Perpendicular magnetic random access memory (MRAM) device with a stable reference cell

• US 8,559,215 B2
• Filed: 01/27/2012
• Issued: 10/15/2013
• Est. Priority Date: 07/20/2011
• Status: Active Grant

• Current Assignee: Avalanche Technology Incorporated
• Original Assignee: Avalanche Technology Incorporated
• Inventors: Zhou, Yuchen, Huai, Yiming
• Primary Examiner(s): Zarabian, Amir
• Assistant Examiner(s): HUERTA, PABLO S
• Application Number:
  US13/360,524
• Publication Number:
  US 20130021841A1
• Time in Patent Office: 627 Days
• Field of Search: 365/158
• US Class Current: 365/158
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• 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 11/5607 using magnetic storage elements
• CPC Class Codes: Y10S 977/933 Spintronics or quantum computing
• CPC Class Codes: Y10S 977/935 Spin dependent tunnel, SDT, junction, e.g. tunneling magnetoresistance, TMR

Abstract

A magnetic random access memory (MRAM) element is configured to store a state when electric current flows and includes a first magnetic tunnel junction (MTJ) for storing a data bit and a second MTJ for storing a reference bit. The direction of magnetization of the FL is determinative of the data bit stored in the at least one MTJ. Further, the MTJ includes a magnetic reference layer (RL) having a magnetization with a direction that is perpendicular to the film plane, and a magnetic pinned layer (PL) having a magnetization with a direction that is perpendicular to the film plane. The direction of magnetization of the RL and the PL are anti-parallel relative to each other in the first MTJ. The direction of magnetization of the FL, the RL and the PL are parallel relative to each other in the second MTJ.

Claims

1. A magnetic random access memory (MRAM) element configured to store a state when electric current flows therethrough comprising:

at least one magneto tunnel junction (MTJ) configured to store a data bit including,

a magnetic free layer (FL) having a switchable magnetization with a direction that is perpendicular to a film plane, the direction of magnetization of the FL being determinative of the data bit stored in the at least one MTJ;

a magnetic reference layer (RL) having a magnetization with a direction that is perpendicular to the film plane;

a magnetic pinned layer (PL) having a magnetization with a direction that is perpendicular to the film plane;

a junction layer (JL) positioned between the FL and the RL wherein a change of the magnetization direction of the FL relative to the magnetization of the RL produces a resistance change across the JL;

a spacer layer (SL) disposed immediately adjacent to the PL, wherein the directions of magnetization of the RL and the PL of the at least one MTJ being anti-parallel relative to each other,

further wherein when electric current is applied to the first at least one MTJ, the magnetization direction of the FL thereof switches during a write operation, whereas, the direction of magnetization of the RL and the PL thereof remain the same;

at least another MTJ configured to store a reference bit that is used to compare with the at least one MTJ to retrieve the data bit stored in the at least one MTJ, the at least another MTJ including,

a magnetic free layer (FL) having a switchable magnetization with a direction that is perpendicular to the film plane, the direction of magnetization of the FL being determinative of the data bit stored in the at least one MTJ;

a magnetic reference layer (RL) having a magnetization with a direction that is perpendicular to the film plane;

a magnetic pinned layer (PL) having a magnetization with a direction that is perpendicular to the film plane,

a junction layer (JL) positioned between the FL and the RL, wherein a change of the magnetization direction of the FL of the at least another MTJ relative to the magnetization direction of the RL thereof produces a resistance change across the JL of the at least another MTJ;

a spacer layer (SL) disposed immediately adjacent to the PL,

wherein the directions of magnetizations of the RL and the PL of the at least another MTJ being parallel relative to each other.

2. The MRAM element of claim 1, wherein the at least one MTJ and the at least another MTJ are formed on the same die.

3. The MRAM element of claim 1, wherein the at least one MTJ and the at least another MTJ have the same structure.

4. The MRAM element of claim 1, wherein the directions of magnetizations of the RL and PL of the at least one MTJ and the at least another MTJ are effectuated either during manufacturing of the MRAM element or thereafter.

5. The MRAM element of claim 1, wherein the JL of each of the at least one MTJ and the at least another MTJ is made of MgO, alumina, ZnO, Cu, or Cu nano-pillars within an oxide.

6. The MRAM element of claim 1, wherein the direction of magnetization of each of the at least one MTJ and the second at least another MTJ can be switched by the electric current through the MTJ stack by spin transfer torque (STT) effect.

7. The MRAM element of claim 1, wherein the PL and RL are disposed on the same side of the JL opposing the FL in each of the at least one MTJ and the at least another MTJ.

8. The MRAM element of claim 7, wherein in each of the at least one MTJ and the at least another MTJ, the PL is separated from a respective RL by the SL formed in between.

9. The MRAM element of claim 8, wherein the SL of each of the at least one MTJ and the at least another MTJ produces an anti-ferromagnetic exchange coupling between a respective RL and a respective PL.

10. The MRAM element of claim 8, wherein the SL of each of the at least one MTJ and the at least another MTJ produces a ferromagnetic exchange coupling between a respective RL and a respective PL.

11. The MRAM element of claim 1, wherein the PL and FL are disposed on the same side of the JL opposing the RL in each of the at least one MTJ and the at least another MTJ.

12. The MRAM element of claim 11, wherein in each of the at least one MTJ and the at least another MTJ, the PL is separated from the respective FL by SL formed in between.

13. The MRAM element of claim 12, wherein the SL of each of the at least one MTJ and the at least another MTJ produces an anti-ferromagnetic exchange coupling between a respective FL and a respective PL.

