JP3333670B2 - Magnetic thin film memory - Google Patents

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 for storing information according to a difference in magnetization direction, and more particularly to a magnetic thin film memory for reproducing magnetically recorded information by a magnetic tunneling effect.

[0002]

2. Description of the Related Art At present, nonvolatile memories used in information processing devices include flash EEPROMs and hard disk devices. In these non-volatile memories, shortening the write time and the read time has become an important issue as the information processing device speeds up.

As a technique effective in increasing the speed of such a nonvolatile memory, a magnetic thin film memory element utilizing a giant magnetoresistance effect (GMR) is known. This giant magnetoresistance effect shows a magnetoresistance change rate exceeding the anisotropic magnetoresistance effect (AMR). Unlike AMR, the resistance value does not depend on the angle between the current and the magnetic field, and the axis of easy magnetization is parallel. When the magnetization directions of the two magnetic layers are the same, the resistance value becomes minimum, and when the magnetization directions are opposite (180 ° reverse direction), the resistance becomes maximum.

In a nonvolatile memory utilizing the giant magnetoresistance effect, information is stored according to the magnetization directions of two magnetic layers opposed to each other with a nonmagnetic layer interposed therebetween. Such non-volatile memories utilizing the giant magnetoresistance effect include a spin valve type in which information is written in a magnetic layer whose magnetization direction changes only by applying a weak magnetic field, and a magnetic layer whose magnetization direction does not change unless a strong magnetic field is applied. There is an inductive ferri type that writes information to a computer.

[Spin Valve Type] As a type of storing information in a magnetic layer whose magnetization direction changes only by applying a weak magnetic field, there is a type called a spin valve. The spin valve is a multilayer film in which a magnetic layer having a fixed magnetization direction (hereinafter, referred to as a pinned layer) and a magnetic layer whose magnetization direction is freely changed by an external magnetic field (hereinafter, referred to as a free layer) are combined. In this case, the resistance value is different between the case where the magnetization direction of free and the direction of magnetization are the same and the case where the magnetization direction is the opposite direction. For example, in Phys. Rev. B, 43, 1297 (1991), the magnetic layer NiFe /
An example of a magnetic thin film in which a nonmagnetic layer Cu / magnetic layer NiFe / antiferromagnetic layer FeMn is laminated is shown. In this magnetic thin film, the magnetization direction of the magnetic layer (pinned layer) adjacent to the antiferromagnetic layer is fixed by exchange anisotropy at the NiFe / FeMn interface, and the magnetization of the other magnetic layer (free layer) is fixed. The direction can be changed freely by applying a suitable external magnetic field. Therefore, if only the magnetization direction of the free layer is changed by applying an external magnetic field, the magnetization directions of the two magnetic layers can be made the same or opposite.

As a magnetic thin film memory element utilizing this spin valve film, one disclosed in US Pat. No. 5,343,422 is known. In this magnetic thin-film memory element, binary “0” and “1” are written as two states, that is, the magnetization directions of the two magnetic layers are the same direction or opposite directions, and the difference between the resistance values in both states is detected. Thus, the written information is read. In the case of this type, when reading the difference between the resistance values in the above two states, it is necessary to apply a current to the magnetic thin-film memory element and to apply an external magnetic field. The magnetization direction of the layer may change after reading, and it has been difficult to read non-destructively written information.

[About the induced ferri type] Jpn.J.Appl.Phy
s.33 (1994) L1668 has an induction ferrimagnetic type in which a hard magnetic layer (hard layer) made of CoPt and having a high coercive force and a soft magnetic layer (soft layer) made of NiFeCo are laminated via a nonmagnetic layer Cu. Are shown. In this magnetic thin film, the resistance value changes when the magnetization directions of the hard layer and the soft layer are the same and opposite directions.

As a magnetic thin film memory element using this magnetic thin film, the one shown in Jpn. J. Appl. Phys. Part 2, 34 (1994) L415 is known. In this magnetic thin film memory element, information is written in the hard layer, so that the written information can be read out without being destroyed.

FIGS. 12 to 1 show a case where information is written and a case where information is read from the magnetic thin film memory element.
This will be described with reference to the schematic diagram of the cross section of the thin film shown in FIG.

FIG. 12 shows a case where information is written in this magnetic thin film memory element. As shown in the figure, the magnetic thin film memory element includes a soft layer (magnetic layer) 41 and a hard layer (magnetic layer) 42 stacked with a non-magnetic layer 43 interposed therebetween. A write line 10 generates an external magnetic field. The soft layer 41 and the hard layer 42 are magnetized in the direction of the external magnetic field generated by the current flowing through the write line 10. Then, binary “0” and “1” are assigned to the two magnetization directions of the hard layer 42. In the case of FIG. 12A, a counterclockwise external magnetic field 10a is generated. Is 41a, the magnetization direction of the hard layer 42 is 42a, and in the case of FIG.
A clockwise external magnetic field 10b is generated, and as a result, the magnetization direction of the soft layer 41 becomes 41b and the magnetization direction of the hard layer 42 becomes 42b. In the case of writing, it is necessary to apply an external magnetic field strong enough to change the magnetization direction of the hard layer 42 as well as the soft layer 41.

