JP2015201515A - Thin film magnetic element and high frequency device with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select an oscillation frequency of a signal at a desired value in a thin film magnetic element utilizing high frequency characteristics of a magnetoresistance effect element.SOLUTION: In the thin film magnetic element, a current constriction layer including a plurality of nano contact holes, a first ferromagnetic layer and a second ferromagnetic layer are laminated. A nonmagnetic layer is included between the first ferromagnetic layer and the second ferromagnetic layer, the first ferromagnetic layer is included between the current constriction layer and the nonmagnetic layer, and a nonmagnetic conductive region is included which is disposed between the current constriction layer and the first ferromagnetic layer or at an opposite side of the first ferromagnetic layer to the current constriction layer. An area Se of an opposing surface of the nonmagnetic conductive region opposite to the first ferromagnetic layer and an area Sf of a minimum cross section having a minimum area among cross sections of the first ferromagnetic layer vertical to a direction of lamination meet the relation of Sf>Se.

Description

  The present invention relates to a thin film magnetic element applied to non-wired signal transmission, a new functional element for communication, and the like, and a high frequency device including the same.

  To date, the development of electronics has been brought about by various semiconductor devices using carrier charges. However, in recent years, the field of spintronics (spin + electronics) that uses spins in addition to carrier charges has attracted attention. Spintronics contributes greatly to the industry in the form of hard disk drives (HDD) and magnetoresistive memories (MRAM) due to the rapid development of magnetoresistive elements utilizing the giant magnetoresistive (GMR) effect and tunneling magnetoresistive (TMR) effect. I have done it.

  In magnetoresistive elements, it is known that spin-polarized electrons in a ferromagnet are transported to an antiparallel magnetized ferromagnet, causing precession in the spin of the ferromagnet and causing spin reversal. ing. Here, when a magnetic field is applied in the direction in which the spin is reversed, and the two torques derived from the spin-polarized current and the external magnetic field are antagonized, an oscillation phenomenon corresponding to the period of the spin precession occurs. Industrial applications as devices such as high-frequency oscillation, detection, mixers, and filters using these phenomena have been proposed.

  An element that uses the high frequency characteristics of a magnetoresistive effect element (hereinafter referred to as a thin film magnetic element) is smaller in size, impedance matching with a transmission circuit, and variability in frequency characteristics than an element that uses high frequency characteristics made of semiconductor In view of this, research into higher output is underway for practical application. (Patent Document 1)

JP 2011-181756 A JP 2010-87225 A

  In Patent Document 1, it is possible to change the oscillation frequency by controlling the perpendicular magnetic anisotropy of the magnetization free layer and the magnetization fixed layer and adjusting the external magnetic field applied to the magnetic oscillation element.

  Patent Document 2 describes a thin-film magnetic element that can change the frequency and amplitude of a signal by changing the direction of an external magnetic field using ferromagnetic uniaxial magnetic anisotropy.

  In Patent Documents 1 and 2, the oscillation characteristics of the magnetic oscillation element are optimized by controlling an external magnetic field. However, problems such as the influence of the leakage magnetic field remain in the control by the external magnetic field.

  During etching by element processing, alteration occurs at the processed end of the element due to the impact of atoms. The design of the ferromagnetic layer is known to cause precession with different spins at the edge of the magnetization free layer and the central part that is not easily affected by etching, and to oscillate signals with different frequency bands. On the other hand, the oscillation frequency can be changed by combining different frequency bands at the center and end of the magnetization free layer.

  Therefore, in the present invention, by using a structure in which a non-magnetic conductive region processed to be narrow and a current confinement layer having a plurality of nanocontact holes are used, the region of the ferromagnetic current is adjusted and the oscillation frequency is selected. An object of the present invention is to provide a thin film magnetic element capable of achieving the above.

  The thin film magnetic element according to the first aspect of the present invention that achieves the above object includes a current confinement layer having a plurality of nanocontact holes, a first ferromagnetic layer, and a second ferromagnetic layer laminated. A thin film magnetic element comprising a nonmagnetic layer between the first ferromagnetic layer and the second ferromagnetic layer, and the first magnetic layer between the current confinement layer and the nonmagnetic layer. A nonmagnetic conductive region having a ferromagnetic layer and disposed between the current confinement layer and the first ferromagnetic layer, or disposed on the opposite side of the current confinement layer from the first ferromagnetic layer; A minimum area having a minimum area of a cross section perpendicular to the stacking direction of the first ferromagnetic layer and the area Se of the nonmagnetic conductive region facing the first ferromagnetic layer. The thin film magnetic element is characterized in that a cross-sectional area Sf satisfies a relationship of Sf> Se.

  According to the thin film magnetic element according to the first aspect, since Se is smaller than Sf, the current region flowing in the first ferromagnetic layer can be defined in a range corresponding to Se. At the end of the first ferromagnetic layer, alteration due to processing occurs, and the saturation magnetization Ms decreases. A decrease in the saturation magnetization Ms causes a decrease in the oscillation frequency, and the oscillation frequency differs between the central portion and the end portion of the first ferromagnetic layer. Therefore, it is possible to select the oscillation frequency of the signal by changing the ratio between the end portion and the center portion of the first ferromagnetic layer in the Se region.

  Further, by combining the current confinement layer with the nonmagnetic conductive region, it becomes possible to reduce the diffusion of the current flowing through the first ferromagnetic layer, and the current in the range corresponding to Se can be accurately supplied to the first ferromagnetic layer. It becomes possible to flow.

