A digital CMOS micro-hotplate array for analysis of environmentally relevant gases

A monolithic gas sensor array fabricated in industrial CMOS-technology combined with post-CMOS micromachining is presented. The device comprises an array of three metal-oxide-coated micro-hotplates with integrated MOS-transistor heaters and the needed driving and signal-conditioning circuitry. The operating temperature of the SnO₂ metal oxide resistors varies between 200 and 350°C. Three digital PID controllers enable individual temperature regulation. Interface and temperature control are implemented digitally, making a power-saving mode and temperature modulation, to enhance the analyte discrimination, applicable. Emphasis was placed on a modular system with the required analog circuitry reduced to a minimum.