JP2017220533A - Magneto resistance effect element, magnetic memory and random access memory using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tunnel magneto resistance effect element (MTJ) capable of reducing the deterioration of thermal stability accompanying the microfabrication of an element being one of technical problems of MRAM accompanying high integration.SOLUTION: A tunnel magneto resistance effect element comprises: a recording layer 15 consisting of a ferromagnetic thin film arranged to contact one side surface of a barrier layer 14 and having perpendicular magnetic anisotropy; a fixing layer 13 arranged to contact the other side surface of the barrier layer 14, having perpendicular magnetic anisotropy and consisting of a ferromagnetic thin film having the direction of magnetization fixed in one direction; a first intermediate layer 16 contacting the surface of the recording layer 15 on the side opposite to the barrier layer 14; a second intermediate layer 12 contacting the surface of the fixing layer 13 on the side opposite to the barrier layer 14; a first magnetic layer 17 contacting the surface of the first intermediate layer 16 on the side opposite to the recording layer 15; and a second magnetic layer 11 contacting the surface of the second intermediate layer 12 on the side opposite to the fixing layer 13. At least one of the recording layer 15, the fixing layer 13, the first magnetic layer 17 and the second magnetic layers 11 is a Nd-Fe-B layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetoresistive effect element using a perpendicular magnetization material, a magnetic memory using the same, and a random access memory.

  With the spread of information communication equipment in recent years, higher integration of memory has been demanded. In particular, high integration of nonvolatile memories such as MRAM (Magnetic Random Access Memory) is becoming more and more important. The MRAM uses an MTJ (Magnetic Tunneling Junction) element that uses a tunneling magnetoresistive (TMR) effect as an element element.

  The technical problems of MRAM accompanying high integration are low power consumption, improvement of thermal stability, and improvement of S / N ratio. Low power consumption can be solved by improving the magnetic characteristics of the recording layer. Further, improvement of thermal stability can be solved by using a magnetic material having a high magnetic anisotropy constant. Improvement of the S / N ratio can be solved by increasing the TMR effect.

  For example, Patent Document 1 discloses a single metal having a melting point of 1600 ° C. or more outside a CoFeB layer / MgO barrier layer / CoFeB layer as a magnetoresistive effect element using a perpendicular magnetization material and having a high TMR ratio (resistance change rate). Or an element in which an intermediate layer made of an alloy containing the metal is inserted is disclosed. In order to manufacture the device, the crystallization of the CoFeB layer proceeds from the MgO (001) crystal side, and the CoFeB layer is moved to bcc. Although annealing after thin film formation is indispensable for crystal orientation at (001), it is disclosed that by providing such an intermediate layer, a perpendicular magnetization MTJ element exhibiting a high TMR ratio can be realized even after annealing. .

  For example, in Patent Document 2, in a vertical MTJ element, the thermal stability index (E / kBT) of the recording layer and the fixed layer is maintained while maintaining a high TMR ratio and a low writing current and suppressing an increase in resistance of the entire element. ) Or by increasing the perpendicular magnetic anisotropy of the fixed layer with respect to the recording layer, the recording layer made of the ferromagnetic material CoFeB is used in the perpendicular MTJ element using CoFeB. In at least one of the fixed layers, a conductive oxide layer is disposed on the side opposite to the tunnel barrier layer.

JP 2011-155073 A Japanese Patent No. 5816867

  The present invention also provides an MTJ element in which a decrease in thermal stability due to element miniaturization, which is one of the technical problems of MRAM accompanying high integration, a magnetic memory and a random access memory using the MTJ element. Is to provide.

  As a result of intensive studies, the present inventors have found that an MTJ element having a thin film formed using a material having a high magnetic anisotropy constant and a high coercive force has a thermal stability index (E / kT) of the recording layer and the fixed layer. It has been found that the MTJ element can be adapted to ultra-high integration because of the increase in the perpendicular magnetic anisotropy of the fixed layer with respect to the recording layer. Further, in the manufacture of a thin film using a material having a high magnetic anisotropy constant and a high coercive force, by irradiating an alternating electromagnetic field (including an alternating electric field and an alternating magnetic field), an MTJ multilayer film structure including the thin film is formed as a barrier layer. It has been found that an MTJ multilayer film structure in which the recording layer and the fixed layer are uniformly aligned in the c-axis direction perpendicular to the interface between the two can be obtained. The present invention is based on such new findings. Accordingly, the present invention provides the following items.

Item 1. A recording layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy arranged in contact with one side of the barrier layer and a magnetic layer having perpendicular magnetic anisotropy arranged in contact with the other side of the barrier layer A fixed layer made of a ferromagnetic thin film in which the direction of is fixed in one direction,
A first intermediate layer in contact with the side opposite to the barrier layer of the recording layer;
A barrier layer of the fixed layer and a second intermediate layer in contact with the opposite side surface,
A first magnetic layer in contact with the side opposite to the recording layer of the first intermediate layer and a second magnetic layer in contact with the side opposite to the fixed layer of the second intermediate layer;
At least one of the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer is an Nd—Fe—B layer.

  Item 2. Crystal having orientation obtained by performing alternating electromagnetic field irradiation treatment at the same time and / or after at least one step selected from the steps of forming the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer Item 2. The tunnel magnetoresistive element according to Item 1, wherein a layer including a tissue is disposed.

  Item 3. Item 3. The tunnel magnetoresistive element according to Item 2, wherein the alternating electromagnetic field irradiation treatment is performed at a thin film temperature of 1500 ° C or lower.

  Item 4. Item 4. The tunnel magnetoresistive element according to Item 2 or 3, wherein the frequency of the alternating electromagnetic field in the alternating electromagnetic field irradiation treatment is 300 MHz to 1 THz.

