MAGNETIC RANDOM ACCESS MEMORY AND WRITE METHOD THEREOF

• US 20080205125A1
• Filed: 02/26/2008
• Published: 08/28/2008
• Est. Priority Date: 02/27/2007
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Inaba, Tsuneo, KAJIYAMA, Takeshi
• Granted Patent: US 7,629,637 B2
• Time in Patent Office: Days
• US Class Current: 365/158
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/5607 using magnetic storage elements
• CPC Class Codes: H10B 41/00 Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type

Abstract

A magnetic random access memory includes first and second bit lines extending in a first direction, the second bit line being adjacent to the first bit line in a second direction, a first magnetoresistive effect element being connected to the first bit line and having a first fixed layer, a first recording layer, and a first nonmagnetic layer, and a second magnetoresistive effect element being adjacent to the first magnetoresistive effect element in the second direction and being connected to the second bit line and having a second fixed layer, a second recording layer, and a second nonmagnetic layer, the first and second recording layers being formed by a same first layer extending in the second direction.

Claims

1. A magnetic random access memory comprising:

a first bit line extending in a first direction;

a second bit line which is adjacent to the first bit line in a second direction different from the first direction and which extends in the first direction;

a first magnetoresistive effect element which is connected to the first bit line and which has a first fixed layer with a fixed magnetization direction, a first recording layer with an invertible magnetization direction, and a first nonmagnetic layer provided between the first fixed layer and the first recording layer, the magnetization directions of the first fixed layer and the first recording layer being parallel or antiparallel depending on the direction of a first current passed across the first fixed layer and the first recording layer; and

a second magnetoresistive effect element which is adjacent to the first magnetoresistive effect element in the second direction and which is connected to the second bit line and which has a second fixed layer with a fixed magnetization direction, a second recording layer with an invertible magnetization direction, and a second nonmagnetic layer provided between the second fixed layer and the second recording layer, the first and second recording layers being formed by a same first layer extending in the second direction, the magnetization directions of the second fixed layer and the second recording layer being parallel or antiparallel depending on the direction of a second current passed across the second fixed layer and the second recording layer.

2. The memory according to claim 1, further comprising:

a word line extending in the second direction.

3. The memory according to claim 1, wherein

projections are formed on a side surface of the first layer opposite to the first and second nonmagnetic layers between the first and second magnetoresistive effect elements.

4. The memory according to claim 1, wherein

recesses are formed on a side surface of the first layer opposite to the first and second nonmagnetic layers between the first and second magnetoresistive effect elements.

5. The memory according to claim 1, wherein

the first and second nonmagnetic layers are formed by a same second layer extending in the second direction,

the first and second fixed layers are formed by a same third layer extending in the second direction, and

the first to third layers integrally wave, and parts of the first to third layers connecting to the first and second bit lines are flat layers.

6. The memory according to claim 1, wherein

the first and second nonmagnetic layers are formed by a same second layer extending in the second direction, and

the first and second fixed layers are formed by a same third layer extending in the second direction.

7. The memory according to claim 1, wherein

the first and second nonmagnetic layers are divided, and

the first and second fixed layers are divided.

8. The memory according to claim 1, wherein

the first and second nonmagnetic layers are formed by a same second layer extending in the second direction, and

the first and second fixed layers are divided.

9. The memory according to claim 1, further comprising:

contacts which are connected to the first recording layer and which have a width in the first direction smaller than the width of the first recording layer in the first direction.

10. The memory according to claim 9, further comprising:

a cap layer which is provided between the first recording layer and the contact and which has a resistance value higher than a resistance value of the first recording layer.

11. The memory according to claim 10, wherein

an area of a surface of the cap layer on a side of the contacts is greater than an area of a surface of the contact on a side of the cap layer.

12. The memory according to claim 1, further comprising:

a first contact which is connected to the first fixed layer and which has a width in the first direction smaller than a width of the first fixed layer in the first direction; and

a second contact which is connected to the first recording layer and which has a width in the first direction smaller than a width of the first recording layer in the first direction.

13. The memory according to claim 1, wherein

the magnetizations of the first and second fixed layers and the first and second recording layers are directed perpendicular to a film surface.

14. A write method of a magnetic random access memory, the magnetic random access memory comprising:

a first bit line extending in a first direction;

a second bit line which is adjacent to the first bit line in a second direction different from the first direction and which extends in the first direction;

a first magnetoresistive effect element which is connected to the first bit line and which has a first fixed layer with a fixed magnetization direction, a first recording layer with an invertible magnetization direction, and a first nonmagnetic layer provided between the first fixed layer and the first recording layer; and

a second magnetoresistive effect element which is adjacent to the first magnetoresistive effect element in the second direction and which is connected to the second bit line and which has a second fixed layer with a fixed magnetization direction, a second recording layer with an invertible magnetization direction, and a second nonmagnetic layer provided between the second fixed layer and the second recording layer, the first and second recording layers being formed by a same first layer extending in the second direction,

the write method comprising;

passing a write current across the first fixed layer and the first recording layer, and orienting the magnetization of the first recording layer parallel or antiparallel with the magnetization of the first fixed layer in accordance with the direction in which the write current is passed, in the case of writing into the first magnetoresistive effect element,

wherein the write current is adjusted to control the expansion of the magnetization inversion of the first recording layer.

15. The method according to claim 14, wherein

the time of passing the write current is controlled, and a magnetic wall in the first layer which is moved by the passage of the write current is stopped between the first and second magnetoresistive effect elements.

16. The method according to claim 14, wherein

the range of the inversion of the magnetization in a cell is adjusted by the write current to create first to third resistance values of the first magnetoresistive effect element,

the first resistance value being created when all the magnetizations of the first recording layer are parallel with the magnetization of the first fixed layer in the cell,

the second resistance value being created when all the magnetizations of the first recording layer are antiparallel with the magnetization of the first fixed layer in the cell,

the third resistance value being created when the first recording layer has a first magnetization parallel with the magnetization of the first fixed layer and a second magnetization antiparallel with the magnetization of the first fixed layer in the cell.

17. The method according to claim 16, further comprising:

reading data in the first magnetoresistive effect element before writing into this magnetoresistive effect element.

18. The method according to claim 16, further comprising:

reading the resistance value of the first magnetoresistive effect element after writing into the first magnetoresistive effect element; and

repassing the write current across the first fixed layer and the first recording layer when the resistance value of the first magnetoresistive effect element has not reached a threshold value.

19. The method according to claim 14, wherein

projections or recesses are formed on the lateral surface of the first layer opposite to the first and second nonmagnetic layers between the first and second magnetoresistive effect elements.

20. The method according to claim 14, wherein

the magnetizations of the first and second fixed layers and the first and second recording layers are directed perpendicular to a film surface.