JP2003198001A - Magnetoresistive effect device and memory using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an MRAM memory cell to be reduced in size, restrained from magnetically affecting an adjacent memory cell, and improved in capacity. <P>SOLUTION: A magnetoresistive device is equipped with a first conductor 31 serving as a word line, a second conductor 32 serving as a bit line, and a magnetoresistive effect film arranged and connected between the conductors 31 and 32. The conductors 31 and 32 are each connected to magnetic layers 21 and 22 respectively, the first conductor 31 is smaller in width than the magnetic layer 21 connected to the conductor 31. Furthermore, an additional magnetic material 40 is provided on the first conductor 31, and the first conductor 31 is sandwiched in between the magnetic layer 21 and the additional magnetic material 40. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive effect element and a memory (magnetic random access memory: MRAM) using the same.

[0002]

2. Description of the Related Art MRAM is being researched as an element capable of solving volatility, which is one drawback of a conventionally used DRAM (Dynamic Random Access Memory).

In the structure of the MRAM, as shown in FIG. 6, a plurality of magnetoresistive elements are arranged as a memory cell 1, an X-address decoder 2 selects the X direction of the arrangement of the memory cells 1, and a Y- By selecting the array of the memory cells 1 in the Y direction by the address decoder 3, a specific one memory cell 1 can be selected. Then, the change in the resistance value of the magnetoresistive effect element forming each memory cell 1 is held as data.

FIG. 7 is a sectional view simply showing the structure of each magnetoresistive effect element. The magnetoresistive effect element shown in FIG. 7 is an element using the tunneling magnetoresistive effect (TMR), that is, a tunnel magnetoresistive effect element (hereinafter referred to as a TMR element), and the tunnel barrier layer 10 and the two magnetic layers 1 are used.
An upper magnetic layer 1 having a TMR film structure sandwiched between 1 and 12
Reference numeral 1 denotes a layer in which the magnetization method can be freely changed (free layer), and the lower magnetic layer 12 is a layer in which the magnetization direction is fixed (pinned layer). Conductors 13 and 14 are further formed outside the magnetic layers. These conductors 13 and 14 are wired to each TMR element as the memory cell 1 as shown in FIG.

In the structure of the TMR element shown in FIG. 7, if the upper conductor 13 is a word line (wiring in the row direction in the memory cell array) and the lower conductor 14 is a bit line (wiring in the column direction in the memory cell array), the word is formed. By passing a current through both the line and the bit line, the magnetization direction of the magnetic layer 11, which is the free layer, can be selected by the combined current magnetic field generated by both the word line and the bit line. That is, it is possible to change the magnetization direction of the free layer by changing the direction of the current.

The magnetic layer 12 serving as a pinned layer against this change
Is magnetized in a fixed direction, the magnetic layer 11
It becomes possible to create two states, parallel and anti-parallel, with respect to the directions of magnetization in and 12.

Regarding the TMR element, the above two magnetic layers 1
When the magnetization directions of 1 and 12 are the same, the tunnel barrier layer 1
There is a property that resistance to a current flowing through 0 is low (R), and that in the case of antiparallel, it is high (R + ΔR). That is, the resistance value R and R + ΔR can be stored in correspondence with the data of 0 and 1 (or vice versa).

[0008]

However, the above conventional structure has the following problems.

In order to increase the capacity of the memory in the conventional configuration, it is necessary to reduce the size of each TMR element, and the shape of each memory cell is also reduced accordingly. Naturally, the width in the plane direction of the magnetic layer shown in FIG. 7 also becomes smaller. Considering the magnetic field penetrating into the magnetic layer 11 at this time, generally, when the external magnetic field invades and the length of the magnetic layer becomes shorter in the outgoing direction (horizontal direction), the demagnetizing field becomes correspondingly larger and the invading direction. The generated external magnetic field tends to be extremely small.

