Method for manufacturing magnetic tunnel junction element and precursor of magnetic tunnel junction element

Abstract

One embodiment of the present invention provides a method for manufacturing a magnetic tunnel junction element, the method including the following steps: a first preparation step in which a first laminate is prepared by laminating an antiferromagnetic layer on a base layer cooled to a prescribed cooling temperature, the antiferromagnetic layer being configured to exhibit an abnormal Hall effect; a second preparation step in which a second laminate is prepared by laminating a laminate including a ferromagnetic layer on the first laminate; and an annealing step in which the entire second laminate is annealed at an annealing temperature higher than the cooling temperature.

Description

Method for manufacturing a magnetic tunnel junction element and a precursor of a magnetic tunnel junction element

[0001] The present invention relates to a method for manufacturing a magnetic tunnel junction element and a precursor for a magnetic tunnel junction element.

[0002] Patent Document 1 discloses a magnetoresistive element equipped with a magnesium oxide passivation layer and a high-speed, ultra-low-power non-volatile memory using the same. This memory incorporates an MgO passivation layer on the sidewalls of a tunnel magnetoresistance (TMR) film consisting of a ferromagnetic free layer, an insulating layer, and a ferromagnetic fixed layer, as well as a protective layer and an orientation control layer. This suppresses elemental diffusion from each layer of the tunnel magnetoresistance (TMR) element due to heat treatment at 350°C or higher, thereby realizing a magnetic memory cell and magnetic random access memory with stable high-power read and low-current write characteristics. Furthermore, when CoFeB is used for the ferromagnetic layer and MgO for the insulating layer, the MgO passivation layer is oriented to (001).

[0003] International Publication No. 2010 / 067520

[0004] However, there is still room for improvement in magnetic tunnel junction elements that utilize this tunnel magnetoresistance effect.

[0005] According to one aspect of the present invention, a method for manufacturing a magnetic tunnel junction element is provided, comprising the following steps: a first preparation step, in which a first laminate is prepared by laminating an antiferromagnetic layer onto a substrate cooled to a specified cooling temperature, wherein the antiferromagnetic layer is configured to exhibit an anomalous Hall effect; a second preparation step, in which a second laminate is prepared by laminating a laminate containing a ferromagnetic layer onto the first laminate; and an annealing step, in which the entire second laminate is annealed at an annealing temperature higher than the cooling temperature.

[0006] This configuration makes it possible to provide a novel magnetic tunnel junction element.

[0007] This figure shows an example of the configuration of a tunnel junction element. This figure shows an example of the configuration of a manufacturing apparatus for MTJ elements. This flowchart shows an example of the flow of a manufacturing method for MTJ elements.

[0008] Embodiments of the present invention will be described below with reference to the drawings. The various features shown in the embodiments below can be combined with each other.

[0009] 1. Diagram 1 shows an example of the configuration of a magnetic tunnel junction element.

[0010] As shown in Figure 1, the magnetic tunnel junction (MTJ) element 11 comprises a substrate 100 and an underlayer 102 as a base layer, a storage layer M, an insulating layer 108, and a fixed layer F. The MTJ element 11 may further comprise an upper layer 112. The MTJ element 11 (or a memory equipped therewith) can be used, for example, in MRAM (Magnetic Random Access Memory), magnetic heads of HDDs (Hard Disk Drives), racetrack memory, etc. The MTJ element 11 is envisioned to be used, for example, in STT (Spin Transfer Torque) type MRAM or SOT (Spin Orbit Torque) type MRAM, but it may also be used in conventional Vertical MRAM.

[0011] The substrate 100 is made of any material used for memory applications, such as silicon. The substrate 100 may also be a flexible substrate.

[0012] The base layer 102 may include layers that perform various mechanical or electromagnetic functions, such as electrodes that can be electrically connected to external elements. The base layer 102 can be laminated on the substrate 100.

[0013] The memory layer M is configured to have spontaneous magnetization. Spontaneous magnetization is not limited to that caused by ferromagnetic magnetic order, but may include that caused by antiferromagnetic magnetic order, such as so-called angle-tilted antiferromagnetism and ferrimagnetism. In this embodiment, the magnetization direction of the memory layer M is aligned with the stacking direction in which each layer is stacked in the MTJ element 11. The magnetization direction of the memory layer M is configured to be reversible in response to an input signal. The input signal is a signal for reversing the magnetization direction of the memory layer M and is configured to impart spin angular momentum to the memory layer M. In this embodiment, the memory layer M includes an antiferromagnetic layer 104 and a first ferromagnetic layer 106.