FIG. 13 shows a case where information written by the counterclockwise external magnetic field 10a shown in FIG. 12A is read. Normally, when information written in the magnetic thin film memory element is read out, the external magnetic field 10a is weak in a counterclockwise direction (a magnetic field intensity in which only the magnetization direction of the soft layer 41 changes) as shown in FIG. A weak external magnetic field 10b in the clockwise direction as shown in FIG. 3 (b) causes a current to flow through the write line 10 so as to be applied to the magnetic thin film memory element in this order. At this time, a current Ir is applied to the read line 5 connected to the magnetic thin film memory element.

Here, a weak counterclockwise external magnetic field 10a
Is added, the magnetization direction 41a of the soft layer 41,
When the magnetization direction 42a of the hard layer 42 becomes the same direction and the clockwise weak external magnetic field 10a is applied, the magnetization direction 41b of the soft layer 41 and the magnetization direction 42
Since a is reversed, the resistance of the magnetic thin film memory element changes from low resistance to high resistance due to the change of the external magnetic field. Therefore, when the external magnetic field changes, the voltage V on the output side of the magnetic thin film memory element drops.

FIG. 14 shows a case where information written by the clockwise external magnetic field 10b shown in FIG. 8B is read.

Here, when a weak counterclockwise external magnetic field 10a is applied as shown in FIG.
When the magnetization direction 41a of the hard layer 42 and the magnetization direction 42b of the hard layer 42 are opposite to each other and a weak clockwise external magnetic field 10a as shown in FIG. Since the magnetization direction 42b of the hard layer 42 is in the same direction, the resistance value of the magnetic thin film memory element changes from high resistance to low resistance due to the change of the external magnetic field. Therefore, when the external magnetic field changes, the voltage V on the output side of the magnetic thin film memory element increases.

As described above, when the external magnetic field applied to the magnetic thin-film memory element is changed by changing the current flowing through the write line 10, the magnetization direction of the hard layer 42 causes the output side of the magnetic thin-film memory element to change. A difference occurs in the fluctuation (rise or fall) of the voltage V. Therefore, by detecting the change in the voltage V, information stored as the magnetization direction of the hard layer 42 can be read.

[0016]

However, a magnetic thin film memory element capable of obtaining a giant magnetoresistance effect has a layer thickness of 10 mm.
Since four or more layers of a very thin magnetic layer of up to 200 A and a conductive nonmagnetic layer of Cu or the like are laminated, the structure and the manufacturing process are complicated, and the manufacturing cost is high.

In a normal magnetic thin film memory, memory elements are arranged in a matrix, and memory elements arranged vertically or horizontally are connected in series by read lines. Since the thickness of this memory element is very small, several hundreds of amperes, and its resistance is high, when a magnetic thin film memory is formed and a current is applied to a read line, heat generation and power loss due to heat generation increase. Therefore, it has been difficult to increase the number of elements to increase the memory capacity.

Therefore, the present invention has been proposed in view of such a conventional situation, and is a magnetic thin film memory having a simple three-layer structure, low resistance, low power loss, and large capacity. The purpose is to provide.

[0019]

The magnetic thin film according to the present invention
In the memory, magnetic thin film memory elements are arranged in a matrix
The magnetic thin film member
Mori device comprises an insulating layer tunneling effect is obtained, the insulation <br/> edge layer is sandwiched therebetween stacked first magnetic layer easy axis is parallel and a second magnetic layer, the second The coercive force of the magnetic layer is
A magnetic thin-film memory having a coercive force greater than that of the first magnetic layer,
Further includes a direction in which the magnetic thin-film memory elements are arranged.
And in a direction perpendicular to this, insulated from each other
Writing for writing information, provided in a state
A line and a layer of the insulating layer for the magnetic thin film memory element
Flowing a current in a direction perpendicular to the plane,
Information by detecting a change in the resistance value of
And a read line for reading .

In the magnetic thin film memory according to the present invention, the difference in coercive force between the first magnetic layer and the second magnetic layer is 20 Oe.
The above is the feature.

[0021]

[0022]

[0023] In addition, the magnetic thin film memory according to the present invention is, above
In serial magnetic thin film memory, the read line is characterized in that for connecting said magnetic thin film memory elements arranged in one direction in series.

[0024]

According to the magnetic thin film memory element of the present invention,
With a simple three-layer structure, a large magnetoresistance change rate (MR change rate) can be obtained.

Further, the current flowing through the insulating layer due to the tunnel effect flows in a direction perpendicular to the layer surface of the insulating layer, so that the resistance of the magnetic thin film memory element can be reduced.

In the case where diamond-like carbon, polyparaxylylene or an oxide containing aluminum as a main component is used as a material of the insulating layer, a tunnel junction having a tunnel effect can be easily formed. Can be.

According to the magnetic thin-film memory using the magnetic thin-film memory element according to the present invention, the memory element is simple.
Because of the layer structure, the magnetic thin film memory can be manufactured by a simple manufacturing process.

According to the magnetic thin film memory using the magnetic thin film memory element according to the present invention, the resistance of the element is small,
In the state where no magnetic field is applied, the elements are in a low resistance state, so that the capacity of the memory can be increased and a magnetic thin film memory with low power consumption can be provided.

