Patent ID: 7678603

Claim:
A method for fabricating a via wave guide in a CMOS image sensor (CIS), the method comprising: forming a sensing element in a substrate; forming a metallization layer over the sensing element, wherein the metallization layer includes a plurality of insulation layers and a plurality of metal lines disposed in the insulation layers, and having an upper surface; dry etching the metallization layer through a mask opening to define a first, relatively narrow hole through the upper surface of the metallization layer, the first hole extending a first, relatively short distance between the upper surface and the sensing element; and wet etching the metallization layer through the mask opening to define an light concentrator of the via wave guide, the light concentrator having a first, relatively wide opening located adjacent to the upper surface and a tapered surface extending between the upper opening and a lower opening, the lower opening being smaller than the upper opening, wherein defining the light concentrator comprises forming a curved surface having a shape such that light beams directed toward the curved surface are redirected by the curved surface through the lower opening.