US 2008/0259684 A1Published application

Programming a NAND flash memory with reduced program disturb

AssigneeSanDisk IL Ltd.

InventorsMark Shlick, Mark Murin

Life of this patent

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Abstract

When a memory device receives two or more pluralities of bits from a host to store in a nonvolatile memory, the device first stores the bits in a volatile memory. Then, in storing the bits in the nonvolatile memory, the device raises the threshold voltages of some cells of the volatile memory to values above a verify voltage. While those threshold voltages remain substantially at those levels, the device raises the threshold voltages of other cells of the volatile memory to values below the verify voltage. In the end, every cell stores one or more bits from each plurality of bits. Preferably, all the cells share a common wordline. A data storage device operates similarly with respect to storing pluralities of bits generated by an application running on the system.

Claims11

Dependent claims

A method of storing data in a memory device, comprising the steps of:

(a) receiving, from a host of the memory device, at least two pluralities of bits to store in a plurality of cells of a nonvolatile memory of the memory device;
(b) storing said at least two pluralities of bits in a volatile memory of the memory device;
and
(c) subsequent to said storing of said at least two pluralities of bits in said volatile memory, storing said at least two pluralities of bits in said plurality of cells, by steps including:
(i) raising a threshold voltage of a first at least one of said cells to a first value that is greater than a verify voltage;
and
(ii) while said threshold voltage of each said first at least one cell remains substantially at said first value, raising a threshold voltage of a second at least one of said cells to a second value that is less than said verify voltage;
wherein at least one bit of each of said pluralities of bits is stored in at least one of said cells.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 11/806,111Filed 30 May 2007
Priority: 7 Nov 2006
Published: 23 Oct 2008
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G11C 16/0483
Using variable threshold transistors, e.g. FAMOS: comprising cells having several storage transistors connected in series
G11C 11/5628
Using charge storage in a floating gate: programming or writing circuits; Data input circuits
G11C 16/3418
Determination of programming status, e.g. threshold voltage, overprogramming or underprogramming, retention: disturbance prevention or evaluation;…
G11C 16/3427
Disturbance prevention or evaluation; Refreshing of disturbed memory data: circuits or methods to prevent or reduce disturbance of the state of a…