Modeling of Front-Etched Micromachined Thermopile IR Detector by CMOS Technology

CMOS-compatible thermopile detectors are widely used for IR detection. In this paper, an analytical model is developed for front-etched thermopile IR detectors using CMOS technology. By dividing the front-etched microbridge thermopile detector into cantilever thermocouple detectors with separate absorber areas, the thermal gradient in each zone of the single thermocouple IR detector (absorber and thermocouple transducer) is analyzed using 1-D method. During thermal gradient modeling, the IR absorption of dielectric layers in the thermocouple area is also considered. The thermopile IR detector performance is then calculated by adding the temperature differences of each single thermocouple IR detector. The developed analytical model has been verified by comparing simulations with experiments. The simulation results closely agree with the measured results. For optimizing the geometry of the front-etched thermopile IR detector, a quantitative study of the detector performance is conducted with respect to the absorber width, polysilicon length, polysilicon width, and etching window width.