JP2007305823A - Memory using magnetoresistance effect element and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems that a crosspoint type MRAM requires a selective transistor and a diode within the cell to suppress a read error caused by a sneak current which makes it difficult to downsize the cell and to rewrite by one directional driving current. <P>SOLUTION: This cross-point type memory is provided with its memory cell of only a magnetoresistance effect element having asymmnetric diversity and nonlinearity, and with its cell area small. Further, a nonvolatile memory which can be rewritten by only one directional driving current is provided by making the constitution of the magnetoresitance effect element and a combination of the driving current direction appropriate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic solid-state memory represented by a magnetic random access memory used for an information communication terminal and the like, and a driving method thereof.

In 1998, it was discovered that an Fe / Cr artificial lattice film composed of a magnetic film exchange-coupled via a nonmagnetic film exhibits a giant magnetoresistive element (GMR) (Non-Patent Document 1). A sensitive magnetic sensor and a reproducing magnetic head for hard disks were commercialized. As a new concept device, MRAM (Magnetic Randam Access Memory) using a GMR film has also been proposed (Non-patent Document 2). Subsequently, it was demonstrated that the tunnel magnetoresistive effect element (TMR) using an insulating film such as Al ₂ O ₃ as the nonmagnetic layer exhibits a large resistance change at room temperature (Non-patent Document 3). In order to realize the recording, the reproduction magnetic head for hard disk and MRAM have been developed. In addition, from the viewpoint of high sensitivity, a magnetic microcontact with two needle-shaped nickel (Ni) abutting or a magnetic microcontact with magnetite in contact is a ballistic type. It is disclosed as a magnetoresistive effect element (BMR) (Non-Patent Document 4, Non-Patent Document 5).

  A magnetic memory using such a magnetoresistive effect element has a relatively large read signal and can be formed of only metal, so that a memory cell can be formed simply by placing the element at a cross point of the wiring. An MRAM having such a structure is called a cross-point type MRAM.

However, the conventional crosspoint type MRAM has the following problems. The magnetoresistive effect element described above is a linear element whose current increases in proportion to the applied voltage, and is a resistance element whose resistance changes depending on the magnetization direction. Therefore, as shown in FIG. 11, when data written to the magnetoresistive effect element 12 of the selected cell is read, the bit line BL (b-1) is turned on by turning on the switches SW (a) and SW (b-1). ) And the word line WL (a) are selected, and a read current flows through the magnetoresistive effect element 12 in the direction of the solid line arrow. Due to the structure of the cross-point type memory, a plurality of elements other than the selected magnetoresistive effect element 12 are connected to the selected bit line BL (b-1) and word line WL (a). Current flows in the direction of the dotted arrow in the resistance effect elements 12a, 12b, and 12c. As a result, there is a problem that the ratio of the sneak current that does not pass through the shortest distance with respect to the read current flowing in the actual selected cell increases, and erroneous reading occurs. In addition, this problem becomes more apparent as the size of the memory array increases. In order to solve these problems, a magnetoresistive effect element having no non-linear characteristics and a transistor or a diode having non-linear characteristics are arranged together in a cell. For example, as shown in FIGS. 12 (a) and 12 (b), there is a measure to prevent a sneak current flowing in the direction opposite to the read current by using an element on the selection transistor or an amorphous silicon diode instead of the selection transistor. (Patent Document 1, Patent Document 2). As a driving method, a memory element using a spin injection magnetization reversal method capable of reversing the magnetization direction of a magnetic material by the torque of spin-polarized electrons has been proposed (Patent Document 3).
JP 2004-303801 A JP 2004-153248 A Japanese Patent Laid-Open No. 2003-204095 MNBaibich et.at., Phys.Rev.Lett.61 (1988) 2472. KTmRanmuthu et.al., IEEE Trans.on Magn. 29 (1993) 2593. T.Miyazaki et.al.JMMM 109,79 (1995) N. Garcia, M. Munoz, and Y.-W. Zhao, Physical Review Letters, Vol. 82, p2923 (1999) JJVersluijs, MABari and JMDCoey, Physical Review Letters, vol. 87, p26601-1 (2001) S. Boussaad and NJ Tao Applied Physics Letters 80 (2002) 2398

  However, as shown in Patent Document 1 and Patent Document 2, for the method of arranging the selection transistor in the memory cell, the area of the selection transistor becomes larger than the element, resulting in an increase in the cell area. There was also a problem that it would be a major obstacle to realizing a large-capacity memory. When an amorphous silicon diode is used, the area of the memory cell can be reduced because the area of the diode is smaller than that of the select transistor. However, the material used for MRAM is interface diffused by heat treatment at about 300 ° C. As a result, the characteristics deteriorate, and there is a problem that it is impossible to withstand the deposition temperature of amorphous silicon or polysilicon.