[0014] The antiferromagnetic layer 104 is a layer that exhibits the anomalous Hall effect, and may contain, for example, a non-collinear antiferromagnet. The non-collinear antiferromagnet can easily rotate spins, for example, by polarization caused by a magnetic octupole. Accordingly, the sign of the anomalous Hall coefficient of the antiferromagnet is configured to be reversible in accordance with data written into the MTJ element 11.

[0015] For example, the antiferromagnetic layer 104 contains Mn and at least one element selected from the group consisting of Sn, Ga, Ge, Pt, Ir, and Rh as main components. Specifically, for example, the non-collinear antiferromagnet contained as a main component in the antiferromagnetic layer 104 is Mn ３ Sn, Mn ３ Pt, Mn ３ Ge, Mn ３ Ga, and Mn ３ composed of one or more substances selected from the group of Ir. The non-collinear antiferromagnet contained as a main component in the antiferromagnetic layer 104 is, for example, Mn ３ Sn, Mn ３ Ge, Mn ３ Ga and other Mn ３ X-based alloys. Regarding the composition ratio of the Mn ３ X-based alloy, it is preferable that the Mn content is 2.5 times or more and 5 times or less relative to the content of Sn, Ge, or Ga (including those containing a plurality of these). From such an antiferromagnet, the anomalous Hall effect is observed under a condition with no magnetic field. The antiferromagnet is, for example, an antiferromagnet in which the anomalous Hall effect is observed at a temperature of room temperature or higher. The antiferromagnet is, for example, an antiferromagnet capable of taking at least two values by spin rotation. In the present embodiment, the antiferromagnetic layer 104 is Mn ３ composed of Sn, and can be laminated on the underlayer 102.

[0016] In the MTJ element 11 according to the present embodiment, the antiferromagnetic layer 104 is formed by being annealed at a prescribed annealing temperature. According to such a configuration, diffusion of magnetic elements in the antiferromagnetic layer can be appropriately suppressed while promoting crystallization of the antiferromagnetic layer. The annealing temperature corresponds to the antiferromagnet contained in the antiferromagnetic layer 104 (e.g., Mn ３The temperature at which the Sn(s) order is performed is arbitrary, but for example, it is 300-550°C, 330-500°C, or 340-450°C. In the MTJ element 11, the antiferromagnetic layer 104 may be annealed at a temperature of 300°C to 550°C. Specifically, for example, the annealing temperature is 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550°C, and may be within the range of any two of the values ​​exemplified here.

[0017] The first ferromagnetic layer 106 may be composed of a ferromagnetic material used in ferromagnetic MTJ elements, such as Co, CoFeB, or CoFe. In other words, the ferromagnetic material may contain magnetic elements having a magnetic moment. Examples of such magnetic elements include Fe, Co, Ni, Nd, Gd, and Tb. The first ferromagnetic layer 106 functions as a free layer in the MTJ element 11. The material constituting the first ferromagnetic layer 106 is not particularly limited as long as it is a material that functions as a free layer, such as CoFeB or CoFe. The first ferromagnetic layer 106 may be a single layer or a multi-layer layer. Furthermore, since the first ferromagnetic layer 106 functions as a free layer, it may contain magnetic materials other than the ferromagnetic material mentioned above, as well as non-magnetic materials. The first ferromagnetic layer 106 is laminated on the antiferromagnetic layer 104.

[0018] Here, the polarity of the antiferromagnetic layer 104 and the magnetization direction of the first ferromagnetic layer 106 are configured to reverse in conjunction with each other. For example, when the magnetization direction of the first ferromagnetic layer 106 is reversed, the polarity of the anomalous Hall effect in the antiferromagnetic layer 104 (i.e., the sign of the Hall voltage with respect to the current) is reversed. This is achieved by the magnetic coupling between the antiferromagnetic layer 104 and the first ferromagnetic layer 106 through magnetic interaction. For example, when the magnetization direction of the first ferromagnetic layer 106 is reversed, the magnetic structure of the antiferromagnetic layer 104 is reversed. Such reversal of the magnetic structure in the antiferromagnetic layer 104 causes a reversal of the polarity of the anomalous Hall effect. Other layers may be interposed between the antiferromagnetic layer 104 and the first ferromagnetic layer 106, as long as the interdependence between the antiferromagnetic layer 104 and the first ferromagnetic layer 106 is maintained.

[0019] The insulating layer 108 is laminated on the memory layer M (for example, the first ferromagnetic layer 106). The insulating layer 108 is a non-magnetic insulating layer provided to exhibit TMR. The insulating layer 108 is not particularly limited as long as it functions as an insulating layer, such as MgO, AlOx, TiOx, etc.

