JP2000076844A - Magnetic thin-film memory element and its recording and reproducing method as well as image video-recording and reproducing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic thin-film memory element which eliminates the demagnetizing field of a magnetic thin film, which increases the stability of a recording operation, whose information retention stability is high and which can be integrated highly. SOLUTION: A magnetoresistance film is formed in such a way that a first magnetic layer 1 which is circular cylinder-shaped or square tube-shaped and which has a low coercive force and a second magnetic layer 2 which is circular-cylinder-shaped or square tube-shaped and which has a high coercive force are laminated via a nonmagnetic layer 3. A magnetic thin-film memory element is featured in such a way that the magnetoresistance film whose easy axis of magnetization is counterclockwise or clockwise is provided, that a write selection line 4 which is installed at the magnetoresistance film via an insulator and which is composed of a good conductor is provided and that the magnetization direction of the first magnetic layer 1 or the second magnetic layer 2 is decided by a magnetic field generated when a current flows to the magnetization film in a direction perpendicular to its film face and by a magnetic field generated when a current flows to the write selection line 4. A recording and reproducing method is used for the magnetic thin-film memory element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic thin film memory element for recording information according to the direction of magnetization and reproducing the information by a magnetoresistance effect, a recording / reproducing method thereof, and an image recording / reproducing apparatus.

[0002]

2. Description of the Related Art Like a semiconductor memory, a magnetic thin film memory is a solid-state memory having no operation part, but does not lose information even if power is cut off, has an infinite number of rewrites, and records contents when radiation is incident. There is an advantage in comparison with a semiconductor memory, for example, there is no danger of disappearing. In particular, in recent years, a magnetic thin film memory using the giant magnetoresistance (GMR) effect has attracted attention because a large output can be obtained as compared with a conventionally proposed magnetic thin film memory using the anisotropic magnetoresistance effect. I have.

For example, the journal of the Japan Society of Applied Magnetics, VOL20, P
22 (1996), the hard magnetic film HM / nonmagnetic film NM / soft magnetic film SM / (nonmagnetic film NM) as shown in FIG.
A solid-state memory has been proposed in which a memory element is formed by laminating constituent elements a plurality of times. This memory element is provided with a sense line S joined to a metal conductor and a word line W insulated from the sense line S by an insulating film I. The sense line current generated by the word line current and the sense line current is generated. Information is written by a changing magnetic field.

More specifically, as shown in FIG. 11, a current I is applied to a word line W to generate a magnetic field in a different direction depending on the direction ID of the current. “0” and “1” are recorded. For example, as shown in FIG. 3A, a positive current is applied to generate a rightward magnetic field, and as shown in FIG. 3B, "1" is recorded on the hard magnetic film HM. As shown in (c), a negative current is passed to generate a leftward magnetic field, and "0" is recorded on the hard magnetic film HM as shown in (d) of FIG.

[0005] Information is read out as shown in FIG.
A current I smaller than the recording current is caused to flow through the word line W to cause only the magnetization reversal of the soft magnetic film SM, and the resistance change at that time is measured. Here, if the giant magnetoresistance effect is used, the resistance value differs between the case where the magnetization of the soft magnetic film SM and the hard magnetic film HM are parallel and the case where the magnetization is antiparallel. Can be determined. Specifically, when a positive to negative pulse as shown in FIG. 12A is applied, the soft magnetic film SM turns from right to left, and for the memory state “1”, the soft magnetic film SM in FIG. The resistance value changes from a small resistance value to a large resistance value as shown in FIG. 4C, and for the memory state “0”, the resistance value changes from a large resistance value as shown in FIG. Changes to a small resistance value. If the change in resistance is read in this manner, the information recorded on the hard magnetic film HM can be read regardless of the magnetization state of the soft magnetic film SM after recording, that is, nondestructive reading can be performed.

[0006]

However, in the magnetic thin film memory having the above structure, the demagnetizing field (self-demagnetizing field) generated inside the magnetic layer cannot be neglected as the area of the bit cell is reduced, and the magnetic thin film memory for recording and holding is not able to be stored. The magnetization direction of the layer is not determined in one direction and becomes unstable. Therefore, the magnetic thin film memory having the above-described structure has a disadvantage that it is difficult to store information as the bit cell is miniaturized, so that high integration is impossible. In addition, the magnetic field generated from the recording current is insufficient, so that recording becomes unstable and information storage stability is poor.

In view of the above, the present invention eliminates the demagnetizing field of the magnetic thin film, which is a problem when miniaturizing a bit cell, and furthermore, can generate a sufficient magnetic field to improve the stability of recording. It is another object of the present invention to provide a magnetic thin film memory element having high information storage stability and high integration, a recording / reproducing method thereof, and an image recording / reproducing apparatus.

[0008]

According to the present invention, there is provided a magnetic thin film memory element having a first magnetic layer having a low coercive force in a cylindrical or rectangular cylindrical shape and a first magnetic layer having a high coercive force in a cylindrical or rectangular cylindrical shape. A magnetoresistive film in which two magnetic layers are stacked with a nonmagnetic layer interposed therebetween, wherein the first magnetic layer and the second magnetic layer have a counterclockwise or clockwise easy axis; A magnetic field generated by passing a current through the magnetoresistive film in a direction perpendicular to the film surface, the magnetic field being generated by flowing a current through the magnetoresistive film via an insulator; The magnetic thin film memory element is characterized in that a magnetization direction of the first magnetic layer or the second magnetic layer is determined by a magnetic field generated by flowing the magnetic thin film.

