Method of Fabricating CMOS Image Sensor

Abstract

A method of fabricating a CMOS image sensor is disclosed that enhances device robustness. The method includes the steps of forming a metal pad on a pad area of a substrate, forming a planarizing layer on the substrate including the metal pad, removing a portion of the planarizing layer to open a surface of the metal pad, forming a protective layer over the substrate including the metal pad, coating a color filter resist layer on the protective layer and selectively exposing the color filter resist layer, coating a microlens resist layer on the color filter resist layer and selectively exposing the microlens resist layer, developing the exposed color filter and microlens resist layers, forming a pad opening by selectively removing the protective layer to open a surface of the metal, and reflowing the microlens pattern.

1 . An image sensor, comprising:
 a substrate having an active area and a pad area;   a metal pad in the pad area;   a planarizing layer in the active area of the substrate;   a color filter layer over the planarizing layer;   a microlens pattern comprising a plurality of microlenses, each microlens in direct contact with a corresponding color filter in the color filter layer.   
   
   
       2 . The image sensor of  claim 1 , wherein the metal pad has a thickness equal to or greater than the planarizing layer. 
   
   
       3 . The image sensor of  claim 1 , further comprising a protective layer on the substrate and the metal pad. 
   
   
       4 . The image sensor of  claim 3 , wherein the protective layer is on at least the active area of the substrate. 
   
   
       5 . The image sensor of  claim 3 , further comprising a pad opening in the protective layer exposing a surface of the metal pad. 
   
   
       6 . The image sensor of  claim 1 , further comprising one or more signal lines corresponding to or communicating with a plurality of gate electrodes. 
   
   
       7 . The image sensor of  claim 6 , wherein the metal pad and the signal lines comprise a same material. 
   
   
       8 . The image sensor of  claim 1 , wherein the metal pad comprises aluminum. 
   
   
       9 . The image sensor of  claim 1 , wherein the substrate comprises image sensor elements formed therein. 
   
   
       10 . The image sensor of  claim 9 , wherein the image sensor elements comprise a plurality of photodiodes. 
   
   
       11 . The image sensor of  claim 10 , wherein the color filters align with the photodiodes. 
   
   
       12 . The image sensor of  claim 11 , wherein the photodiodes are configured to receive illumination radiating through the color filters. 
   
   
       13 . The image sensor of  claim 3 , wherein the protective layer comprises an oxide or a nitride. 
   
   
       14 . The image sensor of  claim 13 , wherein the protective layer comprises a doped oxide. 
   
   
       15 . The image sensor of  claim 3 , wherein the protective layer has a thickness of from 300 to 800 Å. 
   
   
       16 . The image sensor of  claim 3 , wherein the protective layer has a thickness of from 300 to 500 Å. 
   
   
       17 . The image sensor of  claim 1 , wherein the microlens pattern comprises a same resist material as the color filter layer. 
   
   
       18 . The image sensor of  claim 1 , wherein the microlens pattern comprises a different resist material as the color filter layer. 
   
   
       19 . The image sensor of  claim 3 , wherein an upper surface of the protective layer is planarized.