EMERGING BAD BLOCK DETECTION

• US 20080307270A1
• Filed: 06/07/2007
• Published: 12/11/2008
• Est. Priority Date: 06/07/2007
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Li, Tieniu
• Granted Patent: US 7,765,426 B2
• Time in Patent Office: Days
• US Class Current: 714/47
• CPC Class Codes: G06F 11/073 in a memory management context, e.g. virtual memory or cache management memory management G06F12/00; testing of static memory units G11C29/00
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 11/2017 where memory access, memory control or I/O control functionality is redundant redundant communication control functionality G06F11/2005; redundant storage control functionality G06F11/2089
• CPC Class Codes: G06F 2201/85 Active fault masking without idle spares
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles

Abstract

Apparatus and methods, such as those that read data from non-volatile integrated circuit memory devices, such as NAND flash. For example, disclosed techniques can be embodied in a device driver of an operating system. Errors are tracked during read operations. If sufficient errors are observed during read operations, the block is then retired when it is requested to be erased or a page of the block is to be written. One embodiment is a technique to recover data from uncorrectable errors. For example, a read mode can be changed to a more reliable read mode to attempt to recover data. One embodiment further returns data from the memory device regardless of whether the data was correctable by decoding of error correction code data or not.

Claims

1. A method of monitoring a block of a non-volatile integrated circuit memory device, the method comprising:

decoding error correction codes to determine whether or not a page of data of the block of the memory device was read with at least one error; and

maintaining a history of errors for the block of the memory device corresponding to the page that was read at least when the page was read with at least one error, wherein the history of errors is used to indicate whether or not to retire the block early.

2. The method of claim 1, wherein maintaining the history further comprises:

maintaining a count, wherein the count is incremented at least partially in response to determining that the at least one error corresponds to one error;

wherein early retirement for the block is indicated in response to the count reaching a threshold value.

3. The method of claim 2, further comprising resetting the count upon power up of a device using the memory device.

4. The method of claim 1, wherein maintaining the history further comprises updating the history to indicate early retirement for the block when multiple errors are encountered when reading the page of the block, wherein a count of the number of errors is determined by comparing uncorrected data and corrected data.

5. The method of claim 1, wherein maintaining the history comprises setting a count for the history to at least a threshold value, wherein the block is indicated for early retirement if the count reaches at least the threshold value.

6. The method of claim 1, wherein the at least one error comprises multiple errors that are uncorrectable, further comprising initiating a data recovery process to attempt to recover the data.

7. The method of claim 1, wherein the at least one error comprises multiple errors that are uncorrectable by decoding of error correction codes (ECC), and wherein the page was read using a first read mode, further comprising changing to a different read mode and re-reading the page.

8. The method of claim 1, wherein the at least one error comprises uncorrectable errors further comprising returning a status to an operating system of a successful read operation even when an uncorrectable error is read.

9. The method of claim 1, further comprising maintaining the history of errors for the block of the memory device on a different device than the memory device itself.

10. The method of claim 1, wherein the memory device comprises a NAND flash memory device.

11. The method of claim 1, wherein the method is performed by an operating system.

12. A method of managing blocks for a non-volatile integrated circuit memory device, the method comprising:

receiving a command to erase a block of memory or write to a page of the block of memory; and

disabling an erase or write based at least in part on a history of errors associated with read operations for one or more pages of the block.

13. The method of claim 12, further comprising reclaiming previously written pages of the block, and then disabling use of the block.

14. The method of claim 12, wherein disabling comprises adding the block to a bad block table in the memory device to mark the block as bad.

15. The method of claim 12, further comprising inspecting a count of errors encountered during read operations for one or more pages of the block.

16. A method of accessing a page of data from a non-volatile integrated circuit memory device, the method comprising:

requesting a read of the page of data from the memory device;

inspecting error correction codes (ECC) associated with the page; and

providing a status to an operating system that indicates that the page of data was read correctly regardless of whether or not the page of data included any uncorrectable errors.

17. The method of claim 16, wherein at least a first read mode of operation and a second read mode of operation slower than the first read mode of operation are selectable for reading data from the device, wherein requesting the read of the page further comprises:

determining that a decoding of an initial read has resulted in an uncorrectable error, wherein the initial read was performed using the first read mode of operation;

changing from the first read mode of operation to the second read mode of operation; and

requesting another read of the page.

18. The method of claim 17, wherein the first read mode of operation comprises direct memory access (DMA) and wherein the second read mode of operation comprises using the microprocessor to control access.

19. The method of claim 17, further comprising determining whether to request another read of the page based at least partly on a loop counter.

20. The method of claim 17, further comprising determining whether to request another read of the page based at least partly on a timer.

21. The method of claim 16, further comprising performing the method by a driver of an operating system.

22. A method of maintaining one or more indications for indicating that a block of a non-volatile integrated circuit memory device, the method comprising:

preventing further erasing or reprogramming of the block at least partially in response to at least one of;

determining that an error detected as part of at least one read operation performed with respect to at least one page of the block of memory is not correctable via decoding of an error correction code;

or

determining that a history of errors collected for the blocks of the memory device indicates that at least one error has occurred during a prior read operation for the block.

23. An apparatus for monitoring a block of a non-volatile integrated circuit memory device, the apparatus comprising:

a module configured to decode error correction codes to determine whether or not a page of data of the block of the memory device was read with at least one error; and

a module configured to maintain a history of errors for the block of the memory device corresponding to the page that was read at least when the page was read with at least one error, wherein the history of errors is used to indicate whether or not to retire the block early.