  Item 5. Item 5. The tunnel magnetoresistive element according to any one of Items 2 to 4, wherein an output of the alternating electromagnetic field in the alternating electromagnetic field irradiation treatment is 1 mW to 1 MW.

  Item 6. Item 6. The thin film according to any one of Items 2 to 5, wherein the alternating electromagnetic field irradiation in the alternating electromagnetic field irradiation treatment is pulse irradiation or continuous irradiation.

  Item 7. Item 7. The tunnel magnetoresistive element according to any one of Items 2 to 6, wherein the step of forming each layer is performed under pressure, in the air, or under reduced pressure.

Item 8. A tunnel magnetoresistive element having a recording layer and a fixed layer;
An electrode for passing a current through the tunnel magnetoresistive element;
A switching element that controls on / off of a current flowing through the tunnel magnetoresistive element,
In a magnetic memory cell in which the magnetization of the recording layer can be reversed by spin transfer torque,
The tunnel magnetoresistive element is
A recording layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy disposed in contact with one side of the barrier layer;
A fixed layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy and having a magnetization direction fixed in one direction, disposed in contact with the other side surface of the barrier layer;
A first intermediate layer in contact with the side opposite to the barrier layer of the recording layer;
A barrier layer of the fixed layer and a second intermediate layer in contact with the opposite side surface,
A first magnetic layer in contact with the side opposite to the recording layer of the first intermediate layer and a second magnetic layer in contact with the side opposite to the fixed layer of the second intermediate layer;
A magnetic memory cell, wherein at least one of the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer is an Nd—Fe—B layer.

Item 9. A plurality of magnetic memory cells;
Means for selecting a desired magnetic memory cell from the plurality of magnetic memory cells;
In a random access memory comprising means for reading or writing information to the selected magnetic memory cell,
The magnetic memory cell controls on / off of a tunnel magnetoresistive effect element having a recording layer and a fixed layer, an electrode for passing a current through the tunnel magnetoresistive effect element, and a current flowing through the tunnel magnetoresistive effect element A switching element,
The tunnel magnetoresistive element is
A recording layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy arranged in contact with one side of the barrier layer and a magnetic layer having perpendicular magnetic anisotropy arranged in contact with the other side of the barrier layer A fixed layer made of a ferromagnetic thin film in which the direction of is fixed in one direction,
A first intermediate layer in contact with the side opposite to the barrier layer of the recording layer;
A barrier layer of the fixed layer and a second intermediate layer in contact with the opposite side surface,
A first magnetic layer in contact with the side opposite to the recording layer of the first intermediate layer and a second magnetic layer in contact with the side opposite to the fixed layer of the second intermediate layer;
At least one of the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer is an Nd—Fe—B layer,
The random access memory characterized in that the means for writing information to the selected magnetic memory cell reverses the magnetization of the recording layer of the magnetic memory cell by a spin transfer torque.

  The magnetoresistive element of the present invention, the magnetic memory using the magnetoresistive effect element, and the random access memory have a higher thermal stability index (E / kT) of the recording layer and the fixed layer, or the perpendicular magnetic difference of the fixed layer with respect to the recording layer. Since the directivity increases, it becomes possible to cope with ultra-high integration.

It is a figure explaining the example of embodiment of this invention (Example 1). It is a figure explaining the example of another embodiment of the present invention (example 2). It is a figure explaining the example of another embodiment of this invention (Example 3).

An embodiment of the present invention will be described with reference to FIG. In the magnetoresistive effect element, a barrier layer 14 is disposed, a recording layer 15 made of a ferromagnetic thin film having perpendicular magnetic anisotropy is disposed in contact with one side surface of the barrier layer 14, and is disposed on the other side surface of the barrier layer. Is provided with a fixed layer 13 made of a ferromagnetic thin film having perpendicular magnetic anisotropy and having a magnetization direction fixed in one direction. A first intermediate layer 16 is disposed in contact with the side surface opposite to the barrier layer of the recording layer 15, and a second intermediate layer 12 is disposed in contact with the side surface opposite to the barrier layer of the fixed layer 13. Further, the first magnetic layer 17 is disposed in contact with the side surface opposite to the recording layer of the first intermediate layer 16, and the second magnetic layer 11 is disposed in contact with the side surface opposite to the fixed layer of the second intermediate layer 12. Yes.
A lower electrode 10 is provided on the substrate, and the multilayer structure is laminated thereon. An upper electrode 19 is disposed above the multilayer structure via a cap layer 18. Although not shown in the drawing, the lower electrode and the upper electrode are connected to wiring for passing a current through the MTJ having the multilayer structure.

  Here, the recording layer, the fixed layer, and the second magnetic layer are Nd—Fe—B layers. At least one of the recording layer, the fixed layer, and the second magnetic layer includes a crystalline structure having a novel crystal structure and orientation by performing an alternating electromagnetic field irradiation treatment simultaneously with and / or after the forming step. It is a layer.

  These Nd—Fe—B layers have Nd 2 Fe 14 B as a main phase, and may contain Dy, Pr, Cu, Al, Ga, O, C, N, and the like as additive elements, and after crystallization, Fcc—NdOx. Phase, Nd30Fe66B3Cu phase, Nd—Cu alloy phase, Nd—Fe—Cuu alloy phase, and the like.