[0020] The fixed layer F is configured to be fixed regardless of the data (e.g., input signal) written to the MTJ element 11. The magnetization direction of the fixed layer F is along the stacking direction, similar to the magnetization direction of the memory layer M. Here, the magnetization direction of the memory layer M is either parallel or antiparallel to the magnetization direction of the fixed layer F for each partial magnetic domain. As a result, the MTJ element 11 is configured to read the magnetization direction of the memory layer M as data 0 or 1 based on the difference in resistance between the parallel spin state and the antiparallel spin state due to the tunnel magnetoresistance effect. The fixed layer F is stacked on an insulating layer 108. For example, the insulating layer 108 is placed between the memory layer M and the fixed layer F, thereby forming a tunnel magnetic junction between the memory layer M and the fixed layer F. In this embodiment, the fixed layer F includes a second ferromagnetic layer 110.

[0021] The second ferromagnetic layer 110 may be a ferromagnetic material used in ferromagnetic MTJ elements, such as CoFeB or CoFe. The second ferromagnetic layer 110 functions as a fixed layer in the MTJ element. The material constituting the second ferromagnetic layer 110 is not particularly limited as long as it functions as a fixed layer F. The second ferromagnetic layer 110 may be a single layer or a multi-layer layer. Furthermore, the second ferromagnetic layer 110 may include magnetic or non-magnetic materials other than the ferromagnetic materials mentioned above, such as synthetic antiferromagnet (SAF). The MTJ element 11 may have a structure in which an antiferromagnetic material such as MnPt or MnIr is laminated on the second ferromagnetic layer 110 in order to make the second ferromagnetic layer 110 function as a fixed layer F. That is, at least one of the memory layer M and the fixed layer F may include an antiferromagnetic layer that exhibits an anomalous Hall effect, a barrier layer, and a ferromagnetic layer. This configuration suppresses the diffusion of magnetic elements contained in the antiferromagnetic layer and appropriately promotes the ordering of the antiferromagnetic layer. The magnetization direction of the ferromagnetic material constituting the second ferromagnetic layer 110 is fixed regardless of the data written to the MTJ element 11.

[0022] The second ferromagnetic layer 110 is laminated on the insulating layer 108. For example, the insulating layer 108 may be placed between the second ferromagnetic layer 110 and the first ferromagnetic layer 106. The antiferromagnetic layer 104 is configured to be connected to the insulating layer 108 via the first ferromagnetic layer 106. With such a configuration, an antiferromagnetic layer 104 having crystallinity suitable for the structure of the first ferromagnetic layer 106 can be obtained. Preferably, the ferromagnetic material constituting the second ferromagnetic layer 110 and the ferromagnetic material constituting the first ferromagnetic layer 106 contain at least the element Co as particles having a magnetic moment, and more preferably, are composed of Co or CoFeB.

[0023] The upper layer 112 is a layer provided on top of the second ferromagnetic layer 110, which serves as the fixed layer F. The upper layer 112 may consist of electrodes or a layer made of a material based on known techniques for making the MTJ element 11 function more efficiently. The configuration of the upper layer 112 is not particularly limited. For example, the upper layer 112 is laminated on the second ferromagnetic layer 110.

[0024] The spin magnetization direction of the antiferromagnetic layer 104, the first ferromagnetic layer 106, and / or the second ferromagnetic layer 110 is preferably perpendicular (i.e., in the stacking direction), but it may also be in the in-plane direction.

[0025] The specific form of the MTJ element 11 is not limited to this. For example, in the above embodiment, the base layer 102, memory layer M, insulating layer 108, fixed layer F, and upper layer 112 are stacked in order on the substrate 100, but for example, the stacking order of the memory layer M and fixed layer F on the substrate 100 may be reversed. Also, the memory layer M is stacked on the substrate 100 in the order of antiferromagnetic layer 104 and first ferromagnetic layer 106, but the stacking order of the antiferromagnetic layer 104 and first ferromagnetic layer 106 may be reversed.

[0026] 2. Manufacturing apparatus for MTJ elements Next, an example of a manufacturing apparatus for MTJ elements described in the previous section will be explained. Figure 2 is a diagram showing an example of the configuration of an MTJ element manufacturing apparatus. As shown in Figure 2, the manufacturing apparatus 1 comprises a chamber 2, a stage 3, an atmosphere control unit 4, an annealing unit 5, a lamination unit 6, and a cooling device 7.

