Infrared micro-spectrometer based on a diffraction grating

The optical properties of crystalline silicon in the IR spectral range have been used for the realisation of a grating type micro-spectrometer. An aluminium metallisation on a double side polished silicon wafer is used for fabrication of the multi-slit gratings. The dispersed spectrum propagates through this silicon wafer and is projected on an array of polysilicon thermopiles, integrated in a second bulk micromachined silicon wafer. The two wafers are bonded at low temperature. An IR spectrometer results, which is simple to fabricate and remains compatible with standard IC processing.