  The material of each layer is illustrated. MgO (film thickness: 1 nm) can be used for the barrier layer 14. An Nd—Fe—B layer (film thickness: 1 nm) can be used for the recording layer 15 made of a ferromagnetic thin film having perpendicular magnetic anisotropy arranged in contact with one side surface. Further, the Nd—Fe—B layer is disposed on the fixed layer 13 made of a ferromagnetic thin film that is disposed in contact with the other side surface of the barrier layer 14 and has perpendicular magnetic anisotropy and the magnetization direction is fixed in one direction. (Film thickness: 1 nm) can be used. Ta (film thickness: 0.5 nm) is used for the first intermediate layer 16 in contact with the side surface opposite to the barrier layer of the recording layer 15 and the second intermediate layer 12 in contact with the side surface opposite to the barrier layer of the fixed layer 13. be able to. Two layers of CoFe (film thickness: 0.2 nm) and Pd (film thickness: 1.2 nm) were laminated three times on the first magnetic layer 17 in contact with the opposite side of the recording layer of the first intermediate layer 16. A multilayer film (film thickness: 4.2 nm) can be used. An Nd—Fe—B layer (film thickness: 1 nm) can be used for the second magnetic layer 11 in contact with the side surface opposite to the fixed layer of the second intermediate layer 12. A Ta layer can be used as the lower electrode 10. An underlayer may be provided between the second magnetic layer 11 and the lower electrode 10, and Ru can be used as the underlayer. The cap layer 18 is a Ta layer, and an upper electrode 19 having a laminated structure of Cr / Au can be used. Although it does not specifically limit as a raw material of a board | substrate, For example, a silica, a silicon | silicone, glass etc. are mentioned.

  In this embodiment, the second magnetic layer is a layer including a crystal structure having a novel crystal structure and orientation, and Nd2Fe14B has a c-axis perpendicular to the barrier layer MgO and the second intermediate layer Ta surface. Fully oriented in the direction. As a result, the magnetization of the fixed layer made of a ferromagnetic material adjacent to the second magnetic layer via the intermediate layer is pinned. In addition, since the magnetization fluctuation of the fixed layer when a current is passed can be tightly sealed, the element operates stably. In such an embodiment, the thermal stability index (E / kT) of the recording layer and the fixed layer is increased, or the perpendicular magnetic anisotropy of the fixed layer with respect to the recording layer is increased. It will be something. A magnetic memory and a random access memory using this element can cope with ultra-high integration.

  By using magnesium oxide (MgO) as a barrier layer and arranging Nd2Fe14B on both sides thereof, the resistance change rate (TMR ratio) can be improved in the perpendicular magnetization MTJ element.

  Since the intermediate layer is disposed, the heat resistance of the TMR ratio is improved. For example, when Co—Fe—B of the recording layer and the fixed layer is heat-treated, diffusion of boron (B) occurs. At this time, if an appropriate intermediate layer is adjacent to each layer, the diffusion of B is suppressed, and each layer is crystallized from the interface of the MgO (001) crystal and oriented to bcc (001). On the other hand, when there is no intermediate layer (directly adjacent to the second magnetic layer), or when the intermediate layer is a material that hardly suppresses B diffusion (Pd, Cu, Al, etc.) Since B is released by diffusion, it is crystallized as an alloy from which B is released at a low annealing temperature. At that time, the crystallization of each layer proceeds from the side opposite to MgO (intermediate layer side or magnetic layer side adjacent to each layer) and is different from bcc (001) by being affected by the crystal structure of the intermediate layer or magnetic layer. (Fcc structure) or crystallize with a different crystal orientation (bcc (110)). Therefore, the insertion of a nonmagnetic material that suppresses the diffusion of B is effective for obtaining the bcc (001) crystal of each layer.

  Ta used in the intermediate layer in this example has a higher melting point (1600 ° C. or higher) than each element of Co—Fe—B and Nd—Fe—B. In this case, an effect of allowing the crystallization of each layer as described above to proceed from the MgO side can be obtained. Ta is mentioned as the first intermediate layer and the second intermediate layer. In addition, W, Ru, Pt, Ti, Os, V, Cr, Nb, which is a material having a melting point of 1600 ° C. or more. Similar effects can be obtained by using Mo, Rh, Hf, Re, or the like. The intermediate layer may be made of an amorphous ferromagnetic material and has a higher crystallization temperature than each layer. As the material of the intermediate layer, any one of FeTaN, FeTaC, FeZrB, FeHfB, FeTaB, CoZrNb, CoFeBNb, CoFeZr, CoFeZrNb, CoFeZrTa, and CoTaZr may be used. The intermediate layer may include an alloy containing Si and B, and containing either Fe or Co and Nb, Zr, Hf, or Ta. Moreover, you may use the combination of a different material for a 1st intermediate | middle layer and a 2nd intermediate | middle layer.

Although a laminated film of CoFe and Pd has been described as the perpendicular magnetization material of the first magnetic layer, the same effect can be obtained by applying other perpendicular magnetization materials. As specific materials, for example, an L10 type ordered alloy such as Co50Pt50, Fe50Pt50, Fe30Ni20Pt50, m-D019 type Co75Pt25 ordered alloy, or a granular magnetic material such as CoCrPt-SiO2, FePt-SiO2 is used as a non-magnetic matrix. A laminated film in which a granular structure material dispersed in a phase or an alloy containing one or more of Fe, Co, Ni and nonmagnetic metals such as Ru, Pt, Rh, Pd, Cr are alternately laminated. Alternatively, an amorphous alloy including a transition metal in a rare earth metal such as Gd, Dy, or Tb, such as TbFeCo or GdFeCo, may be used. Also, using Co, for example, a CoCr alloy or a CoCrPt alloy containing one or more elements of Cr, Ta, Nb, V, W, Hf, Ti, Zr, Pt, Pd, Fe, and Ni. Also good.
As the cap layer, Ta mentioned is preferable from the viewpoint of reaction and diffusion with the magnetic layer by annealing treatment. However, other materials such as Ru, Pt, Cr, Ti, and W may be used.

