THIN-FILM OPTICAL SENSORS WITH SILICON-COMPATIBLE MATERIALS

Antireflection filters based on multilayer stacks of dielectric and po lysilicon films on monocrystalline silicon combined with charge collec tion in different (poly)Si layers can be used to realize sensors with a programmable spectral response controlled by weighted summing of the photocurrents detected in the polysilicon and the substrate. Thus, em ploying both interference and selective absorption of light yields inc reased photoelectric efficiency and improved flexibility of spectral c ontrol and enables on-chip integration of the detector(s) with the sig nal conditioning and processing circuits. The potential of thin-film c olor sensors has been evaluated for this purpose. However, for practic al implementation of such structures the problems associated with the realization of reliable photodetectors in polysilicon must also be con sidered. Phosphorus passivation of the grain-boundary states has been employed to yield polysilicon photodiodes with improved electrical cha racteristics and reliable light and color detection. We present the de sign methods of thin-film color sensors employing silicon-compatible m aterials only. The measurement results of a fabricated structure fully demonstrate that such sensors can be realized with good spectral sele ctivity. (C) 1997 Optical Society of America.