Smart single-chip CMOS microhotplate array for metal-oxide-based gas sensors

A monolithic gas sensor system is presented, which includes on a single chip an array of three metal-oxide covered microhotplates, each of which is individually addressable and can be operated at a defined temperature. The monolithically co-integrated circuitry consists of three independent temperature control loops for the microhotplates and an on-chip temperature sensor. An innovative design of a circular-shape microhotplate has been realized. Temperature homogeneity and thermal efficiency of the membrane were optimized for use with thick films of nanocrystalline metal oxides as sensitive layers. A SnO/sub 2/-based sensing material with noble metal doping was operated at different temperatures as well as in temperature pulsing mode. Chemical sensor measurements have been conducted with, e.g., CO to show the system performance.