  One of the features of this embodiment is that an alternating electromagnetic field is applied during and / or after the production of the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer, so that at least one layer becomes It is a layer including a crystal structure having a novel crystal structure and orientation. By applying an alternating electromagnetic field, for example, the crystal growth direction of a highly magnetic anisotropic material, which is a thin film material constituting the layer, can be changed to control the orientation of the thin film. In addition, since a material having a high magnetic anisotropy constant absorbs alternating electromagnetic fields well, in the embodiment for manufacturing a thin film consisting of two or more layers, along with the above change, by selective heating that gives energy only to the magnetic recording layer, A crystal structure having a novel crystal structure and orientation can be obtained. For example, by alternating electromagnetic field irradiation, the c-axis of the tetragonal Nd2Fe14B crystal can be highly oriented in the perpendicular direction while keeping the thin film interface clean.

The present invention relates to a magnetoresistive effect element having an MTJ multilayer structure in which any one of a recording layer, a fixed layer, a first magnetic layer, and a second magnetic layer is a perpendicular magnetization layer, and the perpendicular magnetization layer comprises: The main component is a ferromagnetic material with Ku of 10 ⁶ to 10 ⁹ erg cm ⁻³ .

In the present invention, the ferromagnetic material serving as the main component of the highly magnetic anisotropic particles is not particularly limited as long as it has a high magnetic anisotropy, and the magnetic anisotropy constant (Ku) is 10 ^6. -10 ⁹ erg cm ^-3 , preferably 5 x 10 ⁶ to 10 ⁹ erg cm ^-3 , more preferably 10 ⁷ to 8 x 10 ⁸ erg cm ^-3 Can do.

The method for producing a thin film according to the present invention is not particularly limited. For example, a step of forming a thin film using a material containing a ferromagnetic material having a Ku of 10 ⁶ to 10 ⁹ erg cm ⁻³ , and simultaneously with the thin film formation step And / or after that, it can obtain by the method etc. which include the process of performing an alternating electromagnetic field irradiation to the said thin film. Accordingly, the present invention also provides a method for producing such a thin film.

Thin Film Forming Process The recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer are manufactured by a thin film forming process using respective raw materials. The thin film forming step according to the present invention includes a step of forming a perpendicular magnetization thin film having oriented nano-columnar particles using a material having a high magnetic anisotropy constant.

  The method for forming a thin film according to the present invention is not particularly limited, and sputtering, chemical vapor deposition (CVD), vapor deposition, ion plating, ion beam vapor deposition, dip coating, spin coating, spray coating, plating and other methods. The method can be selected as appropriate. The substrate used for forming these thin films is not particularly limited. For example, sapphire, silicon, quartz, metal oxides (MgO, etc.), metal nitrides (GaN, AlN, etc.), metal carbides (SiC, etc.) are representative. Inorganic materials and organic materials represented by polycarbonate and the like. The thin film may be formed not only by a method for forming a thin film on a substrate but also by laser ablation in a medium such as water. In addition, the thin film formation step may be performed in the air, under reduced pressure, or under pressure, and can be appropriately set according to the method for forming the coating film, the raw material, and the like. The temperature of the film forming process is not particularly limited, and can be set as appropriate within a range from room temperature (for example, 25 ° C.) to 1500 ° C.

  The film thickness of the thin film obtained by the production method according to the present invention is not particularly limited, and can be set as appropriate within a range of, for example, 0.1 nm or more, 1 nm or more, 5 nm or more, 10 nm or more, 50 nm or more, 100 nm or more. Further, the upper limit of the thickness of the thin film is not particularly limited, and can be appropriately set within a range of 1 μm or less, 500 nm or less, 200 nm or less, 100 nm or less, 50 nm or less, and the like.

  In the manufacturing method according to the present invention, the film thickness of the thin film may preferably be in the range of 0.1 nm to 1 μm, more preferably in the range of 0.2 nm to 500 μm, and preferably 0. It may be in the range of 2 nm to 200 nm.

Alternating electromagnetic field irradiation step The manufacturing method according to the present invention comprises an alternating electromagnetic field irradiation at the same time and / or after at least one step selected from the steps of forming a recording layer, a fixed layer, a first magnetic layer, and a second magnetic layer. Including an irradiation step of performing the treatment. In addition, when irradiating during shaping | molding of a film | membrane, the irradiation object becomes a thin film and / or its raw material. Unlike other heat treatments, the energy of alternating electromagnetic field irradiation interacts with the substance to cause a change in the substance and can affect the selected substance. These changes are complex for each target substance and have not been fully elucidated. The tunnel magnetoresistive element of the present invention is subjected to an alternating electromagnetic field irradiation treatment simultaneously with and / or after at least one step selected from the steps of forming a recording layer, a fixed layer, a first magnetic layer, and a second magnetic layer. It can be said that it is a tunnel magnetoresistive effect element in which a layer including a crystal structure having orientation obtained by application is disposed.

  The crystal structure having a novel crystal structure and orientation obtained by the alternating electromagnetic field irradiation is, for example, a highly oriented nanocolumnar particle in the form of a thin film made of a material having high magnetic anisotropy. Therefore, by performing this irradiation treatment, at least one layer selected from the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer has a novel crystal structure, a layer having a crystal structure with orientation, For example, it is a layer having good c-axis orientation in the direction perpendicular to the barrier layer surface.

  The alternating electromagnetic field that is irradiated during film forming, the thin film after forming, or a combination thereof is not particularly limited as long as it is a method that can apply an alternating electromagnetic field, for example, microwave, submillimeter wave, etc. Can be mentioned. Further, the alternating electromagnetic field irradiation step may be performed after the thin film formation, simultaneously with the thin film formation (including performing the alternating electromagnetic field irradiation as part of the thin film formation step), or both.

