Current driven switched magnetic storage cells having improved read and write margins and magnetic memories using such cells

• US 7,286,395 B2
• Filed: 10/27/2005
• Issued: 10/23/2007
• Est. Priority Date: 10/27/2005
• Status: Active Grant

• Current Assignee: Samsung Semiconductor Incorporated (Samsung Group)
• Original Assignee: Grandis, Inc. (Samsung Group)
• Inventors: Chen, Eugene Youjun, Huai, Yiming
• Primary Examiner(s): Ho; Hoai V.
• Application Number:
  US11/260,778
• Publication Number:
  US 20070097730A1
• Time in Patent Office: 726 Days
• Field of Search: 365/158, 365/173, 365/210, 365/200, 365/230.03
• US Class Current: 365/158
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: G11C 11/1653 Address circuits or decoders
• CPC Class Codes: G11C 11/1659 Cell access
• CPC Class Codes: G11C 11/1673 Reading or sensing circuits or methods

Abstract

A method and system for providing a magnetic memory is described. The magnetic memory includes a plurality of magnetic storage cell and at least one bit line and a plurality of source lines corresponding to the plurality of magnetic storage cells. Each magnetic storage cell includes a magnetic element that is programmed to a high resistance state by a first write current driven through the magnetic element in a first direction and to a low resistance state by a second write current driven through the magnetic element in a second direction. The bit line(s) and the source lines are configured to drive the first write current through the magnetic element in the first direction, to drive the second write current through the magnetic element in the second direction, and to drive at least one read current through the magnetic element in a third direction that does not destabilize the low resistance state.

Claims

1. A magnetic memory comprising:

a plurality of magnetic storage cells, each of the plurality of magnetic storage cells including a magnetic element that is configured to be programmed to a high resistance state by a first write current driven through the magnetic element in a first direction and to a low resistance state by a second write current driven through the magnetic element in a second direction, the first write current and the second write current programming the magnetic element via spin transfer;

at least one bit line corresponding to the plurality of magnetic storage cells; and

a plurality of source lines corresponding to the plurality of magnetic storage cells;

wherein the at least one bit line and the plurality of source lines are configured to drive the first write current through the magnetic element in the first direction, to drive the second write current through the magnetic element in the second direction, and to drive at least one read current through the magnetic element in a third direction that does not destabilize the low resistance state;

wherein the second direction is opposite to the first direction and the second direction and the third direction are the same.

2. The magnetic memory of claim 1 further comprising:

a plurality of word lines, each of the plurality of word lines corresponding to a magnetic storage cell of the plurality of magnetic storage cells and for allowing current to flow through the magnetic storage cell.

3. The magnetic memory of claim 2 wherein each of the plurality of magnetic storage cells further includes:

at least one selection device, a portion of the plurality of word lines selectively activating the at least one selection device to allow current to flow through the magnetic element.

4. The magnetic memory of claim 3 wherein the at least one selection device is an selection transistor having a source, a drain, and a gate and wherein the portion of the plurality of word lines is a word line coupled with the gate of the selection transistor, the magnetic element being coupled with the drain and one of the plurality of source lines being coupled with the source.

5. The magnetic memory of claim 1 wherein each of the plurality of source lines corresponds to a pair of the plurality of magnetic storage cells.

6. The magnetic memory of claim 1 wherein the magnetic element includes a pinned layer having a first magnetization pinned in a pinned direction, a spacer layer, and a free layer having a second magnetization, the spacer layer residing between the pinned layer and the free layer, the free layer being configured such that the magnetic element is programmed to the high resistance state by the first write current driven through the magnetic element in the first direction and being programmed into the low resistance state by the second write current driven through the magnetic element in a second direction opposite to the first direction.

