Alternate method for photodiode formation in CMOS image sensors

Abstract

A complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) having a plurality of pixels which includes at least one pixel entailing a photodetector, a transistor adjacent the photodetector having a silicide surface, and an insulator over the photodetector. The insulator has a thickness sufficient to prevent the silicide surface from forming over the photodetector and contains an insulator as a field oxide.

What is claimed is:  
     
         1 . A method of forming a complementary metal oxide semiconductor (CMOS) pixel sensor comprising: 
 supplying a substrate;    doping a first region of said substrate to form a photodetector;    forming a transistor adjacent said photodetector, said forming of said transistor including forming an insulator, wherein said insulator covers said photodetector; and    siliciding conductive regions of said transistor, wherein said inculator prevents said photodetector from being silicided.    
     
     
         2 . The method in  claim 1 , wherein said insulator comprises a field oxide.  
     
     
         3 . The method in  claim 1 , wherein said photodetector comprises a pinned photodiode and said method further comprises, before forming said insulator, forming a pinning layer over said photodetector.  
     
     
         4 . The method in  claim 1 , wherein said doping of said first region is performed after said insulator is formed and is performed through said insulator.  
     
     
         5 . The method in  claim 1 , wherein said transistor comprises a reset transistor and said method further comprises: 
 forming a silicided source region adjacent said photodetector;    forming a silicided gate adjacent said source region; and    forming a silicided drain region on an opposite side of said gate from said source.    
     
     
         6 . The method in  claim 1 , wherein said transistor comprises a transfer transistor and said method further comprises: 
 forming a silicided source region adjacent said photodetector;    forming a silicided gate adjacent said source region; and    forming a silicided drain region on an opposite side of said gate from said source.    
     
     
         7 . The method in  claim 1 , wherein said transistor comprises a row select transistor and said method further comprises; 
 forming a silicided gate adjacent said photodetector; and    forming a silicided drain region on an opposite side of said gate from said photodetector.