[0027] Chamber 2 is configured to accommodate the sample S. The sample S is a precursor of the MTJ element 11 and can change stepwise depending on the processing state, for example, a substrate 100. In its initial state, the sample S is a base layer (substrate 100 or underlayer 102).

[0028] Stage 3 is configured to accommodate the sample S. MTJ elements are manufactured by performing various processes on the substrate 100 and other components placed in Stage 3.

[0029] The atmosphere control unit 4 is configured to control the atmosphere inside the chamber 2. The atmosphere control unit 4 includes, for example, a vacuum pump and a replacement gas supply unit.

[0030] The annealing unit 5 is configured to anneal the sample S so that its temperature reaches a predetermined annealing temperature. The specific method of annealing by the annealing unit 5 is arbitrary and may include, for example, substrate heating, lamp heating, laser heating, etc.

[0031] The stacking unit 6 is configured to stack various layers such as the antiferromagnetic layer 104 described above on the sample S. Although the specific embodiment of stacking by the stacking unit 6 is arbitrary, for example, any method such as sputtering, vapor deposition, molecular beam epitaxy (MBE), plating, sintering, printing, and attaching can be used.

[0032] The cooling device 7 is configured to cool the sample S. For example, the cooling device 7 is connected to the stage 3 and cools the sample S by absorbing heat from the sample S through the stage 3.

[0033] The manufacturing apparatus 1 may also include various sensors for observing the state of the sample S on the stage 3 (e.g., stacking state, temperature, atmosphere, etc.) and processing apparatuses for performing various processing such as wiring processing on the sample S.

[0034] 3. Manufacturing Method of MTJ Element Next, the manufacturing methods of various MTJ elements described in the previous section will be described. FIG. 3 is a flowchart showing an example of the flow of the manufacturing method for an MTJ element. Note that the order of each step included in the manufacturing method shown in FIG. 3 can be changed as appropriate. For example, the manufacturing method includes a base layer placing step S1, a cooling step S2, a first stacking step S3, a second stacking step S4, and an annealing step S5.

[0035] The base layer placing step S1 is a step of placing a base layer on the stage 3 connected to the cooling device 7. Thereby, the base layer is thermally connected to the stage 3. The base layer may be the substrate 100 alone, or may be a sample in a state where the underlayer 102 is stacked on the substrate 100.

[0036] Cooling step S2 is a step of cooling the base layer on the stage 3 to a specified cooling temperature using a cooling device 7. For example, the cooling temperature is a temperature at which the antiferromagnetic layer 104 to be laminated in the next first lamination step S3 can form amorphous material on the base layer. For example, the cooling temperature is below the normal temperature (i.e., room temperature) inside the chamber 2 when the annealing unit 5 is not in operation. For example, the cooling temperature is less than 27°C, preferably 0°C or below. With such a configuration, the amorphous formation of the antiferromagnetic layer 104 can be further promoted. Alternatively, the cooling temperature may be, for example, -150°C or higher, preferably -100°C or higher, and more preferably -50°C or higher. Specifically, for example, the cooling temperature may be -150, -140, -130, -120, -110, -100, -90, -80, -70, -60, -50, -40, -30, -20, -10, 0, 10, 20, or 26°C, and may be within the range of any two of the values ​​exemplified here. For example, the cooling temperature may be -150°C or higher and less than 27°C, -150°C or higher and 0°C or lower, -100°C or higher and less than 27°C, -100°C or higher and 0°C or lower, -50°C or higher and less than 27°C, or -50°C or higher and 0°C or lower. In a steady state, the cooling temperature is measured from the temperature of the base layer in the chamber 2. The cooling temperature is measured, for example, using a resistance thermometer provided on the stage 3. Ideally, the substrate temperature should match the temperature of the stage 3 and, furthermore, the target temperature set by the cooling device 7. However, it can fluctuate due to various factors such as the heat conduction efficiency of the stage 3, radiant heat from the inner wall of the chamber 2, and the thermal resistance between the stage 3 and the substrate.

[0037] The first lamination step S3 is a step of laminating an antiferromagnetic layer 104 on a base layer cooled to a cooling temperature by using a lamination section 6. It is preferable that cooling by the cooling device 7 is continuously performed while the first lamination step S3 is being performed. In the first lamination step S3, the antiferromagnetic layer 104 may be laminated on a base layer that has once been cooled to the cooling temperature, then cooled is stopped and the temperature thereof has risen. In this case, it is preferable that the first lamination step S3 is completed while the temperature of the base layer is kept at or below the temperature at which the antiferromagnetic layer 104 can form an amorphous phase on the base layer. In the present embodiment, through the base layer placement step S1, the cooling step S2, and the first lamination step S3, a first laminate obtained by laminating the antiferromagnetic layer 104 on the base layer cooled to the cooling temperature is prepared. The base layer placement step S1, the cooling step S2, and the first lamination step S3 are an example of a first preparation step.

