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/Hz^1/2 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.

I. Introduction

For the last decades, the demands on MEMS inertial sensors have grown rapidly for the application on consumer electronics, automotive electronics and so on [1]–[3]. Among the reported inertial sensors, differential sensing accelerometers especially with differential sensing comb attracted widely attentions with the advantages of high sensitivity and high reliability [4]–[5] while many differential sensing mechanisms of Z-axis accelerometers had been developed. References [2]–[3] reported gap closing differential sensing electrodes, and reference [6] realized the differential sensing by rotational displacement detection, while asymmetrical vertical comb sensing were reported by [5],[7].