Patent ID: 12232426

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described below in further detail, with reference to the drawings. The drawings used in the following description may be drawn with specific portions enlarged as appropriate to facilitate comprehension of the features of the present invention, and the dimensional ratios and the like between the constituent elements may differ from the actual values. Further, the materials and dimensions and the like presented in the following examples are merely examples, which in no way limit the present invention, and may be altered as appropriate within the scope of the present invention.

(Spin-Orbit Torque Type Magnetoresistance Effect Element)

FIG.1is a perspective view schematically illustrating a spin-orbit torque type magnetoresistance effect element according to a first embodiment.

The spin-orbit torque type magnetoresistance effect element100according to the first embodiment has a magnetoresistance effect element10and spin-orbit torque wiring20.

In the following description, the stacking direction of the magnetoresistance effect element10is deemed the z-direction, a first direction along which the spin-orbit torque wiring20extends is deemed the x-direction, a second direction which is orthogonal to both the x-direction and the z-direction is deemed the y-direction.

<Magnetoresistance Effect Element>

The magnetoresistance effect element10has a first ferromagnetic metal layer 1 having a fixed magnetization direction, a second ferromagnetic metal layer 2 having a variable magnetization direction, and a non-magnetic layer 3 sandwiched between the first ferromagnetic metal layer 1 and the second ferromagnetic metal layer 2.

The magnetoresistance effect element10functions by having the orientation of the magnetization M1of the first ferromagnetic metal layer 1 fixed in a single direction, whereas the orientation of the magnetization M2of the second ferromagnetic metal layer 2 is able to vary relatively. When applied to coercive force difference (pseudo spin valve) MRAM, the coercive force of the first ferromagnetic metal layer is larger than the coercive force of the second ferromagnetic metal layer, and when applied to exchange bias (spin valve) MRAM, the magnetization direction of the first ferromagnetic metal layer is fixed by exchange coupling with an antiferromagnetic layer.

When the non-magnetic layer 3 is formed from an insulator, the magnetoresistance effect element10is a tunneling magnetoresistance (TMR) element, whereas when the non-magnetic layer 3 is formed from a metal, the magnetoresistance effect element10is a giant magnetoresistance (GMR) element.

The stacking structure of the magnetoresistance effect element can employ a conventional magnetoresistance effect element stacking structure. For example, each layer may be composed of a plurality of layers, and the structure may also include other layers such as an antiferromagnetic layer for fixing the magnetization direction of the first ferromagnetic metal layer 1. The first ferromagnetic metal layer 1 is also called the fixed layer or reference layer, whereas the second ferromagnetic metal layer 2 is also called the free layer or the memory layer.

Conventional materials can be used as the material for the first ferromagnetic metal layer 1. For example, metals selected from the group consisting of Cr, Mn, Co, Fe and Ni, and alloys containing at least one of these metals and having ferromagnetism can be used. Further, alloys containing at least one of these metals and at least one element among B, C and N can also be used. Specific examples include Co—Fe and Co—Fe—B.

Further, in order to achieve higher output, a Heusler alloy such as Co2FeSi is preferably used. Heusler alloys contain intermetallic compounds having a chemical composition of X2YZ, wherein X is a noble metal element or a transition metal element belonging to the Co, Fe, Ni or Cu group of the periodic table, whereas Y is a transition metal belonging to the Mn, V, Cr or Ti group of the periodic table, and can select the elemental species of X, and Z is a typical element of group III to group V. Specific examples include Co2FeSi, Co2MnSi, and Co2Mn1-aFeaAlbSi1-b.

Furthermore, in order to increase the coercive force of the first ferromagnetic metal layer 1 on the second ferromagnetic metal layer 2, an antiferromagnetic material such as IrMn or PtMn may be used as the material that contacts the first ferromagnetic metal layer 1. Moreover, in order to ensure that the leakage magnetic field of the first ferromagnetic metal layer 1 does not affect the second ferromagnetic metal layer 2, a structure having synthetic ferromagnetic coupling may be used.

Furthermore, in those cases where the orientation of the magnetization of the first ferromagnetic metal layer 1 is perpendicular to the stacking surface, a stacked film of Co and Pt is preferably used. Specifically, the structure of the first ferromagnetic metal layer 1 may be [FeB (1.0 nm)/Ta (0.2 nm)/[Pt (0.16 nm)/Co (0.16 nm)]4/Ru (0.9 nm)/Co (0.24 nm)/Pt (0.16 nm)]6in order from the non-magnetic layer 3.

