JP2000187976A - Magnetic thin film memory and its recording and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high integration degree by arranging plural layers of magnetic thin film memory elements which have magnetoresistance films each consisting of a first magnetic layer having low coercive force and a second magnetic layer having high coercive force laminated through a nonmagnetic layer and the films showing different resistance depending on the relative angle of the magnetization direction, and which have writing lines made of a conductive material near the magnetoresistance films. SOLUTION: The magnetic thin film memory elements having magnetoresistance films 1 in which information is to be recorded and writing lines 2 made of a good conductive metal arranged near the magnetoresistance films 1 are laminated in plural layers with the magnetoresistance films 1 electrically connected to one another in parallel on a substrate. A current is applied on the writing lines 2 in the perpendicular direction to generate a magnetic field which determines the magnetization direction of the magnetoresistance film. An insulating material 3 such as SiO2 and SiNx is preferably disposed between the magnetoresistance film 1 and the writing line 2 so as to prevent electric connection between the writing line 2 and the magnetoresistance film 1.

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, and more particularly, to a magnetic thin film memory with an improved degree of integration.

[0002]

2. Description of the Related Art Semiconductor memories include volatile memories, such as DRAM, which lose information when power is lost, and non-volatile memories, such as flash memories and ferroelectric memories, which retain information even when power is lost. .

In a DRAM or a ferroelectric memory, a portion for recording information is composed of a capacitor, and information is recorded according to the presence or absence of charges stored in the capacitor or the direction of polarization. One transistor is required. In a flash memory, a threshold voltage of a control gate of a transistor is changed depending on whether or not charges are accumulated in a floating gate. Therefore, at least one transistor is required for each memory cell.

On the other hand, a transistor is formed by implanting an impurity element such as boron or phosphorus into a Si crystal to form a p-type or n-type semiconductor. S at this time
The i-crystal needs to have a defect-free crystal structure or to have a film thickness that can withstand implantation of an impurity element in order to obtain a semiconductor property value having an appropriate band structure. For these reasons, it is extremely difficult to form a transistor by stacking transistors by further forming a Si film on the Si substrate on which the transistors have been formed.

Therefore, in a conventional semiconductor memory, at least one transistor is required for one memory cell, and it is not possible to form the transistors in an overlapping manner. Therefore, a plurality of memory cells are stacked in the film thickness direction. It was impossible to do.

[0006] A nonvolatile magnetic solid-state memory using a giant magnetoresistive film has recently been proposed. For example, USP. NO. 5,432,734 (JP-A-7-660)
33) shows a matrix configuration of the magnetic memory shown in FIG. 13A is a plan view and FIG. 13B is a cross-sectional view. The MR element 15 is composed of a giant magnetoresistive film having a nonmagnetic layer provided between two magnetic layers, and stores digital data according to the magnetization direction of the magnetic layer having a low coercive force.
The magnetic layer having a high coercive force is magnetized in a predetermined direction in advance. Recording is performed on a word line W1 provided above the magnetic film.
To W5 and the sense lines S1 to S5 to generate a large magnetization at the intersection of the word line and the sense line. The reproduction is performed by reversing the magnetization of the magnetic layer having the coercive force having the magnetization information and detecting the resistance change caused by the reversal. Therefore, it is necessary to perform rewriting after reproduction.

Further, USP. NO. 5,432,734
In a known solid-state magnetic memory using a giant magnetoresistive effect film, a memory element serially arranged on a substrate surface is arranged in only one stage, and a structure in which memory elements are stacked and a method of stacking the memory elements are disclosed. Not.

[0008]

Therefore, in the conventional semiconductor memory and the magnetic solid-state memory using the giant magnetoresistive film, one memory cell area is required for 1-bit recording. It was difficult to further increase. In view of this point, an object of the present invention is to realize a magnetic solid-state memory in which the degree of integration can be significantly improved as compared with the related art.

[0009]

According to the magnetic thin film memory of the present invention, a first magnetic layer having a low coercive force and a second magnetic layer having a high coercive force are laminated via a non-magnetic layer. 1
A magnetic thin film memory having a magnetoresistive film exhibiting a resistance value that differs depending on the relative angle between the direction of magnetization of the magnetic layer and the direction of magnetization of the second magnetic layer, and a write line formed of a good conductor provided near the magnetoresistive film A magnetic thin film memory is characterized in that at least two or more elements are stacked and arranged on a substrate, and the magnetoresistive films are connected in parallel.

