Abstract
Silicon piezoresistive pressure sensor technology has recently been gaining ground in its use in many advanced applications. In order to meet the needs of mechanical signal sensing in the industry, the different characteristics of pressure sensors need to be crucially taken into account. Therefore, our research employs simulations and experiments to determine the factors which produce the thermal hysteresis voltage in thermal cycle loadings. The purpose of this is to achieve measurement accuracy and avoid the thermal hysteresis phenomenon. The silicon piezoresistive pressure sensor is fabricated by the MEMS process, and utilizes the ion implant technique to form the piezoresistors on the silicon substrate. The main principle for operation is that the external pressure loading causes the deflection on the silicon membrane. Then a piezoresistive effect results in a resistance change in the piezoresistor on the silicon membrane. Using the Wheatstone Bridge transforms the mechanical signal to an output voltage in order to obtain the unknown pressure loading. However, the sensitivity of the piezoresistive pressure sensor is relatively high for the environmental temperature, thereby reducing accuracy. Therefore, the drifts of the output voltage in the same temperature result in a residual stress on the aluminum trace under thermal cycle loading. This situation is called the thermal hysteretic phenomenon, and the variation in output voltage is called the thermal hysteresis voltage. Given these, one goal of the current research is to analyze the relation between the residue stress of the trace and the thermal hysteresis voltage in order to reduce the measurement error in the thermal hysteresis phenomenon. The thermal hysteresis phenomenon is produced by the thermal expansion coefficients’ mismatch with the nonlinear properties of the aluminum trace in the thermal cycle loadings. Furthermore, this research will input the nonlinear properties of aluminum trace in ANSYS® and will base on the process of the pressure sensor to obtain the thermal hysteresis voltage. After several numerical analyses of the thermal hysteresis voltage, experiments will be performed to validate the simulation results. We will revise the process simulation for the etching effect in order to analyze the thermal hysteresis voltage’s differences. The research will also do a series of simulations and experiments on the creep effect that usually affects the thermal hysteresis voltage in the pressure sensor. To sum up, both the simulations and experiments systematically discuss the hysteresis phenomenon of the pressure sensor. The study’s conclusions will hopefully provide designers with relevant guidelines in the relative field.