JPH11353867A - Magnetic thin film memory device and method for recording information, method for reproducing information using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cell width of one bit and enhance the integration degree by using two magnetic layers of a closed magnetic circuit structure and regulating the length range of a generated magnetic field. SOLUTION: In this magnetic thin film memory device, a first magnetic layer of a closed magnetic circuit structure and a second magnetic layer of a closed magnetic circuit structure having coercive force higher than the first magnetic layer are layered via a non-magnetic layer. The first, second magnetic layer has an axis of easy magnetization in left turning or right turning, showing a different resistance value in accordance with a relative angle of directions of magnetization of the first, second magnetic layers. A current is supplied perpendicularly to film faces of the first, second magnetic layers, whereby a length of a current path where information is to be recorded by a generated magnetic field is set to be 0.05-2 μm. Moreover, the current is supplied upward or downward perpendicularly to a film face of the magnetic thin film memory element beforehand, and a size of the current is set to generate the magnetic field larger than a magnetization inverted magnetic field of the second magnetic layer.

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 recorded information by utilizing a magnetoresistance effect, an information recording method using the same, and an information reproducing method. It is.

[0002]

2. Description of the Related Art Conventionally, a magnetic thin film memory is known as a solid state memory having no moving parts, like a semiconductor memory. Such a magnetic thin-film memory is compared with a semiconductor memory in that information is not lost even when the power is turned off, the number of times of repeated rewriting of information is infinite, and there is no danger of losing information even when radiation is incident. Have many advantages.
In particular, thin film magnetic memories utilizing the giant magnetoresistance (GMR) effect have recently attracted attention because they can provide a larger output than conventional magnetic thin film memories using the anisotropic magnetoresistance effect.

[0003] For example, the journal of the Japan Society of Applied Magnetics, Vol. 2
0. P22 (1996) includes a hard magnetic film (HM), a non-magnetic film (NM), a soft magnetic film (SM), as shown in FIG.
There has been proposed a solid-state memory in which a non-magnetic film (NM) is stacked to form a memory element. This memory element is provided with a sense line S coupled to a metal conductor and a word line W insulated from the sense line S by an insulating film I as shown in FIG.
Information is written by a magnetic field generated by the current of the word line W and the current of the sense line S.

More specifically, a current I is applied to a word line W.
To generate a magnetic field in a different direction depending on the current direction ID, thereby performing magnetization reversal of the hard magnetic film HM,
Recording of the memory states “0” and “1” is performed. For example, FIG.
When a positive current is supplied to the word line W as shown in FIG. 9A, a rightward magnetic field is generated as shown in FIG. 9B, and "1" can be recorded on the hard magnetic film HM. FIG.
When a negative current is supplied to the word line I as shown in FIG. 9C, a leftward magnetic field is generated as shown in FIG.
“0” can be recorded in M.

On the other hand, when reading information, the word line W
To the soft magnetic film S
Information is read out by causing only the magnetization reversal of M and detecting a resistance change at that time. When the giant magnetoresistance effect is used, the resistance values of the soft magnetic film SM and the hard magnetic film HM are different depending on whether the magnetization is in the same direction or in the opposite direction.
The memory state of "1" or "0" is determined based on the resistance change occurring at that time. Specifically, when a pulse that changes from positive to negative as shown in FIG. 10A is applied, the magnetization direction of the soft magnetic film SM changes from the rightward state in FIG.
When the memory state is “1”, the magnetizations of the hard magnetic film HM and the soft magnetic film SM are changed from the small resistance value in the same direction in the case of the memory state “1”. Changes to a large resistance value in the opposite direction. In the case of the memory state "1", the resistance changes from a large resistance value as shown in FIG. 10D to a small resistance value as shown in FIG. Therefore, by reading such a change in resistance value,
Regardless of the magnetization state of the soft magnetic film SM after recording, the information recorded on the hard magnetic film HM can be read, and nondestructive reading can be performed.

[0006]

However, in the above-mentioned conventional thin film magnetic memory, the demagnetizing field (self-demagnetizing field) generated in the magnetic layer as the bit cell area decreases.
However, there is a problem that the magnetization direction of the magnetic layer for recording and holding is not fixed in a fixed direction and becomes unstable.
Therefore, there is a limit to miniaturization of the bit cell, and high integration cannot be sufficiently performed.

The present invention has been made in view of the above-mentioned conventional problems, and provides a magnetic thin-film memory element capable of eliminating the influence of a demagnetizing field of a magnetic film and achieving higher integration, and an information recording method and an information reproducing method using the same. The purpose is to do.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a first magnetic layer having a closed magnetic circuit structure and a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the first magnetic layer. The first and second magnetic layers have an easy axis in a counterclockwise or clockwise direction, and are formed by a relative angle of the magnetization direction of the first and second magnetic layers. A magnetic thin film memory element having different resistance values, wherein a current is supplied in a direction perpendicular to the film surfaces of the first and second magnetic layers, and a length of a current path for recording information by a generated magnetic field is set to 0. It is attained by a magnetic thin film memory element characterized in that the thickness is not less than 0.05 μm and not more than 2 μm.

An object of the present invention is a method of recording information on a magnetic thin film memory device according to claim 1, wherein a current is supplied in advance vertically or vertically to the film surface of the magnetic thin film memory device. By setting the magnitude of the current so that a magnetic field larger than the magnetization reversal magnetic field of the second magnetic layer is generated, the direction of the magnetization of the second magnetic layer is set to a predetermined direction regardless of the recording information. Then, a current is supplied upward or downward according to recorded information in a direction perpendicular to the film surface of the magnetic thin film memory element, and the magnitude of the current is larger than the magnetization reversal magnetic field of the first magnetic layer. Recording information in the first magnetic layer in accordance with the direction of magnetization by setting a magnetic field smaller than the magnetization reversal magnetic field of the second magnetic layer. One It is achieved by.

