JP2014110356A - Spin injection magnetization reversal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical modulation element including a TMR element structure reduced in magnetization reversal current using MgO as a barrier layer.SOLUTION: An optical modulation element 5 includes: a TMR element structure 1 formed by stacking a magnetization fixed layer 11, a barrier layer 12 comprising MgO, and a magnetization free layer 13; and an upper electrode 3 and a lower electrode 2 connected to above and below the TMR element structure. The lower electrode 2 comprises an amorphous Cu-Cr alloy. The magnetization fixed layer 11 comprises GdFe or is formed by stacking a CoFeB layer on a TbFeCo layer. Since an MgO film as the barrier layer 12 is formed on the magnetization fixed layer 11 comprising GdFe or on the CoFeB layer, the MgO film exhibits a strong (001) plane orientation, and since the lower electrode 2 is amorphous, the MgO film is not prevented from forming a (001) plane orientation. Accordingly, magnetization reversal current in the TMR element structure 1 can be reduced.

Description

  The present invention relates to a spin-injection magnetization reversal element suitable for an optical modulation element used in a spatial light modulator that emits incident light by spatially modulating the phase and amplitude of the light by a magneto-optic effect.

  A spin-injection magnetization reversal element includes two or more magnetic films (magnetic films), and is supplied with current from a vertically connected electrode (wiring) perpendicularly to the film surface. The magnetization direction of the part of the magnetic film is rotated (reversed) by 180 °, and is in the same direction as that of another magnetic film in which the magnetization direction does not change or in the opposite direction. In this spin-injection magnetization reversal element, the resistance between the upper and lower electrodes changes depending on whether the magnetizations of the magnetic films are in the same direction or in different directions, so that 1-bit data can be written / read as a magnetoresistive effect element. It can be carried out. That is, the spin-injection magnetization reversal element can constitute a magnetic random access memory (MRAM) by arranging memory cells having the spin injection magnetization reversal element in a matrix. Since the spin injection magnetization reversal element is extremely small in size and operates at a high speed, the RRAM is being studied and developed as a large-capacity magnetic memory.

  Known spin injection magnetization reversal elements include CPP-GMR (Current Perpendicular to the Plane Giant MagnetoResistance) elements and TMR (Tunnel MagnetoResistance) elements. In particular, a TMR element having a higher magnetoresistance ratio has been particularly studied. In recent years, in order to further increase the capacity and power saving of the MRAM, a magnetic material exhibiting magnetization in the direction perpendicular to the film surface (having perpendicular magnetic anisotropy) has been applied to a spin-injection magnetization switching element. Yes. A spin-injection magnetization reversal element having perpendicular magnetic anisotropy can be further miniaturized and can reduce a current (reversal current) required for magnetization reversal. The TMR element has a structure in which an extremely thin insulator film called a tunnel barrier or a barrier layer is sandwiched between two magnetic films. As a material for the barrier layer, magnesium oxide (MgO) that can further reduce the current required for magnetization reversal is suitable.

  Another application of the spin injection magnetization reversal element is a light modulation element mounted on a pixel of a spatial light modulator. The spin-injection magnetization reversal element as the light modulation element reverses the magnetization direction of the magnetic film by the magneto-optic effect in which the polarization direction of the light reflected or transmitted by the magnetic film changes (rotates), and the polarization direction of the light Is changed to a binary value. Also in the spatial light modulator, research and development are being conducted in the same manner as the MRAM as a material replacing the conventional liquid crystal for high definition and high speed (for example, see Patent Documents 1 and 2). The spin-injection magnetization reversal element used as the light modulation element desirably has a large change in the direction of polarization (high degree of light modulation). Therefore, also in the light modulation element, it is desirable to increase the degree of light modulation by the polar Kerr effect by using a perpendicular magnetic anisotropy spin-injection magnetization reversal element and making light incident substantially perpendicular to the film surface ( For example, see Non-Patent Document 1 and Patent Document 2.) Further, there is a demand for a material that can be suitably driven even when the number of pixels is increased to achieve higher definition and that can reduce the inversion current for power saving.

JP 2008-83686 A JP 2011-2522 A

K. Aoshima et. Al, “Spin transfer switching in current-perpendicular-to-plane spin valve observed by magneto-optical Kerr effect using visible light”, Appl. Phys. Lett. 91, 052507 (2007) SSP Parkin, C. Kaiser, A. Panchula, PM Rice, B. Hughes, M. Samant, SH Yang, “Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers”, Nature Materials, vol. 3, p. 862, Dec. 2004 Shinji Yuasa, Taro Nagahama, Akio Fukushima, Yoshishige Suzuki, Koji Ando, “Giant room-temperature magnetoresistance in single-crystal Fe / MgO / Fe magnetic tunnel junctions”, Nature Materials, vol.3, p.868, Dec. 2004. M. Nakayama, T. Kai, N. Shimomura, M. Amano, E. Kitagawa, T. Nagase, M. Yoshikawa, T. Kishi, S. Ikegawa, H. Yoda, “Spin transfer switching in TbCoFe / CoFeB / MgO / CoFeB / TbCoFe magnetic tunnel junctions with perpendicular magnetic anisotropy ”, J. Appl. Phys. 103, 07A710 (2008). Hitoshi Kubota, et al., “Spin-injection magnetization reversal in MTJ using MgO barrier”, Japanese Society of Applied Magnetics, Vol.145, p.43-48, 2006.01.30 D. D. Djayaprawira, et. Al, “230% room-temperature magnetoresistance in CoFeB / MgO / CoFeB magnetic tunnel junctions”, Appl. Phys. Lett. 86, 092502 (2005)

  In a TMR element using MgO as a barrier layer, a thin film made of (001) -oriented Fe or CoFe is provided on at least one of two magnetic films sandwiching the barrier layer at the interface with the barrier layer. It is known that the spin injection efficiency is dramatically improved and the reversal current is reduced (Non-Patent Documents 2 to 5). This is because MgO as the barrier layer has the crystals arranged in the (001) plane and the atoms are regularly arranged, so that electrons are injected without being scattered (Non-Patent Documents 2 to 4).

  However, the crystal structure of the MgO film tends to largely depend on the base. For example, it is known that an MgO film is provided on an amorphous CoFeB film rather than on a polycrystalline CoFe film (non-patent document 6).

  Further, a spin-injection magnetization reversal element such as a TMR element usually has a pair of electrodes connected vertically in order to pass a current in a direction perpendicular to the film surface. For this electrode, common metal electrode materials such as Cu, Au, Ag, Pt, and Pd are used. These metal electrode materials are easy to have a (111) plane structure having a face-centered cubic lattice (fcc) structure. When an MgO film is formed on an electrode having such a crystal structure, the magnetic film of the TMR element, There is a problem that the MgO film is difficult to have a (001) plane structure even through a thin film of CoFe or the like and a thin film of Ta or the like provided as a base of the TMR element.

  In addition, although the above-mentioned CoFe and CoFeB can be applied to a spin-injection magnetization reversal element as a magnetic material, these materials have in-plane magnetic anisotropy, and spin-injection magnetization with perpendicular magnetic anisotropy. There is a problem of not being an inverting element.

  In addition, in the TMR element in general, it is preferable for the magnetic tunnel junction that the flatness of the interface between the barrier layer and each of the two magnetic films sandwiching the barrier layer is good. However, when the electrode connected under the TMR element is formed by sputtering, for example, as a Cu single layer film to a thickness of 50 nm or more, the surface roughness (arithmetic average roughness) Ra usually exceeds 1 nm. For this reason, the magnetic film and the like formed thereon have the same surface roughness and the same surface roughness, and it is difficult to obtain sufficient flatness at the interface between the barrier layer and the magnetic film.

  The present invention has been devised in view of the above problems, and it is an object of the present invention to provide a TMR element having perpendicular magnetic anisotropy that can reduce the reversal current and is suitable for a light modulation element of a spatial light modulator. It is a problem to improve the flatness of the interface between the barrier layer and the magnetic film by setting MgO as the barrier layer to (001) plane orientation.

  In order to solve the above-mentioned problems, the MgO film exhibits a strong (001) plane orientation if the base is amorphous. Therefore, the present inventors have proposed an amorphous electrode material, particularly a lower electrode of a light modulation element. As a result, we have intensively studied metal electrode materials with high light reflectivity. Furthermore, the present inventors diligently researched on a magnetic material serving as a base for the MgO film, on a material in which the MgO film exhibits (001) plane orientation and has perpendicular magnetic anisotropy.

That is, the spin injection magnetization reversal element according to the present invention is a tunnel magnetoresistive element formed by laminating a magnetization fixed layer having perpendicular magnetic anisotropy, a barrier layer made of MgO, and a magnetization free layer having perpendicular magnetic anisotropy. And an electrode connected under the tunnel magnetoresistive element structure, the electrode having an amorphous Cu— composition of Cu _1-x Cr _x (0.07 <x <0.42) Made of Cr alloy. The magnetization fixed layer includes a layer made of Tb-Fe-Co and a layer made of Co-Fe-B, and the barrier layer is formed on a layer made of Co-Fe-B of the magnetization fixed layer. It is characterized by being laminated.

  With such a configuration, the MgO film is formed on the electrode made of an amorphous alloy, so that the flatness of the interface is good, and further, the MgO film is strong because it is laminated on the layer of Co—Fe—B of the magnetization fixed layer. Since it is easily formed in (001) plane orientation and the magnetization fixed layer includes a layer made of Tb—Fe—Co, it exhibits perpendicular magnetic anisotropy.

  In another spin injection magnetization reversal element according to the present invention, the magnetization fixed layer of the tunnel magnetoresistive effect element structure includes a layer made of Gd-Fe, and the barrier layer is made of Gd-Fe of the magnetization fixed layer. It is characterized by being laminated in a layer.

  Alternatively, in the spin-injection magnetization switching element according to the present invention, the tunnel magnetoresistive element structure has a magnetization free layer having perpendicular magnetic anisotropy, a barrier layer made of MgO, and a magnetization fixed layer having perpendicular magnetic anisotropy May be laminated. In the case of such a structure, the magnetization free layer includes a layer made of Gd—Fe instead of the magnetization fixed layer, and the barrier layer is laminated on the layer of Gd—Fe of the magnetization free layer. Features.

  With this configuration, since the MgO film is laminated on the electrode made of an amorphous alloy and the Gd—Fe layer of the magnetization fixed layer or the magnetization free layer, it is easily formed in a strong (001) plane orientation, A spin injection magnetization reversal element having perpendicular magnetic anisotropy can be formed by -Fe.

  Furthermore, it is preferable that the spin transfer magnetization switching element according to the present invention includes a Ta film stacked on the electrode. With this configuration, the MgO film can be formed with a stronger (001) plane orientation.

  The spin-injection magnetization reversal element according to the present invention is a light modulation element that emits light while changing the direction of polarization of incident light. With such a configuration, it is possible to obtain a light modulation element that reflects light by an electrode connected to the lower side when light is incident from above.

