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Thermopile detectors are particularly well suited for spectral imaging, space science applications, track recording, presence detection and applications with low energy consumption. The purpose of this work is the fabrication of a surface micromachined 2-D high detectivity infrared thermopile array using a thermoelectrically effective Bi0.87Sb0.13-Sb thermopair materials combination. The thermopile array comprises 8 x 8 pixels with an active area of 100 microns in square, which are wired directly. Each pixel consists of eight Bi0.87Sb0.13-Sb thermocouples arranged on top of each other, which are isolated and passivated by a thin layer of SixNy. The intrinsic stress of SixNy layers is well suited to avoid a sticking effect or an excessive deflection of the absorber area after removing the sacrificial layer. Thermopile structure and absorber area are manufactured upon a sacrificial layer based on polyimide. This organic material can be structured well in an oxygen rf-plasma process with a high selectivity to the membrane material. After removing the sacrificial layer in an isotropic plasma process, membranes are free-standing and suspended by four spiral legs. Due to their long thermal paths and low thermal conductivity this legs provide a high thermal gradient between the absorber area, heated by an incoming infrared radiation, and the substrate surface, which acts as a heat sink. Thermoelectric layers as well as wiring layers were patterned almost exclusively by lift-off technique in order to obtain very small structure dimension with high reliability as well as high integration level. Detectors can be equipped with two absorber types. For broadband application a well suited colloidal silver black layer absorber is available. A second option is a quarter wavelength arrangement with a absorption coefficient of 0.88 suited for the 8-14 μm band. A higher absorption coefficient was obtained with the silver black layer absorber over a broad spectral range. This layer was deposited in an evaporation process after the sacrificial layer was removed. The amount of absorption depends on the deposited thickness and can be well controlled by the process. The detectivity of so manufactured IRFPAs is about ⋅ 9 1 10 cmHz 1/2 /W exceeding most of the state-of-the-art thermopile detectors. The time constant was measured to be 36 ms.

1.3 - High Detectivity Uncooled Thermopile IRFPA Chip Prepared by Surface Micromachining