Manufacturing process to eliminate ONO fence material in high density NAND-type flash memory devices
First Claim
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1. A method for fabricating a semiconductor device comprising:
- providing a first layer of polysilicon on the surface of a semiconductor substrate;
protecting selected portions of said first layer of polysilicon and exposing portions of said first layer of polysilicon by providing a masking material over said selected portions;
removing said exposed portions of said first layer of polysilicon;
providing a second layer of polysilicon over said surface of said semiconductor substrate;
anisotropically removing said second layer of polysilicon, so as to form spacers of said second layer of polysilicon adjacent said protected selected portions of said first layer of polysilicon;
removing said masking material;
providing a triple layer of oxide-nitride-oxide (ONO) over said first layer of polysilicon and said spacer;
forming a third layer of polysilicon over said triple layer of oxide-nitride-oxide;
removing portions of said third layer of polysilicon, said triple layer, said first layer of polysilicon and said spacer between intended locations of memory core cells successively; and
removing ONO material remaining between intended locations of memory core cells.
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Abstract
Polystringers that cause NAND-type memory core cells to malfunction are covered by ONO fence material. ONO fence is removed so that polystringers may then be removed more readily. A SiON layer, tungsten silicide layer, second polysilicon layer, ONO dielectric, and first polysilicon layer are successively removed from between NAND-type flash memory core cells leaving ONO fence that shields some first polysilicon layer material from removal. The device is next exposed to an hydrogen-fluoride solution to remove oxide-based materials, particularly ONO fence. Thereafter, the polystringers are exposed and may thus be removed more readily.
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Citations
24 Claims
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1. A method for fabricating a semiconductor device comprising:
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providing a first layer of polysilicon on the surface of a semiconductor substrate;
protecting selected portions of said first layer of polysilicon and exposing portions of said first layer of polysilicon by providing a masking material over said selected portions;
removing said exposed portions of said first layer of polysilicon;
providing a second layer of polysilicon over said surface of said semiconductor substrate;
anisotropically removing said second layer of polysilicon, so as to form spacers of said second layer of polysilicon adjacent said protected selected portions of said first layer of polysilicon;
removing said masking material;
providing a triple layer of oxide-nitride-oxide (ONO) over said first layer of polysilicon and said spacer;
forming a third layer of polysilicon over said triple layer of oxide-nitride-oxide;
removing portions of said third layer of polysilicon, said triple layer, said first layer of polysilicon and said spacer between intended locations of memory core cells successively; and
removing ONO material remaining between intended locations of memory core cells. - View Dependent Claims (2, 3, 4)
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5. A method for fabricating a semiconductor device comprising:
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providing a first insulating layer over a semiconductor substrate;
forming a first conductive layer over said first insulating layer;
forming a mask over said first conductive layer thereby protecting selected portions of said first conductive layer and exposing remaining portions of said first conductive layer;
removing exposed remaining portions of said first conductive layer;
providing a second conductive layer over said semiconductor substrate, including said protected selected portions of said first conductive layer; and
anisotropically removing said second conductive layer so as to form spacers of said second conductive layer adjacent said selected protected portions of said first conductive layer. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
forming a mask layer over said first conductive layer;
depositing and patterning a photoresist layer over said mask layer to expose a portion of said mask layer; and
removing said exposed portion of said mask layer to form said mask.
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9. The method of claim 8, further comprising removing said photoresist layer.
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10. The method of claim 5, wherein said mask comprises oxide.
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11. The method of claim 5, further comprising forming said mask over an active region of said substrate.
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12. The method of claim 5, wherein said portion of said first conductive layer comprises a portion above a core region of a field oxide region in said substrate.
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13. The method of claim 5, wherein said second conductive layer comprises amorphous silicon.
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14. The method of claim 5, further comprising:
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removing said mask; and
forming a dielectric layer over said first insulating layer, said spacer and said protected selected portion of said first conductive layer.
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15. The method of claim 14, wherein said dielectric layer comprises ONO (oxide-nitride-oxide).
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16. The method of claim 14, further comprising:
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forming a second conductive layer over said dielectric layer; and
selectively removing portions of said second conductive layer, said dielectric layer, said first conductive layer and said spacer, thereby forming said semiconductor device.
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17. The method of claim 16, further comprising removing, after said selectively removing, portions of said dielectric layer not covered by said second conductive layer.
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18. The method of claim 17, wherein said removing portions of said dielectric layer comprises exposing said semiconductor device to a hydrogen fluoride solution.
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19. The method of claim 17, wherein said removing portions of said dielectric layer comprises performing a buffer oxide etch.
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20. The method of claim 15, further comprising cleaning said semiconductor device.
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21. The method of claim 20, further comprising removing any polystringers.
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22. The method of claim 21, wherein said removing any polystringers comprises oxidizing said polystringers.
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23. The method of claim 22, further comprising heating said semiconductor device to oxidize said polystringers.
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24. The method of claim 14, further comprising:
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forming a tungsten silicide layer over said second conductive layer; and
forming a silicon oxy-nitride (SiON) layer over said tungsten silicide layer.
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Specification