  According to the spin-injection magnetization reversal element according to the present invention, by providing the barrier layer with the MgO film exhibiting a strong (001) plane orientation, a tunnel magnetoresistive effect element structure capable of reversal of magnetization with a low current is obtained, and a perpendicular magnetic anomaly is obtained. Since the optical modulation element has a directivity, it can be a reflective spatial light modulator that has a high magneto-optical effect and saves power even when the resolution is increased.

It is sectional drawing which shows the structure of the light modulation element which consists of a spin injection magnetization reversal element concerning 1st Embodiment of this invention. It is a schematic diagram explaining operation | movement of the spin injection magnetization reversal element which concerns on embodiment of this invention, (a), (b) is spin injection magnetization reversal, (c), (d) is a light modulation element and magnetoresistive. It is sectional drawing explaining the operation | movement as an effect element. (A), (b) is sectional drawing which shows the structure of the light modulation element which consists of a spin injection magnetization reversal element based on the modification of 1st Embodiment of this invention. It is sectional drawing which shows the structure of the light modulation element which consists of a spin injection magnetization reversal element concerning 2nd Embodiment of this invention. It is sectional drawing which shows the structure of a memory cell provided with the magnetoresistive effect element which consists of a spin injection magnetization reversal element concerning 3rd Embodiment of this invention. It is sectional drawing which shows the structure of the magnetoresistive effect element which consists of a spin injection magnetization reversal element concerning 4th Embodiment of this invention, and its modification, (a) is 4th Embodiment, (b) is 4th Embodiment. It is a modified example of. It is a schematic diagram explaining operation | movement of the spin injection magnetization reversal element which concerns on embodiment of this invention, (a), (b) is spin injection magnetization reversal, (c), (d) is a magnetoresistive effect element. It is sectional drawing explaining operation | movement. It is sectional drawing which shows the structure of the light modulation element which consists of a spin injection magnetization reversal element based on 5th Embodiment of this invention. It is sectional drawing which shows the structure of the light modulation element which consists of a spin injection magnetization reversal element based on the modification of 5th Embodiment of this invention. It is an X-ray diffraction pattern of the sample which simulated the tunnel magnetoresistive element structure of the spin injection magnetization reversal element of an Example, (a) is the spin injection magnetization reversal element which concerns on 1st Embodiment, (b) is 2nd Embodiment. Is a spin-injection magnetization reversal element. It is a X-ray diffraction pattern of the sample which simulated the spin injection magnetization reversal element of an Example, (a) is the spin injection magnetization reversal element which concerns on 1st Embodiment, (b) is the spin which concerns on the modification of 1st Embodiment. An injection magnetization reversal element, (c) is a spin injection magnetization reversal element of a comparative example, and (d) is a conventional spin injection magnetization reversal element. FIG. 3 is a magnetization curve expressed by magnetic field dependence of the Kerr rotation angle of a sample of the spin injection magnetization reversal element of the example, (a) is the spin injection magnetization reversal element according to the first embodiment, and (b) is the second embodiment. (C) is a spin-injection magnetization reversal element of a comparative example. It is an X-ray diffraction pattern of the sample which simulated the lower electrode of the spin injection magnetization reversal element of an Example, (a)-(e) is spin injection magnetization which concerns on 1st Embodiment which changed the composition of Cu-Cr alloy. It is an inverting element.

Hereinafter, embodiments for realizing a spin transfer magnetization switching element according to the present invention will be described with reference to the drawings.
A spin injection magnetization reversal element according to an embodiment of the present invention is a light modulation element constituting a pixel of a spatial light modulator (means for displaying information (bright / dark) in a minimum unit of display by the spatial light modulator) The light incident from above is modulated into different binary light (polarized light component), reflected by the electrode connected below, and emitted upward.

[First Embodiment]
As shown in FIG. 1, the light modulation element (spin injection magnetization reversal element) 5 according to the first embodiment of the present invention includes a lower electrode (electrode) 2, a magnetization fixed layer 11, a barrier layer 12, a magnetization free layer 13, In this configuration, the protective film 16 and the upper electrode 3 are laminated in this order. The optical modulation element 5 is a TMR formed by laminating a magnetization fixed layer 11 whose magnetization is fixed in one direction and a magnetization free layer 13 whose magnetization direction is rotatable with a barrier layer 12 made of MgO as an insulator interposed therebetween. An element structure (tunnel magnetoresistive element structure) 1 is provided. The light modulation element 5 includes the TMR element structure 1, the lower electrode 2 and the upper electrode 3 (hereinafter referred to as electrodes 2 and 3 as appropriate) as a pair of electrodes, in both directions perpendicular to the film surface (in the vertical direction). ) Supply current. The light modulation element 5 further includes a protective film 16 on the TMR element structure 1 (magnetization free layer 13) as necessary to protect each layer of the TMR element structure 1 from damage in the manufacturing process of the light modulation element 5. Is provided. The light modulation element 5 may further include a base film made of a metal thin film (not shown) under the TMR element structure 1 in order to obtain adhesion to the lower electrode 2.

  The light modulation elements 5 are arranged in a two-dimensional array in the film surface direction on the substrate 7 so as to be pixels of the spatial light modulator, and one of the pair of electrodes 2 and 3 is arranged in the row direction and the other is arranged in the column. Each extends in the direction and is shared (not shown). Therefore, between the light modulation elements 5 and 5, specifically, between the TMR element structures 1 and 1, between the electrodes 2 and 3, between the lower electrodes 2 and 2, and between the upper electrodes 3 and 3 (between wirings), The insulating layer 6 is filled. The TMR element structure 1 has, for example, a rectangular shape in plan view (not shown), and preferably has an area corresponding to 300 nm × 400 nm or less in order to suitably reverse magnetization. The length is at least equal to or greater than the diffraction limit of incident light (about ½ of the wavelength). The layers 11, 12, 13 and the protective film 16 constituting the TMR element structure 1 are continuously formed by a known method such as a sputtering method or a molecular beam epitaxy (MBE) method, and are stacked on the substrate 7 to form an electron. It is processed into a desired planar view shape by line lithography, ion beam milling, or the like.

(Magnetization reversal operation)
Here, the magnetization reversal operation of the TMR element structure 1 in the light modulation element 5 will be described with reference to FIGS. In FIG. 2, the protective film 16 is not shown. In the TMR element structure 1 which is a spin injection magnetization reversal element, the magnetization direction is reversed when the magnetization free layer 13 is injected with electrons having spins in the reverse direction (spin injection magnetization reversal, hereinafter referred to as magnetization reversal as appropriate). To do. Specifically, as shown in FIG. 2A, the upper electrode 3 is set to “+” and the lower electrode 2 is set to “−”, and the TMR element structure 1 is changed from the magnetization free layer 13 side to the magnetization fixed layer 11. A current I _W is supplied to inject electrons from the magnetization fixed layer 11 side. Then, an electron d _D having a downward spin opposite to the magnetization of the magnetization fixed layer 11 is discriminated by the magnetization fixed layer 11 whose magnetization is fixed upward, and the magnetization free layer 13 has an electron d having an upward spin. _U is biased and the magnetization reverses upward. On the other hand, as shown in FIG. 2B, the upper electrode 3 is set to “−”, the lower electrode 2 is set to “+”, and the current I is transferred from the magnetization fixed layer 11 side to the magnetization free layer 13 in the TMR element structure 1. _W is supplied to inject electrons from the magnetization free layer 13 side. Then, electrons d _D having a downward spin are discriminated by the magnetization fixed layer 11 and remain in the magnetization free layer 13, so that the magnetization of the magnetization free layer 13 is reversed downward.

As described above, in the TMR element structure 1, the magnetization direction of the magnetization free layer 13 is the same as that of the magnetization fixed layer 11 by supplying a current in a direction perpendicular to the film surface by the pair of electrodes 3 and 2 connected to the upper and lower surfaces. (Parallel) or 180 ° different directions (anti-parallel). Although the barrier layer 12 of the TMR element structure 1 is an insulator, a very small current (tunnel current) flows because the barrier layer 12 is extremely thin, such as several nm or less. Furthermore, since the barrier layer 12 is MgO exhibiting (001) plane orientation, the spin injection efficiency is improved. Further, in the TMR element structure 1, if the magnetization of the magnetization free layer 13 exhibits either parallel or antiparallel magnetization, the magnetization free layer until the current (I _W ) for reversing the magnetization is supplied. Magnetization is held by the coercive force of 13 (see FIGS. 2C and 2D). Therefore, as a current supplied to the TMR element structure 1, a current (DC pulse current) that temporarily reaches a current value that reverses the magnetization direction, such as a pulse current, can be used. Hereinafter, elements constituting the light modulation element 5 will be described in detail.

(TMR element structure)
In the TMR element structure 1 of the light modulation element 5 according to the present embodiment, the magnetization fixed layer 11 is composed of a transition metal (TM) and a rare earth metal (RE), which are amorphous and have a perpendicular magnetic anisotropy. It is formed of a Gd—Fe alloy which is a kind of alloy (RE-TM alloy). The magnetization fixed layer 11 is provided in the lower layer of the barrier layer 12 made of MgO together with the lower electrode 2 which will be described later, and further serves as a direct base, so that it is formed of a Gd—Fe alloy which is an amorphous material. Thus, MgO can be made into a strong (001) plane oriented crystal. In addition, since the magnetization fixed layer 11 is fixed in magnetization, the composition and thickness of the Gd—Fe alloy are set so that the coercive force is larger than that of the magnetization free layer 13. Is preferably set in accordance with the magnetization free layer 13 in the range of 3 to 50 nm.

  In the present invention, the term “amorphous” refers to a material having a fine crystal structure that is difficult to detect by X-ray diffraction (XRD), that is, a microcrystalline structure. By making the magnetization fixed layer 11 and the lower electrode 2 provided below the barrier layer 12 amorphous, MgO forming the barrier layer 12 can be made a strong (001) -oriented crystal.

  The barrier layer 12 is made of (001) -oriented MgO, and its thickness is preferably 0.1 to 2 nm. By using MgO having such a crystal structure as the barrier layer 12, electrons are injected without being scattered in the TMR element structure 1, so that the inversion current of the TMR element structure 1 can be reduced.

  The magnetization free layer 13 can be formed of a known magnetic material as a magnetization free layer of a TMR element having perpendicular magnetic anisotropy, and a material having a high magneto-optic effect is preferably applied. Specifically, for example, a [Co / Pt] × n, [Co / Pd] × n multilayer film including a transition metal such as Fe, Co, or Ni and a noble metal such as Pt or Pd, or the transition metal Examples include alloys (RE-TM alloys) with rare earth metals such as Nd, Gd, Tb, Dy, and Ho. The magnetization free layer 13 preferably has a thickness in the range of 1 to 20 nm. Further, in order to make the coercive force smaller than that of the magnetization fixed layer 11, the magnetization free layer 13 may be formed of a magnetic material having a small coercive force, Is preferably made thinner than the magnetization fixed layer 11. For example, when a Gd—Fe alloy is applied to the magnetization free layer 13 in the same manner as the magnetization fixed layer 11, the composition of Fe may be larger than that of the magnetization fixed layer 11 in order to reduce the coercive force.

