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Mechanical Properties and Reliability of Amorphous vs. Polycrystalline Silicon Thin Films

Published online by Cambridge University Press:  01 February 2011

Joao Gaspar ,
Oliver Paul ,
Virginia Chu  and
Joao Pedro Conde
Joao Gaspar
Affiliation:
[email protected], University of Freiburg, Department of Microsystems Engineering (IMTEK), Microsystems Materials Laboratory, Georges-Koehler-Allee 103, Freiburg, 79110, Germany, +497612037194, +497612037192
Oliver Paul
Affiliation:
[email protected], University of Freiburg, Dept. Microsystems Eng. (IMTEK), Freiburg, 79110, Germany
Virginia Chu
Affiliation:
[email protected], INESC Microsistemas e Nanotecnologias, Lisbon, 1000-029, Portugal
Joao Pedro Conde
Affiliation:
[email protected], INESC Microsistemas e Nanotecnologias, Lisbon, 1000-029, Portugal
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Abstract

This paper presents the mechanical characterization of both elastic and fracture properties of thin silicon films from the load-deflection response of membranes, also known as the bulge test. Properties extracted include the plane-strain modulus, prestress, fracture strength and Weibull modulus. Diaphragms made of low-temperature, hydrogenated amorphous and nanocrystalline silicon films (a-Si:H and nc-Si:H, respectively) deposited by plasma enhanced chemical vapor deposition (PECVD) and, for comparison, membranes composed of high-temperature polycrystalline silicon (poly-Si) deposited by low pressure chemical vapor deposition (LPCVD) have been fabricated and characterized. The structures are bulged until failure occurs. From the stress profiles in the diaphragms at fracture, the brittle material strength is analyzed using Weibull statistics. The bulge setup is fully automated for the sequential measurement of several membranes on a substrate realizing the high-throughput acquisition of data under well controlled conditions. A comprehensive study of the mechanical properties of low-temperature silicon films as a function of deposition parameters, namely substrate temperature, RF power, hydrogen dilution and doping, is presented.

Keywords

thin filmmicroelectro-mechanical (MEMS)elastic properties
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1066: Symposium A – Amorphous and Polycrystalline Thin-Film Silicon Science and Technology—2008 , 2008 , 1066-A15-04
Copyright
Copyright © Materials Research Society 2008

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References

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