An object of the present invention is to provide a first magnetic layer having a closed magnetic circuit structure and a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the first magnetic layer via a nonmagnetic layer. The first and second magnetic layers have an easy axis counterclockwise or clockwise, and have different resistance values depending on the relative angle of the magnetization direction of the first and second magnetic layers. A method of recording information on a thin film memory element, comprising supplying a current upward or downward in a direction perpendicular to a film surface of the memory element according to recording information, and controlling a magnitude of the current to the second magnetic layer. By setting such that a magnetic field larger than the magnetization reversal magnetic field is generated, information is recorded in the second magnetic layer in accordance with the direction of its magnetization.

An object of the present invention is to form a first magnetic layer having a closed magnetic circuit structure and a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the first magnetic layer via a nonmagnetic layer. The first and second magnetic layers have an easy axis counterclockwise or clockwise, and have different resistance values depending on the relative angle of the magnetization direction of the first and second magnetic layers. A method of reproducing information recorded in a thin-film memory element in accordance with the direction of magnetization of the second magnetic layer, wherein a current is supplied in a direction perpendicular to a film surface of the magnetic thin-film memory element, The information reproducing method is characterized by reproducing the recorded information by initializing the magnetization of one magnetic layer in a predetermined direction and measuring the resistance of the magnetic thin film memory element in this state. .

An object of the present invention is to form a first magnetic layer having a closed magnetic circuit structure and a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the first magnetic layer via a nonmagnetic layer. The first and second magnetic layers have an easy axis counterclockwise or counterclockwise, and have different resistance values depending on the relative angles of the magnetization directions of the first and second magnetic layers, In a magnetic thin film memory element in which the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are in a parallel or anti-parallel state when no magnetic field is applied, according to the direction of the magnetization of the second magnetic layer. A method of reproducing the information recorded in the magnetic thin film memory element, first measuring a resistance value of the magnetic thin film memory element, then supplying a current in a direction perpendicular to a film surface of the magnetic thin film memory element, After orienting the magnetization of the magnetic layer in a predetermined direction,
The information reproduction method is characterized in that the resistance value of the magnetic thin film memory element is measured again, and the recorded information is reproduced by measuring the resistance change at this time.

An object of the present invention is to interpose a first magnetic layer having a closed magnetic circuit structure and a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the first magnetic layer via a nonmagnetic layer. The first and second magnetic layers have an easy axis counterclockwise or clockwise, and have different resistance values depending on the relative angle of the magnetization direction of the first and second magnetic layers. A method for reproducing recorded information in a thin-film memory element in accordance with the direction of magnetization of said second magnetic layer, comprising supplying a current to said second magnetic layer from one surface, The resistance of the magnetic thin film memory element is measured by reversing the magnetization of the layer, and then a current is supplied to the memory element from the opposite side to invert the magnetization of the first magnetic layer, thereby reversing the magnetization of the first magnetic layer. Measures the resistance value and reproduces the recorded information based on the obtained resistance change It is achieved by an information reproducing method comprising Rukoto.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of one embodiment of a magnetic thin film memory element of the present invention. In FIG. 1, reference numeral 1 denotes a columnar first magnetic layer, and reference numeral 2 denotes a columnar second magnetic layer. A non-magnetic layer 3 is provided between the first and second magnetic layers 1 and 2. The 1st and 2nd magnetic layers 1 and 2 and the nonmagnetic layer 3 of FIG. 1 constitute a 1-bit cell memory element. Each of the first and second magnetic layers 1 and 2 has an easy axis counterclockwise or counterclockwise, and its magnetization is annularly oriented along a columnar shape. The arrows in FIG. 1 are the first and second arrows.
Of the magnetic layers 1 and 2 of FIG. Incidentally, the magnetic layer is not limited to a columnar shape, and may have a structure having a square cross section.
It suffices if the magnetization is oriented in a closed magnetic path. However, a columnar structure is desirable because it is the most stable closed magnetic circuit structure.

In this embodiment, when the magnetization directions of the first and second magnetic layers 1 and 2 are the same, the resistance between the first and second magnetic layers 1 and 2 shows a low resistance value. When the first and second magnetization directions are in opposite directions, a high resistance value is exhibited. Since the resistance value of the memory element varies depending on the magnetization direction of the first magnetic layer 1, magnetization information can be read by using this. Also, the magnetization information of “0” and “1” is
Recording is performed so as to correspond to the counterclockwise or counterclockwise direction of magnetization of the second magnetic layers 1 and 2. That is, the first and second magnetic layers 1
A current is supplied upward or downward in the direction perpendicular to the film surface (direction t in FIG. 1), and the magnetic field generated thereby causes the magnetization of the first magnetic layer 1 or the second magnetic layer 2 to be reversed. Do it. A method for recording and reproducing information will be described later in detail. In this embodiment, since the first and second magnetic layers 1 and 2 have a closed magnetic circuit structure, the influence of the demagnetizing field can be eliminated, and the magnetization information can be stably recorded. Therefore, a 1-bit cell width can be reduced, a memory device with a high degree of integration can be realized, and furthermore, a stable recording / reproduction can be performed without a leakage magnetic field leaking to adjacent cells.

FIG. 2 is a diagram showing an example of a case where the memory device shown in FIG. 1 is actually configured as a memory. In FIG. 2, first, a memory element including first and second magnetic layers 1 and 2 and a non-magnetic layer 3 is provided on a semiconductor substrate in a pair with a driving transistor. This semiconductor substrate is
For example, it is made of a p-type semiconductor substrate, and the source and drain regions are n-type semiconductors. Signal is, for example, a source terminal of the driving transistor, Select is a gate terminal, and a drain terminal is electrically connected to, for example, a memory element. The other side of the memory element is connected to VDD. VDD is a power supply voltage, and by switching the polarity of VDD according to the recording information, the direction of the current of the memory element is changed to record “1” and “0” of the magnetization information. A large number of memory elements and driving transistors are arrayed vertically and horizontally on a semiconductor substrate, and are integrated as a highly integrated magnetic thin film memory.

