Influence of gold coating on design and performance of high-g SOI technology based MEMS inertial switch

Abstract

Abstract MEMS based inertial switches have important applications in defense, automobile, and aviation sectors. The materials for these inertial switches are either metals or low-resistivity silicon. This paper discussed about the amalgamation of metal and silicon in the MEMS inertial switch (500 g) structure to achieve high performance and high current handling capability. The switch structure, comprises of four series-parallel beam supported large proof-mass suspended over a gap of 4 µm. The resonant frequency of the switch structure is found to be 4.2 kHz. The dimensions of the switch structure are studied by parametric analysis. The transient response of the gold coated silicon MEMS inertial switch structure showed contact (on-state) duration of 230–380 µs due to the 10% variation in half-sine threshold acceleration value (500 g). The variation in acceleration input pulse width (0.25–1 ms) yielded a large variation in contact duration (2.5–370 µs). In response to two successive half-sine acceleration pulses, variation in contact duration is observed due to the superimposition of residual movement of the proof-mass arising due to first pulse with the response of the second acceleration pulse. The electro-thermal behaviour (under 1A current flow in the switch contact duration) of the gold coated (1.0 µm) switch structure showed a substantial reduction in temperature rise (due to Joule heating) from 413 K to 301 K. Thus, the gold coating on the silicon MEMS inertial switch lowered on-state resistance by one order and improved current handling capability due to less Joule heating issue.