JP2001237470A - Magnetic tunnel junction element and magnetic memory using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the influence of a diamagnetic field due to magnetic poles at both ends due to the thinning of an element and the magnetization of a memory layer becomes unstable, since the magnetization of a ferromagnetic layer that becomes the memory layer in a magnetic tunnel junction(MTJ) element for improving sensitivity by lamination is in the direction of the inside of a surface. SOLUTION: A closed magnetic path layer 16 is provided on a ferromagnetic layer 14 that becomes the memory layer of a laminated MTJ element 1, and the ferromagnetic layer 14 and a closed magnetic path layer 16 are jointed via metal layers 15 and 15' at both ends and are separated at a central part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tunnel junction device and a magnetic memory using the same.

[0002]

2. Description of the Related Art In recent years, a magnetic tunnel junction (MTJ) element can provide a larger output than a conventional anisotropic magnetoresistive (AMR) element or giant magnetoresistive (GMR) element, so that an Applications to read heads for hard disk drives) and magnetic memories have been considered. In particular, a magnetic memory is a solid-state memory having no moving parts like a semiconductor memory, but does not lose information even when power is cut off.
It is more useful than a semiconductor memory, for example, the number of repetitions is infinite, and there is no danger of losing recorded contents even when radiation is incident.

When considering application to such magnetic heads and magnetic memories, a high resistance change rate is important. In response to such a demand, the improvement in the rate of change in resistance from the viewpoint of materials is limited, and therefore the improvement in the rate of change in resistance by the film configuration is considered. For example, Japanese Patent Application Laid-Open No. 11-16343
In JP-A-6, a high resistance change rate is realized by stacking a plurality of MTJ elements.

FIG. 5 shows the configuration of an MTJ element disclosed in Japanese Patent Application Laid-Open No. 11-163436. The MTJ element shown in FIG. 5 has a structure in which a first ferromagnetic layer 51, a first insulating layer 52, a second ferromagnetic layer 53, a second insulating layer 54, and a third ferromagnetic layer 55 are stacked. . Here, the main purpose is to apply to a magnetic head, but it is also possible to apply to a magnetic memory.

When the MTJ element having the structure shown in FIG. 5 is used for a magnetic memory, the magnetizations of the ferromagnetic layer 51, the ferromagnetic layer 53 and the ferromagnetic layer 55 are all in the film plane and are parallel or antiparallel. It is only necessary to have an effective uniaxial magnetic anisotropy as described above.

The magnetizations of the ferromagnetic layer 51 and the ferromagnetic layer 55 are substantially fixed in one direction by exchange coupling with the antiferromagnetic layer, and the memory is retained in the direction of the magnetization of the ferromagnetic layer 53. The magnetization of the ferromagnetic layer 53 serving as a memory layer is
Reading is performed by detecting that the resistance of the MTJ element is different between parallel and anti-parallel to 55. In the structure shown in FIG. 5, since two magnetic tunnel junctions are connected in series, it is possible to obtain approximately twice the output as compared with the conventional MTJ element having a single magnetic tunnel junction. .

[0007] Writing is realized by changing the direction of magnetization of the ferromagnetic layer 53 using a magnetic field generated by a current line arranged near the MTJ element.

[0008]

In the MTJ element having the above structure, since the magnetizations of the ferromagnetic layers 51, 53 and 55 are in the in-plane direction, magnetic poles are generated at both ends.
To increase the density of the magnetic memory, it is necessary to miniaturize the MTJ element. However, as the element is miniaturized, the influence of the demagnetizing field due to the magnetic poles at both ends increases.

When the ferromagnetic layers 51 and 55 are exchange-coupled with the antiferromagnetic layer, the influence of the above demagnetizing field is small.
Further, by forming the ferromagnetic layers 51 and 55 with two ferromagnetic layers that are antiferromagnetically coupled, the magnetic pole generated at the end can be made substantially zero.

However, the ferromagnetic layer 5 serving as a memory layer
Since the same method cannot be used for No. 3, the magnetization becomes unstable due to the influence of the end poles as the pattern becomes finer, and it becomes difficult to retain the memory.

