Bottom antireflection coating color filter process for fabricating solid state image sensors

Abstract

An image sensor system and methods of making such a system are described. The image sensor system includes a color filter array that is formed by a color filter process that incorporates a bottom antireflection coating. The bottom antireflection coating forms a protective layer that protects exposed areas of the active image sensing device structure during formation of the color filter array and, thereby, preserves the intrinsic transmission characteristics of the active image sensing device structure. The bottom antireflection coating also reduces degradation of metal structures (e.g., bonding pads) and pixel edges at the exposed surface of the active image sensing device structure. In addition, the bottom antireflection coating provides a reliable adhesive surface for the color filter array, substantially eliminating lifting of the color filter array resist structures. In some embodiments, the bottom antireflection coating also improves the optical transmission characteristics of one or more colors of the colors filter array.

What is claimed is:  
     
         1 . A method of fabricating an image sensor, comprising: 
 forming a bottom antireflection coating over an exposed surface of an active image sensing device structure;    forming a color filter array on the bottom antireflection coating; and    substantially removing exposed portions of the bottom antireflection coating.    
     
     
         2 . The method of  claim 1 , wherein the bottom antireflection coating comprises a dyed organic film-forming material.  
     
     
         3 . The method of  claim 1 , wherein the bottom antireflection coating comprises a light-absorbing polymeric film-forming material.  
     
     
         4 . The method of  claim 1 , wherein the bottom antireflection coating has a thickness selected to improve an optical transmission characteristic of one or more colors of the color filter array.  
     
     
         5 . The method of  claim 1 , wherein the bottom antireflection coating is substantially transmissive to radiation in a wavelength range of about 400 nm to about 700 nm.  
     
     
         6 . The method of  claim 1 , wherein the color filter array comprises a plurality of colored photoresist structures.  
     
     
         7 . The method of  claim 1 , wherein exposed portions of the bottom antireflection coating are removed substantially by a plasma etch process.  
     
     
         8 . The method of  claim 7 , wherein the plasma etch process is a low-power buffered oxygen ash process.  
     
     
         9 . The method of  claim 7 , wherein the plasma etch process removes the bottom antireflection coating at a substantially higher etch rate than the color filter array.  
     
     
         10 . The method of  claim 1 , wherein the bottom antireflection coating forms a substantially continuous layer over the exposed surface of the active image sensing device structure before exposed portions of the bottom antireflection coating are substantially removed.  
     
     
         11 . The method of  claim 1 , wherein the bottom antireflection coating forms a protective barrier over metal structures at the exposed surface of the active image sensing device structure during formation of the color filter array.  
     
     
         12 . The method of  claim 1 , wherein the active image sensor device structure comprises a complementary metal-oxide-semiconductor (CMOS) image sensor.  
     
     
         13 . An image sensor system, comprising: 
 an active image sensing device structure;    a color filter array; and    a bottom antireflection coating disposed between the color filter array and a surface of the active image sensing device structure.    
     
     
         14 . The system of  claim 13 , wherein the bottom antireflection coating comprises a dyed organic film-forming material.  
     
     
         15 . The system of  claim 13 , wherein the bottom antireflection coating comprises a light-absorbing polymeric film-forming material.  
     
     
         16 . The system of  claim 13 , wherein the bottom antireflection coating has a thickness selected to improve an optical transmission characteristic of one or more colors of the color filter array.  
     
     
         17 . The system of  claim 13 , wherein the bottom antireflection coating is substantially transmissive to radiation in a wavelength range of about 400 nm to about 700 nm.  
     
     
         18 . The system of  claim 13 , wherein the color filter array comprises a plurality of colored photoresist structures.  
     
     
         19 . The system of  claim 13 , wherein the bottom antireflection coating has a substantially higher plasma etch rate than the color filter array.  
     
     
         20 . The system of  claim 13 , wherein the active image sensor device structure comprises a complementary metal-oxide-semiconductor (CMOS) image sensor.