DRAM including a vertical surround gate transistor
First Claim
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1. A method of forming a vertical memory cell, the method comprising:
- forming a vertical memory cell comprising;
a source,a drain,a polysilicon surround gate to extend in a first generally vertically extending direction, anda generally vertically extending channel region, wherein the source is arranged at an upper end of the vertically extending channel region and wherein the drain is arranged at an opposite lower end of the vertically extending channel region;
depositing a dielectric to cover a horizontal upper surface of the polysilicon surround gate;
forming a trench extending along the surround gate so as to expose a vertical surface of the surround gate;
depositing a thin metal on the exposed vertical surface of at least the polysilicon surround gate while the horizontal upper surface of the polysilicon surround gate remains covered by the dielectric;
exposing the thin metal to heat that is sufficiently high to react at least a portion of the thin metal with at least a portion of the polysilicon gate in order to form a silicided gate extending along a vertical length of the formerly exposed vertical surface of the polysilicon surround gate;
forming a spacer arranged to cover at least the silicided gate contact; and
forming a second separate generally vertical conductive path extending from a drain contact upwards to above the surround gate, wherein the drain contact is arranged adjacent the lower end of the vertically extending channel region.
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Abstract
DRAM memory cells having a feature size of less than about 4F2 include vertical surround gate transistors that are configured to reduce any short channel effect on the reduced size memory cells. In addition, the memory cells may advantageously include reduced resistance word line contacts and reduced resistance bit line contacts, which may increase a speed of the memory device due to the reduced resistance of the word line and bit line contacts.
459 Citations
22 Claims
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1. A method of forming a vertical memory cell, the method comprising:
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forming a vertical memory cell comprising; a source, a drain, a polysilicon surround gate to extend in a first generally vertically extending direction, and a generally vertically extending channel region, wherein the source is arranged at an upper end of the vertically extending channel region and wherein the drain is arranged at an opposite lower end of the vertically extending channel region; depositing a dielectric to cover a horizontal upper surface of the polysilicon surround gate; forming a trench extending along the surround gate so as to expose a vertical surface of the surround gate; depositing a thin metal on the exposed vertical surface of at least the polysilicon surround gate while the horizontal upper surface of the polysilicon surround gate remains covered by the dielectric; exposing the thin metal to heat that is sufficiently high to react at least a portion of the thin metal with at least a portion of the polysilicon gate in order to form a silicided gate extending along a vertical length of the formerly exposed vertical surface of the polysilicon surround gate; forming a spacer arranged to cover at least the silicided gate contact; and forming a second separate generally vertical conductive path extending from a drain contact upwards to above the surround gate, wherein the drain contact is arranged adjacent the lower end of the vertically extending channel region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 19, 20)
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10. A vertical memory cell comprising:
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a source region; a drain region; a polysilicon surround gate extending generally vertically between the source region and drain region; a channel region extending generally vertically between the source region and the drain region wherein the source region is arranged at an upper end of the vertically extending channel region and wherein the drain region is arranged at an opposite lower end of the vertically extending channel region; a vertically extending silicided surround gate contact arranged adjacent the polysilicon surround gate wherein the polysilicon surround gate and the silicided surround gate contact extend along a vertical length of the channel region; an insulating sidewall spacer arranged to cover a vertical outer surface of the silicided gate contact; and a separate second conductive path extending generally vertically from a silicided drain contact over the drain region to above the polysilicon surround gates and the spacer and wherein the drain contact is arranged adjacent the lower end of the vertically extending channel region, the second conductive path insulated from the silicided surround gate contact by the insulating sidewall spacer.
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11. A method of forming a memory device comprising a plurality of vertical memory cells, the method comprising:
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forming a plurality of vertical memory cells each comprising a polysilicon surround gate vertically extending over a channel region, a source arranged generally at an upper end of the channel region, and a drain arranged generally at an opposite lower end of the channel region; depositing dielectric to cover upper surfaces of the polysilicon surround gates; forming trenches to expose vertical surfaces of the polysilicon surround gates; depositing a thin metal on the exposed vertical surfaces of the polysilicon surround gate of each memory cell; exposing the thin metal to heat that is sufficiently high to react at least a portion of the thin metal with at least a portion of the polysilicon gate in order to form a silicided gate contact adjacent and extending across an entire vertical length of the polysilicon surround gate in each of the memory cells; forming sidewall spacers arranged to cover at least the silicided gate contacts; and forming second separate generally vertical conductive paths extending from respective drain contacts upwards to above the respective surround gate, wherein the drain contacts are arranged adjacent the lower end of the respective vertically extending channel region and wherein the second generally vertical conductive paths are isolated from the silicided gate contacts by the sidewall spacers. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 21, 22)
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Specification