14. The MRAM element of claim 12, wherein the SL of each of the at least one MTJ and the at least another MTJ produces a ferromagnetic exchange coupling between a respective FL and a respective PL.

15. The MRAM element of claim 1, wherein the SL of each of the at least one MTJ and the at least another MTJ is made of non-magnetic layer.

16. The MRAM element of claim 15, wherein the SL of each of the at least one MTJ and the at least another MTJ is made of Ru, Ta, Ti, MgO, Cu, Hf, ZnO, IrMn, PtMn, FeRh, or alumina.

17. The MRAM element of claim 1, wherein the RL and the PL of the at least one MTJ reduces each other'"'"'s magnetic field produced within the FL.

18. The MRAM element according to claim 1, wherein the RL and the PL of the at least another MTJ enhance each other'"'"'s magnetic field produced within the FL.

19. The MRAM element of claim 1, wherein the RL and the PL of the at least one MTJ each generate a magnetic field that cancel each other.

20. A magnetic random access memory (MRAM) element configured to store a state when electric current flows therethrough comprising:

at least one magneto tunnel junction (MTJ) configured to store a data bit including,

a magnetic free layer (FL) having a switchable magnetization with a direction that is perpendicular to a film plane, the direction of magnetization of the FL being determinative of the data bit stored in the at least one MTJ;

a magnetic reference layer (RL) having a magnetization with a direction that is perpendicular to the film plane;

a magnetic pinned layer (PL) having a magnetization with a direction that is perpendicular to the film plane;

a junction layer (JL) positioned between the FL and the RL wherein a change of the magnetization direction of the FL relative to the magnetization of the RL produces a resistance change across the JL;

a spacer layer (SL) disposed immediately adjacent to the PL, wherein the directions of magnetization of the RL and the PL of the at least one MTJ being anti-parallel relative to each other,

further wherein when electric current is applied to the at least one MTJ, the magnetization direction of the FL thereof switches during a write operation, whereas, the direction of magnetization of the RL and the PL thereof remain the same;

at least another MTJ configured to store a reference bit that is used to compare with the at least one MTJ to retrieve the data bit stored in the at least one MTJ, the at least another MTJ including,

a magnetic free layer (FL) having a switchable magnetization with a direction that is perpendicular to the film plane, the direction of magnetization of the FL being determinative of the data bit stored in the at least one MTJ;

a magnetic reference layer (RL) having a magnetization with a direction that is perpendicular to the film plane;

a magnetic pinned layer (PL) having a magnetization with a direction that is perpendicular to the film plane,

a junction layer (JL) positioned between the FL and the RL, wherein a change of the magnetization direction of the FL of the at least another MTJ relative to the magnetization direction of the RL thereof produces a resistance change across the JL of the at least another MTJ;

a spacer layer (SL) disposed immediately adjacent to the PL,

wherein the directions of magnetizations of the RL and the PL of the at least another MTJ being parallel relative to each other,

further wherein the PL and RL are disposed on the same side of the JL opposing the FL in each of the at least one MTJ and the at least another MTJ and in each of the at least one MTJ and the at least another MTJ, the PL is separated from a respective RL by the SL formed in between, wherein the SL of each of the at least one MTJ and the at least another MTJ eliminates any type of exchange coupling between a respective RL and a respective PL.

21. A magnetic random access memory (MRAM) element configured to store a state when electric current flows therethrough comprising:

at least one magneto tunnel junction (MTJ) configured to store a data bit including,

a magnetic free layer (FL) having a switchable magnetization with a direction that is perpendicular to a film plane, the direction of magnetization of the FL being determinative of the data bit stored in the at least one MTJ;

a magnetic reference layer (RL) having a magnetization with a direction that is perpendicular to the film plane;

a magnetic pinned layer (PL) having a magnetization with a direction that is perpendicular to the film plane;

a junction layer (JL) positioned between the FL and the RL wherein a change of the magnetization direction of the FL relative to the magnetization of the RL produces a resistance change across the JL;

a spacer layer (SL) disposed immediately adjacent to the PL, wherein the directions of magnetization of the RL and the PL of the at least one MTJ being anti-parallel relative to each other,

further wherein when electric current is applied to the at least one MTJ, the magnetization direction of the FL thereof switches during a write operation, whereas, the direction of magnetization of the RL and the PL thereof remain the same;

at least another MTJ configured to store a reference bit that is used to compare with the at least one MTJ to retrieve the data bit stored in the at least one MTJ, the at least another MTJ including,

a magnetic free layer (FL) having a switchable magnetization with a direction that is perpendicular to the film plane, the direction of magnetization of the FL being determinative of the data bit stored in the at least one MTJ;

a magnetic reference layer (RL) having a magnetization with a direction that is perpendicular to the film plane;

a magnetic pinned layer (PL) having a magnetization with a direction that is perpendicular to the film plane,

a junction layer (JL) positioned between the FL and the RL, wherein a change of the magnetization direction of the FL of the at least another MTJ relative to the magnetization direction of the RL thereof produces a resistance change across the JL of the at least another MTJ;

a spacer layer (SL) disposed immediately adjacent to the PL,

wherein the directions of magnetizations of the RL and the PL of the at least another MTJ being parallel relative to each other,

further wherein the PL and FL are disposed on the same side of the JL opposing the RL in each of the at least one MTJ and the at least another MTJ and in each of the at least one MTJ and the at least another MTJ, the PL is separated from the respective FL by SL formed in between, wherein the SL of each of the at least one MTJ and the at least another MTJ eliminates any type of exchange coupling between a respective FL and a respective PL.