Further, according to the recording method of the present invention, there is provided a magnetic field generated by flowing a current in a direction perpendicular to a film surface of a magnetoresistive film of a magnetic thin film memory element of the present invention, and a current flowing through a write selection line of the magnetic thin film memory element. A recording method for a magnetic thin film memory element, characterized in that a magnetization direction of a first magnetic layer or a second magnetic layer of the magnetic thin film memory element is determined by a magnetic field generated by flowing.

Further, according to the reproducing method of the present invention, a current is applied to the magnetoresistive film of the magnetic thin film memory element of the present invention in a direction perpendicular to the film surface and the resistance is measured to obtain the magnetization information of "0" and "1". Is a method of reproducing a magnetic thin film memory element, characterized by detecting

In the magnetic thin film memory element of the present invention,
Since the magnetic film has a closed magnetic path with a cylindrical or rectangular cylindrical structure, the demagnetizing field can be eliminated, and the magnetization information can be stably stored. Therefore, the cell width of one bit can be reduced, and a magnetic thin film memory with a high degree of integration can be realized. Further, since the leakage magnetic field does not leak to the adjacent cells, it is possible to more stably record and reproduce information.

Furthermore, if this memory element is formed by stacking multiple layers, the degree of integration per unit area is dramatically improved, so that a high-capacity nonvolatile solid-state memory with high recording stability can be realized. Become.

Further, the image recording apparatus of the present invention has a lens group for forming an image of a subject on a photoelectric conversion element, a photoelectric conversion element for converting the formed image into an electric signal, and records the electric signal. At least a recording medium is used, and a magnetic thin film memory in which the above-mentioned memory elements are stacked in multiple layers is used as the recording medium.

According to the image reproducing apparatus of the present invention, an image is stored as an electric signal in a magnetic thin film memory in which the above-mentioned memory elements are multiplexed, and the electric signal is read out from the magnetic thin film memory, and the electric signal is converted into an image. To display.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

FIG. 1 is a diagram showing an example of the magnetic thin film memory element of the present invention. In the figure, 1 is a first magnetic layer, 2
Indicates a second magnetic layer, 3 indicates a non-magnetic layer, and arrows indicate magnetization directions in the respective magnetic layers. The first magnetic layer and the second magnetic layer are cylindrical, and their magnetization is annularly oriented along the cylinder. Therefore, unlike the conventional medium (FIGS. 10 to 12), the magnetic pole does not come out to the end face, and stable magnetization can be stored. In the vicinity of the cylindrical magnetic film, a write selection line 4 is provided via an insulator (not shown).

The magnetic thin film memory element of the present invention exhibits a low resistance value when the magnetizations of the first magnetic layer and the second magnetic layer are parallel,
It shows a high resistance value when antiparallel. Therefore, the resistance value of the memory element differs depending on the magnetization direction of the first magnetic layer and the second magnetic layer, and the recorded magnetization information can be read.

The first magnetic layer and the second magnetic layer are not limited to the cylindrical type and may have a closed magnetic circuit structure. For example, a square cylindrical type, for example, a square cylindrical type shown in FIG. May be. However, the cylindrical type is the most preferable because the maximum value of the curvature in the magnetization direction is the smallest.

The magnetization information of "0" and "1" is recorded according to whether the magnetization direction of the first magnetic layer or the second magnetic layer is clockwise or counterclockwise. Recording of information is mainly performed by flowing a current in a direction perpendicular to the film surface and inverting the magnetization of the first magnetic layer or the second magnetic layer by the generated magnetic field. For example, in FIG.
When a current is passed through the magnetic layer, a clockwise magnetic field is generated when viewed from above, so that the second magnetic layer can have a clockwise magnetization direction.

In the magnetic thin film memory element of the present invention,
Along with the current perpendicular to the film surface, a current is applied to the write selection line 4 to generate a magnetic field. When a current flows through the write selection line 4, a magnetic field is generated perpendicular to the film surface as shown in FIG. In FIG. 2, reference numeral 400 denotes a symbol indicating the direction of the current. Since this magnetic field is perpendicular to the magnetization direction of the memory element, the magnetization direction cannot be determined. However, the magnetic field has an effect of facilitating the magnetization reversal, and the current perpendicular to the film surface can be reduced.

Whether the first magnetic layer is inverted or the second magnetic layer is inverted during recording depends on the type of medium.

The first type has a structure of “memory layer (first magnetic layer) / nonmagnetic layer / pinned layer (second magnetic layer)”. This means that the first magnetic layer is always kept constant in the memory layer in which the magnetization information is stored, and the second magnetic layer is always kept constant in any state of storage, recording, and reproduction without depending on the magnetization direction. When a pinned layer is provided, recording is performed by reversing the magnetization of the first magnetic layer. The reproduction is performed by detecting the absolute value of the resistance value without performing the magnetization reversal of the magnetic layer, as described later.