  Further, as a memory driving method, as shown in Patent Document 3, spin injection magnetization reversal can be used, and the direction of magnetization can be reversed by the direction of current to write information of “1” and “0”. When the spin injection magnetization reversal method is used as a driving method, when writing information “1” and “0” in the memory, it is necessary to switch the direction of the write current, and an amorphous silicon diode that allows current to flow only in one direction is used. The memory cell structure used cannot be used. Therefore, it is necessary to use a memory cell structure using a selection transistor, and it is difficult to increase the capacity due to an increase in the memory cell area.

In order to solve the above problems, the present invention comprises at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and the magnetic body is physically connected to the conductors. The resistance changes depending on the relative magnetization angle of the two magnetic bodies formed so as to sandwich the conductor having the magnetic characteristics, and the magnetic characteristics of the spin transmission path and the magnetization fixed body are It is possible to control ballistic conduction, which is mainly quantum conduction, by properly selecting the configuration, arrangement, shape, size, and material of the magnetic material configured to sandwich the conductor and the conductor. enable. Furthermore, a sneak current can be prevented without arranging a selection transistor or a diode in the cell by a magnetoresistive effect element having a nonlinear characteristic in a range where the quantum conductance shown as the element resistance is 0.01 or more and 0.3 G ₀ or less. A memory cell can be configured only from an effect element, an electrode for passing a current necessary for writing or reading to the magnetoresistive effect element, and a word line and a bit line joined to the electrode. Therefore, a large-capacity memory can be realized. The quantum conductance will be described. Quantum behavior occurs when the conductor through which electrons conduct becomes smaller than the mean free path of electrons. The quantum behavior is a phenomenon in which electrons can pass through the crystal without being scattered, and is called a ballistic conduction state. In this conduction state, the resistance value of the substance does not follow Ohm's law, and takes a value indicated by the jump energy rank indicated by the electron elementary quantity e and the blank constant h, as shown in Equation 1. This formula is called Landauer's formula, and its value is represented by quantum conductance G, and is used in the present invention in the same definition.

Further, the present invention is composed of at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and the magnetic body is in physical contact with the conductor, The resistance varies depending on the relative magnetization angle of two magnetic bodies formed so as to sandwich the conductor having magnetic characteristics, and a conductor having magnetic characteristics to be a spin transmission path and a magnetization fixed body, and its By appropriately selecting the configuration, arrangement, shape, size, and material of the magnetic body configured to sandwich the conductor, it is possible to control ballistic conduction which is mainly quantum conduction. Furthermore, it is a magnetoresistive effect element having non-linear characteristics in a range where the quantum conductance shown as element resistance is 0.01 or more and 0.3 G ₀ or less, and the constituent material is made of a metal material such as Ni. Usually, when an element is comprised with a metal material, an element has a linear characteristic. However, in the present invention it was found to have a non-linear characteristic have a configuration of only a metal material by optimizing the range quantum conductance of 0.01 G ₀ or more and 0.3 G ₀ or less. As a result, a sneak current can be prevented without arranging a selection transistor or a diode in the cell, and an electrode for flowing a current necessary for writing or reading with the magnetoresistive element, a word line joined to the electrode, and A memory cell can be configured only from the bit line, and the area of the memory cell can be reduced, so that a large capacity memory can be realized.

Further, the present invention is composed of at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and the magnetic body is in physical contact with the conductor, The resistance varies depending on the relative magnetization angle of two magnetic bodies formed so as to sandwich the conductor having magnetic characteristics, and a conductor having magnetic characteristics to be a spin transmission path and a magnetization fixed body, and its By appropriately selecting the configuration, arrangement, shape, size, and material of the magnetic body configured to sandwich the conductor, it is possible to control ballistic conduction which is mainly quantum conduction. Furthermore, the magnetoresistive effect element has a nonlinear characteristic in a quantum conductance range of 0.01 or more and 0.3 G ₀ or less shown as element resistance, and the magnetization free layer of the magnetoresistive effect element is at least 2 across the nonmagnetic layer. The two ferromagnetic layers are arranged such that the magnetization directions of the two ferromagnetic layers are antiparallel and have magnetic coupling. The ferromagnetic layer is arranged in an antiparallel state via the nonmagnetic layer of the free layer and has a magnetic coupling, so that spin-polarized electrons are always arranged through the nonmagnetic layer. Torque can be applied to either of the layers, and the free layer can be inverted with only one direction of current. Therefore, a memory cell can be configured only from the magnetoresistive element and an electrode for passing a current required for writing or reading, a word line and a bit line joined to the electrode, and the area of the memory cell can be reduced. A capacity memory can be realized.