  The frequency of the alternating electromagnetic field is not particularly limited, and can be appropriately set in a range of 300 MHz or more, 0.5 GHz Hz or more, 1 GHz or more, 2 GHz or more, for example. Further, the upper limit of the frequency of the alternating electromagnetic field is not particularly limited, and can be appropriately set in a range of 1 THz or less, 300 GHz or less, 30 GHz or less, 6 GHz or less, 3 GHz or less, for example. In the present embodiment, the frequency condition of the alternating electromagnetic field irradiation step may preferably be in the range of 300 MHz to 300 GHz, more preferably in the range of 900 MHz to 300 GHz, and desirably in the range of 900 MHz to 30 GHz. There may be.

  The output of the alternating electromagnetic field irradiation is not particularly limited, and can be appropriately set within a range of, for example, 1 mW or more, 1 W or more, 1 kW or more, 5 kW or more. Moreover, the upper limit of the output of an alternating electromagnetic field is not specifically limited, For example, it can set suitably in ranges, such as 1 MW or less, 100 kW or less, 10 kW or less, 1 MW or less. In the present embodiment, the output condition of the alternating electromagnetic field irradiation step may preferably be in the range of 1 mW to 500 kW, more preferably in the range of 1 mW to 10 kW, and desirably in the range of 1 mW to 5 kW. There may be.

  The irradiation time is not particularly limited, and can be set as appropriate within a range of, for example, 1 second or more, 1 minute or more, 5 minutes or more. Moreover, the upper limit of irradiation time is not specifically limited, For example, it can set suitably in the range of 1 day or less, 1 hour or less, 30 minutes or less, 15 minutes or less, etc. In the present embodiment, the irradiation time condition of the alternating electromagnetic field irradiation step may preferably be in the range of 1 second to 18 hours, more preferably in the range of 1 second to 10 hours, desirably 1 It may be in the range of seconds to 3 hours.

  Further, the alternating electromagnetic field irradiation may be performed in a single mode or a multi mode. Further, the irradiation of the alternating electromagnetic field may be a so-called pulsed irradiation in which the alternating electromagnetic field irradiation is performed for a predetermined time and then the alternating electromagnetic field irradiation is stopped for a predetermined time, or the alternating electromagnetic field irradiation is continuously performed. May be performed. Although the temperature conditions of an alternating electromagnetic field irradiation process are not specifically limited, For example, it can set suitably in normal temperature (for example, 25 degreeC)-1500 degreeC (for example, normal temperature-1500 degreeC, normal temperature-800 degreeC etc.). At this time, if the substrate does not absorb energy by alternating electromagnetic field irradiation (inactive substrate of alternating electromagnetic field), the effect of alternating electromagnetic field irradiation can be exerted only on the thin film. For example, sapphire, silicon, quartz, MgO, and the like have weak ability to absorb the energy of alternating electromagnetic field irradiation, and may be called inert substrates.

  From this point of view, it is preferable to appropriately set the temperature conditions of the alternating electromagnetic field irradiation step from 900 ° C. or lower, 800 ° C. or lower, 700 ° C. or lower, 600 ° C. or lower, 500 ° C. or lower, or the like. At that time, the lower limit of the temperature condition is not particularly limited, but it is preferable to set appropriately from conditions such as normal temperature or higher, 30 ° C. or higher, 50 ° C. or higher, 100 ° C. or higher, 150 ° C. or higher, 200 ° C. or higher. In the present invention, the “temperature condition of the alternating electromagnetic field irradiation process” means the temperature of the thin film itself during the irradiation process, not the environmental temperature in the apparatus that performs the alternating electromagnetic field irradiation process. Therefore, the temperature condition of the alternating electromagnetic field irradiation step being 700 ° C. or lower means that the temperature of the thin film itself during the irradiation step is 700 ° C. or lower.

  The alternating electromagnetic field to be irradiated may be subjected to frequency modulation, phase modulation, output modulation, or modulation combining them as necessary.

Novel crystal structure, crystal structure having orientation Further , the present invention also provides a novel crystal structure, crystal structure having orientation, for example, a thin film having predetermined highly oriented nanocolumnar particles. Such a thin film can be produced by the thin film production method described above.

  Examples of the physical and chemical properties imparted to the thin film material in the present invention include the following. As a material having a high magnetic anisotropy constant as a raw material, the step of forming a thin film using a metal having a high magnetic anisotropy constant such as FePt, Nd2Fe14B, and the same as and / or after the thin film formation step, By the method of manufacturing a thin film material including a step of subjecting the material to alternating electromagnetic field irradiation, a perpendicularly crystallized thin film including a novel crystal structure, an oriented crystal structure, for example, a highly oriented nano-columnar particle is obtained as a physical and chemical property. Provided.

  As the metal having a high magnetic anisotropy constant, a ferromagnetic material, a ferrimagnetic material, and the like can be used. As the ferromagnetic material or the ferrimagnetic material, for example, a ferromagnetic metal (for example, a platinum-containing metal (cobalt) Examples thereof include platinum-containing metals (CoPt, CoCrPt, etc.), iron platinum-containing metals (FePt, etc.), and ferromagnetic intermetallic compounds (Nd2Fe14B, etc.).

  By alternating electromagnetic field irradiation, electromagnetic waves are preferentially absorbed and heated by the grains of the ferromagnetic or ferrimagnetic substance among the ferromagnetic or ferrimagnetic substance and the paramagnetic or antiferromagnetic substance. As a result, since the crystal growth direction of the ferromagnetic or ferrimagnetic material changes depending on the electromagnetic reaction field, it is considered that each grain of the ferromagnetic or ferrimagnetic material grows while maintaining a high orientation.

