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Title: Reliability Testing of Polysilicon For MEMs Devices

Abstract

Mission critical applications of MEMS devices require knowledge of the distribution in their material properties and long-term reliability of the small-scale structures. This project reports on a new testing program at Sandia to quantify the strength distribution using samples that reflect the dimensions of critical MEMS components. The strength of polysilicon fabricated with Sandia's SUMMiT 4-layer process was successfully measured using samples with gage sections 2.5 {micro}m thick by 1.7 {micro}m wide and lengths of 15 and 25 {micro}m. These tensile specimens have a freely moving pivot on one end that anchors the sample to the silicon die and prevents off axis loading during testing. Each sample is loaded in uniaxial tension by pulling laterally with a flat tipped diamond in a computer-controlled Nanoindenter. The stress-strain curve is calculated using the specimen cross section and gage length dimensions verified by measuring against a standard in the SEM. The first 48 samples had a means strength of 2.24 {+-} 0.35 GPa. Fracture strength measurements grouped into three strength levels, which matched three failure modes observed in post mortem examinations. The seven samples in the highest strength group failed in the gage section (strength of 2.77 {+-} 0.04 GPa), the moderate strengthmore » group failed at the gage section fillet and the lowest strength group failed at a dimple in the hub. With this technique, multiple tests can be programmed at one time and performed without operator assistance at a rate of 20-30 per day allowing the collection of significant populations of data. Since the new test geometry has been proven, the project is moving to test the distributions seen from real geometric features typical to MEMS such as the effect of gage length, fracture toughness, bonding between layers, etch holes, dimples and shear of gear teeth.« less

Authors:
;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
5689
Report Number(s):
SAND99-0810C
TRN: AH200115%%96
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Micro/Nanotechnology for Space Applications, Pasadena, CA (US), 04/11/1999--04/15/1999; Other Information: PBD: 5 Apr 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; FRACTURE PROPERTIES; RELIABILITY; MATERIALS TESTING; SILICON; POLYCRYSTALS; MINIATURIZATION; TENSILE PROPERTIES; MICROELECTRONICS

Citation Formats

LaVan, D A, and Buchheit, T E. Reliability Testing of Polysilicon For MEMs Devices. United States: N. p., 1999. Web.
LaVan, D A, & Buchheit, T E. Reliability Testing of Polysilicon For MEMs Devices. United States.
LaVan, D A, and Buchheit, T E. Mon . "Reliability Testing of Polysilicon For MEMs Devices". United States. https://www.osti.gov/servlets/purl/5689.
@article{osti_5689,
title = {Reliability Testing of Polysilicon For MEMs Devices},
author = {LaVan, D A and Buchheit, T E},
abstractNote = {Mission critical applications of MEMS devices require knowledge of the distribution in their material properties and long-term reliability of the small-scale structures. This project reports on a new testing program at Sandia to quantify the strength distribution using samples that reflect the dimensions of critical MEMS components. The strength of polysilicon fabricated with Sandia's SUMMiT 4-layer process was successfully measured using samples with gage sections 2.5 {micro}m thick by 1.7 {micro}m wide and lengths of 15 and 25 {micro}m. These tensile specimens have a freely moving pivot on one end that anchors the sample to the silicon die and prevents off axis loading during testing. Each sample is loaded in uniaxial tension by pulling laterally with a flat tipped diamond in a computer-controlled Nanoindenter. The stress-strain curve is calculated using the specimen cross section and gage length dimensions verified by measuring against a standard in the SEM. The first 48 samples had a means strength of 2.24 {+-} 0.35 GPa. Fracture strength measurements grouped into three strength levels, which matched three failure modes observed in post mortem examinations. The seven samples in the highest strength group failed in the gage section (strength of 2.77 {+-} 0.04 GPa), the moderate strength group failed at the gage section fillet and the lowest strength group failed at a dimple in the hub. With this technique, multiple tests can be programmed at one time and performed without operator assistance at a rate of 20-30 per day allowing the collection of significant populations of data. Since the new test geometry has been proven, the project is moving to test the distributions seen from real geometric features typical to MEMS such as the effect of gage length, fracture toughness, bonding between layers, etch holes, dimples and shear of gear teeth.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {4}
}

Conference:
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