Method for forming shallow trench isolation structure with deep oxide region

Abstract

The present invention relates to a shallow trench isolation structure and a method for forming a shallow trench isolation structure on a semiconductor substrate. A masking structure that includes a hard mask is formed over the semiconductor substrate and an etch is performed so as to form trenches within the semiconductor substrate. A shallow trench isolation structure and a method for forming a shallow trench isolation structure are disclosed. Oxidation enhancing species are then implanted into the bottom surface of the trenches and an oxidation process is performed. The oxidation enhancing species will form a deep oxidation region below the bottom surface of each trench and will form thinner oxidation regions within side surfaces of trenches. A layer of dielectric material is then deposited to fill the trenches. A chemical mechanical polishing process is performed to remove those portions of the dielectric film that overlie the hard mask. The hard mask is then removed, producing a void-free shallow trench isolation structure.