  In the thin film magnetic element according to the second aspect of the present invention, the peripheral portion of the first ferromagnetic layer according to the first aspect is such that the opposing surface is the interface on the opposing surface side of the first ferromagnetic layer. The thin film magnetic element is characterized in that the nonmagnetic conductive region is arranged so as to be exposed in an annular shape with respect to the first projection surface projected above.

  The exposure in the present invention does not mean that it is exposed to the outside air, but when the first projection surface is viewed from the stacking direction and the upper layer is viewed from the first projection surface, the first ferromagnetic material is observed. This indicates a state in which the periphery of the layer can be confirmed in an annular shape.

  According to the thin film magnetic element according to the second aspect, since the nonmagnetic conductive region is disposed so as to expose the peripheral portion of the first ferromagnetic layer in an annular shape, the end portion of the first ferromagnetic layer The ratio of the amount of current passing through is small. As a result, the signal oscillation frequency can be increased.

  A thin film magnetic element according to a third aspect of the present invention is characterized in that a second projection surface obtained by projecting the opposing surface onto the minimum cross section is included in the minimum cross section. It is.

  According to the thin film magnetic element according to the third aspect, since the nonmagnetic conductive region is arranged so as to expose the peripheral portion of the minimum cross section in an annular shape, the current is more central in the first ferromagnetic layer. It passes through the area corresponding to the part. Since the ratio of the amount of current passing through the end of the first ferromagnetic layer is smaller, the signal oscillation frequency can be further increased.

  The thin film magnetic element according to the fourth aspect of the present invention includes a minimum value leo of a distance from an end of the second projection surface to an end of the minimum cross section, and the first ferromagnetic layer from the facing surface. The thin film magnetic element according to the fourth feature is that a thickness df obtained by removing a film thickness of the current confinement layer from a thickness up to the interface on the nonmagnetic layer side satisfies a relationship of leo> df.

  According to the thin film magnetic element of the fourth aspect, the flow of electrons confined by the region defining the nonmagnetic conductive region Se passes through a region corresponding to the area of Se of the first ferromagnetic layer. To do. Since df is defined to be smaller than leo, the flow of electrons passing from the nonmagnetic conductive region to the first ferromagnetic layer is diffused to the region of the processed end of the first ferromagnetic layer. The signal oscillation frequency is further increased.

  The thin film magnetic element according to the fifth aspect of the present invention has a plurality of the nonmagnetic conductive regions, and the shortest distance lei between the nonmagnetic conductive regions that are closest to each other satisfies the relationship of lei / 2> df. A thin film magnetic element according to a fifth feature.

  According to the thin film magnetic element according to the fifth aspect, since each nonmagnetic conductive region satisfies lei / 2> df, the flow of electrons confined by each nonmagnetic conductive region is not synthesized by diffusion. , Passing through the center of the first ferromagnetic layer. Since the signal generated by the constricted current causes phase lock, it is possible to narrow the oscillation frequency band of the signal and increase the output of the signal.

  In the thin film magnetic element according to the sixth aspect of the present invention, the average distance dnc between the centers of the nanocontact holes adjacent to each other satisfies the relationship of dnc / 2> df. It is the thin film magnetic element characterized by these.

  According to the thin film magnetic element according to the sixth aspect, since the relationship of dnc / 2> df is satisfied, diffusion of the electron flow constricted by the nano contact hole flows in the first ferromagnetic layer. Thus, the signal oscillation frequency band can be narrowed and the signal output can be further increased by improving the current density and generating a phase lock.

  According to the present invention, in a thin film magnetic element utilizing the high frequency characteristics of a magnetoresistive effect element, a structure in which a nonmagnetic conductive region processed narrowly without using an external magnetic field and a current confinement layer having a plurality of nanocontact holes are combined By using, an element structure capable of selecting an oscillation frequency can be provided.

It is sectional drawing which shows the detailed laminated structure of the thin film magnetic element based on Embodiment 1 of this invention. Sectional drawing which shows the detailed laminated structure of the thin film magnetic element based on Embodiment 2 of this invention, and the opposing surface facing the 1st ferromagnetism of a nonmagnetic conductive area | region are projected on the interface of a 1st ferromagnetic layer It is the figure showing the 1st projection surface. Sectional drawing which shows the detailed laminated structure of the thin film magnetic element based on Embodiment 2 of this invention, and the opposing surface which opposes the 1st ferromagnetism of a nonmagnetic conductive area are perpendicular | vertical to the lamination direction of a 1st ferromagnetic layer. It is a figure showing the 2nd projection surface projected on the minimum section which has the minimum area among simple sections. It is sectional drawing which shows the laminated structure outline of the thin film magnetic element based on Embodiment 3 of this invention. It is sectional drawing which shows the laminated structure outline of the thin film magnetic element based on Embodiment 4 of this invention. It is sectional drawing which shows the laminated structure outline of the thin film magnetic element based on Embodiment 5 of this invention. It is sectional drawing which shows the laminated structure outline of the thin film magnetic element based on Embodiment 6 of this invention. It is a figure which shows the oscillation apparatus used for wiringless signal transmission based on Embodiment 7 of this invention. FIG. 3 is a cross-sectional view schematically illustrating a laminated structure of a thin film magnetic element of Comparative Example 1. 6 is a cross-sectional view schematically showing a laminated structure of a thin film magnetic element of Comparative Example 2. FIG. It is a figure which shows the relationship between the distance X between the center axis | shaft of the surface perpendicular | vertical to each lamination direction of a 1st ferromagnetic layer and a nonmagnetic electrically conductive area | region and oscillation frequency based on Embodiment 1 of this invention. It is a figure which shows the relationship between leo / df and the oscillation frequency of a signal. It is a figure which shows the relationship between (lei / 2) / df and the oscillation output of a signal. It is a figure which shows the relationship between (dnc / 2) / df and the oscillation output of a signal. It is a figure which shows the relationship between the distance X between the center axis | shaft of the surface perpendicular | vertical to each lamination direction of a 1st ferromagnetic layer and a nonmagnetic electrically conductive area | region based on Comparative Examples 2-6, and an oscillation frequency.