[0038] The second lamination step S4 prepares a second laminate by laminating a ferromagnetic laminate including a ferromagnetic layer 106 (or a ferromagnetic layer 110) on the first laminate by using the lamination section 6. The second lamination step S4 is an example of a second preparation step. The ferromagnetic laminate may be composed of only the first ferromagnetic layer 106, or may include other layers.

[0039] Such a second laminate becomes an MTJ element 11 having desired magnetic properties by being annealed. Therefore, the second laminate can also be referred to as a precursor of the MTJ element 11. As described above, the precursor includes a memory layer, an insulating layer 108, and a pinned layer F. Each of the memory layer M and the pinned layer F is configured to have spontaneous magnetization. The insulating layer 108 is disposed between the memory layer M and the pinned layer F, and is thereby configured to form a tunnel magnetic junction between the memory layer M and the pinned layer F. At least one of the memory layer M and the pinned layer F includes the antiferromagnetic layer 104 that exhibits an anomalous Hall effect, and the first ferromagnetic layer 106. At least one of the memory layer M and the pinned layer F is configured such that the polarity of the antiferromagnetic layer 104 and the direction of spontaneous magnetization of the first ferromagnetic layer 106 are reversed in conjunction with each other. The antiferromagnetic layer 104 contains an amorphous antiferromagnetic material.

[0040] In the annealing process S5, the entire second laminate is annealed at an annealing temperature higher than the cooling temperature in the cooling process S2 by controlling the annealing section 5, etc. This annealing temperature is a temperature that can promote the crystallization of the first ferromagnetic layer 106. Here, if the antiferromagnetic layer 104 is polycrystalline or monocrystalline, annealing at a high temperature exceeding 500°C is required for the ordering of the antiferromagnetic layer 104. However, on the other hand, the crystallization of the ferromagnetic layers 106 and 110 is at a lower annealing temperature than the annealing temperature required for the ordering of the antiferromagnetic layer 104 (for example, 350°C or lower). Therefore, when annealing the entire second laminate at once, if the annealing temperature is set to a temperature suitable for the ordering of the antiferromagnetic layer 104, it will lead to a decrease in the magnetic properties of the ferromagnetic layers 106 and 110. If the annealing temperature is set to a temperature suitable for the crystallization of the ferromagnetic layers 106 and 110, the ordering of the antiferromagnetic layer 104 will be insufficient, and the magnetic properties of the antiferromagnetic layer 104 will decrease.

[0041] Therefore, the inventors of this invention focused on the fact that the amorphous antiferromagnetic layer 104 tends to have lower energy required for atomic movement compared to the polycrystalline antiferromagnetic layer 104. They found that by stacking ferromagnetic layers 106 and 110 on the amorphous antiferromagnetic layer 104 and annealing these layers together at a relatively low temperature, it is possible to achieve both the ordering of magnetic elements and the crystallization of ferromagnetic layers 106 and 110. With this configuration, the amorphous formation of the antiferromagnetic layer 104 is promoted, thereby promoting the ordering of the antiferromagnetic layer 104 and the crystallization of ferromagnetic layers 106 and 110 at a relatively low annealing temperature. Consequently, it is possible to suppress the reduction of the overall characteristics of the MTJ element 11 due to annealing.

[0042] The annealing temperature is a temperature that can promote the crystallization of the ferromagnetic layers 106 and 110, for example, 250°C or higher. With this configuration, the ordering and crystallization of the compounds constituting the antiferromagnetic layer 104 and the ferromagnetic layers 106 and 110 can be promoted more efficiently, and the performance of the MTJ element 11 can be improved. The annealing temperature may more preferably be 300°C or higher, and even more preferably 320°C or higher. Furthermore, it is preferable that the annealing temperature be 350°C or lower. With this configuration, the MTJ element 11 can be manufactured more efficiently from the viewpoint of suitability of the manufacturing apparatus 1 that performs these processes.

[0043] 4. In addition to the above embodiments, the following embodiments may be applied, for example.

[0044] The laminate described above (the first laminate 1000, etc.) is a precursor of the MTJ element 11 described above, but the thickness of each layer does not substantially change before and after the annealing process. Therefore, the thickness of each layer in the laminate can also be said to be the thickness of each layer in the MTJ element.

