Isolation process and structure for CMOS imagers
View Patent ↗A barrier implanted region of a first conductivity type formed in lieu of an isolation region of a pixel sensor cell that provides physical and electrical isolation of photosensitive elements of adjacent pixel sensor cells of a CMOS imager. The barrier implanted region comprises a first region having a first width and a second region having a second width greater than the first width, the second region being located below the first region. The first region is laterally spaced from doped regions of a second conductivity type of adjacent photodiodes of pixel sensor cells of a CMOS imager.
1. A method of forming pixel sensor cells, said method comprising:
providing a first doped layer of a first conductivity type in a substrate;
forming at least one barrier implanted isolation region in said doped layer to isolate said pixel sensor cells, said barrier implanted isolation region comprising a first well region of a first width and a second well region of a second width greater than the first width, the second well region being located below and in contact with the first well region;
forming at least two charge collection regions of a second conductivity type in said first doped layer, said charge collection regions being adjacent said barrier implanted isolation region; and
forming at least two second doped layers of said first conductivity type in said substrate above each of said charge collection regions.
2. The method of claim 1 , wherein said first doped layer is a p-type epitaxial layer.
3. The method of claim 1 , wherein said first well region is formed to a width of less than about 0.4 microns.
4. The method of claim 3 , wherein said first well region is formed to a width of less than about 0.2 microns.
5. The method of claim 1 , wherein said second well region is formed to a width of about 0.6 to about 1.2 microns.
6. The method of claim 5 , wherein said second well region is formed to a width of about 0.8 microns.
7. The method of claim 1 , wherein said first well region is formed to a thickness of about 0.5 to about 2 microns.
8. The method of claim 7 , wherein said first well region is formed to a thickness of about 1 micron.
9. The method of claim 1 , wherein said second well region is formed to a thickness of about 1.5 to about 12.0 microns.
10. The method of claim 9 , wherein said second well region is formed to a thickness of about 5 microns.
11. The method of claim 1 , wherein said first well region is doped with a p-type dopant at a dopant concentration of from about 5×10 11 to about 5×10 13 atoms per cm 2 .
12. The method of claim 11 , wherein said first well region is doped with a p-type dopant at a dopant concentration of about 1×10 12 to about 5×10 12 atoms per cm 2 .
13. The method of claim 1 , wherein said second well region is doped with a p-type dopant at a dopant concentration of from about 5×10 11 to about 5×10 13 atoms per cm 2 .
14. The method of claim 13 , wherein said second well region is doped with a dopant at a dopant concentration of about 1×10 12 to about 5×10 12 atoms per cm 2 .
15. The method of claim 1 , wherein pixel sensor cells are spaced from each other by less than 0.4 microns.
16. The method of claim 15 , wherein pixel sensor cells are spaced from each other by less than 0.2 microns.