  Hereinafter, preferred embodiments of the present invention will be described. However, the present invention is not limited to these embodiments, and is included in the scope of the present invention as long as the form has the technical idea of the present invention. Each configuration in each embodiment, a combination thereof, and the like are examples, and the addition, omission, replacement, and other changes of the configuration can be made without departing from the spirit of the present invention. Further, the present invention is not limited by the embodiments, and is limited only by the scope of the claims.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a detailed laminated structure of a thin film magnetic element 1 according to the first embodiment. The thin film magnetic element 1 of Embodiment 1 includes a second ferromagnetic layer 2, a nonmagnetic layer 3, a first ferromagnetic layer 4, a current confinement layer 6 including a plurality of nanocontact holes 5, and a nonmagnetic conductive region 7. It arrange | positions in this order and the insulator 8 is arrange | positioned so that the peripheral part of each layer may be enclosed.

  In the present invention, the laminated structure of the thin-film magnetic element 1 is not limited to that of the first embodiment, and the order of lamination may be reversed. When the effects of the present invention can be obtained, a thin layer is disposed between the layers. May be.

  The nonmagnetic conductive region 7 has a role as an electrode, and the lower electrode 9 is disposed at a position that makes a pair with the nonmagnetic conductive region 7 so as to sandwich the current confinement layer 6 from the second ferromagnetic layer 2. Has been. When a current is passed through a pair of electrodes, the structure passes through in a direction intersecting the surface of each layer constituting the element, for example, a direction perpendicular to the surface of each layer constituting the thin film magnetic element 1 (stacking direction). .

  The pair of electrodes is made of, for example, a sputtering apparatus and is composed of Ta, Cu, Au, AuCu, Ru, or any two or more of the above films, and the film thickness is desirably 5 nm to 500 nm.

Each of the second ferromagnetic layer 2, the nonmagnetic layer 3, and the first ferromagnetic layer 4 is formed using, for example, a sputtering apparatus. As the sputtering apparatus, an apparatus having a plurality of physical vapor deposition (PVD) chambers and an oxidation chamber is preferable. Preferably, at least one of the plurality of PVD chambers is capable of co-sputtering. Sputter film formation is performed, for example, by sputtering a target made of metal or alloy using Ar sputtering gas and forming a film on the substrate under an ultrahigh vacuum. At this time, the flow rate of Ar gas is preferably 1 to 300 sccm, the applied power between the substrate and the target is 50 to 500 W, and the degree of vacuum is preferably 5.0 × 10 ⁻⁶ Pa or less.

  The buffer layer for improving the roughness of the lower electrode layer 9 between the lower electrode layer 9 and the second ferromagnetic layer 2 and the orientation of the second ferromagnetic layer by blocking the crystallinity of the lower electrode. -You may arrange | position the seed layer which gave the function which controls a particle size. The material of the buffer layer and the seed layer is preferably a film of Ta and NiCr or a film of Ta and Ru, for example. Each film thickness of the buffer layer and the seed layer is preferably about 2 to 6 nm, for example. In either case, if the film thickness is too small, a desired effect cannot be obtained, and if it is too large, parasitic resistance that does not contribute to the magnetoresistance effect increases.

  The purpose of the second ferromagnetic layer 2 is to dispose a ferromagnetic layer imparted with unidirectional magnetic anisotropy by exchange coupling. As a preferred form, an antiferromagnetic layer, an outer layer, a nonmagnetic intermediate layer, and an inner layer (not shown) are sequentially laminated, that is, a synthetic pinned layer.

  The inner layer and the outer layer are configured to include a ferromagnetic layer made of a ferromagnetic material containing Co or Fe, for example. The inner layer and the outer layer are antiferromagnetically coupled by the nonmagnetic intermediate layer, and are fixed so that the directions of magnetization are opposite to each other.

  The inner layer and the outer layer are preferably, for example, a CoFe alloy, a laminated structure of CoFe alloys having different compositions, and a laminated structure of a CoFeB alloy and a CoFe alloy. The thickness of the inner layer is preferably 2 to 10 nm, and the thickness of the outer layer is preferably about 1 to 7 nm. The inner layer may contain a Heusler alloy.

  The nonmagnetic intermediate layer is made of, for example, a nonmagnetic material containing at least one selected from the group of Ru, Rh, Ir, Re, Cr, Zr, and Cu. The film thickness of the nonmagnetic intermediate layer is, for example, about 0.35 nm to 1.0 nm. The nonmagnetic intermediate layer is provided to fix the magnetization of the inner layer and the magnetization of the outer layer in opposite directions. If the film thickness is too large, the inner layer and the outer layer are interposed via the nonmagnetic intermediate layer. Magnetic coupling is weakened. The “magnetization is opposite to each other” is a wide concept including the case where these two magnetizations differ from each other by 180 ° ± 20 ° without being narrowly interpreted as being narrowly limited.