For the material of the second ferromagnetic metal layer 2, a ferromagnetic material, and particularly a soft magnetic material, can be used. Examples of materials that can be used include metals selected from the group consisting of Cr, Mn, Co, Fe and Ni, alloys containing at least one of these metals, and alloys containing at least one of these metals and at least one element among B, C and N. Specific examples include Co—Fe, Co—Fe—B and Ni—Fe.

The orientation of the magnetization of the second ferromagnetic metal layer 2 is z-direction (perpendicular to the stacking surface). In those cases where the orientation of the magnetization of the second ferromagnetic metal layer 2 is z-direction, the size of the magnetoresistance effect element10becomes small. The orientation of the magnetization of the second ferromagnetic metal layer 2 is influenced by the crystal structure constituting the second ferromagnetic metal layer 2 and the thickness of the second ferromagnetic metal layer 2. The thickness of the second ferromagnetic metal layer 2 is preferably not more than 2.5 nm. Because the perpendicular magnetic anisotropy effect is attenuated as the thickness of the second ferromagnetic metal layer 2 is increased, the thickness of the second ferromagnetic metal layer 2 is preferably kept thin.

Conventional materials can be used as the non-magnetic layer 3.

For example, when the non-magnetic layer 3 is formed from an insulator (and forms a tunnel barrier layer), examples of materials that can be used include Al2O3, SiO2, MgO and MgAl2O4. In addition to these materials, materials in which a portion of the Al, Si or Mg has been substituted with Zn or Be or the like can also be used. Among the above materials, MgO and MgAl2O4are materials that enable the realization of coherent tunneling, and therefore enable efficient injection of spin.

Further, when the non-magnetic layer 3 is formed from a metal, examples of materials that can be used include Cu, Au, and Ag and the like.

Furthermore, the magnetoresistance effect element10may also have other layers. For example, the magnetoresistance effect element10may have a base layer on the opposite surface of the second ferromagnetic metal layer 2 from the non-magnetic layer 3, and/or may have a capping layer on the opposite surface of the first ferromagnetic metal layer 1 from the non-magnetic layer 3.

A layer disposed between the spin-orbit torque wiring20and the magnetoresistance effect element10preferably does not dissipate the spin propagated from the spin-orbit torque wiring20. For example, silver, copper, magnesium, and aluminum and the like have a long spin diffusion length of at least 100 nm, and are known to be resistant to spin dissipation.

The thickness of this layer is preferably not more than the spin diffusion length of the material used for forming the layer. Provided the thickness of the layer is not more than the spin diffusion length, the spin propagated from the spin-orbit torque wiring20can be transmitted satisfactorily to the magnetoresistance effect element10.

<Spin-Orbit Torque Wiring>

The spin-orbit torque wiring20extends along the x-direction. The spin-orbit torque wiring20is connected to one surface of the second ferromagnetic metal layer 2 in the z-direction. The spin-orbit torque wiring20may be connected directly to the second ferromagnetic metal layer 2, or connected via another layer.

The spin-orbit torque wiring20is formed from a material that generates a pure spin current by the spin Hall effect when a current flows through the material. This material may have any composition capable of generating a pure spin current in the spin-orbit torque wiring20. Accordingly, the material is not limited to materials formed from simple elements, and may also be composed of a portion formed from a material that generates a pure spin current and a portion formed from a material that does not generate a pure spin current.

The spin Hall effect is a phenomenon wherein when an electric current is passed through a material, a pure spin current is induced in a direction orthogonal to the orientation of the electric current as a result of spin-orbit interactions.

FIG.2is a schematic diagram for explaining the spin Hall effect.FIG.2is a cross-sectional view of the spin orbit torque wiring20shown inFIG.1cut along the x-direction. A mechanism by which a pure spin current is generated by the spin Hall effect is described with reference toFIG.2.

As illustrated inFIG.2, when an electric current I flows along the direction which the spin-orbit torque wiring20extends, a first spin S1oriented toward the back of the paper surface and a second spin S2oriented toward the front of the paper surface are bent in directions orthogonal to the current. The normal Hall effect and the spin Hall effect have in common the fact that the direction of travel (movement) of the traveling (moving) electric charge (electrons) is bent, but differ significantly in terms of the fact that in the common Hall effect, charged particles moving through a magnetic field are affected by Lorentz forces, resulting in bending of the travel direction, whereas in the spin Hall effect, despite no magnetic field existing, the travel direction of the spin bends simply under the effect of the movement of the electrons (flow of current).