In this embodiment, when recording information, there are two types of memory elements depending on whether the magnetization of the first magnetic layer 1 is inverted or the magnetization of the second magnetic layer 2 is inverted. Divided into First, the first type has a structure including a memory layer (first magnetic layer 1), a nonmagnetic layer 3, and a pinned layer (second magnetic layer 2). This is because the first magnetic layer 1
A memory layer for storing magnetization information, a second magnetic layer 2
Is used as a pinned layer for keeping the magnetization direction constant regardless of the magnetization information during storage, recording, and reproduction, and the first magnetic layer 1 is inverted by a recording current. . Reproduction of information is performed by absolute value detection without reversing the magnetic layer as described later.

The second type has a configuration including a detection layer (first magnetic layer 1), a nonmagnetic layer 3, and a memory layer (second magnetic layer 2). This is a case in which the first magnetic layer 1 is used as a detection layer that is inverted for relative detection at the time of reading, and the second magnetic layer 2 is used as a memory layer for storing magnetization information. Invert layer 2. In either case, the first magnetic layer 1 needs to have a low coercive force, and the second magnetic layer 2 needs to have a higher coercive force than the first magnetic layer 1.

Next, in the magnetic thin film memory element of the present embodiment, sufficiently stable recording can be performed by increasing the length t of the current path through which the recording current flows. This is the same in both the first type and the second type described above, and also in any of the later-described spin tunnel film configuration and spin scattering film configuration. Hereinafter, a specific configuration of the memory element will be described. First, in order to record information in a memory element, it is desirable to generate a magnetic field of at least 5 (Oe), and more preferably a magnetic field of 10 (Oe) 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 is difficult to hold recorded information stably. In order to obtain a large magnetic field, it is sufficient to apply a large amount of current.However, if the current density exceeds the limit current density of the wiring material, electromigration occurs and the wiring is easily disconnected, and when the current value increases, the power consumption of the memory element decreases. It gets bigger.

Among the wiring materials used in semiconductor devices, the limiting current density of a tungsten wire, which is a material having a relatively large limiting current density, is 20 mA / μm ² . Further, a current desirable for suppressing an increase in power consumption and heat generation of the device is about 1 mA or less. Here, FIG. 3 shows the above-described tungsten wire as a columnar conductor, the radius of the conductor as R, and the length as t. FIG. 4 shows FIG.
Shows the relationship between the radius R of the conductor and the magnetic field generated when a current is supplied in the longitudinal direction of the conductor. FIG.
In the figure, the generated magnetic field H is plotted against the radius R using the length t of the conductor as a parameter. The length t of the conductor is
0.01, 0.03, 0.05, 0.1, 0.2, 0.
It is 3 μm.

FIG. 5 shows the length t of the conductor and the maximum magnetic field H.
This shows the relationship with max. As apparent from FIGS. 4 and 5, in order to obtain a magnetic field of 5 (Oe) or more necessary for recording, the length t of the current path needs to be at least 0.05 μm or more. Also, as can be seen from FIG. 4, the longer the current path length t, the larger the current path radius R that can be used for recording.
It can be seen that the range of is expanded, and the manufacturing margin of the memory element increases. From the above results, in order to generate the magnetic field 5 (Oe) necessary for recording, the length of the current path t
Requires a length of 0.05 μm, preferably 0.1 μm.
μm or more, more preferably 0.15 μm or more, even more preferably 0.2 μm or more. Further, if the length t of the current path is too long, the film thickness increases, so that not only takes a long time to form the film but also the memory element is inclined not to be perpendicular to the semiconductor substrate of FIG. Erroneous recording such as erroneous recording in an adjacent memory element. Therefore, the length t of the current path is 2 μm or less, preferably 1 μm.
The thickness is more preferably 0.5 μm or less. Therefore,
The current path length t of the memory element of FIG.
The thickness is preferably not less than μm and not more than 2 μm.

FIG. 6 is a view showing a second embodiment of the present invention. In the embodiment of FIG. 1, the first magnetic layer 1, the non-magnetic layer 3, and the second magnetic layer 2 form a current path at the time of recording. In this embodiment, a good conductor 4 is further provided. That is,
When the thickness of the first and second magnetic layers 1 and 2 cannot be increased,
By providing the good conductor 4, the length of the current path is ensured. The first and second magnetic layers 1 and 2
The recording is performed on the first and second magnetic layers 1 and 2 by supplying a current in the vertical direction to the memory element of FIG. As shown in FIG. 6, the good conductor 4 is opposite to the end surface of the first magnetic layer 1 opposite to the surface in contact with the nonmagnetic layer 3 and the second magnetic layer 2 is opposite to the surface in contact with the nonmagnetic layer 3. It may be provided on the side surface, or may be provided on any one surface. By providing the good conductor 4 in this manner, resistance loss of the memory element is reduced, and power consumption can be reduced.

FIG. 7 is a diagram showing a third embodiment of the present invention. In this embodiment, a conductor 5 for supplying a recording current is provided at the center of the memory element. The conductor 5 is covered with an insulator 6 and has a higher conductivity than the first and second magnetic layers 1 and 2. The insulator 6 is the conductor 5
Is provided to prevent electrical contact with the magnetic layer. However, if the thickness of the insulator 6 is large, the distance between the conductor 5 and each of the magnetic layers increases, and the magnetic field applied to the magnetic layer decreases. It is better to be as thin as possible. In the present embodiment, the current is not supplied to the magnetic layer during recording, but is supplied to the conductor 5, so that the resistance is reduced, the power consumption can be reduced, and the responsiveness is excellent.