  The material of the antiferromagnetic layer is, for example, an antiferromagnetic material containing at least one element selected from the group consisting of Pt, Ru, Rh, Pd, Ni, Cu, Ir, Cr and Fe, and Mn. Consists of materials. The Mn content is preferably 35 to 95 at%.

  A hard magnetic layer may be disposed instead of the antiferromagnetic layer. As the hard magnetic layer material, CoPt, FePt or the like is preferable.

The nonmagnetic layer 3 has a role for obtaining the magnetoresistance effect by causing the magnetizations of the first ferromagnetic layer 4 and the second ferromagnetic layer 2 to interact with each other. If it is a body, Al ₂ O ₃ and single crystal MgO _x (001) are preferable, and the film thickness is desirably about 0.5 to 2.5 nm.

In addition, when a layer including a conductive region constituted by a conductor is applied to the nonmagnetic insulator, the nonmagnetic insulator constituted by Al ₂ O ₃ or magnesium oxide (MgO) is added to CoFe, CoFeB, CoFeSi, CoMnGe. , CoMnSi, CoMnAl, Fe, Co, Au, Cu, Al, Mg, and the like. The thickness of the insulator and the conductive region is preferably about 0.5 to 2.5 nm.

  The first ferromagnetic layer 4 is a layer having a smaller coercive force than that of the second ferromagnetic layer 2 whose magnetization direction is changed by an external magnetic field or a spin-polarized current. When selecting a material having an axis of easy magnetization in the in-plane direction of the film, for example, it is constituted by a film having a thickness of about 1 to 15 nm made of CoFe, CoFeB, CoFeSi, CoMnGe, CoMnSi, CoMnAl, or the like. A soft magnetic film made of, for example, NiFe having a thickness of about 1 to 9 nm may be added to the film as a magnetostriction adjusting layer.

  When the first ferromagnetic layer 4 is selected from a material having an easy axis in the normal direction of the film surface, for example, Co, Co / non-magnetic layer laminated film, CoCr alloy, Co multilayer film, CoCrPt alloy, It is composed of a FePt alloy, a rare earth-containing SmCo alloy, a TbFeCo alloy, and a Heusler alloy.

  Further, a high spin polarization material may be inserted between the first ferromagnetic layer 4 and the nonmagnetic layer 3. This makes it possible to obtain a high magnetoresistance change rate. Examples of the high spin polarization material include a CoFe alloy and a CoFeB alloy. The thickness of each of the CoFe alloy and the CoFeB alloy is preferably 0.2 nm or more and 1 nm or less.

  Further, induced magnetic anisotropy may be introduced by applying a constant magnetic field in the direction perpendicular to the film surface when the first ferromagnetic layer 4 is formed.

The current confinement layer 6 includes a plurality of nanocontact holes 5 and an insulator 10, and a current having a large current density is supplied to the first ferromagnetic layer 4 by confining the flow of electrons due to the current in the nanocontact holes 5. And has the role of increasing the output of the signal. The material of the nano contact hole 5 is preferably a nonmagnetic conductive material typified by Al or Cu, and the insulator material is preferably Al ₂ O ₃ , magnesium oxide (MgO), SiO ₂ or the like.

When an oxide is used for the insulator 10, a nonmagnetic metal may be formed and then oxidized by natural oxidation or Ion-Assisted-Oxidation (IAO) treatment. For example, the natural oxidation is performed by flowing an oxygen gas into the IBD device after depositing a nonmagnetic metal in the IBD device. The IAO treatment is performed, for example, by irradiating a nonmagnetic metal with oxygen gas or oxygen ions in the IBD apparatus and simultaneously irradiating the nonmagnetic metal with low energy Ar ions. In the case of natural oxidation, it is desirable to leave for 5 sec to 200 sec under an oxygen flow rate of ^{1 to} 10 sccm or an oxygen partial pressure of 1.0 × 10 ⁻³ Pa to 5.0 × 10 ⁻¹ Pa. In the case of IAO treatment, it is desirable that the oxygen flow rate be 1 sccm to 5 sccm and the treatment time be 5 sec to 100 sec.

  The nanocontact hole 5 preferably uses a nonmagnetic conductor constituting a layer in contact with the stacking direction of the current confinement layer 6.

  The diameter of the nano contact holes 5 is desirably 0.1 nm to 20 nm, and the interval between the nano contact holes 5 is desirably 10 nm to 100 nm.

The nonmagnetic conductive region 7 has a role of flowing a current to a desired region of the first ferromagnetic layer 4.
Any material can be used for the nonmagnetic conductive region 7 as long as it is nonmagnetic and conductive. For example, Pt, Au, Cu, Al, or the like can be used. The thickness of the nonmagnetic conductive region 7 is desirably 1 to 20 nm.

After the formation of the nonmagnetic conductive region 7, a heat treatment in a magnetic field is performed to fix the magnetization. The heat treatment in the magnetic field is preferably performed at a vacuum of 1.0 × 10 ⁻³ Pa or less, a temperature of 250 ° C. to 300 ° C., a time of 1 hour to 5 hours, and an applied magnetic field of 3 kOe to 10 kOe.

After the heat treatment in the magnetic field, in order to make the nonmagnetic conductive region 7, the current confinement layer 6, the first ferromagnetic layer 4, the nonmagnetic layer 3, and the second ferromagnetic layer 2 into desired shapes, the first resist patterning, Ion beam etching is performed, and the insulator 8 is disposed in the removed region by a sputtering apparatus or the like. The material of the insulator 8 is preferably SiO ₂ , Al ₂ O ₃ or the like.