The second type is a “detection layer (first magnetic layer)
/ Non-magnetic layer / memory layer (second magnetic layer) ". This is a case where the first magnetic layer is a detection layer that is inverted for relative detection at the time of reading, and the second magnetic layer is a memory layer that stores magnetization information. Recording is performed by reversing the magnetization of the second magnetic layer. Do it.

In any of the above cases, the first magnetic layer has a low coercive force, and the second magnetic layer has a higher coercive force than the first magnetic layer.

The write selection line may be provided on either the left or right side of the magnetic film, and may be provided on both sides of the magnetic film as shown in FIG. When a reverse current is applied to the write selection lines 41 and 42, the vertical magnetic field applied to the magnetic film can be increased, and the magnetization can be more easily reversed. In addition, the “detection layer (first
Magnetic layer) / non-magnetic layer / memory layer (second magnetic layer), a current flows through only one write select line during reproduction, and a current flows through both write select lines during recording. The current margin at the time can be expanded, and a stable operation without erroneous recording at the time of reproduction can be performed.

FIG. 4 is a view showing another example of the magnetic thin film memory element of the present invention. In FIG. 4, a write decision line 5 made of a conductor surrounded by an insulator 6 is provided at the center of the first magnetic layer 1 and the second magnetic layer 2 as shown in detail in FIG. Is provided. The write decision line 5 is used to reverse the magnetization by flowing a current at the time of recording, and has a higher conductivity than the magnetic layer. The insulator 6 is provided to prevent the write decision line 5 from making electrical contact with the magnetic layer. However, when the thickness of the insulator 5 is large, the distance between the write decision line 5 and the magnetic layer becomes long and the magnetic field that can be applied to the magnetic layer becomes small. Further, one write selection line 4 may be provided as shown in FIG. 4A, and both the write selection line 41 and the write selection line 42 may be provided as shown in FIG.

In the structure shown in FIG. 4, since no current flows in the magnetic layer during recording as compared with the structure of FIG. 1, the wiring resistance is reduced, and the power consumption and the recording speed are excellent. Also,
At the time of reproduction, the resistance between the first magnetic layer and the second magnetic layer may be measured so that a current for sensing does not flow through the write decision line.

In the memory element of the present invention, the write selection line 4
Is provided, the memory elements can be stacked on top of each other to form a multiplex structure. For example, as shown in FIG. 6, two magnetoresistive films including a first magnetic layer, a nonmagnetic layer, and a second magnetic layer are stacked to form a series structure. When recording on the magnetoresistive film 10, the write select line 60 and the write decision line 5 for determining the magnetization direction are used, and when recording on the magnetoresistive film 11, the write select line 61 and the write decision line 5 are used. In this case, since a large synthetic magnetic field is applied only to a specific film, 2-bit recording can be performed with a 1-bit cell area. Between the memory element 10 and the memory element 11,
The conductor 20 is provided as needed to prevent erroneous recording.

In reproduction, a current is applied to conductors provided on both sides of the memory elements 10 and 11 to detect a resistance value. At this time, the recording information of the specific cell can be detected by reversing the magnetization of the cell to be read using the write selection line 60 or 61 and observing the change in the resistance value. That is, in the case of a multi-layer structure, it is desirable to use the above-described “detection layer (first magnetic layer) / non-magnetic layer / memory layer (second magnetic layer)”.

The memory shown in FIG. 7 is obtained by further expanding the above-mentioned technical concept and arranging three memory elements connected in series in four rows. In this case, the write selection lines 4 are provided on both sides, and can also be used for recording and reproduction of the memory cells on both sides. FIG. 8 shows the memory of FIG. 7 viewed from above.

Although FIG. 7 shows a case where four memory elements are stacked, the number of memory elements is not limited to four, but may be two or more and 256 or less. However, if the number of laminations is excessively increased, problems such as a decrease in signal output and loss of flatness of the film occur.
The number is preferably 16 or more and 16 or less.

FIG. 9 shows the magnetoresistive film 10 and the write selection line 4.
Is a memory having a semiconductor hybrid structure in which the memory element of the present invention is connected to a transistor. The four memory elements 10 are stacked, and the lower end is connected to the drain electrode 503 of the semiconductor transistor 500, and the upper end is connected to the electrode 504 of the constant voltage VDD. Although not shown, a large number of transistors and memories having the same structure are arranged in a large number in a plane, so that several M bits, several G
A large-capacity memory of more than one bit can be manufactured.

This semiconductor element comprises a gate electrode 502 and a source electrode 501, and a specific memory element can be selected from many elements. After the selection, it is possible to record and reproduce information of a specific memory element from the multiplexed elements by the method described above. The reproduced signal is taken out from the source electrode and amplified by the sense amplifier.

At the time of recording, it is desirable to generate a magnetic field of at least 5 Oe. More preferably, 10 O
It is desirable to generate a magnetic field of e or more. This is because if the magnetic field is too small, it is necessary to reduce the coercive force of the magnetic thin film memory element, and it becomes difficult to stably hold recorded information. In order to generate a large magnetic field, a large amount of current only needs to flow, but if the current density exceeds the limit current density of the wiring material,
When electromigration occurs, the wiring is easily broken, and when the current value increases, the power consumption of the device increases.

