Monolithic metal-oxide microsensor system in industrial CMOS technology

Abstract

A novel monolithic gas sensing system is presented, which includes a microhotplate and advanced analog and digital circuitry for sensor control, signal readout and communication. An innovative design of a circular-shape microhotplate has been implemented and was optimized for use with a thick film of nanocrystalline tin dioxide as sensitive layer. Post-CMOS processing steps for an electrode metalization on wafer level were developed. The integrated circuitry consists of a programmable digital temperature controller, a logarithmic converter for the sensor signal, an on-chip temperature sensor, and a standard serial interface. The detection of less than 1ppm CO has been achieved with this system in gas test measurements.