Next, a specific method for recording information on the magnetic thin film memory element will be described. First, in order to record information in a memory element, a current is supplied in a direction perpendicular to the film surface of the memory element. That is, a current is supplied so as to be perpendicular to the magnetization direction, the magnetization direction of the memory layer is determined by the magnetic field generated by the current, and information "0" and "1" is recorded. In this case, the direction of the magnetic field generated differs depending on the direction of the flowing current.For example, when a current is supplied from the top to the bottom of the memory element, a magnetic field is generated in a clockwise direction when viewed from above the memory element, and the magnetization is clockwise. Orient in the surrounding direction. On the other hand, when a current is supplied from below to above the memory element, a magnetic field is generated counterclockwise when viewed from above the memory element, and the magnetization is oriented in the counterclockwise direction.

When information is actually recorded, the first type "memory layer (first magnetic layer 1), non-magnetic layer 3, pinned layer (second magnetic layer 2)" as described above is used. The recording method differs between the second type “(detection layer (first magnetic layer 1), non-magnetic layer 3, and memory layer (second magnetic layer 2)”).
In the configuration of the type (1), the magnitude of the flowing current is
Of the memory layer (first magnetic layer 1) by generating a magnetic field smaller than the magnetization reversal magnetic field of the magnetic layer 2) and larger than the magnetization reversal magnetic field of the memory layer (first magnetic layer 1). The information "0" and "1" can be recorded in accordance with the direction of the magnetization. In the case of the second type, the magnitude of the current flowing is set so that a magnetic field larger than the magnetization reversal magnetic field of the memory layer (the second magnetic layer 2) is generated. Information "0" and "1" can be recorded according to the direction.

Next, a specific method for reproducing recorded information in the magnetic thin film memory will be described. First, information is reproduced in the direction perpendicular to the film surface of the memory element in the order of the first magnetic layer 1, the non-magnetic layer 3, the second magnetic layer 2, or the second magnetic layer 2,
The current is supplied in the order of the magnetic layer 2, the nonmagnetic layer 3, and the first magnetic layer 1. Then, the first magnetic layer 1 and the second
By measuring the resistance value between the magnetic layers 2, the magnetization information “0” and “1” is detected. That is, when the magnetization directions of the first magnetic layer 1 and the second magnetic layer 2 are the same, the resistance value between the first and second magnetic layers is small, and when the magnetization directions are opposite, the resistance value is large. Information is determined based on the difference between the resistance values. Alternatively, a current is supplied in the horizontal direction to the film surface of the memory element, and a difference in resistance value is similarly detected.

Further, the reading method is the same as the first method,
And the second type are different. First, in the case of the first type, a reading current smaller than that at the time of recording is supplied in a direction perpendicular to the film surface of the memory element, and the first and second currents are supplied.
The resistance value between the magnetic layers 1 and 2 is measured. In this case, since the magnetization of the second magnetic layer 2 is fixed, the resistance value between the first and second magnetic layers 1 and 2 corresponds to the magnetization direction recorded on the first magnetic layer 1. Changes, and the recorded information is reproduced by the resistance value. In this case, the magnetization reversal of the magnetic layer is not required.

On the other hand, in the case of the second type, there are three reading methods. First, a current is supplied in a direction perpendicular to the film surface of the memory element, and the detection layer (first magnetic layer) is inverted to initialize the magnetization in a certain direction. Then
A weak reading current is supplied so that the detection layer is not inverted in the direction perpendicular to the film surface of the memory element, and the resistance between the first and second magnetic layers 1 and 2 is measured. This method is effective for an element in which the coercive force of the detection layer is small and the magnetization is randomly oriented.

The other is to first measure the resistance of the memory element, and then supply a current perpendicular to the film surface of the memory element to orient the magnetization of the detection layer in a predetermined direction. Then, the resistance value of the memory element is measured. The magnetization information of the memory element can be detected depending on whether or not the resistance changes at this time. In this method, after the recording is completed, the magnetization directions of the detection layer and the memory layer are set so as to have a predetermined relationship. For example, the detection layer and the memory layer are magnetically interacted so that the parallel magnetization state is stabilized, and the resistance value measured first is the resistance value in the parallel magnetization state. This is achieved, for example, by setting the thickness of the nonmagnetic layer in the spin tunnel type to about 10 to 20 degrees.

In the last one, a current is supplied to the memory element from one direction in a direction perpendicular to the film surface, and a resistance change between the first and second magnetic layers 1 and 2 is read. Next, a current is supplied to the memory element in a direction opposite to the previous direction, a resistance change between the first and second magnetic layers 1 and 2 is read, and recorded information is determined based on the obtained resistance change. The magnitude of the current is a current for inverting only the detection layer. In either case, it is necessary to prevent the memory layer (second magnetic layer) from being inverted.

In this embodiment, as described above, during reproduction, a current is supplied perpendicularly to the film surface (CPP).
cular to the film Plane)-MR (Magneto-Resistanc)
e) Effect or CIP (Cur
(rent In-Plane to the film Plane)-The MR effect is used. As described above, the current flowing perpendicular to the film surface for determining the magnetization direction of the magnetic layer and the current flowing for measuring the resistance value of the memory element are the same current in the memory elements shown in FIGS. Take the route.

In the configuration of the memory element shown in FIG.
A current for determining the magnetization direction is passed through the conductor 5, and a current for measuring the resistance value is passed between the first magnetic layer 1 and the second magnetic layer 2.
The optimal embodiments in this case are shown in FIGS. 11 and 12 as fourth and fifth embodiments, respectively. FIG. 11 is a cross-sectional view of the memory element according to the fourth embodiment. In this configuration, when the magnetization direction is determined, the conductors 71 and 7 are used.
A current is applied to the conductor 5 by providing a potential difference between the two. When measuring the resistance value of the memory element, the electrodes 61 and 63 made of a conductor provided on the upper surface of the first magnetic layer 1 and the electrodes made of the conductor provided on the lower surface of the second magnetic layer 2 A current is passed between 62 and 64. This is the case of CPP detection, and is used when detecting both types of elements, spin tunneling and spin scattering, which will be described later.