  In the TMR element structure 1, the magnetization free layer 13 may further include a magnetic metal film containing a transition metal at the interface with the barrier layer 12 (not shown). Specifically, the magnetic metal film includes at least one transition metal selected from Fe, Co, and Ni, or an alloy containing the transition metal, such as Co—Fe, Co—Fe—B, Ni—Fe, A Heusler alloy made of Co—Fe—Si or having a particularly high spin polarizability (theoretically 1) can also be used. The magnetic metal film preferably has a thickness in the range of 0.1 to 1 nm. The magnetization free layer 13 is provided with such a magnetic metal film at the interface with the barrier layer 12, thereby increasing the spin polarization at the interface and being injected into the magnetization free layer 13 through the barrier layer 12. Therefore, the reversal current of the TMR element structure 1 can be reduced. Particularly, when the barrier layer 12 has the same (001) orientation Fe as the MgO, the (001) orientation oriented Co by being formed on the (001) orientation MgO surface, and heat treatment after the formation Further, Co—Fe—B that crystallizes from the interface with the barrier layer 12 and exhibits (001) plane orientation is preferable. Magnetic metal films made of these materials have good lattice matching with MgO, and the TMR element structure 1 can further reduce the reversal current when a coherent tunnel current flows. However, when the magnetization free layer 13 is made of a Gd—Fe alloy, it may not show perpendicular magnetic anisotropy (becomes in-plane magnetic anisotropy) when combined with the magnetic metal film. It is preferable not to provide it. This is considered to be due to the influence of the demagnetizing field component of Fe in the Gd—Fe alloy being enhanced by Fe such as Co—Fe—B.

  The protective film 16 is provided on the TMR element structure 1 in order to protect each layer of the TMR element structure 1, particularly the uppermost magnetization free layer 13 from damage in the manufacturing process of the light modulation element 5. The damage in the manufacturing process includes, for example, impregnation with a developing solution at the time of resist formation, and oxidation in particular when the uppermost magnetic free layer 13 is formed of an easily oxidizable RE-TM alloy. The protective film 16 is a laminate in which two or more metal films made of a non-magnetic metal material such as Ru, Ta, Cu, Pt, or Au, or metal films made of different metal materials such as Cu / Ta, Cu / Ru are laminated. Consists of a membrane. If the thickness of the protective film 16 is less than 1 nm, it is difficult to form a continuous (pinhole-free) film. On the other hand, even if the thickness exceeds 10 nm, the effect of protecting the magnetization free layer 13 and the like in the manufacturing process However, the transmitted light quantity of incident light from above the light modulation element 5 is attenuated. Therefore, the thickness of the protective film 16 is preferably 1 to 10 nm.

  A base film (not shown) provided under the TMR element structure 1 (magnetization pinned layer 11) to provide adhesion to the lower electrode 2 may be made of Ru or Ta among nonmagnetic metal materials. preferable. With these metal films, the (001) plane orientation of MgO serving as the barrier layer 12 provided with the magnetization fixed layer 11 interposed therebetween is not hindered. If the thickness of the underlying film is less than 1 nm, it is difficult to form a continuous film (without pinholes) as in the case of the protective film 16, while even if the thickness exceeds 10 nm, the adhesion is more than that. Since it does not improve, it is preferable to set it as 1-10 nm.

(Lower electrode)
The lower electrode 2 is composed of a CuCr alloy layer 21 made of an amorphous Cu—Cr alloy. Since the lower electrode 2 is made of an amorphous Cu—Cr alloy, the (001) plane orientation of MgO serving as the barrier layer 12 formed on the magnetization fixed layer 11 is not disturbed. In addition, since the amorphous Cu—Cr alloy does not become rough even when it is formed thick by sputtering (arithmetic average roughness Ra: several Å), in the TMR element structure 1 formed thereon, the barrier layer 12 is excellent in flatness of the interface between each of the layers 11 and 13 and is preferable for a magnetic tunnel junction. In order to make the CuCr alloy layer 21 amorphous, the composition is Cu _1-x Cr _x (0.07 <x <0.42) (the Cr content is more than 7 at% and less than 42 at%). It consists of a Cu-Cr alloy. A Cu—Cr alloy is unlikely to be amorphous when the composition is outside this range. In particular, when the Cr content is 7 at% or less, the Cu—Cr alloy becomes an alloy showing a (111) plane structure which is a crystal structure of Cu, and is provided therebetween. Even if the magnetization fixed layer 11 is amorphous, the (001) plane orientation of MgO serving as the barrier layer 12 is hindered. On the other hand, the Cu—Cr alloy is an alloy having a (110) plane structure which is a crystal structure of Cr when the Cr content is 42 at% or more. As described above, amorphous is a microcrystalline structure, and amorphous Cu—Cr alloy is detected by X-ray diffraction (XRD) and has (111) plane and (110) plane. The detection intensity indicates a structure lower than that of Cu alone and Cr alone, respectively. Moreover, since Cr has a higher resistance than Cu (about 9 times that of Cu), it is preferable for the content rate to be lower in the composition range in order to suppress the resistance of the lower electrode 2. The thickness of the CuCr alloy layer 21 is preferably 10 nm or more so that MgO serving as the barrier layer 12 formed thereon has a (001) plane orientation. Further, the lower electrode 2 may include a Ta film (not shown) as a base for forming the CuCr alloy layer 21.

(Upper electrode)
The upper electrode 3 is made of a transparent electrode material so that light can pass therethrough. Transparent electrode materials include, for example, indium zinc oxide (IZO), indium tin oxide (ITO), tin oxide (SnO ₂ ), antimony oxide-tin oxide system (ATO), oxidation zinc (ZnO), fluorine-doped tin oxide (FTO), consisting of a known transparent electrode material such as indium oxide (in ₂ O _3). In particular, IZO is most preferable in terms of specific resistance and ease of film formation. These transparent electrode materials are formed into a film by a known method such as a sputtering method, a vacuum deposition method, or a coating method.

  When the electrode (wiring) is made of a transparent electrode material, it is preferable to provide a metal film between the electrode and the TMR element structure 1 connected to the electrode. That is, in the upper electrode 3 made of a transparent electrode material, it is preferable to laminate a metal film as a base between the TMR element structure 1 (not shown). By interposing a metal film between the TMR element structure 1 and the upper electrode 3 made of a transparent electrode material having a higher resistance than the electrode metal material, the contact resistance between the upper electrode 3 and the TMR element structure 1 is reduced. To increase the response speed.

  As the metal film constituting the base of the transparent electrode, for example, Au, Ru, Ta, or an alloy composed of two or more of these metals can be used, and these metals are obtained by a known method such as a sputtering method. A film is formed. In order to further improve the adhesion between the metal film and the upper layer, that is, the transparent electrode and further reduce the contact resistance, the metal film may be continuously formed in the vacuum processing chamber with the transparent electrode material. preferable. When the thickness of the metal film is less than 1 nm, it is difficult to form a continuous film (without pinholes). On the other hand, when the thickness exceeds 10 nm, the amount of transmitted light is reduced.

  The substrate 7 is a base for arranging the light modulation elements 5 two-dimensionally, and is a broad substrate for manufacturing the light modulation elements 5. As the substrate 7, for example, a known substrate such as a Si substrate or glass whose surface is thermally oxidized can be applied.

The insulating layer 6 is formed between the light modulation elements 5 and 5 arranged in a two-dimensional array, that is, between the TMR element structures 1 and 1, between the electrodes 2 and 3 (interlayer), between the lower electrodes 2 and 2, and the upper electrode 3. , 3 (between wirings) are provided to insulate each other. For the insulating layer 6, for example, a known insulating material such as an oxide film such as SiO ₂ or Al ₂ O ₃ or Si nitride (Si ₃ N ₄ ) can be applied. However, since the TMR element structure 1 includes a layer made of a highly oxidizable RE-TM alloy such as a Gd—Fe alloy, the TMR element structure 1 is provided in a portion in contact with the TMR element structure 1 (between the TMR element structures 1 and 1). The insulating layer 6 is preferably made of a non-oxide that does not contain O (oxygen) such as Si nitride or MgF ₂ .

(Manufacturing method of light modulation element)
Next, an example of a method for manufacturing the light modulation element 5 will be described. As described above, the light modulation element according to this embodiment is manufactured as a spatial light modulator arranged in a two-dimensional array on a substrate.

First, the lower electrode 2 is formed. A Cu—Cr alloy having a desired composition is formed on the surface of the substrate 7 by a sputtering method or the like to form the stripe-shaped lower electrode 2. Then, an insulating film such as SiO ₂ (which becomes the insulating layer 6) is deposited between the lower electrodes 2 and ₂ .

  Next, the TMR element structure 1 is formed. On the lower electrode 2 (and the insulating layer 6), each material of the magnetization fixed layer 11, the barrier layer 12, the magnetization free layer 13, and the protective film 16 is continuously formed, and these layers are formed by electron beam lithography and ion The TMR element structure 1 is formed by molding into the shape in plan view by a beam milling method or the like. An insulating film is formed with the resist used as a mask in the molding process remaining, and is deposited between the TMR element structures 1 and 1, and the resist is removed together with the insulating film thereon (lift-off). And

  Next, the upper electrode 3 is formed. On the TMR element structure 1 and the insulating layer 6, a metal film as a base and a transparent electrode material are continuously formed and formed in a stripe shape orthogonal to the lower electrode 2 to form the upper electrode 3. Finally, an insulating film is deposited between the upper electrodes 3 and 3 to form the insulating layer 6 and the light modulation element 5.

  In the light modulation elements 5 of all the pixels in the spatial light modulator, the magnetization of the magnetization fixed layer 11 needs to be fixed in the same direction. Since the magnetization fixed layer 11 does not reverse the magnetization when supplied with current, an initial magnetic field that is larger than the coercive force of the magnetization fixed layer 11 is applied from the outside to align the magnetization direction of the magnetization fixed layer 11 upward (see FIG. 2), for example. Set up. This initial setting is not limited to the completed light modulation element 5 (spatial light modulator), that is, after the deposition of the magnetic material for the magnetization fixed layer 11 in the middle of the production process. Even it can be implemented.

