Optical limitations to cell size reduction in IT-CCD image sensors

We have determined the practical limits of cell size reduction in interline-transfer CCD image sensors, limits resulting 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 μm. We have also found, however, that image cells with greater than 0.2 μm aperture size are sensitive over the entire wavelength range of visible light, and that sensitivity can be increased by thinning the photoshield film