Thermal properties of suspended porous silicon micro-hotplates for sensor applications

Abstract

In this work, the thermal properties of suspended porous silicon (PS) micro-hotplates are investigated. The micro-hotplates are fabricated by a novel technique, based on the isotropic etching of silicon under a PS layer, in a high-density plasma reactor. Suspended PS micro-hotplates with integrated heaters have been fabricated and characterized. Both the supporting beams and the rim surrounding the membrane are made of PS. This results in minimization of the thermal losses to the substrate. Very high local temperatures on the micro-hotplates (higher than 600°C) with very low power consumption (only a few tens of mW) have been obtained, due to the very low thermal conductivity of PS, which is comparable to that of thermal oxide and it is much lower than that of silicon nitride, typically used for thermal sensor applications.