A monolithic thermopile detector fabricated using integrated-circuit technology

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 on 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 membrane measuring 2mm × 2mm × 1µm and containing sixty bismuth-antimony couples, the structure produces a responsivity of 7 volts/watt and a time constant of about 15 msec. Polysilicon couples and the use of slotted membranes can provide further performance improvements while retaining compatibility with on-chip signal processing circuitry.