Combinatorial Measurement 

Methods for Inorganic Materials

CERAMICS

Our goal is to develop novel, combinatorially-compatible measurement 

methods and metrologies, as well as comprehensive and consistent 

data sets, that will enable manufacturers of devices based on inorganic 

functional materials to select new materials more rapidly and intelligently. 

For example, the silicon microelectronics industry is currently materialslimited; the traditional transistor and capacitor formation materials 

— silicon, silicon dioxide, and polysilicon — have been pushed to their 

fundamental material limits, and continued scaling will require the 

introduction of novel materials.

Objective

Impact and Customers

• The silicon (Si) microelectronics industry and the consumer electronics and information revolution that it fuels is, at 

$750 billion, one of the largest sectors of the U.S. (and global) economy. The development of materials with superior 

properties that will enable device scaling (dimensional shrinkage of integrated circuit device elements according to 

Moore’s Law) and enhanced device performance is critical to continued innovation in Si microelectronics. 

• Currently, there are no rapid measurement techniques to determine the critical properties of novel functional materials, 

e.g., the work functions of metal gate electrodes for metal-oxide-semiconductor-field-effect-transistor (MOSFET) 

devices, or the Seebeck coefficients of thermoelectric 

materials for vehicular waste heat recovery devices. 

Development of such methods would enable more 

rapid selection, optimization, and commercialization of 

systems incorporating these devices.

• Key customers include Sematech and major U.S. 

semiconductor manufacturers such as Intel and Micron, 

as well as GM and Honda for the use of thermoelectrics 

for vehicular waste heat recovery applications. We 

are very active in promoting the use of combinatorial 

methodologies with our customers.

Approach

Materials Science and Engineering Laboratory

Our approach is to develop a novel metrology for interrogating the property 

of interest in the combinatorial library film. A good example of the application 

of this approach is the advanced gate stack of the integrated circuit MOSFET 

device. The traditional gate stack layers (SiO2 gate dielectric and polycrystalline 

Si gate electrode) in current Si microelectronic devices must be replaced with 

a high dielectric constant (high-k) gate dielectric, and a metal gate electrode. 

We will develop combinatorial methodologies to: (1) fabricate compositionally 

graded thin film libraries of novel gate metal electrode/high-k gate dielectric/

substrate combinations (“gate stack” structures); and (2) measure the key 

electronic properties (e.g., work function) and thermal stability of such libraries. 

Comprehensive data sets of electronic properties as a function of composition 

will be generated for materials systems identified as high priority by the microelectronics industry. In addition, firstprinciples modeling techniques will be used to predict the electronic properties of such systems.

Source

Silicon

substrate

Gate

electrode

Gate 

dielectric

Source Drain

Silicon

substrate

Gate

electrode

Gate 

dielectric

Drain

852-04-41b
Materials Science and Engineering Laboratory

We commissioned a state-of-the-art 

combinatorial tool capable of producing 

thin film libraries by reactive sputtering 

or pulsed laser deposition (PLD). Both 

chambers are equipped with multiple 

targets, allowing for the deposition of 

ternary films of metals and nitrides (by 

sputtering) and oxides (by PLD) with 

monolayer (0.5 nm) thickness control. At 

present, this tool produces library films for 

our thermoelectric materials and advanced 

MOS gate stack materials projects.

Thermoelectric materials have a major 

application for vehicular waste heat recovery, 

which could result in a 10% improvement in 

fuel efficiency, as well as a decrease in CO2

emissions. There is currently no screening 

tool to measure the Power Factor (equal 

to the square of the Seebeck coefficient 

multiplied by the electrical conductivity), an 

important indicator of energy conversion 

efficiency of thermoelectric thin films. If 

applied to combinatorial thin film libraries, 

it would accelerate material selection 

and optimization. In the example shown, 

the power factor is plotted as a function 

of composition for La and Sr substituted 

Ca3Co4O9 thermoelectric materials. Several 

hundred data points were automatically 

probed on this library film in about 2 hours. 

It can be seen that the power factor “sweet 

spot” is approximately at the composition 

(Ca2Sr0.7La0.3)Co4O9.

Another driver for our combinatorial 

project is the MOS gate stack (gate 

dielectric and gate metal electrode), which 

must be replaced by advanced materials if 

scaling is to continue. The microelectronics 

industry has identified HfO2, among other 

high-k gate dielectrics, as the leading 

candidate replacement materials for the 

SiO2 gate dielectric. However, dielectrics 

with dielectric constants even greater than 

HfO2 (k = 20), i.e., between the range of 

50 and 100, are now needed. We have 

investigated the HfO2-TiO2-Y2O3 ternary 

oxide system, and determined that there 

are many compositions with dielectric 

constants between 50 and 100, notably 

TiO2-rich oxides containing about 30% 

Y2O3 and 15% HfO2.

We have also studied the other gate 

stack layer, the gate metal electrode. The 

selection of gate electrode materials to 

replace polysilcon is not as far along as 

for the gate dielectric case. Recently, we 

have focused our efforts on gate electrode 

materials, specifically metalloids such 

as the Ta-C-N ternary system. We have 

developed high throughput, automated 

methods to measure current-voltage 

(I-V) and capacitance-voltage (C-V) 

properties of gate stack structures. From 

these measurements, the work function 

(fm) and leakage current density (JL

) can 

be determined. Shadow masks are used 

during thin film deposition, so etching is 

not needed to produce capacitor pillars. 

Each capacitor is individually addressable; 

the properties of 700 capacitors can be 

measured in about 5 hours. Our work 

function results on the Ta-C-N system 

are the first reported comprehensive 

measurements of the dependence of work 

function on composition for this metalloid 

system deposited on high-k dielectrics.

Accomplishments

Kao-Shuo Chang

Eric Cockayne

Peter Schenck

Martin Green

(Ceramics Division)

(301) 975-8496

martin.green@nist.gov

www.nist.gov/ceramics

Learn More Publications

Chang K-S, Green ML, Hattrick-Simpers J, Suehle J, Takeuchi I, Celik O and DeGendt S 

Determination of Work Functions in the Ta1-xAl xNy/HfO2 Advanced Gate Stack Using Combinatorial 

Methodology IEEE Trans. Electron Devices, 55: 2641 (2008)

Schenck PK, Klamo JL, Bassim ND, Burke PG, Gerbig YB and Green ML Combinatorial Study of the 

Crystallinity Boundary in the HfO2–TiO2–Y2O3 System Using Pulsed Laser Deposition Library Thin 

Films Thin Solid Films, 517: 691 (2008)

Otani M, Lowhorn ND, Schenck PK, Wong-Ng W, Green ML, Itaka K and Koinuma H A Highthroughput Thermoelectric Power-Factor Screening Tool for Rapid Construction of Thermoelectric 

Property Diagrams Applied Physics Letters, 91: 132102 (2007)

Combinatorial thin film tool

Power factor of La and Sr substituted Ca3Co4O9

thermoelectric materials

Work function as a function of position 

(i.e., composition) on a Ta-C-N library film

Dielectric constants of HfO2-TiO2-Y2O3 alloys