Application specific spectral response with CMOS compatible photodiodes

Several methods are presented for realizing photodiodes with independent spectral responses in a standard CMOS integrated circuit process. Only the masks, materials, and fabrication steps inherent to this standard process were used. The spectral responses of the photodiodes were controlled by (1) using the SiO₂ and polycrystalline Si as thin-film optical filters, (2) using photodiodes with different junction depths, and (3) controlling the density of the interfacial trapping centers by choosing which oxide forms the Si/SiO ₂ interface. Also presented is an example method for constructing photo-spectrometers using these spectrally-independent photodiodes. This method forms weighted sums of the photodiodes´ outputs to extract spectrographic information