The magnetic thin film memory is characterized in that the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are oriented antiparallel when the external magnetic field is zero.

The non-magnetic layer is made of a good conductor, and the first magnetic layer, the second magnetic layer, and the non-magnetic layer are connected in parallel.

Further, the non-magnetic layer comprises an insulating layer, and the first magnetic layer and the second magnetic layer are connected to different electrodes.

Further, the magnetoresistive film comprises a magnetic thin film memory wherein information is recorded by applying a recording magnetic field by a current flowing through at least two write lines provided above and below.

A circuit for detecting a resistance value of the magnetoresistive film is connected to an end of the magnetoresistive film connected in parallel,
A circuit for supplying a current is connected to the write line.

Further, the magnetic thin-film memories are arranged in a matrix on a substrate surface, and an end of the magnetoresistive film is electrically connected to a semiconductor element comprising a field-effect transistor or a diode. And a magnetic thin film memory.

A current is caused to flow through the write line, a magnetization direction of the second magnetic layer is determined by a magnetic field generated by the current, and the current direction of the write line is changed to “0”.
And the state of "1" is recorded.

Further, information recorded in the second magnetic layer is read by utilizing a resistance change caused by reversing the magnetization direction of only the first magnetic layer of the memory element by a magnetic field generated by a write current at the time of reproduction. And a reproducing method of the magnetic thin film memory.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The characteristics of each layer of a magnetoresistive film used in a magnetic thin film memory according to the present invention will be described below. The first magnetic layer and the second magnetic layer are desirably used with at least one of Ni, Fe, and Co as a main component, or as an amorphous alloy containing CoFe as a main component.
For example, NiFe, NiFeCo, Fe, FeCo, C
o, made of a magnetic film such as CoFeB.

(Material of First Magnetic Layer) The first magnetic layer is made of the second magnetic layer.
It has a lower coercive force than the magnetic layer. For this reason, the first magnetic layer is desirably a soft magnetic film containing Ni.
In particular, it is desirable to use NiFe and NiFeCo as main components. 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
In the case of yCoz, 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 5 or less.
0 or more and 90 or less, y is 0 or more and 30 or less, z is 0 or more and 40 or less
Hereafter, 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
When 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 CoFeB is (Cox
Fe100-x) 100-y By, x is 80 or more and 96
Hereinafter, y is preferably 5 or more and 30 or less. Preferably, x is 8
6 to 93 and y is preferably 10 to 25.

(Material of the Second Magnetic Layer) The second magnetic layer is made of the first magnetic layer.
It has a higher coercive force than the magnetic layer. As an example, a magnetic film containing more Co than the first magnetic layer is desirable.

NixFeyCoz is an atomic composition ratio, wherein x is 0 to 40, y is 0 to 50, z is 20 to 95, preferably x is 0 to 30;
y is 5 or more and 40 or less, z is 40 or more and 90 or less, more preferably x is 5 or more and 20 or less, y is 10 or more and 30 or less, and z is 50 or more and 85 or less.

FexCo100-x is an atomic composition ratio, and 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 controlling the coercive force and improving the corrosion resistance.

(Method of Coercive Force Control) When Fe is added to Co, the coercive force decreases, and when Pt is added, the coercive force increases. Therefore, the second magnetic layer is made of, for example, Co100-xy Fex.
The coercive force may be controlled by adjusting the element compositions x and y as Pty. The coercive force can also be reduced by adding Ni. Since the coercive force can also be increased by increasing the substrate temperature during film formation, another method of controlling the coercive force may be to adjust the substrate temperature for film formation. This method may be combined with the above-described method of adjusting the composition of the ferromagnetic thin film. The coercive force of the first magnetic layer can be adjusted by the film composition and the substrate temperature at the time of film formation in the same manner as described above. Also, increasing the film thickness increases the coercive force,
The coercive force difference may be provided by changing the film thickness.

(Thickness of First Magnetic Layer) The thickness of the first magnetic layer is set so that the scattering type giant magnetoresistance effect is efficiently generated. Specifically, if the thickness of the first magnetic layer is significantly larger than the mean free path of electrons, phonon scattering is exerted and the effect is reduced. Therefore, it is desirable that the thickness is at least 200 Å or less. More preferably, the thickness is 150 Å or less. However, if the thickness is too small, the resistance value of the cell becomes small, the output of the reproduction signal decreases, and the magnetization cannot be maintained. Therefore, the thickness is preferably 20 Å or more, and more preferably 80 Å or more.

