Performance improvement of CMOS-MEMS Pirani vacuum gauge with hollow heater design

Abstract

A novel heater-with-holes design is developed to realize a CMOS-MEMS Pirani vacuum gauge. The Pirani vacuum gauge is a thermal-based pressure sensor consisting of heater and heat-sink units. The heat is conducted from heater to heat-sink through gas whose thermal conductivity changed with pressure. The proposed design has the following merits: (1) The holes on heater increase the thermal resistance and then improve the efficiency of heat transfer; (2) The heat-sink mesas are added to compensate the lost active area between heater and heat sink; (3) Easily integrate with other packaged CMOS-MEMS devices for pressure monitoring [1]. This study demonstrates two heaters with different hole-designs for concept proven. The devices have total die size of 206μm×82μm and 0.53μm sensing gap. Preliminary results show that the gauges have sensing range of 0.8-200torr and 0.2-200torr with sensitivity of 6.99×103(K/W)/torr and 8.15×103(K/W)/torr. The power dissipations are respectively 179.43μW and 127.59μW. In comparison, the conventional gauge containing heater w/o holes has sensing range 1-200torr with sensitivity of 0.91×103(K/W)/torr and power dissipation of 1117.34μW.