Further, the present invention is composed of at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and the magnetic body is in physical contact with the conductor, The resistance varies depending on the relative magnetization angle of two magnetic bodies formed so as to sandwich the conductor having magnetic characteristics, and a conductor having magnetic characteristics to be a spin transmission path and a magnetization fixed body, and its By appropriately selecting the configuration, arrangement, shape, size, and material of the magnetic body configured to sandwich the conductor, it is possible to control ballistic conduction which is mainly quantum conduction. Furthermore, the magnetoresistive effect element has a nonlinear characteristic in a quantum conductance range of 0.01 or more and 0.3 G ₀ or less shown as element resistance, and the magnetization free layer of the magnetoresistive effect element is at least 2 across the nonmagnetic layer. The two ferromagnetic layers are arranged such that the magnetization directions of the two ferromagnetic layers are antiparallel and have magnetic coupling. In addition, by arranging the two ferromagnetic layers to have different thicknesses, the magnetization can be reversed with a smaller current than when the thicknesses are the same. A memory cell can be configured only from the magnetoresistive element using the above-described configuration and an electrode for passing a current necessary for writing or reading, a word line and a bit line joined to the electrode, and the area of the memory cell can be reduced. Since it can be made small, a large-capacity memory can be realized.

Further, the present invention is composed of at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and the magnetic body is in physical contact with the conductor, The resistance varies depending on the relative magnetization angle of two magnetic bodies formed so as to sandwich the conductor having magnetic characteristics, and a conductor having magnetic characteristics to be a spin transmission path and a magnetization fixed body, and its By appropriately selecting the configuration, arrangement, shape, size, and material of the magnetic body configured to sandwich the conductor, it is possible to control ballistic conduction which is mainly quantum conduction. Further, a magnetoresistance effect element having a nonlinear characteristic in a range quantum conductance of 0.01 or more and 0.3 G ₀ or less, shown as element resistance, magnetization fixed layer of the magnetoresistive element having an antiferromagnetic layer. By using this configuration, a change in magnetoresistance can be obtained stably, and a read signal can also be obtained stably. A memory cell can be configured only from the magnetoresistive element using the above-described configuration and an electrode for passing a current necessary for writing or reading, a word line and a bit line joined to the electrode, and the area of the memory cell can be reduced. Since it can be made small, a large-capacity memory can be realized.

Further, the present invention is composed of at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and the magnetic body is in physical contact with the conductor, The resistance varies depending on the relative magnetization angle of two magnetic bodies formed so as to sandwich the conductor having magnetic characteristics, and a conductor having magnetic characteristics to be a spin transmission path and a magnetization fixed body, and its By appropriately selecting the configuration, arrangement, shape, size, and material of the magnetic body configured to sandwich the conductor, it is possible to control ballistic conduction which is mainly quantum conduction. Further, a magnetoresistance effect element having a nonlinear characteristic in a range quantum conductance of 0.01 or more and 0.3 G ₀ or less, shown as element resistance, magnetization fixed layer of the magnetoresistive element having an antiferromagnetic layer. By using this configuration, a change in magnetoresistance can be obtained stably, and a read signal can also be obtained stably. In addition, the non-magnetic layer is interposed between at least two ferromagnetic layers, and the two ferromagnetic layers have antiferromagnetic coupling. With this configuration, it is possible to stably fix the magnetization direction of the magnetization fixed layer even if the element is small, so that a change in magnetoresistance can be stably obtained, and a read signal can also be stably obtained. A memory cell can be configured only from the magnetoresistive element using the above-described configuration and an electrode for passing a current necessary for writing or reading, a word line and a bit line joined to the electrode, and the area of the memory cell can be reduced. Since it can be made small, a large-capacity memory can be realized.

Further, the present invention is composed of at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and the magnetic body is in physical contact with the conductor, A magnetoresistive effect having a non-linear characteristic in which a resistance varies depending on a magnetization relative angle between two magnetic bodies formed so as to sandwich a conductor having the magnetic characteristics, and a quantum conductance is in a range of 0.01 to 0.3 G ₀ In a memory cell comprising an element, the magnetoresistive element and an electrode for flowing a current required for writing or reading to the magnetoresistive effect element, a word line joined to the electrode, and a bit line, The magnetoresistive effect element constituting the memory cell is characterized in that a current is passed in only one direction to change the magnetization direction and change the element resistance.