[0029]

【Example】

[Configuration of Magnetic Thin Film Memory Element According to the Present Invention]
The magnetic thin film memory element according to the present invention comprises a first magnetic layer and a second magnetic layer.
The magnetic layer has a three-layer structure in which a magnetic layer is tunnel-joined via an insulating layer, and utilizes a magnetic tunneling effect appearing between the first magnetic layer and the second magnetic layer. In general, even when a potential barrier is formed by separating a metal or a semiconductor with a thin insulating layer, conduction electrons pass through the insulating layer to some extent due to a tunnel effect. Also, since the electronic state of the ferromagnetic metal depends on spin, it is known that the tunnel effect appearing between the first magnetic layer and the second magnetic layer depends on the relative angle of the magnetization direction of these magnetic layers. (J. Magn. Mag)
n. Mater. 98 (1991) L7-L9). The magnetoresistance effect at such a tunnel junction is called a magnetic tunneling effect.

Further, the axes of easy magnetization of the first magnetic layer and the second magnetic layer that contribute to the magnetic tunneling effect are parallel, and the coercive force of the second magnetic layer is larger than the coercive force of the first magnetic layer. Therefore, by adjusting the intensity of the external magnetic field applied to the first magnetic layer and the second magnetic layer, it is possible to change the magnetization direction of only the first magnetic layer or both the first magnetic layer and the second magnetic layer.

The electric resistance decreases when the magnetization directions of the first magnetic layer and the second magnetic layer are in the same direction, and increases when the magnetization directions of the first magnetic layer and the second magnetic layer are in the opposite direction (180 ° reverse direction). Accordingly, when the magnetization direction of only the first magnetic layer is changed in a certain order by the external magnetic field (for example, when the magnetization direction is changed from left to right), the magnetization direction of the second magnetic layer is changed according to the magnetization direction. The electrical resistance changes from low resistance to high resistance or from high resistance to low resistance.

Here, since the magnetization direction of the first magnetic layer needs to be changed by an external magnetic field as weak as possible, the coercive force is preferably small, preferably 50 [Oe] or less, more preferably 10 [Oe] or less. It is. Here, the range of the coercive force is 50 [Oe].
The reason for the following is that if the magnetization direction is changed above 50 [Oe], a current for generating a strong external magnetic field is required. Therefore, when a magnetic thin film memory is configured, heat generation and noise increase, resulting in malfunction. Because it may The magnitude of the coercive force of the magnetic layer can be set to a predetermined value by adjusting the composition, the layer thickness, and the film forming conditions.
The layer thickness is preferably from 5 to 100 nm. This is because if the thickness is less than 5 nm, the film becomes an island shape, and the electric resistance increases, which is not preferable. Further, as a material of the first magnetic layer, Fe, NiFe, NiFeCo, or the like can be used.

On the other hand, the coercive force of the second magnetic layer must be larger than the coercive force of the first magnetic layer, and is preferably 50 [O
e] or more, more preferably 100 [Oe] or more. The reason for setting the coercive force range to 50 [Oe] or more is that if the coercive force is smaller than 50 [Oe], the magnetization direction is disturbed by the influence of an external disturbance magnetic field or the like, and the memory may be destroyed. .
In addition, the magnitude of the coercive force of the second magnetic layer can be set to a predetermined magnitude by adjusting the composition, the layer thickness, and the film forming conditions, similarly to the first magnetic layer. 5-1
Preferably it is 00 nm. Further, as a material of the second magnetic layer, Co, CoFe, CoPt, MnSb, or the like can be used.

The difference in coercive force between the first magnetic layer and the second magnetic layer is required to be at least 20 [Oe], preferably at least 50 [Oe], more preferably at least 100 [Oe]. Here, the reason why the difference in coercive force is set to 20 [Oe] or more is that if the difference in coercive force is smaller than 20 [Oe], it is added to change only the magnetization direction of the first magnetic layer when reading information. This is because the allowable variation range of the external magnetic field, that is, the allowable variation range of the current for generating the external magnetic field is reduced.

In order to obtain the above-mentioned magnetic tunneling effect, the thickness of the insulating layer sandwiched between the first magnetic layer and the second magnetic layer must be uniformly reduced, preferably 1-2.
0 nm, more preferably in the range of 1 to 10 nm. Here, the range of the layer thickness of the insulating layer was set to 1 to 20 nm by 1 nm.
If the thickness is smaller, the number of pinholes increases, and a uniform potential barrier is not formed. If the thickness is larger than 20 nm, the tunneling effect does not occur. Therefore, as the material of the insulating layer, a material that does not easily generate pinholes even when the thickness is small is required. Suitable materials for the material are diamond-like carbon (hereinafter, referred to as DLC) and polyparaxylyl. Oxides containing len and aluminum as main components are mentioned, but DLC or polyparaxylylene is preferably used.

[Operation Principle of Magnetic Thin Film Memory Element According to the Present Invention] The thin film shown in FIGS. 1 to 3 is used for writing information to the magnetic thin film memory element according to the present invention and reading information from the magnetic thin film memory element. A description will be given with reference to a schematic diagram of a cross section.

