Development and Characterization of a CMOS-MEMS Accelerometer With Differential LC-Tank Oscillators

Abstract

This paper presents a CMOS-MEMS accelerometer based on differential LC-tank oscillators. Two LC-tank oscillators composed of differential MEMS capacitors and suspended inductors were designed and fabricated by standard TSMC 0.18 mu m CMOS processes and post-CMOS dry etching. The outputs of the differential oscillators are mixed and the output frequency of the mixer is proportional to the capacitance change caused by the external acceleration. The device has been characterized and has a mechanical resonance frequency of 7 kHz, absolute sensitivity of 3.62 MHz/g, relative sensitivity of 1.9 x 10(-3) Delta f/f(0)/g, in-axis nonlinearity of 1.2 % FS, bias stability of 2.1 mg, and average noise floor of 0.205-0.219 mg/root Hz Hz in the frequency range of 15-250 Hz.