Stuck-at defect condition repair for a non-volatile memory cell
A method and apparatus for repairing a stuck-at defect condition in a non-volatile memory cell, such as a spin-torque transfer random access memory (STRAM). In some embodiments, a resistive sense element has a magnetic tunneling junction (MTJ) and a repair plane located adjacent to the resistive sense element. The repair plane injects a magnetic field in the MTJ to repair a stuck-at defect condition.
1. A magnetic stack comprising:
a resistive sense element having a magnetic tunneling junction (MTJ); and
a repair plane spanning multiple resistive sense elements and separated from at least one MTJ by a predetermined distance that corresponds to a magnetic field generated by a current pulse conducted through the repair plane, the magnetic field influencing a magnetic free layer of the MTJ to repair a stuck-at defect condition in the MTJ.
2. The magnetic stack of claim 1 , wherein the current pulse is an AC degaussing pulse that varies a polarization of the magnetic field.
3. The magnetic stack of claim 1 , wherein the current pulse has a steady state positive amplitude that lasts a predetermined amount of time.
4. The magnetic stack of claim 1 , wherein the current pulse alternates between positive and negative amplitudes to disturb the magnetization of a magnetic free layer of the MTJ.
5. The magnetic stack of claim 1 , wherein the resistive sense elements are connected to row and column decoders while the repair plane is connected to an enhancement layer.
6. The magnetic stack of claim 1 , wherein the repair plane is partially surrounded by a soft magnetic material.
7. The magnetic stack of claim 1 , wherein the repair plane repairs the MTJ after a failed write verify operation.
8. The magnetic stack of claim 1 , wherein the repair plane repairs the MTJ after successively increasing a write current passed through the resistive sense element to a predetermined threshold.
9. The magnetic stack of claim 1 , wherein resistive sense element is spin-torque transfer random access memory (STRAM).
10. A method comprising:
providing a resistive sense element having a magnetic tunneling junction (MTJ); and
repairing a stuck-at defect condition in the MTJ with a magnetic field generated by passing a current pulse through a repair plane that spans multiple resistive sense elements, the repair plane separated from the MTJ by a predetermined distance that corresponds to the magnetic field influencing a magnetic free layer of the MTJ.
11. The method of claim 10 , wherein the current pulse is an AC degaussing pulse that varies a polarization of the magnetic field.
12. The method of claim 10 , wherein the current pulse has a steady state positive amplitude that lasts a predetermined amount of time.
13. The method of claim 10 , wherein the current pulse alternates between positive and negative amplitudes to disturb a magnetization of a magnetic free layer of the MTJ.
14. The method of claim 10 , wherein the repair plane is aligned with a long axis of the resistive sense element.
15. The method of claim 10 , wherein the repair plane is aligned with a short axis of the resistive sense element.
16. The method of claim 10 , wherein the repair plane is partially surrounded by a soft magnetic material.
17. A magnetic stack comprising:
a plurality of resistive sense elements each having a magnetic tunneling junction (MTJ);
a row and column decoder respectively connected to a plurality of control lines that allow access to one or more resistive sense elements; and
a repair plane positioned a predetermined distance from the MTJ to repair a stuck-at defect condition of the MTJ in response to a current pulse generating a magnetic field that induces a magnetic free layer of the MTJ to switch magnetization directions.
18. The magnetic stack of claim 17 , wherein the current pulse is an AC degaussing pulse that varies a polarization of the magnetic field.
19. The magnetic stack of claim 17 , wherein the current pulse alternates between positive and negative amplitudes to switch a magnetization direction.
20. The magnetic stack of claim 1 , wherein the repair plane is proximal to a magnetic free layer and distal to a magnetically fixed layer of the resistive sense element.