(Thickness of Second Magnetic Layer) Like the first magnetic layer, the thickness of the second magnetic layer is at least 200 angstroms or less so that the scattering giant magnetoresistance effect can be efficiently generated. Desirably. More preferably, the thickness is 150 Å or less. However, if the thickness is too small, the memory retention performance deteriorates, the output of the reproduced signal decreases, the cell resistance decreases, and the magnetization cannot be maintained. Therefore, the thickness is preferably 20 Å or more, and more preferably 80 Å or more. desirable.

(Material and Film Thickness of Non-magnetic Layer) The non-magnetic layer is made of a good conductor, and is preferably made of Cu as a main component. When the direction changes, resistance is easily generated at the interface, which is convenient for obtaining a large magnetoresistance ratio. Further, it is desirable that the thickness of the nonmagnetic layer is not less than 5 angstroms and not more than 60 angstroms.

(Others) Between the first magnetic layer and the non-magnetic layer, between the second magnetic layer and the non-magnetic layer, or between the first magnetic layer and the non-magnetic layer, and between the second magnetic layer and the non-magnetic layer It is desirable to provide a magnetic layer containing Co as a main component between them, because the magnetoresistance ratio becomes high and a higher S / N ratio can be obtained. In this case, the thickness of the layer containing Co as a main component is preferably 20 Å or less. Further, in order to improve the S / N, the {first magnetic layer / non-magnetic layer / second magnetic layer / non-magnetic layer} may be formed as one unit and the units may be stacked. The larger the number of sets to be stacked, the higher the MR ratio, which is preferable. For this reason, the number of laminations is preferably 40 or less, more preferably about 3 to 20.

As another example of the memory element of the present invention, as described in the seventh embodiment of the present invention, a C
PP (Current Perpendicular to the film plane) −
There is a method using the MR effect. An example of this is a spin tunnel type GMR film. The spin tunnel film will be described below.

(Material and Film Thickness of Spin Tunneling Film) The magnetoresistance effect by spin tunneling has a structure of first magnetic layer / non-magnetic layer / second magnetic layer, but a thin insulating layer is formed on the non-magnetic layer. Used. Then, when a current is caused to flow perpendicular to the film surface during reproduction, a tunnel phenomenon of electrons from the first magnetic layer to the second magnetic layer occurs.

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

For the first magnetic layer and the second magnetic layer of the spin tunnel film, the same materials as those of the first magnetic layer and the second magnetic layer of the spin-dependent scattering film can be used. In order to obtain the resistance ratio, it is desirable to select Fe having a large amount of polarization of the upper and lower spins on the Fermi surface, and to select Co as the second component. Ni
May be added. Therefore, preferably, Fe, FeC
o, Co, NiFe, NiFeCo are preferred. As NiFe, specifically, Ni72Fe28, Ni51Fe49, Ni
42Fe58, Ni25Fe75, Ni9Fe91 and the like are obtained.

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

(Thickness of Magnetic Layer) The thickness of the first magnetic layer and the second magnetic layer of the magnetic thin film memory element of the present invention is desirably more than 100 Å and not more than 5000 Å.

First, when an oxide is used for the non-magnetic layer, the magnetism at the interface of the magnetic layer on the non-magnetic layer side is weakened due to the effect of the oxide. No.

Second, the aluminum oxide nonmagnetic layer is
In the case where oxygen is introduced and then oxidized after film formation, aluminum remains for several tens of angstroms, and this effect is increased when the magnetic layer is less than 100 angstroms, and appropriate memory characteristics can be obtained. Because there is no.

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

(Material of Non-Magnetic Layer) As described above, the magneto-resistance memory element of the present invention uses the magneto-resistance effect by spin tunneling, and the non-magnetic layer is insulated because electrons hold spins and tunnel. Must be layers.
The entire non-magnetic film may be an insulating layer or a part thereof may be an insulating layer. The magnetoresistive effect can be further enhanced by partially forming the insulating layer and minimizing its thickness. As an example of forming an oxide layer by oxidizing a nonmagnetic metal film, there is an example of forming an Al2 O3 layer by oxidizing a part of an Al film in air. The non-magnetic layer is made of an insulator,
Preferably, aluminum oxide AlOx, aluminum nitride AlNx, silicon oxide SiOx, silicon nitride S
Desirably, iNx. NiOx may be the main component. This is because in order for spin tunneling to occur, it is necessary that an appropriate potential barrier exists for the energies of conduction electrons in the first magnetic layer and the second magnetic layer. Is relatively easy and is advantageous in production.

