Isolation process and structure for CMOS imagers

Abstract

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 pixel structure comprising:
 a substrate;   an isolation region of a first conductivity type located below a surface of said substrate, said implanted region comprising at least two implanted isolation regions having different widths; and   at least one photosensor having a charge collection region of a second conductivity type formed adjacent said implanted isolation region.   
   
   
       2 . The pixel structure of  claim 1 , wherein said photosensor is a photodiode. 
   
   
       3 . The pixel structure of  claim 1 , wherein said photosensor is a photoconductor. 
   
   
       4 . The pixel structure of  claim 1 , wherein said photosensor is a photogate. 
   
   
       5 . The pixel structure of  claim 1 , wherein said pixel comprises two photosensors, each disposed on opposite sides of said implanted region and adjacent said implanted region. 
   
   
       6 . The pixel structure of  claim 1 , wherein said substrate further comprises a doped epitaxial layer over a substrate layer, and wherein said implanted region is provided within said doped epitaxial layer. 
   
   
       7 . The pixel structure of  claim 6 , wherein said implanted region comprises a first implanted isolation region located below an upper surface of said doped epitaxial layer, said first implanted isolation region having a first width, and a second implanted isolation region located below and in contact with said first implanted isolation region, said second implanted isolation region having a second width greater than the first width. 
   
   
       8 . The pixel structure of  claim 7 , wherein said first width is less than about 0.4 microns. 
   
   
       9 . The pixel structure of  claim 8 , wherein said first width is less than about 0.2 microns. 
   
   
       10 . The pixel structure of  claim 7 , wherein said second width is about 0.6 to about 1.2 microns. 
   
   
       11 . The pixel structure of  claim 10 , wherein said second width is about 0.8 microns. 
   
   
       12 . The pixel structure of  claim 7 , wherein said first implanted isolation region has a thickness of about 0.5 to about 2.0 microns. 
   
   
       13 . The pixel structure of  claim 12 , wherein said first implanted isolation region has a thickness of about 1 micron. 
   
   
       14 . The pixel structure of  claim 7 , wherein said second implanted isolation region has a thickness of about 1.5 to about 12.0 microns. 
   
   
       15 . The pixel structure of  claim 14 , wherein said second implanted isolation region has a thickness of about 5 microns. 
   
   
       16 . The pixel structure of  claim 7 , wherein said second implanted isolation region has a trapezoidal cross-section. 
   
   
       17 . The pixel structure of  claim 7 , wherein said first implanted isolation 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 . 
   
   
       18 . The pixel structure of  claim 17 , wherein said first implanted isolation 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 . 
   
   
       19 . The pixel structure of  claim 7 , wherein said second implanted isolation 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 . 
   
   
       20 . The pixel structure of  claim 19 , wherein said second implanted isolation 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 . 
   
   
       21 . The pixel structure of  claim 1 , wherein said implanted isolation region is located within a p-type epitaxial layer formed over a P+ substrate. 
   
   
       22 . The pixel structure of  claim 21 , wherein said p-type epitaxial layer is formed to a thickness of about 2 to about 12 microns. 
   
   
       23 . The pixel structure of  claim 22 , wherein said p-type epitaxial layer is formed to a thickness of about 2 to about 7 microns. 
   
   
       24 . The pixel structure of  claim 1 , wherein said first conductivity type is p-type and said second conductivity type is n-type. 
   
   
       25 . The pixel structure of  claim 1 , wherein said first conductivity type is n-type and said second conductivity type is p-type. 
   
   
       26 . The pixel structure of  claim 1 , wherein said photosensor is a p-n-p photodiode. 
   
   
       27 . A pixel structure comprising:
 a substrate;   an implanted region of a first conductivity type located below a surface of said substrate; and   a first and second photosensors formed adjacent said implanted region and on opposite sides of said implanted region, said first photosensor being spaced from said second photosensor by less than about 0.4 microns.   
   
   
       28 . The pixel structure of  claim 27 , wherein said first photosensor is spaced from said second photosensor by less than about 0.2 microns. 
   
   
       29 . The pixel structure of  claim 27 , wherein said implanted region comprises at least two implanted isolation regions having different widths, said at least two implanted isolation regions being located one below the other and in contact with each other. 
   
   
       30 . The pixel structure of  claim 29 , wherein said implanted isolation regions are formed within a doped epitaxial layer provided over a doped substrate layer. 
   
   
       31 . The pixel structure of  claim 30 , wherein one of said implanted isolation regions contacts an upper surface of said doped epitaxial layer and the other of said implanted isolation regions contacts an upper surface of said doped substrate layer. 
   
   
       32 . An isolation structure formed in a substrate for isolating a first pixel sensor cell from an adjacent second pixel sensor cell, said isolation structure comprising:
 a first implanted region of a first conductivity type extending below an upper surface of a substrate, said first conductivity type being complementary to a second conductivity type first and second charge collection regions corresponding to said first and second pixel sensor cells, respectively, said first implanted region having a first width; and   a second implanted region located below and in contact with said first implanted region, said second implanted region having a second width greater than the first width.   
   
