Patent ID: 8796805

Claim:
A method comprising: forming an opening in a semiconductor substrate, wherein the opening extends from a back surface of a semiconductor substrate to a metal pad on a front side of the semiconductor substrate; forming a first conductive layer on a backside of the semiconductor substrate, wherein the first conductive layer extends into the opening to contact the metal pad; forming a second conductive layer over the first conductive layer, wherein the first and the second conductive layers comprise different materials; performing a first patterning step to remove the second conductive layer from a first device region and a second device region, wherein a portion of the second conductive layer over the metal pad remains after the first patterning step, and wherein the first conductive layer is used as an etch stop layer in the first patterning step; and performing a second patterning step to remove portions of the first conductive layer from the first device region, wherein a portion of the conductive layer in the second device region remains after the second patterning step to form a metal shield, and wherein the metal shield overlaps a black reference image sensor.