Single-mask fabrication of high-G piezoresistive accelerometers with extended temperature range

This paper presents a fabrication process in which all components of an in-plane piezoresistive accelerometer are fabricated simultaneously using a single mask. By dry-etching a silicon-on-insulator (SOI) wafer that has a specific resistivity, piezoresistors are defined and isolated from each other and from the bulk silicon without the pn-junctions normally required in piezoresistive sensors. In addition to simplifying the fabrication, the temperature range is also extended when compared to conventional piezoresistive accelerometers, due to the absence of pn-junctions. Single-axis accelerometers, designed for an acceleration range of 1 G to 500 G with a sensitivity of 1 mV G−1, were fabricated and tested, and linear output characteristics were demonstrated. The temperature performance was also characterized. The temperature coefficient of sensitivity (TCS) was 0.3% ◦C−1 and the temperature coefficient of offset (TCO) was 20 mG ◦C−1. (Some figures in this article are in colour only in the electronic version)