Among the wiring materials used in semiconductor devices, the tungsten wire, which is a material having a relatively large limit current density, has a limit current density of 20 mA / μm ² , and suppresses an increase in power consumption, device heat generation, and the like. A desirable current is about 1 mA.

In order to generate a magnetic field of 5 Oe or more required for recording, the current path through which the recording current flows must be at least 0.
The length of the current path may be 05 μm or more, and the longer the current path length, the wider the range of the radius of the current path that can be recorded.

Therefore, in order to generate a necessary recording magnetic field of 5 Oe, the length of the recording current path needs to be 0.05 μm. Preferably 0.1 μm or more, more preferably 0.15 μm or more, more preferably 0.20 μm
The above is good.

On the other hand, if the length of the current path is too long, the film thickness becomes large, so that it takes a long time to form the film.
In addition, the current path may not be perpendicular to the substrate surface and may be inclined, thereby causing a malfunction such as erroneous recording in an adjacent memory element. Therefore, the length of the current path is 2 μm or less, preferably 1 μm or less, and more preferably 0.1 μm or less.
5 μm or less is preferred.

In the magnetoresistive film of the present invention, a CPP (Current Perpendicular) in which a current at the time of reproduction flows perpendicular to the film surface.
to the film Plane) -Magneto-Resistance (MR) effect is used. This CPP-MR is a CIP (Current In-plane to the film Plane) -M which allows a current to flow parallel to the film surface.
Since the probability of conduction electrons crossing the interface increases more than the R effect, the signal detection sensitivity for obtaining a large resistance change rate can be increased.

As a film structure, a spin tunnel film structure and a spin scattering film structure can be adopted. The present invention can be applied to any of the above-described configurations of “memory layer / nonmagnetic layer / pin layer” and “detection layer / nonmagnetic layer / memory layer”.
However, in the spin tunnel film configuration and the spin scattering film configuration,
It is desirable to use a spin tunneling film configuration. This is because a large magnetoresistance (M
This is because the R) ratio can be obtained, and the resistance value can be increased to 1 kΩ or more, and the semiconductor switching element is hardly affected by the variation of the on-resistance (about 1 kΩ).

One example of the magnetoresistive film used in the present invention has a spin tunnel film configuration. The magnetoresistance effect due to the spin tunneling is caused by the first magnetic layer /
It has a non-magnetic layer / second magnetic layer structure, and a thin insulating layer is used for the non-magnetic layer. Then, when a current is caused to flow perpendicularly to the film surface during reproduction, a tunnel phenomenon of electrons occurs from the first magnetic layer to the second magnetic layer.

In the spin tunneling type magnetic thin film memory element of the present invention, the conduction state of the ferromagnetic metal causes spin polarization, so that the electron states of the upward spin and the downward spin on the Fermi surface are different. When a ferromagnetic tunnel junction composed of a ferromagnetic material, an insulator, and a ferromagnetic material is made using such a ferromagnetic metal, the conduction electrons tunnel while keeping their spins. This changes the tunnel probability, which appears as a change in tunnel resistance. Thereby, the first magnetic layer and the second magnetic layer
When the magnetizations of the magnetic layers are parallel, the resistance is small, and when the magnetizations of the first magnetic layer and the second magnetic layer are antiparallel, the resistance is large.
The larger the difference between the state densities of the upward spin and the downward spin, the greater the resistance value, and a greater reproduction signal can be obtained. Therefore, the first magnetic layer and the second magnetic layer should be made of a magnetic material having a high spin polarizability. Is desirable.

More specifically, as the first magnetic layer and the second magnetic layer, Fe having a large amount of vertical spin polarization on the Fermi surface may be selected, and Co may be selected as the second component. In particular, it is desirable to use a material containing Fe, Co, or Ni as a main component. Preferably, F
e, Co, FeCo, NiFe, NiFeCo and the like are preferable. When the element composition of NiFe is Ni _x Fe _100-x , x is desirably 0 or more and 82 or less. More specifically,
Fe, Co, Ni ₇₂ Fe ₂₈ , Ni ₅₁ Fe ₄₉ , Ni ₄₂ Fe
₅₈ , Ni ₂₅ Fe ₇₅ , Ni ₉ Fe _{91 and the} like.

Further, the first magnetic layer is more preferably made of NiFe, NiFeCo, Fe or the like in order to reduce coercive force. Further, the second magnetic layer is used to increase the coercive force.
A material containing Co as a main component is desirable.

The thicknesses of the first magnetic layer and the second magnetic layer of the magnetic thin film memory element of the present invention exceed 100 ° and 5000 °.
It is desirable that:

First, when an oxide is used for the non-magnetic layer, the magnetism at the interface of the magnetic layer on the non-magnetic layer side is weakened by the effect of the oxide, and this effect is large when the film thickness is small. It is.

Second, the aluminum oxide nonmagnetic layer is
When l is formed and then oxidized by introducing oxygen, aluminum is left for several tens of degrees, and this influence is increased when the magnetic layer is less than 100 degrees, and appropriate memory characteristics cannot be obtained. It is.

