Conf Piezo Mems 2011

2ndInterna*onalWorkshopon

PiezoelectricMEMSMaterials‐Processes‐Tools‐Devices

September6‐7,2011EPFL‐Lausanne‐Switzerland

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Sponsoredby

2ndInterna*onalWorkshoponPiezoelectricMEMSMaterials‐Processes‐Tools‐Devices

WeobserveanincreasingworldwideinterestinpiezoelectricthinfilmMEMSdevices.S;llgreateffortsareneededtoestablishreproducibleprocessing routes, reliable integra;on, op;mal poling procedures,standards in characteriza;on methods, op;mal device design, andreproducible opera;on condi;ons. A@er the success of the firstworkshop in 2010 at Aachen, we aim at bringing together againresearchersandengineersfromindustryandacademiatoreportanddiscuss on progress in in the field, and s;mulate exchange onexperienceandpossiblecoopera;on.Acombina;onofpresenta;onsanddiscussionswillgiveexpertsandresearchersthechancetoboostthispromisingandquicklydevelopingmarket.

Theprogramincludesmanyinteres;ngandexci;ngtalksonsynthesisof piezoelectric thin films, on integra;on, on tes;ng andinstrumenta;on, and on some of the many applica;ons that areforeseeableforpiezoelectricMEMS.

Wehopethisworkshopisagreatopportunityforcompaniesworkinginthinfilmprocessing,microfabrica;onandMEMStolearnaboutthestateoftheartinpiezoelectricMEMSbasedonferroelectricandnon‐ferroelectricpiezoelectricthinfilms.

OnbehalfoftheorganizingcommiLeePaulMuralt

Chair

(i)

Chair:P.Muralt SwissFederalIns;tuteofTechnology

EPFL(Switzerland)

Interna;onaladvisoryboardandprogramcommiLee:T.Matsushima Panasonic(Japan)T.Metzger EPCOS(Germany)R.Polcawich USArmyLabs(USA)H.Raeder SINTEF (Norway)S.Tiedke Aixacct (Germany)S.Trolier‐McKinstry PennstateUniversity(USA)K.Udayakumar TexasInstruments(USA)

OrganizingcommiLee:P.MuraltP.Ulrich(Sciprom)S.Tiedke(Aixacct)

Localarrangements:L.JinN.ChidambaranA.MazzalaiR.Matloub

WorkshopOrganizers:

(ii)

InvitedSpeakers

Exhibitors

aixACCTSystemsGmbHSolMateSYOUTEC/DJKEurope

SrowthiBharadwaja, PennStateUniversity

RolandKessels, AIXACCT

TakakiyoHarigai, PanasonicGillesMoulard, TDK‐ECOS

TuomasPensala, VTT

GianluccaPiazza, UniversityofPennsylvania

RonPolcawich, USArmyLaboratories

GuusRijnders, UniversityTwente

FrodeTyholdt, SINTEF

(iii)

September 6-7, 2011

2nd International Workshop on Piezoelectric MEMS Materials - Processes - Tools - Devices

Program

Tuesday Morning 6 September

Time Speaker Title

0800-0900 Registration

0900 P. Muralt, EPFL

Welcome

Chair: S. Trolier-McKinstry

0930 T. Harigai, Panasonic Corporation

Piezoelectric Thin Films and Their Applications inv

1005 M. Klee, Philips Research

Piezoelectric thin films: A Technology platform for thin film ultrasound transducer arrays

1025 BREAK with exhibition and posters

1045 Polcawich, US Army Research Lab.

PiezoMEMS Technology for Enabling mm-Scale Robotics inv

1120 M. Schreiter, Siemens AG, Corp.Techn.

Piezoelectric MEMS based energy harvesting module for wireless tire pressure monitoring

1140 R. Vullers, IMEC Holst Center

AlN and PZT Thin Films: Essential Ingredients for Piezoelectric Energy Harvesters

1200 P. Janphuang, IMT-EPFL

MEMS Based Piezoelectric Harvesters: From Thick Sheet to Thin Film Epitaxial Piezoelectric Materials

1215 D. Remiens, IEMN-CNRS

Performance of piezoelectric nanostructures

1230-1400 LUNCH with exhibition and posters

Tuesday Afternoon 6 September

Time Speaker Title

Chair: T. Metzger

1400 G. Piazza, Univ. of Pennsylvania

Laterally Vibrating Micro and Nanomechanical Piezoelectric Aluminum resonators for RF Communication and Chemical Sensing

inv

1435 V. Felmetsger OEM Group, Inc.

Sputter Deposition of Piezoelectric AlN Thin Films on Vertical Walls of Micromechanical Devices

1450 G. Moulard, TDK-EPC

Piezo-MEMS for RF applications inv

1520-1545 BREAK with exhibition and posters

1545 T. Pensala, VTT

Piezo-actuated AlN-Si MEMS resonators and sensors inv

1615 R. Matloub LC-EPFL

Sc doped AlN thin films and their properties

1630 T. Baron FEMTO-CNRS

FBAR filters for space application based on LiNbO3 membrane

1645 Piorra, A. University of Kiel

Lead Free Laser Deposited Thin Films Of 0.5(Ba0.7Ca0.3TiO3)–0.5(Ba(Zr0.2Ti0.8)O3)

1700 S. Trolier-McKinstry PennState University

Microcontact Printing of PZT Films for MEMS

1720 Adjourn

1900 DINNER at Beau Rivage (Ouchy)

POSTERS 6 & 7 September

Author Title

P1 T. Baron FEMTO-CNRS HBAR and their applications

P2 N. Chidambaram EPFL-IMX

PZT thin film growth on insulators for interdigitated electrode applications

P3 V. Felmetsger, OEM group Reactive Magnetron Sputtering of Ultrathin Piezoelectric

P4 S.Y. Kang Samsung Elec.-Mech.

Influence of Temperature and O2 Flow Rate on the Structure and Ferroelectric Properties of PZT Films Deposited by RF Magnetron Sputtering

P5 A. Mathewson Tyndall National Institute

Influences of Titanium Underlayer on (002) Oriented Aluminium Nitride

P6 A. Mazzalai EPFL-IMX

Conception of interdigitated electrodes based cantilever for piezoelectric energy harvesting

P7 E. Milyutin EPFL-IMX

Local polarity control of AlN thin films

P8 M. Pham-Thi Thales Research

Hyper Frequency properties of “3 inches-frozen capacitive MEMS” with PZT thin films processed by sol-gel

P9 T. Verdot FEMTO Active damping with a piezoelectric MEMS device

P10 A. Vogl SINTEF

Modelling of piezoelectric micromachined ultrasound transducers (pMUT) for medical use.

Wednesday Morning 7th September

Time Speaker Title

Chair: T. Matsushima

0840 G. Rijnders, University of Twente

All Oxide PiezoMEMS devices by Pulsed laser Deposition: Properties of Clamped Piezoelectric Epitaxial PZT Thin Films

inv

0910 A. Janssens, SoLMateS

Introduction of new manufacturing technology for Piezo (PZT) MEMS production

0930 S. Gariglio University of Geneva

Epitaxial Ferroelectric Pb(Zr0.2Ti0.8)O3 Thin Films on Silicon:Growth and Physical Properties

0945 M. Kratzer, Oerlikon Balzers

Oerlikon PVD production solution for in-situ large scale deposition of PZT films

1000-1020 BREAK with exhibition and posters

1020 R. Kessels, AIXACCT

Qualification and Quantification of piezoelectric MEMS inv

1050 Le Rhun, G. CEA-LETI

Direct And Indirect Piezoelectric Characterization of PZT Thin Films for MEMS Applications

1105 T. Kijima, YOUTEC

Spin-Coat Technology of KNN Film Deposition with Oxygen Pressurizing RTA

1120 K.-A. Bui-Thi Thales Research

Properties of PMN-PT 65/35 thin film oriented -<011> at radio frequency measured by coplanar waveguide

1135 B. Malic Josef Stefan Inst.

Influence of Solution Synthesis Conditions on Crystallization and Properties of Functional Oxide Thin Films

1150 S. S. N. Bharadwaja, Pennstate University

Low Temperature Laser Processing of Ferroelectric Thin Films

inv

1220-1400 LUNCH with exhibition and posters

Wednesday Afternoon 7th September

Time Speaker Title

Chair: S. Tiedke

1400 F. Tyholdt, SINTEF

FP7 piezoVolume - High Volume Piezoelectric Thin Film Production Process For Microsystems

inv

1430 J. Phair Polight

Manufacture of Minature Tuneable Autofocus Lenses (TLens) using Piezo MEMS

1445 S. Han Samsung Electr.Mech.

Wafer Level Poling of PZT thin films for MEMS Sensor Devices

1500 V. Cauda Italian Inst.Techn.

Effects of Nanoscale Confiment on Ferroelectric Properties: Research Activity at the Center for Space Human Robotics

1515 E. Mounier, Yole Development

2010-2015 Market Analysis of PiezoMEMS

1530 BREAK with exhibition and posters

1600 S. Trolier-McKinstry PennState University

Round table discussion:

1650 P. Muralt Closing remarks

1700 END

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Equipment for PZT thin filmproductionHighqualityPZTthinfilmsSolMateS offers a reliable PVD process todeposit (001)‐ textured PbZrTiOx on Si, SiN3,SOIorGOSwafers.Thicknessuniformityof thethinfilms(0.1to5µm)is<2.5%.Theproductionof high quality PZT is performed in a singleprocessstep,noRTAorpolingisrequired.

Typicaldisplacementdata(1µmPZT)

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“Our customer’s R&D director looked at me and said, ‘Rogier, packaging costsare just too high. We needMUCH BETTER productivity.’”

“That’s howHexagon was born.”

Part I

T 6, SO

2nd International Workshop on Piezoelectric MEMS 2011 3

Piezoelectric Thin Films and Their ApplicationsTakakiyo Harigai1, Kazuki Komaki2, Osamu Watanabe3, Satoru Fujii1, Yoshiaki Tanaka1, Michihito

Ueda1, Hideaki Adachi1 and Eiji Fujii1

1Panasonic Corporation, Japan2Panasonic Elecronic Devices Co., LTD, Japan3Panasonic System Networks Co., LTD, Japan

Piezoelectric materials have been used for many kinds of devices such as actuators for inkjet printerheads and sensors for angular velocity detection. Piezoelectric thin films formed on a Si substrate canbe processed into arbitrary configurations by standard micro-electro-mechanical systems (MEMS) pro-cesses. Performance enhancement and miniaturization are easier for a device with piezoelectric MEMSthan for a normal Si-MEMS device. The importance of the piezoelectric thin films is set to increase inthe future.

We developed a technique to form piezoelectric materials with perovskite structure on various sub-strates (MgO, Si, SUS). We grew Pb(Zr,Ti)O3 (PZT), Pb(Mg,Nb)O3-Pb(Zr,Ti)O3 (PMN-PZT), and lead-free (Na,Bi)TiO3-BaTiO3 (NBT-BT) thin films with the thickness of 3.0 µm by RF magnetron sputtering.The growth of these thin films on MgO substrates was epitaxial, and the films on the Si or SUS wereoriented in (001) single direction. The piezoelectric coefficients d31 of these films were -150 pm/V forPZT/Si, −225 pm/V for PMN-PZT/Si, and −155 pm/V for NBT-BT(100)/MgO.

The PZT films were applied to the sensor for angular velocity detection and the actuator of the inkjet printer head. In the angular velocity sensor, PZT/Si was processed into a tuning fork configuration bySi deep etching. This configuration by itself can vibrate the tuning fork and detect the angular velocityat the same time. Thus, we succeeded in downsizing to 1/100 in volume compared with the conventionalproduct in which bulk PZT or quartz were arranged for three dimensions. This PZT/Si sensor is nowwidely used for a position sensing in a car navigation system, and for shake compensation of a digitalcamera. The ink jet head for industrial on-demand printers was also miniaturized by MEMS processing,and realized printing resolution of 1, 200 dpi, and printing speed of 120 m/min.

The material properties of NBT-BT/MgO films with (001), (110), and (111) orientation were eval-uated. From X-ray diffraction analyses, (001)-films had a tetragonal structure, and (111)-films had arhombohedral structure with no dependence on BT content. The maximum piezoelectric coefficients of(001)- and (111)-films were obtained around morphotropic phase boundary (MPB) compositon of thebulk. On the other hand, (110)-films were distorted to orthorhombic structure which does not form inbulk state. The piezoelectric coefficient d31 of 〈110〉 directions was only −9 pm/V whereas d31 of 〈001〉directions was as high as −221 pm/V, comparable to PMN-PZT/Si. This work is promising to open animportant avenue for the improvement of piezoelectricity larger than that of the original material, and toactual electromechanical devices using lead-free piezoelectric films.

4 2nd International Workshop on Piezoelectric MEMS 2011

Piezoelectric Thin Films: A Technology Platform for Thin FilmUltrasound Transducer Arrays

M. Klee1, R. Mauczok1, C. van Heesch1, H. Boots1, W. Keur1, M. de Wild1 and B. Op het Veld1

1Philips Research, Eindhoven

Piezoelectric thin film technologies get more and more relevance for miniaturized and integratedactuators and transducers. Applications of miniaturized piezoelectric thin film devices are for examplesensors for proximity sensing or ultrasound transducer arrays for imaging.

A piezoelectric thin film technology platform has been developed, which processes lead based per-ovskite piezoelectric thin films by spin-on processing on thin film membranes. Making use of litho-graphic patterning, piezoelectric thin film ultrasound transducers have been realized, which are operatingin the d33 mode.

With the piezoelectric thin film platform, piezoelectric thin film ultrasound transducer arrays havebeen realized, which dependent on the design are operating at frequencies of 50 KHz up to >10 MHz.The piezoelectric thin film ultrasound transducer arrays are tested with respect to their performance.The piezoelectric thin film membrane transducer arrays operating at 4 MHz and above show a very goodacoustic matching to water. This results in a bandwidth of the transducer arrays, which is equal or evenlarger than 100%. The output pressure of the thin film piezoelectric ultrasound transducer arrays is lineardependent from the applied voltage. These piezoelectric thin film ultrasound transducer arrays, due totheir similar operation conditions as traditional ceramic or single crystal ultrasound transducer, can beoperated with standard ultrasound machines. With the piezoelectric thin film ultrasound transducerarrays with 32−42 elements ultrasound images of e.g. nylon wires with 0.12 mm diameter in a watertank have been demonstrated.

The technology platform has also developed to realise ultrasound transducers operating at 50−100 KHz,which have been successfully applied for proximity sensing.