In a non-magnetic material (a material that is not ferromagnetic), the electron count of the first spin S1and the electron count of the second spin S2are equal, and therefore inFIG.2, the electron count of the first spin S1moved to the upward direction and the electron count of the second spin S2moved to the downward direction are equal. Accordingly, the electric current represented by the net flux of the electric charge is zero. This type of spin current that is accompanied by no electric current is called a pure spin current.

When a current is passed through a ferromagnetic material, the fact that the first spin S1and the second spin S2are bent in opposite directions is the same. However, the difference in a ferromagnetic material is that one of either the first spin S1or the second spin S2is greater, resulting in the occurrence of a net flux for the electric charge (and the generation of a voltage). Accordingly, a material formed solely from a ferromagnetic substance cannot be used as the material for the spin-orbit torque wiring20.

If the electron flow of the first spin S1is represented by J↑, the electron flow of the second spin S2is represented by J↓, and the spin current is represented by JS, then the spin current is defined as JS=J↑−J↓. InFIG.2, the pure spin current JSflows in the upward direction in the figure. Here, JSis an electron flow having 100% polarizability.

InFIG.1, when a ferromagnetic material is brought into contact with the upper surface of the spin-orbit torque wiring20, the pure spin current diffuses and flows into the ferromagnetic material. In other words, spin is injected into the magnetoresistance effect element10.

The spin-orbit torque wiring20may contain a non-magnetic heavy metal. Here, the term “heavy metal” is used to mean a metal having a specific gravity at least as large as that of yttrium. The spin-orbit torque wiring20may also be formed solely from a non-magnetic metal.

In such a case, the non-magnetic metal is preferably a non-magnetic metal with a large atomic number, and specifically a non-magnetic metal with an atomic number of 39 or greater having d-electrons or f-electrons in the outermost shell. The reason for this preference is that such non-magnetic metals exhibit large spin-orbit interactions that generate a spin Hall effect. The spin-orbit torque wiring20may also be formed solely from a non-magnetic metal with a large atomic number, having an atomic number of 39 or greater and having d-electrons or f-electrons in the outermost shell.

Typically, when a current is passed through a metal, all of the electrons move in the opposite direction of the current regardless of spin orientation, but in the case of a non-magnetic metal with a large atomic number having d-electrons or f-electrons in the outermost shell, because the spin-orbit interactions are large, the spin Hall effect greatly acts and the direction of electron movement is dependent on the electron spin orientation, meaning a pure spin current JSdevelops more readily.

Furthermore, the spin-orbit torque wiring20may contain a magnetic metal. The term “magnetic metal” means a ferromagnetic metal or an antiferromagnetic metal. By including a trace amount of a magnetic metal in the non-magnetic metal, the spin-orbit interactions can be amplified, thereby increasing the spin current generation efficiency of the electric current passed through the spin-orbit torque wiring20. The spin-orbit torque wiring20may also be formed solely from an antiferromagnetic metal.

Spin-orbit interactions occur within interior field peculiar to the substance of the spin-orbit torque wiring material. Accordingly, pure spin currents also develop in non-magnetic materials. By adding a trace amount of a magnetic metal to the spin-orbit torque wiring material, because the electron spin of the magnetic metal itself is scattered, the efficiency of spin current generation is enhanced. However, if the amount added of the magnetic metal is too large, then the generated pure spin current tends to be scattered by the added magnetic metal, resulting in a stronger action reducing the spin current. Accordingly, it is preferable that the molar ratio of the added magnetic metal is considerably lower than that of the main component of the pure spin current generation portion in the spin-orbit torque wiring. As a guide, the molar ratio of the added magnetic metal is preferably not more than 3%.

Furthermore, the spin-orbit torque wiring20may contain a topological insulator. The spin-orbit torque wiring20may also be formed solely from a topological insulator. A topological insulator is a substance in which the interior of the substance is an insulator or a high-resistance body, but the surface of the substance forms a metal-like state with spin polarization. This substances have a type of internal magnetic field known as a spin-orbit interaction. Accordingly, even if an external magnetic field does not exist, the effect of these spin-orbit interactions generates a new topological phase. This is a topological insulator, which as a result of strong spin-orbit interactions and the break of inversion symmetry at the edges, is able to generate a pure spin current with good efficiency.