[0045] Furthermore, the composition of each layer can be determined, for example, by using a transmission electron microscope and energy-dispersive X-ray spectroscopy to identify the thickness and constituent elements of each layer.

[0046] Note that the configuration of the MTJ element 11 is merely one example of this embodiment. For example, auxiliary layers such as an artificial antiferromagnetic layer may be added to reinforce the function performed by each layer.

[0047] The following configuration is included as an example of the present disclosure. (Item 1) A method for manufacturing an element, comprising: cooling the temperature of a stage on which a substrate is provided to -150°C or more and 0°C or less while depositing the antiferromagnetic layer on top of the substrate; depositing a first ferromagnetic layer on top of the antiferromagnetic layer; depositing a first barrier layer on top of the first ferromagnetic layer; depositing a second ferromagnetic layer on top of the first barrier layer; and annealing these as a laminated structure at a temperature of 250°C or more and 350°C or less. (Item 2) A method for manufacturing a device, comprising the steps of manufacturing elements to be provided in the device, wherein the temperature of a stage on which a substrate is provided is cooled to -150°C or more and 0°C or less, an antiferromagnetic layer is deposited on top of the substrate, a first ferromagnetic layer is deposited on the antiferromagnetic layer, a first barrier layer is deposited on the first ferromagnetic layer, a second ferromagnetic layer is deposited on the first barrier layer, and these are annealed as a laminated structure at a temperature of 250°C or more and 350°C or less.

[0048] A brief explanation of the control method for writing memory using the memory elements shown in each embodiment will be provided. For example, in STT-MRAM, when writing, current is passed in the stacking direction of the MTJ element 11, causing the spin of the antiferromagnetic layer 104 to reverse first. At that time, the spin of the first ferromagnetic layer 106 is also reversed due to magnetic coupling. This makes it possible to write 1s and 0s to the memory. In this case, unlike the spin of a conventional ferromagnetic layer, the spin reversal in the antiferromagnetic layer 104, which has a higher spin reversal speed, is given priority, so the spin can be reversed at a faster speed than the spin reversal of a conventional ferromagnetic layer. The same applies to SOT-MRAM, where the spin reversal occurs first in the antiferromagnetic layer 104, allowing the spin of the first ferromagnetic layer 106 to reverse via magnetic coupling. The same applies to MRAMs that reverse spin using an external magnetic field.

[0049] The above embodiments may also be provided in the following embodiments.

[0050] (1) A method for manufacturing a magnetic tunnel junction element, comprising the following steps: a first preparation step, in which a first laminate is prepared by laminating an antiferromagnetic layer onto a substrate cooled to a specified cooling temperature, wherein the antiferromagnetic layer is configured to exhibit an anomalous Hall effect; a second preparation step, in which a second laminate is prepared by laminating a laminate containing a ferromagnetic layer onto the first laminate; and an annealing step, in which the entire second laminate is annealed at an annealing temperature higher than the cooling temperature.

[0051] With this configuration, the amorphous formation of the antiferromagnetic layer is promoted, thereby facilitating the ordering of the antiferromagnetic layer and the crystallization of the ferromagnetic layer at a relatively low annealing temperature. Therefore, the reduction in the overall properties of the magnetic tunnel junction element due to annealing can be suppressed.

[0052] (2) The manufacturing method described in (1) above, wherein the cooling temperature is less than 27°C.

[0053] This configuration can further promote the amorphous formation of the antiferromagnetic layer.

[0054] (3) A method of manufacturing according to (1) or (2) above, wherein the cooling temperature is 0°C or lower.

[0055] This configuration can further promote the amorphous formation of the antiferromagnetic layer.

[0056] (4) A method of manufacturing according to any one of (1) to (3) above, wherein the cooling temperature is -150°C or higher.

[0057] This configuration can further promote the amorphous formation of the antiferromagnetic layer.

[0058] (5) A method of manufacturing according to any one of (1) to (4) above, wherein the annealing temperature is 250°C or higher.

[0059] (6) A method of manufacturing according to any one of (1) to (5) above, wherein the annealing temperature is 350°C or less.

[0060] This configuration allows for more efficient manufacturing of magnetic tunnel junction elements.

[0061] (7) A method for manufacturing according to any one of (1) to (6) above, wherein in the first preparation step, the base layer is placed on a stage connected to a cooling device, and the antiferromagnetic layer is laminated onto the base layer which has been cooled via the stage, thereby preparing the first laminate.

[0062] (8) A method for manufacturing according to any one of (1) to (7) above, wherein the antiferromagnetic layer mainly contains at least one element from Sn, Ga, Ge, Pt, Ir, and Rh, and Mn.

