Ischia, 21-23 giugno 2006Riunione Annuale GE 2006 Integrated Optical Microsensors Based On Porous Silicon Technology For Vapours And Liquids Identification.

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Integrated Optical Microsensors Integrated Optical Microsensors

Based On Porous Silicon Based On Porous Silicon

Technology For Vapours And Technology For Vapours And

Liquids IdentificationLiquids IdentificationL. Rotiroti, I. Rea, D. Alfieri, I. Rendina and L. De Stefano

Institute for Microelectronic and Microsystem – Dept. of Naples,National Council of Research, Naples, Italy

L. Moretti, F.G. Della CorteDIMET – “Mediterranea” University of Reggio Calabria,

Reggio Calabria, Italy


• …is a low-cost material and fabrication process;

• …has a large specific surface area (~ 200 m2/cm3);

• …rapidly and effectively interacts with chemical species;

• …shows evident changes in several physical properties usable for sensing (reflectivity, photoluminescence, electrical conductivity, optical waveguiding...);

• …easy to integrate in hybrid systems (MEMS, MOEMS, TAS, Labo-on-Chip etc...);

• ...compatible with microelectronic technologies;

• …its surface can be chemically modified to enhance analyte selectivity.

The transducer element: PSiThe transducer element: PSi

Si p+ type

DBR # 1

DBR # 2

8.3 m

600 800 1000 1200 1400 1600

0.2

0.4

0.6

0.8

1.0

Re

flect

ivity

(a

.u)

Wavelength (nm)

monolayer

800 1000 1200 1400

0.0

0.5

1.0

1.5

2.0 microcavità ottica

Ref

lect

ivity

(a.

u)

Wavelength (nm)


PSi Layer

Carrier out

Carrier in

Analyte

Pneumatic actuator

A step furtherA step further


Silicon-glass anodic bondingSilicon-glass anodic bonding

Anodic Bonding is a bonding process of a silicon wafer to glass under the influence of high temperature and an externally applied electric field

@ 200°CElectric Field 2500 V

Planar ElectrodeBonding time 5 min


Flow Injection AnalysisFlow Injection Analysis


Experimental results-1Experimental results-1

-chamber volume: 4 -chamber volume: 4 llPSi layer thickness: 2 PSi layer thickness: 2 mm

0.0 0.5 1.0 1.5 2.0 2.50.0

0.2

0.4

0.6

0.8

1.0

1.2 Carrier burst PSi signal

Tresp

= 156 ms

Trec

= 24 ms

On exposure to Isopropanol

Re

fle

cti

vit

y (

a.u

.)

Time (sec)

-chamber volume: 12 -chamber volume: 12 llPSi layer thickness: 6 PSi layer thickness: 6 mm

0 2 4 6 8 100.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

Re

fle

cti

vit

y (

a.u

.)

Time (s)

Carrier burst PSi signal

Response time = 450 ms


VOC Isopropanol Ethanol Methanol

Response time

156 ms 104 ms 64 ms

Recovery time

24 ms 55 ms 48 ms

Experimental results-2Experimental results-2

Comparison between response times due to different substances.

All the measurements have been made in saturated atmosphere


The second device schemeThe second device scheme

The planar waveguide is realised by thermal oxidation of a SOI wafer, in a dry atmosphere at 1050 °C: a thin silicon oxide layer of 100 nm confines the light into a 3 μm thick crystalline silicon layer. The transduction element of this sensing device is fabricated by a two-step electrochemical etching process of a <100> silicon wafer, p+ type, with a resistivity of 8-12 mΩcm, using an HF/EtOH (50:50) solution. The elements are joined together by AB technique.


Experimental set-up and resultsExperimental set-up and results

An infrared laser (=1550nm) is coupled into the SOI waveguide through an optical fiber. The trasmission beam is collected by another optical fiber and directed in a photodiode.

0 50 100 150 200 250 3001.0

1.5

2.0

2.5

3.0

3.5

Inte

ns

ity

(m

V)

Time (sec)


Thank you for your Thank you for your attentionattention!!

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006 Integrated Optical Microsensors Based On Porous Silicon Technology For Vapours And Liquids Identification.

Documents

riunione annuale ge

silicon wafer

saturated atmosphere

silicon oxide layer

chamber volume

psi layer carrier

psi layer thickness

bonding process