Surface Micromachined CMOS-MEMS Pirani Vacuum Gauge With Stacked Temperature Sensor

Abstract

In this paper, we present a surface micromachined Pirani vacuum gauge integrated with a stacked temperature sensor using CMOS-MEMS technology. The proposed Pirani gauge features a $2.23~\mu \text{m}$ thick suspended microheater, which is positioned between two designed heat sinks. The upper and lower gap spacing between the heat sink and the microheater is $0.53~\mu \text{m}$ , which is made by the surface etching of two metal films. Additionally, a temperature sensor based on a poly-Si resistor is directly integrated into the lower heat sink. The temperature sensor shows a sensitivity of 45 ohm/°C over a linear range of 10~60 °C, while its measurement error is less than 0.11 °C in the worst case. The Pirani gauge achieves a high sensitivity of 0.96 V/Dec under fine vacuum conditions, and its heating power is less than 8.3 mW in the vacuum range of 0.8~14000 Pa. Moreover, the measured output of the Pirani gauge closely matches the proposed semi-empirical model, while the noise measurements indicate that the sensor has a resolution as low as $6.4\times 10 ^{\mathbf {-3}}$ Pa in very fine vacuum conditions. This integrated Pirani gauge and temperature sensor system, in combination with its high performance, makes it a promising sensing node for vacuum and temperature monitoring in semiconductor equipment. [2023-0184]