[0063] (9) In the manufacturing method described in (8) above, the antiferromagnetic layer is Mn ３ A method composed of Sn.

[0064] (10) A precursor for a magnetic tunnel junction element, comprising a memory layer, an insulating layer, and a stationary layer, wherein each of the memory layer and the stationary layer is configured to have spontaneous magnetization, the insulating layer is disposed between the memory layer and the stationary layer so as to form a tunnel magnetic junction between the memory layer and the stationary layer, and at least one of the memory layer and the stationary layer includes an antiferromagnetic layer that exhibits an anomalous Hall effect and a first ferromagnetic layer, wherein the polarity of the antiferromagnetic layer and the direction of spontaneous magnetization of the first ferromagnetic layer are configured to reverse in conjunction with each other, and the antiferromagnetic layer comprises an amorphous antiferromagnetic material. Of course, this is not limited to this.

[0065] Finally, while various embodiments relating to this disclosure have been described, these are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0066] The following describes examples and comparative examples that embody the above embodiments.

[0067] [Regarding the preparation of samples] The inventors prepared the samples for Examples 1 to 5 and Comparative Example 1 using the following procedure.

[0068] First, for each of Examples 1 to 5, the inventors performed a first preparation step, which involved placing a Si substrate (100 μm) on a stage connected to a cooling device, and cooling the substrate to a predetermined cooling temperature Tc via the stage. In Comparative Example 1, however, the substrate was not cooled by the cooling device, and the substrate temperature was approximately 30°C, which is room temperature.

[0069] For a Si substrate (100 μm), Ta (5 nm) / Ru (20 nm) are used as the underlayer, and Mn is used as the antiferromagnetic layer. ３ Laminates according to each of Examples 1 to 5 were fabricated by sequentially stacking Sn (30 nm), CoFeB (1.5 nm) as the first ferromagnetic layer (free layer), MgO (1.0 nm) as the insulating layer, CoFeB (1.2 nm) / Ru (0.9 nm) / CoFe (2.5 nm) / IrMn (10 nm) as the second ferromagnetic layer (fixed layer), and Ta (5 nm) / Ru (5 nm) as the top layer. The numbers in parentheses indicate the thickness of the layer. Each layer was deposited by sputtering. The laminate according to Comparative Example 1 was manufactured using the same procedure as the laminates according to each of Examples 1 to 5, except that each layer was stacked on the substrate without cooling the substrate with a cooling device. The temperature of the substrate when obtaining the laminate according to Comparative Example 1 was approximately 30°C.

[0070] Next, the inventors performed an annealing process on the laminates according to each of Examples 1 to 5 and Comparative Example 1 at a predetermined annealing temperature Ta. The annealing time was 60 minutes, and the annealing atmosphere was an Ar gas atmosphere. As a result, samples (MTJ elements) according to each of Examples 1 to 5 and Comparative Example 1 were obtained.

[0071] [Regarding the evaluation method of the samples] The inventors evaluated whether the spins of the lower CoFeB layer (first ferromagnetic layer) were vertically oriented for the samples of each of Examples 1 to 5 and Comparative Example 1 by magneto-optical Kerr effect (MOKE) measurement. Specifically, the presence or absence of a perpendicular magnetic Kerr signal caused by the vertical orientation of the spins in the lower CoFeB layer was confirmed by measuring the polar Kerr effect. If a perpendicular magnetic Kerr signal was observed, it was judged as "○", and if it was not observed, it was judged as "×". The vertical orientation of the spins in the lower CoFeB layer indicates that the CoFeB layer has good crystallinity based on the epitaxial relationship with the MgO insulating layer, and that the diffusion of Mn elements from the antiferromagnetic layer is suppressed. In other words, the presence or absence of a perpendicular magnetic Kerr signal is a clear indicator of the effectiveness of the batch annealing process.

[0072] [Results and Discussion] The following table shows the cooling temperature Tc, annealing temperature Ta, and evaluation results for the perpendicular magnetic Kerr signal used to obtain the samples for each of Examples 1 to 5 and Comparative Example 1.

[0073]

[0074] As shown in the table above, in Comparative Example 1, no perpendicular magnetic Kerr signal was observed from the lower CoFeB layer. This result indicates that the magnetic properties of the sample were improved by depositing an Mn3Sn layer on a cooled substrate and then performing annealing. One theory suggests that this is because Mn deposited on a substrate at room temperature... ３ Because the Sn layer was formed in a polycrystalline or partially crystalline state, at a relatively low annealing temperature of 300°C, Mn ３ This is thought to be due to insufficient regularization of Sn. Also, Mn ３ It is possible that, under conditions where the Sn elements were not sufficiently ordered, Mn elements diffused into the ferromagnetic and insulating layers, resulting in a deterioration of the crystallinity of the CoFeB layer and the interface quality with MgO.

