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 µm 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 µm, 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 × 10 −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.[