NON-VOLATILE SEMICONDUCTOR STORAGE DEVICE

• US 20130148435A1
• Filed: 06/25/2012
• Published: 06/13/2013
• Est. Priority Date: 12/09/2011
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: MATSUNAGA, Naoki
• Granted Patent: US 8,804,435 B2
• Time in Patent Office: Days
• US Class Current: 365/185.23
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0655 Vertical data movement, i.e. input-output transfer; data movement between one or more hosts and one or more storage devices
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/04 using variable threshold transistors, e.g. FAMOS
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/06 Auxiliary circuits, e.g. for writing into memory
• CPC Class Codes: G11C 16/26 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/3404 Convergence or correction of memory cell threshold voltages; Repair or recovery of overerased or overprogrammed cells
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically
• CPC Class Codes: G11C 29/52 Protection of memory contents; Detection of errors in memory contents

Abstract

According to one embodiment, there is provided a non-volatile semiconductor storage device including a non-volatile memory, a monitoring section, a determining section, and a notification processing section. The non-volatile memory includes a plurality of memory cells driven by word lines and a voltage generating section that generates a read voltage to be applied to the word lines. The monitoring section monitors a change in a threshold distribution of the plurality of memory cells upon performing a read processing to read data from the plurality of memory cells by applying the read voltage to the word lines. The determining section determines a degree of deterioration of the non-volatile memory in accordance with a monitoring result by the monitoring section. The notification processing section notifies a life of the non-volatile memory in accordance with a determining result by the determining section.

Claims

1. A non-volatile semiconductor storage device comprising:

a non-volatile memory including a plurality of memory cells driven by word lines and a voltage generating section that generates a read voltage to be applied to the word lines;

a monitoring section that monitors a change in a threshold distribution of the plurality of memory cells upon performing a read processing to read data from the plurality of memory cells by applying the read voltage to the word lines;

a determining section that determines a degree of deterioration of the non-volatile memory in accordance with a monitoring result by the monitoring section; and

a notification processing section that notifies a life of the non-volatile memory in accordance with a determining result by the determining section.

2. The non-volatile semiconductor storage device according to claim 1, wherein

in a fourth mode, the monitoring section monitors a number of reading until the read processing fails in repeatedly performing the read processing by gradually changing the read voltage respectively in a rising direction and a lowering direction.

3. The non-volatile semiconductor storage device according to claim 2, wherein

the determining section compares the monitored number of reading with a predetermined threshold, and determines the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.

4. The non-volatile semiconductor storage device according to claim 3, wherein

the determining section compares the monitored number of reading with a reading number threshold, and determines the degree of deterioration of the non-volatile memory in accordance with the comparison result thereof.

5. The non-volatile semiconductor storage device according to claim 4, wherein

the determining section identifies a distribution of the monitored number of reading, compares a frequency of the monitored number of reading with a frequency threshold, and determines the degree of deterioration of the non-volatile memory in accordance with the comparison result thereof.

6. The non-volatile semiconductor storage device according to claim 1, wherein

in a fourth mode, the monitoring section monitors the read voltage when the read processing fails while gradually changing the read voltage respectively in a rising direction and a lowering direction.

7. The non-volatile semiconductor storage device according to claim 6, wherein

the determining section compares an amount of change of the monitored read voltage from a default value with a predetermined threshold, and determines the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.

8. The non-volatile semiconductor storage device according to claim 7, wherein

the determining section compares the amount of change of the monitored read voltage from the default value with a change amount threshold, and determines the degree of deterioration of the non-volatile memory in accordance with the comparison result thereof.

9. The non-volatile semiconductor storage device according to claim 8, wherein

the determining section identifies a distribution of the amount of change, compares a frequency of the amount of change that is at or more than the change amount threshold with a frequency threshold, and determines the degree of deterioration of the non-volatile memory in accordance with the comparison result thereof.

10. The non-volatile semiconductor storage device according to claim 1, wherein

in a first mode, the monitoring section monitors a number of reading until the read processing succeeds while repeatedly performing the read processing under a state in which the read voltage is kept constant.

11. The non-volatile semiconductor storage device according to claim 10, wherein

the determining section compares the monitored number of reading with a predetermined threshold, and determines the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.

12. The non-volatile semiconductor storage device according to claim 11, wherein

the determining section compares the monitored number of reading with a reading number threshold, and determines the degree of deterioration of the non-volatile memory in accordance with the comparison result thereof.

13. The non-volatile semiconductor storage device according to claim 12, wherein

the determining section identifies a distribution of the monitored number of reading, compares a frequency of the monitored number of reading that is at or more than the reading number threshold with a frequency threshold, and determines the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.

14. The non-volatile semiconductor storage device according to claim 1, wherein

in a second mode, the monitoring section monitors a number of reading until the read processing succeeds in repeatedly performing the read processing by gradually changing the read voltage in one of a rising direction and a lowering direction.

15. The non-volatile semiconductor storage device according to claim 14, wherein

the determining section compares the monitored number of reading with a predetermined threshold, and determines the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.

16. The non-volatile semiconductor storage device according to claim 15, wherein

the determining section compares the monitored number of reading with a reading number threshold, and determines the degree of deterioration of the non-volatile memory in accordance with the comparison result thereof.

17. The non-volatile semiconductor storage device according to claim 16, wherein

the determining section identifies a distribution of the monitored number of reading, compares a frequency of the monitored number of reading that is at or more than the reading number threshold with a frequency threshold, and determines the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.

18. The non-volatile semiconductor storage device according to claim 1, wherein

in a second mode, the monitoring section monitors the read voltage when the read processing succeeds while gradually changing the read voltage in one of a rising direction and a lowering direction.

19. The non-volatile semiconductor storage device according to claim 12, wherein

the determining section compares the monitored number of reading with a predetermined threshold, and determines the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.

20. The non-volatile semiconductor storage device according to claim 1, wherein

in a third mode, the monitoring section monitors a number of bit errors in data in the plurality of memory cells in performing the read processing.