Patent attributes
A single photon avalanche diode (SPAD) image sensor is disclosed. The SPAD image sensor includes: a substrate having a front surface and a back surface; a trench isolation in the substrate, the trench isolation extending from the front surface of the substrate toward the back surface of the substrate, the trench isolation having a first surface and a second surface opposite to the first surface, the first surface being coplanar with the front surface of the substrate, the second surface being distanced from the back surface of the substrate by a distance greater than 0; wherein the substrate includes: a first layer doped with dopants of a first conductivity type, the first layer extending from the back surface of the substrate toward the trench isolation and laterally surrounding at least a portion of sidewalls of the trench isolation.