CMOS-integrated geometrically tunable optical filter

Commonly, optical filters consist of pigments on glass or of many stapled interference layers. In both cases, they are not applied on CMOS devices within the fab line, but through further processing, which also involves additional costs. In addition to this, pigment-based filters do not allow to perform a spectral analysis, which needs multichannel-based sensors, i.e. more than four different filters. Two methods for producing optical filters in the CMOS-line with different sensitivities are presented here. The first one consists of a structured metal layer embedded in oxide, whose working principle bases on plasmonics. The second one is a Fabry-Perot resonator with patterned cavity deposited with CMOS technology on top of the device. Both filters are characterized by a response which can be tuned by the geometric factors used in their patterning, allowing mutlichanneling. The filters have been simulated, realized and measured. The results are presented.