Imaging systems with crosstalk reduction structures

Abstract

An imaging system may include a camera module with an image sensor having an array of image sensor pixels. The image sensor may include a substrate having an array of photodiodes, an array of microlenses formed over the array of photodiodes, and an array of color filter elements interposed between the array of microlenses and the array of photodiodes. The color filter elements may be separated from each other by color filter barriers. Each color filter barrier may include an upper portion formed from dielectric material and a lower portion formed from metal. The metal portion of each color filter barrier may form a crosstalk reduction structure that prevents stray light from passing from one pixel to an adjacent pixel. The color filter barriers may have a grid shape with an array of openings. The color filter elements may be deposited in the openings.

What is claimed is: 
     
         1 . An image sensor having an array of image pixels, comprising:
 a substrate;   an array of photodiodes formed in the substrate;   an array of microlenses formed over the array of photodiodes; and   an array of color filter elements interposed between the array of microlenses and the array of photodiodes, wherein the array of color filter elements comprises a plurality of color filter barriers, wherein each of the color filter barriers is interposed between an associated pair of color filter elements in the array of color filter elements, and wherein each of the color filter barriers comprises metal.   
     
     
         2 . The image sensor defined in  claim 1  wherein the array of color filter elements comprises red color filter elements, green color filter elements, blue color filter elements, and clear color filter elements. 
     
     
         3 . The image sensor defined in  claim 1  wherein each of the color filter barriers comprises a dielectric portion and wherein the metal is interposed between the dielectric portion and the substrate. 
     
     
         4 . The image sensor defined in  claim 3  wherein the metal comprises titanium nitride. 
     
     
         5 . The image sensor defined in  claim 4  wherein the dielectric material comprises silicon dioxide. 
     
     
         6 . The image sensor defined in  claim 1  wherein the plurality of color filter barriers has a grid shape with an array of openings and wherein the color filter elements are located in the openings. 
     
     
         7 . The image sensor defined in  claim 1  further comprising an anti-reflective coating on a surface of the substrate, wherein the anti-reflective coating is interposed between the array of color filter elements and the array of photodiodes. 
     
     
         8 . A method for forming a color filter array, comprising:
 depositing a layer of metal onto an image sensor substrate;   depositing a layer of dielectric material onto the layer of metal;   etching an array of openings into the layer of metal and the layer of dielectric material; and   depositing a color filter element into each of the openings.   
     
     
         9 . The method defined in  claim 8  wherein depositing the layer of metal onto the image sensor substrate comprises depositing titanium nitride onto the image sensor substrate. 
     
     
         10 . The method defined in  claim 9  wherein depositing the layer of dielectric material on the layer of metal comprises depositing silicon dioxide onto the layer of metal. 
     
     
         11 . The method defined in  claim 8  wherein etching the array of openings into the metal layer and the dielectric layer comprises etching the array of openings into the metal layer and the dielectric layer to form a grid of color filter barriers, wherein each of the color filter barriers comprises a portion of the layer of metal and a portion of the layer of dielectric material. 
     
     
         12 . The method defined in  claim 11  wherein depositing the color filter element into each of the openings comprises depositing red color filter elements, green color filter elements, blue color filter elements, and clear color filter elements into associated openings in the array of openings. 
     
     
         13 . The method defined in  claim 8  further comprising covering portions of the layer of dielectric material with a masking material, wherein etching the array of openings into the layer of metal and the layer of dielectric material comprises removing portions of the layer of metal and the layer of dielectric material that are not covered by the masking material. 
     
     
         14 . The method defined in  claim 13  wherein covering portions of the layer of dielectric material with the masking material comprises covering a grid-shaped portion of the layer of dielectric material with a hardmask. 
     
     
         15 . The method defined in  claim 8  wherein the image sensor substrate is coated with an anti-reflective coating and wherein depositing the layer of metal onto the image sensor substrate comprises depositing the layer of metal over the anti-reflective coating. 
     
     
         16 . A system, comprising:
 a central processing unit;   memory;   input-output circuitry; and   an imaging device, wherein the imaging device comprises an image sensor having an array of image pixels and wherein the image sensor comprises:
 a substrate; 
 an array of photodiodes formed in the substrate; 
 an array of microlenses formed over the array of photodiodes; and 
 an array of color filter elements interposed between the array of microlenses and the array of photodiodes, wherein the array of color filter elements comprises a plurality of color filter barriers, wherein each of the color filter barriers is interposed between an associated pair of color filter elements in the array of color filter elements, and wherein each of the color filter barriers comprises metal. 
   
     
     
         17 . The system defined in  claim 16  wherein each of the color filter barriers comprises a dielectric portion and wherein the metal is interposed between the dielectric portion and the substrate. 
     
     
         18 . The system defined in  claim 17  wherein the metal comprises titanium nitride and wherein the dielectric material comprises silicon dioxide. 
     
     
         19 . The system defined in  claim 16  wherein the plurality of color filter barriers has a grid shape with an array of openings and wherein the color filter elements are located in the openings. 
     
     
         20 . The system defined in  claim 16  further comprising an anti-reflective coating on a surface of the substrate, wherein the anti-reflective coating is interposed between the array of color filter elements and the array of photodiodes.