Choice of insulation materials and its effect on the performance of square microhotplate

One of the methods, to improve the uniformity of a microhotplate is to provide an insulation layer of optimum dimensions between the heater and gas sensor. In this paper, two insulation layer material, silicon nitride and silicon carbide, are investigated. Simulation studies are carried out to find the optimum dimension of insulation layer, required for a targeted uniformity of 0.22 K/mu m, a value comparable to the reported literature. With 8 mu m thick silicon nitride layer, a thermal uniformity of 0.18 K/mu m is obtained whereas the same is achieved with a 1.5 mu m thick silicon carbide layer. Therefore, the deposition time in the whole process will significantly reduce by employing silicon carbide layer while retaining similar uniformity. It has been established that, the proposed method not only serves the purpose of providing electrical insulation and improve thermal uniformity but also improves the mechanical stability. The silicon carbide is compared with silicon nitride layer in terms of performance parameters and a table is also listed, highlighting the practical aspects involved in the choice of these two insulation layer materials.