A silicon-on-glass Z-axis accelerometer with vertical sensing comb capacitors

A Z-axis accelerometer with asymmetrical vertical sensing comb capacitors and high aspect ratio single crystal mechanical structures is presented. A 5-mask silicon-on-glass (SOG) process combined with silicon/glass anodic bonding and multiple deep ion reactive etching (DRIE) is used to fabricate the accelerometer. With the specially designed out-of-plane springs, the accelerometer shows a cross-axis sensitivity of 0.46%. The scale factor and the non-linearity of the accelerometer are measured to be 172.5 mV/g and 0.47% with the input range of ±1 g (gravity), respectively. The noise floor of the accelerometer is 0.22 mg/Hz1/2 at 100 Hz and for a bandwidth of 400 Hz. The short term (10 min) zero bias stability of the fabricated accelerometer is also evaluated to be about 0.47 mg.