JPH11251139A - Magnetoresistance material for vertical magnetic memory, and vertical magnetic memory element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture large-scale array with ease while specific resistance is high for sufficient performance index. SOLUTION: A hard magnetic film 20 which is a magnetoresistance material is a dispersion film wherein magnetic particles are dispersed in an oxide. This is laminated between a lower part electrode 8 and an upper part electrode 7 so that coercive force in each dispersion film is different, while a ward line 6 is formed on the upper part electrode 7 with an insulating film 9 in between, thus a vertical magnetic memory is constituted. Related to forming of the magnetic film 20, a target of Co and Al is fitted to a spattering device for controlling application power with each target, or such target as different in composition ratio of Co/Al is used for controlling component amount in the film. Then, films of different coercive force are alternately formed to form a magnetic film. The coercive force of the film is 100 (Oe) or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic resistance material for a vertical magnetic memory and a vertical magnetic memory which have a large specific resistance and a sufficiently high figure of merit and are suitable for manufacturing a large-scale array.

[0002]

2. Description of the Related Art A magnetic memory stores information "1" and "0" as the direction of a magnetic film in a unit called a cell.
For reading out information, a change in magnetoresistance due to a combination with a film having magnetic properties different from that of the film storing the information is used.

[0003] The magnetoresistive memories are classified into two types, a horizontal cell and a vertical cell, in terms of structure. FIG. 4 is a perspective view showing a horizontal element. As shown in FIG. 4, in the element having a horizontal cell structure, electrodes 2 are connected to both ends of an element 1 which is a film showing a magnetoresistance, and a word line 3 extending in a direction orthogonal to the direction in which the electrodes 2 face each other. Is provided above the element 1. The word line 3 is for passing a current for assisting writing and reading of information.

As shown in FIG. 5, the element 1 is formed by laminating a two-layer film of an antiferromagnetic film 11 and a soft magnetic film 12 and a soft magnetic film 12 with a non-magnetic film 13 interposed therebetween. The magnetic field generated by the current of the word line 3 causes the soft magnetic film 1
Reading and recording of information are performed by the magnetization reversal of 2. Such a horizontal cell is disclosed in Japanese Patent Application Laid-Open No. 8-139.
No. 387 and Journal of the Japan Society of Applied Magnetics vol.20, No.1, 19
96 has been disclosed.

[0005] This horizontal structure is basically formed by adding a word line to a magnetoresistive element used for a hard disk or the like, and is easy to make. However, when this is developed into a cell array, As shown in FIG. 6A, it is necessary to connect the horizontal cells 4 in series. For this reason, the magnetoresistance change rate of the one cell becomes extremely small as shown by the following equation (1).

[0006]

## EQU1 ## MR _app. = ΔR _e / (ΣR _e + R _con )

[0007] However, MR _app. The magnetoresistance ratio per one cell 1, [Delta] R _e is the total resistance variation, .SIGMA.R _e is the total resistance, R _con shows the wiring resistance (Journal of the Magnetics Society of Japan Vo
l.20, No.1,1996, Vol.20, No.2,1996).

FIG. 7 is a perspective view showing a vertical element. As shown in FIG. 7, the element 5 is configured by alternately stacking magnetic films and non-magnetic films.
The lower electrode 8 is provided at the lower end in the stacking direction, and the upper electrode 7 is provided at the upper part. The word line 6 is stacked on the upper electrode 7 with an insulating film 9 interposed therebetween. Note that the upper electrode 7 may also serve as a word line.

When these vertical cells are connected in an array, the cells 10 are connected in parallel as shown in FIG. Therefore, even in an array having a large number of cells, one
The magnetoresistance change rates of the two cells are sufficiently large as shown in Equation 2 below. That is, even when a large number of cells are connected in an array, the decrease in the magnetoresistance ratio is extremely small as compared with the horizontal array.