PiezoMEMS Technology for Enabling mm-Scale RoboticsR.G. Polcawich1, J.S. Pulskamp1, G. Smith1, S. Bedair1, T. Ivanov1, R. Proie1, R. Kaul1, L. Sanchez1

and D. M. Potrepka1

1US Army Research Laboratory, Adelphi, MD, USA

Piezoelectric MEMS (PiezoMEMS) technology can enable integrated solutions for a wide varietyof applications including radio and cellular communications systems, biomedical, consumer electron-ics, and mm-scale robotics. Several piezoelectric materials are of interest for this technology. AlNthin films lead the way in the front-end filtering technology with film bulk acoustic resonators (FBAR)currently seeing heavy demand in cellular phones. Another material of keen interest is lead zirconatetitanate (PZT) especially for applications requiring low voltage, high stroke, high force actuators. Aspart of an on-going research activity at the Army Research Laboratory, PiezoMEMS technology usingPZT thin films has been developed in the area of RF applications and mm-scale robotics. Specifically,switches and relays covering a frequency space from DC to the high GHz have been demonstrated formechanical logic for low power embedded microcontrollers and high frequency phase shifters to en-able electronically steerable antennas. PiezoMEMS actuators have also enabled two degree-of-freedomactuators capable of matching the kinematic performance of insects at the mm-scale. These actuatorscombined/integrated with low power sensors are being developed to enable mm-scale insect-inspiredrobotic platforms. This presentation will focus specifically on the technologies of interest for mm-scalerobotics including advancements in actuator design, integrated sensing, integration of a mechanical logicbased microcontroller and performance will be presented with respect to bio-inspired microflight.


Piezoelectric MEMS Based Energy Harvesting Module for Wireless TirePressure Monitoring

Matthias Schreiter1, Dana Pitzer1, Michael Schier1, Andreas Wolff1, Ingo Kuhne1, Julian Seidel1,Helmut Seidel2 and Alexander Frey1

1Siemens AG, Corporate Technology, Munich, Germany2Saarland University, Chair of Micromechanics, Microfluidics/Microactuators, Saarbruecken,

Germany

Recently, MEMS-based energy harvesting systems have gained increasing importance to powerwireless sensor networks. While conventional batteries represent a simple and in many cases sufficientpower supply, dedicated energy harvesting solutions enable the implementation of sensor applicationswhere the operation conditions such as inaccessibility of the sensor in conjunction with long lifetimerequirements ban the usage of batteries.

This presentation gives an overview about the development of a demonstrator for a piezoelectricMEMS based power generator for tire pressure sensors. Conventional battery driven systems are usuallymounted in the wheel rim. However, an arrangement on the inner liner of the tire would enable thedetection of additional parameters such as tire temperature, friction, wearout and side slip. This approachimplies stringent system requirements favouring an energy harvesting approach against a battery. This isin particular a total system weight less than 7 grams and a minimum life time of 8 years. The harvestingmodule needs to provide a minimum average power of 3 µW to power pressure sensor, microcontroller,and RF-frontend. The energy harvesting module requires a system approach with adapted componentinterfaces. The generator is based on a piezoelectric MEMS cantilever with a triangular shape whichenables high energy densities. Tire related forces during the tread shuffle passage are proposed to beused for a pulsed excitation. To optimize the generator performance, piezoelectric thin films of differentmaterials (AlN, ZnO, and PZT) were evaluated with respect to relevant material characteristics such aselectro-mechanical coupling, dielectric constant and charge constant.

An analytical approach was implemented modeling the generator system as a whole which enables tocalculate the supplied average power and voltage depending on input parameters, cantilever geometries,material parameters, and the interface circuit. The figure illustrates a thus obtained parameter spacefor the generator design to meet requested output characteristics (generator area and piezoelectric thinfilm parameters are fixed). First demonstrators were tested showing an electrical energy density of35 nJ/mm2.

This work is supported by the “Bundesministerium fur Forschung und Entwicklung”, Germany,and embedded in the project “ASYMOF–Autarke Mikrosysteme mit mechanischen Energiewandlernfur mobile Sicherheitsfunktionen” (reference 16SV3336).


AlN and PZT Thin Films: Essential Ingredients for Piezoelectric EnergyHarvesters

Ruud Vullers1, Madhusudhanan Jambunathan1, Rene Elfrink1, Christine de Nooijer1, Rob Van Schaijk1

1imec/Holst Centre, Eindhoven, The Netherlands

The rapidly growing need for energy autonomy of wireless sensor nodes can only be well served byusing various energy harvesting technologies in combination with energy storage devices. The marketacceptance of such solutions necessitates further cost reduction, which can be achieved by taking advan-tage of MEMS technology. This paper focuses on the principle and thin film technology developmentfor piezoelectric harvesting devices within imec/Holst Centre.

Aluminum nitride (AlN) was chosen as piezoelectric material for its material properties and its well-known sputter process. For power generation AlN is better or at least comparable with other piezoelectricmaterials like, e.g. PZT [1]. A maximum power of 225 µW has been measured at an acceleration of 2.5 gand a resonance frequency of 929 Hz (Fig. 1a). The package of MEMS energy harvesters is essentialboth for reliability, in preventing excessive displacements, as well for preventing air damping by the useof vacuum [2]. Therefore, the released MEMS structures are packaged with a 6-inch wafer level process,using two glass substrates with a cavity depth of 600 µm (Fig. 1b). Devices with different beam and masssize were fabricated to cover a 200-1200 Hz frequency range. The devices in vacuum have a large Q,and therefore a very narrow bandwidth of less then 1%. This will hinder practical applications for singlefrequency input excitation, since it will be very difficult to match the resonance to the ambient frequency.Frequency tuning is therefore essential [3]. This can be accomplished by adding wing like structuresnext to the beam (Fig. 1c). In this case, PZT is the material of choice, for its higher piezoelectric constantcompared to AlN. Modeling indicates that 10 to 20% tuning can be reached with PZT (Fig. 1d). Progressin development of sputtering of PZT thin films and the influence of deposition conditions, anneal andpoling on RF and pulsed DC sputtered layers will be discussed.

2nd International Workshop on Piezoelectric MEMS 2011

AlN and PZT Thin Films: Essential Ingredients for Piezoelectric Energy Harvesters

Ruud Vullers, Madhusudhanan Jambunathan, Rene Elfrink, Christine de Nooijer, Rob Van Schaijk imec/Holst Centre

Eindhoven, The Netherlands

1Affiliation, Country 2Affiliation,Country

The rapidly growing need for energy autonomy of wireless sensor nodes can only be well served by using various energy harvesting technologies in combination with energy storage devices. The market acceptance of such solutions necessitates further cost reduction, which can be achieved by taking advantage of MEMS technology. This paper focuses on the principle and thin film technology development for piezoelectric harvesting devices within imec / Holst Centre. Aluminum nitride (AlN) was chosen as piezoelectric material for its material properties and its well-known sputter process. For power generation AlN is better or at least comparable with other piezoelectric materials like, e.g. PZT [1]. A maximum power of 225 µW has been measured at an acceleration of 2.5 g and a resonance frequency of 929 Hz (Fig 1a). The package of MEMS energy harvesters is essential both for reliability, in preventing excessive displacements, as well for preventing air damping by the use of vacuum [2]. Therefore, the released MEMS structures are packaged with a 6-inch wafer level process, using two glass substrates with a cavity depth of 600 µm (Fig. 1b). Devices with different beam and mass size were fabricated to cover a 200-1200HZ frequency range. The devices in vacuum have a large Q, and therefore a very narrow bandwidth of less then 1%. This will hinder practical applications for single frequency input excitation, since it will be very difficult to match the resonance to the ambient frequency. Frequency tuning is therefore essential [3]. This can be accomplished by adding wing like structures next to the beam (Figure 1c). In this case, PZT is the material of choice, for its higher piezoelectric constant compared to AlN. Modeling indicates that 10 to 20% tuning can be reached with PZT (Fig 1d). Progress in development of sputtering of PZT thin films and the influence of deposition conditions, anneal and poling on RF and pulsed DC sputtered layers will be discussed. In case of shock induced vibration harvesting, the seismic mass is excited with a mechanical shock after which the mass will “ring-down” at its natural resonance frequency [4]. During the ring-down period, whose duration increases with increasing quality factor, part of the mechanical energy is harvested. The output power has multiple maxima with a bandwidth of about 100% each.Therefore, the main advantage of this principle is that the frequency match condition is not relevant. In case of application inside car tires, repetitive high amplitude shocks occurs every rotation. A high quality factor harvester enables continuous power generation of a few tens of µW, sufficient to power a wireless sensor node.

References [1] R. Elfrink, et al., conf. proc. PowerMEMS 2008, p.249-252 [3] D. Zhu et al., Meas. Sci. Technol. 21 (2010) [2] R. Elfrink, et al, IEEE IEDM2009, pp. 543-546 [4] B. Cavallier, et al, IEEE Ultrason. Symp. 2005, p.943-945

b)

a)

c)

d) Figure 1 : a) Power output for AlN piezoelectric energy harvester b) Wafer level packaged device c) Frequency tuning design for a piezo electric, by adding overhanging PZT 〝wings〝 (grey areas) next to the beam d) the change of the frequency that can be reached Fig. 1: a) Power output for AlN piezoelectric energy harvester b) Wafer level packaged device c) Frequency tuning

design for a piezo electric, by adding overhanging PZT “wings” (grey areas) next to the beam d) the change of thefrequency that can be reached

In case of shock induced vibration harvesting, the seismic mass is excited with a mechanical shockafter which the mass will “ring-down” at its natural resonance frequency [4]. During the ring-down pe-riod, whose duration increases with increasing quality factor, part of the mechanical energy is harvested.The output power has multiple maxima with a bandwidth of about 100% each.Therefore, the main ad-vantage of this principle is that the frequency match condition is not relevant. In case of applicationinside car tires, repetitive high amplitude shocks occurs every rotation. A high quality factor harvesterenables continuous power generation of a few tens of µW, sufficient to power a wireless sensor node.

[1] R. Elfrink, et al., conf. proc. Power MEMS 2008, pp. 249-252. [2] R. Elfrink, et al., IEEE IEDM2009, pp.543-546. [3] D. Zhu et al., Meas. Sci. Technol. 21 (2010). [4] B. Cavallier, et al., IEEE Ultrason. Symp. 2005,pp. 943-945.


MEMS Based Piezoelectric Harvesters: From Thick Sheet to Thin FilmEpitaxial Piezoelectric Materials

P. Janphuang1, D. Isarakorn1, D. Briand1, S.Gariglio2, A. Sambri2, J.-M. Triscone2, F. Guy3, J.W.Reiner4, C.H. Ahn4 and N.F. de Rooij1

1Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland2University of Geneva, Switzerland

3Engineering school of Geneva, Switzerland4Yale University, USA

This work demonstrates MEMS based vibration piezoelectric energy harvesters. The characteristicsand performances of two different energy harvesting devices based on thick PZT sheet and epitaxialPZT thin film have been investigated. The harvester made by bonding a thick PZT sheet produced apower density of 2.41 µW/mm3/g2. While with the device based on an epitaxial PZT thin film reached apower density of 85 µW/mm3/g2. To compare our device performances, the Figure of Merit defined byMitcheson [1] is taken into account (Table 1).


References [1] P. D. Mitcheson, et al., Proceedings of the IEEE, vol. 96, pp. 1457-1486, 2008. [2] E. E. Aktakka et al., IEE IEDM 2007, San Francisco, pp. 31.5.1-31.5.4. [3] G. A. Ardila Rogríguez et al., Proc.PowerMEMS 2009, Washington DC, pp. 197-200. [4] S. Roundy and P.K. Wright, Smart Mater. Struct. 13 (2004) pp. 1131-1142. [5] S. Trolier-Mckinstry and P. Muralt, J. Electroceramics. 12 (2004), pp. 7-17. [6] D. Shen et al., J. Micromech. Microeng., 18 (2008) 055017.

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12

16




Pow

er (μ

W g

-2)

Figure 3. The output power across 218 kΩ as a function of frequency at input acceleration of 1.0g

Figure 5. Theoretical and experiment power, current, and voltage as a function of resistive load for the epitaxial PZT harvester.

Figure 2. The output power (Prms) and output voltage (Vrms) as a function of resistive load at input vibration of 0.1g and 145 Hz.

Figure 4. Optical image of an epitaxial PZT harvester (active volume of 0.153 mm3). The inset shows the Si mass on the backside of the cantilever.

Figure 1. Optical image of a thick PZT harvester (active volume of 90 mm3) mounted on the shaker. The accelerometer is used to determine the acceleration level.

Table 1. Performances of our devices based volume figure of merit (FoMv) proposed by Mitcheson et al. [1].

9.2892.78

0.1313

23022302

0.98 (0.1g)9.80 (1g)

0.153Epitaxial PZT -0.5 µm

0.503.73

2.17157.74

145141

0.98 (0.1g)9.80 (1g)

90Thick PZT sheet -130 µm

FoMv(%)

Power (µm)

fr(Hz)

Input acc. (m/s2)

Vol.(mm3)

Piezoelectric type

9.2892.78

0.1313

23022302

0.98 (0.1g)9.80 (1g)

0.153Epitaxial PZT -0.5 µm

0.503.73

2.17157.74

145141

0.98 (0.1g)9.80 (1g)

90Thick PZT sheet -130 µm

FoMv(%)

Power (µm)

fr(Hz)

Input acc. (m/s2)

Vol.(mm3)

Piezoelectric type


Bulk PZT ceramics present high electromechanical coupling which is highly desirable in piezoelec-tric energy harvester. Several piezoelectric cantilevers based energy harvester with bulk PZT have beenproposed and investigated in recent years [2,3]. In our work, the thick PZT sheet was bonded onto sil-icon cantilever using a spin coated UV activated epoxy. The harvester structure was designed to haveresonant frequency lower than 200 Hz in order to be matched by the ambient vibrations in environ-ment [4]. Fabricated thick PZT harvester (Fig.1) produced an average output power of 2.17 µW at 0.1 g(145 Hz) (Fig. 2) and reached to 157.74 µW at 1.0 g (141 Hz) with an optimal resistive load of 218 kΩ

(Fig. 3). In order to achieve low resonant frequency structure, a high mass with a high volume is re-quired in thick PZT harvester, resulting in low power density (2.41 µW/mm3/g2). Moreover, wafer levelmanufacturability is limited with the transfer of the PZT sheet and the mass onto the silicon structure.Therefore, piezoelectric thin films are promising [5,6] to develop a low volume harvesters using waferlevel manufacturing processes.

