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

A novel prototype of low-power thick-film gas sensor deposited by screen-pr inting onto a micromachined hotplate is presented. The micro-heater is desi gned to maintain a film temperature of 400 degreesC with less than 30 mW of input power. The fabrication process involves a combination of standard, V LSI-compatible, micromachining procedures and computer-aided screen-printin g. A dielectric membrane of Si3N4 and SiO2 has been obtained with an embedd ed poly-Si resistor acting as a heating element. The bonding pad and contac ts 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 characterisat ion of a device, based on SnO2 sensing film, at working conditions together with the response curve for CH4 and NO2. We will also address some importa nt improvements to the micro-hotplate structure, which leads to an increase d flexibility of the device. (C) 2001 Elsevier Science B.V. All rights rese rved.