[0010]

## EQU2 ## MR _app. = ΔR _e / (R _e + R _con )

However, since the element having the vertical cell structure has a structure in which a current flows perpendicularly to the film surface of the element 5, when the resistance of the element 5 is small, the change in voltage that can be taken out is extremely small. Therefore, a cell having a vertical structure requires a cell having a large magnetoresistance change rate and a large resistance itself. Therefore, a cell having a vertical structure needs to have a large magnetoresistance change and a large resistance itself. That is, as the magnetoresistive material for the vertical cell, a material having a large product of the magnetoresistance change rate and the resistance (hereinafter, referred to as a figure of merit) is required.

Also, a word line can be generated 100 times.
It is necessary that the magnetization of the memory layer can be reversed in a magnetic field of about (Oe) or less. That is, the coercive force of the memory layer needs to be 100 (Oe) or less. For this reason, conventionally, as a magnetoresistive material having a vertical element structure, a GMR laminated film and spin tunneling (Spin tunneling) have been used.
-Tunneling) membranes have been proposed (USP
5,477,482, Journal of the Japan Society of Applied Magnetics, Vol. 20, No. 2,
1996).

[0013]

SUMMARY OF THE INVENTION However, GMR
In the laminated film, although the resistance change rate of the laminated film is large, but the specific resistance is as small as several tens μΩ · cm, it is necessary to increase the film thickness in order to obtain a sufficient voltage change as a cell. However, when the film thickness is increased, the influence of the demagnetizing field increases, and as a result, the magnetic field sensitivity decreases, and the cell
Sufficient characteristics as an element cannot be obtained.

US Pat. No. 5,477,482 proposes a method for solving this problem by processing a multilayer film into a ring shape. In this method, a hole is formed in the multilayer film laminate later. The problem is that it is not suitable for large memory arrays because the ring is made.

In the case of a spin tunneling film, since an oxide film such as alumina is used for one layer of the laminated film,
Although the resistance is higher than that of the R laminated film, it is difficult to produce a uniform alumina film having a small thickness. Therefore, the spin tunneling film is not suitable for producing a large array stably. is there.

The present invention has been made in view of the above-mentioned problems, and has a large specific resistance, a sufficient figure of merit, can be easily formed, and can be easily formed in a vertical type. It is an object to provide a magnetoresistive material for a magnetic memory and a vertical magnetic memory.

[0017]

A magnetoresistive material for a vertical magnetic memory according to the present invention is characterized by comprising a film in which magnetic particles are dispersed in an oxide.

The vertical magnetic memory according to the present invention is characterized in that it is formed by laminating magnetoresistive films having magnetic particles dispersed in an oxide and having different coercive forces.

The magnetoresistive material for a vertical magnetic memory according to the present invention is a dispersion film in which magnetic particles are dispersed in an oxide.
A vertical magnetic memory can be formed. The dispersion film in which the magnetic particles are dispersed in the oxide as described above has a sufficiently high specific resistance, a high figure of merit, and is excellent as a cell material of a vertical magnetic memory. In addition, its creation is easy, which is effective for creating a large-scale array.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be specifically described with reference to the accompanying drawings. FIG. 1 is a diagram showing the structure of one cell of the vertical memory according to the present embodiment. This vertical memory cell has the same structure as that shown in FIG. The element 5 disposed between the lower electrode 8 and the upper electrode 7 is formed by alternately stacking the hard magnetic films 20 and the soft magnetic films 21.

The lower electrode 8 and the upper electrode 7 are made of, for example, Cu
It is formed by a film. The hard magnetic film 20 and the hard magnetic film 21 of the read auxiliary layer and the memory layer that constitute the element 5 are, for example, a target of a Co material for magnetic material particles and an Al material to be an oxide.
There is a type in which Co magnetic material particles are dispersed in an Al ₂ O ₃ oxide (alumina layer) by performing a sputtering process in an oxygen mixed gas. In this case, it is the Co content that distinguishes between hard and soft. When a large amount of Co is contained, a hard magnetic layer is formed, and when a small amount of Co is contained, a soft magnetic layer is formed. The coercive force of the hard magnetic film 20 is 100 (O
e) Make sure that:

In this case, the hard magnetic film 20 and the hard magnetic film 2
In the forming step 1, for example, in a sputtering apparatus to which a target made of a Co material and an Al material is attached, the inside of the chamber is evacuated, and then A
The hard magnetic film 20 and the hard magnetic film having different coercive forces are controlled by introducing a predetermined pressure of an r-oxygen mixed gas and performing sputtering processing while separately controlling the power supplied to the target in the chamber. 21 can be formed. As described above, the magnetic laminated films having different coercive forces each have a higher specific resistance and a higher figure of merit than the multilayer GMR element, and are extremely excellent as cells for a vertical element structure. Further, since the dispersion film is easy to produce, it is suitable for producing a large-scale array.