In this matter, we are developing MEMS scavengers using an epitaxial Pb(Zr0.2Ti0.8)O3 thin filmsgrown on silicon through oxide layers. The PZT with a composition of Zr/Ti=20/80 is chosen for itsgood lattice match with oxide layers and for the highest power generation figure of merit due to a highpiezoelectric coefficient and a low dielectric constant. The power generated from the epitaxial PZTharvester (Fig. 4) measured at its resonant frequency (2.3 kHz) are 13 µW/g2, 60 µA/g and 0.28 V/g foran optimal resistive load of 4.7 kΩ (Fig. 5). The epitaxial PZT harvester can gererate high power andcurrent while maintaining low resistive load, which is favorable for impedance matching with electronicdevices.The eptixial PZT harvester still needs to be optimized by changing on the device geometry toincrease its ouput voltage to match with most of rectifying devices. An improved design included lowerresonant frequency, higher output voltage and power will be presented.

[1] P. D. Mitcheson, et al., Proceedings of the IEEE, vol. 96, pp. 1457-1486, 2008.[2] E. E. Aktakka et al., IEE IEDM 2007, San Francisco, pp. 31.5.1-31.5.4.[3] G. A. Ardila Rogrıguez et al., Proc. Power MEMS 2009, Washington DC, pp. 197-200.[4] S. Roundy and P.K. Wright, Smart Mater. Struct., 13 (2004) pp. 1131-1142.[5] S. Trolier-Mckinstry and P. Muralt, J. Electroceramics. 12 (2004), pp. 7-17.[6] D. Shen et al., J. Micromech. Microeng., 18 (2008) 055017.


Performances of Piezoelectric Nano StructuresD. Remiens1, J. Costecalde1, D. Deresmes1, D. Troadec1 and C. Soyer1

1IEMN-UVHC-DOAE-UMR 8520, Universite des Sciences et Technologies de Lille, Bat. P3, BP60069, 59652 Villeneuve d’Ascq Cedex, France

Piezoelectric nano-structures (islands of dimensions in the lateral size range 50–500 nm) have beenfabricated by Focused Ga3+ Ion Beam (FIB) etching on PbZr0.54Ti0.46O3 thin films obtained by mag-netron sputtering. The degradation induced by the etching process is investigated through the evolutionof electromechanical activity measured by means of local piezoelectric hysteresis loops produced byPiezo-response Force Microscopy. The analysis of surface potential is performed by Kelvin Force Mi-croscopy and the measurement of current-voltage curves is carried out by Conducting Atomic ForceMicroscopy. Two kinds of structures, namely one based on crystallized films and the other based onamorphous ones, were studied. In this latter case, the amorphous films are post-annealed after etchingto obtain crystallized structure. For the structures based on the crystallized and then etched films, nopiezoelectric signal was registered that evidences a serious degradation of material induced by Ga3+

ion implantation. For the structures based on the films etched in amorphous state and then crystallizedthe piezo response signal was near to that of the reference films (crystallized and not etched) whateverwere the ion dose and the island dimensions. Even for very small lateral size (50 nm), no size effect wasobserved. All these results will be presented at the workshop.


Laterally Vibrating Micro and Nanomechanical Piezoelectric AluminumNitride Resonators for RF Communications and Chemical Sensing

Gianluca Piazza1

1University of Pennsylvania, Philadelphia, PA, USA

Miniaturized resonators capable of operating at various frequencies on the same substrate havegained interest as emerging technologies for addressing the specific needs of next generation radiofrequency (RF) communication and sensing systems. Large scale integration of micro and nanoscaleresonant mechanical devices will yield unprecedented platforms capable of low power and dynamic re-configuration of radio links as well as the development of portable and disposable OnosesO characterizedby very low limit of detection and high sensitivity to complex volatile organic chemical mixtures.

This talk presents the latest advancements undergoing at the University of Pennsylvania in the de-velopment of a very promising class of these micro and nanomechanical resonators, namely laterallyvibrating (contour-mode) piezoelectric aluminum nitride resonators. These devices have shown the abil-ity to operate from few MHz up to several GHz with low motional impedances that can be readilyinterfaced with electronics and mechanical quality factors in excess of 1,000 and up to 4,000 in ambientconditions. Switchable banks of resonators and filters for frequency synthesis and low energy signalprocessing have been experimentally demonstrated. The impact of these multi-frequency low phasenoise oscillators and low loss filters goes well beyond providing a miniaturized replacement for existingcomponents; massive parallelism of these devices will infact enable new archicetures such as congnitiveradios.

Extreme miniaturization of the thickness of these AlN devices (50-250 nm) has benefited the demon-stration of highly sensitivity and low limit of detection resonant chemical sensors. The reduced massand large surface area in conjuction with high Q at 100 s of MHz make these AlN nanoplates the idealcandidates for the synthesis of very low power and portable sensors. These resonators have been arrayedand functionalied with single-stranded DNA to yield an electronically controlled nose capable of iden-tifiying sub-part per billion (ppb) concentrations of Dinitrotoluene (DNT) and 100 s of ppb of DimethylMethylphosphonate (DMMP).

In summary, this talk will offer an overview of the potentials of this miniaturized AlN resonatortechnology and highlight how it will likely impact the More than Moore evolution of the semiconductorindustry.


Sputter Deposition of Piezoelectric AlN Thin Films on Vertical Walls ofMicromechanical Devices

Valeriy Felmetsger1, Roozbeh Tabrizian2 and Farrokh Ayazi2

1OEM Group Incorporated, USA2Georgia Institute of Technology, USA

We present a novel AlN thin film processing technique that benefits from the efficient longitudinalpiezoelectric effect as well as large transduction area provided by the sidewalls of silicon microstructures[1]. Compared to FBARs where resonance frequency of the device is mainly a function of the piezo-electric film and substrate thicknesses, the resonance frequency of AlN-on-sidewall resonators is mainlydefined by the lateral dimentions of a relatively thick Si microstructure. This implies that devices withresonance frequencies spreading across a wide frequency spectrum can be implemented on the samesubstrate using lithography.

In this study, the Mo/AlN/Mo film stacks were deposited by dual-target S-gun magnetrons onto ex-perimental resonator structures with a sidewall height of 20 µm patterned in Si device layer of 100-mmdiameter SOI wafers. Pre-deposition rf plasma etch of the substrate and thin AlN seed layer were em-ployed to stimulate growth of smooth and well-textured Mo bottom electrode deposited by a dc poweredS-gun with rf substrate biasing. An alternating current (40 kHz) S-gun magnetron for reactive sputteringenabled AlN growth in long-throw, low-pressure conditions with energetic particle bombardment thusensuring effective wall coverage and formation of strong texture in the film.


Sputter Deposition of Piezoelectric AlN Thin Films on Vertical Walls of Micromechanical Devices

Valeriy Felmetsger1, Roozbeh Tabrizian2 and Farrokh Ayazi2

1OEM Group Incorporated, USA

2Georgia Institute of Technology, USA

We present a novel AlN thin film processing technique that benefits from the efficient longitudinal piezoelectric effect as well as large transduction area provided by the sidewalls of silicon microstructures [1]. Compared to FBARs where resonance frequency of the device is mainly a function of the piezoelectric film and substrate thicknesses, the resonance frequency of AlN-on-sidewall resonators is mainly defined by the lateral dimentions of a relatively thick Si microstructure. This implies that devices with resonance frequencies spreading across a wide frequency spectrum can be implemented on the same substrate using lithography. In this study, the Mo/AlN/Mo film stacks were deposited by dual-target S-gun magnetrons onto experimental resonator structures with a sidewall height of 20 µm patterned in Si device layer of 100-mm diameter SOI wafers. Pre-deposition rf plasma etch of the substrate and thin AlN seed layer were employed to stimulate growth of smooth and well-textured Mo bottom electrode deposited by a dc powered S-gun with rf substrate biasing. An alternating current (40 kHz) S-gun magnetron for reactive sputtering enabled AlN growth in long-throw, low-pressure conditions with energetic particle bombardment thus ensuring effective wall coverage and formation of strong texture in the film.

The films were characterized by x-ray diffraction and scanning electron microscopy. 700-nm-thick AlN films on the top surface of the resonator exhibited single (0002) crystal orientation with rocking curve full-width at half-maximum of 1.65˚. Sidewall AlN and Mo film thicknesses were approximately half of top thicknesses and were continuous on the entire surface of the sidewalls. The efficiency of the sidewall process for transduction of MEMS devices was investigated using one-port width-extensional-mode silicon bulk acoustic resonators.

[1] R. Tabrizian and F. Ayazi, The Proceedings of the 16th International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers 2011), Beijing, China, June 2011, pp. 1520-1523.

The films were characterized by x-ray diffraction and scanning electron microscopy. 700-nm-thickAlN films on the top surface of the resonator exhibited single (0002) crystal orientation with rockingcurve full-width at half-maximum of 1.65. Sidewall AlN and Mo film thicknesses were approximatelyhalf of top thicknesses and were continuous on the entire surface of the sidewalls.

The efficiency of the sidewall process for transduction of MEMS devices was investigated usingone-port width-extensional-mode silicon bulk acoustic resonators.

[1] R. Tabrizian and F. Ayazi, The Proceedings of the 16th International Conference on Solid-State Sensors,Actuators and Microsystems (Transducers 2011), Beijing, China, June 2011, pp. 1520-1523.


New Trends in Piezoelectric Devices for RF Application in Mobile PhonesMoulard Gilles1and Metzger Thomas1

1TDK EPC, Munich, Germany

The market requirements in the field of Mobile Phones induce a continuous improvement of piezomaterial for Radio-Frequency acoustic waves devices. Currently, only RF SAW (Surface Acoustic Wave)/ BAW (Bulk Acoustic Waves) duplexers fulfill all of the stringent customers requirements such as smalldevices RF filters with large bandwidths, low insertion losses, low temperature frequency drift and lowprice.

This presentation shows how the development of new SAW/BAW manufacturing process blocksare consistent with the current and future market requirements. High quality piezoelectric material isessential in BAW technology to achieve filter performances and especially a large bandwith in the GHzrange. But the piezoelectric and acoustic properties of the piezo layer are also largly influenced by thechoice of the electrode material. Each change in the layer stack configuration leads also to processintegration issues that have to be solved before being implemented in production.

New process blocks have been developed for SAW technology, mainly to improve the power dura-bility and to reduce the TCF of the devices in order to fullfil the market requirements.

Today, due to the various different processes which have been developed, we are able to answerthe customer requirements for each duplexer bands. The mix process allows us to propose a hybridBAW/SAW duplexer which is already in mass production.


Piezoactuated AlN-Si MEMS Resonators and SensorsTuomas Pensala1

1VTT, Finland

MEMS resonators have been studied for a long time as a potential replacement for quartz crystals inoscillators and timing circuits. High performance resonators have been demonstrated over the years andfinally also entered the market recently, most of the work being based on electrostatic actuation.

The drawbacks of the electrostatic actuation include the need for a large DC bias voltage and/orvery narrow gaps in the actuator structures, combined with small actuation force. Thin film piezoelec-tric structures have been employed by several groups to overcome the drawbacks of the electrostaticactuation, with the cost of e.g. increase in the MEMS fabrication process complexity.

Piezoactuation is compared to electrostatic actuation from the point of view of device physics, fab-rication processes, device performance, yield and repeatability etc. Obtained advantages and issuesarising from the utilization of piezoelectric actuation in resonators are discussed.

Piezoactuated wafer level packaged MEMS resonators for the >10 MHz range fabricated at VTTare presented and a review of the state of the art is performed.

The focus of the paper is on AlN-Si based resonator devices, but a comparison is made to otherpossible piezomaterials and applications of piezo-MEMS.


Electromechanical Properties of Al0.9Sc0.1N Thin Films Evaluated at2.2 GHz: Film bulk acoustic resonators

Ramin Matloub1, Alvaro Artieda1, Cosmin Sandu1, Evgeny Milyutin1, and Paul Muralt1

1Ceramics Laboratory, Ecole Polytechnique Federale de Lausanne EPFL, Switzerland

Since a few years, aluminum nitride (AlN) thin films have become a standard material for RF filtersin mobile phones. It is mostly used in duplex filters working around 2 GHz composed of thin filmbulk acoustic wave resonators (TFBAR) connected in ladder type circuits. Pure AlN thin films werefound to have maximal d33,f piezoelectric coefficients of 5.3 pm/V. The coupling coefficients of TFBAR’samounts to maximally k2=6.5 % considering standard materials parameters. Such a value is sufficientfor covering the needs of current filter requirements for mobile phones. However, there are other filterstypes and applications that would require larger coupling factors in order to achieve larger bandwidths.Recently it was shown that Al substitution by Sc allows for an increase of the piezoelectric response.We prepared polycrystalline (001)-textured Al0.88Sc0.12N thin films by reactive, pulsed, direct currentmagnetron sputtering to measure all relevant properties for TFABR resonators. The target was a 200 mmdiameter, 6 mm thick plate of an Al0.9Sc0.1 alloy of 99.9% purity and exact composition Al/Sc of 89.76at. %/10.23 at. %. Selected area electron diffraction calibrated with the XRD (002) peak yielded a and clattice parameters of 3.11 and 5.01 A, respectively. The c/a ratio decreased to 1.575 from 1.601 of pureAlN. The unit cell volume increased by 5%. Energy dispersive analysis of x-ray emission in the TEMrevealed that 12 at. % of Al atoms were substituted by Sc, indicating a higher sputter or transfer yield forSc. The microstructure of the films as investigated by means of TEM is very close to the known pictureof fiber-type T-zone growth of good AlN thin films for TFBAR’s. The clamped piezoelectric coefficientd33,f as measured by double side interferometry increases to 7.7 to 8.0 pm/V. TFBAR resonators withfundamental resonance at 2.2 GHz have been fabricated and characterized. The sound velocity in AlScNwas derived by means of 2d finite element modeling of the layer stack, allowing for discrimination ofloading effects by the electrodes. The value of 10’300 m/s is clearly lower than in pure AlN (11’000 m/s).A parasitic resistance was taken into consideration through application of an equivalent circuit model.As a result of these procedures we obtained k2 to 11 % and Q factor of 270 for the complete resonator,furthermore a dielectric constant of 12, and a dielectric loss tangent of 0.5% (both @2.2 GHz). Thestiffness constants cD

33 and cE33 were derived as 345 and 320 GPa. The resonance frequency temperature

drift of 26.1 ppm/K was found to be about the same as for pure AlN. The evolution of piezoelectricconstant e33, the dielectric constant, and the stiffness constant cE

33 were found to be close to the valuespredicted by ab-inito calculations.