Examples of preferred topological insulators include SnTe, Bi1.5Sb0.5Te1.7Se1.3, TlBiSe2, Bi2Te3, and (Bi1-xSbx)2Te3. These topological insulators can generate spin current with good efficiency.

The spin-orbit torque type magnetoresistance effect element100may also have other structural elements besides the magnetoresistance effect element10and the spin-orbit torque wiring20. For example, the spin-orbit torque type magnetoresistance effect element100may have a substrate or the like as a support. The substrate preferably has superior smoothness, and examples of materials that can be used include Si and AlTiC.

(Principles of Spin-Orbit Torque Type Magnetoresistance Effect Element)

Next, the operating principles of the spin-orbit torque type magnetoresistance effect element100will be explained, together with the specific structure of the magnetoresistance effect element10and the relationship between the magnetoresistance effect element10and the spin-orbit torque wiring20.

As illustrated inFIG.1, when a current I1is applied to the spin-orbit torque wiring20, a pure spin current JS(seeFIG.2) is generated in the z-direction. A magnetoresistance effect element10is provided in the z-direction of the spin-orbit torque wiring20. Due thereto, spin is injected from the spin-orbit torque wiring20into the second ferromagnetic metal layer 2 of the magnetoresistance effect element10. The injected spin applies a spin-orbit torque (SOT) to the magnetization of the second ferromagnetic metal layer 2, causing magnetization reversal.

The magnetization reversal of the magnetoresistance effect element10depends on the amount of injected spin. The amount of spin is determined by the current density Ic1of the electric current I1flowing through the spin-orbit torque wiring20. The current density Ic1of the electric current I1flowing through the spin-orbit torque wiring20is the value of the electric current flowing through the spin-orbit torque wiring20divided by the area of a plane orthogonal to the direction of flow of the electric current. For this reason, inFIG.1, the current density Ic1=I1/WH. In this case, W represents the length (width) of the spin-orbit torque wiring20in the y-direction, and H represents the thickness of the spin-orbit torque wiring20in the z-direction.

The current density Ic1does not include a component along the length L1 of the magnetoresistance effect element in the x-direction, and is determined by the spin-orbit torque wiring20. This is a highly noteworthy fact. In the spin-orbit torque type magnetoresistance effect element100, the amount of current necessary for operation can be set independently of the area (the area when viewed from the z-direction) of the magnetoresistance effect element10.

FIG.3is a schematic view of a spin-transfer torque type magnetoresistance effect element101using STT. The spin-transfer torque type magnetoresistance effect element101comprises a magnetoresistance effect element11, first wiring30and second wiring40. Any kind of conductor may be used for the first wiring30and the second wiring40.

When a potential difference is provided between the first wiring30and the second wiring40, an electric current I2flows in the stacking direction of the magnetoresistance effect element11. The electric current I2generates STT, and the magnetization of the second ferromagnetic metal layer 2 is reversed.

The intensity of the STT is determined by the current density Ica of the electric current I2flowing in the stacking direction of the magnetoresistance effect element11. The current density Ic2of the electric current I2flowing in the stacking direction of the magnetoresistance effect element11is the value of the electric current I2flowing in the stacking direction of the magnetoresistance effect element11divided by the area of a plane orthogonal to the direction of flow of the electric current (the cross-sectional area S of the magnetoresistance effect element11). For this reason, inFIG.3, the current density Ic2=I2/S.

This current density Ic2has the cross-sectional area S of the magnetoresistance effect element11as a parameter. For this reason, the amount of current necessary for the operation of the spin-transfer torque type magnetoresistance effect element101depends on the area (the area when viewed from the z-direction) of the magnetoresistance effect element11.

If the cross-sectional area S of the magnetoresistance effect element11is small, then there is an increased probability that the magnetization of the second ferromagnetic metal layer 2 will be reversed under the influence of thermal disturbances or the like. For this reason, the cross-sectional area S of the magnetoresistance effect element11must be at least a predetermined size in order to ensure the stability of magnetic recording. In other words, in order to operate the spin-transfer torque type magnetoresistance effect element101, a current amount obtained by multiplying the “current density necessary for magnetization reversal” with the “area for which magnetization can be stably maintained” is necessary.