As described above, by stacking a magnetic film in which magnetic material particles are dispersed in an oxide (alumina layer) on a block via a non-magnetic film, the specific resistance is extremely large and a sufficient figure of merit is obtained. Is obtained and the fabrication is easy, so that a magnetoresistive material for a magnetic memory suitable for fabricating a large-scale array can be obtained.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, an example for demonstrating the effect of the present invention will be described with respect to the obtained characteristics.

Example 1 First, a Co and Al target was attached to a sputtering apparatus, and a 50 × 50 (mm) glass substrate which had been washed beforehand was set in a chamber of the sputtering apparatus.
After the pressure in the chamber was reduced to 1 × 10 ⁻⁶ Torr or less, Ar gas having a purity of 99.9999% and purity of 99.9 were used.
A mixed gas containing 99% oxygen was introduced into the chamber, and the degree of vacuum in the chamber was adjusted to 7 × 10 ⁻³ Torr. And, as sputtering power, Co
100 W was supplied to the target and 40 W was supplied to the Al target, and a film having a thickness of 15 nm was formed as a first layer on a glass substrate. At this time, the film forming speed was 14.5 nm / sec.

After the formation of the first layer, 75 W was supplied to the Co target and 33 W to the Al target as sputtering power, and a film having a thickness of 35 nm was formed as the second layer on the first layer. . The deposition rate at this time is 1
1.1 nm / sec. The first layer and the second layer, which are the magnetic films thus obtained, had Co particles dispersed in alumina.

FIG. 2 shows the magnetoresistance characteristics of the magnetic film having a two-layer structure obtained in this manner. FIG. 2 shows the applied magnetic field (Oe) on the horizontal axis and the magnetoresistance ratio (MR ratio) on the vertical axis.
FIG. 7 is a graph showing the relationship between the two by taking (%). In FIG. 2, ◆ is a magnetoresistance curve when the magnetic field is increased from −200 (Oe) to the (+) side, and ■ is +
It is a magnetoresistive curve when decreasing from 200 (Oe) to the (-) side. The curve indicated by ◆ differs from the curve indicated by が in the applied magnetic field at which the MR ratio becomes an extreme value, and 0 (Oe)
Are located symmetrically on the + side and the-side with respect to the, so that a memory operation is possible.

The specific resistance of the two-layer magnetic film is 200 mΩ · cm, which is about 10,000 times larger than the material used for the multilayer GMR element.
It is suitable as a magnetoresistive material for a vertical memory.

The component composition of the film formed under the same conditions as described above is as follows: the first layer is Co: 65 at%, balance: alumina, the second layer is Co: 58 at%, balance: alumina. The coercive force of the first and second layers was 30 (Oe) and 1.5 (Oe), respectively. The component analysis was performed by ICP emission spectroscopy, and the magnetic measurement was performed by VSM.

In order to use the laminated film formed as described above as a memory element, first, as a lower electrode,
After a Cu film is formed on a glass substrate and the obtained Cu film is processed into an electrode shape, the first layer is Co: 65 atomic% and the balance is alumina on the lower electrode in the same manner as described above. A two-layer magnetic particle dispersion film in which the second layer is Co: 58 atomic% and the balance is alumina is formed, and this is 1 × 4 (μm).
Processed to the size of.

Furthermore, as an interlayer insulating film, a SiO ₂ film 4
After the film was formed to a thickness of 00 nm, a contact hole was formed in the SiO ₂ film in order to make contact between the storage unit and the upper electrode, and then a Cu film was formed
The film was formed with a thickness of nm. Then, this was processed into a predetermined shape to obtain an upper electrode.