As a measure against this, it is effective to increase the current flowing through the conductor (word line, lead wire) to increase the current magnetic field formed around the conductor.
In order to reduce the size of the memory cell, it is also necessary to make the conductor through which the current flows thinner, so that there is a limit in flowing more current through the thinner conductor in terms of heat generation and current consumption. As a rule of thumb for design rules in general semiconductor manufacturing, a current of about 1 mA is limited for a conductor having a thickness of 0.1 μm and a conductor having a width of 1 μm. Further, a large current naturally causes a large current magnetic field formed outside the conductor, which may possibly magnetically affect other memory cells formed adjacently.

Japanese Patent Application No. 2000-90658 discloses a structure in which a magnetic flux control layer made of a ferromagnetic material is provided on one magnetic layer of a magnetoresistive effect film, but a giant magnetoresistive effect (GMR) element is used. It is premised on the use, and a gap (insulating layer) is provided between the one magnetic layer and the magnetic flux control layer.

The present invention has been made in view of the above inconvenience. Therefore, the first object of the present invention is to use it as a memory cell of an MRAM, and to reduce the size of the memory cell and an adjacent memory cell. The present invention aims to provide a magnetoresistive effect element capable of reducing the magnetic influence of, and eventually forming a large capacity MRAM.

A second object of the present invention is to increase the storage capacity by using the magnetoresistive effect element to reduce the size of the memory cell and reduce the magnetic influence on the adjacent memory cell. It is to provide a memory that can be used.

Other objects and novel features of the present invention will be clarified in the embodiments described later.

[0015]

In order to achieve the above object, the invention of claim 1 is a magnetoresistive effect element in which a conductor for energizing a magnetoresistive effect film is provided, wherein the conductor is the magnetoresistive effect film. Connected to the magnetic layer forming the magnetic layer, the width of the conductor is narrower than the width of the magnetic layer connected to the magnetic layer, and an additional magnetic body is provided on the conductor, and the magnetic layer and the additional magnetic body are provided. It is characterized in that the conductor is placed between and.

A magnetoresistive effect element according to a second aspect of the present invention is characterized in that, in the first aspect, the magnetic layer and the additional magnetic body are connected at a portion where the conductor is not formed.

The magnetoresistive effect element according to the invention of claim 3 is characterized in that, in claim 1 or 2, the conductor is a non-magnetic metal.

According to a fourth aspect of the present invention, in the magnetoresistive effect element according to the third aspect, the conductor is Cu, Au, A.
It is characterized by being either l or Ag.

The magnetoresistive effect element according to claim 5 of the present invention is the magnetoresistive effect element according to claim 1, 2, 3 or 4, wherein the magnetoresistive effect film is arranged so as to sandwich the tunnel barrier layer. It is characterized in that it has a structure of a tunnel magnetoresistive film including two magnetic layers.

According to a sixth aspect of the present invention, in the magnetoresistive effect element according to the first, second, third, fourth or fifth aspect, the easy axis of magnetization of the magnetic layer connected to the conductor is in the longitudinal direction of the conductor. It is characterized by being.

In the memory according to the invention of claim 7, the magnetic field is arranged and connected between the first conductor which becomes the word line, the second conductor which becomes the bit line, and the first and second conductors, respectively. A resistance effect film, the first and second conductors are respectively connected to the magnetic layers forming the magnetoresistive effect film, and the conductor width of at least one of the first and second conductors is the magnetic field to which it is connected. It is characterized in that it is formed narrower than the width of the layer, an additional magnetic body is provided on the at least one conductor, and the conductor is sandwiched between the magnetic layer and the additional magnetic body.

According to an eighth aspect of the present invention, in the memory according to the seventh aspect, the magnetic layer and the additional magnetic body are connected at a portion where the conductor is not formed.

According to a ninth aspect of the present invention, in the memory according to the seventh or eighth aspect, the conductor is a nonmagnetic metal.

According to a tenth aspect of the present invention, in the memory according to the ninth aspect, the conductor is any one of Cu, Au, Al and Ag.

According to claim 11 of the present invention, in the memory according to claim 7, 8, 9 or 10, the magnetoresistive film is a tunnel barrier layer and two magnetic layers arranged so as to sandwich the tunnel barrier layer. And a tunnel magnetoresistive effect film structure having a layer.