(Non-Magnetic Layer Thickness) The non-magnetic layer is a uniform layer having a thickness of about several tens of angstroms, and the thickness of the insulating portion thereof is desirably 5 to 30 angstroms. This is because if the thickness is less than 5 angstroms, the first magnetic layer and the second magnetic layer may be electrically short-circuited.
If the thickness exceeds 0 angstroms, electron tunneling becomes difficult to occur. More preferably, 4
It is desirable that the thickness be in the range of Å to 25 Å. More preferably, the thickness is 6 angstroms or more and 18 angstroms.

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

[0043]

In the magnetic thin film memory according to the present invention, since the memory cells connected in parallel are stacked in the thickness direction of the substrate, the degree of integration is high and the recording capacity per unit area of the chip is large. Thin film memories can be realized without the need for complicated manufacturing processes. Further, since rewriting after reproduction is not required, there are advantages that the reproduction speed is high and the power consumption is small.

Further, even if the power is cut off, the information is not lost.
The number of times of rewriting is almost infinite, and there is no danger of losing the contents of the recording when radiation is incident.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a diagram showing a cross section of an example of a magnetic thin film memory according to the present invention. As shown in FIG. 1, the magnetic thin film memory of the present invention comprises a magnetic thin film memory element having a magnetoresistive film 1 on which information is recorded and a write line 2 made of a good conductor metal provided near the magnetoresistive film 1. , The magnetoresistive films 1 are electrically connected in parallel, and are laminated on a substrate in at least two stages. Electrodes 4 and 5 are provided at both ends of the magnetoresistive film 1, and a sense circuit (not shown) that can measure a resistance change between the electrodes 4 and 5 is connected to the electrodes 4 and 5. You. It is desirable that the electrodes 4 and 5 be good conductors having a low resistance value. This makes it possible to reduce the resistance value of a portion irrelevant to information storage, and to create a memory element having a good SN ratio. As a good conductor of the electrodes 4 and 5, a material having an electric resistance smaller than that of the magnetoresistive film, for example, a material containing aluminum, copper, or the like is desirable. Alternatively, a soft magnetic film such as NiF is formed on the electrodes 4 and 5 in order to improve the spin orientation by eliminating the adverse effect of spin curling generated on the end face particularly when the magnetoresistive film is miniaturized.
e, a perpendicular magnetization film of FeN, GdFe, or the like may be used, or a double structure having a soft magnetic film or a perpendicular magnetization film on the inside and a good conductor on the outside may be used.

A write line 2 is provided near the magnetoresistive film 1. The write line 2 is provided to allow a current to flow in a direction perpendicular to the plane of the paper and determine the magnetization direction of the magnetoresistive film by a magnetic field generated at that time. The magnetization direction is the direction of the current, and the magnitude of the magnetic field can be changed by the magnitude of the flowing current. It is desirable to provide an insulator 3 made of SiO ₂ , SiN _x or the like between the magnetoresistive film 1 and the write line 2. This is to prevent the write line 2 and the magnetoresistive film 1 from being electrically connected.

FIG. 2 shows the magnetoresistive film 1 shown in FIG. 1 in more detail. As shown in FIG. 2, the magnetoresistive film 1 has a first magnetic layer 11 having a low coercive force mainly in one direction in the film plane and a magnetic orientation in one direction mainly in the film plane. Second magnetic layer 12 having a high coercive force
Are laminated via the non-magnetic layer 13. The first magnetic layer having a small coercive force is provided for reading out the magnetization information stored in the second magnetic layer using the magnetoresistance effect. The second magnetic layer having a large coercive force is provided for storing magnetization information.

The magnetoresistive film 1 has a low resistance when the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 are parallel as shown in FIG. As shown in ()), when antiparallel, a high resistance value is shown. Therefore, “0”,
The digital information of “1” is read, for example, as shown in FIG.
As shown in (b), by making the magnetization direction correspond to the magnetization direction of the second magnetic layer 12, it is possible to detect digital information recorded by a difference in resistance value as described later. One bit of information is recorded for one write line. That is, if the number of the write lines 2 is n, n-bit information is stored.

