Silicon substrate with reduced surface roughness

Abstract

The present disclosure provides a method for fabricating a semiconductor device including providing a semiconductor substrate comprising a first surface and a second surface, wherein at least one imaging sensor is located adjacent the first surface, activating a dopant layer in the semiconductor substrate adjacent the second surface using a localized annealing process, and etching the dopant layer.

What is claimed is: 
     
       1. A method for fabricating a backside illuminated imaging sensor, comprising:
 providing a semiconductor substrate having a first surface and a second surface; 
 forming a plurality of imaging sensors on the first surface; and  
 forming a positive type dopant layer on the second surface;, wherein forming the positive type dopant layer on the second surface includes activating the positive type dopant on the second surface with a localized annealing process. 
 forming a plurality of color filters on the positive type dopant layer; and 
 forming a plurality of micro lenses adjacent the color filters. 
 
     
     
       2. The method of  claim 1 , further comprising etching the second surface to provide a surface roughness on the second surface of less than approximately 20 Angstroms. 
     
     
       3. The method of  claim 1 , further comprising:
 forming a multi layer interconnect on the first surface adjacent the plurality of imaging sensors. 
 
     
     
       4. The method of  claim 1 , further comprising etching the second surface with wet chemical etching. 
     
     
       5. The method of  claim 4 , wherein the wet chemical etching comprises etching with an alkaline solution of ammonia water and aqueous amine. 
     
     
       6. The method of  claim 4 , wherein the wet chemical etching comprises etching with an etchant chosen from the group consisting of Tetra-methyl ammonium hydroxide (TMAH), ethylenediamene pyrocatecol (EDP), and an Alkali Hydroxide (Alkali-OH). 
     
     
       7. A backside illuminated semiconductor device, comprising:
 a semiconductor substrate having a first surface and a second surface; 
 a plurality of imaging sensors formed in the semiconductor substrate adjacent the first surface; 
 a positive type dopant layer formed in the semiconductor substrate adjacent the second surface, wherein the positive type dopant layer comprises a thickness between approximately 500 to 5000 Angstroms; and  
 a plurality of color filters formed adjacent directly on the positive type dopant layer; and. 
 a plurality of micro lenses formed adjacent the color filters. 
 
     
     
       8. The device of  claim 7 , wherein the positive type dopant layer is fabricated by a process comprising:
 activating a P+ ion implant layer with a localized annealing process; and 
 etching the P+ ion implant layer. 
 
     
     
       9. The device of  claim 8 , wherein the second surface has a surface roughness of less than approximately 20 Angstroms. 
     
     
       10. The method of  claim 1 , wherein the forming of the positive type dopant layer on the second surface includes:
 forming an ion implant layer in the semiconductor substrate; and 
 locally annealing the ion implant layer. 
 
     
     
       11. The method of claim  1  15, wherein the forming of the plurality of micro lenses is carried out so that the micro lenses are on a side of the color filters opposite from the positive type dopant layer. 
     
     
       12. The method of  claim 1 , further comprising etching the second surface, wherein the etching reduces a roughness of the second surface. 
     
     
       13. The device of claim  7  16, wherein the micro lenses are disposed on a side of the color filters opposite from the positive type dopant layer. 
     
     
       14. The device of  claim 7 , wherein the second surface has a surface roughness of less than approximately 20 Angstroms. 
     
     
       15. The method of claim 1, further comprising:
 forming a plurality of color filters on the positive type dopant layer; and   forming a plurality of micro lenses adjacent the color filters.   
     
     
       16. The backside illuminated semiconductor device of claim 7, further comprising:
 a plurality of micro lenses formed adjacent the color filters.