  The final shape corresponding to Sf is defined by the first ion beam etching.

Next, after the nonmagnetic conductive region 7 is formed into a desired shape by second resist patterning and ion beam etching, the insulator 8 is disposed in the removed region by a sputtering apparatus or the like. The material of the insulator 8 is preferably SiO ₂ , Al ₂ O ₃ or the like.

  The final shape corresponding to Se is defined by the second ion beam etching.

  The shape of the surface perpendicular to the stacking direction of the nonmagnetic conductive region 7 and the first ferromagnetic layer 4 is not particularly limited, and may be a circle, an ellipse, or a polygon.

  Se is defined to be smaller than Sf. Since the frequency band of the oscillating signal is different between the end portion and the central portion of the first ferromagnetic layer 4, oscillation occurs by changing the ratio between the end portion and the central portion of the first ferromagnetic layer 4 in the Se region. The frequency band of the signal can be controlled.

  In the first embodiment of the present invention, the shape from the nonmagnetic conductive region 7 to the second ferromagnetic layer 2 is defined by two times of photoresist patterning and ion beam etching. It is not limited. As long as Se satisfies the relationship smaller than Sf, the shape of the second ferromagnetic layer 2 is defined from the nonmagnetic conductive region 7 by performing photoresist patterning and / or ion beam etching three times or more. However, the same effect can be obtained.

  The flow of current to the thin film magnetic element is not limited to the nonmagnetic conductive region 7 from the lower electrode 9, and the effect can be obtained even when flowing in the reverse direction.

(Embodiment 2)
FIG. 2 is a cross-sectional view showing a detailed laminated structure of the thin film magnetic element 1 according to the second embodiment, and the nonmagnetic conductive region 7 has an opposing surface 10 facing the first ferromagnetic layer 4 on the interface of the first ferromagnetic layer 4. It is the figure which showed the 1st projection surface 11 projected on. The difference from the thin film magnetic element 1 according to Embodiment 1 shown in FIG. 1 is that the cross-sectional area of the cross section perpendicular to the stacking direction of the first ferromagnetic layer 4 is not uniform. The other points are the same as those of the thin film magnetic element 1 according to the first embodiment, and the effect of changing the oscillation characteristics and the expression principle are also the same.

  When the nonmagnetic conductive region 7 is arranged so that the peripheral portion of the first ferromagnetic layer 4 is annularly exposed with respect to the first projection surface 11, the current flows in the central portion of the first ferromagnetic layer 4. Pass through the corresponding area. As a result, the ratio of the amount of current passing through the end of the first ferromagnetic layer 4 is reduced, the frequency band of the oscillating signal can be narrowed, and the signal output can be increased.

  3 is a detailed cross-sectional view of the thin-film magnetic element 1 according to the second embodiment and the opposing surface 10 facing the first ferromagnetic layer 4 in the nonmagnetic conductive region 7 in the stacking direction of the first ferromagnetic layer 4. It is a figure showing the 2nd projection surface 12 projected on the minimum section 13 which has the minimum area among perpendicular sections.

  When the second projection surface 12 obtained by projecting the opposing surface 10 onto the minimum cross section 13 perpendicular to the stacking direction of the first ferromagnetic layer 4 is included in the minimum cross section 13, the peripheral portion of the minimum cross section 13 is exposed in an annular shape. Thus, since the nonmagnetic conductive region 7 is arranged, the current passes through a region corresponding to the central portion of the first ferromagnetic layer 4. As a result, the ratio of the amount of current passing through the end of the first ferromagnetic layer 4 is reduced, the frequency band of the oscillating signal can be further narrowed, and the signal output can be increased.

  Further, the minimum value leo of the distance from the end of the second projection surface 12 to the end of the minimum cross section 13 and the thickness from the facing surface 10 to the interface of the first ferromagnetic layer 4 on the nonmagnetic layer 3 side. On the other hand, when the thickness df excluding the thickness of the current confinement layer 6 is defined so as to satisfy the relationship leo> df, electrons flowing from the nonmagnetic conductive region 7 to the first ferromagnetic layer 4 Since the flow passes through the region of the processed end of the first ferromagnetic layer 4 without being diffused, it is possible to further narrow the oscillation frequency band and increase the output of the signal.

(Embodiment 3)
FIG. 4 is a sectional view showing a detailed laminated structure of the thin-film magnetic element 1 according to Embodiment 3 of the present invention. The thin film magnetic element 1 according to Embodiment 3 includes a current confinement layer 6 including a second ferromagnetic layer 2, a nonmagnetic layer 3, a first ferromagnetic layer 4, a nonmagnetic conductive region 7, and a plurality of nanocontact holes 5. Are arranged in this order.

  The other points are the same as those of the thin film magnetic element 1 according to the first embodiment shown in FIG. 1, and the effect of changing the oscillation frequency and the principle of expression are also the same.

  In the third embodiment, since the current confinement layer 6 does not exist between the facing surface 10 and the interface of the first ferromagnetic layer 4 on the nonmagnetic layer 3 side, the difference in the film thickness of the current confinement layer 6 with respect to df is It is unnecessary.