Further, the present invention is composed of at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and the magnetic body is in physical contact with the conductor, A magnetoresistive effect having a non-linear characteristic in which a resistance varies depending on a magnetization relative angle between two magnetic bodies formed so as to sandwich a conductor having the magnetic characteristics, and a quantum conductance is in a range of 0.01 to 0.3 G ₀ In a memory cell comprising an element, the magnetoresistive element and an electrode for flowing a current required for writing or reading to the magnetoresistive effect element, a word line joined to the electrode, and a bit line, The magnetoresistive effect element constituting the memory cell is characterized in that a current is passed in only one direction to change the magnetization direction and change the element resistance. Further, by adopting a configuration in which current flows in a direction perpendicular to the film surface, the area of the memory cell can be reduced, so that a large capacity memory can be realized.

  In addition, the present invention is characterized in that it has a memory array configuration having a cross point structure in which word lines and bit lines are arranged in a matrix and the memory cells are arranged at positions where they cross each other. A memory cell can be configured only from the magnetoresistive element using the above-described configuration and an electrode for passing a current necessary for writing or reading, a word line and a bit line joined to the electrode, and the area of the memory cell can be reduced. Since it can be made small, a large-capacity memory can be realized.

  In addition, the memory array of the present invention is characterized in that it is three-dimensionally stacked via an insulating layer. A memory cell can be configured only from the magnetoresistive element using the above-described configuration and an electrode for passing a current necessary for writing or reading, a word line and a bit line joined to the electrode, and the area of the memory cell can be reduced. Can be small. Furthermore, a large-capacity memory can be realized by three-dimensionally stacking the memory array via an insulating layer.

  By using a magnetoresistive effect element having a non-linear and non-linear VI characteristic of the present invention, it becomes possible to suppress a sneak current that causes erroneous reading and erroneous writing operations. Therefore, the magnetoresistive effect element and its magnetoresistance A cross-point type memory cell that can be configured by only word lines and bit lines for writing and reading by passing current through the effect element can be configured. Further, with the above configuration, the area of the memory cell can be reduced, so that a high density memory can be realized.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a magnetoresistive element (hereinafter sometimes simply referred to as “element”) of the present invention. The element comprises two ferromagnets 1a, 1a 'and one or more conductors 3 having magnetic properties formed so as to be sandwiched between the ferromagnets, and an insulation arranged to enclose the conductors 3. Composed of layer 2. The ferromagnets 1a and 1a 'are in physical contact with the conductor 3, and the resistance changes depending on the relative magnetization angle of the two ferromagnets 1a and 1a' formed so as to sandwich the conductor 3 having magnetic properties. and, and quantum conductance is a magnetic resistance effect element 1 is 0.01 or more and 0.3 G ₀ or less. 2 (a) and 2 (b) show how the rate of change in resistance changes depending on the relative magnetization angle of the two ferromagnets 1a and 1a 'arranged with the conductor 3 having magnetic properties in between. FIG. In FIG. 2 (a), the magnetization directions of the two ferromagnetic bodies 1a and 1a ′ are parallel to each other with the conductor 3 having magnetic characteristics in between. At this time, when a current is passed from one ferromagnet 1a ′ to the other ferromagnet 1a passing through the conductor 3, electrons are scattered because the magnetization directions of the two ferromagnets 1a and 1a ′ are parallel. Pass without. On the other hand, in FIG. 2B, the magnetization directions of the two ferromagnetic bodies 1a and 1a ′ are antiparallel across the conductor 3 having magnetic characteristics. At this time, when a current is passed from one ferromagnet 1a ′ to the other ferromagnet 1a passing through the conductor 3, the magnetization directions of the two ferromagnets 1a and 1a ′ are antiparallel, so that electrons are scattered. Is done. As a result, when the magnetization directions of the two ferromagnets 1a and 1a ′ are parallel, the resistance is low, and when the magnetization directions are antiparallel, the resistance is high. The configuration of the magnetoresistive effect element 1 is not limited to the configuration shown in FIG. 1, and as shown in FIGS. 3 (a) and 3 (b), the two ferromagnetic bodies 1a, 1a ′, 1c, and 1c ′ are conductive. The material constituting the body 3 may be different. FIG. 4 shows the VI characteristics of the magnetoresistive element 1 of the present invention. As shown in FIGS. 2A and 2B, the voltage application direction and the current direction are positive (+) from the top to the bottom, and negative (−) from the bottom to the top. Also from the VI characteristics shown in FIG. 4, the magnetoresistive effect element 1 exhibits non-linear characteristics and has asymmetry. In addition to exhibiting non-linear characteristics, this asymmetry can prevent a sneak current without providing a selection transistor or diode in the cell. As a method for reversing the magnetization direction of the magnetization free layer 6 constituting the magnetoresistive effect element 1 of the present invention, a spin injection magnetization reversal method is used in which the magnetization direction is rotated by a torque applied to magnetization by spin-polarized electrons. Using this induced magnetization switching method, the magnetization of the magnetization free layer 6 of the magneto-resistance effect element 1 having a quantum conductance ranging from V-I characteristic 0.01G ₀ ~0.3G ₀ to asymmetry and nonlinearity is obtained by The current density I required for reversal was I> 10 ⁷ A / cm ² . Table 1 shows values obtained by converting this current density into a current value required for each quantum conductance and obtaining an applied voltage corresponding to the current. As can be seen from this table, the voltage difference between the applied voltage (positive direction) and the applied voltage (negative direction) can be secured to 0.1 V or more, so if a current is passed during writing or reading of information, the sneak current can be suppressed. Therefore, erroneous reading and erroneous writing can be reduced.

