Image sensors having grating structures therein that provide enhanced diffraction of incident light

Abstract

An image sensor may include a semiconductor substrate having a light receiving surface thereon and a plurality of spaced-apart semiconductor photoelectric conversion regions at adjacent locations therein. A grating structure is provided on the light receiving surface. This grating structure extends opposite each of the plurality of spaced-apart photoelectric conversion regions. An optically-transparent layer is provided on the grating structure. This grating structure includes a plurality of spaced-apart grating patterns, which can have the same height and the same width. In addition, the grating patterns may be spaced apart from each other by a uniform distance. The grating structure is configured to selectively produce ±1 or higher order diffraction lights to the photoelectric conversion regions, in response to light incident thereon.

What is claimed is: 
     
         1 . An image sensor comprising:
 a semiconductor substrate that has a first surface and a second surface opposite to the first surface;   a pixel separation structure that vertically extends from the first surface to the second surface and defines a pixel region;   a grating structure disposed on the second surface of the semiconductor substrate; and   a read-out circuit layer disposed on the first surface of the semiconductor substrate,   wherein a contact surface of the read-out circuit layer and the pixel separation structure is located on the first surface of the semiconductor substrate, and   wherein a top surface of the pixel separation structure is lower than a top surface of the grating structure.   
     
     
         2 . The image sensor of  claim 1 , wherein the top surface of the grating structure is higher than the second surface of the semiconductor substrate. 
     
     
         3 . The image sensor of  claim 1 , wherein the second surface of the semiconductor substrate is located at substantially the same level as the top surface of the pixel separation structure. 
     
     
         4 . The image sensor of  claim 1 , wherein the grating structure incudes grating patterns and recess regions alternately arranged, and
 wherein the grating patterns are protruded from the second surface of the semiconductor substrate.   
     
     
         5 . The image sensor of  claim 4 , wherein the top surface of the grating structure corresponds to top surfaces of the grating patterns. 
     
     
         6 . The image sensor of  claim 4 , wherein top surfaces of the grating patterns are higher than the second surface of the semiconductor substrate. 
     
     
         7 . The image sensor of  claim 1 , the grating structure comprises the same semiconductor material as the semiconductor substrate. 
     
     
         8 . The image sensor of  claim 1 , wherein the read-out circuit layer comprises:
 a transistor provided on the first surface of the semiconductor substrate, and   an interlayered insulating layer provided on the first surface of the semiconductor substrate to cover the transistor.   
     
     
         9 . The image sensor of  claim 1 , wherein the grating structure comprises grating patterns provided on the pixel region and arranged in an n x n matrix. 
     
     
         10 . The image sensor of  claim 1 , wherein the grating structure is designed to have a fill factor of 50%. 
     
     
         11 . The image sensor of  claim 1 , wherein the grating structure comprises grating patterns each has a rectangular shape when viewed in a plan view. 
     
     
         12 . The image sensor of  claim 1 , wherein the pixel separation structure surrounds the pixel region when viewed in a plan view. 
     
     
         13 . An image sensor comprising:
 a semiconductor substrate that has a first surface and a second surface opposite to the first surface;   a pixel separation structure that vertically extends from the first surface to the second surface and defines a pixel region;   a grating structure disposed on the second surface;   a vertical transfer gate disposed on the first surface;   a read-out circuit layer disposed on the first surface; and   wherein a first horizontal cross section of the pixel separation structure is wider than a second horizontal cross section of the pixel separation structure,   wherein the first horizontal cross section is closer to the first surface than the second horizontal cross section, and   wherein a vertical height of the vertical transfer gate is longer than a vertical height of the grating structure.   
     
     
         14 . The image sensor of  claim 13 , wherein the vertical height of the grating structure is a vertical length measured from the second surface of the semiconductor substrate to a top surface of the grating structure. 
     
     
         15 . The image sensor of  claim 13 , wherein the vertical gate electrode is disposed in a trench recessed from the first surface of the semiconductor substrate. 
     
     
         16 . The image sensor of  claim 13 , wherein the grating structure comprises grating patterns and recess regions alternately arranged,
 wherein the grating patterns are protruded from the second surface of the semiconductor substrate.   
     
     
         17 . The image sensor of  claim 13 , wherein the grating structure comprises grating patterns provided on the pixel region and arranged in an n x n matrix. 
     
     
         18 . The image sensor of  claim 17 , wherein the pixel separation structure surrounds the pixel region when viewed in a plan view. 
     
     
         19 . The image sensor of  claim 13 , wherein the grating structure is designed to have a fill factor of 50%. 
     
     
         20 . The image sensor of  claim 13 , wherein the grating structure comprises grating patterns each has a rectangular shape when viewed in a plan view.