Apparatus and method for reducing optical cross-talk in image sensors

Abstract

An image sensor device includes a semiconductor substrate having a front surface and a back surface; an array of pixels formed on the front surface of the semiconductor substrate, each pixel being adapted for sensing light radiation; an array of color filters formed over the plurality of pixels, each color filter being adapted for allowing a wavelength of light radiation to reach at least one of the plurality of pixels; and an array of micro-lens formed over the array of color filters, each micro-lens being adapted for directing light radiation to at least one of the color filters in the array. The array of color filters includes structure adapted for blocking light radiation that is traveling towards a region between adjacent micro-lens.

1 . An image sensor device, comprising:
 a semiconductor substrate having a front surface and a back surface;   a plurality of pixels formed on the front surface of the semiconductor substrate, each pixel being adapted for sensing light radiation;   an array of color filters formed over the plurality of pixels, each color filter being adapted for allowing a wavelength of light radiation to reach at least one of the plurality of pixels; and   a plurality of micro-lens formed over the array of color filters, each micro-lens being adapted for directing light radiation to at least one of the color filters in the array;   wherein the array of color filters further includes a structure adapted for blocking light radiation that is traveling towards a region between adjacent micro-lens.   
   
   
       2 . The device of  claim 1 , wherein the array of color filters is formed over the back surface of the substrate. 
   
   
       3 . The device of  claim 2 , wherein the structure includes a black photoresist disposed in a space between adjacent color filters in the array. 
   
   
       4 . The device of  claim 3 , further comprising a planarization layer formed between the back surface of the substrate and the array of color filters. 
   
   
       5 . The device of  claim 1 , wherein the structure includes a planatization layer having a transparent portion and an opaque portion, the planarization layer being disposed between the back surface of the substrate and a bottom surface of the array of color filters, the opaque portion being disposed underneath an area between adjacent color filters. 
   
   
       6 . The device of  claim 5 , wherein the opaque portion includes a black photoresist. 
   
   
       7 . The device of  claim 5 , wherein the transparent portion is one of a silicon oxide, a silicon nitride, a silicon oxynitride, or combinations thereof. 
   
   
       8 . The device of  claim 1 , wherein the structure has a width that is equal to about 0.2 μm. 
   
   
       9 . The device of  claim 1 , further comprising:
 a plurality of interconnect metal layers formed over the front surface of the substrate; and   an inter-metal dielectric disposed between each of the plurality of metal layers.   
   
   
       10 . A method for making an image sensor device, comprising:
 providing a semiconductor substrate having a front surface and a back surface;   forming a plurality of pixels on the front surface of the semiconductor substrate, each pixel being adapted for sensing light radiation;   forming an array of color filters over the plurality of pixels, each color filter being adapted for allowing a wavelength of light radiation to reach at least one of the plurality of pixels; and   forming a plurality of micro-lens over the array of color filters, each micro-lens being adapted for directing light radiation to at least one of the color filters in the array;   wherein the forming the array of color filters further includes forming the array of color filters with a structure adapted for blocking light radiation traveling towards a region between adjacent micro-lens.   
   
   
       11 . The method of  claim 10 , wherein the forming the array of color filters with the structure includes:
 forming a planarization layer on the back surface of the substrate;   patterning the planarization layer to define a space within the planarization layer;   forming a layer of an opaque material over the patterned planarization layer;   etching back the opaque material until the planarization layer is exposed; and   forming a color filter layer over the planarization layer such that the space filled with the opaque material is disposed underneath an area between adjacent color filters.   
   
   
       12 . The method of  claim 11 , wherein the forming the layer of opaque material includes forming a layer of a black photoresist. 
   
   
       13 . The method of  claim 10 , wherein the forming the array of color filters with the structure includes:
 forming a planarization layer on the back surface of the substrate;   forming a color filter layer over the planarization layer;   patterning the color filter layer to define a space between adjacent color filters;   forming a layer of an opaque material over the patterned color filter layer; and   etching back the opaque material until the color filter layer is exposed.   
   
   
       14 . The method of  claim 13 , wherein the forming the layer of the opaque material includes forming a layer of a black photoresist. 
   
   
       15 . The method of  claim 10 , further comprising:
 forming a plurality of metal layers over the front surface of the substrate; and   forming an intermetal dielectric between each of the plurality of metal layers.   
   
   
       16 . A semiconductor device, comprising:
 a substrate having a front surface and a back surface;   a plurality of pixels formed on the front surface of the substrate, each pixel being adapted to sense light radiation directed towards the back surface of the substrate;   an array of color filters formed over the back surface of the substrate, each color filter being aligned with one of the plurality of pixels for allowing a wavelength of light radiation to pass through to the one of the plurality of pixels;   a plurality of micro-lens formed over the array of color filters, each micro-lens being adapted to direct light radiation to each color filter in the array; and   a blocking structure disposed between the back surface of the substrate and the plurality of micro-lens, the blocking structure being adapted to block light radiation traveling towards a region between adjacent micro-lens from reaching the pixels.   
   
   
       17 . The device of  claim 16 , wherein the blocking structure includes a black photoresist disposed in a region between adjacent color filters. 
   
   
       18 . The device of  claim 16 , wherein the blocking structure includes a planarization layer formed between the back surface of the substrate and a bottom surface of the array of color filters, the planarization layer having a black photoresist disposed underneath an area between adjacent color filters. 
   
   
       19 . The device of  claim 16 , wherein the wavelength of light is one of a red light, a green light, and a blue light. 
   
   
       20 . The device of  claim 19 , wherein each pixel includes a photodiode and at least one transistor.