[0075] In contrast, in Examples 1 to 5, film deposition was performed on a substrate cooled to below room temperature (especially below 10°C), thereby depositing Mn ３ When the Sn layer is stacked, the amount of conventional Mn is similar to that of Comparative Example 1. ３Even at annealing temperatures lower than the annealing temperature required to order Sn (e.g., 500°C), a perpendicular magnetic Kerr signal was observed from the sample. One theory suggests that this result is due to the fact that the amorphous state of Mn3Sn could be promoted by depositing the film on a cooled substrate. Because amorphous materials require less energy for atomic movement compared to polycrystalline materials, even at annealing at a temperature of 300°C, which is suitable for crystallization of the ferromagnetic layer, Mn ３ It appears that the regularization of Sn has progressed sufficiently.

[0076] As shown in Examples 2 and 3, a perpendicular magnetic Kerr signal was observed even when the cooling temperature Tc was below 0°C. It is thought that this amorphous effect becomes more pronounced as the substrate temperature during film formation decreases.

[0077] Furthermore, as shown in Examples 4 and 5, when lamination was performed on a cooled substrate, a perpendicular magnetic Kerr signal was observed even when the annealing temperature was 260°C (below 300°C) or 340°C (above 300°C). This result indicates that the annealing temperature is not limited to 300°C, and Mn ３ This suggests that the temperature is not particularly limited, as long as it is a temperature that can promote the regularization of Sn.

[0078] 1: Manufacturing apparatus, 2: Chamber, 3: Stage, 4: Atmosphere control unit, 5: Annealing unit, 6: Lamination unit, 7: Cooling device, 11: MTJ element, 100: Substrate, 102: Underlayer, 104: Antiferromagnetic layer, 106: First ferromagnetic layer, 108: Insulating layer, 110: Second ferromagnetic layer, 112: Upper layer, 1000: First laminate, F: Fixed layer, M: Memory layer, S: Sample, S1: Substrate installation process, S2: Cooling process, S3: First lamination process, S4: Second lamination process, S5: Annealing process

Claims

1. A method for manufacturing a magnetic tunnel junction element, comprising the following steps: a first preparation step, in which a first laminate is prepared by laminating an antiferromagnetic layer onto a substrate cooled to a specified cooling temperature, wherein the antiferromagnetic layer is configured to exhibit an anomalous Hall effect; a second preparation step, in which a second laminate is prepared by laminating a laminate containing a ferromagnetic layer onto the first laminate; and an annealing step, in which the entire second laminate is annealed at an annealing temperature higher than the cooling temperature.

2. A method for manufacturing according to claim 1, wherein the cooling temperature is less than 27°C.

3. A method for manufacturing according to claim 1, wherein the cooling temperature is 0°C or lower.

4. A method for manufacturing according to claim 1, wherein the cooling temperature is -150°C or higher.

5. A method for manufacturing according to claim 1, wherein the annealing temperature is 250°C or higher.

6. A method for manufacturing according to claim 1, wherein the annealing temperature is 350°C or lower.

7. A method for manufacturing according to claim 1, wherein in the first preparation step, the base layer is placed on a stage connected to a cooling device, and the antiferromagnetic layer is laminated onto the base layer which has been cooled via the stage, thereby preparing the first laminate.

8. A method for manufacturing according to any one of claims 1 to 7, wherein the antiferromagnetic layer mainly contains at least one element from Sn, Ga, Ge, Pt, Ir, and Rh, and Mn.

9. In the manufacturing method described in claim 8, the antiferromagnetic layer is Mn ３ A method composed of Sn.

10. A precursor for a magnetic tunnel junction element, comprising a memory layer, an insulating layer, and a stationary layer, wherein each of the memory layer and the stationary layer is configured to have spontaneous magnetization, the insulating layer is disposed between the memory layer and the stationary layer so as to form a tunnel magnetic junction between the memory layer and the stationary layer, at least one of the memory layer and the stationary layer includes an antiferromagnetic layer that exhibits an anomalous Hall effect and a first ferromagnetic layer, the polarity of the antiferromagnetic layer and the direction of spontaneous magnetization of the first ferromagnetic layer are configured to reverse in conjunction with each other, and the antiferromagnetic layer comprises an amorphous antiferromagnetic material.

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