MEMORY ERRORS AND REDUNDANCY

• US 20110041016A1
• Filed: 08/03/2010
• Published: 02/17/2011
• Est. Priority Date: 08/12/2009
• Status: Abandoned Application

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: O'CONNELL, Cormac Michael
• Application Number:
  US12/849,157
• Publication Number:
  US 20110041016A1
• Time in Patent Office: Days
• US Class Current: 714/711
• CPC Class Codes: G06F 11/1048 using arrangements adapted for a specific error detection or correction feature
• CPC Class Codes: G11C 2029/0401 in embedded memories
• CPC Class Codes: G11C 2029/0409 Online test
• CPC Class Codes: G11C 2029/0411 Online error correction
• CPC Class Codes: G11C 2029/1208 Error catch memory
• CPC Class Codes: G11C 29/42 using error correcting codes [ECC] or parity check
• CPC Class Codes: G11C 29/44 Indication or identification of errors, e.g. for repair
• CPC Class Codes: G11C 29/4401 for self repair
• CPC Class Codes: G11C 29/76 using address translation or modifications

Abstract

Redundancy including extra rows and/or columns of memory cells is added to the memory, and ECC parity is used to detect errors. When an error occurs at a location the first time, it is assumed to be a soft error, the data is corrected in this location, and the address of the erroneous cell (e.g., the failed address) is stored in a list. When another error occurs, it is determined whether its failed address is on the stored list. If it is not, then the error is again assumed to be a soft error, the data at this location is corrected, and the failed address is added to the stored address list, etc. If, however, the failed address is already in the stored failed address list, the error is considered either a latent error or VTR, and is repaired on the fly using on-chip redundancy.

Claims

1. A method comprising:

capturing an address of a failed location in a memory;

based on the address, determining an error type;

if the error type does not include a soft error, using redundancy to repair the error.

2. The method of claim 1 wherein determining the error type comprises comparing the address of the failed location to a list of addresses.

3. The method of claim 1, further comprising overwriting the failed location before a next access to the failed location, if the error type includes the soft error.

4. The method of claim 3 wherein overwriting the failed location is done by an application using the memory or by a system using the memory arranging the overwriting.

5. The method of claim 1 further comprising overwriting the failed location with correct data, if the error type includes the soft error.

6. The method of claim 1 further comprising storing the address to a list if the error type includes the soft error.

7. The method of claim 1 wherein using redundancy comprises one or a combination of providing at least one redundant row of memory cells in a memory bank, providing at least one redundant row of memory cells in a redundant bank, and providing at least one redundant column of memory cells and associated column circuitry.

8. The method of claim 1 wherein using redundancy comprises replacing a row containing the failed location for a redundant row.

9. The method of claim 8 wherein the row containing the failed location and the redundant row are in a same bank.

10. The method of claim 1 wherein using redundancy comprises replacing a word containing the failed location for a redundant word.

11. The method of claim 10 wherein the word containing the failed location is in a same bank with the redundant word.

12. The method of claim 10 wherein the word containing the failed location is in a bank different from a bank containing the redundant word.

13. The method of claim 1 wherein using redundancy comprises replacing a column of memory cells and associated circuitry containing the failed location for a redundant column of memory cells and associated circuitry.

14. The method of claim 1 wherein using redundancy to repair the error is performed on the fly.

15. A method comprising:

detecting an error at a memory location;

identifying the error as a soft error, and adding an address of the memory location to a list if the error occurs at the memory location the first time; and

;

using a redundant location to replace the memory location if the error occurs at the memory location at least twice.

16. The method of claim 15 further comprising providing at least one redundant row in a same memory bank with the memory location.

17. The method of claim 16 wherein using a redundant location to replace the memory location comprises:

corresponding a row containing the memory location with a redundant row containing the redundant location;

copying data from the row containing the memory location to the redundant row;

writing correct data to the redundant location; and

redirecting access to the redundant location when accessing the memory location.

18. The method of claim 16 wherein using a redundant location to replace the memory location comprises:

corresponding a word containing the memory location with a redundant word containing the redundant location;

copying data from the word containing the memory location to the redundant word;

writing correct data to the redundant location; and

redirecting access to the redundant location when accessing the memory location.

19. The method of claim 15 further comprising:

providing at least one redundant row in a redundant bank separate from a memory bank of the memory location; and

using a redundant location to replace the memory location comprising;

corresponding a word containing the memory location with a redundant word containing the redundant location;

copying data from the word containing the memory location to the redundant word;

writing correct data to the redundant location; and

redirecting access to the redundant location when accessing the memory location.

20. The method of claim 15 further comprising:

providing at least one redundant column; and

using a redundant location to replace the memory location comprising;

corresponding a column containing the memory location with a redundant column containing the redundant location;

copying data from the column containing the memory location to the redundant column;

writing correct data to the redundant location; and

redirecting access to the redundant location when accessing the memory location.

21. The method of claim 20 wherein writing correct data to the redundant location comprises identifying data in the redundant location as corresponding to a soft error.

22. The method of claim 15 wherein determining if the error occurs at the memory location at least twice is based on the address of the memory location and the list.

23. The method of claim 15, further comprising executing a method selected from a group consisting of 1) having an application using the memory overwrite the memory location before a read access 2) having a processing unit using the memory arrange overwriting the memory location before a read access, and 3) overwriting the memory location, if the error is identified as the soft error.

24. The method of claim 15 wherein using redundancy to replace the memory location is done on the fly.

25. A method comprising:

capturing an address of a failed location in memory;

performing a soft error correction if the address is not in a list of soft error addresses; and

performing a hard error correction if the address is in a list of soft error addresses;

wherein the soft error correction comprises;

adding the address to the list;

repairing the failed location by a method selected from a group consisting of

using an application that uses the memory to overwrite the failed location before an access to the failed location;

using a processing unit that uses the memory to arrange an overwrite to the failed location before the access to the failed location; and

overwriting the failed location; and

the hard error correction comprises;

repairing the failed location by a method selected from a group consisting of

using a redundant row to replace a row containing the failed location;

using a redundant word to replace a word containing the failed location; and

using a redundant column to replace a column containing the failed location.

26. The method of claim 25 wherein the redundant row is in a same bank with the row containing the failed location when using a redundant row to replace a row containing the failed location.

27. The method of claim 25 wherein the redundant row is in a same memory bank with the row containing the failed location when using a redundant word to replace a word containing the failed location.

28. The method of claim 25 wherein the redundant row is in a bank separate from a bank containing the failed location when using a redundant word to replace a word containing the failed location.