(Operation of light modulator)
The operation of the light modulation element according to this embodiment will be described with reference to FIGS. Light incident on the light modulation element 5 from above passes through the upper electrode 3 and reaches the TMR element structure 1, is reflected by the lower electrode 2, passes through the upper electrode 3 again, and is emitted upward. At that time, the polarization plane of the light rotates (rotates) and is emitted by the magneto-optic effect of the magnetization free layer 13 which is a magnetic material. Further, if the magnetization direction of the magnetic material is different by 180 °, the direction of optical rotation due to the magneto-optical effect of the magnetic material is reversed. Therefore, the optical rotation angles in the light modulation element 5 (TMR element structure 1) in which the magnetization directions of the magnetization free layer 13 are different from each other by 180 ° as shown in FIGS. 2C and 2D are −θk and + θk, which are opposite to each other. The plane of polarization rotates. The magnetization reversal operation of the TMR element structure 1 of the light modulation element 5 is as described with reference to FIGS. 2 (a) and 2 (b). Therefore, the light modulation element 5 changes the direction of polarization of the emitted light by switching the direction (positive / negative) of the current I _W and supplying it. The optical rotation angles −θk and + θk are not limited to optical rotation (Kerr rotation) by one reflection on the magnetization free layer 13, and include, for example, angles accumulated by multiple reflections in the light modulation element 5.

  The light modulation elements 5 can be two-dimensionally arranged as pixels and operated in the same manner as a known reflection type spatial light modulator (see, for example, Patent Document 2). The incident light to the light modulation element 5 is, for example, light of a specific polarization component transmitted through a polarizer from a laser light source, and the emitted light is another polarizer, and −θk, + θk with respect to the incident light. It is possible to block the light rotated to one of the light and take out the light rotated to the other (not shown).

  In FIGS. 2C and 2D, the incident angle of incident light is shown to be inclined in order to make it easy to distinguish the paths of incident light and outgoing light. In order to increase the Kerr rotation angle, it is preferable that the incidence is perpendicular to the film surface, that is, the incidence angle is close to 0 °, and specifically, the incidence angle is preferably within 30 °. Most preferably, the incident light is perpendicular to the film surface, that is, the incident angle is set to 0 °. In this case, since the paths of the incident light and the emitted light coincide with each other, the light is incident on the light modulator 5 (the polarization for incident light). A half mirror may be arranged between the optical element and the outgoing light alone, and the outgoing light polarizer may be arranged on the reflected side.

(Modification)
In the spin-injection magnetization switching element according to the present invention, MgO serving as a barrier layer can have a stronger (001) plane orientation by further stacking a Ta film on the lower electrode made of an amorphous alloy. Hereinafter, a spin transfer magnetization switching element according to a modification of the first embodiment will be described. The same elements as those in the first embodiment (see FIG. 1) are denoted by the same reference numerals, and description thereof is omitted.

  The light modulation element (spin injection magnetization reversal element) 5 according to the modification of the first embodiment has the same structure as that of the first embodiment except for the lower electrode (electrode) 2 connected under the TMR element structure 1. As shown in FIG. 3A, the lower electrode 2B is formed by further laminating a Ta film 22 and a Ru film 23 on the lower electrode 2 (CuCr alloy layer 21) of the first embodiment. Ta easily adopts a (110) plane structure having a body-centered cubic lattice (bcc) structure, and MgO formed thereon via an amorphous magnetic film or the like has a stronger (001) plane orientation. can do. However, since Ta is easily oxidized, a Ru film 23 is provided as a protective film for the Ta film 22. The Ta film 22 is preferably set to a thickness of 1 nm or more in order to sufficiently obtain the above-described effect. On the other hand, if the thickness is excessively increased, the effect is reduced. Therefore, the thickness is preferably set to 50 nm or less. The Ru film 23 is preferably 2 nm or more in thickness so as to form a continuous film.

  As described above, Ta can be applied as the base film of the TMR element structure 1. In this case, by forming the base film (Ta film) directly on the lower electrode 2 (CuCr alloy layer 21), the same effect as that of the lower electrode 2B can be obtained, and further, the base film (Ta film) can be continuously formed. Since each layer of the TMR element structure 1 is formed, it is not necessary to stack the Ru film.

  Here, the thickness of the lower electrodes 2 and 2B can be set according to the required wiring resistance and the like. However, the CuCr alloy layer 21 formed of an amorphous Cu—Cr alloy has a higher resistance to Cr (resistance: 12) than Cu (resistance: 1.67 μΩ · cm) compared to a general Cu electrode. .9 .mu..OMEGA..multidot.cm) and further amorphous, the resistance may be increased about 10 times. Further, since Ta (resistance: 12.5 μΩ · cm) is also high in resistance, the lower electrode 2B on which the Ta film 22 is laminated also has higher resistance than the Cu electrode. Therefore, in order to reduce the wiring resistance, the lower electrodes 2 and 2B (CuCr alloy layer 21, Ta film 22) may be formed thick, but a layer made of a low resistance material is formed under the CuCr alloy layer 21. It is preferable to provide it because the entire thickness is suppressed.

  For example, even when a Cu layer having a (111) plane structure is present in the lower layer, a sufficient thickness of the amorphous CuCr alloy layer 21 is provided on the Cu layer. It can be (001) plane orientation. That is, as shown in FIG. 3B, the CuCr alloy layer 21 is laminated on a layer (Cu layer) 24 having low resistance Cu (pure Cu or crystalline Cu alloy) used as a general electrode material. May be. The lower electrode 2C shown in FIG. 3B is formed by further laminating a Ta film 22 and a Ru film 23 on the CuCr alloy layer 21 in the same manner as the lower electrode 2B (see FIG. 3A). The lower electrode 2A (see FIG. 4) having a two-layer structure of the Cu layer 24 and the CuCr alloy layer 21 may be used. When a single layer of Cu is formed by sputtering to a thickness of 50 nm or more, the surface becomes rough (arithmetic average roughness Ra: more than 1 nm), and the surface shape of the CuCr alloy layer 21 and the like formed thereon is also increased. Therefore, the flatness of each interface between the barrier layer 12 and the layers 11 and 13 in the TMR element structure 1 is lowered, which is not preferable for the magnetic tunnel junction. Accordingly, the lower electrodes 2A and 2C are Cu / Ta multilayer films in which the Cu single layer is about 15 nm thick in the Cu layer 24, and, for example, a laminated film is repeatedly stacked with a Ta film having a thickness of about 3 nm interposed therebetween. More preferably.

  As described above, since the light modulation element according to the first embodiment of the present invention and the modification thereof can be reversed in magnetization with a small current density by the TMR element structure having excellent spin injection efficiency, high-definition spatial light Since the TMR element structure that saves power as a modulator and has perpendicular magnetic anisotropy can increase the degree of light modulation by the polar Kerr effect, the spatial light modulator has good contrast.

[Second Embodiment]
The spin-injection magnetization reversal element according to the present invention can also have a TMR element structure in which Tb—Fe—Co suitable for the magnetization fixed layer is applied and has a strong perpendicular magnetic anisotropy with a larger coercive force. However, Tb—Fe—Co cannot make MgO sufficiently strong (001) plane orientation, and thus has the following configuration. The light modulation element according to the second embodiment will be described below. The same elements as those in the first embodiment and the modifications thereof (see FIGS. 1 to 3) are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 4, in the TMR element structure 1A of the light modulation element 5A according to the second embodiment, the magnetization fixed layer 11A includes a layer (TbFeCo layer) 11a made of Tb—Fe—Co, and further, Co A layer (CoFeB layer) 11b made of -Fe-B is provided. That is, the magnetization fixed layer 11A of the TMR element structure 1A has a laminated structure of two layers. The TbFeCo layer 11a has a large coercive force and a strong perpendicular magnetic anisotropy, and the CoFeB layer 11b is used as a base of the barrier layer 12. By laminating, MgO (barrier layer 12) formed on the surface can be made a strong (001) plane crystal.

  Since the TbFeCo layer 11a is made of a kind of Tb—Fe—Co, which is an amorphous RE-TM alloy like Gd—Fe, the (001) plane orientation of MgO serving as the barrier layer 12 is not hindered. The TbFeCo layer 11a can have the same composition and thickness as those applied as the magnetization fixed layer of the perpendicular magnetic anisotropy spin-injection magnetization switching element, and the thickness is the same as that of the magnetization fixed layer 11 of the first embodiment. The thickness is preferably in the range of 3 to 50 nm.

  The CoFeB layer 11b is provided as a base of the barrier layer 12 in order to make MgO formed on the surface thereof into a strong (001) -oriented crystal. Further, the CoFeB layer 11b is amorphous in the same way as the TbFeCo layer 11a at the time of film formation (when manufacturing the TMR element structure 1A). However, as described above, when the heat treatment is performed, the interface with the barrier layer 12 is used. From this, it is crystallized into a bcc structure with good lattice matching with (001) -oriented MgO. In the TMR element structure 1A, the magnetization fixed layer 11A includes such a CoFeB layer 11b at the interface with the barrier layer 12, thereby increasing the spin polarization at the interface and allowing the magnetization free through the barrier layer 12. Since the spin torque due to the spin injected into the layer 13 increases and a coherent tunnel current flows, the inversion current can be reduced. Although Co—Fe—B itself has in-plane magnetic anisotropy, the CoFeB layer 11b is laminated on the TbFeCo layer 11a having strong perpendicular magnetic anisotropy, so that the magnetization fixed layer 11A as a whole becomes perpendicular magnetic. Shows anisotropy. The CoFeB layer 11b preferably has a thickness of 1.0 nm or more so that MgO forming the barrier layer 12 has a (001) orientation. On the other hand, since the in-plane magnetic anisotropy becomes stronger as the CoFeB layer 11b becomes thicker, the thickness is preferably set to 2.0 nm or less.

  The barrier layer 12 and the magnetization free layer 13 have the same configurations as those in the first embodiment, and the magnetization free layer 13 may include a magnetic metal film at the interface with the barrier layer 12. Such a TMR element structure 1A performs the magnetization reversal and light modulation operations (see FIG. 2), similarly to the TMR element structure 1 of the light modulation element 5 according to the first embodiment.

  As shown in FIG. 4, the light modulation element 5 </ b> A includes a lower electrode 2 </ b> A formed by laminating a CuCr alloy layer 21 on a Cu layer 24, but the lower electrode 2 (see FIG. 1) including only the CuCr alloy layer 21 or a CuCr alloy. The lower electrodes 2B and 2C (see FIG. 3) in which the Ta film 22 and the Ru film 23 are stacked on the layer 21 may be provided, and the same effects as those of the first embodiment and the modification thereof are obtained.

  As described above, similarly to the first embodiment, the light modulation element according to the second embodiment of the present invention can be a power-saving and high-contrast spatial light modulator, and further, Tb-Fe. By applying -Co to the magnetization fixed layer having the TMR element structure, stable operation is achieved.

