Low-power thick-film gas sensor obtained by a combination of screen printing and micromachining techniques

Abstract

A novel prototype of low-power thick-film gas sensor deposited by screen-printing onto a micromachined hotplate is presented. The micro-heater is designed to maintain a film temperature of 400°C with less than 30 mW of input power. The fabrication process involves a combination of standard, VLSI-compatible, micromachining procedures and computer-aided screen-printing. A dielectric membrane of Si 3N 4 and SiO 2 has been obtained with an embedded poly-Si resistor acting as a heating element. The bonding pad and contacts have been realised by a Ti/TiN/Cr/Au structure and the sensing film has been deposited by a screen-printing technique. Here follows a characterisation of a device, based on SnO 2 sensing film, at working conditions together with the response curve for CH 4 and NO 2. We will also address some important improvements to the micro-hotplate structure, which leads to an increased flexibility of the device.