In order to solve the above-mentioned problems, the present invention provides a magnetic tunnel junction element capable of stably presenting a magnetization state recorded in a memory layer even when a pattern is miniaturized, and a magnetic memory using the same. The purpose is to:

[0012]

According to the present invention, there is provided a magnetic tunnel junction device comprising at least a first magnetic layer, a first insulating layer, a second magnetic layer, a second insulating layer, and a third magnetic layer. Wherein a fourth magnetic layer is provided on either the first insulating layer laminated side or the second insulating layer laminated side of the second magnetic layer with a metal layer interposed therebetween and a central portion separated therefrom,
A closed magnetic circuit is formed by the second magnetic layer and the fourth magnetic layer.

Further, a first antiferromagnetic layer which is exchange-coupled to the first magnetic layer is laminated, and a second antiferromagnetic layer which is exchange-coupled to the third magnetic layer is laminated.

Further, a temperature at which exchange coupling between the first antiferromagnetic layer and the first magnetic layer disappears and a temperature at which exchange coupling between the second antiferromagnetic layer and the third magnetic layer disappears are different. It is characterized by.

Further, at least one of the first magnetic layer and the second magnetic layer is constituted by two or more ferromagnetic layers which are antiferromagnetically coupled via a metal layer.

Further, at least one lead wire is provided at a space between the second magnetic layer and the fourth magnetic layer.

According to the magnetic memory of the present invention, at least a first magnetic layer, a first insulating layer, a second magnetic layer, a second insulating layer, and a third magnetic layer are laminated, and the first insulating layer of the second magnetic layer is formed. A fourth magnetic layer is provided on either the lamination side or the second insulation layer lamination side with a metal layer interposed therebetween and with a central portion separated, and a closed magnetic circuit is formed by the second magnetic layer and the fourth magnetic layer. It is characterized by using a tunnel junction element.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS.

[Embodiment 1] FIG. 1 shows a configuration of an MTJ element of Embodiment 1.

In FIG. 1, the MTJ element 1 has an antiferromagnetic layer 11, a ferromagnetic layer 12, an insulating layer 13, a ferromagnetic layer 14, metal layers 15, 15 ', a ferromagnetic layer (closed magnetic circuit layer) 16, It comprises a layer 17, a ferromagnetic layer 18, and an antiferromagnetic layer 19. The ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic circuit layer) 16 have metal layers 1 at both ends.
They are joined via 5, 15 'and are separated at the center.

Here, by setting the thickness of the metal layers 15 and 15 'to a thickness at which the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) 16 are antiferromagnetically coupled, the ferromagnetic layer 14 and the ferromagnetic layer 14 are closed. Since the magnetization directions of the ferromagnetic layer (closed magnetic path layer) 16 are reversed, and the magnetizations of the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) 16 form a closed loop, The occurrence of magnetic poles can be avoided.

The antiferromagnetic layer 11 and the ferromagnetic layer 12 are exchange-coupled with each other, and the antiferromagnetic layer 19 and the ferromagnetic layer 18 are exchange-coupled, and the magnetization directions of the ferromagnetic layers 12 and 18 are fixed. .

Ferromagnetic layers 12, 14, 18 and closed magnetic circuit layer 1
As the material of No. 6, Fe, Co, Ni, or an alloy thereof can be used. The materials of the antiferromagnetic layers 11 and 19 include FeMn, NiMn, PtMn, and IrM.
An alloy such as n can be used.

The insulating layers 13 and 17 are preferably Al ₂ O ₃ films from the viewpoint of the rate of change in resistance, but other insulating films such as an oxide film and a nitride film can also be used. Further, an insulating film having a covalent bond such as a Si film, a diamond film, and a diamond-like carbon (DLC) film can also be used. Also, the metal layer 1
Metals such as Ru, Cr, and Cu or alloys thereof can be used as the materials 5 and 15 '.

The MTJ element 1 retains memory in a closed loop magnetization direction formed by the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) 16, and is formed by the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) 16. Closed-loop magnetization direction and pinned ferromagnetic layers 12, 18
The stored state is read out by a resistance change caused by the magnetization direction of と becomes parallel or antiparallel.

As described above, since the memory is maintained in the closed loop magnetization direction created by the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) 16, the magnetization of the ferromagnetic layers 12 and 18 is
They must be fixed in opposite directions by exchange coupling with 1,19.

The arrangement of such magnetization is determined by the antiferromagnetic layer 1
1 and 19 are realized by using materials having different exchange coupling magnetic field disappearing temperatures (blocking temperatures) Tb.