In contrast, in order to operate the spin-orbit torque type magnetoresistance effect element100according to the present embodiment, a current amount obtained by multiplying the “current density necessary for magnetization reversal” with the “cross-sectional area of the spin-orbit torque wiring20” is necessary. The “cross-sectional area of the spin-orbit torque wiring20” can be set to any value. For this reason, in the spin-orbit torque type magnetoresistance effect element100, the total amount of current necessary for operation can be made smaller.

As illustrated inFIG.1, the second ferromagnetic metal layer 2 in the spin-orbit torque type magnetoresistance effect element100has shape anisotropy. The length L1 of the second ferromagnetic metal layer 2 in the x-direction is longer than the length (width) L2 in the y-direction. By configuring the spin-orbit torque type magnetoresistance effect element100in this way, the total amount of current necessary for operation can be made smaller. Herebelow, the reasons therefor will be explained.

FIG.4is a schematic view of a spin-orbit torque type magnetoresistance effect element102when the second ferromagnetic metal layer 2 of the magnetoresistance effect element12does not have shape anisotropy. In the magnetoresistance effect element12illustrated inFIG.4, the length L1′ of the second ferromagnetic metal layer 2 in the x-direction is equal to the length (width) L2′ in the y-direction. In other words, the magnetoresistance effect element12is square-shaped when viewed from the z-direction.

Generally speaking, when introducing elements of limited size into a limited space, elements having higher symmetry can be more efficiently placed. For this reason, in order to raise the level of integration of MRAM, it would be normal to increase the symmetry of the magnetoresistance effect elements. In other words, magnetoresistance effect elements that are highly symmetrical, i.e. square-shaped (seeFIG.4) or circular, when viewed from the z-direction, would be chosen for use as the integrated elements.

In order to operate the spin-orbit torque type magnetoresistance effect element102, an electric current I3obtained by multiplying the “current density Ic3necessary for magnetization reversal” with the “cross-sectional area (W′H) of the spin-orbit torque wiring20” is necessary. In other words, the relation I3=Ic3×W′H is established.

As mentioned above, in order to operate the spin-orbit torque type magnetoresistance effect element100illustrated inFIG.1, an electric current I1obtained by multiplying the “current density Ic1necessary for magnetization reversal” with the “cross-sectional area (WH) of the spin-orbit torque wiring20” is necessary. In other words, the relation I1=Ic1×WH is established.

Since the layer structures of the magnetoresistance effect elements10,12are identical, the current density Ic1and the current density Ic3are about the same. When considering that there is a need to make the areas of magnetoresistance effect elements the same in order to ensure thermal stability, the length L2′ of the magnetoresistance effect element12in the y-direction must be made longer than the length L2, and in conjunction therewith, the width W′ of the spin-orbit torque wiring20in the y-direction must also be made wider. In other words, the width W′ of the spin-orbit torque type magnetoresistance effect element102in the y-direction is wider than the width W of the spin-orbit torque type magnetoresistance effect element100in the y-direction. In other words, the electric current I1that is necessary to operate the spin-orbit torque type magnetoresistance effect element100is lower than the electric current I3that is necessary to operate the spin-orbit torque type magnetoresistance effect element102.

In view of the above, it is preferable for the width W of the magnetoresistance effect element10to be as narrow as possible. However, when considering the state of the art in processing techniques such as photolithography, 7 nm is the limit. Additionally, the thickness H of the spin-orbit torque wiring20is preferably as thin as possible, but the thickness should preferably be at least 10 nm in order to allow a sufficient amount of current to flow.

When the cross-sectional area of the spin-orbit torque wiring20is small, the resistance can be expected to become greater. However, the spin-orbit torque wiring20is metallic and the resistance is not expected to become so large that the operation of the element will be affected. The increase in resistance is trivial in comparison to cases in which the electric current is supplied to a tunnel barrier layer, as in TMR elements in which magnetization reversal is performed by STT.

The resistance value at the portion of the spin-orbit torque wiring20that overlaps with the magnetoresistance effect element10when viewed from the z-direction should preferably be lower than the resistance value of the magnetoresistance effect element10. In this case, the “resistance value of the magnetoresistance effect element10” refers to the resistance value when electric current is supplied in the z-direction of the magnetoresistance effect element. Additionally, when the magnetoresistance effect element is a TMR, most of the resistance in the magnetoresistance effect element10is due to the resistance in the tunnel barrier layer. By setting the resistance values to have such a relationship, it is possible to suppress the flow of the electric current I1that is supplied to the spin-orbit torque wiring20into the magnetoresistance effect element10. In other words, the electric current I1supplied to the spin-orbit torque wiring20can be made to more efficiently contribute to the generation of pure spin current.