FIG. 1 shows a case where information is written in the magnetic thin film memory element. As shown in FIG. 1, the magnetic thin film memory element includes a first magnetic layer 1 and a second magnetic layer 2 stacked with an insulating layer 3 interposed therebetween. Reference numeral 10 denotes a write line for generating an external magnetic field. The first magnetic layer 1 and the second magnetic layer 2 are magnetized in the direction of the external magnetic field generated by the current flowing through the write line 10. Then, binary “0” and “1” are assigned to the magnetization direction of the second magnetic layer 2.

In the case of FIG. 1A, a current flowing through the write line 10 generates a counterclockwise external magnetic field 10a,
As a result, the magnetization direction of the first magnetic layer 1 becomes 1a, and the magnetization direction of the second magnetic layer 2 becomes 2a. In the case of (b), a clockwise external magnetic field 10b is generated. The magnetization direction of 1 is 1b, and the magnetization direction of the second magnetic layer 2 is 2b.
In the case of writing, it is necessary to apply an external magnetic field having a strength sufficient to change the magnetization direction of the second magnetic layer 2 as well as the first magnetic layer 1.

FIG. 2 shows a case where information written by the counterclockwise external magnetic field 10a shown in FIG. 1A is read. Normally, when information written in the magnetic thin film memory element is read out, a weak counterclockwise (magnetic field intensity in which only the magnetization direction of the first magnetic layer 1 changes) external magnetic field as shown in FIG. 10a and a weak clockwise external magnetic field 10b as shown in (b) in this order cause a current to flow through the write line 10 so as to be applied to the magnetic thin film memory element. At this time, a current Ir is applied to the read line 5 connected to the magnetic thin film memory element.

Here, the counterclockwise weak external magnetic field 10a
Is applied, the magnetization direction 1a of the first magnetic layer 1 and the magnetization direction 2a of the second magnetic layer 2 become the same direction, and when a weak clockwise external magnetic field 10a is applied, the first magnetic layer 1 Tier 1
Since the magnetization direction 1b of the magnetic thin film memory device and the magnetization direction 2a of the second magnetic layer 2 are opposite to each other, the resistance of the magnetic thin film memory element changes from low resistance to high resistance due to the change of the external magnetic field. Therefore, when the external magnetic field changes, that is, when the current flowing through the write line 10 is changed, the voltage V on the output side of the magnetic thin film memory element drops.

FIG. 3 shows a case where information written by the clockwise external magnetic field 10b shown in FIG. 1B is read.

Here, the counterclockwise weak external magnetic field 10a
Is applied, the magnetization direction 1a of the first magnetic layer 1 and the magnetization direction 2b of the second magnetic layer 2 become opposite directions, and when the clockwise weak external magnetic field 10a is applied, the first magnetic layer 1 Since the magnetization direction 1b of the layer 1 and the magnetization direction 2b of the second magnetic layer 2 are in the same direction, the change in the external magnetic field changes the resistance of the magnetic thin film memory element from high resistance to low resistance. Therefore, when the external magnetic field changes, the voltage V on the output side of the magnetic thin film memory element increases.

As described above, when the external magnetic field applied to the magnetic thin-film memory element is changed by changing the current flowing through the write line 10, the output of the magnetic thin-film memory element depends on the magnetization direction of the second magnetic layer 2. A difference occurs in the fluctuation of the voltage V on the side.

When the magnetization direction of the first magnetic layer is different from the magnetization direction of the second magnetic layer when the external magnetic field is removed, the magnetization direction of the first magnetic layer becomes more coercive than the first magnetic layer. The direction returns to the same direction as the magnetization direction of the large second magnetic layer. Therefore, when the magnetic thin film memory is configured by arranging the magnetic thin film memory elements in a matrix, all the elements to which no external magnetic field is applied have low resistance, so that heat generation and power loss due to heat generation can be reduced. it can.

FIG. 4 (a) shows a current flowing from the + side to the − side flowing through the write line when reading information (hereinafter, referred to as “current”).
(B) and (c) are referred to as (a)
3 shows the fluctuation of the voltage V on the output side of the magnetic thin film memory element when the reproduction pulse current shown in FIG. Here, as shown in (a) of the figure, when the current flowing through the write line changes from the + side to the-side, the external magnetic field applied to the magnetic thin film memory element changes. In other words, when it is on the + side, FIG.
The counterclockwise magnetic field shown in FIG. 3 is generated, and when it is on the negative side, the counterclockwise magnetic field shown in FIGS. And
At the time of this change, the voltage V on the output side of the magnetic thin film memory element becomes
Depending on the magnetization direction of the second magnetic layer, it rises as shown in (b) or falls as shown in (c). Therefore, when reading information, a reproduction pulse current is applied to the write line, and at that time, a voltage fluctuation occurring in the read line connected to the output side of the magnetic thin film memory element is detected, thereby determining the magnetization direction of the second magnetic layer. can do.

