Method and system for programming and inhibiting multi-level, non-volatile memory cells
AssigneeSanDisk Corporation
InventorsKhandker N. Quader, Khanh T. Nguyen, Feng Pan, Long C. Pham, Alexander K. Mak
Life of this patent
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Abstract
A multi-level non-volatile memory cell programming/lockout method and system are provided. The programming/lockout method and system advantageously prevent memory cells that charge faster than other memory cells from being over-programmed.
Claims12
A method of programming a plurality of memory cells in a nonvolatile memory array to a plurality of threshold voltage ranges where each of the plurality of threshold voltage ranges represents a different logical state, comprising:
- programming each of the plurality of cells from a base state to a first threshold voltage range representing a first logical state, ones of the plurality of cells that reach the first threshold voltage range being inhibited until all of the plurality of cells are in the first threshold voltage range;
- and
- subsequently programming selected ones of the plurality of cells to a second threshold voltage range representing a second logical state while unselected ones of the plurality of cells are maintained with threshold voltages in the first threshold voltage range.
A method of programming an individual one of a plurality of cells to a higher one of a plurality of threshold voltages comprising:
- first programming the individual one of the plurality of cells from an initial threshold voltage to a lower one of the plurality of threshold voltages;
- subsequently inhibiting the one of the plurality of cells at the lower one of the plurality of threshold voltages until all other ones of the plurality of cells to be programmed to the lower one of the plurality of threshold voltages or higher has reached the lower one of the plurality of threshold voltages;
- and
- subsequently programming the one of the plurality of cells from the lower one of the plurality of threshold voltages to the higher one of the plurality of voltages.
Dependencies are inferred from the claim text.