Storage device and read reclaim method thereof

Patent metadata

Field	Value
Publication number	US-10310924-B2
Application number	US-201615376227-A
Country	US
Kind code	B2
Filing date	Dec 12, 2016
Priority date	Dec 18, 2015
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

A read reclaim method of a storage device includes detecting, at a cycle of a random number of read operations, the number of error bits within non-selection data stored in each of a plurality of memory blocks. A memory block having the number of detected error bits, with respect to the number of read operations, increasing at a rate greater than a reference rate over one or more cycles of the random number of read operations is selected as a weak block. The number of error bits within non-selection data stored in the weak block is detected at a cycle of a fixed number of read operations. A detection is made of whether the number of error bits detected according to the fixed-number cycle is greater than or equal to a read reclaim reference. The non-selection data is data not requested by a host.

First claim

What is claimed is:

1. A read reclaim method of a storage device, the method comprising:
detecting first error bits within first non-selection data stored in each of a plurality of memory blocks of the storage device when a first read count of each of the plurality of memory blocks corresponds to a random number, wherein the first read count of each of the plurality of memory blocks is increased by a first read request;
selecting, as a weak block, a memory block of the plurality of memory blocks having an increasing rate of the first error bits greater than a reference increasing rate of error bits;
detecting second error bits within second non-selection data stored in the weak block when a second read count of the weak block corresponds to a fixed number, wherein the second read count of the weak block is increased by a second read request;
detecting whether a number of the second error bits is greater than or equal to a read reclaim reference value;
designating the weak block as a read reclaim block when the number of the second error bits is greater than or equal to the read reclaim reference value; and
performing a read reclaim operation on the read reclaim block to copy data stored in the read reclaim block into a different memory block of the plurality of memory blocks, wherein:
a memory controller of the storage device is configured to:
perform a first read operation on the first non-selection data stored in a first page that is unselected by the first read request; and
perform a second read operation on the second non-selection data stored in a second page that is unselected by the second read request.

2. The method of claim 1 , wherein the fixed number associated with the weak block is shorter than the random number.

3. The method of claim 1 , wherein the reference increasing rate of error bits is an average of increasing rates of error bits of the plurality of memory blocks.

4. The method of claim 1 , further comprising:
comparing the number of the second error bits with a first threshold value of error bits, wherein
when the number of the second error bits is smaller than or equal to the first threshold value of error bits, the number of the second error bits is detected when the second read count corresponds to the random number.

5. The method of claim 4 , wherein when the number of the second error bits is greater than the first threshold value of error bits, the number of the second error bits is detected when the second read count corresponds to the fixed number.

6. The method of claim 1 , further comprising designating the weak block as a read reclaim block when the number of the second error bits is greater than or equal to the read reclaim reference value.

7. The method of claim 1 , wherein:
each of the plurality of memory blocks comprises a plurality of memory cells, each comprising a charge trap layer,
the memory cells constitute a three-dimensional memory array, and
the first non-selection data is data stored in memory cells selected by a word line that is adjacent to a third page corresponding to the first read request of a host or to a ground selection line or a string selection line.

8. A read reclaim method of a storage device, the method comprising:
detecting, by performing a first read operation, a first number of first error bits of first data stored in each of a plurality of memory blocks;
detecting, by performing a second read operation after the first read operation, a second number of second error bits of second data stored in each of the plurality of memory blocks;
calculating, by using the first number and the second number, an error bit increasing rate of each of the plurality of memory blocks;
classifying each of the plurality of memory blocks into one of a first group and a second group based on the error bit increasing rate;
designating a first memory block of the plurality of memory blocks as a read reclaim block based upon a first read reclaim reference value, wherein the first memory block of the plurality of memory blocks is classified into the first group;
designating a second memory block of the plurality of memory blocks as the read reclaim block based upon a second read reclaim reference value that differs from the first read reclaim reference value, wherein the second memory block of the plurality of memory blocks is classified into the second group; and
performing a read reclaim operation on the read reclaim block to copy data stored in the read reclaim block into a different memory block of the plurality of memory blocks.

9. The method of claim 8 , wherein:
the first memory block is designated the read reclaim block when a first detected number of error bits existing in the first memory block exceeds the first read reclaim reference value, and
the second memory block is designated the read reclaim block when a second detected number of error bits existing in the second memory block exceeds the second read reclaim reference value.

10. The method of claim 9 , wherein:
the first read reclaim reference value is smaller than the second read reclaim reference value, and
a first error bit increasing rate of the first memory block based on the calculating the error bit increasing rate is greater than a second error bit increasing rate of the second memory block based on the calculating the error bit increasing rate.

11. The method of claim 8 , wherein:
the first memory block is designated the read reclaim block when, after the second read operation, a first number of read operations of the first memory block exceeds the first read reclaim reference value, and
the second memory block is designated the read reclaim block when, after the second read operation, a second number of read operations of the second memory block exceeds the second read reclaim reference value.

12. The method of claim 11 , wherein:
the first read reclaim reference value is smaller than the second read reclaim reference value, and
the first number of read operations is smaller than the second number of read operations.

13. A storage device comprising:
a nonvolatile memory device comprising a plurality of memory blocks; and
a memory controller configured to:
detect an increasing rate of a number of error bits of data stored in a memory block of the plurality of memory blocks with respect to a random number of read operations requested for the memory block,
designate the memory block as a weak block in response to determining that the increasing rate of the number of error bits of data stored in the memory block exceeds a reference increasing rate of error bits, and
perform a read reclaim operation on the memory block designated as a read reclaim block in response to detecting that, after a fixed number of read operations is performed on the memory block, the memory block designated as the weak block stores a number of error bits exceeding a read reclaim reference value of error bits, for copying data stored in the memory block designated as the read reclaim block into a different memory block of the plurality of memory blocks.

14. The storage device of claim 13 , wherein the memory controller comprises a per-block error bit table that stores a count of read operations of each of the plurality of memory blocks and the number of error bits stored by each of the plurality of memory blocks.

15. The storage device of claim 14 , wherein the memory controller programs the count of the read operations and the number of error bits for each of the memory blocks in the nonvolatile memory device.

16. The storage device of claim 13 , wherein:
the memor

Assignees

• Jei Hyun Seung
• Lee Heewon
• Kim Suejin
• Samsung Electronics Co Ltd

Inventors

• Jei Hyun-Seung
• Lee Heewon
• Kim Suejin

Classifications

• G06F11/102

  Error in check bits · CPC title

• G11C29/52

  Protection of memory contents; Detection of errors in memory contents · CPC title

• G06F11/0751

  Error or fault detection not based on redundancy (power supply failures G06F1/30; network fault management H04L41/06) · CPC title

• G11C2029/0411

  Online error correction · CPC title

• G11C2029/0409

  Online test · CPC title