  As shown in FIG. 5, the memory cell structure can be configured only by the magnetoresistive effect element 1, the word line, and the bit line, and the size of the cell can be reduced. The material constituting the magnetoresistive element 1 is not a problem as long as the electron conducting portion is a material such as Ni.

Next, a method for producing the magnetoresistive effect element 1 of the present invention will be described with reference to FIGS. First,
A multilayer film of ferromagnetic layer 1a ′ / insulating layer 2 / ferromagnetic layer 1a as shown in FIG. 6 (a) is formed by a sputtering apparatus. The multilayer film is patterned into an element shape by photolithography, and processed into a shape as shown in FIG. 6B using an ion milling apparatus. FIG. 6 (b) is a view of the element formed on the substrate as viewed from above. In the element pattern, a protruding portion 11 is provided in a part of the patterned element for producing the conductor 3 in the next step. FIG. 6 (c) shows a cross-sectional view of the element viewed from the direction of the arrow shown in FIG. 6 (b). For the production of the conductor 3, the “self-terminated electrochemical method” which is an atomic scale point contact production method invented by Dr. Tao et al. Was used (Non-patent Document 6). This method is an improvement of electroplating using an electrochemical method, and a simple explanatory diagram is shown in FIG. 6 (d). Power V _0, the gap resistance R _GAP, the gap voltage V _GAP, external resistor R _ext, when its external resistor V _ext, gap voltage V _GAP is shown as the number 2.

When the width of the gap is wide, the gap resistance R _gap shows a very large resistance of 10 ⁹ or more, R _g >> R _ext , and the relationship between the applied power supply voltage V ₀ and the gap voltage V _gap is expressed by Equation 3. It is.

At that time, the deposition rate is maximum. As precipitation proceeds and the gap width narrows, a tunnel current flows out and a voltage drop occurs, so that the gap resistance R _gap decreases and the gap voltage V _gap also decreases. When the gap resistance R _gap is very small compared to the external resistance R _ext , that is, when R _gap << R _ext , the gap voltage V _gap ˜0. That is, the gap width (point contact width) can be controlled depending on the external resistance R _ext . Using this production method, a point contact was produced this time. As shown in FIG. 6 (e), a power source was connected to an element manufactured by photolithography, and the junction was controlled with an external resistance of 12.7 kΩ. The electrolytic solution was a nickel sulfate aqueous solution with a pH of 3.3, and was prepared at a constant applied voltage of -1.0V. When -1.0 V is applied to the power source, nickel gradually precipitates, and the joining is completed in about several minutes, and the conductor 3 as shown in FIG. 6 (f) is manufactured. This time, the protruding part 11 was prepared in advance, and the conductor 3 was prepared on the side of the element. However, a through hole was made in the insulating layer 2, and the conductor was formed in the through hole by the same electroplating. The same effect can be obtained even if 3 is manufactured.

