NONVOLATILE MEMORY DEVICE

• US 20140085968A1
• Filed: 03/12/2013
• Published: 03/27/2014
• Est. Priority Date: 09/26/2012
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: SAIDA, Daisuke, AMANO, Minoru, SHIMOMURA, Naoharu
• Granted Patent: US 8,848,433 B2
• Time in Patent Office: Days
• 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 11/1675 Writing or programming circuits or methods

Abstract

According to one embodiment, a nonvolatile memory device includes: a magnetic memory element and a control unit. The magnetic memory element includes a stacked body, and a first and a second stacked units. The first stacked unit includes a first and second ferromagnetic layers and a first nonmagnetic layer provided between the first and the second ferromagnetic layers. The second stacked unit includes a third ferromagnetic layer and a nonmagnetic tunneling barrier layer stacked with the third ferromagnetic layer. The control unit is configured to implement a first operation of setting the magnetic memory element to be in a first state. The first operation includes a first preliminary operation of applying a first pulse voltage; and a first setting operation of applying a second pulse voltage having a second rising time to the magnetic memory element after the first preliminary operation.

Claims

1. A nonvolatile memory device, comprising:

a magnetic memory element including a stacked body, the stacked body including

a first stacked unit including;

a first ferromagnetic layer having a fixed direction of magnetization;

a second ferromagnetic layer having a changeable direction of magnetization; and

a first nonmagnetic layer provided between the first ferromagnetic layer and the second ferromagnetic layer,

the first ferromagnetic layer, the second ferromagnetic layer, and the first nonmagnetic layer being stacked in a stacking direction, and

a second stacked unit stacked with the first stacked unit in the stacking direction including;

a third ferromagnetic layer having a changeable direction of magnetization; and

a nonmagnetic tunneling barrier layer stacked with the third ferromagnetic layer in the stacking direction to contact the third ferromagnetic layer; and

a control unit electrically connected to the magnetic memory element,

the control unit being configured to implement a first operation of setting the magnetic memory element to be in a first state, the first operation including;

a first preliminary operation of applying a first pulse voltage having a first rising time to the magnetic memory element; and

a first setting operation of applying a second pulse voltage having a second rising time to the magnetic memory element after the first preliminary operation, the second rising time being longer than the first rising time.

2. The device according to claim 1, wherein

the first operation is an operation of setting the direction of the magnetization of the second ferromagnetic layer to be in a first direction,

the first preliminary operation includes changing the direction of the magnetization of the third ferromagnetic layer to be in a second direction, and

the first setting operation is an operation of setting the direction of the magnetization of the second ferromagnetic layer to be in the first direction.

3. The device according to claim 2, wherein

the magnetization of the third ferromagnetic layer processes with a direction different from the second direction as an axis when the first pulse voltage is applied, and

the magnetization of the third ferromagnetic layer becomes oriented in the second direction when the first pulse voltage ends.

4. The device according to claim 3, wherein a duration tp1 of the first pulse voltage is not less than 0.75 times (Cp/2)×

(2n−

1) and not more than 1.25 times (Cp/2)×

(2n−

1) (n being an integer not less than

     1), where a period of the procession is Cp.

5. The device according to claim 1, wherein

the control unit further implements a second operation of setting the magnetic memory element to be in a second state different from the first state, and

the second operation includes:

a second preliminary operation of applying a third pulse voltage having a third rising time to the magnetic memory element; and

a second setting operation of applying a fourth pulse voltage to the magnetic memory element after the second preliminary operation, the fourth pulse voltage having a fourth rising time longer than the third rising time and a polarity different from the polarity of the second pulse voltage.

6. The device according to claim 5, wherein

the second operation is an operation of setting the direction of the magnetization of the second ferromagnetic layer to be in a third direction,

the second preliminary operation includes changing the direction of the magnetization of the third ferromagnetic layer to be in a fourth direction, and

the second setting operation is an operation of setting the direction of the magnetization of the second ferromagnetic layer to be in the third direction.