Embodiments of Preferred Magnetic Memory and Random Access Memory of the Present Invention An example of an embodiment of a magnetic memory and a random access memory to which the MTJ element of the present invention is applied will be described. The magnetic memory cell is equipped with the MTJ element of the present invention. A switching element is connected to the wiring connected to the MTJ element via the electrode in order to control the current flowing through the MTJ element. A C-MOS transistor can be used as the switching element. The C-MOS transistor is composed of two n-type semiconductors and one p-type semiconductor sandwiched between them. An electrode serving as a drain is electrically connected to the n-type semiconductor and connected to the ground via a wiring. The other n-type semiconductor is electrically connected to a source electrode.

  The source electrode is connected to the lower electrode of the MTJ element through a wiring. The bit line is connected to the upper electrode of the MTJ element. Further, a gate electrode is provided in the p-type semiconductor, and the current flowing through the MRJ element is controlled on / off by controlling ON / OFF of the current between the source electrode and the drain electrode by ON / OFF of the gate electrode. In the magnetic memory cell configured as described above, the magnetic information is recorded by rotating the magnetization direction of the recording layer of the MTJ element by the current flowing through the MTJ element, that is, the spin transfer torque. The spin transfer torque is not a spatial external magnetic field, but a principle in which spins of a spin-polarized current that mainly flows in the MTJ element give torque to the magnetic moment of the ferromagnetic recording layer of the MTJ element. Accordingly, the MTJ element is provided with means for supplying current from the outside, and spin transfer torque magnetization reversal is realized by flowing current using the means. In this embodiment, the direction of magnetization of the recording layer in the MTJ element is controlled by turning on and off the current flowing between the bit line and the source electrode.

  A magnetic random access memory includes the magnetic memory cells arranged in an array. A word line and a bit line connected to the gate electrode are electrically connected to a magnetic memory cell including an MTJ element. By disposing the magnetic memory cell having the MTJ element of the present invention, the magnetic random access memory of the present invention can operate with lower power consumption than the conventional one, and the reduction in thermal stability due to miniaturization is reduced. A gigabit-class high-density magnetic memory can be realized. As a means for selecting a desired magnetic memory cell from a plurality of magnetic memory cells and reading or writing information to the selected magnetic memory cell, a write driver connected to a word line and a bit line are connected. Has a writing driver.

  In writing in this configuration, first, a write enable signal is sent to a write driver connected to a bit line to which a current is to be supplied to boost the voltage, and a predetermined current is supplied to the bit line. In accordance with the direction of the current, the write driver is dropped to the ground, and the current direction is controlled by adjusting the potential difference. Next, after a predetermined time elapses, a write enable signal is sent to the write driver connected to the word line to boost the write driver and turn on the transistor connected to the MTJ element to be written. As a result, a current flows through the MTJ element, and spin torque magnetization reversal is performed. After the transistor is turned on for a predetermined time, the signal to the write driver is disconnected and the transistor is turned off. At the time of reading, only the bit line connected to the MTJ element to be read is boosted to the reading voltage V, only the selection transistor is turned on, and a current is supplied to perform reading. Since this structure is the simplest arrangement of one transistor and one memory cell, the area occupied by the unit cell can be reduced and highly integrated.

  Further, since the tunnel magnetoresistive element of the present invention is used, the magnetic memory and the random access memory according to the present embodiment can cope with ultra-high integration because reduction in thermal stability due to miniaturization can be reduced. It will be something.

  In the above, an example in which the recording layer, the fixed layer, and the second magnetic layer are Nd—Fe—B layers in the tunnel magnetoresistive element has been described. However, the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer are described. At least one of the layers may be an Nd—Fe—B layer. For example, as shown in FIG. 2, the fixed layer and the second magnetic layer can be Nd—Fe—B layers. In addition to the effect obtained by using the second magnetic layer as the Nd—Fe—B layer as in FIG. 1, the effect obtained by making the layer in contact with the barrier layer more highly oriented is achieved. Become. Furthermore, as shown in FIG. 3, the second magnetic layer can be an Nd—Fe—B layer. By adopting a structure in which a material (such as CoFeB) having a high electron spin polarizability is disposed on both sides of the barrier layer, the resistance change rate (TMR ratio) can be improved in the perpendicular magnetization MTJ element. Although not shown in the figure, the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer can all be Nd—Fe—B layers.

<Example>
Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples, and the effects of the present invention will be illustrated. These examples are for illustration and specific description, and the present invention is not limited to these examples.

Example 1
FIG. 1 is a schematic cross-sectional view of the MTJ element in Example 1. The material of each layer is shown below. MgO (film thickness: 1 nm) was used for the barrier layer 14. Nd2Fe14B (film thickness: 1 nm) was used for the recording layer 15 made of a ferromagnetic thin film having perpendicular magnetic anisotropy disposed in contact with one side surface. Further, Nd 2 Fe 14 B (film thickness: 1 nm) is disposed on the fixed layer 13 made of a ferromagnetic thin film that is disposed in contact with the other side surface of the barrier layer 14 and has perpendicular magnetic anisotropy and the magnetization direction is fixed in one direction. ) Was used. Ta (film thickness: 0.5 nm) is used for the first intermediate layer 16 in contact with the side opposite to the barrier layer of the recording layer 15 and the second intermediate layer 12 in contact with the side opposite to the barrier layer of the fixed layer 13. It was. Two layers of CoFe (film thickness: 0.2 nm) and Pd (film thickness: 1.2 nm) were laminated three times on the first magnetic layer 17 in contact with the opposite side of the recording layer of the first intermediate layer 16. A multilayer film (film thickness: 4.2 nm) was used. Nd 2 Fe 14 B (film thickness: 1 nm) was used for the second magnetic layer 11 in contact with the side surface opposite to the fixed layer of the second intermediate layer 12. A Ta layer was used as the lower electrode 10. The cap layer 18 was a Ta layer, and an upper electrode 19 having a laminated structure of Cr / Au was disposed.