Third, in particular, when the memory element is miniaturized to submicron, the memory holding performance of the first magnetic layer and the function of holding the constant magnetization of the second magnetic layer deteriorate. On the other hand, if the thickness is too large, there is a problem that the resistance value of the cell becomes too large. Therefore, the thickness is preferably 5000 ° or less, more preferably 1000 ° or less.

As described above, since the magnetoresistive memory element of the present invention uses the magnetoresistance effect by spin tunneling, the nonmagnetic layer may be an insulating layer for electrons to hold spins and tunnel. The entire non-magnetic layer may be an insulating layer, or a part thereof may be an insulating layer. The magnetoresistive effect can be further enhanced by forming a part of the insulating layer and minimizing its thickness. As an example of forming an oxidized layer by oxidizing a nonmagnetic metal film, there is an example of forming an Al ₂ O ₃ layer by oxidizing a part of an Al film in air.
The nonmagnetic layer is made of an insulator, and is preferably made of aluminum oxide AlOx, aluminum nitride AlNx, silicon oxide SiOx, or silicon nitride SiNx. NiOx may be the main component. This is because in order for spin tunneling to occur, it is necessary that an appropriate potential barrier exists for the energies of conduction electrons in the first magnetic layer and the second magnetic layer. Is relatively easy and is advantageous in production.

The nonmagnetic layer is a uniform layer having a thickness of about several tens of degrees, and the thickness of the insulating portion thereof is desirably 5 to 30 degrees. This is because if it is less than 5 °, the first magnetic layer and the second magnetic layer may be electrically short-circuited, and if it is more than 30 °, electron tunneling is less likely to occur. . Further, it is desirable that the angle be 4 ° or more and 25 ° or less. More preferably, the angle is 6 ° or more and 18 ° or less.

The second example of the magnetoresistive film used in the present invention has a spin scattering film configuration, and is characterized in that a magnetoresistive effect is generated by spin-dependent scattering. The magnetoresistive effect due to the spin-dependent scattering has a structure of a first magnetic layer / nonmagnetic layer / second magnetic layer, and a metal layer made of a good conductor is used for the nonmagnetic layer. The magnetoresistance effect due to this spin-dependent scattering is derived from the fact that the scattering of conduction electrons differs greatly depending on the spin. That is, conduction electrons having spins in the same direction as the magnetization are not scattered so much that the resistance is small, but conduction electrons having spins in the opposite direction to the magnetization have a large resistance due to scattering. Therefore, when the magnetizations of the first magnetic layer and the second magnetic layer are in opposite directions, the resistance value is larger than that in the case of the same direction.

The characteristics of the first magnetic layer, the second magnetic layer, and the nonmagnetic layer in this case are shown. The first magnetic layer is provided to form an annular loop with the second magnetic layer and to read out the magnetization information stored in the second magnetic layer using the giant magnetoresistance effect. It is desirable that the first magnetic layer be used mainly with Ni, Fe, and Co, or as an amorphous alloy mainly containing Co and Fe. For example, it is made of a magnetic film of NiFe, NiFeCo, FeCo, CoFeB or the like. The elemental composition of NiFe is Ni _x Fe
_{When 100-x} is set, x is desirably 35 or more and 86 or less.
The element composition of NiFeCo is Ni _x (Fe _100-y C
o _y ) If _100-x , x is 10 or more and 70 or less, and y is 3
It is desirable that y is from 0 to 90, and y is desirably from 60 to 85. Further, Co ₈₄ Fe ₉ B ₇ , Co ₇₂ Fe ₈ B
An amorphous magnetic material such as CoFeB having a composition such as ₂₀ may be used.

The second magnetic layer is provided mainly for the purpose of storing magnetization information, and the direction of magnetization is determined according to the information of "0" and "1". Like the first magnetic layer, the second magnetic layer needs to efficiently generate the giant magnetoresistance effect and to be able to stably maintain the magnetization state. The second magnetic layer is made of a magnetic layer containing Fe and Co as main components, for example, a magnetic film of Fe, FeCo, Co or the like. Further, an additional element such as Pt may be added. Co to F
When e is added, the coercive force decreases, and when Pt is added, the coercive force increases.
_The coercive force may be controlled by adjusting the element compositions x and _y as _100-xy F _x Pty. Similarly, the coercive force of the first magnetic layer can be adjusted by the composition ratio of Fe and Co and the amount of additional elements such as Pt.

The thickness of the first magnetic layer may be set so that the scattering type giant magnetoresistance effect is efficiently generated. CP
In P-MR, the distance that can move while preserving the spin direction, that is, the spin diffusion length, is an important factor. Specifically, the first
If the thickness of the magnetic layer is significantly larger than the mean free path of electrons, phonon scattering is exerted and the effect is reduced. Therefore, it is desirable that the thickness be at least 200 ° or less. More preferably, the angle is 150 ° or less. However, if it is too thin, the resistance value of the cell becomes small and the output of the reproduced signal decreases,
In addition, since magnetization cannot be maintained, the angle is preferably 20 ° or more, and more preferably 80 ° or more.

