(Invited) Development of CMOS-MEMS Cointegrated Pressure Sensor Using Minimal Fab Process

Abstract

PVD-TiN metal gate PMOSFETs and CMOS ring oscillators have successfully been fabricated on circular diaphragms using the developed Minimal Fab CMOS-MEMS cointegrated gate-last process, and their electrical characteristics have systematically been investigated by changing applied pressures to the diaphragms. It was found that the drain current variation (dId) in the <110> channel PMOSFETs is larger than that in the <100> channel ones. The origin of dId is the mechanical stress-induced mobility change. It was also confirmed that the oscillation frequency of the fabricated CMOS ring oscillator on a circular diaphragm changes from 372 to 405 kHz at different pressures of -30 and +30 kPa. This result implies that the fabricated CMOS-MEMS cointegrated sensor chip is operated as a pressure sensor. The developed CMOS-MEMS cointegrated pressure sensor is suitable for the application to the battery drive IoT sensor systems because the all CMOS integration of the sensor has a low-power consumption.