A method for manufacturing a thin film will be specifically described.
Each of the above layers was sequentially formed on a silica substrate by RF sputtering using Ar gas. This MTJ element was cut out to 8 mmφ. The cut out sample was placed at the maximum magnetic field strength portion in the self-made single mode cavity type microwave irradiation apparatus. The sample was inserted into a quartz test tube. The test tube was depressurized using a turbo molecular pump. The sample temperature was measured using a radiation thermometer. The microwave output was pulse-controlled at about 500 W so that the sample temperature reached a maximum of 700 ° C., and irradiated with 2.45 GHz microwave for about 10 minutes to crystallize the recording layer, the fixed layer, and the second magnetic layer.

  The crystal structure of the second magnetic layer was c-axis oriented perpendicular to the second intermediate layer Ta surface. Since the second magnetic layer Nd2Fe14B layer is oriented and has a characteristic of high perpendicular magnetic anisotropy, the fixed layer is magnetically stable. Since the fixed layer and the ferromagnetic layer outside the fixed layer are assumed to be Nd2Fe14B, the c-axis oriented Nd2Fe14B acts to pin the magnetization of the fixed layer, and the magnetization fluctuation of the fixed layer when an electric current is passed. It is estimated that it can be sealed strongly.

(Example 2)
FIG. 2 is a schematic cross-sectional view of the MTJ element in Example 2. The material of each layer is shown below. MgO (film thickness: 1 nm) was used for the barrier layer 24. CoFeB (film thickness: 1 nm) was used for the recording layer 25 made of a ferromagnetic thin film having perpendicular magnetic anisotropy disposed in contact with one side surface. Further, Nd 2 Fe 14 B (film thickness: 1 nm) is formed on the fixed layer 23 made of a ferromagnetic thin film that is arranged in contact with the other side surface of the barrier layer 24 and has perpendicular magnetic anisotropy and the magnetization direction is fixed in one direction. ) Was used. Ta (film thickness: 0.5 nm) is used for the first intermediate layer 26 in contact with the side surface opposite to the barrier layer of the recording layer 25 and the second intermediate layer 22 in contact with the side surface opposite to the barrier layer of the fixed layer 23. It was. Two layers of CoFe (film thickness: 0.2 nm) and Pd (film thickness: 1.2 nm) were laminated in three cycles on the first magnetic layer 27 in contact with the opposite side of the recording layer of the first intermediate layer 26. A multilayer film (film thickness: 4.2 nm nm) was used. Nd 2 Fe 14 B (film thickness: 1 nm) was used for the second magnetic layer 21 in contact with the side surface opposite to the fixed layer of the second intermediate layer 22. A Ta layer was used as the lower electrode 20. The cap layer 28 was a Ta layer, and an upper electrode 29 having a Cr / Au laminated structure was disposed.

  A method for manufacturing a thin film will be specifically described. Each of the above layers was sequentially formed on a silica substrate by RF sputtering using Ar gas. This MTJ element was cut out to 8 mmφ. The cut out sample was placed at the maximum magnetic field strength portion in the self-made single mode cavity type microwave irradiation apparatus. The sample was inserted into a quartz test tube. The test tube was depressurized using a turbo molecular pump. The sample temperature was measured using a radiation thermometer. The microwave output was pulse-controlled at about 500 W so that the sample temperature reached a maximum of 700 ° C., and irradiated with 2.45 GHz microwave for about 10 minutes to crystallize the recording layer, the fixed layer, and the second magnetic layer.

  In the fixed layer, the crystal structure was c-axis oriented perpendicular to the plane of the barrier layer MgO and the second intermediate layer Ta. The crystal structure of the second magnetic layer was c-axis oriented perpendicular to the second intermediate layer Ta surface. Since the second magnetic layer Nd2Fe14B layer is sufficiently oriented and has a large perpendicular magnetic anisotropy, the fixed layer is magnetically stable and exhibits excellent characteristics. Since the fixed layer and the ferromagnetic layer outside the fixed layer are assumed to be Nd2Fe14B, the c-axis oriented Nd2Fe14B acts to pin the magnetization of the fixed layer, and the magnetization fluctuation of the fixed layer when an electric current is passed. It is estimated that it can be sealed strongly.

(Example 3)
FIG. 3 is a schematic cross-sectional view of the MTJ element in Example 3. The material of each layer is shown below. MgO (film thickness: 1 nm) was used for the barrier layer 34. CoFeB (film thickness: 1 nm) was used for the recording layer 35 made of a ferromagnetic thin film having perpendicular magnetic anisotropy arranged in contact with one side surface. In addition, CoFeB (film thickness: 1 nm) is formed on the fixed layer 33 made of a ferromagnetic thin film that is disposed in contact with the other side surface of the barrier layer 34 and has perpendicular magnetic anisotropy and the magnetization direction is fixed in one direction. ) Was used. Ta (film thickness: 0.5 nm) is used for the first intermediate layer 36 in contact with the side opposite to the barrier layer of the recording layer 35 and the second intermediate layer 32 in contact with the side opposite to the barrier layer of the fixed layer 33. It was. A two-layered film of CoFe (film thickness: 0.2 nm) and Pd (film thickness: 1.2 nm) was laminated in three cycles on the first magnetic layer 37 in contact with the side opposite to the recording layer of the first intermediate layer 36. A multilayer film (film thickness: 4.2 nm) was used. Nd 2 Fe 14 B (film thickness: 1 nm) was used for the second magnetic layer 31 in contact with the side surface opposite to the fixed layer of the second intermediate layer 32. A Ta layer was used as the lower electrode 30. The cap layer 38 is a Ta layer, and the upper electrode 30 having a laminated structure of Cr / Au is disposed.

