# US 2019/0318798 A1 · Defective Memory Unit Screening in a Memory System

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- Number: US 2019/0318798 A1
- Document ID: US20190318798A1
- Status: Published application
- Kind: A1
- Application number: 15/952,166
- Filed: 2018-04-12
- Published: 2019-10-17
- Earliest claimed: 2018-04-12
- Assignees: Micron Technology, Inc.
- Applicants: Micron Technology, Inc.
- Inventors: Alex Frolikov
- Web page: https://patentgrep.com/patent/US20190318798A1

## CPC

- G06F 11/1048: {using arrangements adapted for a specific error detection or correction feature}
- G11C 29/44: Indication or identification of errors, e.g. for repair
- G06F 3/0619: {in relation to data integrity, e.g. data losses, bit errors}
- G06F 3/0634: {by changing the state or mode of one or more devices}
- G06F 3/0679: {Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]}
- G06F 11/0727: {in a storage system, e.g. in a DASD or network based storage system (drivers for digital recording or reproducing units G06F3/06; circuits for error detection or correction within digital recording or reproducing units G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097)}
- G06F 11/076: {by exceeding a count or rate limit, e.g. word- or bit count limit}
- G06F 11/0793: {Remedial or corrective actions (recovery from an exception in an instruction pipeline G06F9/3861; by retry G06F11/1402; for recovering from a failure of a protocol instance or entity H04L69/40)}
- G11C 29/38: Response verification devices
- G11C 2029/0411: {Online error correction}
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- G11C: STATIC STORES (semiconductor memory devices H10B)

## Abstract

A memory system having non-volatile media and a controller configured to process requests from a host system to store data in the non-volatile media or retrieve data from the non-volatile media. The non-volatile media has a set of memory units. The memory system stores an indicator indicating whether the memory system is operating in a user mode or a manufacturing mode. A defect manager of the memory system identifies a threshold based on the indicator, monitors an error rate in reading data from the non-volatile media and, in response to the error rate reaching the threshold, screens the non-volatile media for defective memory units.

## Claims

### Claim 1

A memory system, comprising:
non-volatile media having a set of memory units;
a controller configured to process requests from a host system to store data in the non-volatile media or retrieve data from the non-volatile media;
wherein the memory system stores an indicator indicating whether the memory system is operating in a user mode or a manufacturing mode; and
wherein a defect manager of the memory system identifies a threshold based on the indicator, monitors an error rate in reading data from the non-volatile media and, in response to the error rate reaching the threshold, screens the non-volatile media for defective memory units.

### Claim 2 (depends on 1)

The memory system of claim 1, wherein the non-volatile media includes a flash memory.

### Claim 3 (depends on 2)

The memory system of claim 2, wherein the memory system is a solid-state drive.

### Claim 4 (depends on 3)

The memory system of claim 3, wherein the threshold is lower when the memory system is operating in the manufacturing mode than when the memory system is operating in the user mode.

### Claim 5 (depends on 4)

The memory system of claim 4, wherein when the memory system is operating in the manufacturing mode the controller is configured to perform at least one function that is not performed in the user mode.

### Claim 6 (depends on 5)

The memory system of claim 5, wherein the function relates to testing or diagnosis in a manufacturing facility.

### Claim 7 (depends on 5)

The memory system of claim 5, wherein after completion of manufacturing of the memory system, the indicator is adjusted to indicate that the memory system is operating in the user mode.

### Claim 8 (depends on 5)

The memory system of claim 5, wherein during screening of the non-volatile media for defective memory units, the defect manager identifies memory units that have errors in retrieved data after retrying reading for more than a threshold number of times.

### Claim 9 (depends on 5)

The memory system of claim 5, wherein during screening of the non-volatile media for defective memory units, the defect manager identifies memory units that fail to store data correctly.

### Claim 10 (depends on 5)

The memory system of claim 5, wherein the defect manager identifies a priority for screening defective memory units based on an error log.

### Claim 11 (depends on 5)

The memory system of claim 5, wherein the indicator is set by the host system during a power-on startup operation.

### Claim 12

A method, comprising:
processing, by a controller of a memory system having non-volatile media, requests from a host system to store data in the non-volatile media or retrieve data from the non-volatile media, the non-volatile media having a set of memory units;
storing, in the memory system, an indicator indicating whether the memory system is operating in a user mode or a manufacturing mode;
identifying, by a defect manager of the memory system, a threshold based on the indicator;
monitoring, by the defect manager, an error rate in reading data from the non-volatile media; and
in response to the error rate reaching the threshold, screening by the defect manager the non-volatile media for defective memory units.

### Claim 13 (depends on 12)

The method of claim 12, wherein the non-volatile media includes a flash memory; the memory system is a solid-state drive; and the host system and the memory system communicate over a communication channel in accordance with a communication protocol for peripheral component interconnect express bus.

### Claim 14 (depends on 13)

The method of claim 13, wherein:
in response to the memory system operating in the manufacturing mode, a manufacturing mode threshold is identified; and
the screening of the non-volatile media for defective memory units is in response to the error rate reaching the manufacturing mode threshold;
in response to the memory system operating in the user mode, a user mode threshold is identified; and
the screening of the non-volatile media for defective memory units is in response to the error rate reaching the user mode threshold; and
the manufacturing mode threshold is lower than the user mode threshold.

### Claim 15 (depends on 14)

The method of claim 14, further comprising:
in response to the memory system operating in the manufacturing mode,
performing by the controller at least one testing or diagnosis function that is not performed in the user mode.

### Claim 16 (depends on 15)

The method of claim 15, wherein the screening of the non-volatile media for defective memory units includes identifying memory units that have errors in retrieved data after retrying reading for more than a threshold number of times.

### Claim 17 (depends on 16)

The method of claim 16, wherein the screening of the non-volatile media for defective memory units includes identifying memory units that fail to store data.

### Claim 18 (depends on 17)

The method of claim 17, further comprising:
identifying a priority for screening defective memory units based on a log of errors recorded in reading data from memory units where errors are removed via at least one of:
retry of read operations; and
error correction made using redundant information.

### Claim 19

A non-transitory computer storage medium storing instructions which, when executed by a memory system having non-volatile media, and a controller, cause the memory system to perform a method, the method comprising:
processing, by the controller, requests from a host system to store data in the non-volatile media or retrieve data from the non-volatile media, the non-volatile media having a set of memory units;
identifying a threshold based on whether the memory system is operating in a user mode or a manufacturing mode;
monitoring an error rate in reading data from the non-volatile media; and
in response to the error rate reaching the threshold, screening the non-volatile media for defective memory units.

### Claim 20 (depends on 19)

The non-transitory computer storage medium of claim 19, wherein:
when the memory system is operating in the manufacturing mode, a manufacturing mode threshold is identified; and
the screening of the non-volatile media for defective memory units is in response to the error rate reaching the manufacturing mode threshold;
when the memory system is operating in the user mode, a user mode threshold is identified; and
the screening of the non-volatile media for defective memory units is in response to the error rate reaching the user mode threshold; and
the manufacturing mode threshold is lower than the user mode threshold.