For example, an example in which a PtMn film is used for the antiferromagnetic layer 11 and an IrMn film is used for the antiferromagnetic layer 19 will be described. PtMn is an antiferromagnetic material having an AuCuI type ordered phase, and its Tb1 is 380 ° C. On the other hand, IrMn
Is an antiferromagnetic material having a face-centered cubic structure, and its Tb2 is 270 ° C.

First, all the layers (11 to 1) were placed in the same vacuum.
After forming 9), a magnetic field is applied in a certain direction to order the antiferromagnetic layer 11 made of a PtMn film.
Heat treatment is performed at 0 ° C. for 6 hours. As a result, the PtMn film (antiferromagnetic layer 11) is ordered, and its spins are arranged in the course of cooling under the influence of the magnetization of the ferromagnetic layer 12 oriented in the direction of the applied magnetic field. The resulting exchange coupling fixes the ferromagnetic layer 11 in the direction of the applied magnetic field.

Next, the substrate is heated to a temperature equal to or lower than Tb1 and equal to or higher than Tb2, and is cooled while applying a magnetic field in a direction opposite to the first direction (180 °). As a result, the spins of the antiferromagnetic layer 19 made of the IrMn film are rearranged in the course of cooling under the influence of the magnetization of the ferromagnetic layer 18 that is oriented in the opposite direction, and as a result, the spin of the adjacent ferromagnetic layer 18 is changed. The magnetization is fixed in a direction antiparallel to the first heat treatment.

At this time, the antiferromagnetic layer 1 made of a PtMn film
Since the magnetization directions of 1 and the ferromagnetic layer 12 are equal to or less than Tb1, the direction of the first heat treatment is maintained without being affected. As a result, the magnetization directions of the ferromagnetic layers 12 and 18 are antiparallel.

The material of the antiferromagnetic layer and the method of orienting the magnetization are not limited to those described above.
Any number of antiferromagnetic layers may be used. In addition to the method of heat treatment in a magnetic field, a method of controlling the direction of the magnetic field at the time of film formation or a method of combining these methods can also be realized as the method of orientation of magnetization. Also, when an irregular alloy film is used for the antiferromagnetic layer, it is apparent that heat treatment for ordering unlike the case of an ordered alloy film is not required.

Ferromagnetic layers 12, 14, 18 and closed magnetic circuit layer 1
It is desirable that the film thickness of No. 7 is not less than 10 ° and not more than 1000 °. If the film thickness is too small, it becomes superparamagnetic due to the influence of thermal energy. On the other hand, if the film thickness is too large, the influence of the end magnetic poles cannot be avoided in the closed magnetic circuit structure of the present invention. In addition, each magnetic layer can be composed of a multilayer film. In this case, the total film thickness may be set to 10 ° or more and 1000 ° or less.

The insulating layers 13 and 17 have a thickness of 3 ° or more and 3 ° or more.
Desirably, it is 0 ° or less. When the thickness of the insulating layers 13 and 17 is 3 ° or less, the ferromagnetic layers 12 and 14
Is likely to cause an electrical short circuit, and if the thickness of the insulating layer 13 is 30 ° or more, electron tunneling hardly occurs and the magnetoresistance ratio decreases.

Although the metal layers 15 and 15 'are separately provided in FIG. 1, it is apparent that the object of the present invention can be achieved by forming a continuous single metal layer.

Further, the ferromagnetic layer 12 or the ferromagnetic layer 18
Is composed of two ferromagnetic layers, thereby effectively preventing a magnetic pole from being generated at the end. Even if there are three or more layers, it is also possible to prevent a magnetic pole from effectively occurring at the end by adjusting the film thickness of the ferromagnetic layer to be constituted.

Next, FIG. 2 is a schematic diagram showing a case where the MTJ element 1 of the first embodiment is used for a magnetic memory 3 which can be accessed at random.

