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

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 channel PMOSFETs is larger than that in the 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.