[Third Embodiment]
A spin injection magnetization reversal element according to another embodiment of the present invention is a magnetoresistive effect element, and is connected to a transistor by an electrode (wiring) to constitute a memory cell of a magnetic random access memory (MRAM). The spin injection magnetization switching element according to the third embodiment will be described below. The same elements as those in the first and second embodiments (see FIGS. 1 to 4) are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 5, a magnetoresistive effect element (spin injection magnetization reversal element) 5B according to the third embodiment of the present invention includes a lower electrode (electrode) 2B, a magnetization free layer 13B, a barrier layer 12, and a magnetization fixed layer 11B. The protective film 16 and the upper electrode 3A are stacked in this order. That is, the magnetoresistive element 5B includes a TMR element structure (tunnel magnetoresistive element structure) 1B formed by laminating a magnetization fixed layer 11B and a magnetization free layer 13B with a barrier layer 12 made of MgO interposed therebetween, and this TMR element structure 1B. The lower electrode 2B and the upper electrode 3A are connected as a pair of electrodes, and current is supplied perpendicular to the film surface. Further, the magnetoresistive effect element 5B is connected to the drain 7d of the MOSFET (metal oxide semiconductor field effect transistor) formed on the substrate 7A at the lower electrode 2B and the drain connection portion 43 connected to the lower electrode 2B. An MRAM memory cell is formed. That is, in the magnetoresistive effect element 5B, the lower electrode 2B is a wiring in the memory cell for connection to the drain 7d of the MOSFET. On the other hand, the upper electrode 3A is extended in one direction in the plane (left and right direction in FIG. 5) as an MRAM bit line.

  In the TMR element structure 1B, the stacking order of the magnetization fixed layer 11 and the magnetization free layer 13 in the TMR element structure 1 of the light modulation element (spin injection magnetization switching element) 5 (see FIG. 1) according to the first embodiment is changed. Structure. Further, unlike the first and second embodiments, the TMR element structure 1B has no lower limit (minimum area) in plan view for light modulation, and the magnetization of the magnetization free layer 13B may be held. . Specifically, the TMR element structure 1B preferably has an area corresponding to about 300 nm × 100 nm, which is the size of a general spin-injection magnetization reversal element in plan view, in order to more suitably reverse the magnetization. In the TMR element structure 1B, in order to make MgO forming the barrier layer 12 into a crystal having a strong (001) plane orientation, the magnetization free layer 13B serving as the base is formed of a Gd—Fe alloy. The Gd—Fe alloy is as described in the first embodiment. Further, the barrier layer 12 has the same configuration as that of the first embodiment.

The magnetization fixed layer 11B is not limited to amorphous because no barrier layer (MgO) is provided thereon, and can be formed of a known magnetic material as a magnetization fixed layer of a TMR element having perpendicular magnetic anisotropy. It is preferable to apply a material having a large coercive force. Specifically, for example, a multilayer film of [Co / Pt] × n, [Co / Pd] × n, or Tb—Fe— containing a transition metal such as Fe, Co, and Ni and a noble metal such as Pt and Pd. and RE-TM alloy, such as Co, FePt was L1 ₀ type ordered alloys, FePd, and the like. Further, the magnetization fixed layer 11B may include a magnetic metal film containing a transition metal at the interface with the barrier layer 12 (not shown), like the magnetization free layer 13 in the first embodiment.

  As shown in FIG. 5, the magnetoresistive element 5 </ b> B includes a lower electrode 2 </ b> B formed by laminating a Ta film 22 and a Ru film 23 on a CuCr alloy layer 21, but the lower electrode 2 including only the CuCr alloy layer 21 (FIG. 5). 1) and a lower electrode 2A, 2C (see FIGS. 3B and 4) in which a CuCr alloy layer 21 is laminated on the Cu layer 24 may be provided. Further, regarding the electrode connected under the TMR element structure 1B, the portion including the CuCr alloy layer 21, that is, the lower electrode 2B (2, 2A, 2C) is only in the region where the TMR element structure 1B is formed. In other words, the contact portion (drain connection portion 43) connected to the drain 7d may be formed of a metal electrode material such as Cu. In addition, it is preferable that the drain connection portion 43 is provided so as to avoid a region immediately below the TMR element structure 1B (planar view region) so that a region serving as a base surface of the TMR element structure 1B in the lower electrode 2B is not roughened. The lower electrode 2B is formed so as to be extended so that the TMR element structure 1B is provided outside the region connected to the drain connection portion 43.

  In the magnetoresistive effect element 5B according to the present embodiment, the upper electrode 3A does not need to transmit light, and thus is formed of a metal electrode material such as Cu.

  As the substrate 7A, since a MOSFET is formed on the surface layer, a p-type silicon (Si) substrate is used. The MOSFET is formed by a known method. Further, the source line 41, the word line 42, and the drain connection portion 43 connected to the source 7s, gate 7g, and drain 7d of the MOSFET, respectively, are formed of a metal electrode material such as Cu similarly to the upper electrode 3A.

(Operation of magnetoresistive element)
As the memory cell write, the magnetization reversal of the TMR element structure 1B in the magnetoresistive effect element 5B is performed. The magnetization reversal operation of the TMR element structure 1B is different from that of the TMR element structure 1 shown in FIGS. 2A and 2B in the direction of current supplied from the upper and lower electrodes 3A (3) and 2B (2) and the magnetization free layer. This is the same except that the relationship with the magnetization direction of 13B is reversed. On the other hand, as shown in FIGS. 2C and 2D, the memory cell is read by the voltage between the electrodes 2 and 3 when the TMR element structure 1B (1) supplies a predetermined current I _TST that does not reverse the magnetization. Thus, the resistances R _P and R _AP when the magnetization direction of the magnetization free layer 13B of the TMR element structure 1B is parallel or anti-parallel to the magnetization fixed layer 11B are detected. In the magnetoresistive effect element 5B, the lower electrode 2B is connected to the source line 41 extending perpendicularly to the upper electrode (bit line) 3A from the drain connecting portion 43 via the MOSFET, and this connection is connected to the word line. It is turned ON / OFF by supplying current from the line 42. Accordingly, the write and read currents I _W and I _TST are supplied to the TMR element structure 1B using the upper electrode (bit line) 3A and the source line 41 as a pair of electrodes.

  The magnetoresistive effect element 5B may include the TMR element structures 1 and 1A in which a magnetization fixed layer is stacked under the barrier layer, similarly to the spin-injection magnetization switching elements 5 and 5A according to the first and second embodiments. . The magnetoresistive element 5B may be a memory cell by connecting a diode instead of the MOSFET (not shown). The diode can also be formed on the surface layer of the Si substrate, like the MOSFET.

As described above, according to the magnetoresistive effect element according to the third embodiment, since the reversal current is low as in the first and second embodiments, the current for writing is small, and the MR ratio (R _AP Since the TMR element structure having a high −R _P ) / R _P is provided, it is possible to realize a large-capacity MRAM that can be read easily even when miniaturized and saves power.

  The spin-injection magnetization reversal element (light modulation element) according to the first and second embodiments may be connected to the MOSFET with the lower electrode as in the magnetoresistive effect element according to the third embodiment (see FIG. 5). ). By using such a light modulation element with a MOSFET as a spatial light modulator provided in a pixel, it is possible to detect an error in magnetization reversal of the light modulation element for each pixel. In the light modulation element according to the present invention, a metal material, not a transparent electrode material such as IZO, can be applied to the lower electrode, and light does not have to enter and exit from the substrate side (below). A substrate can be applied.

[Fourth Embodiment]
The spin transfer magnetization switching element according to the fourth embodiment of the present invention is a magnetoresistive effect element as in the third embodiment, and includes two TMR element structures stacked. The spin-injection magnetization switching element according to the fourth embodiment will be described below. The same elements as those in the first to third embodiments (see FIGS. 1 to 5) are denoted by the same reference numerals and description thereof is omitted. In addition, since the spin-injection magnetization reversal element has two TMR element structures, there are elements in which “first” and “second” are added to the names of the elements. Are the same elements.

  As shown in FIG. 6A, a magnetoresistive effect element (spin injection magnetization reversal element) 5C according to the fourth embodiment of the present invention includes a lower electrode (electrode) 2B, a first magnetization fixed layer (magnetization fixed layer). 11A, barrier layer 121, magnetization free layer 13B, barrier layer 122, second magnetization fixed layer (magnetization fixed layer) 11B, protective film 16, and upper electrode 3A are stacked in this order. The barrier layer 121 and the barrier layer 122 are the same elements as the barrier layer 12 in the first embodiment and the like made of MgO exhibiting (001) plane orientation, and are given different signs for identification. That is, the magnetoresistive element 5C includes a first TMR element structure (tunnel magnetoresistive element structure) 1C formed by stacking the first magnetization fixed layer 11A, the barrier layer 121, and the magnetization free layer 13B, the magnetization free layer 13B, and the barrier layer 122. In addition, two TMR element structures that are vertically symmetrical to each other and a second TMR element structure (tunnel magnetoresistive element structure) 1B formed by laminating the second magnetization fixed layer 11B are provided in common with the magnetization free layer 13B. The magnetoresistive effect element 5C is provided with a lower electrode 2B and an upper electrode 3A connected as a pair of electrodes at both upper and lower ends of the laminated TMR element structures 1C and 1B. Therefore, the magnetoresistive effect element 5C is a so-called dual pin structure spin injection magnetization reversal element. Similarly to the magnetoresistive effect element 5B shown in FIG. 5, the magnetoresistive effect element 5C is connected to the drain 7d of the MOSFET formed on the substrate 7A by the lower electrode 2B to constitute an MRAM memory cell ( (Not shown).

  The second TMR element structure 1B, that is, the magnetization free layer 13B, the barrier layer 122, and the magnetization fixed layer 11B have the same configuration as that in the third embodiment (see FIG. 5). In order to share the magnetization free layer 13B with the second TMR element structure 1B, the first TMR element structure 1C replaces the magnetization free layer 13 with the magnetization free layer 13B in the TMR element structure 1A in the second embodiment (see FIG. 4). The rest of the configuration is the same as that of the TMR element structure 1A. In the magnetoresistive effect element 5C, by defining the material for the magnetization free layer and the lower magnetization fixed layer (first magnetization fixed layer) in this way, two TMRs using (001) -oriented MgO as barrier layers are used. Element structures 1C and 1B are provided. The magnetoresistive effect element 5C includes the magnetization fixed layer 11 of the TMR element structure 1 in the spin injection magnetization reversal element 5 (see FIG. 1) according to the first embodiment, instead of the first magnetization fixed layer 11A on the lower layer side. You may provide (refer FIG.6 (b)).

  The second magnetization fixed layer 11B is not limited to an amorphous layer because a barrier layer (MgO) is not provided on the second magnetization fixed layer 11B, similarly to the spin-injection magnetization switching element 5B (see FIG. 5) according to the third embodiment. A magnetic metal film containing a transition metal may be provided at the interface with the layer 122 (not shown). Further, the same material (Tb—Fe—Co, Gd—Fe) as the first magnetization fixed layer 11A (11) may be applied to the second magnetization fixed layer 11B, and together with the first magnetization fixed layer 11A (11). The coercive force is larger than that of the magnetization free layer 13B. At the same time, the second magnetization fixed layer 11B is preferably formed so as to have a different coercivity from the first magnetization fixed layer 11A (11). This is because the first magnetization fixed layer 11A and the second magnetization fixed layer 11B are fixed in different magnetization directions, specifically, in antiparallel magnetization directions, as will be described later in the magnetization reversal operation. This is to make it easier. Alternatively, instead of providing a difference in coercivity with the first magnetization pinned layer 11A (11), the second magnetization pinned layer 11B has a magnetic film exchange-coupled on the barrier layer 122 side (lower side). A multi-layer structure may be provided (not shown).

