US Patent 7589306 Image sensor with buried self aligned focusing element

An image sensor includes an optical sensor region, a stack of dielectric and metal layers, and a buried focusing layer. The optical sensor is disposed within a semiconductor substrate. The stack of dielectric and metal layers are disposed on the semiconductor substrate above the optical sensor region. The metal layers include optical pass-throughs aligned to expose an optical path through the stack form a top dielectric layer through to the optical sensor region. The buried focusing layer is disposed over a conforming metal layer of the metal layers within the stack. The buried focusing layer includes a curved surface conformed by the optical pass-through of the conforming metal layer to focus light onto the optical sensor region.