Semiconductor structure of backside illumination cmos image sensor and method for forming the same

Abstract

The present disclosure provides a method of manufacturing a semiconductor structure of a CMOS image sensor. The method includes providing a substrate; growing an epitaxial layer on the substrate; forming a barrier layer on the epitaxial layer; forming a trench extending into the epitaxial layer; oxidizing the epitaxial layer to form a liner layer; defining a region of a photodiode and a first dopant thickness; implanting dopants into the epitaxial layer around a sidewall of the trench to form a protective layer with a second dopant thickness less than the first dopant thickness; forming an oxide layer in the trench; performing an annealing operation to densify the oxide layer to form a densified oxide layer, wherein the protective layer, expanded from the second dopant thickness to a third dopant thickness less than the first dopant thickness, is kept spaced from the region; and forming the photodiode in the region.