A novel pixel structure for 2 &mgr;m square pixel IT-CCD

A pixel structure suitable for an interline transfer charge-coupled device (IT-CCD) image sensor with a pixel size of 2 &mgr;m square or less was developed. The first feature relates to the structure of a transfer electrode, which consists of island transfer electrodes and horizontally continuous transfer electrodes, alternately placed in the form of a single layer. The island electrode is connected with polysilicon wiring formed on the horizontally continuous electrode. This pixel structure eliminates one of two electrodes on the channel stop region of the conventional single layer electrode structure. Over 30% Expansion of the photosensitive areas of 2 &mgr;m square pixel compared to the conventional design was achieved. Carrier crosstalk between adjacent pixels, often caused by application of read-out voltage to the channel stop region, is successfully suppressed in the new structure. The second feature comes from the photo-shield shape around the photodiode. By removing the extension of the photo-shield and reducing the thickness of the lateral side of the photo-shield, the fill factor can be expanded by 70%. In addition, the eclipse of incident light by the photo-shield above the vertical register is suppressed. These developments have led to the achievement of high performance in photo-sensitivity, especially in the small F number region, sensitivity shading, handling charge of the photo diode, and have provided a beneficial solution for sub-2 &mgr;m square pixel IT-CCD.