Patent ID: 6573118
Filing Date: 2003-06-03
Classification: H01L

Abstract:
A method of forming a photo sensor in a photo diode on a semiconductor wafer, the surface of the semiconductor wafer comprising a silicon substrate containing first-type dopants, a well of first-type dopants positioned in a predetermined region on the substrate, a photo diode positioned on the semiconductor wafer and comprising an active region positioned on the surface of the well, the active region being used to form a MOS transistor of second-type dopants, and an insulation layer positioned on the surface of the substrate surrounding a predetermined photo sensor, the photo sensor positioned beside the well, the method comprising:performing a first ion implantation process to form a first doped region of second-type dopants having a first dopant density and a first implantation depth on the surface of the photo sensor; and performing a second ion implantation process to form a second doped region of second-type dopants encompassing the first doped region inside the photo sensor, wherein the second doped region has a second dopant density smaller than the first dopant density and a second implantation depth larger than the first implantation depth, and wherein a portion of the second doped region is positioned beneath the insulation layer; wherein the second doped region functions to reduce the electrical field around the first doped region so as to reduce leakage current.