Thermopile-structured micro thermal conductivity vacuum sensor

A novel type of micro-thermal conductivity vacuum sensor has been developed, on the basis of the thermopile structure, and fabricated with commercially standardized complementary metal oxide semiconductor (CMOS) processes. The device consists of the composite sensing multi-layers, 124μm×100μm, in the form of a micro-bridge suspended over the cavity etched on the silicon substrate, a n-type poly-silicon heater, and a thermopile made up of 20 pairs of poly-silicon-aluminum thermocouples. The discussions focused on the following: i) the design and fabrication process; ii) the finite element analysis (FEA) of the steady and transient states of the device; and iii) comparison of the experimental and theoretical results. When resistively heated at 1.5 V the experimental results show the pressure sensing ranges from 0.1 Pa to 105 Pa (of air) with a thermopile output of 26 mV to 50 mV, and a response time around 1.4 ms.