Design and fabrication of micro-hotplate for thin film gas sensor

This paper reports a novel approach to fabricate a micro-hotplate for a thin film gas sensor. The approach uses frontside anisotropic etching of silicon together with special layout to create the thermally isolated structure. A sandwich of inter-dielectric layers and aluminum interconnection provides the supporting material while highly doped boron diffusion provides the heating and temperature sensing elements. The design incorporates a guard heater layout that improves the temperature uniformity. Simulation results show that the temperature variation on a sensor film of 50×60 μm² is less than 25°C when the operating temperature is 350°C. The micro-hotplate exhibits heating efficiency of about 7°C/mW and is compatible with standard technology