(Embodiment 4)
FIG. 5 is a sectional view showing a detailed laminated structure of the thin film magnetic element 1 according to Embodiment 4 of the present invention. The difference from the thin film magnetic element 1 according to Embodiment 1 shown in FIG. 1 is that the nonmagnetic conductive region 7 is arranged so as to be in contact with the end portion of the current confinement layer 6.

  Other points are the same as those of the thin film magnetic element 1 according to the first embodiment, and the expression principle is also the same.

Most of the current flowing through the thin film magnetic element 1 passes through the end of the first ferromagnetic layer 4. Since the end portion of the first ferromagnetic layer 4 has undergone alteration due to ion milling and the saturation magnetization Ms has decreased, the oscillation frequency of the signal can be made lower than that of the first embodiment.

(Embodiment 5)
FIG. 6 is a sectional view showing a detailed laminated structure of the thin film magnetic element 1 according to the fifth embodiment of the present invention. The difference from the thin film magnetic element 1 according to Embodiment 1 shown in FIG. 1 is that when the cross section of the thin film magnetic element is viewed, the shape from the second ferromagnetic layer 2 to the current confinement layer 6 is substantially trapezoidal. It is a point. The other points are the same as those of the thin film magnetic element 1 according to the first embodiment, and the oscillation principle is also the same.

(Embodiment 6)
FIG. 7 is a cross-sectional view showing a detailed laminated structure of the thin film magnetic element 1 according to Embodiment 6 of the present invention. The difference from the thin film magnetic element 1 according to Embodiment 1 shown in FIG. 1 is that it has a plurality of nonmagnetic conductive regions 7. The signal generated by the flow of electrons confined in the nonmagnetic conductive region 7 causes phase lock, so that the oscillation frequency band of the signal can be narrowed and the output can be increased.

In addition, when the shortest distance lei between the nonmagnetic conductive regions 7 that are closest to each other satisfies the relationship of lei / 2> df, the flow of confined electrons does not merge, the current density is improved, and the signal is output at high power. It is more preferable because
(Embodiment 7)

  FIG. 8 shows the thin film magnetic element 1 according to the first embodiment of the present invention, which is an oscillation device 14 used for non-wired signal transmission. The oscillation device 14 includes a signal generation unit 16 including a thin film magnetic element 1 and a magnetic field application mechanism 15, a power supply unit 17, and a signal amplification unit 18. By controlling the output of the power supply unit 17, the current applied to the thin film magnetic element 1 and the current applied to the magnetic field application mechanism 15 can be controlled. A signal from the thin film magnetic element 1 that oscillates due to an applied current from the power supply unit 17 is amplified to a desired output by the signal amplification unit 16 and used for signal transmission.

  Next, the embodiments of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
The thin film magnetic element 1 described in the first embodiment of the present invention was produced. On the thermally oxidized Si substrate, Cu (100 nm) was deposited as a lower electrode 9 using a sputtering apparatus. Thereafter, a CPW shape was formed by photolithography and ion milling.

  Next, using a sputtering apparatus and an IBD apparatus, a buffer layer, a seed layer, a second ferromagnetic layer 2, a nonmagnetic layer 3, a first ferromagnetic layer 4, a current confinement layer 6, a nonmagnetic conductive region 7, and a cap Layers were deposited in this order. The film structure of each layer is Ta (2 nm) for the buffer layer, Ru (2 nm) for the seed layer, IrMn (7 nm) / 90 CoFe 2.4 (nm) for the second ferromagnetic layer 2, and MgO (1 for the nonmagnetic layer 3). 1.5 nm), the first ferromagnetic layer 4 is 90 CoFe (10 nm), the current confinement layer 6 is Al (1.5 nm) / IAO treatment (Ar gas 10 sccm, 20 sec), the nonmagnetic conductive region 7 is Cu (100 nm), The cap layer was Ru (2 nm).

Next, first photolithography and ion milling were performed, and the size of each layer from the cap layer to the buffer layer was patterned into a circle of φ300 nm. Subsequently, the insulator 8 was formed by sputtering and lift-off. Al ₂ O ₃ was used for the insulator 8.

  Next, second photolithography and ion milling were performed, and each layer from the cap layer to the nonmagnetic conductive region 7 was patterned into a circle of φ100 nm. The circular central axis and the central axis of the first ferromagnetic layer 4 were made to coincide.

  Next, an upper electrode layer was formed by photolithography, sputtering, and lift-off. The upper electrode layer was Cu (20 nm).

  With respect to the thin film magnetic element 1 produced by the above method, the oscillation output was measured while selecting the amount of current, the magnitude of the external magnetic field, and the magnetic field application direction.

  The current applied to the thin film magnetic element 1 was set to 3 mA, and the RBW (Resolution Band Width) of the spectrum analyzer was set to 3 MHz to measure the oscillation output. As a result, the oscillation output was calculated to 110 [nW] with respect to the maximum peak obtained by calculating the oscillation output in consideration of RBW and the full value at half maximum.

(Examples 2 to 6)
The thin film magnetic element 1 described in the first embodiment of the present invention was produced as Example 2, Example 3, Example 4, Example 5, and Example 6. As shown in FIG. 1, the distance X from the central axis of the plane perpendicular to the stacking direction of the first ferromagnetic layer 4 to the central axis of the plane perpendicular to the stacking direction in the nonmagnetic conductive region 7 Except for the point of changing, all have the same configuration as in Example 1. The oscillation output was measured for the created element. Table 1 shows the results of the distance X and the oscillation output.