In FIG. 2, a transistor 31 has a role of selecting the MTJ element 1 at the time of reading.
The information of “0” and “1” is recorded by the magnetization directions of the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) 16 of the MTJ element 1 shown in FIG. Has a fixed magnetization direction. Ferromagnetic layer 12 and ferromagnetic layer 1
When the magnetization of the ferromagnetic layer 4 is parallel and the magnetizations of the ferromagnetic layer 18 and the ferromagnetic layer (closed magnetic path layer) 16 are parallel, the resistance is low, and when the magnetization is antiparallel, the resistance is high. Is read. On the other hand, writing is realized by reversing the magnetization directions of the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) 16 by a combined magnetic field formed by the bit line 32 and the word line 33.

Reference numeral 34 denotes a plate line.

FIG. 3 shows an example of the arrangement of the bit lines 32 and the word lines 33.

In FIG. 3, the bit line 32 and the word line 33 are pierced in the centrally separated portion of the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) 16 so that the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic path layer) are formed. The current value required for reversing the magnetization direction of the layer (16) is reduced, and the power consumption of the magnetic memory can be reduced.

The bit line 32 and the word line 33 are both electrically insulated from the ferromagnetic layer 14 and the ferromagnetic layer (closed magnetic circuit layer) 16.

The arrangement of the bit lines and the word lines is not limited to that shown in FIG. 3, and the bit lines and the word lines can be provided on the same plane. Alternatively,
It is also possible to provide both or either wiring near the outside of the MTJ element, thereby simplifying the process.

[Embodiment 2] FIG. 4 shows a configuration of an MTJ element of Embodiment 2.

In FIG. 4, the MTJ element 2 includes an antiferromagnetic layer 21, a ferromagnetic layer 22, an insulating layer 23, a ferromagnetic layer 24, metal layers 25 and 25 ', a ferromagnetic layer (closed magnetic circuit layer) 26, It comprises a layer 27, a ferromagnetic layer 28 and an antiferromagnetic layer 29. The ferromagnetic layer 24 and the closed magnetic circuit layer 26 are joined at both ends via metal layers 25 and 25 ', and are separated at the center.

Here, by setting the film thickness of the metal layers 25 and 25 ′ to a film thickness at which the ferromagnetic layer 24 and the ferromagnetic layer (closed magnetic circuit layer) 26 are antiferromagnetically coupled, the ferromagnetic layer 24 and the ferromagnetic layer 24 are closed. The magnetization directions of the ferromagnetic layer (closed magnetic path layer) 26 are reversed, and the magnetizations of the ferromagnetic layer 24 and the ferromagnetic layer (closed magnetic path layer) 26 form a closed loop. The occurrence of magnetic poles can be avoided.

The MTJ element 2 of the second embodiment is the same as the MTJ element of the first embodiment.
Unlike the J element 1, the ferromagnetic layer 22 is composed of two ferromagnetic layers 22a and 2a antiferromagnetically coupled via a metal layer 22b.
2c, and the ferromagnetic layer 22c is exchange-coupled to the antiferromagnetic layer 21. Further, similarly to the first embodiment, the antiferromagnetic layer 2
9 and the ferromagnetic layer 28 are exchange-coupled.

That is, the magnetization of the ferromagnetic layer 28 is fixed by exchange coupling with the antiferromagnetic layer 29 and the ferromagnetic layer 22 c
Is fixed by exchange coupling with the antiferromagnetic layer 21, and the ferromagnetic layer 22a is antiferromagnetically coupled via the metal layer 22b, so that the magnetization is fixed in the opposite direction to the ferromagnetic layer 22c. Have been.

The MTJ element 2 retains the memory in the magnetization direction of the closed loop formed by the ferromagnetic layer 24 and the ferromagnetic layer (closed magnetic path layer) 26, and is formed by the ferromagnetic layer 24 and the ferromagnetic layer (closed magnetic path layer) 26 The memory state is read by a resistance change caused by the magnetization direction of the closed loop and the magnetization direction of the ferromagnetic layers 22a and 28 being parallel or antiparallel.

As described above, the magnetization direction of the closed loop formed by the ferromagnetic layer 24 and the ferromagnetic layer (closed magnetic path layer) 26 and the ferromagnetic layer 22
In order to read the storage state by a resistance change caused by the magnetization directions of a and 28 being parallel or antiparallel, the magnetization direction of the ferromagnetic layer 22c must be fixed in the same direction as the ferromagnetic layer 28.

Therefore, according to the second embodiment, it is possible to fix the magnetization directions of the ferromagnetic layers 22c and 28 in a single process or in the same magnetic field direction. Can be simplified.