The configuration of FIG. 12 is a cross-sectional view of the memory element of the fifth embodiment. In this configuration, the electrodes 62 and 64 of FIG. Supplies a current to the electrodes 61 and 63. In this case, C
This is IP detection, and is used when detecting an element of a spin scattering type described later. Since the spin scattering element has a thin magnetic layer and a small resistance value in CPP detection, it is preferable to use CIP detection.

Next, the materials of the first and second magnetic layers and the non-magnetic layer of the magnetic thin film memory element and their thicknesses will be described. Here, as the memory element film configuration, a spin tunnel film configuration and a spin scattering film configuration can be adopted, which are described in the first type “memory layer / non-magnetic layer / pin layer” and the second type. "Detection layer / Nonmagnetic layer / Memory layer"
Can be applied to any of the configurations. However, the spin tunnel film configuration and the spin scattering film configuration preferably use the spin tunnel film configuration. This is because in the spin tunnel film configuration, a large magnetoresistance (MR) ratio can be obtained, and the resistance can be increased to 1 kΩ or more, and the ON resistance (about 1 kΩ) of the semiconductor switching element can be reduced. This is because they are less susceptible to variations. Also,
As will be described later, the spin tunneling film can be employed in any of the embodiments of FIGS. 1, 6 and 7 because the magnetic film can be made relatively thick. Since it is difficult to increase the thickness of the layer to 0.05 μm or more, it is desirable to use the layer in the embodiment of FIG. 6 or FIG.

The first magnetic layer and the second magnetic layer are made of Ni, F
e or at least one of Co as a main component,
It is desirable to use it as an amorphous alloy containing oFe as a main component. For example, NiFe, NiFeCo, Fe,
It is made of a magnetic film such as FeCo, Co, and CoFeB.

(Material of First Magnetic Layer) The first magnetic layer
It has a lower coercive force than the second magnetic layer. For this reason, a soft magnetic film containing Ni is desirable for the first magnetic layer, and specifically, it is particularly desirable to use NiFe or NiFeCo as a main component. Further, a magnetic film of FeCo having a large Fe composition or an amorphous magnetic film having a low coercive force such as CoFeB may be used.

The atomic composition ratio of NiFeCo is NixFe
When yCoz is used, x is 40 or more and 95 or less, y is 0 or more and 40 or less, z is 0 or more and 50 or less, and preferably x is 50 or less.
90 or less, y is 0 or more and 30 or less, z is 0 or more and 40 or less, more preferably x is 60 or more and 85 or less, y is 10 or more and 25 or less, and z is 0 or more and 30 or less.

The atomic composition of FeCo is FexCo
_{In the case of 100-x} , x is 50 or more and 100 or less, preferably x is 60 or more and 90 or less. The atomic composition of the CoFeB _{is, (Co x Fe 100-x} ) when the _100-y B y, x is 86 or more 93 or less, y is good 10 to 25.

(Material of the Second Magnetic Layer)
It has a higher coercive force than the first magnetic layer. As an example, a magnetic film containing more Co than the first magnetic layer is desirable. NixFeyCoz is an atomic composition ratio, x
Is 0 or more and 40 or less, y is 0 or more and 50 or less, z is 20 or more and 95 or less, preferably x is 0 or more and 30 or less, y is 5 or more and 40 or less, z is 40 or more and 90 or less, and more preferably x is 5 or more. 20 or less, y is 10 or more and 30 or less, and z is preferably 50 or more and 85 or less. FexCo _100-x is an atomic composition ratio,
x is preferably 0 or more and 50 or less. Further, an additional element such as Pt may be added to the second magnetic layer for the purpose of improving the coercive force and improving the corrosion resistance.

In the case of the spin tunnel film configuration, the first and second
A thin insulating layer is used as the non-magnetic layer 3 between the magnetic layers 1 and 2, and when a current is supplied in the direction perpendicular to the film surface during reproduction, electron tunneling from the first magnetic layer 1 to the second magnetic layer 2 occurs. To get up. In such a spin tunneling type magnetic thin film memory element, the conduction state of a ferromagnetic metal causes spin polarization, so that the electronic states of the upward spin and the downward spin on the Fermi surface are different from each other. When a ferromagnetic tunnel junction composed of a ferromagnetic material, an insulator, and a ferromagnetic material is formed using a magnetic metal, conduction electrons tunnel while maintaining their spins. The probability changes, which manifests as a change in tunnel resistance. Thus, when the magnetization directions of the first magnetic layer 1 and the second magnetic layer 2 are the same, the resistance between the first and second magnetic layers 1 and 2 is small, and the first magnetic layer 1 and the second magnetic layer In the case where the magnetization directions of Nos. 2 and 3 are opposite, the resistance increases.

The density of states of the upward spin and the downward spin is
The greater the difference, the greater this resistance value,
Since a raw signal is obtained, the first magnetic layer 1 and the second magnetic layer 2
It is desirable to use a magnetic material having a high spin polarizability.
Specifically, the first magnetic layer 1 and the second magnetic layer 2
Select Fe with a large amount of vertical spin polarization on the surface,
Co is selected as the second component. More specifically, F
e, Co, Ni
It is desirable. Preferably, Fe, Co, FeCo,
NiFe, NiFeCo and the like are good. Specifically, Fe,
Co, Ni₇₂Fe ₂₈, Ni₅₁Fe₄₉, Ni₄₂Fe₅₈, N
i_{twenty five}Fe₇₅, Ni₉Fe₉₁And the like. Furthermore, the first
The magnetic layer 1 is made of NiFe, Ni to reduce coercive force.
FeCo, Fe, etc. are more desirable, and the second magnetic layer 2
Is a material containing Co as the main component to increase the coercive force.
Is desirable.