(Examples 7 to 11)
The thin film magnetic element 1 described in the first embodiment of the present invention was manufactured as Example 7, Example 8, Example 9, Example 10, and Example 11. Unlike the first embodiment, a nonmagnetic conductive layer is disposed between the current confinement layer 6 and the first ferromagnetic layer 4 for the purpose of changing df. The nonmagnetic conductive layer was Cu, and the film thickness was set to several conditions. The oscillation output was measured for the created element. Table 2 shows the results of df, leo / df, and oscillation output.

(Examples 12 to 16)
The thin film magnetic element 1 described in the sixth embodiment of the present invention was produced as Example 12, Example 13, Example 14, Example 15, and Example 16. The manufacturing method is partly different from that of the first embodiment, in which a nonmagnetic conductive layer is disposed between the current confinement layer 6 and the first ferromagnetic layer 4 for the purpose of changing df, and in the second photolithography, This is that the two nonmagnetic conductive regions 7 are patterned.

The material of the nonmagnetic conductive layer was Cu, and the film thickness was set to several conditions. Further, the size of each of the two nonmagnetic conductive regions 7 was set to φ80 nm, and the shortest distance between the nonmagnetic regions was set to 40 nm. All the nonmagnetic conductive regions 7 are patterned so as to satisfy leo> df. Subsequently, an insulator 8 was formed by sputtering or lift-off. Al ₂ O ₃ was used for the insulator 8.

  Next, an upper electrode layer was formed by photolithography, sputtering, and lift-off. The upper electrode layer was Cu (20 nm).

  The oscillation output was measured for the thin film magnetic element 1 manufactured by the above method. Table 3 shows the results of df, (lei / 2) / df, and oscillation output.

(Examples 17 to 21)
The thin film magnetic element 1 described in the first embodiment of the present invention was produced as Example 17, Example 18, Example 19, Example 20, and Example 21. The manufacturing method is partially different from that in Example 1, and the IAO processing time in manufacturing the current confinement layer 6 was changed for the purpose of changing the number of nanocontact holes 5 and the average distance between the closest nanocontact holes 5. .

  The number of nanocontact holes 5 is measured by conductive-AFM (hereinafter c-AFM). Since the amount of current flowing between the nanocontact hole 5 and the insulating layer 8 is different, the conductive probe is brought into contact with the surface of the sample prepared up to the current confinement layer 6, and the region of the conductive portion is regarded as the nanocontact hole 5. The number is the number of nanocontact holes 5 and the average distance between the closest nanocontact holes 5 is obtained. In order to prevent oxidation of the sample surface, it is desirable to perform c-AFM measurement while maintaining a high vacuum environment after forming the current confinement layer 6.

Next, the nonmagnetic conductive region 7 is formed, the shape of the lower portion from the current confinement layer 6 is defined by φ300 nm by first photolithography and ion milling, and the nonmagnetic conductive region is formed by second photolithography and ion milling. The shape of 7 was defined at φ100 nm. In the deleted region, the insulator 8 was formed by sputtering or lift-off. Al ₂ O ₃ was used for the insulator 8.

  Next, an upper electrode layer was formed by photolithography, sputtering, and lift-off. The upper electrode layer was Cu (20 nm).

  The oscillation output was measured for the thin film magnetic element 1 manufactured by the above method. Table 4 shows the results of dnc, (dnc / 2) / df, and oscillation output.

(Comparative Example 1)
A thin film magnetic element 1 shown in FIG. The configuration was the same as in Example 1 except that the area of Se was made equal to the area of Sf. The oscillation frequency was measured for the created element. As a result, the oscillation frequency was 4.8 GHz.

(Comparative Examples 2-6)
The thin film magnetic element 1 shown in FIG. 10 was produced as Comparative Example 2, Comparative Example 3, Comparative Example 4, Comparative Example 5, and Comparative Example 6. As shown in FIG. 1, the distance X from the central axis of the plane perpendicular to the stacking direction of the first ferromagnetic layer 4 to the central axis of the plane perpendicular to the stacking direction in the nonmagnetic conductive region 7 The configuration was the same as that of Example 1 except that the current confinement layer 6 was not manufactured. The oscillation output was measured for the created element. The oscillation output was measured for the created element. Table 5 shows the results of the distance X and the oscillation output.

  FIG. 11 shows the relationship between the oscillation frequency of the output signal and the distance X with respect to the measurement results of the oscillation outputs of Examples 1 to 6.

  It can be seen that when X is in the range of 0 nm to 75 nm, the oscillation frequency does not change much and decreases in the range of 75 nm to 100 nm.

  At the end of the first ferromagnetic layer, alteration occurs due to ion milling, and the saturation magnetization Ms decreases. Since the oscillation frequency decreases due to the decrease of the saturation magnetization Ms, the oscillation frequency differs between the central portion and the end portion of the first ferromagnetic layer. Therefore, it is considered that the frequency band of the signal is changed by changing the ratio between the end portion and the center portion of the first ferromagnetic layer in the Se region.

  This time, in the region where X is less than 75 nm, the flow of electrons confined by the nonmagnetic conductive region 7 does not pass through the region of the end of the first ferromagnetic layer 4 and the oscillation frequency does not change significantly. Conceivable. In the region where X is larger than 75 nm, it is considered that the ratio of the amount of current passing through the end region of the first ferromagnetic layer 4 increases due to current diffusion, and the oscillation frequency gradually decreases.

  FIG. 12 shows the relationship between leo / df and the signal oscillation output for the measurement results of the oscillation outputs of Examples 7-11.

