Micromechanical fabrication of robust low-power metal oxide gas sensors

A fabrication process for miniaturized low-power metal oxide gas sensor arrays is presented. This process, which is based on silicon-on-insulator (SOI) wafers, leads to thermally insulated silicon hot plate structures, which successfully combine low-power consumption with mechanical ruggedness and a high process yield. A second important feature of our process is that it consists of a standard-silicon front-end and a sensor-specific back-end module. This separation into front-end and back-end modules is a prerequisite for an efficient workshare between silicon foundries and SME sensor manufacturers in the industrialization of low-power gas sensor arrays. In the first part of the paper we present an outline of the fabrication flow consisting of the front-end fabrication of micromachined low-power heater platforms and the back-end fabrication of gas-sensitive layers. In the second part we report on the results of extensive mechanical, thermal and gas sensing measurements on such miniaturized devices.