US Patent 11329089 Image sensor with multi-patterned isolation well

Pixel isolation wells in a semiconductor image sensor are implemented via two or more photoresist patterning phases and two or more corresponding dopant implantation operations. A distinct photomask is applied in each patterning phase with the isolation-well street lines patterned by each mask spaced from one another by an integer multiple (i.e., 2 or greater) of the pixel pitch, and patterns formed by respective masks being staggered by the pixel pitch.