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Wafer-level mechanical characterization of silicon nitride MEMS

2005; Institute of Electrical and Electronics Engineers; Volume: 14; Issue: 2 Linguagem: Inglês

10.1109/jmems.2004.839315

1941-0158

Ajeet Kaushik, H. Kahn, A. H. Heuer,

Mechanical and Optical Resonators

The mechanical and physical properties of silicon nitride thin films have been characterized, particularly for their application in load-bearing MEMS applications. Both stoichiometric (high-stress) and silicon-rich (low-stress) films deposited by LPCVD have been studied. Young's modulus, E, has been determined using conventional lateral resonators and by bulge testing of membranes, and tensile strength has been determined using a specially designed microtensile specimen. All microdevices have been fabricated using standard micromachining. We have also measured the thermal expansion coefficient of stoichiometric silicon nitride. Our best estimate of E is 325/spl plusmn/30 GPa for stoichiometric and 295/spl plusmn/30 GPa for silicon-rich silicon nitride. The average tensile strength for the stoichiometric material is 6.4/spl plusmn/0.6 GPa, while that for the silicon-rich material is 5.5/spl plusmn/0.8 GPa; the burst strength of membranes of the stoichiometric material is 7.1/spl plusmn/0.2 GPa.