Dummy word line control scheme for non-volatile memory
A memory system includes blocks (or other groupings) of memory cells including data memory cells and dummy memory cells. In order to mitigate program disturb or other issues, the memory system applies a gate voltage based on temperature to all or a subset of the dummy memory cells as part of a memory operation.
1. A non-volatile storage apparatus, comprising:
a plurality of non-volatile memory cells including a data memory cell and a dummy memory cell, wherein the data memory cell and the dummy memory cell are part of a common NAND string;
a select gate, wherein the select gate is part of the common NAND string and the dummy memory cell is located on the common NAND string between the data memory cell and the select gate; and
one or more control circuits in communication with the plurality of non-volatile memory cells, the one or more control circuits configured to perform a memory operation on the data memory cell, the one or more control circuits configured to apply a gate voltage based on temperature to the dummy memory cell as part of the memory operation, wherein:
the memory operation is an erase operation; and
the one or more control circuits are configured to apply the gate voltage based on temperature to the dummy memory cell as part of the memory operation to cause the dummy memory cell to experience a shallow erase in response to a higher temperature and to cause the dummy memory cell to experience a deeper erase in response to a lower temperature.
2. The non-volatile storage apparatus of claim 1 , wherein:
the one or more control circuits are configured to apply a higher gate voltage to the dummy memory cell in response to a higher temperature; and
the one or more control circuits are configured to apply a lower gate voltage to the dummy memory cell in response to a lower temperature.
3. The non-volatile storage apparatus of claim 1 , wherein:
the one or more control circuits include a temperature detection circuit configured to detect temperature; and
the one or more control circuits are configured to add a temperature compensation voltage to a base gate voltage for the dummy memory cell in response to a detected higher temperature and
the one or more control circuits are configured to apply the base gate voltage to the dummy memory cell in response to a detected lower temperature.
4. The non-volatile storage apparatus of claim 1 , wherein:
the one or more control circuits are configured to detect temperature; and
the one or more control circuits are configured to add a higher temperature compensation voltage to a base gate voltage for the dummy memory cell in response to a detected higher temperature; and
the one or more control circuits are configured to add a lower temperature compensation voltage to a base gate voltage for the dummy memory cell in response to a detected lower temperature.
5. A non-volatile storage apparatus, comprising:
a plurality of non-volatile memory cells including a data memory cell and a dummy memory cell, wherein the data memory cell and the dummy memory cell are part of a common NAND string;
a select gate, wherein the select gate is part of the common NAND string and the dummy memory cell is located on the common NAND string between the data memory cell and the select gate; and
one or more control circuits in communication with the plurality of non-volatile memory cells, the one or more control circuits configured to perform a memory operation on the data memory cell, the one or more control circuits configured to apply a gate voltage based on temperature to the dummy memory cell as part of the memory operation, wherein:
the one or more control circuits configured to apply the gate voltage to the dummy memory cell as part of the memory operation based on temperature and number of word lines already programmed;
the memory operation is a programming operation for the data memory cell;
the data memory cell and the dummy memory cell are in a block;
the one or more control circuits are configured to apply a higher gate voltage to the dummy memory cell if more than a predetermined number of word lines of the block are programmed; and
the one or more control circuits are configured to apply a lower gate voltage to the dummy memory cell if less than the predetermined number of word lines of the block are programmed.
6. The non-volatile storage apparatus of claim 5 , wherein:
the one or more control circuits are configured to detect temperature;
the one or more control circuits are configured to apply a higher gate voltage to the dummy memory cell if a lower temperature is detected; and
the one or more control circuits are configured to apply a lower gate voltage to the dummy memory cell if a higher temperature is detected.
7. The non-volatile storage apparatus of claim 5 , wherein:
the one or more control circuits are configured to detect temperature;
the one or more control circuits are configured to increase gate voltage to the dummy memory cell if a lower temperature is detected; and
the one or more control circuits are configured to lower gate voltage to the dummy memory cell if a higher temperature is detected.
8. The non-volatile storage apparatus of claim 1 , wherein:
the data memory cell and the dummy memory cell share a common channel region.
9. The non-volatile storage apparatus of claim 1 , wherein:
the plurality of non-volatile memory cells includes additional dummy memory cells on the common NAND string, with the dummy memory cell being a closest dummy memory cell to the select gate.
10. The non-volatile storage apparatus of claim 1 , wherein:
the plurality of non-volatile memory cells form a monolithic three dimensional memory structure.
11. A method for operating non-volatile storage, comprising:
changing threshold voltage of non-volatile data memory cells connected to a first word line;
determining a word line voltage adjustment based on temperature; and
applying a voltage based on the word line voltage adjustment to a dummy word line connected to dummy memory cells during the changing threshold voltage of the data memory cells connected to the first word line, wherein the data memory cells and the dummy memory cells are arranged as one or more NAND strings, in each of which one of the dummy memory cells is located between one of the data memory cells and a select gate, wherein:
the data memory cells, the dummy memory cells, the first word line and the dummy word line are in a block;
the dummy word line is adjacent a select line for the block;
the changing threshold voltage includes erasing the block; and
the applying the voltage based on the word line voltage adjustment to the dummy word line includes applying a higher voltage to the dummy word line in response to a detected higher temperature and applying a lower voltage to the dummy word line in response to a detected lower temperature.
12. The method of claim 11 , wherein:
the applying the voltage based on the word line voltage adjustment to the dummy word line includes causing the dummy memory cells to experience a shallow erase in response to a detected higher temperature and to causing the dummy memory cells to experience a deeper erase in response to a detected lower temperature.
13. The method of claim 11 , wherein:
the changing threshold voltage includes programming the data memory cells; and
the applying the voltage based on the word line voltage adjustment to the dummy word line includes applying a lower voltage to the dummy word line in response to a higher temperature and applying a higher voltage to the dummy word line in response to a lower temperature.
14. The method of claim 11 , further comprising:
determining an additional adjustment based on number of word lines in a block already programmed; and
applying the additional adjustment to the dummy word line during the changing threshold voltage of the data memory cells connected to the first word line.
15. The method of claim 11 , wherein:
each of the data memory cells is connected to one of the dummy memory cells.
16. The non-volatile storage apparatus of claim 5 , wherein:
the data memory cell and the dummy memory cell share a common channel region.
17. The non-volatile storage apparatus of claim 5 , wherein:
the plurality of non-volatile memory cells includes additional dummy memory cells on the common NAND string, with the dummy memory cell being a closest dummy memory cell to the select gate.
18. The non-volatile storage apparatus of claim 5 , wherein:
the plurality of non-volatile memory cells form a monolithic three dimensional memory structure.