Repairing soft failures in memory cells in SRAM arrays
AssigneeTexas Instruments Incorporated
InventorsWah Kit Loh, Beena Pious
Life of this patent
Estimating the term…
Abstract
An embodiment of the invention provides a method of repairing soft failures in memory cells of an SRAM array. The SRAM array is tested to determine the location and type of soft failures in the memory cells. An assist circuit is activated that changes a voltage in a group of memory cells with the same type of soft failure. The change in voltage created by the assist circuit repairs the soft failures in the group. The group may be a word line or a bit line. The type of soft failures includes a failure during a read of a memory cell and a failure during the write of a memory cell.
Claims20
A method of repairing soft failures in memory cells of an SRAM array comprising:
- testing the SRAM array to determine locations where the memory cells have soft failures;
- testing the SRAM array to determine types of soft failures in the memory cells with soft failures;
- activating at least one assist circuit;
- wherein the at least one assist circuit changes a voltage in the memory cells with soft failures that have one and only one type of soft failure;
- wherein the changed voltage is used during normal operation of the SRAM array;
- wherein the memory cells with soft failures that have one and only one type of soft failure are contained in a group.
A method of repairing bit failures in memory cells of an SRAM array comprising:
- testing the SRAM array to determine locations of the memory cells with hard bit failures;
- replacing the memory cells with hard bit failures with redundant memory cells;
- testing the SRAM array to determine locations of the memory cells with soft failures;
- testing the SRAM array to determine types of soft failure in the memory cells with soft failures;
- activating an assist circuit;
- wherein the assist circuit changes a voltage in the memory cells with soft failures that have one and only one type of soft failure;
- wherein the changed voltage is used during normal operation of the SRAM array;
- wherein the memory cells with soft failures that have one and only one type of soft failure are contained in a group.
Dependencies are inferred from the claim text.