High-Q CMOS MEMS resonator oscillator fabricated in a MPW batch process

Abstract This paper describes the design and characterization of a MEMS resonator oscillator fabricated in a 0.35-μm CMOS MEMS multi-project wafer (MPW) process. The polysilicon in CMOS is partially embedded in the microstructure to reduce the curl within less than 100 nm. The measured resonance frequency of the resonator is 116.1 kHz with a quality factor of 332 at 1 atm. The quality factor is raised to 930 under 0.07 torr and a dc-bias of 20V. The quality factor is further enhanced by placing the resonator in a self-oscillation positive feedback loop. The phase noise of the oscillator is −104 dBc/Hz at a 1-kHz offset and the equivalent quality factor is more than 120,000. Ten chips arbitrarily selected from the corners and center of the MPW are measured with resonant frequencies ranging from 115.9 to 116.2 kHz.