# US 10,872,676 B2 · Methods of performing read count leveling for multiple portions of a block of memory cells

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- Number: US 10,872,676 B2
- Document ID: US10872676B2
- Status: Granted
- Kind: B2
- Application number: 16/433,193
- Filed: 2019-06-06
- Published: 2019-09-19
- Granted: 2020-12-22
- Earliest claimed: 2019-06-06
- Assignees: Micron Technology, Inc.
- Applicants: Micron Technology, Inc.
- Inventors: Ke Liang; Jun Xu
- Web page: https://patentgrep.com/patent/US10872676B2

## CPC

- G11C 16/349: {Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles}
- G11C 16/0483: {comprising cells having several storage transistors connected in series}
- G11C 16/10: Programming or data input circuits
- G11C 16/26: Sensing or reading circuits; Data output circuits
- G11C 16/3427: {Circuits or methods to prevent or reduce disturbance of the state of a memory cell when neighbouring cells are read or written}
- G11C 16/14: Circuits for erasing electrically, e.g. erase voltage switching circuits
- G11C: STATIC STORES (semiconductor memory devices H10B)

## Abstract

Methods include incrementing a first read count in response to performing a read operation on a memory cell of a block of memory cells, the first read count corresponding to a first portion of memory cells of the block of memory cells; incrementing a second read count in response to performing the read operation on the memory cell of the block of memory cells, the second read count corresponding to a second portion of memory cells of the block of memory cells; resetting the first read count in response to performing an erase operation on the first portion of memory cells of the block of memory cells; and resetting the second read count in response to performing an erase operation on the second portion of memory cells of the block of memory cells.

## Claims

### Claim 1

A method, comprising:
incrementing a first read count in response to performing a read operation on a memory cell of a first portion of memory cells of a block of memory cells, the first read count corresponding to the first portion of memory cells of the block of memory cells;
incrementing a second read count in response to performing the read operation on the memory cell of the first portion of memory cells of the block of memory cells, the second read count corresponding to a second portion of memory cells of the block of memory cells;
incrementing the first read count in response to performing a read operation on a memory cell of the second portion of memory cells of the block of memory cells;
incrementing the second read count in response to performing the read operation on the memory cell of the second portion of memory cells of the block of memory cells;
resetting the first read count in response to performing an erase operation on the first portion of memory cells of the block of memory cells; and
resetting the second read count in response to performing an erase operation on the second portion of memory cells of the block of memory cells.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
in response to a value of the first read count reaching a threshold:
copying data of the first portion of memory cells to a free portion of memory cells; and
after copying the data of the first portion of memory cells, erasing the first portion of memory cells; and
in response to a value of the second read count reaching the threshold:
copying data of the second portion of memory cells to a free portion of memory cells; and
after copying the data of the second portion of memory cells, erasing the second portion of memory cells.

### Claim 3 (depends on 2)

The method of claim 2, wherein copying the data of the first portion of memory cells to the free portion of memory cells comprises copying the data of the first portion of memory cells to a free portion of memory cells of a different block of memory cells.

### Claim 4 (depends on 2)

The method of claim 2, wherein copying the data of the first portion of memory cells to the free portion of memory cells comprises copying the data of the first portion of memory cells to a free portion of memory cells of the second portion of memory cells.

### Claim 5 (depends on 2)

The method of claim 2, wherein copying the data of the second portion of memory cells to the free portion of memory cells comprises copying the data of the second portion of memory cells to a free portion of memory cells of a different block of memory cells.

### Claim 6 (depends on 2)

The method of claim 2, wherein copying the data of the second portion of memory cells to the free portion of memory cells comprises copying the data of the second portion of memory cells to a free portion of memory cells of the first portion of memory cells.

### Claim 7 (depends on 2)

The method of claim 2, further comprising setting a value of the threshold in response to a page level read capability for the block of memory cells.

### Claim 8 (depends on 7)

The method of claim 7, wherein setting the value of the threshold comprises setting the value of the threshold to be less than a number corresponding to the page level read capability.

### Claim 9

A method, comprising:
incrementing a first read count in response to performing a read operation on a memory cell of a block of memory cells, the first read count corresponding to a first portion of memory cells of the block of memory cells;
incrementing a second read count in response to performing the read operation on the memory cell of the block of memory cells, the second read count corresponding to a second portion of memory cells of the block of memory cells;
resetting the first read count in response to performing an erase operation on the first portion of memory cells of the block of memory cells;
resetting the second read count in response to performing an erase operation on the second portion of memory cells of the block of memory cells;
in response to a value of the first read count reaching a threshold:
copying data of the first portion of memory cells to a free portion of memory cells; and
after copying the data of the first portion of memory cells, erasing the first portion of memory cells;
in response to a value of the second read count reaching the threshold:
copying data of the second portion of memory cells to a free portion of memory cells; and
after copying the data of the second portion of memory cells, erasing the second portion of memory cells; and
setting a value of the threshold in response to a page level read capability for the block of memory cells, comprising setting the value of the threshold to be less than or equal to the page level read capability times a number of pages of memory cells contained in the block of memory cells.

### Claim 10 (depends on 1)

The method of claim 1, wherein the block of memory cells comprises a plurality of strings of series-connected memory cells, wherein the first portion of memory cells of the block of memory cells comprises a respective portion of each string of series-connected memory cells of the plurality of strings of series-connected memory cells that is closer to any data line selectively connected to the block of memory cells than any memory cell of the second portion of memory cells, and wherein the second portion of memory cells of the block of memory cells comprises a respective portion of each string of series-connected memory cells of the plurality of strings of series-connected memory cells that is closer to a source selectively connected to the block of memory cells than any memory cell of the first portion of memory cells.

