A CMOS compatible active thermopile with high frequency measurement

Abstract

A considerable number of measurements for microsensors and system characterisations rely on the analysis of its step response. Device parameters of thermal microsensors are essential for evaluating the sensor performances and their simulation modelling. For the thermal microsensors, the thermal parameters are sometimes show important relations to the package, which is not an ideal heat sink. By decoupling the heat equations for the membrane of sensor and package, we first build a multiple-time-constant modelling of thermal microsensors, which describes a more realistic thermal behaviour. The behaviour on spectrum domain and time domain are predicted and been proved by our experiments. An investigation of high frequency response for CMOS compatible thermoelectric infrared sensors is proposed and fabricated. The sensors are fabricated by a 1.2 /spl mu/m industrial CMOS IC technologies combined with a subsequent anisotropic front-side etching stop. To reach a larger response signal, we fabricated a large floating membrane structure with a built-in polysilicon resistor as a signal modulator. It consists of a heating polysilicon resistor and an Al/ n-polysilicon thermopile, embedded in an oxide/nitride membrane. High frequency response of a test sample shows unexpected large signal, which is quite interesting and never reported before. We have made a thoroughly measurement and analysis, and give some interesting results.