   
       33 . The isolation structure of  claim 32 , wherein said first and second implanted regions are formed within an epitaxial layer doped with dopants of the first conductivity type. 
   
   
       34 . The isolation structure of  claim 32 , wherein said first and second implanted regions are doped with a p-type dopant. 
   
   
       35 . The isolation structure of  claim 32 , wherein said first width is less than about 0.4 microns. 
   
   
       36 . The isolation structure of  claim 35 , wherein said first width is less than about 0.2 microns. 
   
   
       37 . The isolation structure of  claim 32 , wherein said second width is about 0.6 to 1.2 microns. 
   
   
       38 . The isolation structure of  claim 37 , wherein said second width is about 0.8 microns. 
   
   
       39 . The isolation structure of  claim 32 , wherein said first implanted region has a thickness of about 0.5 to about 2.0 microns. 
   
   
       40 . The isolation structure of  claim 32 , wherein said second implanted region has a thickness of about 1.5 to about 12.0 microns. 
   
   
       41 . The isolation structure of  claim 33 , wherein each of said first and second implanted regions 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 . 
   
   
       42 . The isolation structure of  claim 41 , wherein said doped epitaxial layer is formed to a thickness of about 2 to about 12 microns. 
   
   
       43 . The isolation structure of  claim 42 , wherein said doped epitaxial layer is formed to a thickness of about 2 to about 7 microns. 
   
   
       44 . The isolation structure of  claim 32 , wherein said first conductivity type is p-type and said second conductivity type is n-type. 
   
   
       45 . The isolation structure of  claim 32 , wherein said first conductivity type is n-type and said second conductivity type is p-type. 
   
   
       46 . The isolation structure of  claim 32 , wherein said first and second charge collection regions correspond to at least one element selected from the group consisting of a photodiode, a photogate, and a photoconductor. 
   
   
       47 . An imaging device, comprising:
 a first photosensor of a first pixel cell, said first photosensor comprising a first doped layer of a first conductivity type formed in a substrate, and a first charge collection region formed below said first doped layer for accumulating photo-generated charge, said charge collection region being of a second conductivity type;   a second photosensor of a second pixel cell, said second photosensor comprising a second doped layer of said first conductivity type formed in said substrate, and a second charge collection region formed below said second doped layer for accumulating photo-generated charge, said charge collection region being of said second conductivity type; and   a barrier implanted region of said first conductivity type located adjacent both said first and second photosensors for providing isolation of said first photosensor from said second photosensor, said barrier implanted region comprising at least two different isolation regions having different widths.   
   
   
       48 . The imaging device of  claim 47 , wherein said barrier implanted isolation region comprises a first isolation region having a first width of less than about 0.2 microns, and a second isolation region located below and in contact with said first isolation region and having a second width of about 0.8 microns. 
   
   
       49 . The imaging device of  claim 48 , wherein said first isolation region has a thickness of about 1.0 micron, and said second isolation region has a thickness of about 5 microns. 
   
   
       50 . The imaging device of  claim 48 , wherein each of said first and second isolation regions 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 . 
   
   
       51 . The imaging device of  claim 50 , wherein each of said first and second isolation regions is doped with a p-type dopant at a dopant concentration of from about 1×10 12  to about 5×10 12  atoms per cm 2 . 
   
   
       52 . The imaging device of  claim 48 , wherein each of said first and second isolation regions is formed within a doped epitaxial layer formed over a doped substrate layer. 
   
   
       53 . The imaging device of  claim 52 , wherein said first isolation region contacts an upper surface of said doped epitaxial layer and said second isolation region contacts an upper surface of said doped substrate layer. 
   
   
       54 . The imaging device of  claim 48 , wherein each of said first and second charge collection regions is adjacent a respective gate of a transfer transistor formed over said substrate, said transfer gate transferring charge accumulated in respective first and second charge collection regions to a respective first and second doped region of said second conductivity type. 
   
   
       55 . The imaging device of  claim 47 , wherein said first and second photosensors are p-n-p photodiodes. 
   
   
       56 . A CMOS image sensor comprising:
 a p-type epitaxial layer provided over a P+ substrate;   a p-type barrier implanted isolation region formed within said p-type epitaxial layer; and   a first pixel adjacent said p-type barrier implanted region and comprising a first photosensor, and a second pixel adjacent said p-type barrier implanted region and comprising a second photosensor, wherein said first photosensor is spaced from said second photosensor by less than about 0.2 microns.   
   
   
       57 . The CMOS image sensor of  claim 56 , wherein said p-type barrier implanted region comprises a first p-type well region having a first width and a second p-type well region located below and in contact with said first p-type well region, said second p-type well region having a second width which is greater than the first width. 
   
   
       58 . The CMOS image sensor of  claim 57 , wherein said first p-type well region is in contact with an upper surface of said p-type epitaxial layer, and said second p-type well region is in contact with an upper surface of said P+ substrate. 
   
   
       59 . The CMOS image sensor of  claim 57 , wherein said first p-type well region has a thickness of about 0.5 to about 2.0 microns. 
   