7. The device according to claim 1, wherein

a component of the magnetization of the first ferromagnetic layer in the stacking direction is larger than a component of the magnetization of the first ferromagnetic layer in a in-plane direction perpendicular to the stacking direction,

a component of the magnetization of the second ferromagnetic layer in the stacking direction is larger than a component of the magnetization of the second ferromagnetic layer in the in-plane direction, and

a component of the magnetization of the third ferromagnetic layer in the stacking direction is larger than a component of the magnetization of the third ferromagnetic layer in the in-plane direction.

8. The device according to claim 1, wherein the third ferromagnetic layer generates a high frequency magnetic field by the applying of the second pulse voltage, and the high frequency magnetic field is applied to the second ferromagnetic layer.

9. The device according to claim 1, wherein the nonmagnetic tunneling barrier layer is disposed between the first stacked unit and the third ferromagnetic layer.

10. The device according to claim 1, wherein

the second stacked unit further includes a fourth ferromagnetic layer having a fixed direction of magnetization, and

the nonmagnetic tunneling barrier layer is disposed between the third ferromagnetic layer and the fourth ferromagnetic layer.

11. The device according to claim 10, wherein an orientation of a component of the magnetization of the first ferromagnetic layer projected onto the stacking direction is the reverse of an orientation of a component of the magnetization of the fourth ferromagnetic layer projected onto the stacking direction.

12. The device according to claim 1, wherein the magnetic memory element further includes a magnetic shield covering at least a portion of a side surface of the stacked body.

13. The device according to claim 1, wherein

the stacked body further includes a second nonmagnetic layer provided between the first stacked unit and the second stacked unit, and

the second nonmagnetic layer includes one metal selected from the group consisting of ruthenium (Ru), tantalum (Ta), tungsten (W), platinum (Pt), palladium (Pd), molybdenum (Mo), niobium (Nb), zirconium (Zr), titanium (Ti), and vanadium (V) or an alloy including at least two metals selected from the group.

14. The device according to claim 1, wherein

the stacked body further includes a second nonmagnetic layer provided between the first stacked unit and the second stacked unit,

the second nonmagnetic layer includes one metal selected from the group consisting of ruthenium (Ru), osmium (Os), and iridium (Ir) or an alloy including at least two metals selected from the group, and

a thickness of the second nonmagnetic layer is not more than 3 nanometers.

15. The device according to claim 1, wherein

a length of the third ferromagnetic layer in a direction perpendicular to the stacking direction is not more than 35 nanometers, and

a length of the third ferromagnetic layer in the stacking direction is not less than 0.5 nanometers and not more than 3.5 nanometers.

16. The device according to claim 1, wherein the second stacked unit further includes:

a fourth ferromagnetic layer having a changeable direction of magnetization; and

a nonmagnetic metal layer provided between the third ferromagnetic layer and the fourth ferromagnetic layer.

17. The device according to claim 1, wherein

the second stacked unit further includes:

a fifth ferromagnetic layer stacked with the third ferromagnetic layer in the stacking direction; and

a third nonmagnetic layer provided between the third ferromagnetic layer and the fifth ferromagnetic layer, and

a component of the magnetization of the fifth ferromagnetic layer in a direction perpendicular to the stacking direction is larger than a component of the magnetization of the fifth ferromagnetic layer in the stacking direction.

18. The device according to claim 1, wherein a length of the third ferromagnetic layer in one direction perpendicular to the stacking direction is longer than a length of the third ferromagnetic layer in the stacking direction and a length of the third ferromagnetic layer in one other direction perpendicular to the one direction.

19. The device according to claim 2, wherein the control unit, in the first operation, applies a pulse voltage to the magnetic memory element to read the direction of the magnetization of the third ferromagnetic layer, and implements the first preliminary operation and the first setting operation when the direction of the magnetization of the third ferromagnetic layer is different from the second direction, and implements the first setting operation without implementing the first preliminary operation when the direction of the magnetization of the third ferromagnetic layer is the second direction.

20. The device according to claim 1, wherein

a plurality of the magnetic memory elements is provided, and

the control unit is electrically connected to each of the plurality of magnetic memory elements.