A study on process-compatibility in CMOS-first MEMS-last integration

We report monolithic integration of MEMS (micro electro mechanical systems)actuators and high-voltage driver circuits into a silicon chip. Driver circuits of up to 40 V were prepared on an 8-mum thick SOI (silicon-on-insulator) wafer by the DMOS (double-diffused metal oxide semiconductor) processes, after which MEMS electrostatic actuators were integrated into the identical SOI layer by post-processing using DRIE (deep reactive ion etching). This technique opens up a new way of high-voltage ASIC (application specific integrated circuit)for MEMS designer. We investigated the process compatibility between the integrated circuits and MEMS. Studies are made on (1) the design and fabrication of the MEMS-circuit electrical interconnection and (2) the effect of dry-etching plasma on the circuit characteristics in MEMS DRIE process.