   
       60 . The CMOS image sensor of  claim 59 , wherein said first p-type well region has a thickness of about 1 micron. 
   
   
       61 . The CMOS image sensor of  claim 57 , wherein said second p-type well region has a thickness of about 1.5 to about 12.0 microns. 
   
   
       62 . The CMOS image sensor of  claim 61 , wherein said second p-type well region has a thickness of about 5 microns. 
   
   
       63 . The CMOS image sensor of  claim 57 , wherein said first p-type well region is doped with a dopant at a dopant concentration of from about 5×10 11  to about 5×10 13  atoms per cm 2 . 
   
   
       64 . The CMOS image sensor of  claim 63 , wherein said first p-type 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 . 
   
   
       65 . The CMOS image sensor of  claim 57 , wherein said second p-type well region is doped with a dopant at a dopant concentration of from about 5×10 11  to about 5×10 13  atoms per cm 2 . 
   
   
       66 . The CMOS image sensor of  claim 65 , wherein said second p-type 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 . 
   
   
       67 . A CMOS imager system comprising:
 (i) a processor; and   (ii) a CMOS imaging device coupled to said processor, said CMOS imaging device comprising:   an implanted region of a first conductivity type formed in a substrate, said implanted region comprising at least two implanted isolation regions having different widths; and   at least two pixels adjacent said implanted region, each of said pixels comprising a photodiode adjacent a gate of a transfer transistor, each of said photodiodes further comprising a pinned layer of said first conductivity type, and a doped region of a second conductivity type located below said pinned layer, said doped region being adjacent said implanted region.   
   
   
       68 . The system of  claim 67 , wherein each of said photodiodes is a p-n-p photodiode. 
   
   
       69 . The system of  claim 67 , wherein said at least two implanted isolation regions comprise a first implanted isolation region having a width less than about 0.2 microns and a second implanted isolation located below and in contact with said first implanted region. 
   
   
       70 . The system of  claim 67 , wherein said at least two pixels are spaced from one another by less than about 0.2 microns. 
   
   
       71 - 86 . (canceled) 
   
   
       87 . A method of forming minimally spaced pixel cells of an imaging device, said method comprising:
 forming an implanted region below a surface of a p-type epitaxial layer by implanting p-type ions within said p-type epitaxial layer, said implanting region being formed of a first p-type well region having a first width and a second p-type well region having a second width greater than the first width; and   providing at least two n-type doped regions of photosensitive elements of at least two pixel cells below said surface of said p-type epitaxial layer and adjacent said implanted region.   
   
   
       88 . The method of  claim 87 , wherein said p-type epitaxial layer is formed over a P+ substrate layer. 
   
   
       89 . The method of  claim 88 , wherein said first p-type well region is formed below said surface of said p-type epitaxial layer, and wherein said second p-type well region is formed below and in contact with said first p-type well region and in contact with an upper surface of said P+ substrate layer. 
   
   
       90 . The method of  claim 87 , wherein said first p-type well region is formed to a width of less than about 0.4 microns. 
   
   
       91 . The method of  claim 90 , wherein said first p-type well region is formed to a width of less than about 0.2 microns. 
   
   
       92 . The method of  claim 87 , wherein said second p-type well region is formed to a width of about 0.6 to about 1.2 microns. 
   
   
       93 . The method of  claim 92 , wherein said p-type second well region is formed to a width of about 0.8 microns. 
   
   
       94 . The method of  claim 87 , wherein said first p-type well region is formed to a thickness of about 0.5 to about 2 microns. 
   
   
       95 . The method of  claim 87 , wherein said second p-type well region is formed to a thickness of about 1.5 to about 12.0 microns. 
   
   
       96 . The method of  claim 87 , wherein said first p-type 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 . 
   
   
       97 . The method of  claim 87 , wherein said second p-type 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 . 
   
   
       98 . A method of forming an isolation structure for isolating pixel sensor cells, said method comprising:
 providing an epitaxial layer over a doped substrate, said epitaxial layer being doped with dopants of a first conductivity type;   conducting a plurality of implants with dopants of said first conductivity type in said epitaxial layer to form an implanted isolation region having a at least a first doped isolation region and a second doped isolation region located below and in contact with said first doped isolation region, said second doped isolation region having a second width greater than a first width of said first doped isolation region; and   forming doped regions of photosensors of a second conductivity type in said epitaxial layer, said photosensors being adjacent said implanted region.   
   
   
       99 . The method of  claim 98 , wherein a lower portion of said second doped isolation region contacts an upper surface of said doped substrate. 
   
   
       100 . The method of  claim 98 , wherein said first doped isolation region is formed to a width of less than about 0.4 microns. 
   
   
       101 . The method of  claim 98 , wherein said first doped isolation region is formed to a width of less than about 0.2 microns. 
   
   
       102 . The method of  claim 98 , wherein at least one of said photosensors is a photodiode. 
   
   
       103 . The method of  claim 98 , wherein at least one of said photosensors is a photogate. 
   
   
       104 . The method of  claim 98 , wherein at least one of said photosensors is a photoconductor.