A method for manufacturing a thin film will be specifically described.
Each of the above layers was sequentially formed on a silica substrate by RF sputtering using Ar gas. This MTJ element was cut out to 8 mmφ. The cut out sample was placed at the maximum magnetic field strength portion in the self-made single mode cavity type microwave irradiation apparatus. The sample was inserted into a quartz test tube. The test tube was depressurized using a turbo molecular pump. The sample temperature was measured using a radiation thermometer. The microwave output was pulse-controlled at about 500 W so that the sample temperature reached a maximum of 700 ° C., and irradiated with 2.45 GHz microwave for about 10 minutes to crystallize the recording layer, the fixed layer, and the second magnetic layer.

In the fixed layer, the crystal structure was c-axis oriented perpendicular to the plane of the barrier layer MgO and the second intermediate layer Ta. The crystal structure of the second magnetic layer was c-axis oriented perpendicular to the second intermediate layer Ta surface. Since the second magnetic layer Nd2Fe14B layer is sufficiently oriented and has a large perpendicular magnetic anisotropy, the fixed layer is magnetically stable and exhibits excellent characteristics. Since the recording layer / fixed layer is CoFeB and the ferromagnetic layer outside the fixed layer is Nd2Fe14B, the c-axis oriented Nd2Fe14B acts to pin the magnetization of the fixed layer. It is presumed that the magnetization fluctuation of the fixed layer can be strongly sealed.

Claims (9)

A recording layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy disposed in contact with one side of the barrier layer;
A fixed layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy and having a magnetization direction fixed in one direction, disposed in contact with the other side surface of the barrier layer;
A first intermediate layer in contact with the side opposite to the barrier layer of the recording layer;
A barrier layer of the fixed layer and a second intermediate layer in contact with the opposite side surface,
A first magnetic layer in contact with the side opposite to the recording layer of the first intermediate layer and a second magnetic layer in contact with the side opposite to the fixed layer of the second intermediate layer;
At least one of the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer is an Nd—Fe—B layer.   Crystal having orientation obtained by performing alternating electromagnetic field irradiation treatment at the same time and / or after at least one step selected from the steps of forming the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer The tunnel magnetoresistive element according to claim 1, wherein a layer including a structure is disposed.   The tunnel magnetoresistive effect element according to claim 2, wherein the alternating electromagnetic field irradiation treatment is performed at a thin film temperature of 1500 ° C. or less.   The tunnel magnetoresistive effect element of Claim 2 or 3 whose frequency of the alternating electromagnetic field in the said alternating electromagnetic field irradiation process is 300 MHz-1 THz.   The tunnel magnetoresistive effect element according to any one of claims 2 to 4, wherein an output of the alternating electromagnetic field in the alternating electromagnetic field irradiation treatment is 1 mW to 1 MW.   The thin film according to any one of claims 2 to 5, wherein the alternating electromagnetic field irradiation in the alternating electromagnetic field irradiation treatment is pulse irradiation or continuous irradiation.   The tunnel magnetoresistive effect element of any one of Claims 2-6 by which the process of forming each said layer is performed under pressure, air | atmosphere, or pressure reduction. A tunnel magnetoresistive element having a recording layer and a fixed layer;
An electrode for passing a current through the tunnel magnetoresistive element;
A switching element that controls on / off of the current flowing through the tunnel magnetoresistive element,
In a magnetic memory cell in which the magnetization of the recording layer can be reversed by spin transfer torque,
The tunnel magnetoresistive element is
A recording layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy disposed in contact with one side of the barrier layer;
A fixed layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy and having a magnetization direction fixed in one direction, disposed in contact with the other side surface of the barrier layer;
A first intermediate layer in contact with the side opposite to the barrier layer of the recording layer;
A barrier layer of the fixed layer and a second intermediate layer in contact with the opposite side surface,
A first magnetic layer in contact with the side opposite to the recording layer of the first intermediate layer and a second magnetic layer in contact with the side opposite to the fixed layer of the second intermediate layer;
A magnetic memory cell, wherein at least one of the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer is an Nd—Fe—B layer. A plurality of magnetic memory cells;
Means for selecting a desired magnetic memory cell from the plurality of magnetic memory cells;
In a random access memory comprising means for reading or writing information to the selected magnetic memory cell,
The magnetic memory cell controls on / off of a tunnel magnetoresistive effect element having a recording layer and a fixed layer, an electrode for passing a current through the tunnel magnetoresistive effect element, and a current flowing through the tunnel magnetoresistive effect element A switching element,
The tunnel magnetoresistive element is
A recording layer made of a ferromagnetic thin film having perpendicular magnetic anisotropy arranged in contact with one side of the barrier layer and a magnetic layer having perpendicular magnetic anisotropy arranged in contact with the other side of the barrier layer A fixed layer made of a ferromagnetic thin film in which the direction of is fixed in one direction,
A first intermediate layer in contact with the side opposite to the barrier layer of the recording layer;
A barrier layer of the fixed layer and a second intermediate layer in contact with the opposite side surface,
A first magnetic layer in contact with the side opposite to the recording layer of the first intermediate layer and a second magnetic layer in contact with the side opposite to the fixed layer of the second intermediate layer;
At least one of the recording layer, the fixed layer, the first magnetic layer, and the second magnetic layer is an Nd—Fe—B layer,
The random access memory according to claim 1, wherein the means for writing information to the selected magnetic memory cell reverses the magnetization of the recording layer of the magnetic memory cell by a spin transfer torque.

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