When reading out information, the magnetization direction of the second magnetic layer can be determined by flowing only the current on the + side as shown in FIG. 4D. In this case, when reading information, only a magnetic field (a counterclockwise magnetic field shown in FIGS. 2 and 3) due to a current on the + side is applied to the magnetic thin film memory element. Then, when this current is passed, the voltage V on the output side of the magnetic thin film memory element does not fluctuate as shown in (e) or as shown in (c) depending on the magnetization direction of the second magnetic layer. Fluctuates (decreases). Therefore,
The magnetization direction of the second magnetic layer can be determined by detecting whether or not a voltage change occurs when a current flows.

Since the two magnetization directions of the second magnetic layer are assigned to binary “0” and “1”, the setting of the magnetization direction of the second magnetic layer depends on the magnetic thin film memory element. In response to writing of information, detection of the magnetization direction of the second magnetic layer corresponds to reading of information from the magnetic thin film memory element.

[About the Magnetic Thin Film Memory According to the Present Invention] The magnetic thin film memory according to the present invention will be described with reference to FIGS.

FIG. 5 shows a plan view (a) of one element portion and a cross-sectional view taken along the line AA ′ (b) of a magnetic thin film memory, and shows a first magnetic layer 1 and a second magnetic layer connected to a read line 5. 2
They are stacked via an insulating layer 3. Here, the first magnetic layer 1 and the second magnetic layer 2 are tunnel-joined, and a portion where the first magnetic layer 1 and the second magnetic layer 2 overlap is a tunnel junction. The coercive force of the second magnetic layer 2 is
Larger than the coercive force.

In the magnetic thin film memory device of the present invention, the read current flowing through the tunnel junction is, as indicated by the arrow 8, a current flowing in a direction perpendicular to the film surface of the insulating layer 3, so that the read current is Resistance is reduced, and heat generation of the element can be reduced. Further, a submicron-order element can be formed, and the memory capacity can be increased.

A writing line 10 is provided in a direction perpendicular to the axis of easy magnetization 4 of the magnetic thin film memory element, and a writing auxiliary line 20 is provided in a direction parallel to the writing line 10. The magnetic thin film memory element, the write line 10 and the write auxiliary line 20 are insulated by the insulating films 7 and 6.

FIG. 6 is a plan view (a) of a thin film magnetic memory.
BB ′ sectional view (b) of FIG.
Magnetic thin film memory elements are arranged in a matrix at portions where the write assist lines 12, 22, and 23 are orthogonal to each other. Here, they are arranged in the writing auxiliary line direction.
The magnetic thin film memory elements are connected in series via the read line 5.
Has been continued. For example, in the portion shown in the section BB ′,
Magnetic thin film memory elements 31, 32, 33 are connected in series
The portion becomes the read line 5.

As described above, when the magnetic thin film memory elements are arranged in a matrix, a write current sufficient to change the magnetization direction of the second magnetic layer of the magnetic thin film memory element was applied to the write line. In this case, the first magnetic layer and the second magnetic layer of the magnetic thin film memory arranged along the write line through which the write current has flowed are all magnetized in the direction of the magnetic field generated by the write current. That is, writing is all performed on the magnetic thin-film memories arranged along the write line through which the write current has flowed. Therefore, when the magnetic thin film memory elements are arranged in a matrix,
It is not possible to direct only the magnetization direction of some of the magnetic thin-film memory elements to a desired magnetization direction with only the current flowing through the write lines, that is, to write information only to some of the elements.

Here, when a current is caused to flow through both the write line and the write auxiliary line so that only the magnetization direction of a part of the magnetic thin film memory elements arranged in a matrix is directed to a desired magnetization direction. That is, a case where information is written to only some of the elements will be described with reference to FIGS.

In FIG. 7A, Iw1 indicates a write current flowing through the write line 10, and Iw indicates a write auxiliary current flowing through the write auxiliary line 20. And Hw
1 indicates a write magnetic field generated by the write current Iw1, and Hw indicates a write auxiliary magnetic field generated by the write auxiliary current Iw. Here, the write magnetic field Hw1
Since the write assist magnetic field Hw is smaller than the coercive force of the second magnetic layer of the magnetic thin film memory element, the magnetization direction of the second magnetic layer cannot be changed by only one magnetic field.
However, since the composite magnetic field H1 of the write magnetic field Hw1 and the write auxiliary magnetic field Hw is larger than the coercive force of the second magnetic layer,
When both the write current Iw1 and the write auxiliary current Iw are passed, the magnetization direction of the second magnetic layer can be changed.

FIG. 7B shows the write magnetic field Hw1, the write auxiliary magnetic field Hw, the composite magnetic field H1, and the axis of easy magnetization 4 of the second magnetic layer 2. Here, since the synthetic magnetic field H1 is larger than the coercive force of the second magnetic layer 2, the second magnetic layer 2 is magnetized by the synthetic magnetic field H1, and its magnetization direction B1 is parallel to the easy axis 4 of the synthetic magnetic field H1. Component direction. The write magnetic field Hw1 generated by the write current Iw1
Is a write auxiliary magnetic field Hw substantially parallel to the easy axis 4 of the second magnetic layer 2 and generated by the write auxiliary current Iw.
Is substantially perpendicular to the easy axis 4 of the second magnetic layer 2, the magnetization direction B1 is determined by the write magnetic field Hw1, that is, the write current Iw1.