Next, the first magnetic layer 1 of the magnetic thin film memory element
And the thickness of the second magnetic layer 2 exceeds 100 ° and 5000
Å It is desirable to be less than or equal to. First, when an oxide is used for the non-magnetic layer 3, the magnetism at the interface of the magnetic layer on the non-magnetic layer side is weakened by the influence of the oxide, and this effect is large when the film thickness is small. . Second, when a nonmagnetic layer of aluminum oxide is formed by depositing Al and then oxidizing by introducing oxygen, aluminum remains in the order of several tens of degrees, and this effect increases when the magnetic layer is less than 100 degrees. This is because appropriate memory characteristics cannot be obtained. Third,
In particular, when the memory element is miniaturized to submicron,
Memory holding performance of the second magnetic layer 2
This is because the function of maintaining the constant magnetization of the above-mentioned is weakened. On the other hand, if the thickness is too large, the resistance of the cell becomes too large.
It is good to be less than 000Å.

Next, the material of the non-magnetic layer 3 will be described. First, the magneto-resistance effect by spin tunneling is used. The non-magnetic layer 3 must be an insulating layer because electrons hold a spin and tunnel. Must. Non-magnetic layer 3
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. Also,
As an example in which the nonmagnetic layer 3 is formed as an oxidized layer obtained by oxidizing a nonmagnetic metal film, a part of the Al film is oxidized in air to form an Al layer.
An example of forming a ₂ O ₃ layer is given. The non-magnetic layer 3 is made of an insulator, preferably, aluminum oxide AlO _x ,
It is desirable to use aluminum nitride AlN _x , silicon oxide SiO _x , and silicon nitride SiN _x . Also, NiO
_x may be the main component. This means that in order for spin tunneling to occur, it is necessary that an appropriate potential barrier exists for the energy of the conduction electrons in the first magnetic layer 1 and the second magnetic layer 2, but NiO _x is the main component. If
This is because it is relatively easy to obtain this barrier, and it is advantageous in production.

The thickness of the non-magnetic layer 3 is expressed by several tens.
It is a uniform layer of about Å, and the thickness of the insulating part is 5Å
It is desirable that the angle is not less than 30 °. That is, if it is less than 5 °, the first magnetic layer 1 and the second magnetic layer 2 may be electrically short-circuited, and 30 °
This is because if the value exceeds, electron tunneling becomes difficult to occur. Further, it is preferably 4 ° or more and 25 ° or less, more preferably 6 ° or more and 18 ° or less.

Next, in the case of a spin-scattering film configuration, a magnetoresistance effect caused by spin-dependent scattering is used. To obtain the magnetoresistance effect by spin-dependent scattering, a metal layer made of a good conductor is used as the nonmagnetic layer 3. Is good. The magnetoresistive effect due to the spin-dependent scattering is derived from the fact that the scattering of conduction electrons differs greatly depending on the spin. In other words, conduction electrons having spins in the same direction as the magnetization are not scattered so much that the resistance is small. However, conduction electrons having spins in the opposite direction to the magnetization have a large resistance due to scattering. Therefore, when the magnetization of the first magnetic layer 1 and the magnetization of the second magnetic layer 2 are in opposite directions, the resistance value becomes larger than when the magnetizations are in the same direction.

The first magnetic layer 1, the second magnetic layer 2, and the nonmagnetic layer 3 in the case of the spin-dependent scattering film configuration will be described.
First, the first magnetic layer 1 forms an annular loop with the second magnetic layer 2 and reads out magnetization information stored in the second magnetic layer 2 by utilizing the giant magnetoresistance effect. . It is desirable that the first magnetic layer 1 use Ni, Fe, Co as a main component or an amorphous alloy containing Co, Fe as a main component. For example, NiFe, N
Magnetic films such as iFeCo, FeCo, and CoFeB are exemplified. Further, an amorphous magnetic material such as CoFeB having a composition such as Co ₈₄ Fe ₉ B ₇ or Co ₇₂ Fe ₈ B ₂₀ may be used.

The second magnetic layer 2 is a magnetic layer mainly for storing magnetization information, and the direction of magnetization is determined according to information "0" and "1". The second magnetic layer 2 efficiently generates a giant magnetoresistance effect similarly to the first magnetic layer 1,
It is necessary to be able to store the magnetization state stably. As the second magnetic layer 2, a magnetic layer containing Fe and Co as main components is used, for example, a magnetic film of Fe, FeCo, Co or the like is used. Further, an additional element such as Pt may be added. Co
Coercive force decreases upon addition of Fe, the coercive force is increased upon addition of Pt, the second magnetic layer 2 for example by adjusting the elemental composition x and y as Co _100-xy Fe _x Pt _y coercivity Can also be controlled. Similarly, the coercive force of the first magnetic layer 1 can be adjusted by the composition ratio of Fe and Co and the amount of an additional element such as Pt.

It is necessary to set the thickness of the first magnetic layer 1 so that the scattering type giant magnetoresistance effect occurs efficiently. In the CPP-MR, the distance that can move while preserving the spin direction, that is, the spin diffusion length is an important factor. Specifically, if the thickness of the first magnetic layer 1 is significantly larger than the mean free path of electrons, the effect is reduced due to phonon scattering, so that the thickness is desirably at least 200 ° or less. More preferably, the angle is 150 ° or less. But,
If the thickness is too small, the resistance value of the cell decreases, the output of the reproduced signal decreases, and the magnetization cannot be maintained.

The thickness of the second magnetic layer 2 needs to be set so that the scattering type giant magnetoresistance effect can be efficiently generated, as in the case of the first magnetic layer 1.
Desirably, it is 0 ° or less. More preferably 150
Å The following is good. However, if the thickness is too small, the memory holding performance deteriorates, the output of the reproduced signal decreases, the resistance value of the cell becomes small, and the magnetization cannot be held.