In the second embodiment, the ferromagnetic layer 22 is composed of two ferromagnetic layers, and the ferromagnetic layer 28 is composed of a single layer. However, the number of ferromagnetic layers is one with two fixed layers. If they are different, the same effect can be obtained.

In the second embodiment, the same antiferromagnetic material can be used for the antiferromagnetic layer 21 and the antiferromagnetic layer 29.

The MTJ element 2 can be used for a magnetic memory like the MTJ element 1.

In the above-described embodiment, only the MTJ element portion is shown. However, it is apparent that an electrode for current supply, a substrate, a protective layer, an adhesion layer, and the like are necessary in actual element formation.

[0056]

As described above, according to the present invention, a high resistance change rate and the influence of the end pole can be reduced, so that a stable magnetized state can be maintained even if the pattern is miniaturized. . Further, since the ferromagnetic layer serving as the memory layer has a closed magnetic circuit structure, the structure is stable against an external leakage magnetic field.

Also, since it has a high rate of change in resistance and can reduce the influence of the end magnetic poles, it is possible to maintain a stable magnetized state even if the pattern is miniaturized, realizing a magnetic memory with a higher degree of integration. can do. Further, power consumption of the magnetic memory can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of the present invention.

FIG. 2 is a diagram showing a configuration example of a magnetic memory using the MTJ element of the present invention.

FIG. 3 is a diagram showing an example of the arrangement of word lines and bit lines of a magnetic memory using the MTJ element of the present invention.

FIG. 4 is a diagram showing another configuration example of the present invention.

FIG. 5 is a diagram showing a configuration example of a conventional MTJ element.

[Explanation of symbols]

1, 2: MTJ element 3: magnetic memory 11, 19, 21, 29: antiferromagnetic layer 12, 14, 18, 22, 22a, 22c, 24, 2
8, 51, 53, 55: Ferromagnetic layer 13, 17, 23, 27, 52, 54: Insulating layer 15, 15 ', 25, 25', 22b: Metal layer 16, 26: Ferromagnetic layer (closed magnetic circuit layer) 31: Transistor 32: Bit line 33: Word line 34: Plate line

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuji Minami 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2G017 AA01 AD51 AD69 CB26 5D034 BA03 BA15 BA18 5E049 AA04 BA12 CB02 DB02 DB12

Claims (6)

[Claims] 1. A magnetic tunnel junction device comprising a stack of at least a first magnetic layer, a first insulating layer, a second magnetic layer, a second insulating layer, and a third magnetic layer, wherein: The insulating layer lamination side or the second
A magnetic tunnel, characterized in that a fourth magnetic layer is provided on one of the insulating layer lamination sides with a metal layer interposed therebetween and a central portion separated from the fourth magnetic layer, and a closed magnetic circuit is formed by the second magnetic layer and the fourth magnetic layer. Junction element. 2. The semiconductor device according to claim 1, wherein a first antiferromagnetic layer exchange-coupled to said first magnetic layer is laminated, and a second antiferromagnetic layer exchange-coupled to said third magnetic layer is laminated. The magnetic tunnel junction device as described in the above. 3. A temperature at which exchange coupling between the first antiferromagnetic layer and the first magnetic layer disappears and a temperature at which exchange coupling between the second antiferromagnetic layer and the third magnetic layer disappears. The magnetic tunnel junction device according to claim 2, wherein: 4. An anti-ferromagnetic coupling between at least one of the first magnetic layer and the second magnetic layer via a metal layer.
2. The semiconductor device according to claim 1, wherein said ferromagnetic layer comprises at least one ferromagnetic layer.
Or the magnetic tunnel junction device according to 2. 5. The magnetic tunnel junction device according to claim 1, wherein at least one lead wire is provided at a space between the second magnetic layer and the fourth magnetic layer. 6. A method according to claim 6, wherein at least a first magnetic layer, a first insulating layer, a second magnetic layer, a second insulating layer, and a third magnetic layer are laminated.
A fourth magnetic layer is provided on either the first insulating layer lamination side or the second insulating layer laminating side of the magnetic layer with a metal layer interposed therebetween and a central portion separated therefrom, wherein the second magnetic layer and the fourth magnetic layer A magnetic memory using a magnetic tunnel junction element in which a layer forms a closed magnetic circuit.