Method for angular doping of source and drain regions for odd and even NAND blocks
View Patent ↗Source implantations are performed at a first implantation angle to areas between stacked gate structures of a NAND string. Drain implantations are performed at a second implantation angle to areas between the stacked gate structures. The drain implantations create lower doped regions of a first conductivity type in the substrate on drain sides of the stacked gate structures. The source implantations create higher doped regions of the first conductivity type in the substrate on source sides of the stacked gate structures.
1. A method for creating NAND flash memory, comprising:
creating gate structures of one or more NAND strings, said NAND strings include at least a first NAND string and a second NAND string, said first NAND string and said second NAND string are connected to a common control line;
masking source/drain regions of said second NAND string;
performing source implantation at a first angular orientation to create source regions for said first NAND string; and
performing drain implantation at a second angular orientation, different from said first angular orientation, to create drain regions for said first NAND string;
masking source/drain regions of said first NAND string;
performing source implantation at said second angular orientation to create source regions for said second NAND string; and
performing drain implantation at said first angular orientation to create drain regions for said second NAND string.
2. The method of claim 1 , wherein:
said first angular orientation includes one or more small angles in a first direction; and
said second angular orientation includes one or more small angles in an opposite direction from said first direction.
3. The method of claim 1 , wherein:
said first angular orientation includes a doping angle perpendicular to a substrate for said first NAND string.
4. The method of claim 1 , wherein:
said second angular orientation includes doping at an angle perpendicular to a substrate for said first NAND string.
5. The method of claim 1 , wherein:
said source implantation and said drain implantation include doping a source line area and a bit line contact area; and
said method further comprises performing additional doping of said source line area and said bit line area using an implantation angle larger than with respect to said first angular orientation and said second angular orientation so that said additional doping of said source line area and said bit line area does not include doping of source/drain regions of said NAND string.
6. The method of claim 1 , wherein:
said source implantation to create source regions for said first NAND string and said drain implantation to create drain regions for said first NAND string include doping a source line area while masking a bit line contact area for said first NAND string; and
said method further comprises performing additional doping of said bit line area.
7. The method of claim 1 , wherein:
said source implantation to create source regions for said first NAND string and said drain implantation to create drain regions for said first NAND string include doping a bit line area while masking a source line area for said first NAND string; and
said method further comprises performing additional doping of said source line area.
8. The method of claim 1 , wherein:
said source implantation to create source regions for said first NAND string and said drain implantation to create drain regions for said first NAND string do not include doping a bit line area and do not include doping a source line area for said first NAND string; and
said method further comprises performing additional doping of said source line area and bit line contact area for said first NAND string.
9. The method of claim 1 , wherein:
said stacked gate structures are formed on a substrate;
said substrate includes channel areas between source areas and drain areas for said first NAND string and said second NAND string;
said source implantation for said first NAND string and said source implantation for said second NAND string include doping said source areas;
said drain implantation for said first NAND string and said drain implantation for said second NAND string include doping said drain areas; and
said channel areas include B-Halos.
10. The method of claim 1 , further comprising:
adding higher doped B-Halos for channel areas between source areas and drain areas for said first NAND string and said second NAND string; and
adding lower doped B-Halos for said channel areas, said higher doped B-Halos are added at source sides of said channels and said lower doped B-Halos are added at drain sides of said channels.
11. The method of claim 1 , wherein:
said common control line is a bit line.
12. The method of claim 1 , wherein:
said drain implantation for said first NAND string and said drain implantation for said second NAND string include creating lower doped regions of a first conductivity type; and
said source implantation for said first NAND string and said source implantation for said second NAND string include creating higher doped regions of said first conductivity type.