CMOS-MEMS accelerometer with differential LC-tank oscillators

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 μm 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 external acceleration. The device has been characterized and has a mechanical resonance frequency of 3.3 kHz, sensitivity of 3.7 MHz/g, and nonlinearity of 1.8%.