Process for high density split-gate memory cell for flash or EPROM
First Claim
1. A high density split-gate memory cell, for an erasable programmable read-only memory (EPROM) or flash-memory, comprising:
- a silicon island formed from a silicon substrateimplanted with a first conductivity-imparting dopant;
a first dielectric layer surrounding vertical surfaces of said silicon islands, whereby said first dielectric layer is a gate oxide;
a first conductive layer formed over a portion of the vertical surfaces of said first dielectric layer, acting as a floating gate for said high density split-gate memory cell;
a source region in said silicon substrate, implanted with a second and opposite conductivity-imparting dopant to said first conductivity-imparting dopant, surrounding the base of said silicon island;
a drain region in the top of said silicon island, implanted with a second and opposite conductivity-imparting dopant to said first conductivity-imparting dopant;
a channel region between said source and drain regions, under the vertical surfaces of said silicon island, whereby said floating gate is coupled to only a first lower portion of said channel region;
a second dielectric layer over the top and side surfaces of said floating gate, acting as an interpoly dielectric; and
a second conductive layer formed over that remaining portion of said vertical surfaces of said first dielectric layer not covered by said first conductive layer, and surrounding said second dielectric layer, coupled to that portion of said channel region not coupled to said floating gate, whereby said second conductive layer is a control gate.
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Abstract
A method and structure for manufacturing a high-density split gate memory cell, for a flash memory or EPROM, is described. Silicon islands are formed from a silicon substrate implanted with a first conductivity-imparting dopant. A first dielectric layer surrounds the vertical surfaces of the silicon islands, whereby the first dielectric layer is a gate oxide. A first conductive layer is formed over a portion of the vertical surfaces of the first dielectric layer, and acts as a floating gate for the high density split-gate memory cell. A source region is located in the silicon substrate, and is implanted with a second and opposite conductivity-imparting dopant to the first conductivity-imparting dopant, and surrounds the base of the silicon islands. A drain region is located in the top of the silicon islands, and is also implanted with a second and opposite conductivity-imparting dopant to the first conductivity-imparting dopant. A second dielectric layer is formed over the top and side surfaces of the floating gate, and acts as an interpoly dielectric. A second conductive layer is formed over that remaining portion of the vertical surfaces of the first dielectric layer not covered by the first conductive layer, and surrounds the second dielectric layer, whereby the second conductive layer is a control gate.
206 Citations
21 Claims
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1. A high density split-gate memory cell, for an erasable programmable read-only memory (EPROM) or flash-memory, comprising:
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a silicon island formed from a silicon substrate implanted with a first conductivity-imparting dopant; a first dielectric layer surrounding vertical surfaces of said silicon islands, whereby said first dielectric layer is a gate oxide; a first conductive layer formed over a portion of the vertical surfaces of said first dielectric layer, acting as a floating gate for said high density split-gate memory cell; a source region in said silicon substrate, implanted with a second and opposite conductivity-imparting dopant to said first conductivity-imparting dopant, surrounding the base of said silicon island; a drain region in the top of said silicon island, implanted with a second and opposite conductivity-imparting dopant to said first conductivity-imparting dopant; a channel region between said source and drain regions, under the vertical surfaces of said silicon island, whereby said floating gate is coupled to only a first lower portion of said channel region; a second dielectric layer over the top and side surfaces of said floating gate, acting as an interpoly dielectric; and a second conductive layer formed over that remaining portion of said vertical surfaces of said first dielectric layer not covered by said first conductive layer, and surrounding said second dielectric layer, coupled to that portion of said channel region not coupled to said floating gate, whereby said second conductive layer is a control gate. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of forming a high density split-gate memory cell, for an electrically programmable read-only memory (EPROM) or flash-memory, comprising the steps of:
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forming silicon islands from a silicon substrate implanted with a first conductivity-imparting dopant; forming source regions in said silicon substrate in the regions between said silicon islands, by implanting with a second and opposite conductivity-imparting dopant to said first conductivity-imparting dopant, and simultaneously forming drain regions in the top of said silicon islands by said implanting with a second and opposite conductivity-imparting dopant; forming a first dielectric layer surrounding vertical surfaces of said silicon islands; forming a first conductive layer over a portion of the vertical surfaces of said first dielectric layer, thereby creating a floating gate for said high density split-gate memory cell; forming a second dielectric layer over the top and side surfaces of said floating gate; and forming a second conductive layer over that remaining portion of said vertical surfaces of said first dielectric layer not covered by said first conductive layer, and surrounding said second dielectric layer, whereby said second conductive layer is a control gate. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. An electrically programmable read-only memory (EPROM) or flash-memory, with an array of high density split-gate memory cells, comprising:
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silicon islands formed from a silicon substrate having been implanted with a first conductivity-imparting dopant; a first dielectric layer surrounding vertical surfaces of said silicon islands, whereby said first dielectric layer is a gate oxide; a first conductive layer formed over a portion of the vertical surfaces of said first dielectric layer, acting as floating gates for said high density split-gate memory cells; source regions in said silicon substrate, implanted with a second and opposite conductivity-imparting dopant to said first conductivity-imparting dopant, surrounding the base of said silicon islands; drain regions in the top of said silicon islands, implanted with a second and opposite conductivity-imparting dopant to said first conductivity-imparting dopant; channel regions between said source and drain regions, under the vertical surfaces of said silicon islands, whereby said floating gate is coupled to only a first lower portion of said channel region; a second dielectric layer over the top and side surfaces of said floating gates, acting as an interpoly dielectric; and a second conductive layer formed over that remaining portion of said vertical surfaces of said first dielectric layer not covered by said first conductive layer, and surrounding said second dielectric layer, coupled to that portion of said channel region not coupled to said floating gate, whereby said second conductive layer acts as a control gate and word line for said high density split-gate memory cells, and connects together a column of said memory cells; a thermal oxide layer over said second conductive layer; an insulating layer of borophosphosilicate glass over said memory cells and and said word lines; - View Dependent Claims (16, 17, 18, 19, 20)
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21. A high density split-gate memory cell, for an erasable programmable read-only memory (EPROM) or flash-memory, formed by the method comprising the steps of:
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forming silicon islands from a silicon substrate implanted with a first conductivity-imparting dopant; forming source regions in said silicon substrate in the regions between said silicon islands, by implanting with a second and opposite conductivity-imparting dopant to said first conductivity-imparting dopant, and simultaneously forming drain regions in the top of said silicon islands by said implanting with a second and opposite conductivity-imparting dopant; forming a first dielectric layer surrounding vertical surfaces of said silicon islands; forming a first conductive layer over a portion of the vertical surfaces of said first dielectric layer, thereby creating a floating gate for said high density split-gate memory cell; forming a second dielectric layer over the top and side surfaces of said floating gate; and forming a second conductive layer over that remaining portion of said vertical surfaces of said first dielectric layer not covered by said first conductive layer, and surrounding said second dielectric layer, whereby said second conductive layer is a control gate.
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Specification