A wide measurement pressure range CMOS-MEMS based integrated thermopile vacuum gauge with an XeF2 dry-etching process

This paper reports a wide pressure measurement range CMOS-MEMS based integrated thermopile vacuum gauge with an XeF2 dry-etching process. By using XeF2 front-side dry-etching process, a small gap between the suspended heater and the substrate has been obtained, which can extend the upper pressure limit of the gauge. Meanwhile, a small size about 0.4 mm × 1.5 mm of the gauge structure has been obtained, and a good yield of 93% for elements in a wafer has been achieved. A cap mounted on the integrated thermopile vacuum gauge by wafer level glass frit bonding enhances the gas thermal conduction between the heater and the cap, which increases the sensitivity of the gauge and enlarges the sensing pressure range of the gauge. Moreover, a cap mounted on the gauge provides a chamber to protect the floating integrated thermopile vacuum gauge structure and a good yield of better than 90% for the packaged integrated thermopile vacuum gauge has been achieved. The constant power of 4.5 mW is applied to the device, and experimental results show the integrated thermopile vacuum gauge has a good response to the gas pressure from 5 × 10−3 Pa to 105 Pa.