Implementation of a gap-closing differential capacitive sensing Z-axis accelerometer on an SOI wafer

Abstract

This study presents a novel capacitive-type Z-axis (out-of-plane) accelerometer implemented on an SOI wafer. This accelerometer contains special designed gap-closing differential sensing electrodes. The present Z-axis accelerometer has four merits: (1) mass of the proof mass is increased by combining both device and handle silicon layers of the SOI wafer, (2) the sensitivity is improved by the gap-closing differential electrodes design, (3) the electrical interconnection between the device and handle silicon layers of the SOI wafer is available by means of the metal-vias, and (4) the sensing gap thickness is precisely defined by the buried-oxide layer of the SOI wafer. In application, the Z-axis accelerometer is fabricated and characterized. Typical measurement results demonstrate that the presented Z-axis accelerometer has a sensitivity of 196.3 mV G-1 (42.5 fF G-1) and a maximum nonlinearity of 2% over the range of 0.1-1 G. © 2009 IOP Publishing Ltd.