Memory, memory controller, memory system, method of memory, memory controller and memory system

Patent metadata

Field	Value
Publication number	US-9613687-B2
Application number	US-201414147063-A
Country	US
Kind code	B2
Filing date	Jan 3, 2014
Priority date	Feb 6, 2013
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

In one embodiment, the method includes performing a read operation on a memory, and determining, by a memory controller, whether to perform a reliability verification read operation based on a count value and a reference value. The count value is based on a number of read commands issued by the memory controller to the memory, and the reliability verification read operation is for reading data from at least one memory cell associated with at least one unselected word line in the memory. An unselected word line is a word line not selected during the read operation. The method further includes performing the reliability verification read operation for the at least one unselected word line based on the determining.

First claim

What is claimed is:

1. A method of operating a memory controller, comprising:
performing a read operation on a memory;
comparing, by the memory controller, a count value with a reference value, the count value being based on a number of read commands issued by the memory controller to the memory;
performing a reliability verification read operation for at least one unselected word line of the memory to verify reliability of the memory when the count value reaches the reference value, the unselected word line being a word line not selected during the read operation; and
performing a read reclaim according to a result of the reliability verification read operation.

2. The method of claim 1 , further comprising:
generating a random number as the reference value.

3. The method of claim 2 , wherein the generating generates the random number such that an average of random numbers generated over time approaches a desired value.

4. The method of claim 2 , wherein the reliability verification read operation is performed if the count value is greater than or equal to the random number.

5. The method of claim 4 , further comprising:
resetting the count value if the reliability verification read operation is performed.

6. The method of claim 2 , further comprising:
maintaining count values and random numbers for each of a plurality of blocks in the memory; and wherein
the comparing uses the count value and the random number associated with the block to which the read operation is directed.

7. The method of claim 1 , wherein the performing the reliability verification read operation performs the reliability verification read operation for the at least one unselected word line adjacent to a selected word line selected during the read operation.

8. The method of claim 1 , wherein the unselected word line is an open word line, and each of the at least one memory cell connected to the open word line is in an erased state.

9. The method of claim 1 , wherein the performing the reliability verification read operation,
performs the reliability verification read operation for the at least one unselected word line adjacent to a selected word line selected during the read operation, and
perform the reliability verification read operation for at least one open word line if any open word lines exist, and the at least one memory cell connected to the open word line is in an erased state.

10. The method of claim 1 , wherein the performing the read reclaim comprises:
determining if the data read during the reliability verification read operation meets a condition; and
performing the read reclaim if the condition is met.

11. The method of claim 10 , wherein the condition is if a bit error rate of the data read during the reliability verification read operation is greater than a threshold.

12. The method of claim 1 , wherein the read reclaim copies data of a block including the selected word line to a new block and closes the block including a selected word line selected during the read operation.

13. The method of claim 1 , further comprises:
performing a control operation if the result of the reliability verification read operation meets a condition,
wherein the condition is if a number of off memory cells read during the reliability verification read operation is greater than a threshold.

14. The method of claim 13 , wherein the control operation closes the block including a selected word line selected during the read operation.

15. The method of claim 1 ,
wherein the read reclaim is performed when the result of the reliability verification read operation indicates a low reliability.

16. A memory controller, comprising:
a counter configured to generate a count value based on a number of read commands issued by the memory controller to a memory;
a read controller configured to,
perform a read operation, and
perform a reliability verification read operation for at least one memory cells associated with at least one unselected word line in the memory to verify reliability of the memory when the count value reaches the reference value, wherein

the memory controller is configured to perform a read reclaim according to a result of the reliability verification read operation.

17. The memory controller of claim 16 , further comprising:
a first register configured to store a desired value.

18. The memory controller of claim 17 , further comprising:
a random number generator configured to generate a random number based on the desired value; and wherein
the read controller is configured to determine whether to perform the reliability verification read operation using the random number as the reference value.

19. The memory controller of claim 17 , further comprising:
a second register storing information about program/erase cycles of the memory; and wherein
the memory controller is configured to change the desired value based on the information.

20. The memory controller of claim 16 , wherein the counter is configured to rest the count value if the read controller determines to perform the reliability verification read operation.

21. The memory controller of claim 16 , wherein
the counter is configured to maintain a respective count value for each of a plurality of blocks in the memory;
a random number generator is configured to maintain a respective random number for each of the plurality of blocks;
the read controller is configured to determine whether to perform the reliability verification read operation based on the respective count value and the respective random number associated with the block to which the read operation is directed, the respective random number serving as the reference value.

22. The memory controller of claim 16 , wherein the read controller is configured to perform the reliability verification read operation for the at least one unselected word line adjacent to a selected word line selected during the read operation.

23. The memory controller of claim 16 , wherein the unselected word line is an open word line, and each of the at least one memory cell connected to the open word line are in an erased state.

24. The memory controller of claim 16 , wherein the read controller is configured to,
perform the reliability verification read operation for the at least one unselected word line adjacent to a selected word line selected during the read operation, and
perform the reliability verification read operation for at least one open word line if any open word lines exist, and the at least one memory cell connected to the open word line is in an erased state.

25. The memory controller of claim 16 , wherein the read controller is configured to,
determine if the data read during the reliability verification read operation meets a condition, and
perform the read reclaim if the condition is met.

26. The memory controller of claim 25 , wherein the condition is if a bit error rate of the data read during the read verification operation is greater than a threshold.

27. The memory controller of claim 16 , wherein the read reclaim copies data of a block including a selected word line selected during the read operation to a new block and closes the block including the selected word line.

28. The memory controller of claim 16 , wherein
the read controller is configured to perform a control operation if the result of the reliabili

Assignees

• Samsung Electronics Co Ltd

Inventors

• Kim Kyungryun
• Yoon Sangyong

Classifications

• G11C16/349

  Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles · CPC title

• G11C16/0483

  comprising cells having several storage transistors connected in series · CPC title

• G11C11/5642 Primary

  Sensing or reading circuits; Data output circuits · CPC title

• H03M13/373

  with erasure correction and erasure determination, e.g. for packet loss recovery or setting of erasures for the decoding of Reed-Solomon codes · CPC title

• G11C29/028

  with adaption or trimming of parameters · CPC title