FBAR Filters for Space Application Based on LiNbO3 MembraneT. Baron1, M. Chatras2, S. Ballandras1

1FEMTO-ST UMR 6174 CNRS-UFC-ENSMM-UTBM, ENSMM, 26 Chemin de l’Epitaphe, 25030Besancon Cedex

2Xlim, UMR 6172 CNRS-Universite de Limoges, Limoges, France

Film bulk acoustic resonator (FBAR) usually use for filter application, can be used to addressaerospace filter application which need large band. Then, it needs to use piezoelectric material withhigh electromechanical coupling coefficient. So we use LiNbO3 cut YXl/36 which have coupling coef-ficient for longitudinal mode of 37.5%.

Conception of this kind of large band filter is based on ladder architecture with three FBAR res-onators. Firstly, we compute thickness of LiNbO3 with our own software to achieve frequency requiredfor elementary resonator. Secondly, we compute and optimise the ladder filter. The ladder filter shows awidthband of 22% at 300 MHz.

Conception of such devices needs to have membrane of LiNbO3 with bottom and top electrode. Toachieve this structure, we based our process fabrication on gold bonding silicon and LiNbO3 wafer andlapping/polishing step of LiNbO3 wafer, as described previously last year [1,2]. Contrary to previousworks, we add different steps of process before the bonding step to structure the bot-tom electrodeon titanium and membrane. The bonding step is achieve with deep structured silicon wafer, bottomelectrode on LiNbO3 and structured gold in both wafer. We achieve a membrane on LiNbO3 of 11 µmas showed in Fig. 1.

Fig. 1: Resonator with 11 µm thickness of LiNbO3.

Electrical characterization shows filter behaviour of FBAR devices. Packaging of these devices al-lows us to test power, thermal behaviour.

[1] T. Baron et al., “BAW pressure sensor on LiNbO3 membrane lapping” EFTF April 2010, Noordwijk.[2] T. Baron et al., “Temperature compensated Radio-Frequency Harmonic Bulk Acoustic Resonators PressureSensors”, IUS October 2010, San Diego.


Lead Free Laser Deposited Thin Films of0.5(Ba0.7Ca0.3TiO3)-0.5(Ba(Zr0.2Ti0.8)O3)

Andre Piorra1, Viktor Hrkac1, Lorenz Kienle1 and Eckhard Quandt1

1Institute for Material Science, Faculty of Engineering, University Kiel, Germany

The materials of choice for piezoelectric applications and so far best investigated piezoelectric ma-terials are bulk or thin film ceramics based on lead zirconate titanate (PZT). However, there is an in-creasing and strong interest in lead-free ferroelectric materials due to the toxicity of lead. A promis-ing composition with piezoelectric properties comparable to PZT were found in 0.5(Ba0.7Ca0.3TiO3)-0.5(Ba(Zr0.2Ti0.8)O3) (BCZT).

In this work ferroelectric lead-free BCZT thin films of this composition were successfully de-posited by pulsed laser deposition (PLD) on Pt/TiO2/SiO2/Si substrates using a ceramic BCZT targetprepared by conventional solid state reaction. The target material itself showed a piezoelectric coef-ficient d33=600 pm/V. The (111) textured up to 1800 nm thick films exhibited a clamped piezoelectricresponse up to 90 pm/V and a dielectric coefficient of εr= 2000 at room temperature and are among thehighest reported for lead-free piezoelectric thin films. In this presentation, the piezo- and ferroelectricproperties of BCZT thin films will be discussed in the framework of PLD deposition parameters, theinfluence of the used substrates and its resulting microstructure.

Funding via the DFG Collaborative Research Center SFB 855 “Magnetoelectric Composites–FutureBiomagnetic Interfaces” is gratefully acknowledged.


Microcontact Printing of PZT Films for MEMSAaron Welsh1, Michael Hickner1 and Susan Trolier-McKinstry1

1Department of Materials Science and Engineering, The Pennsylvania State University

The ability to pattern piezoelectric thin films without damage is crucial for the development ofmicroelectromechanical systems (MEMS). Many patterning techniques change the crystallinity or sto-ichiometry, which degrades the dielectric and piezoelectric properties of the material, with potentiallong-term consequences in reliability. This research is focused on shifting the paradigm away fromsubtractive patterning techniques by exploring direct patterning of complex oxides through microcon-tact printing. This process utilizes an elastomeric stamp to transfer a chemical solution precursor of apiezoelectric material directly onto a substrate in a desired pattern. Subsequent heat treatment is used tocrystallize the material.

One key factor that governs the quality of the patterned shape is the wetting of the PbZr0.52Ti0.48O3(PZT) solution “inked” onto the surface of the elastomeric stamp. The most commonly used stamp ma-terial for microcontact printing is polydimethylsiloxane (PDMS). This material has excellent mechanicalproperties for this application. However PDMS has a hydrophobic surface, while the 2-methoxyethanol(2-MOE) based PZT solution is a polar solvent. Therefore poor wetting between the solution and thestamp leads to poor pattern transfer. Two routes are being explored to improve this. The first is subject-ing the PDMS stamps to an oxygen plasma ashing treatment which converts the surface of the stamp toa temporary hydrophilic surface. The second is to use a polyurethane (PU) composite stamp that has aninherently hydrophilic surface.

It was found that oxygen plasma ashing the surface of the PDMS stamps leads to well defined patterntransfer of a single 125 nm layer of PZT solution. Similarly, PU stamps enable both excellent patterntransfer and multiple printing cycles without degradation in definition of the features. Lateral featuresizes of the patterned PZT varied from 500 µm to 5 µm. On crystallization, the patterned features formedperovskite PZT without deleterious second phases. The patterned features have comparable electricalproperties to those of continuous PZT films of similar thicknesses, with permittivities of >1000 forthicknesses above 400 nm. The hysteresis loops are well formed, without pinching of the minor loop.The piezoelectric response of the patterned features produced an e31,f of −5 to −7 C/m2. This indicatesthat the microcontact printing process does not adversely affect the PZT crystallization.

Part II

T 6, SP


HBAR and Their ApplicationsT. Baron1, E. Lebrasseur1, G. Martin1, B. Francois1, V. Petrini1, S. Ballandras1

1FEMTO-ST UMR 6174 CNRS-UFC-ENSMM-UTBM, ENSMM, 26 Chemin de l’Epitaphe, 25030Besancon Cedex

High-overtone Bulk Acoustic Resonators (HBAR) have received a strong interest for many years.Various developments have been particularly achieved using Quartz and AlN materials. With the devel-opments of new materials which present higher coupling electromechanical coefficient, new applicationscan be address. The fabrication of the proposed HBAR is based on bonding and lapping of two wafers.Thin piezoelectric film presentes strong coupling coefficient, as described previously [1,2]. This fabrica-tion method allows us to choose material for piezoelectric layer and substrat layer to address differentsapplications.

For exemple, one possibility is to control the Temperature Coefficient of Frequency (TCF) of HBAR.The famous Campbell & Jones method [3] has been used here for predicting the TCF of any modeof a given HBAR and hence to determine configurations of material for which this parameter can bemagnified or minimized. By this way, we can address applications which need intrinsic temperaturecompensation or on the contrary maximum sensibility of temperature.


HBAR and their applications

T. Baron1, E. Lebrasseur1, G. Martin1, B. François1, V. Petrini1, S. Ballandras1

1FEMTO-ST UMR 6174 CNRS-UFC-ENSMM-UTBM

ENSMM, 26 Chemin de l'Epitaphe, 25030 Besançon Cedex

High-overtone Bulk Acoustic Resonators (HBAR) have received a strong interest for many years. Various developments have been particularly achieved using Quartz and AlN materials. With the developments of new materials which present higher coupling electromechanical coefficient, new applications can be address. The fabrication of the proposed HBAR is based on bonding and lapping of two wafers. Thin piezoelectric film presentes strong coupling coefficient, as described previously 1,2. This fabrication method allows us to choose material for piezoelectric layer and substrat layer to address differents applications. For exemple, one possibility is to control the Temperature Coefficient of Frequency (TCF) of HBAR. The famous Campbell&Jones method 3 has been used here for predicting the TCF of any mode of a given HBAR and hence to determine configurations of material for which this parameter can be magnified or minimized. By this way, we can address applications which need intrinsic temperature compensation or on the contrary maximum sensibility of temperature. The possibility to combine various materials and to include manufacturing steps before and after bonding and lapping process, allow us to target various applications such as oscillator 4, pressure sensor 1, temperature sensor, filter, and so on. 1 T. Baron et al., “BAW pressure sensor on LiNbO3 membrane lapping” Proc.of the IEEE EFTF April 2010 2 T. Baron et al., Temperature compensated radio-frequency harmonic bulk acoustic resonators, Proc.of the IEEE IFCS, pp. 652 – 655, 2010

Fig. 1: Experimental measurements of a mode of a HBAR built on (YXl)/163° LiNbO3 on (YXlt)/34°/90° Quartz located in the ISM band

Fig. 1: Experimental measurements of a mode of a HBAR built on (YXl)/163 LiNbO3 on (YXlt)/34/90 Quartzlocated in the ISM band.

The possibility to combine various materials and to include manufacturing steps before and afterbonding and lapping process, allow us to target various applications such as oscillator [4], pressure sen-sor [1], temperature sensor, filter, and so on.

[1] T. Baron et al., “BAW pressure sensor on LiNbO3 membrane lapping”, Proc.of the IEEE EFTF April 2010.[2] T. Baron et al., “Temperature compensated radio-frequency harmonic bulk acoustic resonators”, Proc.of theIEEE IFCS, pp. 652-655, 2010.[3] J.J. Campbell, W.R. Jones, “A method for estimating crystals cuts and propagation direction for excitation ofpiezoelectric surface waves”, IEEE Trans. On Sonics and Ultrasonics, Vol. 15, pp. 209-217, 1968.[4] T. Baron et al., “RF oscillators stabilized by temperature compensated HBARs based on LiNbO3/Quartzcombination”, Proc.of the IEEE IFCS-EFTF, 2011.


Effective Piezoelectric Coefficients of PZT Thin Films for EnergyHarvesting with Interdigitated Electrodes

Nachiappan Chidambaram1, Andrea Mazzalai1, Paul Muralt1


Interdigitated electrode (IDE) systems with lead zirconate titanate (PZT) (figure 1 (a)) thin filmsplay an increasingly important role for two reasons: first, such a configuration generates higher voltagesthan parallel plate capacitor type electrode (PPE) structures, and second, the application of an electricfield leads to a compressive stress component, contrary to PPE structure, which results in tensile stress.Ceramics tend to crack at relatively moderate tensile stresses and this means that with IDEs one candecrease the crack risk. For these reasons, IDEs are ideal for energy harvesting of vibration energy,as well as for actuators. Systematic investigations of PZT films with IDE systems are still missing todate. In this work we present results on the evaluation of the in-plane piezoelectric coefficients withIDE systems. Idealized effective coefficients eIDE and hIDE are derived, showing its composite naturewith about 1/3rd contribution of the transverse effect, and about 2/3rd contribution of the longitudinaleffect in case of a PZT film deposited on a (100)-oriented silicon wafer with the in-plane electric fieldalong one of the ¡011¿ directions. Randomly oriented, 1 µm thick PZT 53/47 film deposited by a sol-gel technique (figure 1 (b)), were evaluated and yielded an effective coefficient, eIDE of 15 C/m2. Wepropose a measurable figure of merit (FOM) for thin film energy harvester structures as the productbetween effective ‘e’ and ‘h’ coefficient representing twice the electrical energy density stored in thepiezoelectric film per unit strain deformation. Assuming homogeneous fields between the fingers, andneglecting the contribution from below the electrode fingers, the FOM for IDE structures is derived tobe twice as large as for PPE structures for PZT-5H properties. The experiments yielded a maximal FOMof the IDE structures of 7.5×109 J/m3.

EffectivepiezoelectriccoefficientsofPZTthinfilmsforenergyharvestingwithinterdigitatedelectrodes

NachiappanChidambaramƗ,AndreaMazzalaiƗ&PaulMuraltƗ

ƗLaboratoiredeCéramiqueEcolePolytechniqueFédéraledeLausanne,EPFL

Lausanne,Switzerland.

August24,2011

Interdigitatedelectrode(IDE)systemswithleadzirconatetitanate(PZT)(figure1(a))thinfilmsplayanincreasinglyimportantrolefortworeasons:first,suchaconfigurationgenerateshighervoltagesthan parallel plate capacitor type electrode (PPE) structures, and second, the application of anelectric field leads to a compressive stress component, contrary to PPE structure,which results intensilestress.CeramicstendtocrackatrelativelymoderatetensilestressesandthismeansthatwithIDEs one can decrease the crack risk. For these reasons, IDEs are ideal for energy harvesting ofvibrationenergy,aswellasforactuators.SystematicinvestigationsofPZTfilmswithIDEsystemsarestillmissingtodate. In thisworkwepresentresultsontheevaluationof the in‐planepiezoelectriccoefficientswith IDE systems. Idealized effective coefficients eIDE and hIDE are derived, showing itscompositenaturewithabout1/3rdcontributionofthetransverseeffect,andabout2/3rdcontributionofthelongitudinaleffectincaseofaPZTfilmdepositedona(100)‐orientedsiliconwaferwiththein‐planeelectricfieldalongoneofthe<011>directions.Randomlyoriented,1µmthickPZT53/47filmdepositedbyasol‐gel technique(figure1 (b)),wereevaluatedandyieldedaneffectivecoefficient,eIDE of 15 C/m

2. We propose a measurable figure of merit (FOM) for thin film energy harvesterstructuresas theproductbetweeneffective ‘e’and ‘h’ coefficient representing twice theelectricalenergydensitystoredinthepiezoelectricfilmperunitstraindeformation.Assuminghomogeneousfields between the fingers, and neglecting the contribution from below the electrode fingers, theFOMforIDEstructuresisderivedtobetwiceaslargeasforPPEstructuresforPZT‐5Hproperties.TheexperimentsyieldedamaximalFOMoftheIDEstructuresof7.5x109J/m3.Figure1:(a)schematicillustrationPZTfilmwithIDE,showingthepolarizationpatternandchargecollectedintheIDE(+q),(b)showstheSEMcrosssectionand(c)showstheopticaltopviewofIDE

pattern

a

cb

Figure 1: (a) schematic illustration PZT film with IDE, showing the polarization pattern and charge collected inthe IDE (+q), (b) shows the SEM cross section and (c) shows the optical top view of IDE pattern.