7. The magnetic element of claim 6 wherein the spacer layer is a barrier layer.

8. The magnetic element of claim 6 wherein the spacer layer is conductive.

9. The magnetic memory of claim 6 wherein the magnetic element further includes an additional spacer layer and an additional pinned layer, the free layer residing between the additional spacer layer and the spacer layer, the additional spacer layer residing between the free layer and the additional pinned layer.

10. The magnetic element of claim 9 wherein the spacer layer is a barrier layer.

11. The magnetic element of claim 10 wherein the additional spacer layer is an additional barrier layer.

12. The magnetic element of claim 10 wherein the additional spacer layer is conductive.

13. The magnetic element of claim 9 wherein the spacer layer is conductive.

14. The magnetic element of claim 13 wherein the additional spacer layer is an additional barrier layer.

15. The magnetic element of claim 13 wherein the additional spacer layer is conductive.

16. The magnetic memory of claim 1 further comprising:

at least one reference cell;

at least one additional bit line coupled with the at least one reference cell; and

at least one additional source line coupled with the at least one reference cell.

17. The magnetic memory of claim 1 further comprising:

at least one spare magnetic storage cell corresponding to the bit line, each of the at least one spare magnetic storage cell including a spare magnetic element capable of being programmed to a high resistance state by a first write current driven through the spare magnetic element in a first direction and being programmed into a low resistance state by a second write current driven through the spare magnetic element in a second direction opposite to the first direction;

at least one spare source line corresponding to the at least one spare magnetic storage cell;

wherein the at least one bit line and the at least one spare source line are configured to drive the first write current through the spare magnetic element in the first direction, to drive the second write current through the spare magnetic element in the second direction, and to drive at least one read current through the spare magnetic element in a third direction that does not destabilize the low resistance state.

18. The magnetic memory of claim 1 further comprising:

at least one spare magnetic storage cell coupled with at least a portion of the plurality of source lines, each of the at least one spare magnetic storage cell including a spare magnetic element capable of being programmed to a high resistance state by a first write current driven through the spare magnetic element in a first direction and being programmed into a low resistance state by a second write current driven through the spare magnetic element in a second direction opposite to the first direction;

at least one spare bit line corresponding to the at least one spare magnetic storage cell;

wherein the at least one spare bit line and the at least the plurality of source lines are configured to drive the first write current through the spare magnetic element in the first direction, to drive the second write current through the spare magnetic element in the second direction, and to drive the at least one read current through the spare magnetic element in the third direction.

19. The magnetic memory of claim 1 further comprising:

at least one error code correction.

20. A magnetic memory comprising:

a plurality of magnetic storage cells, each of the plurality of magnetic storage cells including a magnetic element and an selection device, the magnetic element being configured to be programmed to a high resistance state by a first write current driven through the magnetic element in a first direction and being programmed to a low resistance state by a second write current driven through the magnetic element in a second direction opposite to the first direction, the first write current and the second write current programming the magnetic element via spin transfer;

a plurality of bit lines, each of the plurality of bit lines corresponding to a first portion of the plurality of magnetic storage cells;

a plurality of source lines, each of the plurality of source lines corresponding to a second portion of the plurality of magnetic storage cells; and

a plurality of word lines, each of the plurality of word lines corresponding to a magnetic storage cell of the plurality of magnetic storage cells and for allowing current to flow through the magnetic storage cell;

wherein the plurality of bit lines and the plurality of source lines are configured to drive the first write current through the magnetic element in the first direction, to drive the second write current through the magnetic element in the second direction, and to drive at least one read current through the magnetic element in the second direction.

21. The magnetic memory of claim 20 further comprising:

a plurality of reference cells corresponding to at least a portion of the plurality of word lines and at least a portion of the plurality of source lines; and

at least one additional bit line coupled with the plurality of reference cells.

