Current driven switching of magnetic storage cells utilizing spin transfer and magnetic memories using such cells having enhanced read and write margins

• US 20070297223A1
• Filed: 06/26/2006
• Published: 12/27/2007
• Est. Priority Date: 06/26/2006
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation, Samsung Semiconductor Incorporated (Samsung Electronics Co. Ltd.)
• Original Assignee: Renesas Technology Corporation (Renesas Electronics Corporation), Grandis, Inc. (Samsung Electronics Co. Ltd.)
• Inventors: Chen, Eugene Youjun, Huai, Yiming, Panchula, Alex Fischer, Wang, Lien-Chang, Luo, Xiao
• Granted Patent: US 7,379,327 B2
• Time in Patent Office: Days
• US Class Current: 365/173
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect

Abstract

A method and system for providing a magnetic memory is described. The magnetic memory includes magnetic storage cells in an array, bit lines, and source lines. Each magnetic storage cell includes at least one magnetic element. The magnetic element(s) are programmable by write currents driven through the magnetic element(s). Each magnetic element has free and pinned layer(s) and a dominant spacer. The magnetic memory is configured such that either the read current(s) flow from the free layer(s) to the dominant spacer if the maximum low resistance state read current divided by the minimum low resistance state write current is greater than the maximum high resistance state read current divided by the minimum high resistance state write current or the read current(s) flow from the dominant spacer to the free layer(s) if the maximum low resistance state read current divided by the minimum low resistance state write current is less than the maximum high resistance state read current divided by the minimum high resistance state write current.

Claims

1. A magnetic memory comprising:

a plurality of magnetic storage cells in an array, each of the plurality of magnetic storage cells including at least one magnetic element, the at least one magnetic element being programmable by at least one write current driven through the magnetic element, each of the at least one magnetic element having at least one free layer, a dominant spacer, and at least one pinned layer, the plurality of magnetic storage cells having a maximum high resistance state read current, a maximum low resistance state read current, a minimum high resistance state write current, and a minimum low resistance state write current, the plurality of magnetic storage cells being read by at least one read current,

a plurality of bit lines corresponding to the plurality of magnetic storage cells; and

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

wherein the plurality of magnetic storage cells, the plurality of source lines and the plurality of bit lines are configured such that at least one of the at least one read current flows from the at least one free layer to the dominant spacer if the maximum low resistance state read current divided by the minimum high resistance state write current is greater than the maximum high resistance state read current divided by the minimum low resistance state write current and the at least one read current flows from the dominant spacer to the at least one free layer if the maximum low resistance state read current divided by the minimum high resistance state write current is less than the maximum high resistance state read current divided by the minimum low resistance state write current.

2. The magnetic memory of claim 1 further comprising:

a plurality of reference cells corresponding to the plurality of magnetic storage cells;

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

a plurality of source lines corresponding to the plurality of reference cells, the plurality of bit lines and the plurality of source lines are configured to drive a reference read current through the plurality of reference cells.

3. The magnetic memory of claim 2 wherein the plurality of reference cells are arranged in a plurality of columns.

4. The magnetic memory of claim 3 wherein at least one of the plurality of columns is designated a redundant column, replacing a portion of the plurality of magnetic storage cells including at least one outlier cell.

5. The magnetic memory of claim 4 wherein at least one the outlier cell has a write current that is not within a predetermined amount of a mean write current.

6. The magnetic memory of claim 5 wherein the predetermined amount is at least 4.5 σ

.

7. The magnetic memory of claim 3 wherein at least one of the plurality of columns is configured to store error correction data.

8. The magnetic memory of claim 3 wherein the plurality of columns includes a first column and a second column, the plurality of reference cells including a reference element programmable to by the at least one write current driven through the reference, the reference element having the at least one free layer, the dominant spacer, and the at least one pinned layer, the reference element being read by the at least one read current, the first column including a first portion of the plurality of reference cells in the low resistance state, the second column including a second portion of the plurality of reference cells in the high resistance state, the first column and the second column being electrically connected.

9. The magnetic memory of claim 2 further wherein the plurality of reference cells are arranged in a plurality of rows.

10. The magnetic memory of claim 9 wherein at least one of the plurality of rows is designated a redundant row, replacing a portion of the plurality of magnetic storage cells including at least one outlier cell.

11. The magnetic memory of claim 10 wherein at least one the outlier cell has a write current that is not within a predetermined amount of a mean write current.

12. The magnetic memory of claim 11 wherein the predetermined amount is at least 4.5 σ

24. The magnetic memory of claim 10 wherein at least one the outlier cell has a write current that is not within a predetermined amount of a mean write current.

25. The magnetic memory of claim 11 wherein the predetermined amount is at least 4.5 σ

13. A method for fabricating a magnetic memory comprising:

providing a plurality of magnetic storage cells in an array, each of the plurality of magnetic storage cells including at least one magnetic element, the at least one magnetic element being programmable by at least one write current driven through the magnetic element, each of the at least one magnetic element having at least one free layer, a dominant spacer, and at least one pinned layer, the plurality of magnetic storage cells having a maximum high resistance state read current, a maximum low resistance state read current, a minimum high resistance state write current, and a minimum low resistance state write current, the plurality of magnetic storage cells being read by at least one read current,

providing a plurality of bit lines corresponding to the plurality of magnetic storage cells;

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

providing a plurality of reference cell;

wherein the plurality of magnetic storage cells, the plurality of source lines and the plurality of bit lines are configured such that at least one of the at least one read current flows from the at least one free layer to the dominant spacer if the maximum low resistance state read current divided by the minimum high resistance state write current is greater than the maximum high resistance state read current divided by the minimum low resistance state write current and the at least one read current flows from the dominant spacer to the at least one free layer if the maximum low resistance state read current divided by the minimum high resistance state write current is less than the maximum high resistance state read current divided by the minimum low resistance state write current.

14. The method of claim 13 wherein the plurality of reference cells includes a plurality of columns;

the method further comprising;

determining whether at least one outlier cell is included in the plurality of memory cells; and

designating at least one of the plurality of columns as a redundant column; and

if the at least one outlier cell exists, replacing a portion of the plurality of magnetic storage cells including at least one outlier cell.

15. The method of claim 14 wherein the at least one outlier cell determining further includes:

determining whether the at least one the outlier cell has a write current that is not within a predetermined amount of a mean write current.

16. The method of claim 13 wherein the predetermined amount is at least 4.5 σ

.

17. The method of claim 13 further comprising:

configuring a portion of the plurality of columns to store error correction data.

18. The method of claim 13 wherein the plurality of reference cells includes a plurality of rows, the method further comprising:

determining whether at least one outlier cell is included in the plurality of memory cells; and

designating at least one of the plurality of rows as a redundant rows; and

if the at least one outlier cell exists, replacing a portion of the plurality of magnetic storage cells including at least one outlier cell.

19. The method of claim 14 wherein the at least one outlier cell determining further includes:

determining whether the at least one the outlier cell has a write current that is not within a predetermined amount of a mean write current.

20. The method of claim 13 wherein the predetermined amount is at least 4.5 σ

.

21. The method of claim 13 further comprising:

configuring a portion of the plurality of columns to store error correction data.

22. The method of claim 13 wherein the plurality of reference cells are arranged in a plurality of rows.

23. The magnetic memory of claim 22 wherein at least one of the plurality of rows is designated a redundant row, replacing a portion of the plurality of magnetic storage cells including at least one outlier cell.