Additionally, there is also the advantage that, when the second ferromagnetic metal layer 2 in the magnetoresistance effect element10has shape anisotropy, the magnetization of the second ferromagnetic metal layer is more easily reversed. When the magnetization of the second ferromagnetic metal layer is oriented in the z-direction, magnetization rotation must be triggered in order to rotate the magnetization by SOT. The magnetization rotation may be triggered by applying an external magnetic field or the like. However, if a magnetic field generation source is provided outside the element, the overall size of the spin-orbit torque type magnetoresistance effect element100will become large. Therefore, the magnetization rotation may be triggered, even in an environment lacking a magnetic field, by providing the magnetoresistance effect element with shape anisotropy.

When the second ferromagnetic metal layer 2 in the magnetoresistance effect element10has shape anisotropy, the intensity of the demagnetizing field of the magnetoresistance effect element10will differ between the long-axis direction (direction of length L1) and the short-axis direction (direction of length L2). In other words, there will be a distribution in the intensity of the demagnetizing field.

The demagnetizing field is a reverse-oriented magnetic field that is generated inside a ferromagnetic body by the magnetic poles formed at the ends of a magnetic body. For this reason, the intensity of the demagnetizing field becomes greater as the polarizability of the magnetic poles becomes greater and as the distance between the magnetic poles becomes smaller. In the case of the magnetoresistance effect element10illustrated inFIG.1, the intensity of the demagnetizing field in the short-axis direction (direction of length L2) is greater than the intensity of the demagnetizing field in the long-axis direction (direction of length L1).

The demagnetizing field generates a restoring force that tends to return the magnetization of the second ferromagnetic metal layer to the original state when the magnetization begins to rotate. The restoring force counteracts the magnetization rotation, and as the restoring force becomes greater, it becomes more difficult to rotate the magnetization.

For this reason, the ease of rotation of the magnetization of the second ferromagnetic metal layer 2 differs between the rotation direction along the long-axis direction (hereinafter referred to as the first rotation direction) and the rotation direction along the short-axis direction (hereinafter referred to as the second rotation direction). The intensity of the restoring force that is encountered when rotating the magnetization is greater in the short-axis direction. For this reason, the magnetization is more easily rotated along the first rotation direction than along the second rotation direction. In other words, the first rotation direction is a magnetization-reversal-facilitated direction.

As illustrated inFIG.3, the magnetoresistance effect element12, which is square-shaped in planar view when viewed from the z-direction, does not have a magnetization-reversal-facilitated direction. Additionally, when considering that it is necessary to make the areas of magnetoresistance effect elements the same in order to ensure thermal stability, the length L1 of the magnetoresistance effect element10in the x-direction must be longer than the length L1′ of the magnetoresistance effect element12in the x-direction. In other words, the energy necessary for reversing the magnetization of the magnetoresistance effect element10is less than the energy necessary for reversing the magnetization of the magnetoresistance effect element12.

In this case, the length L1 of the magnetoresistance effect element10in the long-axis direction should preferably be at least 10 nm and not more than 60 nm, and the length L2 in the short-axis direction should preferably be smaller than L1. When the size of the magnetoresistance effect element10is large, magnetic domains are formed inside the second ferromagnetic metal layer 2. When magnetic domains are formed, the stability of the magnetization of the second ferromagnetic metal layer decreases. Additionally, the length of the magnetoresistance effect element10in the long-axis direction is preferably at least twice, more preferably at least four times, the length in the short-axis direction. If the ratio between the lengths of the magnetoresistance effect element10in the long-axis direction and the short-axis direction is within said range, then a sufficient difference is obtained in the restoring force due to the demagnetizing field.

FIG.5is a diagram illustrating the spin-orbit torque type magnetoresistance effect element according to the present embodiment, when viewed from the z-direction.FIG.5(a)corresponds to a diagram illustrating the spin-orbit torque type magnetoresistance effect element100illustrated inFIG.1, when viewed from the z-direction. There are no particular limitations on the shape of the magnetoresistance effect element as long as the length L1 in the x-direction is longer than the length (width) L2 in the y-direction. The shape may be rectangular as in the magnetoresistance effect element10illustrated inFIG.5(a), or elliptical as in the magnetoresistance effect element13illustrated inFIG.5(b).

