# US 11,307,799 B2 · Managing threshold voltage drift based on operating characteristics of a memory sub-system

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- Number: US 11,307,799 B2
- Document ID: US11307799B2
- Status: Granted
- Kind: B2
- Application number: 16/552,165
- Filed: 2019-08-27
- Published: 2021-03-04
- Granted: 2022-04-19
- Earliest claimed: 2019-08-27
- Assignees: Micron Technology, Inc.
- Applicants: Micron Technology, Inc.
- Inventors: Murong Lang; Zhenming Zhou
- Web page: https://patentgrep.com/patent/US11307799B2

## CPC

- G06F 3/0659: {Command handling arrangements, e.g. command buffers, queues, command scheduling}
- G11C 5/147: {Voltage reference generators, voltage or current regulators; Internally lowered supply levels; Compensation for voltage drops (G11C5/141 takes precedence)}
- G06F 3/0614: {Improving the reliability of storage systems}
- G06F 3/0632: {by initialisation or re-initialisation of storage systems}
- G06F 3/0673: {Single storage device}
- G11C 7/1045: {Read-write mode select circuits}
- G11C 7/1051: {Data output circuits, e.g. read-out amplifiers, data output buffers, data output registers, data output level conversion circuits}
- G11C 7/1096: {Write circuits, e.g. I/O line write drivers}
- G11C 7/22: Read-write [R-W] timing or clocking circuits; Read-write [R-W] control signal generators or management
- G11C 29/021: {in voltage or current generators}
- G11C 29/028: {with adaption or trimming of parameters}
- G11C 7/04: with means for avoiding disturbances due to temperature effects
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- G11C: STATIC STORES (semiconductor memory devices H10B)

## Abstract

Multiple sets of values corresponding to operating characteristics of a memory sub-system are established. For each of the sets of values, a read voltage level corresponding to a decreased bit error rate of a programming distribution of the memory sub-system is identified. A data structure is stored that includes the read voltage level for each set of values corresponding to the operating characteristics. In response to a read command, a current set of values of the operating characteristics is determined. Using the data structure, a stored read voltage level corresponding to the current set of values of the operating characteristics is identified. The read command is executed using the stored read voltage level corresponding to the current set of values of the operating characteristics.

## Claims

### Claim 1

A method comprising:
establishing a plurality of sets of values corresponding to a plurality of operating characteristics of a memory sub-system, wherein the plurality of operating characteristics comprises two or more of a write-to-write delay time, a write-to-read delay time, a memory die temperature or a cycling condition;
for each of the plurality of sets of values corresponding to the plurality of operating characteristics, identifying a target read voltage level corresponding to a decreased bit error rate of a programming distribution of the memory sub-system;
storing a data structure including the target read voltage level corresponding to each set of values of the plurality of sets of values corresponding to the plurality of operating characteristics;
in response to a read command associated with a memory cell, measuring a current set of measured values of the plurality of operating characteristics associated with a memory cell;
performing a comparison of the current set of measured values and the set of values associated with the plurality of operating characteristics stored in the data structure to identify a match between a first set of values of the plurality of sets of values corresponding to the plurality of operating characteristics and the current set of measured values;
identifying, using the data structure, a first stored target read voltage level corresponding to the first set of values corresponding to the plurality of operating characteristics matching the current set of measured values; and
executing, by a processing device, the read command using the first stored target read voltage level corresponding to the first set of values of the plurality of sets of values.

### Claim 2 (depends on 1)

The method of claim 1, further comprising performing a look up operation associated with the data structure to determine the first stored target read voltage level corresponding to the first set of values of the plurality of operating characteristics matching the current set of measured values.

### Claim 3 (depends on 1)

The method of claim 1, further comprising performing a write operation to write data to the memory sub-system.

### Claim 4 (depends on 3)

The method of claim 3, further comprising determining a first value of the current set of measured values, wherein the first value comprises a first time difference between the write operation and a previous write operation.

### Claim 5 (depends on 4)

The method of claim 4, further comprising determining a second value of the current set of measured values, wherein the second value comprises a second time difference between the write operation and a time associated with the read command.

### Claim 6 (depends on 5)

The method of claim 5, further comprising:
determining a third value of the current set of measured values, wherein the third value comprises a temperature of a die associated with the read command; and
determining a fourth value of the current set of measured values, wherein the fourth value comprises the cycling condition associated with the memory sub-system.

