TITLE:
Porous Silicon as Soft Material in Low-Frequency MEMS (MicroElectro-Mechanical Systems) Resonators
AUTHORS:
C. Malhaire, A. Danescu, V. Lysenko, A. Sabac
KEYWORDS:
Porous Silicon, Cantilever, Resonator
JOURNAL NAME:
World Journal of Mechanics,
Vol.8 No.11,
November
7,
2018
ABSTRACT: This study focuses on the mechanical response of silicon on porous silicon bilayer cantilevers ended with a seismic mass. The porous silicon is intended to provide an alternative to decrease the cantilever stiffness for low-frequency MEMS applications. The first eigenfrequency of the cantilever is obtained using static deflection obtained under classical Euler-Bernoulli assumptions and Rayleigh method. In order to estimate the errors due to small-strain approximation and Euler-Bernoulli theory, the analytical results were validated through 3D finite element simulations for different cantilever geometries and porosities. Both bulk silicon and silicon on porous silicon bilayer cantilevers ended with a seismic mass were fabricated and we measured the first eigenfrequency (f0) and quality factor (Q) by using a laser Doppler vibrometer. In agreement with the theoretical predictions we found that, when compared to bulk silicon cantilevers, the first eigenfrequency of a bilayer cantilever containing 6% porous silicon (at 50% porosity) on 94% bulk silicon is lowered by 5%, from (5447 ± 120) Hz to ≈ 5198 Hz. This decrease is also accompanied by a reduction of the quality factor by two.