We have determined the practical limits of cell size reduction in interline-transfer charge-coupled device (IT-CCD) image sensors, which result from diffraction occurring at the aperture above the photodiode. We have found that image cell size cannot be reduced to a level for which aperture width would fall below about 0.2 /spl mu/m. We have also found, however that image cells with greater than 0.2 /spl mu/m aperture size are sensitive over the entire wavelength range of visible light, and that sensitivity can be increased by thinning the photoshield film.
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