Built-in-redundancy analysis using RAM
View Patent ↗A method for testing memory in an integrated circuit device is disclosed. The method includes executing a test routine in a portion of the memory at a speed sufficient to fully test the memory cells, identifying faulty memory cells in the tested portion of the memory; writing an error map in another portion of the memory, the error map indicating the location of faulty memory cells found in the tested portion and, after executing the test routine and writing the error map, repairing at least some of the faulty memory cells using the error map. Once one portion of memory is tested, another portion is tested and a prior tested portion is used to write a new error map. Repairing, by analyzing the error map, is done at a slower speed than required for memory testing, allowing the use of a smaller logic section in the integrated circuit.
1. A method for testing memory in an integrated circuit device, comprising:
executing a test routine in a first portion of said memory, said test routine identifying faulty memory cells in said first portion of said memory;
writing an error map in a second portion of said memory, said error map indicating the location of said faulty memory cells; and
after said executing a test routine and said writing an error map, repairing at least some of said faulty memory cells using said error map when said error map indicates the presence of said faulty memory cells.
2. The method for testing memory described in claim 1 , wherein said repairing said faulty memory cells comprises:
analyzing said first portion of said memory by reference to said error map;
determining a repair plan from said analyzing if said analyzing indicates that said first portion of said memory includes faulty memory cells; and
performing a repair of said first portion of said memory according to said plan.
3. The method for testing memory described in claim 1 , further comprising:
executing said test routine in said second portion of said memory;
writing an error map in said first portion of said memory, said error map indicating the location of said faulty memory cells;
analyzing said memory by reference to said map;
determining a repair plan from said analyzing if said analyzing indicates an error in said second portion of said memory; and
performing a repair of said second portion of said memory according to said plan.
4. The method for testing memory described in claim 1 , wherein said executing a test routine is performed at a speed consistent with the normal operation of said memory.
5. The method for testing memory described in claim 4 , wherein said executing a test routine is performed by dedicated logic resident in said integrated circuit device.
6. The method for testing memory described in claim 4 , wherein said analyzing said memory is performed by dedicated analysis logic resident in said integrated circuit device.
7. The method for testing memory described in claim 6 , wherein said analyzing said memory is performed at a speed that is less than said speed consistent with the normal operating speed of said memory.
8. The method for testing memory described in claim 1 , wherein said second portion of said memory is logically identical to said first portion of said memory.
9. The method for testing memory described in claim 1 , wherein said performing a repair of said memory is accomplished by substituting a redundant memory column in said memory for a column in said memory containing a faulty memory cell.
10. The method for testing memory described in claim 1 , wherein said performing a repair of said memory is performed by substituting a redundant memory row in said memory for a row in said memory containing a faulty memory cell.
11. The method for testing memory described in claim 1 , wherein said performing a repair of said memory is accomplished by substituting a redundant memory column and a redundant memory row in said memory for a column and a row containing a faulty memory cell.
12. A circuit in an integrated circuit device for testing an array of memory cells comprising a first bank of memory cells and a second bank of memory cells in said integrated circuit device, comprising:
a circuit electronically coupled to said array of memory cells and comprising logic for performing said testing of one of said first bank and said second bank of memory cells at a speed sufficient to fully stress the memory cells in said array and writing an error map to the other of said first bank and said second bank; and
a circuit electronically coupled to said array of memory cells and comprising logic for repairing said array of memory cells.
13. The circuit described in claim 12 wherein said repairing said array of memory cells is operable to be performed after the completion of said testing said array of memory cells.
14. The circuit described in claim 12 wherein said logic for testing said array of memory cells comprises logic for writing an error map of the results of said testing into an array of memory cells not under test.
15. The circuit described in claim 12 wherein said logic for repairing said array of memory cells comprises logic for analyzing said map of said results of said testing.
16. The circuit described in claim 15 wherein said logic for repairing said array of memory cells is enabled to repair said array according to the results of analyzing said map of said results found.
17. The circuit described in claim 16 wherein said analyzing said map is accomplished independently of said testing of said array of memory cells.
18. The circuit described in claim 12 wherein said repairing said array of memory cells comprises changing addressing in said integrated circuit device to logically incorporate a redundant memory cell into said array of memory cells in place of a faulty memory cell.
19. An integrated circuit device, comprising:
a first set of memory cells, said first set of memory cells being enabled to be logically addressed in said integrated circuit device and including a first bank of memory cells and a second bank of memory cells;
a second set of memory cells, said second set of memory cells being enabled to be logically addressed in said integrated circuit device;
a circuit comprising logic for performing a test of one of said first bank and said second bank of memory cells and writing an error map to the other of said first bank and said second bank of said first set of memory cells; and
a circuit comprising logic for performing a repair analysis of the results of said test, wherein memory cells in said second set of memory cells are enabled to be logically incorporated into the addressing of said first set of memory cells so as to logically replace one or more memory cells in said first set of memory cells.
20. The integrated circuit device described in claim 19 , wherein said circuit comprising logic for performing a test comprises a built-in-self-test controller.
21. The integrated circuit device described in claim 20 , wherein said circuit comprising logic for performing a repair analysis of the results of said test is enabled to perform said analysis on an error map of said results written in a third set of memory cells.
22. The integrated circuit device described in claim 19 , wherein said first set of memory cells is logically arrayed in rows and columns.
23. The integrated circuit device described in claim 19 , wherein said second set of memory cells comprises a logical row of memory cells.
24. The integrated circuit device described in claim 19 , wherein said second set of memory cells comprises a logical column of memory cells.