Back side illumination image sensor and a process thereof

Abstract

A process and structure of a backside illumination (BSI) image sensor are disclosed. An n-type doped region is formed in a substrate, and a transfer gate is formed on top of the semiconductor substrate. A p-type doped region is formed in the n-type doped region either using the transfer gate as a mask or is non-self aligned formed.

1 . A process of forming a back side illumination (BSI) image sensor, comprising:
 forming an n-type doped region in a semiconductor substrate;   forming a transfer gate on the semiconductor substrate, therefore resulting in an overlap between one end of the transfer gate and the n-type doped region; and   forming a p-type doped region in the n-type doped region using the transfer gate as a mask.   
     
     
         2 . The process of  claim 1 , before forming the n-type doped region, further comprising a step of forming a transfer gate channel implant in the semiconductor substrate. 
     
     
         3 . The process of  claim 1 , wherein the n-type doped region is an n-type implant, and the p-type doped region is a p-type implant. 
     
     
         4 . The process of  claim 1 , wherein the transfer gate is a polysilicon gate. 
     
     
         5 . The process of  claim 1 , after forming the transfer gate, further comprising a step of forming a spacer on a sidewall of the transfer gate. 
     
     
         6 . The process of  claim 1 , further comprising a step of forming a floating diffusion in the semiconductor substrate, the floating diffusion being near another end of the transfer gate. 
     
     
         7 . A process of forming a back side illumination BC image sensor, comprising:
 forming a transfer gate channel implant in a semiconductor substrate;   forming an n-type doped region in the semiconductor substrate;   forming a p-type doped region in the n-type doped region; and   forming a transfer gate on the semiconductor substrate to substantially cover the n-type doped region and the p-type doped region.   
     
     
         8 . The process of  claim 7 , after forming the transfer gate, further comprising a step of forming a spacer on a sidewall of the transfer gate.