A low-voltage tunneling-based silicon microaccelerometer

This paper describes the design, fabrication, and testing of a low-voltage tunneling-based silicon microaccelerometer. The device has been successfully batch-fabricated by the boron etch-stop dissolved wafer process. A 4 h, 1100°C oxygen, post-diffusion annealing process has been developed to eliminate the stress gradient in and warpage of thin (≈3 μm) heavily-boron-doped silicon microstructures. Using a simple discrete readout circuit, the device with an active area of 400×400 μm² provides a measured sensitivity of 1.66×10⁴ ppm/g (133 mV/g), bandwidth of 2 kHz in air, and a full scale range of 30 g with a nonlinearity of 0.6%. The measured noise spectrum exhibits a typical 1/f behavior and drops from 1.75 mg/√Hz (at 50 Hz) to 0.25 mg/√Hz (at 2 kHz), corresponding to a minimum detectable acceleration of 22.8 mg. The variations of the offset output voltage and device sensitivity are ±40 mV (≈0.5%) and ±0.65 mV/g (≈0.49%) in continuous operation over thirty days. The temperature coefficient of offset (TCO) and temperature coefficient of sensitivity (TCS) are -600 ppm/°C and 1200 ppm/°C, respectively