Technologies to improve photo-sensitivity and reduce VOD shutter voltage for CCD image sensors

New technologies to increase the photo-sensitivity and reduce the shutter voltage of the vertical over-flow-drain (VOD) have been developed for CCD image sensors. The photo-sensitivity was increased 40% by forming an anti-reflection film over the photodiode and reducing the thickness of the p/sup +/-layer formed at the photodiode surface. The VOD shutter voltage was reduced from 31 to 18 V by using an epitaxially grown substrate with double impurity concentration layers.