According to a twelfth aspect of the present invention, in the memory according to the seventh, eighth, ninth, tenth or eleventh aspect, one of the first and second conductors is connected to a magnetic layer whose magnetization direction can be changed. The magnetic easy axis of the magnetic layer is in the longitudinal direction of the conductor connected to the magnetic layer.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a magnetoresistive element and a memory using the same according to the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention. FIG. 1 shows the structure of a magnetoresistive effect element that constitutes the memory cell 1, and FIG. 2 shows a memory in which a plurality of memory cells 1 shown in FIG. 1 are arranged. (MRAM) is shown.

In these figures, the memory cell 1 has a magnetoresistive effect film (main body of a magnetoresistive effect element) having a tunnel barrier layer 20 and two magnetic layers 21 and 22 arranged so as to sandwich the tunnel barrier layer 20. Part), and the first and second conductors 31 and 32 as word lines and bit lines connected thereto, and the magnetoresistive effect element. The magnetoresistive effect film having the tunnel barrier layer 20 and the magnetic layers 21 and 22 has a tunnel magnetoresistive effect (TM).
R) film structure, the tunnel barrier layer 20 is formed of an oxide such as alumina, and the upper and lower magnetic layers 21, 22 are Fe, Co, Ni, FeNi, FeCo, FeCoN.
It is a metal magnetic body composed of one or more layers containing i and CoZrNb. The upper magnetic layer 21 is a layer (free layer) whose magnetization method can be freely changed, and the lower magnetic layer 2
2 is a layer in which the magnetization direction is fixed (Pinn (Pinn
ed) layer).

The magnetic layer 21 serving as the free layer is connected to the first conductor 31 forming the word line. First
The conductor 31 has a width smaller than that of the magnetic layer 21, which is a free layer, and the additional magnetic body 4 is formed on the conductor 31.
By providing 0, the conductor 31 is sandwiched between the magnetic layer 21 and the additional magnetic body 40. Specifically, in the cross-sectional direction of FIG. 1, the additional magnetic body 4 is arranged from above the first conductor 31.
0 is laminated so that the conductor 31 is included in the magnetic body. Both side portions 31A and 31B of the conductor 31 are also covered with the additional magnetic body 40, and the conductor 31 and the additional magnetic body 40 are respectively free layers. The magnetic layer 21 is closely adhered.

With this configuration, the magnetic field generated by the first conductor 31 forming the word line can generate a magnetic field in the magnetic layer 21, which is a free layer, with almost no demagnetizing field. That is, the additional magnetic body 40 functions as a magnetic yoke, and the circulating magnetic field formed in the word line can be configured as a closed magnetic path by the magnetic body forming the free layer. Therefore, it is extremely effective as compared with the case where the closed magnetic path is not configured. The current magnetic field of the word line can be formed in the free layer.

The magnetic layer 21, which is the free layer, is usually
Although having magnetic anisotropy, in this case, the relationship between the rotating direction of the additional magnetic body 40 acting as a magnetic yoke and the easy axis of magnetization of the magnetic layer 21 is preferably such that the rotating direction is perpendicular to the easy axis. . Specifically, the easy magnetization axis of the magnetic layer 21 connected to the first conductor 31, which is a word line, is set in the longitudinal direction (wiring direction) of the first conductor 31.

As shown in FIGS. 2 and 6, the memory cell 1 shown in FIG. 1 is formed at a position where a first conductor 31 forming a word line and a second conductor 32 forming a bit line intersect with each other. To be done. For example, M × N (M and N are natural numbers) memory cells are arranged in a configuration of M word side and N bit side. Here, it is preferable that the shape of each memory cell 1 is such that the direction in which the additional magnetic body 40 as a magnetic yoke turns is shortened and that the vertical direction (the direction along the word line) is lengthened. This is because the magnetic field in the direction of rotation of the additional magnetic body 40 like the magnetic field due to the current of the word line penetrates into the magnetic layer 21 which is the free layer without receiving the demagnetizing field, but the current magnetic field due to the bit line causes the demagnetizing field. Receive and invade the free layer. Therefore, it is better to set it longer to reduce the demagnetizing field to some extent.