Reactive Magnetron Sputtering of Ultrathin Piezoelectric AluminumNitride Films

Valeriy Felmetsger1, Pavel Laptev2 and Roger Graham3

1OEM Group Incorporated, USA2Innovative Micro Technology

3NanoTEM Analytics Incorporated, USA

One of today’s challenges is to develop electroacoustic devices operating at higher frequencies. Asthe resonance frequency of the resonator is determined by the thickness of the AlN layer, there is es-sential interest of using ultrathin 100-200 nm films to extend the current FBAR technology from 1-2 to10-20 GHz range. 100-nm and thinner AlN films with precisely controllable in-plain stress as well asstress gradient through the film thickness are required for a new class of vertically deflecting piezoelec-tric nanoelectromechanical (P-NEM) actuators recently implemented for low power logic applications.However, it is challenging to deposit such thin films with acceptable piezoelectric coefficients due totheir drastically downward crystallinity compared to 500-2000 nm thick films currently employed inmass production.

In this study, technological solutions for reactive magnetron sputtering of higly textured nanoscaleAlN films (having thicknesses as low as 200 down to 25 nm) have been proposed, their microstructure,crystal orientation, and features of stress control have been investigated.

To promote the nucleation of small size grains preferably oriented by nitrogen basal plain on top, atwo-step reactive sputtering process by an ac (40 kHz) powered S-gun magnetron was employed. In thefirst stage, a higher substrate temperature (400-450 C) and a higher nitrogen concentration in Ar-N2 gasmixture are used during growth of the first 20 nm thick film. In the second stage, the remaining film isdeposited at an ambient temperature of about 300 C, while the N2 flux is reduced to the value enablingthe magnetron discharge to remain in a poison mode but at the work point located closer to a transitionzone between a poison and a metallic mode on the hysteresis curve. Regulation of the flux of chargedspecies, substrate temperature, and gas content during deposition enabled formation of the films withlow and controllable stress gradient as well as in-plane stress. The two-step AlN processing combinedwith the capability to deposit smooth and highly textured Mo bottom electrodes has demonstrated highefficiency in producing very thin piezoelectric AlN films exhibiting superior crystallinity with FWHMfrom 1.8 (200 nm) to 3.1 (25 nm) on Mo electrodes.

HRTEM results have confirmed that the 25-100 nm thick films have a fine columnar texture and acontinuous lattice microstructure within a single grain from interface with the Mo layer through to theAlN surface. Although the grains were found slightly rotated relative to one another about the c-axis,the (0001)-type planes parallel to the interface with the Mo substrate were observed in all samples,confirming the presence of a strong orientation even in the 25 nm thick film.


Influence of Temperature and O2 Flow Rate on the Structure andFerroelectric Properties of PZT Films Deposited by RF Magnetron

SputteringYun Sung Kang1, Sang Jin Kim1, Seung Hun Han1, Min Kyu Choi1, Sung Min Cho2 and Jung Won

Lee1

1AMD Lab. Samsung Electro-Mechanics,314 Maetan-Dong, Suwon 443-743, Korea2Micro Fab. Samsung Electro-Mechanics,314 Maetan-Dong, Suwon 443-743, Korea

Pb(Zr,Ti)O3 (PZT)films have attracted considerable attention for potential micro-electronics andelectro-mechanical applications due to their excellent ferroelectric and piezoelectric properties. PZTfilms in thickness range of 2-2.5 mm were deposited on Pt/TiOx/SiO2/Si multilayered substrates by radiofrequency magnetron sputtering. The influence of deposition temperature (560-620 C) and O2 flow rate(0.5-2 sccm) on the structural, electrical, ferroelectric and piezoelectric properties of the PZT films wassystematically evaluated. According to this study, the deposition temperature has a strong influence onthe evolution and texture of the ferroelectric perovskite phase and microstructure of the films.


Influences of Titanium Underlayer on (002) Oriented Aluminium NitrideNathan Jackson1, Robert O’Leary1, Rosemary O’Keeffe1, Mary White1, Mike O’Neill2, Finbarr

Waldron1 and Alan Mathewson1

1Tyndall National Institute, University College Cork, Ireland2Analog Devices Inc., Ireland

Recently, aluminium nitride (AlN) has become a highly researched piezoelectric material because ofits unique properties. Piezoelectric AlN films have been used as resonators, actuators, transducers, andenergy harvesting devices. AlN is CMOS compatible, which makes it easier to integrate into an IC chipdesign. Moreover, it is not a ferroelectric material, so poling is not required to obtain a piezoelectriceffect. However, the crystal orientation of the material is critical in order to optimise the piezoelectricproperties. AlN has been deposited using various methods and on numerous materials. AlN depositedon metals such as Pt, Ti, and Mo have shown the highest orientation of (002) c-axis AlN films.

The authors have investigated the influences of using Ti and various deposition parameters on the(002) crystal orientation of AlN. Various DC sputtered Ti and AlN films were investigated using AFM,SEM, and XRD in order to determine the affects of the underlying layers on the (002) orientation ofAlN. Ti was deposited onto Si and Si/SiO2 substrates, followed by a DC sputtered AlN film. Variationsincluded, Ti thickness, AlN thickness, continous deposition of AlN or multiple breaks, and with or with-out a SiO2 isolation layer. Full width half maximum (FWHM) values obtained from the XRD rockingcurve of both the Ti and AlN layers were used to determine the influences of the varying parameters onthe (002) AlN films.

The results show that all of the varied parameters had a significant affect on the RMS surface rough-ness. The thinner films along with multiple depositions of AlN and no oxide gave the lowest surfaceroughness values. SEM cross section images show good columnar c-axis (002) oriention of the AlNfilm. The FWHM results of the (002) AlN film show a strong correlation with quality of the (002) Tioriented film. The highest quality film had a FWHM of 1.5 (AlN) and 1.8 (Ti).

In conclusion, optimising the quality of the underlying layers is critical in order to obtain the highestquality (002) oriented AlN film.


Interdigitated Electrodes Based Cantilevers for Piezoelectric EnergyHarvesting

A. Mazzalai1, N. Chidambaram1, P. Muralt1


We report on conception, simulation, fabrication, and characterization of PZT thin film structuresfor piezoelectric vibration energy harvesting (EH). We investigated specifically interdigitated electrodeconfigurations (IDE), which in theory, allow for a better exploitation of the capabilities of lead zirconatetitanate (PZT) as an active material in terms of output voltage and output power. The overall efficiencyof a MEMS energy harvester is analyzed and also compared to versions with parallel plate structures.

The IDE arrangement decouples the electrode gap from the thin film thickness, allowing to reducethe capacitance of the active layer and therefore to increase the output voltage, which is very importantfor any diode-based rectification and charge pumping circuit. The product of the effective piezoelectriccoefficients eeff and heff constitutes an easy to measure relevant figure of merit for thin film based EHstructures. From the constitutive equations of piezoelectricity we conclude that IDE harvesters can alsocarry about twice the energy density with respect to parallel plate electrodes (PPE) devices with thesame active volume.

The results of finite element modeling (FEM) investigations for both IDE and PPE are presented andcompared with simplified analytical calculations. We studied the harvesting efficiency as a function ofthe power input in the form of elastic beam bending. Due to its higher coupling coefficient, PZT thinfilm based systems with IDE’s can harvest a given amount of stored elastic energy much faster than PZTPPE and AlN PPE structures. Based on these results, an EH design for broadband devices applicationsis proposed and discussed also in its critical aspects of stress compensation and capacitive coupling.

The micro fabrication route of the PZT laminated beams is presented. Deposition of PZT thin filmswas investigated with both magnetron sputtering and chemical solution routes. Silicon cantilevers coatedwith 2 µm thick PZT 53/47 thin films with mainly (100)-orientation were fabricated and characterized.


Local Polarity Control of (001)AlN Thin FilmsE. Milyutin1, S. Harada1, D. Martin2, J. F. Carlin2, N. Grandjean2, V. Savu3, O. Vaszques-Mena3, J.

Brugger3 and P. Muralt1

1Ceramics Laboratory, Ecole Polytechnique Federale de Lausanne EPFL, Lausanne, Switzerland2Laboratory of Advanced Semiconductors for Photonics and Electronics, Ecole Polytechnique

Federale de Lausanne EPFL, Lausanne, Switzerland3Microsystems Laboratory, Ecole Polytechnique Federale de Lausanne EPFL, Lausanne, Switzerland

We report on the ability to control the polarity of sputter deposited AlN(001) thin films using seedlayers. Reactive sputter deposition leads to N-polarity on any substrate hitherto applied, i.e. Si(111),sapphire, SiO2, polycrystalline metals such as Pt(111), Mo(110), W(110), etc. A site-controlled polarityallows for an efficient excitation of shear modes of surface, bulk, and Lamb waves by interdigitatedelectrodes. We were able to introduce the Al-polarity through a MOCVD seed layer. By subsequentlypatterning the substrate surface it was possible to define the desired film polarity of sputter depositedAlN film. Polarities were determined by selective etching with KOH solutions and by piezoresponseforce microscopy (PFM).


Hyper Frequency Properties of “3 Inches-frozen Capacitive MEMS” withPZT Thin Films Processed by Sol-gel

M. Pham Thi1, P. Martins1, A.Leuliet1, M. Pate1 and A. Ziaei1

1Thales Research Technology France, 1 Avenue A. Fresnel, 91676 Palaiseau Cedex Francee-mail: [email protected]

RF-MEMS have a crucial role to play in future wireless systems through the development of fil-ters, high-Q inductors, high-density capacitors and low loss switches to enable novel and improved RFtransceiver front-ends. Compared with FETs or PIN diodes, RF MEMS present lower insertion loss inthe “on state” and better isolation in the “off state”. Most of capacitive RF MEMS use Si3N4 as dielectriclayer. Its low dielectric constant (7@few GHz) limits the performance of device at low frequency.

PZT exhibiting high-k dielectrics constant were investigated in capacitive MEMS to lower theswitching bandwidth up to 2 GHz. A frozen capacitive MEMS switch, that simulates a MEMS in it“on state” consists of coplanar lines shunted by a dielectric patch. Gold electrodes were deposited byevaporation and PZT or derived PZT thin films were obtained by spin coating onto 3 inch Silicon sub-strates. Crystallization of PZT thin film was optimized about 500 C in order to limit the diffusion of Auelectrode. At this temperature pure perovskite thin films exhibiting a dielectric constant of 500-1000@2-7 GHz were observed. The increase of dielectric constant with thin film thickness is consistent withdata in the literature and reveals the presence of dead layer at electrode/PZT interface thin film. Thevariation of the dielectric constant versus frequency, measured for three capacitance dimensions exhibitsa circuit resonance from 4 GHz to 9 GHz for the value of capacitance from 82 pF to 22 pF. These res-onances perturb dielectric constant determination and imply the right choice of capacitance dimensionversus frequency. Influence of bias on dielectric properties were measured in order to evaluate PZTbehaviour during switching.

HF measurements were done from 1 GHz to 20 GHz. The reflection coefficients are high, between−0.5 and −0.6 dB for most lines. At 10 GHz all the shunted lines have high attenuation, better than−39 dB. These data are promising and implementation of PZT and derived PZT thin film in MEMSprocess is in progress.


Active Damping with A Piezoelectric MEMS DeviceThierry Verdot1, Paul Muralt2 and Manuel Collet1

1Femto-st institute, Departement de Mecanique appliquee, France2Ecole Polytechnique Federale de Lausanne (EPFL), Laboratoire de Ceramique (LC), Switzerland

Active stabilization strategies offer interesting prospects for the protection of embedded MEMS de-vices against accelerations generated by their vibrating support. Moreover, downscaling operated inmicrotechnology brings substantial benefits. First, the reduced amount of mass to control lowers dras-tically the energy required for the active stabilization. Then, the large variety of coupling mechanisms,mature in microengineering, offers facilities for the integration of actuators and sensors required for con-trol implementation. The device presented at the 2nd International Workshop on piezoelectric MEMS isa piezoelectric Micro Active Suspension prototype dedicated to the application of a stabilization strategycalled Integral estimated-Force Feedback. Basically, it is a mechanical suspension etched in a silicon-on-insulator wafer and equipped with an actuator/sensor pair integrated via a Pb(Zr0.53,Ti0.47)O3 thinfilm deposited by gradient free sol-gel route. Obtained ferroelectric transducers exhibit high transversepiezoelectric coefficient in the linear domain restricted to ±2 V. Their remarkable authority on suspen-sion dynamic combined to a weak electrical “cross-talking” enables the implementation of the controllerby using a restricted number of electronic analog low-voltage components. The transfer functions ofthe closed-loop system, recorded during experimental test conducted on a vibrating table, emphazisesky-hook damping actively introduced that stabilizes suspension dynamic while preserving isolationperformances above its cutoff frequency.


Modelling of Piezoelectric Micromachined Ultrasound Transducers(pMUT) for Medical UseAndreas Vogl1 and Dag T. Wang1

11SINTEF ICT, Department of Microsystems and Nanotechnology, Oslo, Norway

PiezoMEMS transducers consist often of multilayered thin-film structures which are difficult tomodel with finite element modelling (FEM) tools due to high aspect ratio of the geometry. Therefore, aset of analytical models for different variables in the transfer function of the pMUT has been developedas a checking point for the multiphysics FEM simulations.

The transfer function for the frequency f of the circular, membrane based ultrasound transducer inbending mode can be written as the quotient of amplitudes of average deflection and applied voltage tothe structure:

H( f )≡ y0

V0=

kM(V0)R2in ln

(RmRin

)2Dm[k + j2π f Z( f )−m(2π f )2]

.

Here we use the spring constant k, the piezoelectric bending moment due to the voltage M(V ), the radiiRin (inner radius of the actuation electrode) and Rm (membrane radius), the flexural rigidity Dm, theacoustic impedance Z( f ) (defined as in [1]) and the membrane effective mass m.

The results of the analytical modelling and a FEM model in COMSOL multiphysics regarding thefirst eigenfrequency and centre displacement for a pMUT in water were compared and showed onlyminor deviations. A combination of both modelling types has been used for the modelling of pMUTSwhich are currently under manufacturing at SINTEF. This approach allows for a quick exploration of thedesign space with the analytical models for this multiphyscis problem and providing a check point forthe time consuming optimal meshing of the high-aspect ration geometries for FEM. At the same timeimportant design parameters can also be identified. The multiphysics FEM simulations give additionalqualitative and quantitave information e.g. higher order eigenmodes close to the first one.

