Optical isolation structure for reducing crosstalk between pixels and fabrication method thereof

Abstract

An optical isolation structure and a method for fabricating the same are provided. The optical isolation structure includes an epitaxial layer and a dielectric layer. The epitaxial layer and the dielectric layer are formed in a deep trench of a semiconductor substrate. The epitaxial layer covers a lower portion of sidewall of the trench, and the dielectric layer covers an upper portion of the sidewall of the trench. In the method for fabricating the optical isolation structure, at first, shallow trenches are formed in the semiconductor substrate. Then, the dielectric layer is formed in the shallow trenches. Thereafter, deep trenches are formed passing through the dielectric layers. Then, the epitaxial layer is formed in the deep trenches.