Quantitative Analysis of MEMS Piezoresistive Pressure Sensors Based on Wide Band Gap Materials

Wide band gap materials such as silicon carbide and diamond are considered more suitable compared to silicon for the fabrication of piezoresistive pressure sensors for operation at high temperatures. We have carried out extensive FEM simulation study for theoretically assessing the response of pressure sensors incorporating these wide band gap materials. Response of sensors incorporating silicon micromachined diaphragm with oxide isolated piezoresistors of diamond or silicon carbide was studied using FEM simulations. The study was further extended for sensors incorporating diaphragm as well as piezoresistors of diamond or silicon carbide. The results in both cases were compared with those obtained for a single crystal or polycrystalline piezoresistor-based silicon pressure sensor. The results presented in this paper demonstrate that among the materials studied in this work, diamond-based sensors will have the least pressure sensitivity compared to silicon carbide or silicon-based sensors. However, considering the nonlinearity of response, diamond-based sensors will have the minimum nonlinearity of pressure response compared to silicon-based pressure sensors. Hence for the same nonlinearity, it would be possible to operate the diamond-based sensors up to much higher pressures.