Non-volatile memory structure and method of fabrication
A method for creating a non-volatile memory array includes implanting pocket implants in a substrate at least between mask columns of a given width and at least through an ONO layer covering the substrate, generating increased-width polysilicon columns from the mask columns, generating bit lines in the substrate at least between the increased-width polysilicon columns and depositing oxide at least between the polysilicon columns.
1. A method for creating a non-volatile memory array, the method comprising:
implanting pocket implants in a substrate at least between mask columns of a given width and at least through an ONO layer covering said substrate;
generating increased-width polysilicon columns from said mask columns;
generating bit lines in said substrate at least between said increased-width polysilicon columns;
depositing oxide at least between said polysilicon columns,
wherein said generating polysilicon columns comprises: generating spacers to the sides of said mask columns;
etching at least said first polysilicon layer between said spacers to generate said increased-width polysilicon columns, and
wherein said generating polysilicon columns also comprises removing said mask columns and said spacers after said etching.
2. The method according to claim 1 and wherein said spacers are one of the following materials: nitride and oxide.
3. The method according to claim 1 and wherein said generating bit lines comprises implanting said bit lines and performing a rapid thermal anneal.
4. The method according to claim 1 and wherein said etching etches to one of the following layers: a top layer of said ONO layer, a bottom layer of said ONO layer and said substrate.
5. The method according to claim 1 wherein said etching etches to either one of the following: a bottom layer of said ONO layer and said substrate and also comprising depositing a protective spacer between said polysilicon columns.
6. The method according to claim 1 and wherein said depositing oxide occurs before removing said mask columns and said spacers.
7. The method according to claim 1 and wherein said depositing oxide occurs after removing said mask columns and said spacers.
8. The method according to claim 1 and also comprising planarizing said array to the height of said increased-width polysilicon columns and removing said mask columns and said spacers before said planarizing.
9. The method according to claim 1 and also comprising planarizing said array to the height of said mask columns and removing said mask columns and said spacers after said planarizing.
10. The method according to claim 1 wherein said generating polysilicon columns comprises etching polysilicon between said mask columns and generating polysilicon spacers to the sides of said polysilicon columns.
11. The method according to claim 10 and also comprising:
depositing second polysilicon on top of said planarized array;
etching said second polysilicon into word lines;
removing a portion of said deposited oxide between said increased-width polysilicon columns and said word lines; and
etching said increased-width polysilicon columns between said word lines into gates.
12. The method according to claim 10 and wherein the thickness of said polysilicon columns is at least 20 nm thick.
13. The method according to claim 11 and wherein the thickness of said second polysilicon is at least 20 nm thick.
14. The method according to claim 1 and wherein said non-volatile memory array is a nitride read only memory (NROM) array.