(Operation of magnetoresistive element)
The magnetization reversal operation of the TMR element structures 1C and 1B in the magnetoresistive element 5C will be described with reference to FIGS. 7 (a) and 7 (b). In FIG. 7, the protective film 16 is not shown. The magnetization of the first magnetization fixed layer 11A is fixed upward, and the second magnetization fixed layer 11B is fixed downward. As shown in FIG. 7A, the upper electrode 3 (3A) is set to “+” and the lower electrode 2 (2B) is set to “−”, so that the TMR element structures 1C and 1B are connected to the second magnetization fixed layer 11B side. A current is supplied to the first magnetization fixed layer 11A, and electrons are injected from the first magnetization fixed layer 11A side. Then, similarly to the spin-injection magnetization switching element 5 according to the first embodiment (see FIG. 2A), the first magnetization fixed layer 11A causes downward spin in the direction opposite to the magnetization of the first magnetization fixed layer 11A. The possessed electrons d _D are discriminated, and electrons d _U having upward spin are biased and injected into the magnetization free layer 13B. Further magnetization free layer 13B electrons d _U injected into remains in magnetization free layer 13B because the magnetization is discriminated by the second magnetization fixed layer 11B in the reverse direction, as a result, upward magnetization of the magnetization free layer 13B Invert. On the other hand, as shown in FIG. 7B, the upper electrode 3 is set to “−”, the lower electrode 2 is set to “+”, and the TMR element structures 1C and 1B are subjected to the second magnetization from the first magnetization fixed layer 11A side. When a current is supplied to the fixed layer 11B and electrons are injected from the second magnetization fixed layer 11B side, the electrons d _D having a downward spin remain in the magnetization free layer 13B, so that the magnetization of the magnetization free layer 13B is reversed downward. To do.

  As described above, the magnetoresistive effect element 5C is formed of a pair of electrodes 2 and 3 as in the case of the spin injection magnetization reversal element 5 having one TMR element structure (see FIGS. 2A and 2B). By supplying current in the direction perpendicular to the plane, the magnetization direction of the magnetization free layer 13B is reversed by 180 °, and the magnetization fixed layers 11A and 11B are provided on both upper and lower sides of the magnetization free layer 13B, thereby stabilizing the magnetization reversal operation. To do.

  In order to fix the two magnetization fixed layers 11A and 11B of the magnetoresistive effect element 5C to antiparallel magnetization, initial setting is performed as follows. For example, if the first magnetization fixed layer 11A has a larger coercive force than the second magnetization fixed layer 11B, first, a magnetic field larger than the coercivity of the first magnetization fixed layer 11A is applied to the magnetoresistive effect element 5C. Then, the magnetization fixed layers 11A and 11B (and the magnetization free layer 13B) are all magnetized upward, and then smaller than the coercivity of the first magnetization fixed layer 11A and the coercivity of the second magnetization fixed layer 11B. By applying a large magnetic field, the second magnetization fixed layer 11B (and the magnetization free layer 13B) is magnetized downward. Alternatively, when the second magnetization fixed layer 11B includes a magnetic film exchange-coupled, by performing a heat treatment at about 200 ° C. in a vacuum while applying a magnetic field exceeding the coercive force of both the magnetization fixed layers 11A and 11B. The initial setting of the magnetoresistive effect element 5C can be performed by one (one step) application of the magnetic field.

The magnetoresistive effect element 5C detects a change in resistance due to magnetization reversal, as in the TMR element structure 1 shown in FIGS. The value measured from is the sum of the resistances of the TMR element structures 1C and 1B. Here, the resistance when the magnetization direction of the magnetization free layer 13B of the first TMR element structure 1C is parallel or antiparallel to the first magnetization fixed layer 11A is R1 _P , R1 _AP (= R1 _P + ΔR1), and the second TMR element The resistance when the magnetization direction of the magnetization free layer 13B of the structure 1B is parallel or antiparallel to the second magnetization fixed layer 11B is R2 _P and R2 _AP (= R2 _P + ΔR2). Then, the resistance of the magnetoresistive effect element 5B is such that when the magnetization of the magnetization free layer 13B shown in FIG. 7C is upward, R _U = R1 _P + R2 _AP and the magnetization free layer 13B shown in FIG. When the magnetization is downward, R _D = R 1 _AP + R 2 _P , and the amount of change ΔR due to magnetization reversal is | R _U −R _D | = | ΔR 2 −ΔR 1 | It becomes a difference in quantity.

  Therefore, the magnetoresistive effect element 5C has a structure in which the first TMR element structure 1C and the second TMR element structure 1B have a difference that can be detected in the amount of change in resistance due to the magnetization reversal of the magnetization free layer 13B. It is preferable. For example, the barrier layer 121 and the barrier layer 122 may have different thicknesses.

(Modification)
Alternatively, the two TMR element structures may include barrier layers made of different materials, that is, one may include a barrier layer other than (001) -oriented MgO. As shown in FIG. 6B, the magnetoresistive effect element 5D according to the modification of the fourth embodiment includes a lower electrode (electrode) 2B, a first magnetization fixed layer 11, a barrier layer 12, a magnetization free layer 13, an intermediate layer. The layer (barrier layer) 14, the second magnetization fixed layer 11B, the protective film 16, and the upper electrode 3A are stacked in this order. That is, the magnetoresistive effect element 5D includes the TMR element structure 1 and the MR element structure 1D that shares the magnetization free layer 13 of the TMR element structure 1 in a stacked manner.

The TMR element structure 1, that is, the magnetization fixed layer 11, the barrier layer 12, and the magnetization free layer 13 have the same configuration as that of the first embodiment (see FIG. 1). Further, the TMR element structure 1 may be a TMR element structure 1A provided with a magnetization fixed layer 11A (see FIG. 6A) instead of the magnetization fixed layer 11. The intermediate layer 14 of the MR element structure 1D is formed of a known insulator as a barrier layer of a TMR element different from the barrier layer 12, and is made of Al ₂ O ₃ , HfO ₂ , or MgO that is not (001) plane oriented. Alternatively, the MR element structure 1D may be a CPP-GMR element. In this case, the intermediate layer 14 is made of a nonmagnetic metal such as Cu, Ag, Al, or Au, or a semiconductor such as ZnO, and has a thickness. It is preferable to set it as 1-10 nm. Since the CPP-GMR element generally has an MR ratio lower than that of the TMR element and the amount of change due to magnetization reversal is small, the change in resistance of the magnetoresistive effect element 5D due to magnetization reversal of the magnetization free layer 13 becomes easier to detect.

  As described above, according to the magnetoresistive effect element according to the fourth embodiment and the modification thereof, the magnetization reversal operation is stabilized by the two magnetization fixed layers, and at least one barrier layer is MgO having (001) plane orientation. Thus, as in the third embodiment, it is possible to realize a large-capacity MRAM that can be read easily even when miniaturized and saves power.

[Fifth Embodiment]
The spin-injection magnetization switching element according to the fifth embodiment of the present invention is a light modulation element and includes two TMR element structures sharing a magnetization free layer as in the fourth embodiment, but is arranged in parallel in the film surface direction. This is a spin injection magnetization reversal element having a parallel dual pin structure (see JP 2012-78579 A). The spin-injection magnetization switching element according to the fifth embodiment will be described below. The same elements as those in the first to fourth embodiments (see FIGS. 1 to 7) are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 8, in the light modulation element 5E, the first magnetization fixed layer (magnetization fixed layer) 11A and the second magnetization fixed layer (magnetization fixed layer) 11 are spaced apart from each other and arranged in the plane direction, and these magnetization fixed The barrier layer 12, the magnetization free layer 13, and the protective film 16 are stacked on the entire layers 11 and 11A and the gap between them, and a first lower electrode (electrode) is provided below the first magnetization fixed layer 11A. ) 2A1 and a second lower electrode (electrode) 2A2 connected to the second magnetization fixed layer 11, respectively. That is, the light modulation element 5E includes a first TMR element structure (tunnel magnetoresistive element structure) 1A formed by stacking a first magnetization fixed layer 11A, a barrier layer 12, and a magnetization free layer 13, a second magnetization fixed layer 11, and a barrier layer. 12, the second TMR element structure (tunnel magnetoresistive element structure) 1 formed by laminating the magnetization free layer 13 and the two TMR element structures arranged side by side are provided in common with the barrier layer 12 and the magnetization free layer 13. These are concave shapes in which the cross-sectional views of these portions are upside down. The barrier layer 12 may be separated into two and stacked on each of the magnetization fixed layers 11A and 11 (see the barrier layer 12 and the intermediate layer 14 in FIG. 9). The light modulation element 5E connects the first lower electrode 2A1 and the second lower electrode 2A2 as a pair of electrodes to the magnetization fixed layers 11 and 11A side of the TMR element structures 1A and 1, that is, to the lower side. Therefore, the light modulation element 5E is a spin-injection magnetization reversal element having a parallel dual pin structure in which a dual-pin magnetoresistive element 5C (see FIG. 6A) is deformed to form an arch-shaped current path. is there.

  The TMR element structures 1 and 1A, that is, the magnetization fixed layers 11 and 11A, the barrier layer 12, and the magnetization free layer 13 have the same configurations as those in the first and second embodiments (see FIGS. 1 and 4), respectively. In the light modulation element 5E, unlike the magnetoresistive effect element 5C, the magnetization free layer 13 is not limited to the Gd—Fe alloy (magnetization free layer 13B) because the barrier layer 12 is not formed thereon. In the light modulation element 5E, the first magnetization fixed layer 11A (TbFeCo layer 11a) is formed of Tb—Fe—Co, and the second magnetization fixed layer 11 is formed of a Gd—Fe alloy. While the barrier layer 12 formed in the above is made of (001) -oriented MgO, the magnitude of the coercive force is different. By adopting such a configuration, the light modulation element 5E has magnetizations antiparallel to each other in the first magnetization fixed layer 11A and the second magnetization fixed layer 11 similarly to the magnetoresistive effect element 5C according to the fourth embodiment. It is easy to fix in the direction (see FIGS. 7A and 7B). In FIG. 8, the magnetization fixed layers 11 </ b> A and 11 are shown at the same thickness and the same height position, but this does not stipulate that the thickness and the height position are the same. , And may be formed at different height positions. In the light modulation element 5E, when the thicknesses of the two magnetization fixed layers 11A and 11 are different from each other, a base film is provided on the lower electrodes 2A1 and 2A2, and the height positions of the upper surfaces of the magnetization fixed layers 11A and 11 are set. They should be aligned (not shown). Furthermore, the light modulation element 5E may use both of the two magnetization fixed layers as the magnetization fixed layer 11 or the magnetization fixed layer 11A. In this case, the light modulation elements 5E may be formed to have different thicknesses and different coercive forces.

