Abstract
This thesis proposes wafer-level complementary metal oxide semiconductor (CMOS) micro-electro-mechanical systems (MEMS) processes whose steps are fully compatible with standard CMOS process and have the potential for mass production. A monolithic capacitive accelerometer is proposed by using the wafer-level CMOS MEMS process. The out-of-plane deflection resulted from the vertical stress gradient over the whole device is under 0.2 μm. The sensing circuit topology adopts switched capacitors for achieving a low power consumption and a low output offset voltage. With the sensing range of ±6 G, the sensitivity of the accelerometer is 191 mV/G, and the nonlinearity is 1.07 %. The measured output noise floor is 354 μG/Hz1/2. The measured output offset voltage is about 100 mV at 27 °C, and the zero-G temperature coefficient of the accelerometer output is 0.94 mV°C−1 below 85 °C. A monolithic capacitive CMOS MEMS resonator is also proposed in this thesis. The measured resonator frequency is 116 kHz with a quality factor of 332 at 1 atm. The quality factor is raised to 930 at 0.07 Torr with a DC bias of 60 V. A CMOS MEMS oscillator is implemented with gain and phase compensations using an off-chip op-amp in printed circuit board. The oscillation frequency is 116 kHz and the phase noise at a 1-kHz offset is -104 dBc/Hz. In addition, a high quality-factor CMOS MEMS inductor is also fabricated with the post-CMOS MEMS process, which shows an improvement of 88% comparing to a CMOS inductor. The CMOS MEMS inductor is implemented in a 5.8 GHz voltage controlled oscillator, which improves 5 dB in phase noise.