A MicroPirani Pressure Sensor Based on the Tungsten Microhotplate in a Standard CMOS Process

This paper reports a tungsten microhotplate fabricated in a standard CMOS process and the implementation of a MicroPirani pressure sensor with it. A monolithic constant-current circuit including an operational amplifier is used to bias the tungsten microhotplate to measure the gas pressure. The sensor shows a linear response to the gas pressure in the range of 1-100 Pa when driven by a constant current of 7 mA. In this regime, the sensitivity of the sensor is 0.23 mV/Pa, the linearity is 4.95%, and the hysteresis is 8.69%. The MicroPirani pressure sensor in this paper can be used in a medium-vacuum measurement. Because tungsten in a standard CMOS process has a large temperature coefficient regardless of the different manufacturing processes, the design of the tungsten microhotplate can be applied to other thermal-based sensors, even in different standard CMOS processes.