As in the magnetoresistance effect element14illustrated inFIG.5(c), the configuration may be such that the planar shape when viewed from the z-direction has an inscribed elliptical region E and external regions A on the outside, in the x-direction, of the elliptical region E. By retaining the external regions A, it is possible to make the area of the magnetoresistance effect element14larger. If the area of the magnetoresistance effect element14is made larger, the magnetization stability is increased and magnetization reversals due to thermal disturbances or the like can be avoided.

As in the magnetoresistance effect element15illustrated inFIG.5(d), the long axis of the magnetoresistance effect element10may be inclined by an angle θ with respect to the direction of extension (x-direction) of the spin-orbit torque wiring20.

As mentioned above, the magnetization-reversal-facilitated direction is formed in the long-axis direction of the magnetoresistance effect element10. In other words, in the magnetoresistance effect element15, the magnetization-reversal-facilitated direction has a component in the y-direction.

The spin that is generated in the spin-orbit torque wiring20by the spin Hall effect is aligned with the outer surface of the spin-orbit torque wiring20. In other words, the spin injected from the spin-orbit torque wiring20into the magnetoresistance effect element10is oriented in the y-axis direction. That is, the spin most efficiently contributes to magnetization reversal of magnetization having a component in the y-direction.

In other words, due to the magnetization-reversal-facilitated direction of the magnetoresistance effect element15having a y-direction component, the magnetization can be strongly influenced by SOT acting in the y-direction. That is, the SOT can be made to efficiently act on the magnetization reversal, and the magnetization can be reversed without applying any external forces such as an external magnetic field.

FIG.6is a diagram illustrating the spin-orbit torque type magnetoresistance effect element according to the present embodiment, when viewed from the x-direction.FIG.6(a)corresponds to a diagram illustrating the spin-orbit torque type magnetoresistance effect element100illustrated inFIG.1when viewed from the x-direction. InFIG.6(a), the distance between the end portions of the spin-orbit torque wiring20and the magnetoresistance effect element10in the y-direction is the same at both sides. In other words, the following relationship is established.

The two end portions of the spin-orbit torque wiring20in the y-direction are referred to as the first end portion e1and the second end portion e2. Additionally, the two end portions of the magnetoresistance effect element10in the y-direction are referred to as the third end portion e3and the fourth end portion e4. The third end portion e3is the end portion on the same side as the first end portion e1, and the fourth end portion e4is the end portion on the same side as the second end portion e2. The distance D1 between the first end portion e1and the third end portion e3is equal to the distance D2 between the second end portion e2and the fourth end portion e4.

The distance D1 between the first end portion e1and the third end portion e3and the distance D2 between the second end portion e2and the fourth end portion e4are both greater than zero, and preferably, at least one of the distances is not more than the spin diffusion length of the spin-orbit torque wiring20.

When an electric current is supplied to the spin-orbit torque wiring20, a pure spin current is generated between the first end portion e1and the third end portion e3and between the second end portion e2and the fourth end portion e4. The spin that is generated in these regions can propagate within a distance range that is not more than the spin diffusion length. For this reason, if the distance D1 between the first end portion e1and the third end portion e3and the distance D2 between the second end portion e2and the fourth end portion e4are greater than zero, then the spin generated in these regions can also be used for magnetization rotation. Additionally, if these distances are not more than the spin diffusion length of the spin-orbit torque wiring20, then the generated spin can all be used for magnetization reversal.

Additionally,FIG.6(b)is a diagram illustrating another example of the spin-orbit torque type magnetoresistance effect element according to the present embodiment, when viewed from the x-direction. InFIG.6(b), the distance D1 between the first end portion e1and the third end portion e3is greater than the distance D2 between the second end portion e2and the fourth end portion e4. In other words, the distance D1 between the first end portion e1and the third end portion e3is different from the distance D2 between the second end portion e2and the fourth end portion e4.

The total amount of spin generated between the first end portion e1and the third end portion e3is greater than the total amount of spin generated between the second end portion e2and the fourth end portion e4. If the generated spin is all supplied to the magnetoresistance effect element10, then the amount of spin supplied to the side of the magnetoresistance effect element10having the third end portion e3will be greater than the amount of spin supplied to the side having the fourth end portion e4. In other words, the symmetry in the intensity of the SOT in the y-direction for rotating the magnetization of the magnetoresistance effect element10will be disrupted.

