Image sensor pixel with deep trench isolation structure

Abstract

An image sensor device is disclosed. The image sensor device includes a substrate having a plurality of pixel regions. Two adjacent pixel regions are optically and electrically isolated by a deep trench isolation structure. In an embodiment, a method of forming the deep trench isolation structure includes receiving a workpiece comprising a first isolation structure formed in a front side of a substrate, forming a trench extending through the first isolation structure and the substrate, forming a dielectric liner to line the trench, depositing a conductive layer conformally over the workpiece after the forming of the dielectric liner, and depositing a dielectric fill layer over the conductive layer to fill the trench. A refractive index of the dielectric fill layer may be smaller than a refractive index of the conductive layer. The present disclosure also includes an alternative method for forming isolation structures at a back side of the substrate.