Charge coupled device with potential gradient region between two control gate regions

Abstract

A six-phase charge coupled device (CCD) pixel includes a pixel pair, with each pixel having two adjacent control gates overlying corresponding variable potential wells, where voltages applied to the control gates enable charge to be accumulated into and transferred out of the wells. A clear window region overlies a fixed potential gradient region, decreasing in potential away from the control gates. This region enables a wide band of photons to be sensed by the photosensitive silicon of the CCD. The decreasing potential levels facilitate high charge transfer efficiency (i.e., high CTE) from pixel to pixel via the control or transfer gates. By applying particular voltages to the control gates, charge can be quickly and efficiently transferred between pixels. In addition, the window provides a self aligned mask for the implantation steps and thus prevents the formation of pockets (or wells) due to misalignments that decrease the charge transfer efficiency and causes non-uniformity problems as associated with prior art. Furthermore the window provides a flat region that can be covered with an anti-reflective (AR) coating layer, thus further increasing the quantum efficiency.