Granted Patent B2

US 10,679,708 · App. 16/133,552 · Granted Jun 9, 2020

Abstract

Claims (30)

1. A method, comprising:

performing a read operation on a first portion of a flash memory in response to an erase operation on a second portion of the flash memory, wherein the first portion comprises a plurality of logical wordlines corresponding to a plurality of physical wordlines of the second portion, and wherein the first portion is at least a subset of the second portion;

counting, for each of the plurality of logical wordlines, a number of memory cells exceeding a threshold error voltage;

marking, in an error bitmap, whether each of the plurality of physical wordlines is defective based on the count satisfying a threshold error count for the respective one of the plurality of logical wordlines;

receiving a request to perform a write operation into a third portion of the flash memory that includes at least one physical wordline marked as defective in the error bitmap; and

performing the write operation, wherein the write operation writes a predetermined data pattern to the at least one physical wordline,

wherein:

the first portion includes first memory cells;

the second portion includes the first memory cells and second memory cells;

the second memory cells are different from the first memory cells; and

in response to the erase operation on the first memory cells and the second memory cells of the second portion, the read operation is performed on the first memory cells but not on the second memory cells.

2. The method of claim 1 , wherein the write operation writes the predetermined data pattern to a lower page of the at least one physical wordline.

3. The method of claim 2 , wherein the first portion of the flash memory excludes pages other than lower pages of the second portion.

4. The method of claim 2 , wherein the erase operation senses a current in each of a plurality of strings within the second portion, and wherein the first portion is selected from the plurality of strings based on whether the sensed current for each of the plurality of strings is below a leakage threshold.

5. The method of claim 1 , wherein the predetermined data pattern is not based on data for the write operation.

6. The method of claim 5 , wherein the predetermined data pattern comprises a repeating data string.

7. The method of claim 1 , wherein the threshold error voltage is a zero (0) voltage.

8. The method of claim 1 , wherein the counting comprises one of toggling the first portion of the flash memory to a storage controller or reading latches of the flash memory.

9. The method of claim 1 , wherein:

a first logical wordline of the plurality of logical wordlines corresponds to a first physical wordline of the plurality of physical wordlines;

the first logical wordline includes fewer memory cells than the first physical wordline;

the first logical wordline includes a first memory portion of the first memory cells;

the first physical wordline includes the first memory portion of the first memory cells and a second memory portion of the second memory cells;

the first memory portion is different from the second memory portion;

in response to the erase operation on the first physical wordline including the first memory portion and the second memory portion, the read operation is performed on the first memory portion but not on the second memory portion;

the counting comprises counting, for the first memory portion, a first number of memory cells exceeding the threshold error voltage; and

the marking comprises marking, in the error bitmap, whether the first memory portion and the second memory portion are defective, based on the first number, for the first memory portion, satisfying the threshold error count, but not based on an error count for the second memory portion.

10. The method of claim 9 , wherein:

the at least one physical wordline is the first physical wordline; and

the write operation writes the predetermined data pattern to the first memory portion of the first physical wordline but not to the second memory portion of the first physical wordline.

Assignments (10)