Dynamic MEMS devices for multiaxial fatigue and elastic modulus measurement

Carolyn D. White; Rui Xu; Xiaotian Sun; Kyriakos Komvopoulos

doi:10.1117/12.476332

16 January 2003 Dynamic MEMS devices for multi-axial fatigue and elastic modulus measurement

Carolyn D. White, Rui Xu, Xiaotian Sun, Kyriakos Komvopoulos

Proceedings Volume 4980, Reliability, Testing, and Characterization of MEMS/MOEMS II; (2003) https://doi.org/10.1117/12.476332
Event: Micromachining and Microfabrication, 2003, San Jose, CA, United States

Abstract

For reliable MEMS device fabrication and operation, there is a continued demand for precise characterization of materials at the micron scale. This paper presents a novel material characterization device for fatigue lifetime testing. The fatigue specimen is subjected to multi-axial loading, which is typical of most MEMS devices. Polycrystalline silicon (polysilicon) fatigue devices were fabricated using the MUMPS process with a three layer mask process ground plane, anchor, and structural layer of polysilicon. A fatigue device consists of two or three beams, attached to a rotating ring and anchored to the substrate on each end. In order to generate a sufficiently large stress, the fatigue devices were tested in resonance to produce a von Mises equivalent stress as high as 1 GPa, which is in the fracture strength range reported for polysilicon. A further increase of the stress in the beam specimens was obtained by introducing a notch with a focused ion beam. The notch resulted into a stress concentration factor of about 3.8, thereby producing maximum von Mises equivalent stress in the range of 1 through 4 GPa. This study provides insight into multi-axial fatigue testing under typical MEMS conditions and additional information about micron-scale polysilicon mechanical behavior, which is the current basic building material for MEMS devices.

Citation Download Citation

Carolyn D. White, Rui Xu, Xiaotian Sun, and Kyriakos Komvopoulos "Dynamic MEMS devices for multi-axial fatigue and elastic modulus measurement", Proc. SPIE 4980, Reliability, Testing, and Characterization of MEMS/MOEMS II, (16 January 2003); https://doi.org/10.1117/12.476332

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