As in the case of the first magnetic layer, the thickness of the second magnetic layer is set so that the scattering type giant magnetoresistive effect can be efficiently generated. More preferably, the angle is 150 ° or less.
However, if the thickness is too small, the memory retention performance is degraded, the resistance of the cell, which reduces the output of the reproduced signal, becomes small, and the magnetization cannot be retained. Therefore, the thickness is preferably 20 ° or more, and more preferably 80 ° or more.

The non-magnetic layer is made of a good conductor.
When Cu is used as the main component, since the Fermi energy level and the magnetic layer are close to each other and the adhesion is good, resistance is easily generated at the interface when the magnetization direction changes, which is convenient for obtaining a large magnetoresistance ratio. The thickness of the nonmagnetic layer is 5 は.
It is desirable that the angle be equal to or more than 60 ° or less.

Between the first magnetic layer and the non-magnetic layer, or
When a magnetic layer containing Co as a main component is provided between the magnetic layer and the non-magnetic layer, or between the first magnetic layer and the non-magnetic layer, and between the second magnetic layer and the non-magnetic layer, the magnetoresistance ratio becomes lower. This is desirable because a higher S / N ratio can be obtained. In this case, the thickness of the layer containing Co as a main component is preferably 20 A or less. Further, in order to improve S / N, {first magnetic layer /
The nonmagnetic layer / second magnetic layer / nonmagnetic layer｝ may be formed as one unit, and the units may be stacked. The larger the number of stacked layers, the higher the MR ratio, which is preferable. However, if the number is too large, the MR magnetic layer becomes thick and requires a large amount of current. For this reason, the number of laminations is 40 or less, more preferably 3 to 2
It is preferable to provide about 0 sets.

[0058] Control of the coercive force, for example, coercive force becomes smaller as the addition of Fe to Co, since the coercive force is increased upon addition of Pt, the elemental composition x and y as for example Co _100-xy Fe _x Pt _y The coercive force may be controlled by adjustment. Since the coercive force can be increased by increasing the substrate temperature during film formation, another method of controlling the coercive force may be to adjust the substrate temperature during film formation. This method may be combined with the above-described method of adjusting the composition of the ferromagnetic thin film.

In the magnetic thin film memory element of the present invention, an antiferromagnetic layer is provided in contact with the surface of the second magnetic layer opposite to the nonmagnetic layer, and the antiferromagnetic layer and the second magnetic layer are exchange-coupled. Thus, the magnetization of the second magnetic layer may be fixed. The exchange coupling with the antiferromagnetic layer makes it possible to increase the coercive force of the second magnetic layer. In this case, since the same material can be used for the first magnetic layer and the second magnetic layer, there is no need to sacrifice the MR ratio in order to increase the coercive force, and the range of material selection can be widened. Examples of the antiferromagnetic layer include nickel oxide NiO, iron manganese FeMn, and cobalt oxide CoO.

[0060]

The present invention will be described in more detail with reference to the following examples.

<Example 1> A magnetic thin film memory element having the structure shown in FIG. 6 (two laminations) was manufactured. Here, the material of the first magnetic layer is Ni ₈₀ Fe ₂₀ , the thickness is 25 nm, and the coercive force is 10 O.
e. The material of the nonmagnetic layer was Al ₂ O ₃ and the thickness was 5 nm. The material of the second magnetic layer was Co, the film thickness was 25 nm, and the coercive force was 20 Oe. The material of the write selection line was Al.

For this magnetic thin film memory element, 25 mA is applied to each of the write selection lines beside the two memory elements.
And "1" and "0" were recorded in each memory element according to the direction of the current.

In order to reproduce the recorded magnetic thin film memory element, a current of 12 mA is applied to each write select line in the positive and negative directions, and only the first magnetic layer is inverted to measure the resistance change of the magnetoresistive film portion. did. As a result, a resistance change corresponding to the recorded information was obtained, and the information could be accurately reproduced.

The magnetic thin film memory element of the present invention described above can be used as a recording medium of an image recording / reproducing apparatus. FIG. 14 is a block diagram showing a configuration example of an image recording / reproducing apparatus using the solid-state memory shown in FIG. 9 formed by laminating magnetic thin film memory elements as a recording medium. When recording, an image is formed on an image sensor 90 by a lens system, a signal from the image sensor is converted into a digital signal by an A / D converter 91, and a recording medium 9 using a solid-state memory using a ferromagnetic material is used.
Write to 2.

For reproduction, the digital signal from the recording medium 92 is converted into an analog signal by the D / A converter 93,
It is displayed on the display 94 by a normal processing circuit.

<Embodiment 2> An embodiment of the image recording / reproducing apparatus shown in FIG. 14 will be described below using the solid-state memory shown in FIG. 9 as a recording medium.

The solid-state memory shown in FIG. 9 can have a high degree of integration. Therefore, when the solid-state memory is manufactured with a 0.16 μm design rule using a KrF excimer laser capable of manufacturing a 1-Gbit DRAM, a 4-Gbit capacity can be integrated into one chip. Degree can be achieved. By mounting 8 chips on a PCMCIA type 2 memory card, 4Gby
A solid memory card of te capacity can be made. The number of 8 chips to be mounted is a practical upper limit in consideration of the size, power consumption, and cost of a card that can be used as a portable device. When compressed by MPEG2, the reception quality image of the current television can be recorded at about 5 Mbps.

