Integrated 0–30 V switching driver circuit fabricated by mesa isolation postprocess of standard 5 V CMOS LSI for MEMS actuator applications

Abstract

A 30 V switching circuit with standard CMOS foundry-made transistors on a silicon-on-insulator (SOI) wafer is proposed.The key fabrication process is mesa isolation postprocessing that physically separates a series-connected transistor's body so that we can apply independent substrate (body) voltages to each transistor. The process is a combination of anisotropic and isotropic deep reactive ion etching (DRIE) with a single mask. In the experiment, CMOS transistors were fabricated on a 9-µm-thick 6-in. SOI wafer in an LSI foundry company, and the postprocess was carried out in a MEMS cleanroom. In this paper, full integration with gate-voltage-level shift circuits and dynamic driving of an electrostatic comb-drive MEMS device with series-connected transistors are presented.