22. The magnetic memory of claim 20 further comprising:

a plurality of spare magnetic storage cells corresponding to the plurality of bit lines and the plurality of source lines, each of the plurality of spare magnetic storage cells including a spare magnetic element capable of being programmed to a high resistance state by a first write current driven through the spare magnetic element in a first direction and being programmed into a low resistance state by a second write current driven through the spare magnetic element in a second direction opposite to the first direction;

wherein the at least one spare bit line and the plurality of source lines are configured to drive the first write current through the spare magnetic element in the first direction, to drive the second write current through the spare magnetic element in the second direction, and to drive at least one read current through the spare magnetic element in a third direction that does not destabilize the low resistance state.

23. The magnetic memory of claim 20 further comprising:

a plurality of spare magnetic storage cells, each of the at least one spare magnetic storages cell including a spare magnetic element capable of being programmed to a high resistance state by a first write current driven through the spare magnetic element in a first direction and being programmed into a low resistance state by a second write current driven through the spare magnetic element in a second direction opposite to the first direction;

at least one spare bit line corresponding to the at least one spare magnetic storage cell;

at least one spare source line corresponding to the at least one spare magnetic storage cell;

wherein the at least one spare bit line and the at least one spare source line are configured to drive the first write current through the spare magnetic element in the first direction, to drive the second write current through the spare magnetic element in the second direction, and to drive at least one read current through the spare magnetic element in a third direction that does not destabilize the low resistance state.

24. A method for utilizing at least one magnetic memory cell in a memory, each of the at least one magnetic memory cell including a magnetic element capable of being programmed using spin transfer, the method comprising:

programming the at least one memory cell to a high resistance state or a low resistance state including programming the high resistance state by driving a first write current through the magnetic element in a first direction or programming the low resistance state by driving a second write current driven through the magnetic element in a second direction, the first write current and the second write current programming the magnetic element via spin transfer; and

reading the at least one magnetic memory cell by driving at least one read current through the magnetic element in a third direction that does not destabilize the low resistance states;

wherein the second direction and the third direction are the same.

25. The method of claim 24 wherein the second direction is opposite to the first direction.

26. The method of claim 24 wherein the programming includes driving the first write current and the second write current between at least one bit line and at least one source line.

27. The method of claim 24 wherein the reading includes driving the at least one read current between at least one bit line and at least one source line.

28. The method of claim 24 wherein at least one selection device corresponds to the at least one magnetic storage cell and wherein the programming further includes:

utilizing at least one word line to selectively activate the at least one selection device to allow the first write current or the second write current to flow through the at least one magnetic storage cell.

29. The method of claim 24 wherein at least one selection device corresponds to the at least one magnetic storage cell and wherein the reading further includes:

utilizing at least one word line to selectively activate the at least one selection device to allow the at least one read current to flow through the at least one magnetic storage cell.

30. The method of claim 24 wherein the magnetic element includes a pinned layer having a first magnetization pinned in a pinned direction, a spacer layer, and a free layer having a second magnetization, the spacer layer residing between the pinned layer and the free layer, the free layer being configured such that the magnetic element is programmed to the high resistance state by the first write current driven through the magnetic element in the first direction and being programmed into the low resistance state by the second write current driven through the magnetic element in a second direction opposite to the first direction.

31. The method of claim 30 wherein the spacer layer is a barrier layer.

32. The method of claim 30 wherein the spacer layer is conductive.

33. The method of claim 30 wherein the magnetic element further includes an additional spacer layer and an additional pinned layer, the free layer residing between the additional spacer layer and the spacer layer, the additional spacer layer residing between the free layer and the additional pinned layer.

34. The method of claim 33 wherein the spacer layer is a barrier layer.

35. The method of claim 34 wherein the additional spacer layer is an additional barrier layer.

36. The method of claim 34 wherein the additional spacer layer is conductive.

37. The method of claim 34 wherein the spacer layer is conductive.

38. The method of claim 37 wherein the additional spacer layer is an additional barrier layer.

39. The method of claim 37 wherein the additional spacer layer is conductive.

40. The method of claim 24 further comprising:

programming at least one reference cell; and

providing the at least one read current to the at least one reference cell.