Method for Programming a Multi-Level Non-Volatile Memory Device

• US 20080089123A1
• Filed: 08/30/2007
• Published: 04/17/2008
• Est. Priority Date: 09/06/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Byeon, Dae-Seok, Chae, Dong-Hyuk
• Granted Patent: US 7,596,022 B2
• Time in Patent Office: Days
• US Class Current: 365/185.03
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 2211/5646 Multilevel memory with flag bits, e.g. for showing that a "first page" of a word line is programmed but not a "second page"

Abstract

A method for programming multi-level non-volatile memory. A plurality of multi-bit storage cells capable of storing different levels of charge usable to represent data represented by a least significant bits (LSBs) and a most significant bits (MSBs) are programmed first with LSBs and then with MSBs. The programmed storage cells have a threshold voltage lower than a voltage VR1 to store a first value, greater than VR1 and lower than a voltage VR2 to store a second value, and greater than VR2 and lower than a voltage VR3 to store a third value. Each of the cells has a threshold voltage greater than a voltage VR3 when it is desired that the storage cell store a fourth value. VR1 is less than VR2 which is less than VR3. The flag cell is programmed to have a threshold voltage greater than VR3 to indicate that the MSBs have been programmed.

Claims

1. A method for programming multi-level non-volatile memory comprising at least one flag cell and a plurality of multi-bit storage cells, each of the plurality of multi-bit storage cells capable of storing different levels of charge usable to represent data, the data represented by a least significant bits (LSBs) and a most significant bits (MSBs), the method comprising:

programming the storage cells first with LSBs and then with MSBs such that each of the programmed storage cells;

has a threshold voltage lower than a voltage VR1 when it is desired that the storage cell store a first value;

has a threshold voltage greater than the voltage VR1 and lower than a voltage VR2 when it is desired that the storage cell store a second value;

has a threshold voltage greater than the voltage VR2 and lower than a voltage VR3 when it is desired that the storage cell store a third value; and

has a threshold voltage greater than a voltage VR3 when it is desired that the storage cell store a fourth value;

wherein VR1<

VR2<

VR3; and

programming the flag cell to have a threshold voltage greater than the voltage VR3 to indicate that the MSBs have been programmed.

2. The method of claim 1, wherein the multi-level non-volatile memory is flash memory.

3. The method of claim 2, wherein the multi-level non-volatile memory is NAND memory.

4. The method of claim 1, wherein the programming of the LSBs and the programming of the MSBs each comprise implementing an incremental step pulse program.

5. The method of claim 1, further comprising selecting one or more reference voltages for reading the data depending upon the status of the flag cell.

6. The method of claim 1, further comprising reading the flag cell at a reference voltage of VR2.

7. The method of claim 1, wherein:

VR1 is approximately equal to 0 volts;

VR2 is within the range of approximately 1 to 2 volts; and

VR3 is within the range of approximately 2.5 to 3.5 volts.

8. A controller for controlling memory according to a method for programming multi-level non-volatile memory comprising at least one flag cell and a plurality of multi-bit storage cells, each of the plurality of multi-bit storage cells capable of storing different levels of charge usable to represent data, the data represented by least significant bits (LSBs) and a most significant bits (MSBs), the method comprising:

programming the storage cells first with LSBs and then with MSB data such that each of the programmed storage cells;

has a threshold voltage lower than a voltage VR1 when it is desired that the storage cell store a first value;

has a threshold voltage greater than the voltage VR1 and lower than a voltage VR2 when it is desired that the storage cell store a second value;

has a threshold voltage greater than the voltage VR2 and lower than a voltage VR3 when it is desired that the storage cell store a third value; and

has a threshold voltage greater than a voltage VR3 when it is desired that the storage cell store a fourth value;

wherein VR1<

VR2<

VR3; and

programming the flag cell to have a threshold voltage greater than the voltage VR3 to indicate that the MSB data have been programmed.

9. The controller of claim 8, wherein the multi-level non-volatile memory is flash memory.

10. The controller of claim 9, wherein the multi-level non-volatile memory is NAND memory.

11. The controller of claim 8, wherein the programming of the LSB data and the programming of the MSBs data each comprise implementing an incremental step pulse program.