When reproducing information recorded in the magnetic thin film memory element of the present invention, a weaker magnetic field is generated by applying a weaker current to the write line than in recording. The direction of magnetization of the second magnetic layer for storing magnetization information is not changed, and the first
Only the magnetization of the magnetic layer is reversed. For example, FIG.
As shown in (a), a pulse current that changes from positive to negative with time T is supplied to the write line 2 to change the direction of magnetization of the first magnetic layer 11 from left to right. In this case, when “0” is recorded in the second magnetic layer, the current is reduced as shown in FIG.
As shown in FIG. 11B, when the current flows from the paper surface toward the viewer (current direction 301) and then flows from the viewer toward the paper surface (current direction 302) as shown in FIG. 11C, the resistance value becomes low. To high values. When “1” is recorded in the second magnetic layer, the resistance changes from a high value to a low value because the state changes from FIG. 11D to FIG. 11E. Therefore, magnetization information recorded on the second magnetic layer can be detected by a change in resistance of the magnetoresistive film.

The coercive force of the first magnetic layer is 20 at 2 Oe or more.
The coercive force of the second magnetic layer is 5 Oe or more and 50 or less.
It is desirable to make it Oe or less. Further, it is desirable that the coercive force of the first magnetic layer be about half of the coercive force of the second magnetic layer.

The structure shown in FIG. 2 has a large coercive force.
Although the magnetic layer is provided on the write line side, the first magnetic layer having a small coercive force may be provided on the write line side. However, since a magnetic layer having a large coercive force requires a larger current for reversing the magnetization, it is more desirable to provide a second magnetic layer having a large coercive force on the write line side, since current consumption is reduced.

As shown in FIG. 1, in the structure of the present invention,
Compared with the conventional example shown in FIG. 13, since a plurality of bits can be recorded in one memory cell area with a simple structure, a high degree of integration can be achieved. Further, rewriting after reproduction is unnecessary.

(Embodiment 2) When the number of memory elements arranged in parallel is increased, the time constant is increased, the reading speed is reduced, and the thermal noise is increased as the overall resistance value is increased. In order to suppress this adverse effect, the number of memory elements arranged in one parallel structure is preferably 256 or less.

When the number of memory elements connected in parallel is increased, the rate of change in resistance at the time of detection decreases. For example,
The n magnetoresistive films are arranged in parallel, and one of the magnetoresistive films has a resistance value from the minimum value R1min to the maximum value R1ma.
x, and the resistance values of the remaining n-1 magnetoresistive films all have the same resistance value as R1max. At this time, the overall resistance value is changed from the minimum value RTmin to the maximum value RTmax.
, The resistance change rate MRT of all the memory elements connected in parallel defined by Expression (1) (Equation 1) becomes

[0056]

(Equation 1) Using the resistance change rate MR of one magnetoresistive film defined by Expression (2) (Equation 2), the overall change rate MRT is expressed by Expression (3) (Equation 3).

[0057]

(Equation 2)

[0058]

(Equation 3) That is, the resistance change rate decreases as the number of memory elements arranged in parallel increases. Further, assuming that the resistance values of the remaining n-1 magnetoresistive films are all R1min, the overall resistance change rate MRT is expressed by Expression (4) (Equation 4).

[0059]

(Equation 4) From the equations (2) and (4), in the case of the parallel arrangement, the memory element other than the memory element to be reproduced has a higher resistance value, the overall magnetoresistance ratio becomes higher, and the reproduction is slightly advantageous. It can be seen that it is. For this reason, when the memory element of the present invention uses a GMR film, for example, the first magnetic layer and the second magnetic layer
It is more desirable that the magnetization of the magnetic layer be in an anti-parallel state before reproduction. This may be achieved by, for example, causing a magnetic coupling between the first magnetic layer and the second magnetic layer such that the magnetization becomes antiparallel when the external magnetic field is zero.

FIG. 3 is a graph in which the vertical axis represents the MRT expressed by the equations (2) and (3), and the horizontal axis represents the number n of elements arranged in parallel. The upper part of the two plotted curves is the value of equation (2), and the lower one is the value of equation (3). MR is 0.2
And This is a typical value of the spin tunnel film.

