METHOD FOR MAKING CMOS IMAGE SENSOR INCLUDING SUPERLATTICE TO ENHANCE INFRARED LIGHT ABSORPTION

摘要

A method for making a CMOS image sensor may include forming a plurality of laterally adjacent infrared (IR) photodiode structures on a semiconductor substrate having a first conductivity type. Forming each IR photodiode structure may include forming a superlattice on the semiconductor substrate including a plurality of stacked groups of layers, with each group of layers including a plurality of stacked base semiconductor monolayers defining a base semiconductor portion, and a non-semiconductor monolayer(s) constrained within a crystal lattice of adjacent base semiconductor portions. The superlattice may have the first conductivity type. A semiconductor layer may be formed on the superlattice, along with a retrograde well extending downward into the semiconductor layer from a surface thereof and having a second conductivity type, a first well around a periphery of the retrograde well having the first conductivity type, and a second well above the retrograde well having the first conductivity type.