(Embodiment 2)
FIG. 7 (a) is a diagram showing the magnetoresistive element 1 constituting the memory cell of the present invention. In the magnetoresistive effect element 1, the magnetization fixed layer 7 is composed of a metal material 1a ′ including Ni and an antiferromagnetic material 5. The soft magnetic material 4 constituting the magnetization free layer 6 is preferably a soft magnetic material containing at least Fe, Co, and Ni. The antiferromagnetic material 5 is preferably a low resistance metal antiferromagnetic material such as IrMn (iridium manganese). By using the antiferromagnetic material 5 for the magnetization fixed layer 7 shown in FIG. 7 (a), the magnetization fixed layer 7 can stably fix the magnetization direction against disturbances such as heat. On the other hand, the magnetization free layer 6 is composed of two soft magnetic layers 4 and 4 ′ with a nonmagnetic layer 8 interposed therebetween, and the two soft magnetic layers 4 and 4 ′ are arranged in anti-parallel directions and magnetically coupled. It is characterized by having. FIGS. 7B and 7C show the configuration of the magnetoresistive effect element 1 when the magnetization fixed layer 7 uses a multilayer structure having antiferromagnetic coupling instead of an antiferromagnetic material. As shown in FIG. 7B, the magnetization fixed layer 7 is composed of at least two ferromagnetic layers 1a ′ via a nonmagnetic layer 8, and the two ferromagnetic layers 1a ′ have antiferromagnetic coupling. It is a sign that you are doing. With this multilayer structure having antiferromagnetic coupling, the magnetization fixed layer 7 can be stably held even when the size is reduced, and the memory cell can be downsized. Further, as the magnetization fixed layer 7, as shown in FIG. 7 (c), the ferromagnetic layer 1a ′ is not a multilayer structure, but the ferromagnetic layers 9 and 9 ′ different from the ferromagnetic layer 1a ′ are used. The multi-layer structure can further improve the stability of the magnetization fixed layer and reduce the size of the memory cell.

(Embodiment 3)
FIGS. 8A, 8B, and 8C are diagrams for explaining a method of driving the magnetoresistive effect element 1 of the present invention. As a driving method, a spin injection magnetization reversal method is used in which magnetization is rotated by the torque effect of spin-polarized electrons. In FIGS. 8 (a), (b), and (c), solid arrows indicate the current direction. On the other hand, the dotted arrow indicates the direction in which electrons flow. In FIGS. 8 (a), (b), and (c), the current direction is positive (+) from the top to the bottom of the drawing, and electrons move from bottom to top. At this time, an electron having a spin in the same direction as the magnetization direction of the magnetization fixed layer 7 is e- ↑, and an electron having a spin in the opposite direction to the magnetization fixed layer 7 is e- ↓.

  In the configuration of FIG. 8 (a), when current flows from top to bottom (electrons move from bottom to top), an electron e- ↑ having a spin in the same direction as the magnetization fixed layer 7 passes through the conductor 3, Torque is applied to one soft magnetic layer 4 ′ of the magnetization free layer 6, and when the current exceeds a certain critical value, the magnetization direction is reversed in the same direction as the magnetization fixed layer 7. Since the other soft magnetic layer 4 of the magnetization free layer 6 is magnetically weakly antiferromagnetically coupled to the soft magnetic layer 4 ′ via the nonmagnetic layer 8, when the soft magnetic layer 4 ′ is reversed, the other soft magnetic layer 4 ′ The soft magnetic layer 4 is also reversed. Further, the ferromagnetic layer 1a is also magnetically induced in the soft magnetic layer 4 and reversed in the same direction as the soft magnetic layer 4, and changes as shown in FIG. 8 (b). In the state shown in FIG. 8 (b), when a current is passed again in the same direction, an electron e- ↑ having a spin in the same direction as the magnetization fixed layer 7 passes through the conductor 3, and one soft magnetic layer of the magnetization free layer 6 Torque is applied to 4 and the ferromagnetic layer 1a, and when the current exceeds a certain critical value, the magnetization direction is reversed in the same direction as the magnetization fixed layer 7. Since the soft magnetic layer 4 is magnetically weakly antiferromagnetically coupled to the soft magnetic layer 4 ′ via the nonmagnetic layer 8, when the soft magnetic layer 4 is inverted, the other soft magnetic layer 4 ′ is also inverted. As shown in 8 (c), the magnetization is reversed. By using the configuration of the magnetoresistive effect element described above, a nonvolatile memory that can be driven with a current in only one direction can be realized.