Although the word line has a conductor width narrower than that of the magnetic layer on the TMR film side when passing through the TMR element, it may be set to a required width once it is separated from the TMR element. That is, the current capacity to be passed can be increased so that it can be widened.

Further, in the TMR element, it seems that the current capacity that can be made to flow decreases when the width of the word line is narrowed, but since the magnetic body forming the magnetic layer 21 which is a free layer is a metal magnetic body, it is basically Since the current also flows in the metal magnetic body and the cross section through which the current passes becomes large, the current resistance does not extremely increase at the connection portion to the TMR element.

Further, the first and second word lines and bit lines are formed.
The second conductors 31 and 32 are preferably made of a metal selected from non-magnetic good conductors such as Cu, Au, Al, and Ag. Basically, these metals are good conductors with low specific resistance. On the other hand, as described above, since the magnetic layer 21 and the additional magnetic body 40 forming the TMR element are also metal magnetic bodies, current flows, but the specific resistance of the metal magnetic body is about 10 to 100 times different from that of the good conductor. Therefore, in reality, a current mainly flows in a good conductor with low impedance.

Next, writing of data to the memory cell 1 having the structure of the TMR element is free by the combined magnetic field of the current magnetic fields of the first conductor 31 forming the word line and the second conductor 32 forming the bit line. This is performed by changing the magnetization direction of the magnetic layer 21, which is a layer. For example, in FIG.
In (A), when the current Iw of the word line is rightward and the current Ib of the bit line is upward (this state is assumed to be a state where 1 as data is written), current magnetic fields Mw and Mb are generated by the respective conductors, A synthetic magnetic field Mu is formed inside the intersection (between the word line and the bit line). At this time, the synthetic magnetic field Mu enters the magnetic layer 21 of the free layer as an external magnetic field and passes in the direction of Mu in FIG. 3B. At this time, when the magnetic layer 21 as the free layer has an easy axis of magnetization in the word line direction, the magnetic layer 21 as the free layer is formed after the external magnetic field Mu disappears (after the writing is completed).
Stable magnetization is carried out in the direction of the easy axis shown in (C), and 1 is written as data.

Further, FIG. 4A shows a state in which only the current (Ib) direction of the bit line is switched from that in FIG. 3A (this state is assumed to be a state in which 0 as data is written). . FIG. 4B shows the magnetic layer 2 as a free layer.
1 shows the direction of the external magnetic field Mu that invades 1 (FIG. 3).
It is rotated 90 degrees from the Mu direction in (B)). Similar to FIG. 3, when the magnetic layer 21 as a free layer has an easy axis of magnetization in the word line direction, the magnetic layer 2 as a free layer after the external magnetic field Mu disappears (after writing is completed).
1 is stably magnetized in the direction of the easy axis of magnetization shown in FIG.
0 is written as data.

The first conductor 31 forming the word line as described above
The current magnetic field can be effectively applied to the free magnetic layer 21. On the other hand, the second conductor 32 forming the bit line
With regard to the above, since the above structure is not applied, a current magnetic field is applied to the free magnetic layer 21 from below as in the conventional case. However, since the thickness of the magnetic layer 22 that forms the pinned layer is 100 nm or less and the tunnel barrier layer 20 is also formed that is 10 nm or less, the absolute value of the distance from the second conductor 32 to the magnetic layer 21 that forms the free layer. Is very small, it is quite possible to apply the bit line current field to the free layer. However, the magnetic field cannot be efficiently applied as compared with the case of the word line, and the magnetic field of the same level as in the conventional case is supplied.

However, since it is possible to effectively take measures on the word line side, a large number of memory cells are formed on the word line side, that is, M on the word side and N on the bit side.
This is particularly effective when M> N when × N memory cells are arranged. At this time, when the actual wiring on the word line side becomes long in the above relationship, the mutual magnetic coupling between the word lines may increase, but this can be avoided by the structure of the present embodiment. That is, the closed magnetic path is formed so as to surround the word line. As a matter of course, the longer the word line side is, the larger the conductor resistance becomes. However, the structure of the present embodiment can reduce the current amount on the word line side, so that the current loss can also be reduced.

