Selected-area deposition of multiple active films for conductometric microsensor arrays

A new generation of planar conductometric gas sensors is being developed which combines active semiconducting oxide films with Si-micromachined 'micro-hotplate' array structures. These devices are tailored for a variety of applications by tuning both the composition of multiple types of active films and the temperature cycles programmed for individual elements within an array. In this paper we describe and demonstrate the approach, and present results for, a chemical vapor deposition (CVD)-based self-lithographic microfabrication method. This method is being examined as a highly efficient and compatible means of depositing oxide films and low-coverage catalytic metal overlayers on the microsensor elements of micro-hotplate arrays. Real-time monitoring of the film growth processes is provided by conductance measurements, and surveys of processing/property relationships can be performed in a very effective manner to determine optimal fabrication methods for multiple-active material arrays.