(Embodiment 4)
FIGS. 9 (a), (b), and (c) are diagrams for explaining a method of driving the magnetoresistive effect element 1 of the present invention. As a driving method, a spin-injection magnetization reversal method is used in which magnetization is rotated by the torque effect of spin-polarized electrons as in the third embodiment. In FIG. 9 (a), (b), and (c), the practice arrow indicates the current direction. On the other hand, the dotted arrow indicates the direction in which electrons flow. In FIGS. 9A, 9B and 9C, the current direction is positive (+) from the top to the bottom in the same manner as in the third embodiment, and electrons move from the bottom to the top. An electron having a spin in the same direction as the magnetization direction of the magnetization fixed layer 7 is denoted by e- ↑, and an electron having a spin opposite to the magnetization fixed layer 7 is denoted by e- ↓. The difference from the third embodiment is the direction of current and the junction direction of the point contact of the conductor 3.

  In the configuration of FIG. 9 (a), when the current flows from bottom to top (electrons move from top to bottom), among the electrons flowing from the magnetization free layer 6, electrons having the spin in the same direction as the magnetization fixed layer 7e -↑ can pass through the conductor 3, but electrons e- ↓ having a spin opposite to that of the magnetization fixed layer 7 are reflected at the interface between the conductor 3 and the ferromagnetic layer 1a 'of the magnetization fixed layer 7. This reflected electron electron e- ↓ is combined with the magnetization of the ferromagnetic layer 1a and the soft magnetic layer 4 of the magnetization free layer 6, and the magnetization of the ferromagnetic layer 1a and the soft magnetic layer 4 is changed to the magnetization of the magnetization fixed layer 7. Antiparallel. As a result, the state changes to that shown in FIG. 9 (b). In the state shown in FIG. 9 (b), when a current is passed again in the same direction, an electron e- ↑ having a spin in the same direction as the magnetization fixed layer 7 can pass through the conductor 3, but a spin in the opposite direction to the magnetization fixed layer 7 The electron e- ↓ having is reflected at the interface between the soft magnetic body 4 and the nonmagnetic layer 8 of the magnetization free layer 6. The reflected electron electrons e− ↓ are combined with the magnetization of the soft magnetic layer 4 ′ of the magnetization free layer 6 so that the magnetization of the soft magnetic layer 4 ′ is antiparallel to the magnetization of the magnetization fixed layer 7. Since the soft magnetic layer 4 ′ is magnetically weakly antiferromagnetically coupled to the soft magnetic layer 4 via the nonmagnetic layer 8, when the soft magnetic layer 4 ′ is inverted, the other soft magnetic layer 4 is also inverted. The magnetization is reversed as shown in 9 (c). By using the configuration of the magnetoresistive effect element described above, a nonvolatile memory that can be driven with a current in only one direction can be realized.

  The combination of the configuration of the magnetoresistive effect element 1 that can be driven by a current in one direction (the junction direction of the point contact of the conductor 3) and the current direction is shown in FIG. 8 (a) in addition to the third and fourth embodiments. ), (B), and (c) in the configuration of the magnetoresistive effect element 1, and the current direction in the configurations of the magnetoresistive effect element 1 in FIGS. 9 (a), (b), and (c) There are two combinations of the opposite. These remaining two types can be driven with a current in one direction, but the current density required for reversing the magnetization is higher than that shown in FIGS. 8 and 9, and it has non-linear characteristics. It was found that the sneak current cannot be suppressed because the asymmetry effect as shown in FIG. 4 is small. Therefore, a combination of the element configuration and the current direction of the magnetoresistive effect element 1 of FIGS. 8 and 9 is desirable.

(Embodiment 5)
FIG. 10 shows a configuration in the case where memory cells having the magnetoresistive effect element 1 of the present invention are arranged in a 3 × 3 matrix. As shown in FIG. 10, the word lines and the bit lines are arranged in a matrix and have a cross point structure in which only the magnetoresistive effect element 1 is arranged at a position where they cross each other. In the memory cell of the present invention, the magnetoresistive element 1 has asymmetry and nonlinearity in the VI characteristic shown in FIG. As a result, a sneak current at the time of reading or writing that has occurred in the cross-point type MRAM can be suppressed, and reduction of erroneous reading and erroneous writing can be realized. Further, since the selection transistor and the diode need not be arranged in the cell, it can be realized including the reduction of the cell area.

  Further, a memory using the memory cell of the present invention uses a spin injection magnetization reversal method using spin-polarized electrons as a driving method. It has been found that the direction of magnetization can be reversed by a current in one direction by optimizing the combination of the element configuration of the magnetoresistive effect element 1 in FIG. 8 and FIG. As a result, it is not necessary to use a variety of power sources for the driving power source, and the driving power source can be configured with a very simple driving circuit.

