CMOS Compatible MEMS P/N Polycrystalline Silicon Thermopile IR Detector

With the increasing advancement of IR (infrared radiation) detecting technology in both military and civil domain, uncooled IR technique has become the mainstream in IR technology progress which directs to low cost and miniaturization in recent years. It utilizes the growing MEMS technology with the conversions among light-heat-electricity to detect IR. This technology has the advantages of light weight, less complexity, low energy consumption and low cost. Thermopile IR detector is one of the first thermal IR imaging device that has been studied and applied. MEMS IR thermopiles perform much better than conventional IR thermopiles since that MEMS technology could decrease heat conduction and improve the integration of the devices.Most of MEMS IR thermopiles are fabricated by back-etching or complicated front-etching technologies, which are not so compatible with CMOS technology, which need post processes and is strict with process and lead to low product rates. In this thesis, we give full consideration to the compatibility with CMOS technology and fabricate MEMS thermopile IR detector through designing a front-cut thermopile structure.As concerned with thermocouple material, metal thermocouples, polycrystalline silicon-metal thermocouples and silicon/polycrystalline silicon-aluminum thermocouples are commonly used as the thermocouple materials. In CMOS compatible materials, the seebeck coefficient of most metals is low while that of silicon is high. So the MEMS thermopile fabricated in this thesis uses p doped poly-Si and n doped poly-Si as thermocouple materials which will lead to higher responsivity.In the course of design and optimizing, we put forward a simplified model based on current structure and describe the analytical relations between device structure and performance parameter. After overall consideration among performance parameters as responsivity, detectivity and thermal time, we optimize the key structure size of the device and analyze the optimized structure by finite element methods and simulative calculations.