Patent ID: 8329499

Claim:
A method of forming a lateral overflow drain and a channel stop associated with a pixel of an image sensor, the pixel comprising one or more shift elements for the accumulation of charge carriers in response to exposure to light, the method comprising: forming a first mask layer over a semiconductor layer; removing a portion of the first mask layer, thereby forming a first opening; forming a second mask layer over the first mask layer; removing a portion of the second mask layer to form a second opening disposed within and sharing a boundary with the first opening; introducing dopants having a first conductivity type into the semiconductor layer through only the second opening, thereby forming a lateral overflow drain for draining excess charge carriers from the one or more shift elements; removing a remaining portion of the second mask layer; and after removing the remaining portion of the second mask layer, introducing dopants having a second conductivity type opposite the first conductivity type into the semiconductor layer through the first opening, thereby forming a channel stop for preventing movement of charge carriers from the one or more shift elements into a second pixel adjacent to the pixel, wherein the lateral overflow drain is disposed within and substantially shares a boundary with the channel stop.