Light guide array for an image sensor

Abstract

An image sensor pixel that includes a photoelectric conversion unit supported by a substrate and an insulator adjacent to the substrate. The pixel includes a cascaded light guide located within an opening of the insulator. The cascaded light guide may include a color filter having an air gap between adjacent color filters that is sealed from above by a transparent sealing film having a concave surface over the air gap to diverge light crossing into the air gap from the concave surface into adjacent color filters. A portion of a support wall between a pair of color filters may have a larger width above than below to form a necking to hold down the color filters for better retention.

What is claimed is: 
     
         1 . A method for fabricating an image sensor pixel of an image sensor pixel array supported by a substrate, comprising:
 forming a lower transparent light guide above the substrate;   forming a support film above the lower transparent light guide;   forming an opening in the support film; and   forming an upper transparent light guide in the opening,   wherein a vertical centerline of the lower transparent light guide is offset from a vertical centerline of the opening laterally, and   wherein the image sensor pixel is in a corner of the image sensor pixel array.   
     
     
         2 . The method of  claim 1 , wherein the upper and lower transparent light guides are symmetric about their respective vertical centerlines. 
     
     
         3 . The method of  claim 1 , wherein the upper transparent light guide is offset relative to the lower transparent light guide to be further away from a center of the image sensor pixel array. 
     
     
         4 . The method of  claim 3 , wherein the upper and lower transparent light guides are symmetric about their respective vertical centerlines. 
     
     
         5 . The method of  claim 1 , further comprising:
 forming an insulating layer on the substrate, the lower transparent light guide being formed in the insulating layer and between a plurality of wires embedded in the insulating layer.   
     
     
         6 . The method of  claim 5 , wherein a protection film is formed on the insulating layer during the forming of the lower transparent light guide. 
     
     
         7 . The method of  claim 5 , further comprising:
 forming a protection film on the insulating layer between the forming of the lower light guide and the forming of the support film.   
     
     
         8 . The method of  claim 1 , further comprising:
 forming a color filter in the opening.   
     
     
         9 . The method of  claim 8 , further comprising:
 removing a portion of the support film that laterally adjoins the color filter.   
     
     
         10 . An image sensor pixel of an image sensor pixel array, comprising:
 a substrate;   a photoelectric conversion unit supported by the substrate;   a lower transparent light guide arranged to transmit a light to the photoelectric conversion unit; and,   an upper transparent light guide arranged to transmit the light to the lower transparent light guide,   wherein vertical centerlines of the upper and lower transparent light guides are mutually offset laterally,   wherein the image sensor pixel is in a corner of the image sensor pixel array.   
     
     
         11 . The image sensor pixel of  claim 10 , wherein the upper transparent light guide is offset relative to the lower transparent light guide to be further away from a center of the image sensor pixel array. 
     
     
         12 . The image sensor pixel of  claim 10 , wherein the upper and lower transparent light guides are symmetric about their respective vertical centerlines. 
     
     
         13 . The image sensor pixel of  claim 10 , further comprising:
 an insulating layer on the substrate, the lower transparent light guide being disposed in the insulating layer between a plurality of wires; and   a protection film for sealing the insulating layer against moisture.   
     
     
         13 . The image sensor pixel of  claim 15 , wherein the protection film comprises a silicon nitride. 
     
     
         14 . A method of detecting an image using a plurality of photoelectric conversion units arranged in a two-dimensional array supported by a substrate, comprising:
 providing an upper transparent light guide for each photoelectric conversion unit;   providing a lower transparent light guide to receive a light from the upper light guide and transmit the light to said each photoelectric conversion unit,   wherein a vertical centerline of the lower transparent light guide is offset from a vertical centerline of the upper transparent light guide laterally where the upper transparent light guide is in a corner of the two-dimensional array.   
     
     
         15 . The method of  claim 14 , wherein the upper and lower transparent light guides are symmetric about their respective vertical centerlines. 
     
     
         16 . The method of  claim 14 , wherein the upper transparent light guide is offset relative to the lower transparent light guide to be further away from a center of the two-dimensional array. 
     
     
         17 . The method of  claim 16 , wherein the upper and lower transparent light guides are symmetric about their respective vertical centerlines. 
     
     
         18 . The method of  claim 14 , wherein the lower transparent light guide is disposed in an insulating layer covering the substrate, the method further comprising:
 sealing the insulating layer from moisture by means of a protection film.   
     
     
         19 . The method of  claim 18 , wherein the protection film comprises a silicon nitride.