Electronic Materials and Applications€¦ · • High throughput (combinatorial) materials science methodology is a relatively new research paradigm that has enabled rapid and efficient
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Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Electronic Materials and Applications
Martin L. Green, NIST
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Computing Power Has Increased By A Factor of 107 Since 1970
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
The cost of developing new materials, and the time for commercializing them can both be decreased through simulation and modeling, which are less expensive and faster than experimentation
The Materials Genome Initiative
A large portion of the MGI program thus far has been devoted to modeling, simulation, and curation of data
High throughput (combinatorial) experimentation is the counterpart to the concerted computational materials design efforts being carried out under MGI
Such experimentation will realize the MGI approach by:
Enabling rapid experimental verification of models and simulations, iteratively improving them
Generating the data needed to power the MGI “engine” and thereby enable new models
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Combinatorial Materials Science • High throughput (combinatorial) materials science methodology is
a relatively new research paradigm that has enabled rapid and efficient materials discovery, screening, and optimization
• MGI will be an important driver of high throughput methodologies for ongoing materials innovations in substitutes for critical materials, functional materials, energy-related materials, catalysts, materials discovery, etc. • Major challenges: – Expense and availability of high throughput facilities – Novel high throughput metrologies (fast and local) will be
needed – Real time data collection and analysis – Managing large amounts of data in a variety of formats – Better materials informatics
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Why Now?: e.g., Increasing Complexity of Si Technology
Courtesy of Intel Corp.
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
The Advanced Gate Stack
Source
Silicon substrate
Gate Metal Electrode
Drain
Lc
Wc
High-κ Gate Dielectric
HfO2, Hf-O-N, Hf-Si-O, higher-κ…..
Metals, alloys, nitrides, silicides…..
Thermal and electrical stability of
the interfaces
2005 ITRS: ...The crux of this problem comes from the fact that the traditional transistor…materials, silicon, silicon dioxide, and polysilicon have been pushed to fundamental material limits and continued scaling has required the introduction of new materials.
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
HT Work Flow and Equipment Needs • Library synthesis tool (usually specific to a
few classes of materials) ($1.0M) • Basic characterization tools (composition,
structure) (generic to many classes of materials) ($1.5M)
• HT metrology (usually specific to one or two classes of materials) ($0.2M)
• Data analysis/informatics capability (generic to many classes of materials) ($0.2M)
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
• When I first visited Sematech in 2004, they had not heard of combinatorial materials science
• Found about 40 references • Lots of proprietary research
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Silicon substrate
Gate Metal
Drain
Lc
Wc
High-κ gate dielectric
HfO2, ZrO2, Y2O3, Al2O3, silicates, aluminates, ...
nitrides, alloys, silicides…..
Candidates:
Candidates:
Thermal and electrical stability of the interfaces
Source
Metal-oxide-semiconductor field effect transistor (MOSFET) Motivation – Gate Metal Electrode
Challenge: For novel gate metal electrodes, need to know work function
Problem: Many candidates for gate metal electrode; not feasible to look at them all on a one-at-a-time basis
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Strategy Ta1-xAlxNy/HfO2/Si gate stack
Ta1-xAlxNy library film
50 nm
p-Si
HfO2 (3 nm)
SiO2 (4, 5, 6, or10 nm)
Side View
Identical Ta1-xAlxNy composition spreads were deposited on four different thickness of dielectric layers using a shadow mask. These four libraries allow us to systematically extract work functions.
Vfb vs. EOT is used to extract Φm
We use an automated probe to measure capacitance – voltage (C-V) characteristics of hundreds of MOS capacitors for each library.
Over 2000 MOS capacitors are measured.
TaNy
AlNy
Top View
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Capacitors: Ta1-xAlxNy Library
100 µm
Each capacitor has a different metal gate
composition
Chang et al, IEEE TRANS. ELECT. DEV., VOL. 55, NO. 10, 2008
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
TaN Ta1-xAlxN
4.4
4.5
4.6
4.7
4.8
4.9
5
5.1
5.2
5.3
0 10 20 30 40 50 60 Composition (x)
Wor
k fu
ncti
on (
eV)
HfO2(3nm)+SiO2(4, 5, 6, 10nm)
HfO2(3nm)+SiO2(4, 5, 6, 10nm) 900°C, 5s, Ar
Extracted Work Functions from the Ta1-xAlxN Library
Alshareef et al, APL, 88, 072108 2006
• Represents two years effort for a postdoc • Many other projects can go on simultaneously • Almost all tools are multi-use
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Thermoelectric materials can generate an electrical potential from a thermal gradient, and vice-versa.
• The Seebeck Effect: The conversion of a temperature differential directly into electricity.
S = Seebeck coefficient = - ∆V/∆T
Major Application: Vehicular waste heat recovery
• The Peltier Effect: When a current flows through the junction of dissimilar materials, heat will either be absorbed or evolved depending on the direction of current flow.
Q = Heat current = Π x I (Π = Peltier coefficient, I = electrical current) Major Application: Solid-state refrigeration
• ZT is the figure of merit of thermoelectric
materials performance • Good candidate thermoelectric materials
exhibit high electrical conductivity and low thermal conductivity (unfortunately in most materials they are correlated)
0 T
C PPMS
Screening tool
Thermoelectric Materials
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Pulsed laser deposition growth of a ternary thermoelectric material
library
(Ca2Sr)Co4O9
Ca3Co4O9 (Ca2La)Co4O9
Si(100) substrate
Thermoelectric System (Ca-Sr-La)3Co4O9
Otani et al, APL 91, 132102 (2007)
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Thermoelectric Materials
M. Otani et al., APL 2007
Comparison of Seebeck coefficients
measured by scanning tool and
commercial (single measurement) tool
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Material Measurement Laboratory
Phase Transformation in VO2
Tetragonal (Rutile), IR reflective Monoclinic, IR transparent
Eyert, Ann.Phys. 2002 Dimerization.
T = 68°C
e- density, c-axis compressive stress
To depress transformation temperature by impurity atoms:
increased e-density, dope with larger atoms.
For W impurities: 20°C/at.%
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Material Measurement Laboratory
Thermochromic ‘Smart’ Windows
win
dow
: co
ld d
ay
win
dow
: ho
t da
y
outd
oors
indo
ors
outd
oors
indo
ors
At T < Tc, solar heating desirable, and window is VIS/NIR transparent.
At T > Tc, window is VIS transparent and NIR reflective.
VIS
NIR VIS/NIR
VIS/NIR
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
Material Measurement Laboratory
High Throughput Reflectometry
Thermochromic phase transition in V1-xNbxO2 Monoclinic Tetragonal
Measure NIR reflectance at many temperatures and locations (compositions)
35 temperatures X 165 locations
= 5775 spectra in 20 hours
x = 0.014
Combinatorial Approaches to Functional Materials 5/5-6/2014 M. L. Green
High Throughput Combinatorial Library Analysis: V-W-Nb-O
Combinatorial Thin Film Library
X-ray diffraction
Material Property Characterization: Thermochromism in VO2 region
Manual Analysis
High Speed Clustering Analysis
-20 0 20
-20
0
20
Structure-Property Relationship
VO2
WOx NbOx
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