The writing time of the data to be transferred to the card is
Since the spin inversion time is 2 nsec, the entire chip becomes 100 ns or less even when the access time of the selection transistor is taken into consideration. Therefore, the recording time on these cards is 1.8 hours. Therefore, in the image recording device using the solid-state memory constituted by the magnetoresistive film of the present invention as a recording medium, it can be sufficiently used as a moving image recording medium.

Table 1 (comparison table showing the capacity and recording time of the giant magnetoresistive memory (GNR memory) used in the image recording apparatus of the present invention and the flash memory and ferroelectric memory as comparative examples) is summarized. Shown. GMR in the table
Shows a GMR memory having the configuration shown in FIG.

[0070]

[Table 1]

Note that recent image recording devices, particularly portable video cameras, have been reduced in device size to near the palm size. Therefore, the recording medium is PCMCIA.
Preferably, the size is about half that of type 2.

At this time, since the recording capacity is reduced to half,
The device of the type in which the GMR films shown in Examples 4 and 5 are multiply stacked can make use of the features of the present invention,
More preferred.

Although the case where a moving image is recorded has been described above, the same applies to a still image requiring a large capacity.

The memory used in the image recording apparatus of the present invention
Since a semiconductor switching element is provided, random access is possible even when the degree of integration is increased. In addition, since there is no physically moving solid head or the like, power consumption can be suppressed, and there is no deterioration due to wear, and the device is small and lightweight. Also, since information is stored by spin, recording and reproduction can be performed almost infinitely repeatedly.

Next, the rewriting durability required for the nonvolatile memory will be described below.

In a GMR memory, information is rewritten as the spins of the atoms of the magnetic material are reversed, so that the number of possible rewrites is almost infinite at 10 ¹⁵ or more. For example, assuming that the access time for rewriting is 200 seconds, the transfer speed is 5
When rewriting the data of “0” and “1” at Mbps is repeated, 10 ¹⁵ times corresponds to continuous rewriting for about 6 years or more. Therefore, with the image recording device of the present invention, it is possible to repeatedly record substantially infinite times.

Table 2 (comparison table showing the rewriting durability of the giant magnetoresistive memory (GMR memory) used in the image recording apparatus of the present invention and the flash memory and ferroelectric memory as comparative examples) is summarized. Show. GMR in the table
Shows a GMR memory having the configuration shown in FIG.

[0078]

[Table 2]

Hereinafter, Comparative Examples 1 and 2 shown in Tables 1 and 2 will be described.

<Comparative Example 1> The same recording as in Example 2 was performed using a flash memory. In a flash memory, high integration can be performed up to 256 Mbit. However, electrons pass through the tunnel film and inject electrons into the loading gate. When storing information, the tunnel film needs to be thick so that the electrons do not escape. Therefore, it takes time to pass through the thick tunnel film, and as a result, the writing speed is 1 msec per chip, and the recording speed is considerably low. Therefore, recording of a moving image was impossible.

The rewriting durability of the flash memory will be described below. The flash memory as described above, for electronic thick tunneling film during recording passes, rewriting frequency is degraded at ¹⁰⁶ or less. As in the second embodiment, the transfer speed is 5 Mbps with the access time for rewriting set to 200 seconds.
In "0", the repeated rewriting of data of "1", and is 10 ⁶ times, corresponding to that of rewriting a continuous 0.2 seconds. Therefore, recording cannot be performed with high durability in a flash memory.

<Comparative Example 2> The same recording as in Example 2 was performed using a ferroelectric memory. The ferroelectric memory can record at a relatively high speed, but there is a big problem in the degree of integration in a class exceeding 4 Mbit. Since a high-temperature heat treatment is necessary because of a crystalline material, it may be difficult to form a capacitance portion. In the case of recording on a 4 Mbyte card, only 7 seconds can be recorded, and practical use is difficult.

The rewriting durability of the ferroelectric memory will be described below. As described above, in a ferroelectric memory, the position of a specific atom moves in a crystal lattice, and information is recorded by polarization at that time. Therefore, when repeatedly recorded,
Gradually, the atomic position is stably held at an intermediate position, the amount of polarization decreases, and the frequency of rewriting becomes 1
Deterioration occurs below 0 ¹¹ .

As in Embodiment 2, "0" and "1" at a transfer rate of 5 Mbps with a rewrite access time of 200 seconds.
When you do repeatedly rewriting of the data, the 10 ¹¹ times,
This corresponds to rewriting continuously for 5 hours and 36 minutes.
Therefore, recording cannot be performed with high durability in the ferroelectric memory.

[0085]

As described above, according to the present invention,
Eliminates the demagnetizing field of the magnetic thin film, which is a problem when miniaturizing bit cells, and furthermore, it is possible to generate a sufficient magnetic field to improve the stability of recording, and the high stability of information storage and high integration It is possible to provide a magnetic thin film memory element, a recording and reproducing method thereof, and an image recording and reproducing apparatus.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a magnetic thin film memory element which is one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a magnetic thin film memory element which is one embodiment of the present invention.

