Reducing floating gate to floating gate coupling effect
View Patent ↗For a non-volatile memory system, compressing the erase threshold voltage distribution into the lowest threshold voltage state will decrease the valid data threshold voltage window. Decreasing the valid data threshold voltage window reduces the floating gate to floating gate coupling effect. The compression can be performed as part of the erase process or part of the programming operation.
1. A method for operating non-volatile memory, comprising:
erasing a set of non-volatile storage elements by intentionally moving threshold voltages for said non-volatile storage elements to a first range of threshold voltages, said first range is below zero volts, said first range is not a valid data range;
compressing said threshold voltages and moving said threshold voltages from said first range to a second range of threshold voltages, said second range is above zero volts; and
programming at least a subset of said non-volatile storage elements from said second range to one or more of additional ranges above zero volts, said second range and said additional ranges above zero volts are valid data ranges.
2. A method according to claim 1 , further comprising:
receiving a request to program said subset of said non-volatile storage elements subsequent to said compressing, said programming at least a subset of said non-volatile storage elements is performed in response to said request to program.
3. A method according to claim 1 , further comprising:
receiving a request to program said subset of said non-volatile storage elements prior to said compressing, said programming at least a subset of said non-volatile storage elements and said compressing is performed in response to said request to program.
4. A method according to claim 1 , wherein:
said moving said threshold voltages to said second range includes moving said threshold voltages to a first valid data state of eight valid data states; and
said programming includes moving threshold voltages for said subset of said non-volatile storage elements to any of a second valid data state, a third valid data state, a fourth valid data state, a fifth valid data state, a sixth valid data state, a seventh valid data state or an eighth valid data state.
5. A method according to claim 1 , further comprising:
pre-programming said non-volatile storage elements prior to said erasing.
6. A method according to claim 1 , wherein:
said erasing includes removing charge from floating gates for said non-volatile storage elements; and
said compressing and moving includes adding charge to floating gates for said non-volatile storage elements.
7. A method according to claim 1 , wherein:
said non-volatile storage elements are multi-state NAND flash memory elements.
8. A method according to claim 1 , wherein:
said non-volatile storage elements are multi-state flash memory elements.
9. A method according to claim 8 , wherein:
each of said non-volatile storage elements store data in multiple pages.
10. A method according to claim 8 , wherein:
each of said non-volatile storage elements store data in multiple pages; and
said programming includes writing to a particular non-volatile storage element with respect to a particular page subsequent to writing to adjacent non-volatile storage elements for previous pages.
11. A method according to claim 1 , wherein:
said moving said threshold voltages to said second range includes moving said threshold voltages to a first valid data state of four or more valid data states; and
said programming includes moving threshold voltages for said subset of said non-volatile storage elements from said first valid data state to any other of said four or more valid data states.
12. A non-volatile memory system, comprising:
a plurality of non-volatile storage elements; and
one or more control circuits in communication with said non-volatile storage elements, said one or more control circuits erase said non-volatile storage elements by intentionally lowering threshold voltages for said non-volatile storage elements to levels below zero volts, compress said threshold voltages and raise said threshold voltages to levels above zero volts, and program at least a subset of said non-volatile storage elements from said levels above zero volts to one or more valid programmed data states, said levels below zero volts do not include a valid data range.
13. A non-volatile memory system according to claim 12 , wherein:
said programming of at least a subset of said non-volatile storage elements and said compressing are performed in response to a request to program.
14. A non-volatile memory system according to claim 12 , wherein:
said non-volatile storage elements are multi-state NAND flash memory elements.
15. A non-volatile memory system according to claim 12 , wherein:
said levels above zero voltage correspond to a first valid data state of four or more valid data states; and
said one or more valid programmed data states correspond to other valid data states of said four or more valid data states.
16. A non-volatile memory system, comprising:
a plurality of non-volatile storage elements, each of said non-volatile storage elements store data in multiple pages said non-volatile storage elements are multi-state NAND flash memory elements; and
one or more control circuits in communication with said non-volatile storage elements, said one or more control circuits erase said non-volatile storage elements by lowering threshold voltages for said non-volatile storage elements to levels below zero volts, compress said threshold voltages and raise said threshold voltages to levels above zero volts, and program at least a subset of said non-volatile storage elements from said levels above zero volts to one or more valid data states by programming a particular non-volatile storage element with respect to a particular page subsequent to programming adjacent non-volatile storage elements for previous pages.
17. A method for operating non-volatile memory, comprising:
erasing a set of non-volatile storage elements by intentionally moving threshold voltages for said non-volatile storage elements to a first range, said first range is associated with non-valid data;
moving said threshold voltages for said non-volatile storage elements to a second range different than said first range, said second range is associated with valid data; and
progranmiing at least a subset of said non-volatile storage elements from said second range to one or more of other ranges associated with valid data.
18. A method according to claim 17 , further comprising:
receiving a request to program subsequent to said moving, said programming at least a subset of said non-volatile storage elements is performed in response to said request to program.
19. A method according to claim 17 , further comprising:
receiving a request to program prior to said moving, said programming at least a subset of said non-volatile storage elements and said moving are performed in response to said request to program.
20. A method according to claim 17 , further comprising:
pre-programming said non-volatile storage elements prior to said erasing.
21. A method according to claim 17 , wherein:
said non-volatile storage elements are multi-state NAND flash memory elements.
22. A method according to claim 21 , wherein:
each of said non-volatile storage elements store data in multiple pages; and
said programming includes writing to a particular non-volatile storage element with respect to a particular page subsequent to writing to adjacent non-volatile storage elements for previous pages.
23. A method according to claim 17 , wherein:
said moving said threshold voltages includes compressing said threshold voltages.
24. A non-volatile memory system, comprising:
a plurality of non-volatile storage elements; and
one or more control circuits in coimnunication with said non-volatile storage elements, said one or more control circuits erase a set of non-volatile storage elements by intentionally moving threshold voltages for said non-volatile storage elements from valid data ranges to a non-valid data range, compress said threshold voltages and move said threshold voltages to a first range of said valid data ranges and program at least a subset of said non-volatile storage elements from said first range of said valid ranges to one or more of add other ranges of said valid data ranges.
25. A non-volatile memory system according to claim 24 , wherein:
said non-volatile storage elements are multi-state NAND flash memory elements.
26. A non-volatile memory system according to claim 24 , wherein:
said non-valid data range is below zero volts; and said valid data ranges are above zero volts.
27. A method for erasing non-volatile memory, comprising:
erasing a set of non-volatile storage elements by intentionally moving threshold voltages for said non-volatile storage elements to a particular range outside of valid data ranges; and
compressing said threshold voltages and moving said threshold voltages from said particular range to a valid data range.
28. A method according to claim 27 , wherein:
said erasing includes applying an erase pulse to said non-volatile storage elements so that threshold voltages for said non-volatile storage elements are lowered to form a threshold voltage distribution below ranges used to represent valid data; and
said compressing includes raising threshold voltages for said non-volatile storage elements to a range representing a valid data state.
29. A method according to claim 28 , wherein:
said threshold voltage distribution is below zero volts; and
said valid data state is above zero volts.
30. A method according to claim 29 , wherein:
said non-volatile storage elements are multi-state NAND flash memory elements.