From FIG. 3, the MRT is approximately 0.1 when n = 2 and 0.05 when n = 4. As mentioned earlier,
If a differential detection method in which the magnetization of the first magnetic layer is reversed left and right is used for reproduction, detection is possible as long as the effect of thermal noise does not occur even if the magnetoresistance ratio is small, but more stable. In order to realize accurate reproduction, the magnetoresistance ratio is preferably 0.04 or more, and more preferably about 0.1. Therefore, the number of memory elements connected in parallel is preferably 10 or less, and more preferably 4 or less.

In order to exhibit the effect of the present invention, at least two memory elements must be arranged in parallel. Therefore, the number of memory elements arranged in one parallel structure is at least 2 and at most 250, preferably at most 10 and more preferably at most 4.

Further, when comparing the case where memory elements are connected in parallel as in the present invention and the case where memory elements are connected in series as in the conventional example, a memory element with a shorter wiring delay and a higher speed can be used. Can be realized.

(Embodiment 3) FIG. 1 shows a case where one memory element is arranged in parallel on one stage of a magnetoresistive film. However, as shown in FIG. A plurality of memory elements may be arranged in series and further arranged in parallel. In this case, the degree of integration per unit area can be further increased. In FIG. 4, a part of the write line 2 is omitted by a dotted line.

However, if the number of elements arranged in series is increased too much, the magnetoresistance ratio becomes small. Therefore, the number of elements arranged in series in one stage is 10 or less, preferably 5 or less.
More preferably, about two are good.

(Embodiment 4) A magnetic thin film memory according to the present invention
As described above, at least 250 or less memory elements are arranged in a parallel structure. Therefore, several 100 Mbytes or several G in one memory chip
In order to achieve the capacity of bytes, it is desirable to form a matrix structure by arranging a large number of parallel structures shown in FIGS. 1 and 4 as one unit.

When this matrix structure is shown in a circuit diagram, for example, one unit of the parallel structure shown in FIG. 5 is arranged in a matrix and configured as shown in FIG. FIG.
In FIG. 7, most of the surrounding circuit structures are omitted, and a matrix of four parallel structures is shown. In order to eliminate the electric mutual interference between the parallel structures, it is desirable to connect a semiconductor element such as a transistor or a diode to each parallel structure. More preferably, the semiconductor element includes an active element such as a field effect transistor. It is desirable to provide an element. 5 and 6 show an example in which one end of the magnetoresistive film is connected to a transistor and the other end is connected to a power supply voltage VDD. Selection of each parallel structure is performed by turning on the transistor by applying a potential to a selection line connected to the gate electrode of the transistor. In this case, a voltage can be applied to the gate electrode of the transistor connected to the magnetoresistive film to select one of the many parallel structures. Further, in the selected parallel structure, a current is applied to a write line placed on a memory cell to be read to generate a magnetic field. The generated magnetic field reverses the magnetization of only the detection layer in the memory cell. This causes a change in the resistance value, and the change is amplified and detected by the sense circuit. Thus, information of a specific memory cell can be read from a large number of memory cells. The writing line is
By sharing with another parallel structure, the complexity of wiring can be eliminated.

FIGS. 7 and 8 show examples of cross-sectional views of a device structure provided with a transistor. FIGS. 7 and 8 show MOS (Metal-Oxide-Semiconductduct) structures in FIGS. 1 and 4, respectively.
or) shows a structure provided with a transistor. One end of the electrode in which the magnetoresistive films are arranged in parallel is electrically connected to the drain region of the field effect transistor, and the other end is connected to a constant voltage VDD. Further, source and drain regions are formed by forming n-type wells 9 and 10 on a p substrate, and a gate electrode 8 is provided to form a MOS (Metal-Oxide-Semiconductor) transistor.

FIG. 9 is a side view of the structure of FIG. Write lines are arranged across each parallel structure. FIG. 9 shows a case where the magnetoresistive film 1 is connected to the n-type well 10 of the MOS transistor via the connection line 5. The end of the write line is electrically connected to a switching element such as a transistor. A write line can be selected by these transistors.

(Embodiment 5) In a magnetic thin film memory according to the present invention in which magnetic thin film memory elements are arranged in a matrix, information is recorded by applying a current to the write line and the memory element body and generating the current. The magnetization direction of the second magnetic layer is determined by a magnetic field, and the state of “0” and “1” is recorded by changing the direction of current flow of the write line.