FIG. 8A shows the write current Iw1 of FIG.
And the write current Iw2 flows in the opposite direction. Accordingly, the direction of the generated write magnetic field Hw2 is also opposite to the direction of the write magnetic field Hw1 in FIG. Accordingly, as shown in FIG. 7B, the magnetization direction B2 of the second magnetic layer
The direction is opposite to 1.

As described above, in the case where the magnetic thin film memory elements are arranged in a matrix, current is applied only to the write line and write auxiliary line passing through the portion of the magnetic thin film memory element whose magnetization direction is to be changed. Only the magnetization direction of the magnetic thin film memory element at that portion can be changed. Further, the magnetization direction of the magnetic thin film memory element can be directed in a desired direction depending on the direction of the current flowing through the write line.

On the other hand, when reading information written in the magnetic thin-film memory elements arranged in a matrix, a read current is applied to a read line connected to the magnetic thin-film memory element to be read, and the magnetic thin-film memory is read. A reproduction pulse current is supplied to a write line passing through the element portion, and a voltage variation of the read line when the reproduction pulse current is supplied is detected to determine a magnetization direction of the second magnetic layer, which is written information. be able to.

Example 1 First Magnetic Layer 1 with Small Coercive Force
Fe, Co as the second magnetic layer 2 having a large coercive force,
Using DLC as the insulating layer 3, Fe (50 nm) / DLC
A (2 nm) / Co (50 nm) ferromagnetic tunnel junction and a magnetic thin film memory element were fabricated. FIG. 9 shows a perspective view (a) and a schematic plan view (b) of a sample prepared for examining the magnetoresistance curve of the ferromagnetic tunnel junction 9. The magnetic resistance curve was measured by a DC four-terminal method under an applied magnetic field of 500 [Oe]. Also, a Fe / DLC / Co3 layer film having a size of 10 mm square was prepared, and the magnetization curve was examined by VSM.

Hereinafter, a process of forming a ferromagnetic tunnel junction will be described.

First, an Fe layer was formed with a thickness of 50 nm on a glass substrate by DC sputtering under the following film forming conditions.

Ultimate pressure 5 × 10 ⁻⁵ Pa Ar gas 10 SCCM Film formation pressure 0.5 Pa Input power 100 W Film formation rate 0.5 nm / sec The Fe layer thus obtained is subjected to fine processing technology. 1mm using
The first magnetic layer 1 was patterned into a rectangle of × 10 mm.

Next, plasma CVD is performed on the first magnetic layer 1.
A DLC film having a thickness of 2 nm was formed by the method under the following film forming conditions.

Ultimate pressure 3 × 10 ⁻³ Pa Ethylene gas 10 SCCM Film formation pressure 3 Pa Input power 100 W Film formation rate 10 nm / min The DLC film thus obtained is finely processed into φ3 mm, and the insulating layer is formed. It was set to 3.

Subsequently, the film was transferred to a DC sputtering apparatus again, and a Co layer was formed with a thickness of 50 nm under the following film forming conditions.

Ultimate pressure 5 × 10 ⁻⁵ Pa Ar gas 10 SCCM Film formation pressure 0.5 Pa Input power 100 W Film formation rate 0.5 nm / sec The Co layer obtained in this manner is used as the first magnetic layer. In the same manner as described above, patterning was performed in a stripe shape of 1 mm × 10 mm by a fine processing technique to form a ferromagnetic tunnel junction 9 of Fe / DLC / Co having a junction area of 1 mm × 1 mm, and the magnetoresistance curve was examined.

A 10 mm × 10 mm tunnel junction was formed in the same manner, and the magnetization curve was examined. As a result, FIG.
And the magnetization curve by VSM shown in FIG. 11 were obtained. Here, the MR change rate shown in FIG. 10 is given by (ΔR / R) × 100 (R: resistance value, ΔR: amount of change in resistance value). In the sample of this embodiment, the applied magnetic field is 100 [Oe]. In the following, an MR change rate of 12% was obtained.

Using this Fe / DLC / Co ferromagnetic tunnel junction, a magnetic thin film memory element as shown in FIG.
It was produced in the following steps.

First, an Fe layer was formed to a thickness of 50 nm while applying a magnetic field of 500 [Oe] in the direction of forming readout lines on a glass substrate, and then 2 μm ×
The first magnetic layer 1 was patterned into a rectangular shape of 10 μm. Thus, by forming a film while applying a magnetic field, the axis of easy magnetization of the formed magnetic layer becomes parallel to the direction of the applied magnetic field.

Next, a diamond-like carbon (DLC) film having a thickness of 2 nm was formed on the first magnetic layer 1 and finely processed to form an insulating layer 3.

Subsequently, the film was transferred to a DC sputtering apparatus again, and a Co layer was formed with a thickness of 50 nm while applying the same magnetic field as in the case of the Fe layer.
The resultant was patterned into a stripe shape of × 10 μm to form a second magnetic layer 2. By the above process, the bonding area is 1μm × 3μm
Fe / DLC / Co tunnel junction was formed.

Next, Cr (5 nm) / Au (200 nm) / Cr is connected so as to be connected to the first magnetic layer 1 and the second magnetic layer 2.
A (5 nm) film was formed as the read line 5.

