Design, modeling, microfabrication and characterization of novel micro thermal conductivity detector

This paper describes the design, modeling, fabrication, and characterization of a novel micro thermal conductivity detector (μTCD). To maximize the detection response, highly isolated thermistors and a four-filament Wheatstone bridge circuit were designed. To enhance the reliability, these thermistors were supported by a multi-layer structure beam formed by a diffusion of silicon layer, a silicon oxidation layer, and a silicon nitride layer. A polydimethylsiloxane (PDMS) membrane instead of a glass was used to seal the μTCD at the room temperature with a good sealing effect. Moreover this method could avoid the resistance variation of thermistors affected by the high temperature during the bonding step. From the pressure and the hermetic tests, the μTCD could withstand 0.5 MPa pressure without leakage and destroying the chip. Then the μTCD was used to detect the CH4 with a detection response of 500 ppm and a short response time of 30 s.