[1] Kinsler, L.E., Fundamentals of acoustics. 4th ed. 2000, New York ; Chichester: Wiley. xii, 548 p.[2] Muralt P., Kholkin M., Kohli M., Maeder T, 1996, Piezoelectric actuation of PZT thin-film diaphragms at staticand resonant conditions, Sensors and Actuators A53, 398-404


Piezoelectric MEMS Fabrication Integrating Thermally andMechanically Incompatible Materials

P.B. Kirby1 and R.V.Wright1

1Cranfield University,UK

In common with a number of other technologically important thin film materials high temperaturesare required for the growth of high quality piezoelectric films either for film deposition itself or duringa subsequent anneal which can make them difficult to integrate with conventional e.g. CMOS devices.Also with the advent of plastic electronics mechanical constraints are now becoming important: the me-chanical strain in flexible circuits for example can reach ∼3% which is well above the breaking strainof many inorganic piezoelectric materials. It is possible with some materials to overcome thermal in-compatibilities by reducing film growth temperature a good example of which is sol-gel deposited PZT,which can be grown at temperatures as low as 500 C, but an attractive option which has recently beendeveloped is transfer bonding in which the piezoelectric layer is deposited on a separate wafer, thenbonded to the low temperature substrate and finally removed from its original substrate by mechanicalgrinding and/or chemical etching or if the substrate is uv transparent by excimer laser ablation. Strate-gies to deal with mechanical incompatibility include use of a temporary rigid backing to enable planarprocessing and strain relief measures such as buckled interconnecting beams and strain isolating layers.

In the present work some of these approaches have been applied to a range of piezoelectric devices toovercome thermal and mechanical constraints. Thin film PZT actuated DC contact RF MEMS switcheshave been fabricated using two types of transfer bonding technique one in which stud bonding is com-bined with laser ablation for selective device transfer and another which employs adhesive bonding forfull wafer device transfer. Good switching performance has been achieved with both. A simple processfor the transfer of thin film PZT structures onto polydimethylsiloxane (PDMS) for energy harvesting ap-plications has also been demonstrated in which a Si substrate containing the structures is pressed againsta separate PDMS coated substrate and then etched away by deep reactive ion etching. The transferredstructures appear well bonded but some reduction in their ferroelectric, and hence piezoelectric, proper-ties following transfer has been observed. ZnO based thin film bulk acoustic resonators (FBARs) havebeen fabricated directly onto a flexible liquid crystal polymer by pre-bonding the flexible substrate toa rigid backing wafer to enable conventional planar processing and lowering the ZnO growth tempera-ture to 200 C. A high effective electromechanical coupling constant (k2) has been achieved ∼6.7% butthe low growth temperature and consequent non-optimum grain structure is believed to have led to thelimited series and parallel Q values that are observed (126 and 78 respectively).

Part III

W 7, SO


All-oxide PiezoMEMS Devices by Pulsed Laser Deposition: Properties ofClamped Epitaxial PZT Thin Films

Guus Rijnders1

1MESA+ Institute for Nanotechnology, University of Twente, POBox 217,7500AE, Enschede,Netherlands

Ferroelectric oxides, such as Pb(Zr,Ti)O3 (PZT), are very useful for electronic and photonic devices,as well as piezomechanical actuators and sensors. The ferro- and piezoelectric properties are stronglyrelated to the crystal orientation as well as the strain state of the PZT layer. Successful integration ofthese devices into silicon technology is therefore not only dependent on the ability of epitaxial growthon silicon substrates, but also the control of the crystallographic orientation and the residual strain stateof the deposited PZT thin film.

A study will be presented on the effects of the residual strain in PZT thin films on the ferroelectricand piezoelectric properties. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched betweenSrRuO3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinationsby pulsed laser deposition. All the PZT films show ferroelectric behavior that is consistent with thesingle domain ferroelectric r-phase. Compressive or tensile stress caused by the difference in thermalexpansion of the PZT film and substrate influences the ferroelectric and piezoelectric properties. Theirdependences on this misfit strain are in good correspondence with theoretical predictions. We concludethat clamped (001) oriented single domain Pb(Zr0.52Ti0.48)O3 thin films strained by the substrate alwaysshow rotation of the polarization vector.

In this contribution, I will furthermore highlight the recent progress on the fabrication of all-oxidepiezo-MEMS devices by pulsed laser deposition.


Introduction of New Manufacturing Technology for Piezo (PZT) MEMSProductionJanssens, Arjen1

1CEO SolMateS, [email protected]

The MEMS market is growing fast of which PiezoMEMS applications are showing high marketpotential. Many companies are working on Piezo actuated MEMS, trying to get their application fromdevelopment towards production. One of the major challenges in this process is the reliable integrationof the Piezo material (PZT) on the silicon wafer. The deposition of PZT on silicon wafers is not straight-forward as the optimal material performance; yield and stability are hard to achieve using traditionaldeposition technologies. For this reason SolMateS offers the PiezoFlare 1200 to deposit PZT thin filmson 6" and 8" wafers.

This thin film platform uses laser deposition to deposit PZT and oxide electrodes in the same reactor.Due to its modular configuration we have a solution from research till production. The PiezoFlare 1200is designed to manufacture reliable PZT thin films. Measurements show high and homogeneous piezoperformance on each wafer, and stable values from wafer to wafer. The PiezoFlare 1200 enables reliableproduction capability for PZT thin film deposition.

After the PZT thin films (1-3 µm) are deposited no poling and RTA is required. Wafer mappingusing DBLI (AixaCCT systems) show uniform d33 values across the wafer with values of 180 pm/Voltor higher for a 1mm2 pad size and 2 µm PZT thin films. From cantilever tip displacement measurementsd31 values of 120 pm/V and higher are calculated. Furthermore measurements show stable membraneand cantilever actuation till 1010 cycles.


Epitaxial Ferroelectric Pb(Zr0.2Ti0.8)O3 Thin Films on Silicon: Growthand Physical Properties

S. Gariglio1, A. Sambri1, P.Janphuang2, D. Isarakorn2, D. Briand2, J.W. Reiner3, A. Torres Pardo4, O.Stephan4, C.H. Ahn3, N.F. de Rooij2 and J.-M. Triscone1

1University of Geneva, Switzerland2Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland

3Yale University, USA4Universite Paris-Sud, France

This work discusses the growth and properties of epitaxial ferroelectric layers on silicon for piezo-electric MEMS devices. Nowadays it is possible to control the growth of epitaxial thin films of per-ovskite structure on silicon substrates using a SrTiO3 layer as a chemical and structural buffer. Theintegration of this crystalline oxide layer on silicon requires a complex multi-step procedure achievedby molecular beam epitaxy. The successive bottom electrode SrRuO3 and ferroelectric Pb(Zr0.2Ti0.8)O3thin films are grown by reactive magnetron sputtering. We currently master this process on 3 inch siliconsubstrates.

The structural analysis performed by transmission electron microscopy and x-ray diffraction revealsa full epitaxial relation between the layers. Polarization-voltage loops, measured at room temperatureon 100×100 µm2 Cr/Au top electrodes, reveal a remnant polarization and a coercive field of about70 µC/cm2 and 250 kV/cm, respectively. Piezo-force microscopy yields an estimation of the piezoelec-tric d33 coefficient of 50 pm/V.

As for ferroelectric materials it is well known that the mechanical boundary conditions affect sub-stantially the ferroelectric properties through the strain-polarization coupling, we have investigated theeffect of the epitaxial strain on the critical temperature of the paraelectric-ferroelectric phase transition.

A. Sambri et al., Appl. Phys. Lett. 98, 012903 (2011).


Oerlikon PVD Production Solution for in-situ Large Scale Deposition ofPZT Films

Kratzer M.1, Kaden D.2, Quenzer H J.2, Castaldi L.1, Heinz B.1, Harada S.3, Mazzalai A.3 and Muralt P.3

1Oerlikon Balzers, Liechtenstein2Fraunhofer ISIT, Germany

3EPFL, Switzerland

The direct growth of piezoelectric PZT films by RF sputtering (PVD) is considered as the depositionmethod particularly suitable to satisfy the increasing demand for this material type driven by variousapplications like sensors, energy harvesting devices, ink-jet printing heads and other active components.This is because of the remarkable advantage of the PVD deposition method to grow high quality filmsin a single process step (in-situ) without post annealing.

One prerequisite for the in-situ growth of the correct crystalline perovskite structure is the tighttemperature control of the substrate in the range of 500 C during film deposition. Challenges arisebecause of the required temperature uniformity especially for the large wafer size of 200 mm. Furtheron the sputter equipment has to be optimized to enable a deposition process at a high throughput whichis a key factor for minimized cost of ownership for PZT volume production.

The status of the tool development for in-situ deposition of PZT films by sputtering will be presented.The hardware capabilities will be shown and their influence on the PZT film properties will be discussed.

As a result high quality PZT films were deposited on 8" wafer showing a considerable piezoelectricperformance with highest piezoelectric coefficients d33,f of 120 pm/V and e31,f of−13.8 C/m2 on 200 mmsubstrate size.


Measurements of Electrical and Electromechanical Characteristics ofPiezoelectric Thin Films and Optimization of Poling

Stephan Tiedke1, Roland Kessels1, Thorsten Schmitz-Kempen1, Gwenael Le Rhun3, Dirk Kaden4 andPaul Muralt5

1aixACCT Systems GmbH, Germany3CEA-LETI, France

4Fraunhofer Institut fur Siliziumtechnologie, Germany5Swiss Federal Institute of Technology EPFL, Switzerland

The first mass-products of Micro-Electro-Mechanical Systems (MEMS) based on piezoelectric thinfilms have been introduced into the market. A broad range of new applications are currently beingdeveloped e.g. energy harvester for autonomous devices, new ink-jet printer heads, RF-switches andtilted mirror arrays. With more products under development the need of accurate and standardizedcharacterization of piezoelectric films is increasing.

The characterization of the piezoelectric film properties is essential for device design as well asdevice simulation and critical for process qualification. Different measurement methods for the investi-gation of the piezoelectric thin film properties will be presented.

The first method presented uses the Double Beam Laser Interferometer (DBLI) to measure the effec-tive longitudinal (d33,f) coefficient of piezoelectric thin films on wafer level up to 8 inch. Resolution andlong-term repeatability were verified by an x-cut quartz sample and 8 inch wafers with AlN thin films asa stable reference piezoelectric material.

The second method focuses on thin film samples on silicon substrates where the electrode layout isadapted to our 4-point bending setup for measurement of the transversal piezoelectric (e31,f) coefficientunder well-defined homogeneous mechanical strain. Stress and corresponding strain distributions inthe film were verified by Finite Element simulations. Repeatability was also verified on AlN thin filmsamples. This combination of setups allows fast and accurate measurements of both coefficients onPb(Zr,Ti)O3 (PZT) thin films.

In the second part of the presentation it will be shown that careful poling of Pb(Zr,Ti)O3 (PZT) thinfilms under elevated temperature and different excitation signals can significantly increase the piezoelec-tric coefficients. In some cases the e31,f coefficient could be increased by 50% or more. Optimizationsof the poling condition will be presented and the results will be summarized.


Direct And Indirect Piezoelectric Characterization of PZT Thin Films forMEMS Applications

Abergel, J.1, Cueff, M.1, Michaud, H.1, Allain, M.1, Ricart, T.1, Dieppedale, C.1, Suhm, A.1, Kessels,R.2, Tiedke, S.2, Le Rhun, G.1, Fanget, S.1, Aıd, M.1 and Defay, E.

1CEA LETI Minatec Campus, 38054 Grenoble, France2AixACCT Systems GmbH Dennewartstr. 25, D-52068 Aachen, Germany

Pb(Zr,Ti)O3 (PZT) thin films have been extensively studied during the last 20 years because of theiroutstanding ferroelectric, dielectric and piezoelectric properties. However, it appears that there is still alarge discrepancy between the communicated piezoelectric coefficients. This is closely related to the factthat thin films are clamped to their subtrates. Thus, only effective piezoelectric coefficients, which are acombination of purely piezoelectric coefficients and elastic constants, can be extracted. Moreover, thinfilms elastic constants are not well known: that increases the difficulty to determine pure piezoelectriccoefficients.

In this study, we propose to implement a direct and indirect piezoelectric characterization of PZTfilms in order to provide a clear assessment of the transverse piezoelectric coefficients. Those char-acterizations give the opportunity to eventually determine e31, d31 and the Young modulus of thesePZT thin films. (100)-oriented sol-gel 2 µm-thick Pb(Zr0.52,Ti0.48)O3 films were deposited on 200 mmSOI wafers. The final stack was Si substrate/0.5 µm-SiO2 (BOX)/5 µm Si (SOI)/0.5 µm-SiO2 /0.1 µmPt/2 µm-PZT/0.1 µm Ru. Two types of piezoelectric characterizations were performed on these films.On one hand, the effective direct transverse coefficient e31,eff was extracted by using the 4-points bendingmethod provided by Aixacct [1]. On the other hand, the indirect transverse coefficient d31 was extractedfrom measuring the deflection with a WYCO interferometer of a processed membrane actuated by thePZT film. PZT membranes were released by a back-side etching process. Thanks to the SOI processedsubstrates, the cavity length is very well-controlled. That consequently makes these devices particularlysuitable for d31 measurements. d31 was fitted by using a Finite Element Model (Comsol).

The extracted e31,eff value is −15.95 C/m2. It is worth noting that e31,eff does not require PZT’sYoung Modulus EPZT to be determined. The extracted d31 value is −150 pm/V. In this case, EPZT plays aminor role on the mechanical behaviour of the membrane which is mainly influenced by the 5 µm thickSOI Si layer. Moreover, e31,eff, d31 and the Young modulus E are linked by d31=e31,eff(1-ν)/E, whereν is the Poisson ratio. By using ν=0.3, the evaluated E is 74 GPa, which fits with PZT bulk ceramicsvalues reported in the literature for PZT in morphotropic phase [2]. Therefore, a careful characteriza-tion of direct and indirect piezoelectric coefficients of PZT films gives consistent data with the typicalfollowing values: e31,eff=−15.95 C/m2, d31=−150pm/V and EPZT=74 GPa.

