Fabrication of suspended porous silicon micro-hotplates for thermal sensor applications

Abstract

In this work, we describe a process for the fabrication of suspended porous silicon micro-hotplates for application in thermal sensors. Membrane release is achieved by means of lateral isotropic etching of the bulk silicon substrate, the etching being highly selective to the porous silicon and the photoresist used to protect the structure. High lateral etch rates are achieved (of the order of 6–7 μm/min) in a high-density plasma reactor, which permit a reasonable etching time for the release of the membranes and the simultaneous formation of the cavity underneath, used for thermal isolation of the final device.