Patent ID: 8779539

Claim:
An image sensor comprising: a substrate, having a front-side surface and a back-side surface opposite to the front-side surface; an interconnect structure, disposed on the front-side surface; a plurality of photoelectric transducer devices, formed on the front-side surface; at least one dielectric isolator, extending downwards into the substrate from the back-side surface in order to isolate the photoelectric transducer devices; a back-side alignment mark, comprising a p + doping layer, a dielectric layer, an anti-reflective coating layer and a metal shielding layer formed in a recess extending downwards into the substrate from the back-side surface; wherein the p + doping layer is formed in the recess of the back-side alignment mark and on sidewalls of the at least one dielectric isolator before the dielectric layer, the anti-reflective coating layer and the metal shielding layer are disposed in the recess in a manner of referencing to a front-side alignment mark previously formed on the front-side surface.