Image sensor having large micro-lenses at the peripheral regions

Abstract

An image sensor includes an array of pixels formed in a semiconductor substrate. The pixels are grouped as a center portion of pixels and an outer portion of pixels. A first set of micro-lenses is formed over each of the pixels in the center portion of pixels. A second set of micro-lenses is formed over each of the pixels in the outer portion of pixels. The second set of micro-lenses differ from said first set of micro-lenses. In one embodiment, the second set of micro-lenses are taller than the first set of micro-lenses.

I claim:  
     
         1 . An image sensor comprising: 
 a plurality of pixels formed in a semiconductor substrate, each pixel including a light sensitive element, said pixels grouped as a center portion of pixels and an outer portion of pixels;    a first set of micro-lenses formed over each of said pixels in said center portion of pixels; and    a second set of micro-lenses formed over each of said pixels in said outer portion of said pixels,    wherein said second set of micro-lenses differ from said first set of micro-lenses.    
     
     
         2 . The image sensor of  claim 1  further including a color filter formed over each pixel, said color filter formed between said micro-lens and said light sensitive element.  
     
     
         3 . The image sensor of  claim 1  further including a color filter formed over each pixel, said color filter formed over said micro-lens.  
     
     
         4 . The image sensor of  claim 1  wherein the second set of micro-lenses are taller than said first set of micro-lenses.  
     
     
         5 . The image sensor of  claim 1  wherein the second set of micro-lenses are larger than said first set of micro-lenses.  
     
     
         6 . The image sensor of  claim 1  wherein said micro-lenses are formed from either polymethylmethacrylate (PMMA) or polyglycidylmethacrylate (PGMA).  
     
     
         7 . The image sensor of  claim 1  further including an imaging lens coupled to said image sensor.  
     
     
         8 . A method for forming an image sensor comprising: 
 forming a plurality of pixels in a semiconductor substrate, each pixel including a light sensitive element, said pixels grouped as a center portion of pixels and an outer portion of pixels;    forming a first set of micro-lenses over each of said pixels in said center portion of pixels; and    forming a second set of micro-lenses over each of said pixels in said outer portion of said pixels,    wherein said second set of micro-lenses differ from said first set of micro-lenses.    
     
     
         9 . The method of  claim 8  further including forming a color filter over each pixel, said color filter formed between said micro-lens and said light sensitive element.  
     
     
         10 . The method of  claim 8  further including forming a color filter over each pixel, said color filter formed over said micro-lens.  
     
     
         11 . The method of  claim 8  wherein the second set of micro-lenses are taller than said first set of micro-lenses.  
     
     
         12 . The method of  claim 8  wherein the second set of micro-lenses are larger than said first set of micro-lenses.  
     
     
         13 . The method of  claim 8  wherein said micro-lenses are formed from either polymethylmethacrylate (PMMA) or polyglycidylmethacrylate (PGMA).  
     
     
         14 . The method of  claim 8  further including coupling an imaging lens to said image sensor.  
     
     
         15 . A method for forming an image sensor comprising: 
 forming a plurality of pixels in a semiconductor substrate, each pixel including a light sensitive element, said pixels grouped as a center portion of pixels and an outer portion of pixels;    forming a micro-lens material over said plurality of pixels, wherein said micro-lens material is a photoresist;    exposing said micro-lens material with a first reticle mask to generate gap sections in said micro-lens material;    exposing said micro-lens material with a second reticle mask to generate top portions in said micro-lens material located in said center portion of pixels;    developing said micro-lens material to remove said top portions and said gap sections;    reflowing said micro-lens material to form a first set of micro-lenses over each of said pixels in said center portion of pixels and a second set of micro-lenses over each of said pixels in said outer portion of said pixels,    wherein said second set of micro-lenses differ from said first set of micro-lenses.    
     
     
         16 . The method of  claim 15  further including forming a color filter over each pixel, said color filter formed between said micro-lens and said light sensitive element.  
     
     
         17 . The method of  claim 15  further including forming a color filter over each pixel, said color filter formed over said micro-lens.  
     
     
         18 . The method of  claim 15  wherein the second set of micro-lenses are taller than said first set of micro-lenses.  
     
     
         19 . The method of  claim 15  wherein the second set of micro-lenses are larger than said first set of micro-lenses.  
     
     
         20 . The method of  claim 15  wherein said micro-lens material is either polymethylmethacrylate (PMMA) or polyglycidylmethacrylate (PGMA).