### Claim 7

A non-transitory computer readable medium comprising instructions, which when executed by a processing device, cause the processing device to perform operations comprising:
establishing a plurality of sets of values corresponding to a plurality of operating characteristics of a memory sub-system, wherein the plurality of operating characteristics comprises two or more of a write-to-write delay time, a write-to-read delay time, a memory die temperature or a cycling condition;
for each of the plurality of sets of values corresponding to the plurality of operating characteristics, identifying a target read voltage level corresponding to a decreased bit error rate of a programming distribution of the memory sub-system;
storing a table including the target read voltage level corresponding to each set of values of the plurality of sets of values corresponding to the plurality of operating characteristics;
in response to a read command associated with a memory cell, measuring a current set of measured values of the plurality of operating characteristics associated with a memory cell;
performing a comparison of the current set of measured values and the set of values associated with the plurality of operating characteristics stored in the table to identify a match between a first set of values of the plurality of sets of values corresponding to the plurality of operating characteristics and the current set of measured values;
identifying, using the table, a first stored target read voltage level corresponding to the first set of values corresponding to the plurality of operating characteristics matching the current set of measured values; and
executing, by a processing device, the read command using the first stored target read voltage level corresponding to the first set of values of the plurality of sets of values.

### Claim 8 (depends on 7)

The non-transitory computer readable medium of claim 7, wherein the table comprises a plurality of target read voltage levels, wherein each of the plurality of target read voltage levels corresponds to approximately a target bit error rate of a programming distribution associated with each set of values of the plurality of operating characteristics.

### Claim 9 (depends on 8)

The non-transitory computer readable medium of claim 8, the operations further comprising:
normalizing the current set of measured values to generate a normalized set of measured values; and
identifying, from the table, the first set of values of the plurality of sets of values that matches the normalized set of measured values.

### Claim 10 (depends on 8)

The non-transitory computer readable medium of claim 8, the operations further comprising performing a write operation to write data to the memory sub-system.

### Claim 11 (depends on 10)

The non-transitory computer readable medium of claim 10, the operations further comprising determining a first value of the current set of measured values, wherein the first value comprises a first time difference between the write operation and a previous write operation.

### Claim 12 (depends on 11)

The non-transitory computer readable medium of claim 11, the operations further comprising:
determining a second value of the current set of measured values, wherein the second value comprises a second time difference between the write operation and a time associated with the read command;
determining a third value of the current set of measured values, wherein the third value comprises a temperature of a die associated with the read command; and
determining a fourth value of the current set of measured values, wherein the fourth value comprises the cycling condition associated with the memory sub-system.

### Claim 13

A system comprising:
a memory component; and
a processing device, operatively coupled with the memory component, to:
establish a plurality of sets of values corresponding to a plurality of operating characteristics of a memory sub-system, wherein the plurality of operating characteristics comprises two or more of a write-to-write delay time, a write-to-read delay time, a memory die temperature or a cycling condition;
for each of the plurality of sets of values corresponding to the plurality of operating characteristics, identify a target read voltage level corresponding to a decreased bit error rate of a programming distribution of the memory sub-system;
store a data structure including the target read voltage level corresponding to each set of values of the plurality of sets of values corresponding to the plurality of operating characteristics;
in response to a read command associated with a memory cell, measure a current set of measured values of the plurality of operating characteristics associated with a memory cell;
identify a match between a first set of values corresponding to the plurality of operating characteristics stored in the data structure and the current set of measured values;
performing a comparison of the current set of values and the set of values associated with the plurality of operating characteristics stored in the data structure to identify a match between a first set of values of the plurality of sets of values corresponding to the plurality of operating characteristics and the current set of measured values; and
execute the read command using a first stored target read voltage level corresponding to the first set of values of the plurality of sets of values.

### Claim 14 (depends on 13)

The system of claim 13, wherein the processing device is further to:
perform a look up operation associated with the data structure to determine the first stored target read voltage level corresponding to the first set of values of the plurality of operating characteristics matching the current set of measured values.

### Claim 15 (depends on 13)

The system of claim 13, wherein the processing device is further to perform a write operation to write data to the memory sub-system.

### Claim 16 (depends on 15)

The system of claim 15, wherein the processing device is further to determine a first value of the current set of measured values, wherein the first value comprises a first time difference between the write operation and a previous write operation.

### Claim 17 (depends on 16)

The system of claim 16, wherein the processing device is further to determine a second value of the current set of measured values, wherein the second value comprises a second time difference between the write operation and a time associated with the read command.

### Claim 18 (depends on 17)

The system of claim 17, wherein the processing device is further to:
determine a third value of the current set of measured values, wherein the third value comprises a temperature of a die associated with the read command; and
determine a fourth value of the current set of measured values, wherein the fourth value comprises the cycling condition associated with the memory sub-system.