[1] K. Prume, P. Muralt, F. Calame, T. Schmitz-Kempen, and S. Tiedke, “Piezoelectric thin film: evaluation ofelectrical and electromechanical characteristics for MEMS devices,” IEEE Trans. Ultrason., Ferroelectr., Freq.Control, vol. 54, no. 1, pp. 8-14, 2007.[2] A. K. Singh, S. K. R. Mishra, D. Pandey, S. Yoon, S. Baik, and N. Shin, “Origin of high piezoelectric responseof Pb(ZrxTi1−x)O3 at the morphotropic phase boundary: Role of elastic instability,” Appl. Phys. Lett, vol. 92,no.2. art. no. 022910, 2008.


Spin-Coat Technology of KNN Film Deposition with Oxygen PressurizingRTA

Takeshi Kijima1, Takekazu Shigenai1 and Yuji Honda1

1Youtec Co.,Ltd. Japan

Recently, KNN ceramics is expected to next generation piezoelectric material as lead-free. Howeverthere are only several reports of the KNN film deposition by PVD as thin film. This study reportsa success in the KNN film deposition by Spin-Coat Technology with the Oxygen Pressurizing RTA.Spin-Coat technology is suitable for industrial production more than PVD concerning its cost.

We developed an original KNN sol-gel solution and deposition process. High concentration KNNsolution (25 weight %) is a feature of our original sol-gel solution and high pressure oxygen (about10 atm) during RTA process is a feature of our original deposition process. Combining high pressureoxygen and high concentration KNN solution provides the highest KNN crystal growth rate withouthelp of a substrate orientation. We consider that chemical kinetics is applied to the KNN crystal growth.The KNN crystal growth prvided from an upper surface of an amorphous KNN film is fastest growth. Acrystallization direction of an ingredient (110) is the strongest like a KNN bulk.

Very thin piezofilms are deposited on the KNN film to cap it and spun it before RTA process. Thiscap layer prevents an alkaline metal from evaporating and assists a crystallization of the KNN film fromthe upper surface. Now we have developed that the KNN film may be crystallized in a (110) directionof a polarization axis.


Spin-Coat Technology of KNN Film Deposition with Oxygen Pressurizing RTA

Takeshi Kijima, Takekazu Shigenai and Yuji Honda

Youtec Co.,Ltd. Japan

Recently, KNN ceramics is expected to next generation piezoelectric material as lead-free. However there are only several reports of the KNN film deposition by PVD as thin film. This study reports a success in the KNN film deposition by Spin-Coat Technology with the Oxygen Pressurizing RTA. Spin-Coat technology is suitable for industrial production more than PVD concerning its cost. We developed an original KNN sol-gel solution and deposition process. High concentration KNN solution (25 weight %) is a feature of our original sol-gel solution and high pressure oxygen (about 10 atm) during RTA process is a feature of our original deposition process. Combining high pressure oxygen and high concentration KNN solution provides the highest KNN crystal growth rate without help of a substrate orientation. We consider that chemical kinetics is applied to the KNN crystal growth. The KNN crystal growth prvided from an upper surface of an amorphous KNN film is fastest growth. A crystallization direction of an ingredient (110) is the strongest like a KNN bulk. Very thin piezofilms are deposited on the KNN film to cap it and spun it before RTA process. This cap layer prevents an alkaline metal from evaporating and assists a crystallization of the KNN film from the upper surface. Now we have developed that the KNN film may be crystallized in a (110) direction of a polarization axis. Figure.1 shows a cross section of the KNN film. 2um thick KNN film with flat and smooth surface was obtained. The cap layer was not obtained. Figure.2 shows XRD of the KNN film. This film has single layer with (110). Figure.3 shows C-V carve of KNN. 2Pr is 30uC/cm2 at 100V.

Fig.1 Fig.2 Fig.3 Fig. 1 shows a cross section of the KNN film. 2 µm thick KNN film with flat and smooth surface wasobtained. The cap layer was not obtained.Fig. 2 shows XRD of the KNN film. This film has single layer with (110).Fig. 3 shows C-V carve of KNN. 2Pr is 30 µC/cm2 at 100 V.


Properties of PMN-PT 65/35 thin film oriented -〈011〉 at radio frequencymeasured by coplanar waveguide

Kim-Anh Bui-Thi1,2, Mai Pham-Thi1, Gui Garry1, Aude Leuliet1, Michel Pate1, Paolo Martins1,Afshin Ziaei1 and Philippe Lecoeur2

1Thales Research & Technology, Palaiseau, France2Institut d’Electronique Fondamentale, Orsay, France

In capacitive MEMS (micro-electro-mechanics systems) applications, the dielectric constant decidesusually the working frequency of the device. Communly used dielectrics like Si3 3N4, SiO2, ZrO2...allow good isolation at high frequency (30 GHz). In order to adapt the component for the radar appli-cations (10 GHz) and telecommunication (500 MHz-3 GHz), one has to increase the capacitace of thedevice by replacing these dielectrics by a high-k dielectric or by modifying the capacitance dimensionsand the thin film thickness. The latters are not very effective since they can increase only a few times thecapacitance while changing the dielectric can increase the capacitance sometimes a factor of 100. Thatis the reason why high-k dielectric becomes the best choice to optimize the working frequency.

Well known as a very good material for MEMS actuators and sensors, PMN-PT has been studiedsince a long time mainly to optimize its electro-mechanical response. In order to obtain high-k dielectricfor radiofrequency micro-electro-mechanics systems, we have concentrated recently on PMN-PT 65/35because of its actractive permittivity. A lack of knowledge of this PMN-PT thin film at radio frequencyleads us to characterize these properties with a coplanar waveguide.

We have succeeded to grow PMN-PT thin film oriented 〈011〉 by Pulsed Laser Deposition on met-alized silicon substrate. The very small remnant polarization of the PMN-PT oriented 〈011〉 is muchmore advantageous than the usual 〈001〉 and 〈111〉 orientation for the functioning of the rapide MEMSSwitch applications. Our coplanar waveguide short-circuit (the coplanar waveguide isolated with ablocked transversal metal line by a PMN-PT thin film) shows a good agreement between the simulationwith High Frequency Simulation Software and the RF measurement (the isolation S12 in both cases is−40 dB around 10 GHz). The simulation considers the variation of the material permittivity in fre-quency using Debye relaxation model. The RF measurement has been carried on different capacitancedimensions to make sure of the accuracy of the results. The working frequency range of our MEMSSwitch test using PMN-PT is very large: from 500MHz up to 20 GHz. This encouraging result showsthat it is possible to use this material for both applications in radars and telecommunication.


Influence of Solution Synthesis Conditions on Crystallization andProperties of Functional Oxide Thin Films

Barbara Malic1,2, Sebastjan Glinsek1,2, Alja Kupec1, Brigita Kuznik1,2, Elena Tchernychova1,2 andMarija Kosec1

1Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia2Centre of Excellence SPACE.SI, VESOLJE.SI, Askerceva 12, 1000 Ljubljana, Slovenia

Ceramic functional-oxide thin films with enhanced functional properties, such as dielectric per-mittivity, voltage tunability, remanent polarisation, piezoelectric properties, or electrocaloric effect, toname only a few, have been studied for different microelectronic and microelectromechanical applica-tions, including thin film capacitors, memories, sensors, actuators, tunable microwave devices or microheating/cooling devices.

Thin film microstructure critically influences the functional properties. In case of Chemical Solu-tion Deposition (CSD), the crystallisation and evolution of the film microstructure depend on, and maytherefore be tailored by the chemistry of the sol, the choice of the substrate, and by the processingconditions, mainly by the temperatures and times of the individual heat treatment steps - drying, pyrol-ysis and annealing. For example, the dielectric permittivity and voltage tunability of solution-derivedBa0.3Sr0.7TiO3 (BST) thin films were almost doubled, namely from 345 and 1.47, to 722 and 1.93, asthe grain size was increased from 40 nm to 80 nm. (B. Malic et al., J. Europ. Ceram. Soc. 27 (2007)2945.) In solution-derived PbZr0.3Ti0.7O3 (PZT) thin films, the design of microstructure and preferentialorientation of the perovskite phase with consequent changes of dielectric permittivity and ferroelectricproperties could be achieved by the choice of the reagents and the deposition-heating sequence. (B.Malic et al., Integr. Ferroel., 100 (2008) 285.)

The contribution addresses the design of microstructure of selected ferroelectric complex perovskitethin films based on lead-free perovskites: incipient ferroelectric potassium tantalate, potassium tantalate-niobate, and potassium sodium niobate; which has been, in the bulk ceramic form, extensively studiedas the lead-free piezoelectric, with properties of some modified compositions comparable to those oflead-based perovskites.

The correlation between the film microstructure and respective functional properties and the detailsof the solution syntheisis of individual material compositons are discussed.

The work was supported by the Slovenian Research Agency (program P2-0105; young researcherprogram, contract number: 10000-07-3100068) and by the European Union and Ministry of HigherEducation, Science and Technology of Slovenia.


Low Temperature Laser Processing of Ferroelectric Thin FilmsS. S. N. Bharadwaja1, F. Griggio1, W. Qu1, J. Kulik1, T. Clark1, H. Beratan2 and S. Trolier-McKinstry1

1Materials Research Institute, The Pennsylvania State University, University Park, PA 168022Bridge Semiconductor Corporation, Pittsburgh, PA 15235

Low thermal budgets for processing of ferroelectric films are important for nonvolatile memories,pyroelectric detectors, miniaturized piezoelectric transducers, and embedded dielectrics. Most comple-mentary metal oxide semiconductor (CMOS) based read-out circuits can withstand processing tempera-tures less than 450 C; however large thermal budgets (>500 C) are required to crystallize ferroelectricthin films such as Pb(Zr,Ti)O3 and BaTiO3. Using KrF excimer laser annealing and oxidation, the sub-strate temperatures can be reduced below 400 C.

In this presentation, three main topics will be discussed:(i) Crystallization kinetics of Pb(Zr,Ti)O3 thin films within the framework of rate dependent Avrami

theory under non-isothermal conditions. The resultant electrical properties of laser annealed films arecomparable to those of rapid thermally annealed Pb(Zr,Ti)O3 thin films.

(ii) Orientation control in laser annealed Pb(Zr,Ti)O3 52/48 thin films using a bottom template layerat substrate temperatures below 400 C. Both 111 and 100 orientations were achieved in ∼200-300 nm thick PZT layers on (111) Pt and 001 PbTiO3 surfaces. The measured average remanent polariza-tion and coercive fields are 31 µC/cm2 and 86 kV/cm for 001 PZT films and 23.6 µC/cm2 and 64 kV/cmfor 111 oriented PZT thin films respectively. The maximum e31,f coefficients are ∼ −9.0 C/m2 for001 and ∼−8.5 C/m2 for 111 PZT thin films respectively.

(iii) Oxidation kinetics of ∼200 nm thick BaTiO3 thin films on Ni foils in O2/O3 (90/10) at substratetemperature below 400 C for base metal capacitor applications. The resultant films have small signaldielectric permittivities ∼ 1100 with <4% loss values between 0.1-1 kHz. Well-controlled interfacesbetween the BaTiO3 and the Ni foil, without indication of a NiO reaction layer are confirmed from elec-tron energy loss spectroscopy (EELS) and high resolution transmission electron microscopy (HRTEM)studies.


FP7 piezoVolume - High Volume Piezoelectric Thin Film ProductionProcess For Microsystems

Tyholdt F1, Haavik C.1, Mazzalai A.2, Tiedke S.3, Kessels R.3, Kratzer M.4, Kaden D.5, Schropfer G.6,Cruau A.6, Muffler P.7, Herrmann R.7, Muralt P.2

1SINTEF, Norway; 2EPFL, Switzerland; 3aixACCT, Germany; 4Oerlikon Baltzers, Liechenstein;5Fraunhofer ISIT, Germany; 6Coventor, France; 7Solar-semi, Germany

The main goal of FP7 piezoVolume (2010−2013) (www.piezovolume.com) is to develop a platformof integrated processes for production of piezoelectric microsystems. In this platform the processes andprocedures specific to piezoMEMS have been identified i.e.: piezoMEMS modeling and process emula-tion, piezoMEMS design including design rules, PZT deposition tools for production, in-line piezoelec-tric thin film quality monitoring and a standard fabrication process including fab integration procedures.piezoVolume develops solutions for all the elements in this platform. Even though the current mainbottleneck is the availability of piezoelectric thin film deposition tools capable of delivering suitabledeposition rate and performance uniformity, the importance of the other piezoMEMS specific elementsshould not be forgotted when establishing a piezoMEMS fab. We believe that the availability of a com-plete process platform will lower the threshold for industry acceptance and be a key tool to realise newproducts using piezoMEMS.

The status of the ongoing developments within the separate elements of the process platform willbe presented. Some examples from using the commercial piezoMEMS CAD and process emulationsoftware from Coventor will be shown. Modelling of the integration of piezoMEMS and ICs is now alsopossible. Regarding PZT deposition tools, very promising results from single target sputtering on 150and 200 mm wafers have been obtained in the project by Oerlikon, EPFL and Fraunhofer ISIT. Currently,an e31,f of −13.8 C/m2 has been obtained on 200 mm wafers. Also, the status of an automated clustercoater for CSD of PZT from Solar-semi will be presented. In-line quality monitoring is very importantfor process control in a production environment and an automated Double Beam Laser Interferometer(aixDBLI from aixACCT) integratable with a wafer robot capable of non-destructive e31,f estimation,will be shown.

The consortium has the aim of aciting as a contact point and compentece centre for piezoMEMScapable of prototyping and low volume fabrication. The plans for this will be presented.


Manufacture of Minature Tuneable Autofocus Lenses (TLens) using PiezoMEMS

J.W. Phair1 and Daniel Rosenfeld1

1poLight AS, Norway

poLight AS, a Norwegian-based start-up company, has developed the world’s first piezo-actuatedautofocus lenses without moving parts. Its proprietary technology enables the production of wafer-scaleactive optic components based on deformable polymers. poLight’s TLens offers some crucial advan-tages to the camera module market thanks to its extremely small size (4.2 mm×4.2 mm×0.5 mm), whileachieving high optical quality (megapixel independent and HD compatible). These features, combinedwith its reflow-compatible manufacturing, positions the TLens as the ideal solution for the latest cameraphone applications such as videos with continuous-autofocus. The presentation will discuss the progresspoLight is making in bringing the production of the piezo-actuated TLens from small volume to highvolume including the main technical hurdles. A discussion of piezo production for the TLens, test andmeasurement, integration as well as environmental consideration during the manufacture to high volumewill also be made.


