NROM NON-VOLATILE MEMORY AND MODE OF OPERATION
First Claim
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1. A method for operating a plurality of NVM memory cells comprising:
- performing an erase step using Fowler-Nordheim tunneling (FNT) to establish a high initial threshold voltage (Vt) for the plurality of memory cells;
performing a first programming step using hot hole injection (HHI) to reduce the threshold voltage (Vt) of selected ones of the memory cells; and
performing a second programming step using channel hot electron (CHE) injection to increase the threshold voltage (Vt) of bits of memory cells that are unnecessarily programmed in the first programming step.
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Abstract
Operating NVM memory cell such as an NROM cell by using a combination of Fowler-Nordheim tunneling (FNT), hot hole injection (HHI), and channel hot electron (CHE) injection. In the FNT erase step, only a few cells may be verified, and in the CHE second programming step, the threshold voltage of those cells which were not fully erased in the FNT erase step is increased to a high threshold voltage level (ERS state).
117 Citations
15 Claims
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1. A method for operating a plurality of NVM memory cells comprising:
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performing an erase step using Fowler-Nordheim tunneling (FNT) to establish a high initial threshold voltage (Vt) for the plurality of memory cells; performing a first programming step using hot hole injection (HHI) to reduce the threshold voltage (Vt) of selected ones of the memory cells; and performing a second programming step using channel hot electron (CHE) injection to increase the threshold voltage (Vt) of bits of memory cells that are unnecessarily programmed in the first programming step. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for programming a plurality of memory cells, each cell having a characteristic program voltage (PV) and a characteristic erase voltage (EV), the method comprising the steps of:
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(a) erasing the plurality of memory cells by increasing a threshold voltage (Vt) of the cells to greater than the erase voltage (Vt>
EV);(b) programming first selected ones of the cells by decreasing the threshold voltage of the first selected ones of the cells to less than the program voltage (Vt<
PV); and(c) refreshing second selected ones of the cells by increasing the threshold voltage (Vt) of the cells to greater than the erase voltage (Vt>
EV). - View Dependent Claims (10, 11)
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12. A method of operating a NVM memory cell comprising:
using a combination of Fowler-Nordheim tunneling (FNT), hot hole injection (HHI), and channel hot electron (CHE) injection. - View Dependent Claims (13, 14)
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15. A method for operating a plurality of NVM memory cells comprising:
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performing an erase step using Fowler-Nordheim tunneling (FNT) to establish a high initial threshold voltage (Vt) for the plurality of memory cells; verifying only a few of the plurality of cells; programming selected ones of the plurality of cells to a low threshold voltage; and using channel hot electron (CHE) injection to raise the threshold voltage of selected ones of those cells which were not fully erased in the FNT erase step, and which are desired to be at the high threshold voltage.
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Specification