Subsequently, the insulating film 7 made of alumina was subjected to RF
After a film thickness of 200 nm is formed by sputtering, Cr (5n
m) / Au (200 nm) / Cr (5 nm) film was formed and patterned in a strip shape in the direction parallel to the read line 5 on the upper part of the tunnel junction to form the write assist line 20. Further, in the same manner, an insulating film 6 made of alumina having a film thickness of 200 nm and a write line 10 patterned in a belt shape in a direction perpendicular to the write auxiliary line 20 were formed to obtain a magnetic thin film memory element.

When the operation of the magnetic thin film memory thus obtained was confirmed, writing and reading could be performed normally. That is, at the time of writing, the first magnetic layer 1 and the second magnetic layer 2 of the magnetic thin-film memory element are magnetized in the direction of the magnetic field generated by the writing current, and at the time of reading, a reproduction pulse current is supplied to allow the desired read line to be read. Was obtained.

(Example 2) A ferromagnetic tunnel junction having the film configuration shown in Table 1 was prepared in the same manner as in Example 1, and the magnetoresistance curve was examined. The obtained magnetoresistance change rate was shown in Table 1. Indicated. As shown in the table, 5 to 5
It was confirmed that an MR change rate of 25% was obtained.

Next, a magnetic thin film memory device using these ferromagnetic tunnel junctions was manufactured, and operation was confirmed in the same manner as in Example 1. As a result, writing and reading could be performed normally.

For the comparative sample, a ferromagnetic tunnel junction using the diamond-like carbon film as an insulating layer with the film configuration shown in Table 1 was prepared in the same manner, and the magnetoresistance curve was examined. The rate of change is shown in Table 1. As shown in the table, each of the comparative samples had an M of 0.1 to 0.2%.
Only the R change rate was obtained. The reason for this is considered to be that if the thickness of the insulating layer is as thin as 1 nm, a uniform insulating layer is not formed, so that the number of pinholes increases and an electrical bridge is formed between the two magnetic layers. Further, it is considered that when the insulating layer is as thick as 30 nm, the tunnel current is scattered.

Next, a magnetic thin film memory element using a ferromagnetic tunnel junction of a comparative sample was manufactured, and its operation was confirmed in the same manner as in the above sample. As a result, it did not operate normally.

[0080]

[Table 1]

Example 3 In the same manner as in Example 1, a ferromagnetic tunnel junction having a film configuration shown in Table 2 and polyparaxylylene as an insulating layer was manufactured, and a magnetoresistance curve was examined.
Table 2 shows the obtained magnetoresistance ratios. As shown in the table, it was confirmed that an MR change ratio of 6 to 13% was obtained for each of the samples.

Here, the polyparaxylylene film was formed by the following method. First, diparaxylylene as a raw material is vaporized under vacuum at about 150 ° C., and then 600 ° C. in a furnace.
To form a polyparaxylylene film at a reaction pressure of 20 mTorr in a film forming chamber. Parylene N and Parylene C manufactured by Union Carbide Co. were formed as polyparaxylylene at a film formation rate of 10 nm / min.

Next, a magnetic thin film memory element using these ferromagnetic tunnel junctions was manufactured, and operation was confirmed in the same manner as in Example 1. As a result, writing and reading could be performed normally.

For a comparative sample, a ferromagnetic tunnel junction using a polyparaxylylene or a polymonoxylparaxylylene as an insulating layer with the film configuration shown in Table 2 was prepared in the same manner, and a magnetoresistance curve was obtained. Table 2 shows the obtained magnetoresistance change rates. As shown in the table, all of the comparative samples obtained only the MR ratio of 0.1 to 0.3%.
The reason for this is considered to be that if the thickness of the insulating layer is as thin as 1 nm, a uniform insulating layer is not formed, so that the number of pinholes increases and an electrical bridge is formed between the two magnetic layers. Further, it is considered that when the thickness of the insulating layer is as large as 25 nm, the tunnel current is scattered.

Next, a magnetic thin film memory element using a ferromagnetic tunnel junction of a comparative sample was manufactured, and operation was confirmed in the same manner as in the above sample. As a result, it did not operate normally.

[0086]

[Table 2]

Example 4 In the same manner as in Example 1, a ferromagnetic tunnel junction having the film configuration shown in Table 3 and using Al ₂ O ₃ as an insulating layer was fabricated, and the magnetoresistance curve was examined. Table 3 shows the obtained magnetoresistance ratios. As shown in the table,
It was confirmed that an MR change rate of 13 to 20% was obtained for each of the samples.

Here, the Al ₂ O ₃ insulating layer was formed by sputter-treating an Al metal film in the air for 24 hours after forming it by sputtering.

Next, a magnetic thin film memory element using these ferromagnetic tunnel junctions was manufactured, and operation was confirmed in the same manner as in Example 1. As a result, writing and reading could be performed normally.

For the comparative sample, in the same manner, a ferromagnetic tunnel junction having the film configuration shown in Table 3 and using Al ₂ O ₃ as an insulating layer was produced, and the magnetoresistance curve was examined. Are shown in Table 3. As shown in the table, only 0.2% MR change was obtained in the comparative sample. It is considered that the reason for this is that since the insulating layer is as thin as 1 nm, the number of pinholes increases and an electrical bridge can be formed between the upper and lower magnetic layers.