Wafer Level Poling of PZT thin films for MEMS Sensor DevicesSeunghun Han1, Yunsung Kang1, Wonkyu Jung1, Jun Lim1 and Jungwon Lee1

1Samsung Electro-Mechanics, Korea

In recent decades, thin film type PZTs have been spotlighted for MEMS applications because or theirexcellent piezoelectric properties. PZT thin films have to be poled along one direction to have properpiezoelectric properties. However there might be enormous loss in process time or costs by individualchip poling. Furthermore, most of piezo-MEMS devices cannot be operated after poling process, itis impossible to check the performance of device without wafer level poling. For these reasons, it isessential to develop wafer level poling process for MEMS device.

In order to overcome conduction defects problems of wafer level poling for MEMS sensor device,two types of processes were evaluated. Non-contact poling method using corona discharge showedinsufficient remnant polarization of 15 µC/cm2 with PZT surface damages. The other method suppliedexcess current to the conduction defects of the PZT thin film, conduction path was eliminated. In thisway, wafer level poling was successfully demonstrated without any breakdown or degradation of MEMSsensor devices. Remnant polarization of the poled PZT thin films was 20 µC/cm2.


Effects of Nanoscale Confiment on Ferroelectric Properties: ResearchActivity at the Center for Space Human Robotics

V. Cauda1, G. Canavese1, S. Stassi1, M. Lombardi1,2, R. Gazia1, I. Aulika1, M. Quaglio1, C.F. Pirri1,2

1Center for Space Human Robotics, Italian Institute of Technology, C.so Trento 21, Turin, 10129, Italy2Materials Science and Chemical Engineering Department, Politecnico di Torino, Turin, Italy

The activities of Center for Space Human Robotics (CSHR), part of the Italian Institute of Technol-ogy (IIT), are focused on the development and prototyping of integrated systems for human robotics.Particular interest is devoted to the design and fabrication of a hand-exoskeleton for motion support inboth space and human activity. The fabrication of a hand-exoskeleton requires the development of: i)actuators and sensors (e.g. tactile sensors) to properly manage the interface of the exoskeleton withboth the human body and the external environment, ii) electronics to manage the entire system, and iii)energy sources and storage systems to power it. In this scenario CSHR has focused its activity on theeffect of nanoscale confinement on the piezoelectric properties of materials analysed in its three mainforms: thin films as 1D confined structures, nanowires as 2D confined structures and hybrid materialswith nanosized fillers as 3D confined structures.


Figure 1. Polarization hysteresis and displacement curves obtained as a result of 3 cycles. Inset: Scanning electron microscopy image of the PVDF-TrFE nanowires after dissolution of the alumina membrane, with some residues of the dissolved alumina.

Fig. 1. Polarization hysteresis and displacement curves obtained as a result of 3 cycles. Inset: Scanning electronmicroscopy image of the PVDF-TrFE nanowires after dissolution of the alumina membrane, with some residuesof the dissolved alumina.

To obtain flexible and performing materials, piezoelectric hybrids based on barium titanate nanopar-ticles (npBT) dispersed in a 3D polymeric network were developed. In particular electroactive polyvinyli-dene fluoride (PVDF) or passive (UV-cured acrylic or epoxide resins) polymers were used as matrices.Despite the npBT slightly affected the composite mechanical properties, they were able to improve thethermal and functional behaviour. The effect of npBT size distribution and their crystalline phase wereevaluated. Another representative example of increased piezoelectric properties upon nanoconfinementis given by 1D polymeric nanowires.

An ease and fast wet-impregnation method from a solution of PVDF copolymer (PVDF-TrFE) leadin one step to an array of 1D piezoelectric nanostructures distributed in an insulating matrix, i.e. 60 µmthick porous Anodic Alumina Membranes (AAM, Whatman, av. pore size: 200 nm) [1]. The polymericnanowires showed a diameter of about 150 nm, several micrometers in lengths and a high filling ratio ofthe alumina pores (Inset of Fig.1). X-ray diffraction and infrared spectroscopy showed that the high levelof crystallinity is induced by the confinement into the pores of the AAM and results in a pronounced


piezoelectric effect. Hysteresis measurements were recorded simultaneously with sample displacementdata by a Piezo Evaluation System (TFAnalyzer 2000HS, Aixacct) coupled to a single point laser vi-brometer (Polytec OVF-505), showing a polarization curve typical of ferroelectric material with a Pr ofapproximately 14.3 µC/m2 (Fig.1) and coercitive field of 4.3 MV/m. It is noteworthy that the averagedd33 constant (obtained from the linear part of the piezoelectric displacement curve) is about 97 pm/V,which is quite higher with respect to the literature values (from 5 to 20 pm/V of pre-poled thin film ofPVDF-TrFE [2]). Despite the absence of pre-poling of the PVDF-TrFE nanowires, we attribute thishigher d33 value to the higher percent of polymer crystallinity, which is due to the confinement into thepores of alumina.

As a future outlook, these crystalline piezoelectric nanowires distributed in vertical array can be en-gineered in a piezoelectrical MEMS device, thus potentially addressing applications like tactile sensorsfor humanoid robotics.

[1] V. Cauda, et al., Sensors & Tran. J., 2011, accepted.[2] V. Maheshwari, et al., Angew. Chemie, Int. Ed. 2008, 47, 7808.


2010-2015 Market Analysis of PiezoMEMSDr Eric Mounier1

1Yole Developpement, France

Ferroelectric materials are historically not common for semiconductor manufacturing companieswho are often reluctant to adopt these exotic materials in their fabs. But this approach has changed inthe 2000s with the adoption of ferroelectric thin films by well known companies in a variety of markets.

We have analyzed and estimated the MEMS and non MEMS applications for ferroelectric thin films.We particularly looked at the piezo effect of ferroelectric thin films for MEMS. In 2010, we estimatedferroelectric thin film production is about 900 k 6” wafers. It is done through two main applications:MEMS inkjet heads and IPD ESD/EMI planar capacitors that together represent 90% of the production.Large companies (Epson, STM, NXP) have adopted ferroelectric thin films at a large industrial scale forthe past several years.

We estimate that, until 2015, the ferroelectric thin film business will continue to grow at rate of+7.5% / year with many current or new MEMS applications: Wafer Level Autofocus, IR sensors, RFswitches, and medical ultrasonic transducers.

In non MEMS markets, ferroelectric thin filmswill be used for IPD tunable capacitor, IPD hearingaids, FeRAM, optical switches. These applications will represent 26% of the total ferroelectric thin filmproduction in 2015 which will be more than 1,000 k 6" wafers.

Our talk will review the different applications and market volume for piezoelectric MEMS.

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Author Title Page No.

Abergel, J. Direct and Indirect Piezoelectric Characterization of PZT Thin Films for MEMS Applications 40

Baron, T. HBAR and their applications 21

Baron, T. FBAR filters for space application based on LiNbO3 membrane 16

Bharadwaja, R. Low Temperature Laser Processing of Ferroelectric Thin Films 44

Bui-Thi, K.-A. Properties of PMN-PT 65/35 thin film oriented -<011> at radio frequency measured by coplanar waveguide 42

Cauda, V. Effects of Nanoscale Confiment on Ferroelectric Properties: Research Activity at the Center for Space Human Robotics 48

Chidambarm, N Effective piezoelectric coefficients of PZT thin films for energy harvesting with interdigitated electrodes 22

Chidambarm, N Interdigitated Electrodes Based Cantilevers for Piezoelectric Energy Harvesting 26

Felmetsger, V. Reactive Magnetron Sputtering of Ultrathin Piezoelectric 23

Felmetsger, V. Sputter Deposition of Piezoelectric AlN Thin Films on Vertical Walls of Micromechanical Devices 12

Gariglio, S. MEMS Based Piezoelectric Harvesters: From Thick Sheet to Thin Film Epitaxial Piezoelectric Materials 8

Gariglio, S. Epitaxial Ferroelectric Pb(Zr0.2Ti0.8)O3 Thin Films on Silicon:Growth and Physical Properties 37

Han, S. Wafer Level Poling of PZT thin films for MEMS Sensor Devices 47

Han, S. Influence of Temperature and O2 Flow Rate on the Structure and Ferroelectric Properties of PZT Films Deposited by RF Magnetron Sputtering

24

Harigai, T Piezoelectric Thin Films and Their Applications 3

Jackson, N. Influences of Titanium Underlayer on (002) Oriented Aluminium Nitride 25

Janphuang, P. MEMS Based Piezoelectric Harvesters: From Thick Sheet to Thin Film Epitaxial Piezoelectric Materials 8

Janphuang, P. Epitaxial Ferroelectric Pb(Zr0.2Ti0.8)O3 Thin Films on Silicon:Growth and Physical Properties 35

Janssens, A. Introduction of new manufacturing technology for Piezo (PZT) MEMS production 36

Kaden, D. Oerlikon PVD production solution for in-situ large scale deposition of PZT films 38

Kaden, D. Measurements of Electrical and Electromechanical Characteristics of Piezoelectric Thin Films and Optimization of Poling

37

Kang, S.-Y. Influence of Temperature and O2 Flow Rate on the Structure and Ferroelectric Properties of PZT Films Deposited by RF Magnetron Sputtering

24

b

Kang, S.-Y. Wafer Level Poling of PZT thin films for MEMS Sensor Devices 44

Kessels, R. Measurements of Electrical and Electromechanical Characteristics of Piezoelectric Thin Films and Optimization of Poling

37

Kessels, R. Direct and Indirect Piezoelectric Characterization of PZT Thin Films for MEMS Applications 38

Kijima, T. Spin-Coat Technology of KNN Film Deposition with Oxygen Pressurizing RTA 41

Kirby, P. Piezoelectric MEMS Fabrication Integrating Thermally and Mechanically Incompatible Materials 31

Klee, M. Piezoelectric Thin Films: A Technology Platform for Thin Film Ultrasound Transducer Arrays 4

Kosec, M. Influence of Solution Synthesis Conditions on Crystallization and Properties of Functional Oxide Thin Films 41

Kratzer, M. Oerlikon PVD production solution for in-situ large scale deposition of PZT films 38

Le Rhun, G. Measurements of Electrical and Electromechanical Characteristics of Piezoelectric Thin Films and Optimization of Poling

39

Le Rhun, G. Direct and Indirect Piezoelectric Characterization of PZT Thin Films for MEMS Applications 40

Lombardi, M. Effects of Nanoscale Confiment on Ferroelectric Properties: Research Activity at the Center for Space Human Robotics 45

Malic, B. Influence of Solution Synthesis Conditions on Crystallization and Properties of Functional Oxide Thin Films 43

Mathewson, A. Influences of Titanium Underlayer on (002) Oriented Aluminium Nitride 25

Matloub, R Electromechanical properties of Al0.9Sc0.1N thin films evaluated at 2.2 GHz Film bulk acoustic resonators 15

Mauczok, R. Piezoelectric Thin Films: A Technology Platform for Thin Film Ultrasound Transducer Arrays 4

Mazzalai, A. Effective piezoelectric coefficients of PZT thin films for energy harvesting with interdigitated electrodes 22

Mazzalai, A. Interdigitated Electrodes Based Cantilevers for Piezoelectric Energy Harvesting 26

Mazzalai, A. Oerlikon PVD production solution for in-situ large scale deposition of PZT films 36

Metzger, T. New Trends in Piezoelectric Devices for RF Application in Mobile Phones 13

Milyutin, E. Electromechanical properties of Al0.9Sc0.1N thin films evaluated at 2.2 GHz Film bulk acoustic resonators 15

Milyutin, E. Local Polarity Control of (001)AlN Thin Films 27

Moulard, G. New Trends in Piezoelectric Devices for RF Application in Mobile 13

c

Phones

Mounier, E. 2010-2015 Market Analysis of PiezoMEMS

50

Muralt, P. 15, 22, 26, 27, 29, 38,

39, 45 Pensala, T. Piezoactuated AlN-Si MEMS Resonators and Sensors 14

Phair, J. Manufacture of Minature Tuneable Autofocus Lenses (TLens) using Piezo MEMS 46

Pham-Thi, M. Hyper Frequency properties of “3 inches-frozen capacitive MEMS” with PZT thin films processed by sol-gel 28

Pham-Thi, M. Properties of PMN-PT 65/35 thin film oriented -<011> at radio frequency measured by coplanar waveguide 42

Piazza, G. Laterally Vibrating Micro and Nanomechanical Piezoelectric Aluminum Nitride Resonators for RF Communications and Chemical Sensing

11

Piorra, A. Lead Free Laser Deposited Thin Films Of 0.5(Ba0.7Ca0.3TiO3)–0.5(Ba(Zr0.2Ti0.8)O3)

17

Pirri, C. F. Effects of Nanoscale Confiment on Ferroelectric Properties: Research Activity at the Center for Space Human Robotics 48

Polcawich, R. PiezoMEMS Technology for Enabling mm-Scale Robotics 5

Remiens, D. Performances of Piezoelectric Nano Structures 10

Rijnders, G. All-oxide PiezoMEMS Devices by Pulsed Laser Deposition: Properties of Clamped Epitaxial PZT Thin Films 35

Rosenfeld, D. Manufacture of Minature Tuneable Autofocus Lenses (TLens) using Piezo MEMS 46

Sandu, C. Electromechanical properties of Al0.9Sc0.1N thin films evaluated at 2.2 GHz Film bulk acoustic resonators 15

Schreiter, M. Piezoelectric MEMS based energy harvesting module for wireless tire pressure monitoring 6

Thyholdt, F. FP7 piezoVolume - High Volume Piezoelectric Thin Film Production Process For Microsystems

45

Tiedke, S. Measurements of Electrical and Electromechanical Characteristics of Piezoelectric Thin Films and Optimization of Poling

39

Tiedke, S. Direct and Indirect Piezoelectric Characterization of PZT Thin Films for MEMS Applications 40

Trolier-McKinstry, S. Microcontact Printing of PZT Films for MEMS 18

Trolier-McKinstry, S. Low Temperature Laser Processing of Ferroelectric Thin Films 44

Verdot, T. Active Damping with a piezoelectric MEMS device 29

Vogl, A. Modelling of piezoelectric micromachined ultrasound transducers (pMUT) for medical use 30

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Vullers, R. AlN and PZT Thin Films: Essential Ingredients for Piezoelectric Energy Harvesters 7

Welsh, A. Microcontact Printing of PZT Films for MEMS 18

Conf Piezo Mems 2011

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