Image sensor grid and method of fabrication of same

Abstract

An image sensor includes a substrate, a grid, and a color filter. The grid is over the substrate. From a cross-sectional view, the grid includes a first grid and a second grid over the first grid, the first grid has lower portion that has a first sidewall and a second sidewall opposing the first sidewall, the second grid has a third sidewall and a fourth sidewall opposing the third sidewall, and a width between the third sidewall and the fourth sidewall is less than a width between the first sidewall and the second sidewall. The color filter extends through the grid structure.

What is claimed is: 
     
         1 . An image sensor, comprising:
 a substrate;   a grid structure over the substrate, wherein from a cross-sectional view, the grid structure comprises:
 a first grid having a lower portion that has a first sidewall and a second sidewall opposing the first sidewall; and 
 a second grid over the first grid, the second grid having a third sidewall and a fourth sidewall opposing the third sidewall, wherein a distance between the third sidewall and the fourth sidewall is less than a distance between the first sidewall and the second sidewall; and 
   a color filter extending through the grid structure.   
     
     
         2 . The image sensor of  claim 1 , wherein from the cross-sectional view, the first grid of the grid structure has an upper portion that has a fifth sidewall and a sixth sidewall opposing the fifth sidewall, and a distance between the fifth sidewall and the sixth sidewall decreases as a distance from the substrate increases. 
     
     
         3 . The image sensor of  claim 1 , wherein from the cross-sectional view, the first grid of the grid structure has an upper portion, and a top end of the upper portion of the first grid has a narrower width than a bottom end of the upper portion of the first grid. 
     
     
         4 . The image sensor of  claim 3 , wherein from the cross-sectional view, the top end of the upper portion of the first grid has a same width as a bottom end of the second grid, and the bottom end of the upper portion of the first grid has a same width as a top end of the lower portion of the first grid. 
     
     
         5 . The image sensor of  claim 3 , wherein from the cross-sectional view, the top end of the upper portion of the first grid has a narrower width than a top end of the lower portion of the first grid. 
     
     
         6 . The image sensor of  claim 3 , wherein from the cross-sectional view, the bottom end of the upper portion of the first grid has a wider width than a bottom end of the second grid. 
     
     
         7 . The image sensor of  claim 3 , wherein from the cross-sectional view, the upper portion of the first grid has a trapezoidal profile. 
     
     
         8 . The image sensor of  claim 1 , wherein from the cross-sectional view, the lower portion of the first grid has a rectangular profile. 
     
     
         9 . The image sensor of  claim 1 , wherein from the cross-sectional view, the second grid has a rectangular profile. 
     
     
         10 . The image sensor of  claim 1 , wherein the first grid is made of a different material than the second grid. 
     
     
         11 . An image sensor, comprising:
 a substrate;   first gridlines over the substrate, the first gridlines each comprising a lower portion having a vertical sidewall and an upper portion having a width that decreases as a distance from the lower portion increases;   second gridlines over the first gridlines, wherein from a cross-sectional view, each of the second gridlines has a narrower width than the lower portions of the first gridlines; and   a color filter extending through the first and second gridlines.   
     
     
         12 . The image sensor of  claim 11 , wherein from the cross-sectional view, the upper portions of the first gridlines each has a top end having a same width as bottom ends of the second gridlines, and a bottom end having a same width as top ends of the lower portions of the first gridlines. 
     
     
         13 . The image sensor of  claim 11 , wherein the second gridlines are made of a different material than the first gridlines. 
     
     
         14 . The image sensor of  claim 11 , further comprising:
 an antireflective coating between the substrate and the first gridlines.   
     
     
         15 . The image sensor of  claim 11 , further comprising:
 microlenses over the color filter and the first and second gridlines.   
     
     
         16 . An image sensor, comprising:
 a substrate;   a first grid pattern over the substrate, wherein from a cross-sectional view, the first grid pattern has an upper portion having a first sidewall and a second sidewall opposing the first sidewall, and a distance between the first sidewall and the second sidewall decreases as a distance from the substrate increases;   a second grid pattern over the first grid pattern, wherein from the cross-sectional view, a top end of the second grid pattern has a narrower width than a bottom end of the upper portion of the first grid pattern; and   a color filter extending through the first and second grid patterns.   
     
     
         17 . The image sensor of  claim 16 , wherein the first grid pattern has a lower portion, and a top end of the lower portion of the first grid pattern has a same width as a bottom end of the upper portion of the first grid pattern. 
     
     
         18 . The image sensor of  claim 17 , wherein from the cross-sectional view, a bottom end of the lower portion of the first grid pattern has a wider width than a top end of the upper portion of the first grid pattern. 
     
     
         19 . The image sensor of  claim 16 , wherein from the cross-sectional view, a bottom end of the second grid pattern has a narrower width than the bottom end of the upper portion of the first grid pattern. 
     
     
         20 . The image sensor of  claim 16 , wherein the second grid pattern is made of a different material than the first grid pattern.