A batch-fabricated silicon thermopile infrared detector

A thermopile infrared detector fabricated using silicon integrated-circuit technology is described. The device uses a series-connected array of thermocouples whose hot junctions are supported an a thin silicon membrane formed using anisotropic etching and a diffused boron etch stop. The membrane size and thickness control the speed and responsivity of the structure, which can be designed for a given application. For a 2-mm × 2-mm × 1-µm silicon membrane containing sixty bismuth-antimony couples, the structure produces a responsivity of 6 V/W and a time constant of about 15 ms. The use of polysilicon-gold couples can improve the responsivity to nearly 10 V/W while maintaining the same speed, simplifying the process, and retaining compatibility with on-chip signal processing circuitry.