The nonmagnetic layer 3 is made of a good conductor, and preferably uses Cu as a main component. Since the Fermi energy level is close to that of the magnetic layer and the adhesion is good, resistance is generated at the interface when the magnetization direction changes. This is convenient for easily obtaining a large magnetoresistance ratio. It is desirable that the thickness of the nonmagnetic layer 3 be 5 ° or more and 60 ° or less. Further, between the first magnetic layer 1 and the non-magnetic layer 3, between the second magnetic layer 2 and the non-magnetic layer 3, between the first magnetic layer 1 and the non-magnetic layer 3, and between the first magnetic layer 1 and the non-magnetic layer 3. It is desirable to provide a magnetic layer containing Co as a main component between the layer 2 and the nonmagnetic layer 3 because a higher magnetoresistance ratio and a higher S / N ratio can be obtained. Co in this case
The thickness of the layer containing as a main component is preferably 20 ° or less, and more preferably 5 ° or more for exhibiting the effect. Also,
In order to improve the S / N, the first magnetic layer 1 / non-magnetic layer 3 / second magnetic layer 2 / non-magnetic layer 3 may be stacked as one unit. The larger the number of sets to be stacked, the higher the MR ratio, which is preferable.
Since the R magnetic layer becomes thick and requires a large amount of current, the number of laminations is preferably 40 or less, more preferably about 3 to 20.

Control of coercive force of first and second magnetic layers 1 and 2
For example, when Fe is added to Co, the coercive force decreases.
The addition of Pt increases the coercive force.
Co _100-xyFe_xPt_yAdjust elemental composition x and y as
What is necessary is just to control the coercive force. In addition, the substrate temperature during film formation
The coercive force can also be increased by increasing the degree
Therefore, another method of controlling the coercive force is to control the substrate temperature during film formation.
May be adjusted. This method and the set of ferromagnetic thin films described above
It may be combined with a method of adjusting the composition.

The present invention is not limited to the structure shown in FIGS. 1, 6, and 7, and an antiferromagnetic layer is provided in contact with the surface of the second magnetic layer 2 on the side opposite to the nonmagnetic layer 3. This antiferromagnetic layer and the second
May be exchange-coupled to fix the magnetization of the second magnetic layer 2. The exchange coupling with the antiferromagnetic layer makes it possible to increase the coercive force of the second magnetic layer 2. In this case, since the same material can be used for the first magnetic layer 1 and the second magnetic layer 2, there is no need to sacrifice the MR ratio to increase the coercive force. The width expands. Nickel oxide NiO as the antiferromagnetic layer,
Iron manganese FeMn, cobalt oxide CoO, or the like can be used.

Next, as described above, information is recorded in the memory element by generating a magnetic field larger than the magnetization reversal magnetic field (coercive force) of the memory layer by the recording current. Therefore, the magnetic field required for recording depends on the coercive force of the memory layer. Hereinafter, in order to examine the magnitude of the magnetic field required for recording, the present inventor manufactured a memory element having memory layers having different coercive forces and tried an evaluation experiment.

In the configuration of the memory element shown in FIG.
12 μm conductor 5, inner diameter 0.14 μm, outer diameter 0.3
A memory cell consisting of a 0 μm NiFe detection layer / AlOx / Co memory layer was set to have a coercive force of 2, 4, 5, 1
100 pieces each were manufactured as 0 and 12 (Oe). "0" or "1" was recorded in these memory cells. The magnitude of the magnetic field generated from the current flowing through the write line was set to be almost equal to or slightly larger than the coercive force of the memory layer. The length of the conductor 5, that is, the length of the current path is 2 μm
And Thereafter, the information in each cell was reproduced, and the number of normal cells in which the recorded information was securely held and the number of defective cells in which the recorded information was lost were examined.

Table 1 shows the results. The error rate was defined as the ratio of defective cells to the total number of cells. The error rate was 1% when the magnitude of the magnetic field generated from the write line current was 5 (Oe), and was 0% when the magnitude was 10 (Oe) or more. Further, in 2 (Oe) and 4 (Oe), the error rates were 50 and 90%, respectively, and it was difficult to hold information. If the error rate is on the order of several percent, it is possible to accurately record and reproduce data with the error rate being 0% by adding redundancy by adding an error correction function as a memory. From the above results, the write current magnetic field is at least 5 (O
e) or more is required, and desirably 10 (Oe) or more is desirable.

[0056]

[Table 1] Next, in order to examine the upper limit of the length of the current path, the present inventor manufactured a memory cell having the same configuration as that described above, changing the length of the current path, and performed a recording / reproducing experiment. The length of the current path was 0.5, 1.0, 2.0, 3.0, and 4.0 μm, and 100 pieces each were manufactured. "0" or "1" was recorded in these memory cells, the magnitude of the magnetic field generated by the current flowing through the write line was 10 (Oe), and the coercive force of the memory layer was 8 (Oe). Table 2 shows the results. If the writing length is 2 μm, the error rate becomes 2%,
The value was 1% at 1.0 μm and 0% at 0.5 μm. It is presumed that the error rate deteriorated because a long current path was provided in the film thickness direction, resulting in erroneous recording in an adjacent cell.
From the above results, the length of the write line is at least 2 μm.
m is required, preferably 1.0 μm or less, and more preferably 0.5 μm or less.

[0057]

[Table 2]

[0058]

As described above, according to the present invention, the length of the current path for recording information by the generated magnetic field using the first and second magnetic layers having the closed magnetic circuit structure is set to 0.05 μm or more. When the thickness is 2 μm or less, not only can the cell width of one bit be reduced and the degree of integration can be increased, but also a sufficient magnetic field for recording can be generated, so that information can be stably recorded and information can be stably recorded. Can be saved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of a magnetic thin film memory of the present invention.