Reading data from the memory cell 1
This can be carried out in the same manner as in the prior art by utilizing the fact that the resistances are different when the directions of magnetization of the two magnetic layers 21 and 22 of the TMR element are the same and when they are antiparallel.

Further, both writing and reading of data are executed for the memory cell 1 connected to the word line and the bit line selected by the X-address decoder 2 and the Y-address decoder 3 of FIG. Become.

According to this embodiment, the following effects can be obtained.

(1) The upper first conductor 31 is a magnetoresistive film (the tunnel barrier layer 20 and the magnetic layers 2 above and below it).
1, 22) connected to the magnetic layer 21 (free layer), and the width of the conductor 31 is formed smaller than the width of the magnetic layer 21, but by providing the additional magnetic body 40 on the conductor 31, the magnetic layer The conductor 31 can be sandwiched between 21 and the additional magnetic body 40, and a magnetic field can be efficiently applied to the magnetic layer 21, which is a free layer. Further, the magnetic layer 21 and the additional magnetic body 4
If 0 is connected at a portion where the conductor 31 is not formed, the magnetic layer 21 and the additional magnetic body 40 are provided around the conductor 32.
It is possible to form a closed magnetic path consisting of and, to apply the magnetic field to the magnetic layer 21 more efficiently, and it is possible to reverse the magnetization of the magnetic layer 21 with a small current consumption.

(2) By forming a closed magnetic path composed of the magnetic layer 21 and the additional magnetic body 40 around the conductor 31, the magnetic flux due to the current magnetic field passes through the closed magnetic path, and the leakage of the magnetic flux to the surroundings is extremely small. Therefore, even when a plurality of conductors 31 are arranged in parallel as word lines, magnetic inductive coupling between the word lines can be avoided.

(3) From the above, each memory cell 1 (in other words, TMR element) constituting the MRAM can be downsized, and a small-sized and large-capacity MRAM can be manufactured.

FIGS. 5 (A) and 5 (B) are other embodiments of the present invention, each of which constitutes a memory cell 1.
An R element is shown. The figure (A) shows T as a magnetoresistive film.
The magnetic layer 21 serving as the free layer of the MR film has a downwardly convex shape, and the width of the upper surface of the magnetic layer 21 to which the first conductor 31 is closely adhered and connected is equal to that of the tunnel barrier layer 20 and the pinned layer. Is set to be larger than the width of the magnetic layer 22. In FIG. 2B, the width of the entire magnetic layer 21 serving as the free layer is defined as the magnetic layer 2 serving as the tunnel barrier layer 20 and the pinned layer.
It is set larger than the width of 2. Others are the same as in the case of FIG. 1, and the same or corresponding parts will be denoted by the same reference numerals and description thereof will be omitted.

With the configuration shown in FIGS. 5A and 5B, TM
There is an advantage that the magnetic layer 21, which is a free layer, and the first conductor 31 arranged thereon can be set wide without being restricted by the width of the tunnel barrier layer 20 of the R film.

In each of the above embodiments, the first upper side
The width of the conductor 31 is reduced to be the free magnetic layer 21.
Although the additional magnetic body 40 connected to the second conductor 32 is provided, the additional magnetic body is also provided below the second conductor 32 so that the magnetic field is effectively applied to the free magnetic layer 21 of the second conductor 32 on the lower side. It may be provided.

In each of the above embodiments, the memory is configured by using the conductor 31 as the word line and the conductor 32 as the bit line, but the memory may be configured by using the conductor 31 as the bit line and the conductor 32 as the word line.

Although the embodiment of the present invention has been described above, it is obvious to those skilled in the art that the present invention is not limited to this and various modifications and changes can be made within the scope of the claims. Ah

[0052]

As described above, according to the present invention,
By providing an additional magnetic body to the conductor connected to the magnetic layer capable of changing the magnetization included in the magnetoresistive effect element,
Since the conductor is arranged so as to be sandwiched between the magnetic layer and the additional magnetic body, the current magnetic field when the conductor is energized can be effectively applied to the magnetic layer, and in order to change the magnetization of the magnetic layer, It is possible to reduce the current flowing through the conductor. That is, the current consumption during writing can be reduced.

