Squeeze film air damping analysis of MEMS piezoresistive accelerometer

In this paper, squeeze film damping analysis of silicon piezoresistive accelerometer is reported. The accelerometer is a bulk micromachined device fabricated using CMOS compatible dual-dope TMAH. The device is realized in a three layer glass/silicon/glass bonded structure, with cavities of uniform depth (~30 mum) on both glasses to provide space for the damping medium. Air is used as damping medium, which has less temperature effect on the viscosity and has low density than those of oil. Simplified electrical equivalent model for the squeeze film air damping of the device has been derived. Experimental results of the accelerometer for the dynamic response also have been presented. It is observed that for the air damping there is not much variation in the resonance frequency and device is critically damped.