  From FIG. 12, it can be confirmed that the output of the signal does not change much in the range of leo> df, and the output decreases in the range of leo <df. In the range where df is smaller than leo, the current hardly passes through the end region of the first ferromagnetic layer 4, so the signal output does not change greatly, and when it exceeds leo, the current of the first ferromagnetic layer 4 It is thought that the amount of current passing through the end region increased and the signal output decreased.

  FIG. 13 shows the relationship between (lei / 2) / df and the oscillation output of the signal with respect to the measurement results of the oscillation outputs of Examples 12-16.

  From FIG. 13, it can be seen that the oscillation output does not change much in the range of lei / 2> df, and is small in the range of lei / 2 <df. When lei / 2 is larger than df, it is divided into a plurality of nonmagnetic conductive regions 7, and the constricted electron flow does not merge in the first ferromagnetic layer 4, and phase lock is generated, thereby showing high output. It is conceivable that when lei / 2 becomes smaller than df, the signals are merged in the first ferromagnetic layer 4 and the signal output is greatly reduced.

  FIG. 14 shows the relationship between (dnc / 2) / df and the oscillation output of the signal with respect to the measurement results of the oscillation output in Examples 17-21.

  FIG. 14 shows that the oscillation output is small in the range of dnc / 2 <df, and the output is rapidly increased in the range of dnc / 2> df. In the range where dnc / 2 is smaller than df, it is considered that the current density is not improved because the flow of the confined electrons divided into the plurality of nanocontact holes 5 is merged in the first ferromagnetic layer 4 and the output is low. However, in the range larger than df, it is considered that the current density is improved without being merged inside the first ferromagnetic layer 4 and the signal output is increased.

  FIG. 15 shows the relationship between the oscillation frequency of the output signal and the distance X with respect to the measurement results of the oscillation outputs of Comparative Examples 2-6.

  Compared with the result of FIG. 11, it can be seen that in FIG. 15, the upper and lower limits of the frequency are small and the amount of change with respect to X is small. In Comparative Examples 2 to 6, since there is no current confinement effect by the current confinement layer 6, the current is more diffused when passing through the first ferromagnetic layer 4, and the first ferromagnetic layer 4 On the other hand, it can be considered that the current easily flows. Therefore, it is considered that oscillations of different frequencies due to the central portion and the end portion of the first ferromagnetic layer 4 are easily mixed and the frequency does not change greatly.

  Although the preferred embodiments of the present invention have been described above, modifications other than those described above can be made.

  As described above, the thin film magnetic element according to the present invention can be used as a device such as an oscillator, a detector, a mixer, and a filter by utilizing the high frequency characteristics of the magnetoresistive effect element. Compared with high-frequency devices that use high-frequency characteristics composed of existing semiconductors, there are advantages due to miniaturization, impedance matching with transmission circuits, and variable frequency characteristics according to the present invention. , Can be substituted.

DESCRIPTION OF SYMBOLS 1 ... Thin film magnetic element 2 ... 2nd ferromagnetic layer 3 ... Nonmagnetic layer 4 ... 1st ferromagnetic layer 5 ... Nano contact hole 6 ... Current constriction layer 7- ..Nonmagnetic conductive region 8... Insulator 9... Lower electrode 10 .. Opposing surface 11... First projection surface 12. ..Oscillator 15 ... Magnetic field application mechanism 16 ... Signal generator 17 ... Power source 18 ... Signal amplifier

Claims (7)

A thin film magnetic element in which a current confinement layer having a plurality of nanocontact holes, a first ferromagnetic layer, and a second ferromagnetic layer are laminated,
A nonmagnetic layer between the first ferromagnetic layer and the second ferromagnetic layer;
The first ferromagnetic layer between the current confinement layer and the nonmagnetic layer;
A nonmagnetic conductive region disposed between the current confinement layer and the first ferromagnetic layer, or a nonmagnetic conductive region disposed on the opposite side of the current confinement layer from the first ferromagnetic layer;
The area Se of the facing surface of the nonmagnetic conductive region facing the first ferromagnetic layer and the area of the smallest cross section having the smallest area among the cross sections perpendicular to the stacking direction of the first ferromagnetic layer. A thin film magnetic element characterized in that Sf satisfies a relationship of Sf> Se.   The non-peripheral portion of the first ferromagnetic layer is annularly exposed with respect to a first projection surface obtained by projecting the opposing surface onto the interface on the opposing surface side of the first ferromagnetic layer. The thin film magnetic element according to claim 1, wherein a magnetic conductive region is disposed.   The thin film magnetic element according to claim 2, wherein a second projection surface obtained by projecting the facing surface onto the minimum cross section is included in the minimum cross section.   From the minimum value leo of the distance from the end of the second projection surface to the end of the minimum cross section, and the thickness from the facing surface to the interface on the nonmagnetic layer side of the first ferromagnetic layer, 4. The thin film magnetic element according to claim 3, wherein the thickness df excluding the thickness of the current confinement layer satisfies a relationship of leo> df.   5. The thin film magnetic element according to claim 4, wherein the thin film magnetic element has a plurality of the nonmagnetic conductive regions, and a shortest distance lei between the nonmagnetic conductive regions closest to each other satisfies a relationship of lei / 2> df.   6. The thin film according to claim 1, wherein an average distance dnc between the centers of the nano contact holes adjacent to each other satisfies a relationship of dnc / 2> df. Magnetic element.   A high frequency device comprising the thin film magnetic element according to claim 1.

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