12. The controller of claim 8, further comprising selecting one or more reference voltages for reading the data depending upon the status of the flag cell.

13. The controller of claim 8, further comprising reading the flag cell at a reference voltage of VR2.

14. The controller of claim 8, wherein:

VR1 is approximately equal to 0 volts;

VR2 is within the range of approximately 1 to 2 volts; and

VR3 is within the range of approximately 2.5 to 3.5 volts.

15. A method for programming a multi-level non-volatile memory comprising at least one flag cell and a plurality of multi-bit storage cells, each of the plurality of multi-bit storage cells capable of storing different levels of charge usable to represent data, the data represented by a plurality of data pages, the method comprising:

sequentially programming one or more of the plurality of data pages such that each of the programmed storage cells has a threshold voltage within one of a plurality of threshold voltage ranges comprising a first range and a plurality of subsequent ranges, wherein each of the plurality of subsequent ranges is defined as being equal to or greater than a respective verify voltage, wherein each of the plurality of subsequent ranges is read at a respective read voltage and wherein for each given subsequent range the respective read voltage is less than the respective verify voltage by a margin M; and

programming the at least one flag cell to a threshold voltage within a threshold voltage range indicative of the number of data pages that have been programmed, wherein the flag cell threshold voltage range is defined as being equal to or greater than a flag cell verify voltage, wherein the flag cell is read at a flag cell read voltage, and the flag cell read voltage is less than the flag cell verify voltage by an enhanced margin M_enhanced that is larger than the margin M.

16. The method of claim 15 wherein the at least one flag cell is a single flag cell and wherein the single flag cell is programmed to one of a plurality of threshold voltage ranges to indicate the number of data pages that have been programmed.

17. The method of claim 15 wherein the at least one flag cell is a plurality of flag cells and wherein which of the plurality of flag cells are programmed indicates the number of data pages that have been programmed.

18. The method of claim 15, wherein the multi-level non-volatile memory is flash memory.

19. The method of claim 15, wherein the multi-level non -volatile memory is NAND memory.

20. The method of claim 15, wherein the programming of the plurality of data pages each comprise implementing an incremental step pulse program.

21. The method of claim 15, further comprising selecting one or more reference voltages for reading the data depending upon the status of the one or more flag cells.

22. A controller for controlling memory according to a method for programming multi-level non-volatile memory comprising at least one flag and a plurality of multi-bit storage cells, each of the plurality of multi-bit storage cells capable of storing different levels of charge usable to represent data, the data represented by a plurality of data pages, the method comprising:

sequentially programming one or more of the plurality of data pages such that each of the programmed storage cells has a threshold voltage within one of a plurality of threshold voltage ranges comprising a first range and a plurality of subsequent ranges, wherein each of the plurality of subsequent ranges is defined as being equal to or greater than a respective verify voltage, wherein each of the plurality of subsequent ranges is read at a respective read voltage, and wherein for each given subsequent range, the respective read voltage is less than the respective verify voltage by a margin M; and

programming the at least one flag cell to a threshold voltage within a threshold voltage range indicative of the number of data pages that have been programmed, wherein the flag cell threshold voltage range is defined as being equal to or greater than a flag cell verify voltage, wherein the flag cell is read at a flag cell read voltage, and the flag cell read voltage is less than the flag cell verify voltage by an enhanced margin M_enhanced that is larger than the margin M.

23. The controller of claim 22 wherein the at least one flag cell is a single flag cell and wherein the single flag cell is programmed to one of a plurality of threshold voltage ranges to indicate the number of data pages that have been programmed.

24. The controller of claim 22 wherein the at least one flag cell is a plurality of flag cells and wherein which of the plurality of flag cells are programmed indicates the number of data pages that have been programmed.

25. The controller of claim 22, wherein the multi-level non-volatile memory is flash memory.

26. The controller of claim 22, wherein the multi-level non-volatile memory is NAND memory.

27. The controller of claim 22, wherein the programming of the plurality of data pages each comprise implementing an incremental step pulse program.

28. The controller of claim 22, wherein the method further comprises selecting one of more reference voltages for reading the data depending upon the status of the one or more flag cells.