Image sensor with improved output region for superior charge transfer characteristics

Abstract

The new CCD output region provides a method of reducing the width of a wide CCD at its output to maintain a high sensitivity output node without sacrificing charge-transfer efficiency. A barrier region is shaped so the "channel width" of the CCD increases towards the input edge of the output gate. The barrier region, therefore, decreases in width towards the output end of the final CCD phase of a multi-phase device. Also, the channel width under the output gate decreases towards its output end in the direction of charge transfer towards the floating diffusion, or detection node. Since the "shaped" portion of the barrier region under the last CCD phase can be formed by the same process steps as the regular-shaped barrier regions, it is possible to form this structure without the requirement for additional masking and implant steps. The advantages of this structure over the prior art are improved charge-transfer characteristics without requiring additional process steps.

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