When information is recorded in the magnetic thin film memory of the present invention, a current is caused to flow through a write line laminated on the magnetoresistive element to be recorded to generate a magnetic field. This is called a write current. At the same time as applying a current to the write line, a current is also applied to the line of the magnetoresistive element to be recorded. This is called a sense current. To prevent this write current from leaking to the magnetoresistive element during recording, the write line
It is laminated on the magnetoresistive element via an insulator and is electrically insulated from the magnetoresistive element.

A magnetic field is applied by a write current and a sense current so as to be orthogonal to only the magnetoresistive element to be recorded. Since the magnetic field of the magnetoresistive element in the orthogonal portion is larger than that of the other portions, a specific one element can be selected from a large number of magnetoresistive elements to perform recording.

In the memory element of the present invention, two write lines are adjacent above and below the magnetoresistive film.
As shown in (1), if a current is supplied to the upper write line 2 and the lower write line 2 in opposite directions, the magnetic field that can be applied can be increased. In FIG. 10, the direction 201 of the current flowing in the front direction from the paper surface on the upper write line and the direction 202 of the current flowing in the paper surface on the lower write line are shown. This makes it possible to apply a strong rightward magnetic field to the magnetic field resistance film. By reversing the direction of the current, a strong leftward magnetic field can be applied. When two upper and lower write lines are used, one write line is added at the bottom. FIG. 7 shows such an example.

(Embodiment 6) As an example of the magnetoresistive film used in the magnetic thin film memory of the present invention, a film which produces a magnetoresistive effect by spin-dependent scattering can be cited. The magnetoresistance effect due to this spin-dependent scattering is derived from the fact that the scattering of conduction electrons differs greatly depending on the spin. That is, conduction electrons having spins in the same direction as the magnetization are not scattered so much that the resistance value is small. However, conduction electrons having spins in the opposite direction to the magnetization have a large resistance value due to scattering. For this reason, when the magnetizations of the first magnetic layer and the second magnetic layer are in opposite directions, the resistance value is larger than when the magnetizations are in the same direction. As a current direction during reproduction, a case where a current flows parallel to the film surface (CIP (Currennt Inplan to the film)
Plane)) and flow perpendicular to the film surface (CPP (Current Pe
rpendicular to the film Plane)), and in spin-dependent scattering, both CIP and CPP are possible.
It is desirable to use CIP because IP has a larger absolute value of the resistance and the output voltage becomes larger.

(Embodiment 7) As another example of the memory element of the present invention, CPP (Current Perpend
(icular to the film plane)-There is a method using the MR effect. FIG. 12 shows a memory element structure as this example. In this structure, the second magnetic layer 112 is connected to the electrode 5, and the first magnetic phase 111 is connected to the electrode 6.
Therefore, when a potential is applied between the electrode 4 and the electrode 5, a current flows through the magnetoresistive film in the order of the first magnetic layer 111, the nonmagnetic layer 113, and the second magnetic layer 112, or vice versa. An example of this is the above-described spin tunnel type GMR film.

COMPARATIVE EXAMPLE 1 A magnetic thin film memory device having a conventional structure does not have a magnetoresistive film laminated thereon as shown in FIG. 13, and therefore requires one magnetic thin film memory device area per bit. On the other hand, since the magnetic thin film memory element of the present invention is stacked, two or more bits of information can be stored in the area of one bit memory element.

For example, since the magnetic thin film memory elements shown in FIG. 1 are stacked in eight stages, it is possible to integrate 8 bits in a 1-bit cell area. If the number of laminations is increased, the degree of integration is further improved. Therefore, the degree of integration is dramatically improved as compared with a memory having a conventional structure.

[0078]

As described above, the present invention has an effect that a higher degree of integration can be realized as compared with a conventional semiconductor memory.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structural example of a magnetic thin film memory of the present invention.

FIG. 2 is a diagram showing an example of a magnetic thin film memory element used for the magnetic thin film memory of the present invention.

FIG. 3 is a diagram showing a change in the overall magnetoresistance ratio MRT when n memory elements are arranged in parallel.

FIG. 4 is a diagram showing an example of the structure of a magnetic thin film memory according to the present invention.