Further, a film thickness of 10
A 0 nm interlayer insulating film is formed, and C is formed on the interlayer insulating film.
A u film was formed and processed to form a word line.

In the vertical device formed as described above,
After a pulse current having a peak current of 60 mA flows through the word line, a peak current of 5 m continues to flow through the word line.
When a pulse current of A was passed and 10 mA was passed between the upper and lower electrodes, a 0.3 mV response pulse was generated between the upper and lower electrodes.
By changing the direction of the current flowing through this first word line,
Since the direction of the pulse obtained later has changed, it can be seen that the information has been written.

Example 2 First, Co: 75 atomic%, Al: 20
Atomic% Co-Al alloy and Co: 80 atomic%, Al:
A target made of a 20 atomic% Co-Al alloy was attached, and a 50.times.
A glass substrate of 50 (mm) is set, and 1
After evacuating to ^10-6 Torr or less, the purity was 99.99.
A mixed gas obtained by mixing 99% by weight of Ar gas and 99.999% by weight of oxygen gas was introduced, and the degree of vacuum in the chamber was adjusted to 7 × 10 ⁻³ Torr. Then, 150 W is supplied to each of the targets, and the film thickness is 5 n.
m were alternately formed, and a total of 20 layers were laminated. At this time, the film forming speed was 14.5 nm / sec. In the two types of films obtained, the first layer was composed of 67 atomic% of Co and the balance was alumina, the second layer was composed of 56 atomic% of Co and the balance was alumina, and the coercive force of the film itself was each. 30 (O
e) 1.4 (Oe).

FIG. 3 shows the magnetoresistive characteristics of the thus obtained 20-layer multilayer magnetic film. As in the case of FIG. 2, the applied magnetic field at which the MR ratio has an extreme value is located on both sides of the boundary of 0 (Oe) and the curve is 0 (O).
It has a symmetrical shape with respect to e), and it can be seen that the obtained magnetic film is a magnetic film suitable for a magnetic memory having non-destructive read characteristics.

In the vertical device formed as described above,
After a pulse current with a peak current of 60 mA flows through the word line, a peak current of 5 mA continues through the word line.
When a pulse current of 10 mA flows between the upper and lower electrodes,
A response pulse of 0.65 mV was generated between the upper and lower electrodes. When the direction of the current flowing through the first word line is changed, the direction of the pulse obtained later changes, and it is understood that the bit is selected by the direction of the pulse and the information is written.

[0037]

As described in detail above, according to the present invention,
Since a vertical magnetic memory is formed by laminating magnetic films in which magnetic particles are dispersed in an oxide, the specific resistance is extremely high and the figure of merit is extremely high. In addition, the magnetic material and the vertical magnetic memory of the present invention are very effective for a large-scale array configuration because they are easy to make.

[Brief description of the drawings]

FIG. 1 is a diagram showing an element structure of a vertical cell.

FIG. 2 shows a magnetoresistance characteristic of a magnetic film according to the first embodiment of the present invention.

FIG. 3 shows a magnetoresistance characteristic of a magnetic film according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a horizontal cell structure.

FIG. 5 is a diagram showing an element structure of a horizontal cell.

6A is a schematic diagram illustrating a horizontal array, and FIG. 6B is a schematic diagram illustrating a vertical array.

FIG. 7 is a perspective view showing a vertical cell structure.

[Explanation of symbols]

1, reading element 3, 6; word line 4, 10; cell 7, upper electrode 8, lower electrode 9, insulating film 11, antiferromagnetic film 12, soft insulating film
13; non-magnetic film 20; hard magnetic film (dispersed film) 21; soft magnetic film (dispersed film)

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Takuo Aoshima 10-1 Nakazawacho, Hamamatsu-shi, Shizuoka Yamaha Corporation

Claims (2)

[Claims] 1. A magnetoresistive material for a vertical magnetic memory, comprising a film in which magnetic particles are dispersed in an oxide. 2. A vertical magnetic memory device comprising a magnetoresistive film in which magnetic particles are dispersed in an oxide and having different coercive forces.