As a result, it is possible to realize a cross-point type nonvolatile memory that is less likely to be erroneously read or erroneously written and that can be rewritten with respect to the magnetoresistive effect element 1 by a current only in one direction.
It is obvious that a three-dimensional memory can be realized by stacking the cross-point type memory array configuration via an insulating layer.

  The memory element and the driving method thereof according to the present invention are useful as a magnetic solid state memory represented by a magnetic random access memory used for an information communication terminal or the like.

The figure which shows the structure of the magnetoresistive effect element of this invention The figure showing the resistance change by the magnetization relative angle of the ferromagnetic layer which comprises the magnetoresistive effect element of this invention The figure which shows the structure of the magnetoresistive effect element of this invention The figure which shows the VI characteristic of the magnetoresistive effect element of this invention The figure which shows the magnetocrystalline anisotropy of the magnetoresistive effect element of this invention The figure which shows the preparation methods of the magnetoresistive effect element of this invention The figure which shows the structure of the magnetoresistive effect element of this invention The figure which shows the drive principle of the magnetoresistive effect element of this invention The figure which shows the drive principle of the magnetoresistive effect element of this invention The figure which shows the memory array and drive current of the memory of this invention The figure which shows the drive current and sneak current of the memory array of the conventional memory A diagram showing a conventional memory cell structure

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetoresistance effect element 1a, 1a ', 1c, 1c' Ferromagnetic layer 2 Insulating layer 3, 3 'Conductor 4 Soft magnetic layer 5 Antiferromagnetic layer 6 Free layer 7 Fixed layer 8 Nonmagnetic layer 9, 9' Strong Magnetic layer 10 Substrate 11 Protruding portions 12, 12a, 12b, 12c Magnetoresistive effect element

Claims (11)

It is composed of at least two magnetic bodies and a conductor having at least one magnetic property formed so as to be sandwiched between the magnetic bodies, and one of the magnetic bodies is in physical contact with the conductor, wherein another of the magnetic material is in contact with the conductor and physically point, quantum conductance of the variable resistance comprises a magnetoresistive element is 0.01 or more and 0.3 G ₀ or less, the magnetoresistive element and its magnetoresistance effect A memory cell comprising only an electrode for supplying a current necessary for writing or reading to an element, a word line and a bit line joined to the electrode. 2. The memory cell according to claim 1, wherein the magnetoresistive effect element constituting the memory cell has nonlinear characteristics. 3. The memory cell according to claim 1, wherein the magnetoresistive effect element constituting the memory cell is made of a metal material. The magnetization free layer of the magnetoresistive effect element is composed of at least two ferromagnetic layers via a nonmagnetic layer, and the magnetization directions of the two ferromagnetic layers are arranged in antiparallel and have magnetic coupling. 4. The memory cell according to claim 1, wherein: 5. The memory cell according to claim 4, wherein the magnetization free layer of the magnetoresistive effect element is composed of at least two ferromagnetic layers with a nonmagnetic layer interposed therebetween, and the thicknesses of the ferromagnetic layers are different. 6. The memory cell according to claim 1, wherein the magnetization fixed layer of the magnetoresistive effect element has an antiferromagnetic layer. The magnetization fixed layer of the magnetoresistive effect element is composed of at least two ferromagnetic layers via a nonmagnetic layer, and the two ferromagnetic layers have antiferromagnetic coupling. 5. The memory cell according to 5. It is composed of at least two magnetic bodies and a conductor having at least one magnetic characteristic formed so as to be sandwiched between the magnetic bodies, and the magnetic body is in physical contact with the conductor and has the magnetic characteristics. A magnetoresistive effect element having a resistance that varies depending on a magnetization relative angle between two magnetic bodies formed so as to sandwich a conductor, and a quantum conductance of 0.01 or more and 0.3 G ₀ or less; In a memory cell including only an electrode for passing a current necessary for writing or reading to the resistive element, and a word line and a bit line joined to the electrode, the magnetoresistive element constituting the memory cell 8. The method of driving a memory cell according to claim 1, wherein the element resistance is changed by flowing a current only in one direction to change the magnetization direction. 9. The method of driving a memory cell according to claim 8, wherein a current is caused to flow in a direction perpendicular to the film surface of the magnetoresistive effect element constituting the memory cell. 10. The memory according to claim 1, wherein said memory device has a cross point structure in which said word lines and bit lines are arranged in a matrix and said memory cells are arranged at positions crossing each other. 11. The memory according to claim 10, wherein the memory array is three-dimensionally stacked via an insulating layer.

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