Process-Induced Stress and Hydrogen Effects on Monolithic Integrated CMOS-MEMS Micro-Bimaterial Cantilever Sensor Array

A monolithic integrated bimaterial micro-cantilever resonant infrared sensor with on-chip auxiliary circuits was fabricated and tested. Surface micromachining method for cantilever fabrication has been merged with conventional CMOS process, and release of MEMS structure is conducted after CMOS process. Both the Cr/Au felling off the polysilicon cantilever during releasing process and the performance degradation of MOSFETs manufactured by standard CMOS or post-CMOS process are ascribed to the additive effects of hydrogen and mechanical stress. A novel post-CMOS process was raised to decrease the mechanical stress and to retain the metal layer of Cr/Au. On-chip digital/analog Bi-CMOS circuits function properly as demonstrated.