The light modulation element 5E according to the present embodiment includes two lower electrodes 2A1 and 2A2 because the pair of electrodes are connected to the lower sides of the magnetization fixed layers 11 and 11A arranged in the plane direction. Does not have an upper electrode. An insulating material that transmits light such as SiO ₂ is provided on the magnetization free layer 13 (protective film 16) as necessary (not shown). The first lower electrode 2A1 and the second lower electrode 2A2 are the same elements as the lower electrode 2A composed of the Cu layer 24 and the CuCr alloy layer 21 in the modified example of the first embodiment, and have different signs to identify each other. Attached. In the light modulation element 5E, instead of the first lower electrode 2A1 and the second lower electrode 2A2 (lower electrode 2A), the Ta film 22 is formed on the lower electrode 2 (see FIG. 1) having only the CuCr alloy layer 21 or the CuCr alloy layer 21. The lower electrodes 2B and 2C (see FIG. 3) may be provided.

  Similar to the pair of electrodes 2 and 3 in the first embodiment, the first lower electrode 2A1 and the second lower electrode 2A2 are two-dimensionally arrayed by wiring extending one in the row direction and the other in the column direction. Are shared by the light modulation elements 5E arranged in the same manner. The first lower electrode 2A1 extends in a direction orthogonal to the direction in which the magnetization fixed layers 11 and 11A are arranged (the left-right direction in FIG. 8), and the first lower electrode 2A1 itself is the light modulation according to the first embodiment. Similar to the lower electrode 2 of the element 5 or the like, it is formed in a wiring shape directly connected under the first magnetization fixed layer 11. On the other hand, the second lower electrode 2A2 shared via the wiring extending in the direction orthogonal to the first lower electrode 2A1 (the left-right direction in FIG. 8) includes the first magnetization fixed layer 11A, the first lower electrode 2A1, and The wiring portion (wiring portion 41A) is below the first lower electrode 2A1 (on the side away from the TMR element structures 1A and 1) so as not to prevent the connection of the first lower electrode 2A1. Are provided with an interlayer insulating layer (insulating layer 6) interposed therebetween. The second lower electrode 2A2 is connected to the wiring portion 41A by an interlayer connection portion (contact) 43A. The interlayer connection portion 43A is preferably provided so as to avoid a region immediately below the second magnetization fixed layer 11 so that the region serving as the base surface of the second magnetization fixed layer 11 in the second lower electrode 2A2 does not become rough. The wiring portion 41A and the interlayer connection portion 43A connected to the second lower electrode 2A2 may be formed of a metal electrode material such as Cu.

(Operation of light modulator)
The magnetization reversal operation of the TMR element structures 1A and 1 in the light modulation element 5E is the same as that of the magnetoresistive effect element 5C according to the fourth embodiment (see FIGS. 7A and 7B). That is, in the light modulation element 5E, the shape of the current path (electron d _U , d _D injection path) between the pair of electrodes (first lower electrode 2A1, second lower electrode 2A2) is the film of the magnetoresistive effect element 5C. It was only arched with respect to a straight line perpendicular to the surface. In the light modulation element 5E, the injected electrons (one of d _U and d _D ) remain between the regions of the magnetization free layer 13 stacked on the magnetization fixed layers 11A and 11 respectively. It is possible to reverse the magnetization even in between.

  The spin-injection magnetization reversal element is difficult to reverse the magnetization when the area in plan view is large, but the light modulation element 5E is designed so that the TMR element structures 1A and 1 are designed to have a small area as in the magnetoresistive effect element. By increasing the area of the shared magnetization free layer 13, the effective area of the light modulation is increased while suppressing the reversal current. Similarly to the light modulation element 5 according to the first embodiment (see FIGS. 2C and 2D), the light modulation element 5E inputs and outputs light from the upper side where the magnetization free layer 13 is provided. Light modulation. The light modulation element 5E includes a pair of electrodes (first lower electrode 2A1 and second lower electrode 2A2) both provided only on the magnetization fixed layers 11A and 11 (lower side). Need not be connected directly (except for the protective film 16). Therefore, the light modulation element 5E does not require any of the pair of electrodes to transmit light, and the transparent electrode material (light modulation element 5) having higher resistance than the amorphous Cu—Cr alloy (CuCr alloy layer 21). It is not necessary to apply the upper electrode 3 (see FIG. 1).

(Modification)
Similar to the modification of the fourth embodiment, in the dual-pin structure spin transfer magnetization switching element, the two TMR element structures may include barrier layers made of different materials, that is, one of which has a (001) plane orientation. A barrier layer other than MgO may be provided. As shown in FIG. 9, the light modulation element 5F according to the modification of the fifth embodiment includes the TMR element structure 1 and the MR element structure 1D that share the magnetization free layer 13 in parallel. Accordingly, the optical modulation element 5F is a dual-pin structure spin-injection magnetization reversal element in which the dual-pin magnetoresistive element 5D (see FIG. 6B) is deformed to form an arch-shaped current path. It is a light modulation element.

  The TMR element structure 1 and the MR element structure 1D, that is, the magnetization fixed layers 11 and 11B, the barrier layer 12, the magnetization free layer 13, and the intermediate layer 14 have the same configuration as the magnetoresistive effect element 5D. Further, the fixed magnetization layer 11B may have a multilayer structure in which exchange-coupled magnetic films are stacked on the intermediate layer 14 side (upper side) instead of providing a difference in coercive force from the fixed magnetization layer 11 (not shown). ) In FIG. 9, the magnetization fixed layer 11 and the magnetization fixed layer 11B, and the barrier layer 12 and the intermediate layer 14 are shown with the same thickness and the same height position, but the thickness and the height position are the same. However, they may be formed with different thicknesses and at different height positions.

The light modulation element 5F includes a barrier layer 12 and an intermediate layer 14 made of different materials or having different thicknesses, so that the light modulation element 5F (lower electrodes 2A1, 2A2) due to magnetization reversal of the magnetization free layer 13 is provided. The change in resistance during the period can be detected (see FIGS. 7C and 7D). In particular, when the intermediate layer 14 is formed of a nonmagnetic metal or the like and the MR element structure 1D is a CPP-GMR element, a change in resistance is increased and detection becomes easier. Therefore, the light modulation element 5F according to the present modification is suitable for a pixel of a spatial light modulator that performs magnetization reversal error detection. Therefore, the light modulation element 5F is preferably connected to the MOSFET like the magnetoresistive effect element according to the third embodiment (see FIG. 5), that is, one of the lower electrodes 2A1 and 2A2 is connected to the drain of the MOSFET. To do. For example, the second lower electrode 2A2 is connected to the drain of the MOSFET at the interlayer connection portion 43A (see FIG. 8), and the wiring portion 41A (see FIG. 8) is connected to the source of the MOSFET, together with the first lower electrode 2A1, A pair of electrodes for supplying currents I _W and I _TST are used.

  In the present modification, the first lower electrode 2A1 and the second lower electrode 2A2 are the same elements as the lower electrode 2A, like the light modulation element 5E according to the fifth embodiment, and the lower electrode 2 (see FIG. 1) and the lower electrode Electrodes 2B and 2C (see FIG. 3) may be provided. The second lower electrode 2A2 may be formed of a metal electrode material such as Cu that does not have the CuCr alloy layer 21 because the barrier layer 12 made of (001) -oriented MgO is not formed thereon. Since the first lower electrode 2A1 is provided at the same height as the first lower electrode 2A1, the same laminated structure (Cu layer 24 / CuCr alloy layer 21) can be formed so that a metal material can be formed at the same time. preferable.

  As described above, the light modulation element according to the fifth embodiment and the modification thereof can suppress the inversion current and increase the area at the same time as in the first and second embodiments. The pixel of the optical modulator can have a wide effective area, and since a transparent electrode material is not required, the pixel of the spatial light modulator can be further reduced in power consumption. Furthermore, the light modulation element according to the modification of the fifth embodiment is a pixel of a spatial light modulator that can easily detect a write error.

  As mentioned above, although the form for implementing this invention has been described, the Example which confirmed the effect of this invention is demonstrated concretely compared with the comparative example which does not satisfy | fill the requirements of this invention below.

  In the spin-injection magnetization switching element according to the present invention, in order to confirm the effect of the underlying magnetic film and the lower electrode on the crystal structure of the MgO film, the materials shown in Tables 1 and 2 are formed on the thermally oxidized Si substrate. Were stacked in order from the bottom to prepare a sample, and the crystal structure was analyzed by X-ray diffraction (XRD). No. Reference numerals 1 and 2 are samples in which an MgO film simulating a barrier layer is laminated on a magnetic film simulating a magnetization fixed layer, and no upper and lower electrodes are provided. Further, all samples in Examples 1 to 3 of this specification were not subjected to molding. No. 1 is a sample of a spin injection magnetization reversal element (see FIG. 1) according to the first embodiment of the present invention. 2 is a sample of the spin-injection magnetization switching element (see FIG. 4) according to the second embodiment of the present invention. The MgO film has a thickness of about 2 nm or less as a barrier layer, but the thickness was set to 15 nm or 30 nm as shown in Table 1 in order to increase the sensitivity of the crystal structure analysis of MgO. No. FIG. 10 shows X-ray diffraction (using CuKα rays, θ-2θ scanning) patterns for the samples 1 and 2.

  No. Nos. 3, 4, and 6 are samples provided by simulating the TMR element structure (see FIG. 4) of the light modulation element according to the second embodiment of the present invention. 3 and 4 are each provided with the lower electrode (refer FIG. 1, FIG. 3 (a)) of the light modulation element which concerns on 1st Embodiment of this invention, and its modification. No. 5 is a comparative example in which the magnetization fixed layer of the spin-injection magnetization reversal element according to the second embodiment is only a TbFeCo layer in which no CoFeB layer is stacked, and the lower electrode has a small influence on the crystal structure of MgO ((MgO ( 001) Does not interfere with plane orientation. The Cu—Cr alloy of the lower electrode is Cr: 36.8 at%, and Cu and Cr are deposited by a dual ion beam sputtering apparatus equipped with a sputtering source made of Cu (purity 9N) and a sputtering source made of Cr (purity 3N). A film was formed by simultaneous sputtering. On the other hand, no. 6 and 7 are comparative examples in which the lower electrode is provided with a Cu layer formed only by a sputtering source made of Cu. Furthermore, no. 7 is a [Co / Pt] × n multilayer film, specifically, a [Pt: 1.2 nm / Co: 0.2 nm] × 10 multilayer film from the bottom. In addition, as shown in Table 2, No. “Pt / Co” of the magnetization free layer in 3 and 4 is a multilayer film of Pt: 1.5 nm / [Co: 0.3 nm / Pt: 1.0 nm] × 3 from the bottom. No. 3-7 are No.3. As in the case of Nos. 1 and 2, the MgO film simulating the barrier layer has a thickness of 50 nm or 30 nm in order to increase the sensitivity of the crystal structure analysis, and no upper electrode is provided. 5-7 are No. Similar to 1 and 2, the magnetic film (magnetization free layer) on the MgO film was omitted. No. FIG. 11 shows X-ray diffraction (using CoKα rays, θ-2θ scanning) patterns for 3 to 6 samples.

