Method to fabricate self-aligned source and drain in split gate flash
First Claim
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1. A new structure for source/drain bit lines in arrays of MOSFET devices comprising:
- rows of conducting regions formed by ion implantation through openings adjacent to gate structures and in isolation regions separating columns of active areas of said arrays;
said openings filled with insulating material.
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Abstract
A new structure is disclosed for source/drain bit lines in arrays of MOSFET devices. Rows of conducting regions are formed by ion implantation through openings adjacent to gate structures and in isolation regions separating columns of active areas of the arrays. The openings are filled with insulating material.
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Citations
29 Claims
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1. A new structure for source/drain bit lines in arrays of MOSFET devices comprising:
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rows of conducting regions formed by ion implantation through openings adjacent to gate structures and in isolation regions separating columns of active areas of said arrays;
said openings filled with insulating material. - View Dependent Claims (2, 3, 4, 5)
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6. A method of fabricating a new structure for source/drain bit lines in arrays of MOSFET devices comprising:
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providing a partially processed array of MOSFET devices having active areas arranged in columns which are surrounded by insulator filled isolation regions and having formed, but not patterned, all layers comprising gate structures that are adjacent to source/drain regions, etching, in rows, all layers comprising gate structures that are adjacent to source/drain regions and insulator filled isolation regions to form openings that are aligned in rows passing source/drain positions;
performing ion implantation into the silicon under said openings creating continuous conductive regions forming rows through the silicon substrate under said openings. filling said openings with insulating material. - View Dependent Claims (7, 8, 9, 10)
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11. A method to fabricate self-aligned source/chain lines in split gate flash memory arrays, comprising:
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providing an extensive p-type semiconductor region on a semiconductor substrate;
defining columns of active regions by surrounding said active regions with oxide filled isolation regions;
performing a first threshold voltage adjust implant;
forming a floating gate oxide layer over the surface of said active regions;
forming a poly 1 layer;
forming a photoresist layer and patterning said photoresist layer to etch said poly 1 layer so that after etching said poly 1 is disposed over said active regions;
performing a poly 1 etch;
removing the photoresist layer;
forming sequentially, a first insulating layer, a poly 2 layer, a second insulating layer, a poly 3 layer and a first oxide layer;
forming another photoresist layer and patterning the photoresist to form, upon etching, two kinds of interposed openings in the row direction, i.e., perpendicular to the active region columns;
openings for source/drain lines that could be narrower than openings for erase gates;
etching sequentially, said first oxide layer, said poly 3 layer, said second insulating layer, said poly 2 layer and said first insulating layer;
removing said other photoresist layer;
forming a third photoresist layer and patterning the photoresist so as to deepen, upon etching, only the openings for source/drain lines;
etching poly 1;
etching floating gate oxide and oxide of said isolation regions;
performing a source/drain ion implantation;
removing the third photoresist layer;
forming a second oxide layer and etching said second oxide layer so that the source/drain openings are filled with said second oxide and so that sidewall spacers, composed of said second oxide, remain, etching exposed poly 1 and poly 3;
performing a second threshold adjust implant for the erase gates;
etching exposed floating gate oxide;
forming an erasing gate oxide layer;
forming a poly 4 layer;
forming a fourth photoresist layer and patterning the photoresist for erase gate lines, in the column direction, disposed over the active regions;
etching poly 4;
removing the fourth photoresist layer. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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Specification