FIG. 3 is a cross-sectional view of a magnetic thin film memory element which is one embodiment of the present invention.

FIG. 4 is a cross-sectional view of a magnetic thin film memory element which is one embodiment of the present invention.

FIG. 5 is a view showing the cylindrical magnetic film of FIG. 4;

FIG. 6 is a cross-sectional view of a magnetic thin film memory according to one embodiment of the present invention.

FIG. 7 is a cross-sectional view of a magnetic thin film memory according to one embodiment of the present invention.

FIG. 8 is a view of FIG. 7 as viewed from above.

FIG. 9 is a cross-sectional view of a magnetic thin film memory element which is one embodiment of the present invention.

FIG. 10 is a sectional view of a magnetic thin film showing a conventional magnetic thin film memory using a giant magnetoresistance effect.

FIG. 11 is an explanatory diagram showing a recording operation of a conventional magnetic thin film memory using the giant magnetoresistance effect.

FIG. 12 is an explanatory diagram showing a reproducing operation of a conventional magnetic thin film memory using a giant magnetoresistance effect.

FIG. 13 is an explanatory diagram of a magnetic thin film memory element which is one embodiment of the present invention.

FIG. 14 is a block diagram showing an embodiment of an image recording / reproducing apparatus using the magnetic thin film memory element of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st magnetic layer 2 2nd magnetic layer 3 Non-magnetic layer 41,42,60,61 Write selection line 400 Current direction 5 Write decision line 6 Insulator 10,11 Magnetoresistance film 20 Good conductor 90 Image sensor 91 A / D Converter 92 Recording medium 93 D / A converter 94 Display 100 Magnetoresistive element, write decision line, etc. viewed from above 500 Semiconductor transistor 501 Source electrode 502 Gate electrode 503 Drain electrode 504 VDD electrode

Claims (12)

[Claims] A first magnetic layer having a low coercive force of a cylindrical or rectangular cylindrical type and a second magnetic layer having a high coercive force of a cylindrical or rectangular cylindrical type are laminated via a non-magnetic layer. Wherein the first magnetic layer and the second magnetic layer have an easy axis counterclockwise or counterclockwise, and a good conductor provided on the magnetoresistive film via an insulator. A magnetic field generated when a current flows through the magnetoresistive film in a direction perpendicular to the film surface, and a magnetic field generated when a current flows through the write selection line. A magnetic thin-film memory device, wherein the magnetization direction of the second magnetic layer is determined. 2. The magnetic thin film memory element according to claim 1, wherein a plurality of said write selection lines are provided on a side surface of said magnetoresistive film. 3. In order to allow a current to flow through the magnetoresistive film in a direction perpendicular to the film surface, the first magnetic layer is surrounded by an insulator at the center of the first magnetic layer and the second magnetic layer. 2. The magnetic thin-film memory element according to claim 1, further comprising a write decision line made of a good conductor having a higher conductivity than the second magnetic layer. 4. The first magnetic layer is a memory layer in which magnetization information is stored, and the second magnetic layer is always kept constant during storage, recording, and reproduction. 2. The magnetic thin film memory device according to claim 1, wherein the magnetic thin film memory device is a pin layer. 5. The first magnetic layer is a detection layer for inverting the first magnetic layer for relative detection at the time of reading, and
2. The magnetic thin film memory device according to claim 1, wherein the second magnetic layer is a memory layer in which magnetization information is stored. 6. The magnetic thin film memory device according to claim 5,
A magnetic thin film memory in which two or more layers are stacked on a substrate. 7. The magnetic thin-film memory element according to claim 1,
A magnetic thin-film memory, which is arranged in a matrix on a substrate, wherein an end of a magnetoresistive film of the magnetic thin-film memory element is electrically connected to a semiconductor element including a transistor. 8. A magnetic field generated by applying a current to the magnetoresistive film of the magnetic thin film memory element according to claim 1 in a direction perpendicular to the film surface, and a magnetic field generated by applying a current to a write selection line of the magnetic thin film memory element. Determining the magnetization direction of the first magnetic layer or the second magnetic layer of the magnetic thin film memory element. 9. A method for detecting magnetization information of “0” and “1” by applying a current to a magnetoresistive film of the magnetic thin film memory device according to claim 1 and measuring a resistance in a direction perpendicular to the film surface. A method for reproducing a magnetic thin film memory element, comprising: 10. A magnetic field generated by applying a current to a write selection line of the magnetic thin film memory element to invert a magnetization direction of a first magnetic layer of the magnetic thin film memory element, and to change a resistance of the magnetoresistive film at that time. 10. The method according to claim 9, wherein the direction of magnetization of the second magnetic layer is detected by a change in the value. 11. An image comprising at least a lens group that forms an image of a subject on a photoelectric conversion element, a photoelectric conversion element that converts the formed image into an electric signal, and a recording medium that records the electric signal. 7. An image recording apparatus, wherein the recording medium comprises the magnetic thin film memory according to claim 6. 12. An image reproducing apparatus for reading an electric signal from a recording medium storing an image as an electric signal and displaying the electric signal as an image, wherein the recording medium comprises the magnetic thin film memory according to claim 6. An image reproducing apparatus characterized by the above-mentioned.