  Since the MgO (001) plane cannot be observed by the extinction rule, the diffraction angles 2θ = 42.9 ° (CuKα line) and 50.2 ° (CoKα line) at which the MgO (002) plane parallel to this plane appears are shown. The vicinity was observed. As shown in FIGS. 10 (a) and 10 (b), No. 1 in which MgO is laminated on the surface of the GdFe layer or CoFeB layer. Nos. 1 and 2 were confirmed to show (001) plane orientation, and in particular, No. 1 laminated on the GdFe layer. No. 1 formed a strong (001) -oriented MgO film.

  No. of the comparative example in which the lower electrode is formed of general Cu as an electrode material. No. 6 has a strong Cu (111) surface as shown in FIG. 2, even if an amorphous TbFeCo layer and a CoFeB layer serving as the base of the MgO film are laminated on the magnetization fixed layer, the MgO (002) plane cannot be observed or even if present, Cu (111) It was so small that it was hidden behind the peak of the surface. Furthermore, the magnetization fixed layer which is the base of the MgO film is formed of a Pt / Co multilayer film having an fcc structure. In No. 7, an MgO (111) plane was observed (not shown).

  On the other hand, No. 1 which is an embodiment of the present invention in which the lower electrode is formed of a Cu—Cr alloy. 3 is No. 3, as shown in FIG. 2 (see FIG. 10B), the MgO (002) plane could be observed. Furthermore, No. 1 was obtained by laminating a Ta film on a Cu—Cr alloy layer. 4 shows that the peak intensity on the MgO (002) plane is No. 4, as shown in FIG. Thus, an MgO film having a stronger (001) orientation could be formed. In addition, No. 3 and 4, the Cr (110) plane was also observed from the Cu-Cr alloy, but since the peak intensity is about half of the crystal structure of Cr alone, the Cu-Cr alloy has a crystal structure close to amorphous. It can be said that there is. No. The lower electrode (CuCr alloy layer) No. 3 has a surface arithmetic average roughness Ra of 0.3 nm, and the flatness is better than the arithmetic average roughness Ra 1.3 nm of the surface of the Cu layer having the same thickness of 50 nm. Met.

  On the other hand, in the comparative example No. 1 in which the MgO film is laminated on the surface of the TbFeCo layer. 11, the MgO (002) plane could be observed as shown in FIG. 11C, but the peak was small with respect to the Ta (110) plane of the Ta film as the lower electrode, and the barrier of the TMR element was As a layer, an MgO film having a (001) plane orientation sufficient to reduce the reversal current was formed.

  In order to confirm that the magnetic film (magnetization pinned layer) of Example 1 had perpendicular magnetic anisotropy, the materials shown in Table 3 were laminated in order from the bottom on the thermally oxidized Si substrate, and the TMR element was formed. A simulated sample was prepared and the magneto-optical effect was observed. No. No. 8 of Example 1 1, a sample of the spin transfer magnetization switching element (see FIG. 1) according to the first embodiment of the present invention corresponding to No. 1, 9 is No. 1 in Example 1. 4 is a sample of a spin transfer magnetization switching element (see FIG. 4) according to a second embodiment of the present invention corresponding to 2. No. 10 is No. This is a comparative example in which a CoFeB layer is laminated on the interface with the barrier layer on a magnetization free layer made of 9 GdFe. In any sample, the magnetization direction is changed by applying an external magnetic field. Therefore, the upper electrode is not provided, and a reflection film is formed from the bottom as Ta: 5 nm / [Cu: 15 nm / Ta: 3 nm]. A x2 multilayer film (shown as “Cu / Ta” in Table 3) was provided.

  About the produced sample, the Kerr rotation angle was measured by the polarization modulation method using a laser beam, and the coercive force was identified from the relationship with the applied magnetic field. Specifically, a uniform magnetic field H (> 0) is applied to the sample from the outside so that the magnetization directions of the magnetization fixed layer and the magnetization free layer become one direction. Then, a laser beam having a wavelength of 780 nm was incident at an incident angle of 30 °, and the direction of polarization (Kerr rotation angle) of the reflected light from the sample was measured with a vertical magnetic field Kerr effect measuring device. Next, while continuing to measure the polarization of the reflected light, a magnetic field H (<0) in the direction opposite to the applied magnetic field is applied while gradually increasing its magnitude (absolute value), and the change in the polarization direction is observed. did. Similarly, a change in the direction of polarization was observed by applying a magnetic field H (> 0) in the opposite direction. FIG. 12 shows the magnetic field (applied magnetic field) dependence of the Kerr rotation angle as a magnetization curve.

  12A and 12B, the magnetization fixed layer is a GdFe single layer or two layers of a TbFeCo layer and a CoFeB layer, and the magnetization free layer is a GdFe single layer. 8 and 9, since the Kerr rotation angle suddenly changed when the magnetic field reached a certain magnitude, the magnetization was reversed by the magnitude of the magnetic field when the Kerr rotation angle was changed, and the magnetization free layer was It was confirmed to have perpendicular magnetic anisotropy. In addition, No. In No. 8, the Kerr rotation angle changed in two steps. This indicates that the magnetization free layer and the magnetization fixed layer were sequentially reversed in magnetization as the magnetic field (magnetic field) increased, and the magnetization fixed layer was formed of GdFe having the same composition as the magnetization free layer. This is because the coercive force is small and the difference from the magnetization free layer is also small. On the other hand, no. No. 9, because the magnetization fixed layer includes TbFeCo having a large coercive force, the magnetization does not change in a magnetic field of 1 kOe or less in absolute value, and only the magnetization free layer made of GdFe is reversed in magnetization, and is stable as a spin injection magnetization reversal element. The operation was shown.

  These No. 8 and 9, the GdFe layer of the magnetization free layer was laminated on the CoFeB layer. No. 10 has a maximum Kerr rotation angle as shown in FIG. It was about 1/10 of 8,9, and it did not change rapidly as the magnetic field increased. This is because the magnetization direction of the magnetization free layer is nearly perpendicular (60 °) with respect to light incident at an incident angle of 30 °, and the polar Kerr effect was not obtained. Is not present.

  In order to confirm the crystal structure of the Cu—Cr alloy composition of the lower electrode, a sample was prepared by depositing a 50 nm thick Cu—Cr alloy film having a changed composition on a thermally oxidized Si substrate. The crystal structure was analyzed by X-ray diffraction (XRD) using The Cu—Cr alloy is No. 1 in Example 1. Similarly to the lower electrode 3, film formation was performed by simultaneously sputtering Cu and Cr by changing the output of the ion beam in a dual ion beam sputtering apparatus equipped with a sputtering source composed of Cu and Cr. Cr: 7.7 at%, 14.0 at%, 36.8 at%, 42.9 at%, 47.8 at%, Cu-Cr alloy films having five different compositions were subjected to X-ray diffraction (θ-2θ scanning) patterns. As shown in FIG. In addition, the pattern of Cu film | membrane (Cr: 0%) is written together with the broken line in each of Fig.13 (a)-(e).

  As shown in FIGS. 13 (a) and 13 (b), the Cu (111) surface becomes sufficiently weak at Cr: 7.7 at% and 14.0 at% (peak intensity of about 1/4 of Cu alone), and The Cr (110) plane is also weak, and as shown in FIG. 13 (c), the Cr (110) plane is observed when Cr: 36.8 at%, and further shown in FIGS. 13 (d) and 13 (e). Thus, the Cr (110) plane was strongly observed at Cr: 42.9 at% and 47.8 at%. Thus, the crystal structure of the Cu—Cr alloy depends on the composition. By forming the Cu—Cr alloy film by controlling the composition within the range of the present invention by a known film formation method, amorphous Cu is formed. The lower electrode can be formed as a -Cr alloy.

1,1A, 1B, 1C TMR element structure (tunnel magnetoresistive element structure)
11, 11A, 11B Magnetization fixed layer 11a TbFeCo layer (layer made of Tb-Fe-Co)
11b CoFeB layer (Co-Fe-B layer)
12 Barrier layer 13, 13B Magnetization free layer 2, 2A, 2B, 2C Lower electrode 21 CuCr alloy layer (amorphous Cu-Cr alloy)
22 Ta film 23 Ru film 24 Cu layer 3, 3A Upper electrode 5, 5A, 5E, 5F Light modulation element (spin injection magnetization reversal element)
5B, 5C, 5D Magnetoresistive effect element (spin injection magnetization reversal element)

Claims (5)

A tunnel magnetoresistive element structure in which a magnetization fixed layer having perpendicular magnetic anisotropy, a barrier layer made of MgO, and a magnetization free layer having perpendicular magnetic anisotropy are stacked, and connected under this tunnel magnetoresistive element structure A spin injection magnetization reversal element comprising:
The electrode is made of an amorphous Cu—Cr alloy having a composition of Cu _1-x Cr _x (0.07 <x <0.42),
The magnetization fixed layer includes a layer made of Tb-Fe-Co and a layer made of Co-Fe-B,
The spin injection magnetization reversal element, wherein the barrier layer is laminated on a layer made of Co—Fe—B of the magnetization fixed layer. A tunnel magnetoresistive element structure in which a magnetization fixed layer having perpendicular magnetic anisotropy, a barrier layer made of MgO, and a magnetization free layer having perpendicular magnetic anisotropy are stacked, and connected under this tunnel magnetoresistive element structure A spin injection magnetization reversal element comprising:
The electrode is made of an amorphous Cu—Cr alloy having a composition of Cu _1-x Cr _x (0.07 <x <0.42),
The magnetization fixed layer includes a layer made of Gd-Fe,
The spin injection magnetization reversal element, wherein the barrier layer is laminated on a layer made of Gd—Fe of the magnetization fixed layer. A tunnel magnetoresistive element structure in which a magnetization free layer having perpendicular magnetic anisotropy, a barrier layer made of MgO, and a magnetization fixed layer having perpendicular magnetic anisotropy are stacked, and connected under this tunnel magnetoresistive element structure A spin injection magnetization reversal element comprising:
The electrode is made of an amorphous Cu—Cr alloy having a composition of Cu _1-x Cr _x (0.07 <x <0.42),
The magnetization free layer includes a layer made of Gd-Fe,
The spin injection magnetization reversal element, wherein the barrier layer is laminated on a layer made of Gd—Fe of the magnetization free layer.   The spin injection magnetization reversal element according to any one of claims 1 to 3, wherein a Ta film is stacked on the electrode.   The spin injection magnetization reversal element according to any one of claims 1 to 4, wherein the spin injection magnetization reversal element is a light modulation element that emits light by changing a direction of polarization of incident light.

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