Next, a magnetic thin film memory element using a ferromagnetic tunnel junction of a comparative sample was manufactured, and operation was confirmed in the same manner as in the above sample. As a result, it did not operate normally.

[0092]

[Table 3]

Further, the resistance of the magnetic thin film memory elements manufactured in Examples 1 to 3 was examined. As a result, it was very low, 1 to 5Ω. This value is as low as 1/10 or less of the resistance of the GMR memory element having the same size of the spin valve structure.

As is clear from the above, according to the present invention,
A very simple magnetic thin film memory element having a three-layer structure of a magnetic layer / insulating layer / magnetic layer and low resistance can be provided.

[0095]

According to the present invention, there is provided a magnetic thin film memory element comprising:
As described above, since a large MR ratio can be obtained with a simple three-layer structure, a magnetic thin-film memory element can be formed at low cost.

Further, the resistance of the magnetic thin film memory element can be reduced, and heat generation in the element can be reduced.

In the case where diamond-like carbon, polyparaxylylene or an oxide containing aluminum as a main component is used as a material for the insulating layer, a tunnel junction having a tunnel effect can be easily formed. Can be.

Further, a magnetic thin film memory can be manufactured only by a simple manufacturing process without forming a very thin magnetic layer or conductive non-magnetic layer, so that the manufacturing yield can be improved.

Further, the magnetic thin film memory element according to the present invention has a low resistance and is in a low resistance state when no magnetic field is applied, so that the memory capacity can be increased and the magnetic thin film memory with low power consumption can be realized. Can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a write operation on a magnetic thin film memory element according to the present invention.

FIG. 2 is a cross-sectional view for explaining a read operation on the magnetic thin film memory element according to the present invention.

FIG. 3 is a cross-sectional view for explaining a read operation for the magnetic thin film memory element according to the present invention.

FIG. 4 is a waveform diagram showing a current waveform of a reproduction pulse current and a voltage fluctuation generated in a read line due to the reproduction pulse current.

FIG. 5 is a plan view and a sectional view showing the structure of a magnetic thin film memory element according to the present invention.

FIG. 6 is a plan view and a sectional view showing the configuration of a magnetic thin film memory according to the present invention.

FIG. 7 is an explanatory diagram for explaining a write operation for an element constituting the magnetic thin film memory according to the present invention.

FIG. 8 is an explanatory diagram for explaining a write operation for an element constituting the magnetic thin film memory according to the present invention.

9A and 9B are a perspective view and a plan view showing a sample of a tunnel junction.

FIG. 10 is a graph showing a magnetoresistance curve in the tunnel junction of Example 1.

FIG. 11 is a graph showing a magnetization curve in the tunnel junction of Example 1.

FIG. 12 is a cross-sectional view for explaining a write operation for a conventional magnetic thin film memory element.

FIG. 13 is a cross-sectional view for explaining a read operation for a conventional magnetic thin film memory element.

FIG. 14 is a cross-sectional view for explaining a read operation for a conventional magnetic thin film memory element.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first magnetic layer 2 second magnetic layer 3 insulating layer 4 easy axis 5 read line 6, 7 insulating film 10, 11, 12, 13 write line 20, 21, 22, 23 write auxiliary line

Continuation of the front page (72) Inventor Osamu Shinoura Examiner Hiromitsu Suhara in TDC Corporation, 1-13-1 Nihonbashi, Chuo-ku, Tokyo (56) References JP-A-7-66033 (JP, A) Noriyuki, 2 others, Magnetic tunneling effect of ferromagnetic / A12O3 / ferromagnetic junction, Journal of the Japan Society of Applied Magnetics, Japan, Japan Society of Applied Magnetics, vol. 19 No. 2, 369-372 (58) Fields investigated (Int. Cl. ⁷ , DB name) G11C 11/14-11/15 H01L 27/10 H01L 43/08 H01F 10/32

Claims (3)

(57) [Claims] 1. A magnetic thin film memory element is arranged in a matrix.
Magnetic thin film medium having storage element portions arranged and arranged
Memory , wherein the magnetic thin film memory element is capable of achieving a tunnel effect.
And the edge layer, are stacked to sandwich the insulating layer, the magnetization easy axis has a first magnetic layer and the second magnetic layer are parallel, the coercive force of the second magnetic layer, the coercive of the first magnetic layer greater than the magnetic force, the magnetic thin film memory further, one-way and this vertical to the magnetic thin film memory element is arranged
Placed in a straight direction and insulated from each other.
Two write lines for writing information, and a perpendicular line on the surface of the insulating layer with respect to the magnetic thin film memory element.
A current flows in a direct direction, and the resistance of the magnetic thin film memory element is reduced.
For reading information by detecting a change in value
A magnetic thin film memo having a read line
Re . 2. The magnetic thin film memory according to claim 1, wherein a difference in coercive force between said first magnetic layer and said second magnetic layer is two.
A magnetic thin film memory characterized by being at least 0 Oe. 3. The magnetic thin film memory according to claim 1, wherein
In the read line, the magnetic thin film memory, characterized in that for connecting said magnetic thin film memory elements arranged in one direction in series.