Method of forming a photo sensor in a photo diode

Abstract

A semiconductor wafer is provided. The semiconductor wafer comprises a silicon substrate containing first-type dopants, a well of first-type dopants positioned in a predetermined region on the substrate, and a photo diode positioned on the semiconductor wafer. The photo diode comprises an active region positioned on the surface of the well. The active region is used to form a MOS transistor of second-type dopants. An insulation layer is positioned on the surface of the substrate and surrounds a predetermined photo sensor, the photo sensor being positioned beside the well. Following this, a first ion implantation process is performed to form a first doped region of second-type dopants on the surface of the photo sensor. A second ion implantation process is then performed to form a second doped region of second-type dopants inside the photo sensor. The second doped region is positioned under the first doped region, and the dopant density of the second doped region is less than that of the first doped region. Hence, the second doped region functions to reduce the electrical field around the first doped region to reduce leakage current.

Dependencies are inferred from the claim text.