Patent ID: 8232133
Filing Date: 2012-07-31
Classification: H01L

Abstract:
1. A method, comprising: receiving visible light incident on a frontside of a frontside illuminated (“FSI”) image sensor including a photodiode region of a first dopant type disposed within a semiconductor layer of a second dopant type opposite the first dopant type, wherein the visible light includes photons having shorter and longer wavelengths; filtering the visible light within the semiconductor layer and a dopant layer disposed within the semiconductor layer between the photodiode region and a back side of the semiconductor layer, wherein the dopant layer has a higher concentration of the second dopant type than the semiconductor layer; reflecting the photons having the longer wavelengths back towards the photodiode region with a reflective layer disposed on the back side of the semiconductor layer, wherein a thickness of the semiconductor layer is selected such that primarily the photons having the longer wavelengths are reflected by the reflective layer back towards the photodiode region while the photons having the shorter wavelengths are substantially absorbed prior to reaching the reflective layer; and generating electrical signals responsive to visible light.