Design and performance analysis of high-g MEMS switch with improved current handling capability

High performance micro-electro-mechanical system (MEMS) inertial switches (made of either metal or silicon) are in great demand for many niche applications. This paper discusses the design of high-g silicon-on-insulator (SOI) MEMS inertial switch structure with improved current handling capability. The switch structure, comprises of four series-parallel beams supported large proof-mass suspended over a 4 μm deep cavity. The switch structure exhibited in-plane (y-axis) fundamental displacement mode with resonant frequency of 4.2 kHz. The transient response of the 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 electromechanical pull-in study of the switch structure showed 155 V pull-in voltage. With the variation in silicon resistivity (0.05–0.005 Ω-cm), the on-state resistance of the switch goes down to 3.5 Ω. Corresponding temperature rise (Joule heating) due to the input current of 1A for the entire contact duration is found to be ∼190 °C. The device structure is coated with 1 μm thick gold layer to further reduce the temperature rise (<50 °C) and improved current handling capability. The fabricated switch exhibited an off-state resistance in GΩ, and ≤2.5 Ω on-state resistance.