### Claim 11

A method, comprising:
incrementing a first read count in response to performing a read operation on a memory cell of a block of memory cells, the first read count corresponding to a first portion of memory cells of the block of memory cells;
incrementing a second read count in response to performing the read operation on the memory cell of the block of memory cells, the second read count corresponding to a second portion of memory cells of the block of memory cells;
resetting the first read count in response to performing an erase operation on the first portion of memory cells of the block of memory cells;
resetting the second read count in response to performing an erase operation on the second portion of memory cells of the block of memory cells; and
incrementing the first read count and the second read count in response to performing a read operation on any memory cell of the block of memory cells.

### Claim 12 (depends on 1)

The method of claim 1, wherein resetting the first read count in response to performing the erase operation on the first portion of memory cells of the block of memory cells further comprises maintaining a value of the second read count in response to performing the erase operation on the first portion of memory cells of the block of memory cells.

### Claim 13 (depends on 12)

The method of claim 12, further comprising wherein resetting the second read count in response to performing the erase operation on the second portion of memory cells of the block of memory cells further comprises maintaining a value of the first read count in response to performing the erase operation on the second portion of memory cells of the block of memory cells.

### Claim 14

A method, comprising:
for each memory cell of a first portion of memory cells of a block of memory cells and a second portion of memory cells of the block of memory cells mutually exclusive of the first portion of memory cells;
incrementing a first read count in response to performing a read operation on a that memory cell of the block of memory cells, the first read count corresponding to the first portion of memory cells;
incrementing a second read count in response to performing the read operation on that memory cell of the block of memory cells, the second read count corresponding to the second portion of memory cells;
resetting the first read count in response to performing an erase operation on the first portion of memory cells without performing an erase operation on the second portion of memory cells;
resetting the second read count in response to performing an erase operation on the second portion of memory cells without performing an erase operation on the first portion of memory cells; and
resetting the first read count and the second read count in response to performance a single erase operation on the first portion of memory cells and on the second portion of memory cells.

### Claim 15 (depends on 14)

The method of claim 14, wherein the block of memory cells is a first block of memory cells, the method further comprising:
in response to a value of the first read count reaching a threshold:
copying data of the first portion of memory cells to a free portion of memory cells selected from a group consisting of a free portion of memory cells of the second portion of memory cells, and a free portion of memory cells of a second block of memory cells different than the first block of memory cells; and
after copying the data of the first portion of memory cells, performing an erase operation on the first portion of memory cells; and
in response to a value of the second read count reaching the threshold:
copying data of the second portion of memory cells to a free portion of memory cells selected from a group consisting of a free portion of memory cells of the first portion of memory cells, and a free portion of memory cells of a third block of memory cells different than the first block of memory cells; and
after copying the data of the second portion of memory cells, performing an erase operation on the second portion of memory cells.

### Claim 16 (depends on 15)

The method of claim 15, wherein copying the data of the second portion of memory cells to the free portion of memory cells of the third block of memory cells different than the first block of memory cells further comprises copying the data of the second portion of memory cells to the free portion of memory cells of the third block of memory cells different than the first block of memory cells and different than the second block of memory cells.

### Claim 17

A method, comprising:
for each memory cell of a block of memory cells;
incrementing a first read count in response to performing a read operation on that memory cell of the block of memory cells, the first read count corresponding to a first portion of memory cells of the block of memory cells;
incrementing a second read count in response to performing the read operation on that memory cell of the block of memory cells, the second read count corresponding to a second portion of memory cells of the block of memory cells mutually exclusive of the first portion of memory cells;
in response to a value of the first read count reaching a threshold while a value of the second read count is below the threshold value:
copying data of the first portion of memory cells to a free portion of memory cells;
after copying the data of the first portion of memory cells, performing an erase operation on the first portion of memory cells without performing an erase operation on the second portion of memory cells; and
resetting the first read count in response to performing the erase operation on the first portion of memory cells without resetting the second read count;
in response to a value of the second read count reaching the threshold while the value of the first read count is below the threshold value:
copying data of the second portion of memory cells to a free portion of memory cells;
after copying the data of the second portion of memory cells, performing an erase operation on the second portion of memory cells without performing an erase operation on the second portion of memory cells; and
resetting the second read count in response to performing the erase operation on the second portion of memory cells without resetting the first read count; and
in response to the value of the first read count and the value of the second read count reaching the threshold value:
copying data of the block of memory cells to a free block of memory cells;
after copying the data of the block of memory cells, performing an erase operation on the block of memory cells; and
resetting the first read count and the second read count in response to performing the erase operation on the block of memory cells.

### Claim 18 (depends on 17)

The method of claim 17, wherein copying the data of the first portion of memory cells to the free portion of memory cells comprises copying the data of the first portion of memory cells to a free portion of memory cells selected from a group consisting of a free portion of memory cells of the second portion of memory cells, and a free portion of memory cells of a different block of memory cells.

### Claim 19 (depends on 17)

The method of claim 17, wherein copying the data of the second portion of memory cells to the free portion of memory cells comprises copying the data of the second portion of memory cells to a free portion of memory cells selected from a group consisting of a free portion of memory cells of the first portion of memory cells, and a free portion of memory cells of a different block of memory cells.

### Claim 20 (depends on 17)

The method of claim 17, wherein performing the erase operation on the first portion of memory cells after copying the data of the first portion of memory cells in response to the value of the first read count reaching the threshold while the value of the second read count is below the threshold value comprises performing the erase operation on the first portion of memory cells without erasing the second portion of memory cells, and wherein performing the erase operation on the second portion of memory cells after copying the data of the second portion of memory cells in response to the value of the second read count reaching the threshold while the value of the first read count is below the threshold value comprises performing the erase operation on the second portion of memory cells without erasing the first portion of memory cells.