FIG. 2 is a diagram illustrating an example of a case where a memory is configured using the magnetic thin film memory of FIG. 1;

FIG. 3 is a diagram schematically showing a cylindrical current path.

4 is a diagram showing a relationship between a radius and a magnetic field in the current path in FIG. 3 using the length of the current path as a parameter.

5 is a diagram showing the relationship between the length of the current path in the current path of FIG. 3 and the maximum generated magnetic field.

FIG. 6 is a diagram showing a second embodiment of the present invention.

FIG. 7 is a diagram showing a third embodiment of the present invention.

FIG. 8 is a view showing a magnetic thin film memory element using a giant magnetoresistance effect of a conventional example.

FIG. 9 is a diagram for explaining a recording operation of the magnetic thin film memory element of FIG.

FIG. 10 is a diagram for explaining a reproducing operation of the magnetic thin film memory device of FIG. 8;

FIG. 11 is a sectional view showing a fourth embodiment of the magnetic thin film memory element of the present invention.

FIG. 12 is a sectional view showing a fifth embodiment of 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 4 Good conductor 5 Conductor 6 Insulator

Claims (8)

[Claims] A first magnetic layer having a closed magnetic circuit structure;
And a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the magnetic layer of
The second magnetic layer has an easy axis counterclockwise or clockwise,
A magnetic thin film memory element having a different resistance value depending on the relative angle of the magnetization direction of the first and second magnetic layers, wherein a current is supplied in a direction perpendicular to the film surfaces of the first and second magnetic layers. And a current path for recording information by a generated magnetic field having a length of 0.05 μm or more and 2 μm or less. 2. A surface of the first magnetic layer opposite to a surface in contact with the nonmagnetic layer, or at least one of a surface of the second magnetic layer opposite to a surface in contact with the nonmagnetic layer. Forming a good conductor layer having a higher conductivity than the first and second magnetic layers, and forming the current path including the first and second magnetic layers, the nonmagnetic layer, and the good conductor layer. The magnetic thin film memory element according to claim 1, wherein: 3. The semiconductor device according to claim 1, wherein the first and second magnetic layers and the non-magnetic layer are disposed at a substantially central portion of a film surface in a direction perpendicular to the film surface with respect to the first and second magnetic layers. 2. The magnetic thin film memory element according to claim 1, wherein a good conductor for supplying a current having a high conductivity is provided. 4. A method for recording information on a magnetic thin film memory element according to claim 1, wherein a current is supplied in advance vertically or vertically to a film surface of said magnetic thin film memory element, and By setting the magnitude so that a magnetic field larger than the magnetization reversal magnetic field of the second magnetic layer is generated, the direction of the magnetization of the second magnetic layer is set to a predetermined direction regardless of recording information, Supplying a current upward or downward in a direction perpendicular to the film surface of the magnetic thin film memory element according to recorded information, and having a magnitude of the current larger than the magnetization reversal magnetic field of the first magnetic layer; An information recording method, wherein information is recorded in the first magnetic layer in accordance with the direction of magnetization by setting a magnetic field smaller than the magnetization reversal magnetic field of the magnetic layer. 5. A first magnetic layer having a closed magnetic circuit structure, wherein the first magnetic layer has
And a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the magnetic layer of
The second magnetic layer has an easy axis counterclockwise or clockwise,
A method of recording information in a magnetic thin film memory element having different resistance values according to a relative angle of a magnetization direction of the first and second magnetic layers, wherein the information is recorded in a direction perpendicular to a film surface of the memory element. A current is supplied upward or downward in accordance with the current, and the magnitude of the current is set so as to generate a magnetic field larger than the magnetization reversal magnetic field of the second magnetic layer. An information recording method characterized in that information is recorded according to the direction of the information. 6. A first magnetic layer having a closed magnetic circuit structure and said first magnetic layer,
And a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the magnetic layer of
The second magnetic layer has an easy axis counterclockwise or clockwise,
A method of reproducing information recorded in a magnetic thin film memory element having different resistance values according to the relative angles of the magnetization directions of the first and second magnetic layers in accordance with the direction of magnetization of the second magnetic layer. A current is supplied in a direction perpendicular to the film surface of the magnetic thin film memory element to initialize the magnetization of the first magnetic layer in a predetermined direction, and in this state, the resistance value of the magnetic thin film memory element is initialized. An information reproducing method characterized in that recorded information is reproduced by measuring the information. 7. A first magnetic layer having a closed magnetic circuit structure, wherein
And a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the magnetic layer of
The second magnetic layer has an easy axis counterclockwise or clockwise,
The first and second magnetic layers have different resistance values depending on the relative angles of the magnetization directions, and when no magnetic field is applied, the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are parallel or opposite. A method of reproducing information recorded according to the direction of magnetization of the second magnetic layer in a magnetic thin film memory element placed in a parallel state, comprising first measuring a resistance value of the magnetic thin film memory element, Next, a current is supplied in a direction perpendicular to the film surface of the magnetic thin film memory element to orient the magnetization of the first magnetic layer in a predetermined direction, and then the resistance value of the magnetic thin film memory element is measured again. An information reproducing method characterized by reproducing recorded information by measuring a resistance change at this time. 8. A first magnetic layer having a closed magnetic circuit structure,
And a second magnetic layer having a closed magnetic circuit structure having a higher coercive force than the magnetic layer of
The second magnetic layer has an easy axis counterclockwise or clockwise,
A method of reproducing information recorded in a magnetic thin film memory element having different resistance values according to the relative angles of the magnetization directions of the first and second magnetic layers in accordance with the direction of magnetization of the second magnetic layer. Current is supplied to the second magnetic layer from one surface, the magnetization of the first magnetic layer is reversed, and the resistance value of the magnetic thin film memory element is measured. A current supplied from the first magnetic layer to invert the magnetization of the first magnetic layer to measure a resistance value of the magnetic thin film memory element, and reproduce recorded information based on the obtained resistance change. Method.