FIG. 5 is a diagram showing an example of a circuit of the magnetic thin film memory of the present invention.

FIG. 6 is a diagram showing an example of a circuit of a magnetic thin film memory according to the present invention.

FIG. 7 is a diagram showing an example of the structure of a magnetic thin film memory according to the present invention.

FIG. 8 is a diagram showing an example of the structure of a magnetic thin film memory according to the present invention.

FIG. 9 is a diagram showing an example of the structure of a magnetic thin film memory according to the present invention.

FIG. 10 shows an example of a magnetic thin film memory element used for the magnetic thin film memory of the present invention.

FIG. 11 is a diagram showing an example of a reproducing process of the magnetic thin film memory of the present invention.

FIG. 12 is a diagram showing an example of the structure of a magnetic thin film memory according to the present invention.

FIG. 13 is a view showing the structure of a conventional magnetic thin film memory.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 magnetoresistive film 2 write line 3 insulating film 4 electrode 5 electrode 7 source electrode 8 gate electrode 9 n-type region 10 n-type region 11 first magnetic layer 12 second magnetic layer 13 nonmagnetic layer 201, 301 Indicates the direction of current Symbols (indicating that the current flows from the paper toward the front) 202, 302 Symbols indicating the direction of the current (indicating that the current flows from the surface toward the paper) 111 First magnetic layer 112 Second magnetic layer 113 Nonmagnetic layer

Claims (13)

[Claims] 1. A first magnetic layer having a low coercive force and a second magnetic layer having a high coercive force are stacked via a non-magnetic layer, and the direction of magnetization of the first magnetic layer and the second magnetic layer are stacked. At least two or more magnetic thin film memory elements each having a magnetoresistive film having a resistance value that differs depending on the relative angle of the magnetization direction of the layer and a write line formed of a good conductor provided near the magnetoresistive film are stacked on a substrate. A magnetic thin film memory, wherein the magnetic resistance films are connected in parallel. 2. The magnetic resistance film according to claim 1, wherein
2. The magnetic thin film memory according to claim 1, wherein the magnetic thin film memory is connected in parallel. 3. The magnetic thin film memory according to claim 1, wherein 2 to 10 magnetoresistive films according to claim 1 are connected in parallel. 4. The magnetic thin film memory according to claim 1, wherein two to five magnetoresistive films according to claim 1 are connected in parallel. 5. The magnetic thin film memory according to claim 1, wherein the magnetoresistive films according to claim 1 are connected in series, and two or more of them are connected in parallel. 6. The magnetic thin film memory according to claim 1, wherein the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are oriented antiparallel when an external magnetic field is zero. Magnetic thin film memory. 7. The magnetic thin-film memory according to claim 1, wherein said non-magnetic layer is made of a good conductor, and said first magnetic layer, said second magnetic layer, and said non-magnetic layer are all arranged in parallel. A magnetic thin film memory connected to a magnetic thin film memory. 8. The magnetic thin film memory according to claim 1, wherein said non-magnetic layer comprises an insulating layer, and said first magnetic layer and said second magnetic layer are connected to different electrodes. A magnetic thin film memory characterized by the above. 9. The magnetic thin film memory according to claim 1, wherein a recording magnetic field is applied to said magnetoresistive film by a current flowing through at least two write lines provided above and below. A magnetic thin-film memory characterized in that information is recorded by using a magnetic thin-film memory. 10. The magnetic thin film memory according to claim 1, wherein a circuit for detecting a resistance value of said magnetoresistive film is connected to an end of said magnetoresistive film connected in parallel, A magnetic thin film memory, wherein a circuit for supplying a current is connected to the write line. 11. The magnetic thin film memory according to claim 1, which is arranged in a matrix on a substrate surface,
A magnetic thin film memory, wherein an end of the magnetoresistive film is electrically connected to a semiconductor element including a field effect transistor or a diode. 12. The magnetic thin film memory according to claim 1, wherein a current is passed through the write line, and a magnetization direction of the second magnetic layer is determined by a magnetic field generated by the current,
A recording method for a magnetic thin film memory, wherein the states of "0" and "1" are recorded by changing the current direction of the write line. 13. The magnetic thin-film memory according to claim 1, wherein a magnetic field generated by a write current at the time of reproduction reverses a magnetization direction of only the first magnetic layer of the memory element. A method for reading information recorded in the second magnetic layer by using the method.