Further, since the conductor functioning as a word line or a bit line is partially or entirely covered with the additional magnetic material, magnetic inductive coupling between the conductors can be avoided even when a large number of conductors are arranged in parallel. it can.

Each TM constituting the MRAM by the above effect
The R element can be downsized, and a small size and large capacity MRAM can be manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a magnetoresistive effect element (TMR element) constituting a memory cell according to an embodiment of the present invention.

FIG. 2 is a memory in which a plurality of the memory cells are arranged (MRA
It is a perspective view showing M).

FIG. 3 is an explanatory diagram showing writing of data to the memory cell.

FIG. 4 is an explanatory diagram in the case of writing data to the memory cell, in which the magnetization direction of the free layer is opposite to that in FIG. 3;

FIG. 5 is another embodiment of the present invention, showing a TMR element forming each memory cell.

FIG. 6 is a configuration diagram of an MRAM in which a plurality of memory cells are arranged.

FIG. 7 is a cross-sectional view illustrating the structure of a TMR element that serves as a memory cell of a conventional MRAM.

[Explanation of symbols]

1 memory cell 2 X-address decoder 3 Y-address decoder 10, 20 Tunnel barrier layer 11,12,21,22 Magnetic layer 13,14,31,32 conductor 40 Additional magnetic material

Claims (12)

[Claims] 1. A magnetoresistive effect element having a conductor for energizing a magnetoresistive effect film, wherein the conductor is connected to a magnetic layer forming the magnetoresistive effect film, and the width of the conductor is the magnetic layer to which the conductor is connected. The magnetic resistance effect element is characterized in that it is formed to have a width smaller than that of No. 1, and an additional magnetic body is provided on the conductor, and the conductor is sandwiched between the magnetic layer and the additional magnetic body. 2. The magnetoresistive effect element according to claim 1, wherein the magnetic layer and the additional magnetic body are connected at a portion where the conductor is not formed. 3. The magnetoresistive effect element according to claim 1, wherein the conductor is a non-magnetic metal. 4. The magnetoresistive effect element according to claim 3, wherein the conductor is one of Cu, Au, Al and Ag. 5. A tunnel magnetoresistive film having a tunnel barrier layer and two magnetic layers arranged so as to sandwich the tunnel barrier layer, wherein the magnetoresistive film has a tunnel magnetoresistive film structure. , 2, 3 or 4 magnetoresistive effect element. 6. The easy axis of magnetization of the magnetic layer connected to the conductor is in the longitudinal direction of the conductor.
4. The magnetoresistive effect element according to 4 or 5. 7. A first conductor serving as a word line, a second conductor serving as a bit line, and a magnetoresistive effect film arranged and connected between the first and second conductors, respectively. The first and second conductors are respectively connected to the magnetic layers forming the magnetoresistive film, and the width of at least one of the first and second conductors is formed to be narrower than the width of the magnetic layer to which they are connected. Further, the additional magnetic body is provided on the at least one conductor, and the conductor is sandwiched between the magnetic layer and the additional magnetic body. 8. The memory according to claim 7, wherein the magnetic layer and the additional magnetic body are connected at a portion where the conductor is not formed. 9. The memory according to claim 7, wherein the conductor is a non-magnetic metal. 10. The memory according to claim 9, wherein the conductor is one of Cu, Au, Al and Ag. 11. The magnetoresistive film is a tunnel barrier layer, and the magnetoresistive film is arranged so as to sandwich the tunnel barrier layer.
11. The memory according to claim 7, 8, 9 or 10, which has a structure of a tunnel magnetoresistive effect film including two magnetic layers. 12. One of the first and second conductors is connected to a magnetic layer whose magnetization direction can be changed, and the easy axis of the magnetic layer is connected to the magnetic layer in the longitudinal direction of the conductor. The memory according to claim 7, 8, 9, 10 or 11.