Design and electro-thermal simulation of a polysilicon microheater on a suspended membrane for use in gas sensing

Abstract

A microhotplate array comprising four 100 μm × 100 μm unit cells has been designed. It has a multi-layer structure: Si-thermal oxide-polySi-PECVD (plasma enhanced chemical vapour deposition) oxide-Sputtered Pt-Gas sensing film (SnO₂). Electro-thermal simulation of the unit cell has been carried out using ANSYS. The simulations show that for an applied bias of 4 V a mean temperature of 706ºC is obtained at the centre of the heater area. The heat is assumed to flow from the hot plate to the surrounding air at an ambient temperature of 30ºC by conduction. The power dissipation is less than 50 mW. The paper presents the design methodology of the hotplate.