As mentioned above, the spin that is injected from the spin-orbit torque wiring20into the magnetoresistance effect element10is oriented in the y-axis direction. In other words, the spin most efficiently contributes to magnetization reversal having a component in the y-direction. For this reason, if the symmetry in the intensity of the SOT that is applied for the magnetization of the magnetoresistance effect element10in the y-direction is disrupted, then magnetization reversal is made easier. As a result thereof, the SOT acts efficiently for magnetization reversal, and the magnetization can be reversed even without applying an external force such as an external magnetic field.

With the spin-orbit torque type magnetoresistance effect element according to the present embodiment, the total amount of the electric current necessary for operation can be made smaller. For this reason, when integrated elements are connected to a power supply having a predetermined capacity, the electric current can be distributed to a larger number of elements.

Additionally, in the spin-orbit torque type magnetoresistance effect element according to the present embodiment, there is no need to supply electric current in the stacking direction of the magnetoresistance effect element. Thus, the operating life of the magnetoresistance effect element can be made longer.

Additionally, in the spin-orbit torque type magnetoresistance effect element according to the present embodiment, a distribution in the demagnetizing field occurs in conjunction with the shape anisotropy of the magnetoresistance effect element. As a result thereof, a magnetization-reversal-facilitated direction is formed in the magnetoresistance effect element, and the magnetization can be easily reversed.

(Method for Producing Spin-Orbit Torque Type Magnetoresistance Effect Element)

Next, the method for producing the spin-orbit torque type magnetoresistance effect element will be explained.

A spin-orbit torque type magnetoresistance effect element can be obtained by using a film deposition technique such as sputtering and a shape processing technique such as photolithography.

First, spin-orbit torque wiring is fabricated on a substrate forming a support. The metal constituting the spin-orbit torque wiring is deposited by a publicly known film deposition means such as sputtering. Next, a technique such as photolithography is used to process the spin-orbit torque wiring into a predetermined shape. Portions other than the spin-orbit torque wiring are covered by an insulating film such as an oxide film. The exposed surfaces of the spin-orbit torque wiring and the insulating film should preferably be polished by means of chemical-mechanical polishing (CMP).

Next, the magnetoresistance effect element is fabricated. The magnetoresistance effect element can be fabricated using a publicly known film deposition means such as sputtering. If the magnetoresistance effect element is a TMR element, then a tunnel barrier layer can be formed, for example, by first sputtering approximately 0.4 to 2.0 nm of magnesium, aluminum and a metal thin-film that forms divalent cations with multiple non-magnetic elements onto the second ferromagnetic metal layer, causing plasma oxidation or natural oxidation by feeding oxygen, and thereafter performing a heat treatment. The film deposition method may, aside from sputtering, be vapor deposition, laser ablation or MBE.

As the method for forming the magnetoresistance effect element into a predetermined shape, a processing means such as photolithography may be used. First, after forming the magnetoresistance effect element, a resist is applied to the surface of the magnetoresistance effect element on the side opposite from the spin-orbit torque wiring. Next, the resist is cured at a predetermined portion and the unnecessary parts of the resist are removed. The cured portion of the resist forms a protective film on the magnetoresistance effect element. The cured portion of the resist has the same shape as the magnetoresistance effect element that is finally obtained.

Additionally, the surface on which the protective film is formed is processed by a technique such as ion milling or reactive ion etching (RIE). The portion on which the protective film is not formed is removed, resulting in a magnetoresistance effect element of a predetermined shape.

The method for curing the resist in the predetermined shape will be explained in detail.

As a first method, there is a method of sensitizing the resist to light using a mask. For example, a positive resist is used to form a photomask on the portion that is to be cured. By exposing the resist to light through the photomask, the resist can be processed to a predetermined shape.

There is a demand for reducing the element size of magnetoresistance effect elements in order to allow higher integration. For this reason, the size of magnetoresistance effect elements may approach the resolution limit that is possible with light exposure. In this case, as illustrated inFIG.7, multiple photomasks PM that have been processed into rectangular shapes are combined to cure the resist in the predetermined shape. In the current state of the art, one side of one photomask PM may be made as small as approximately a few nm.

FIG.7is a diagram illustrating the correspondence between the shape of a photomask PM and the planar shape of the resulting magnetoresistance effect element13, when viewed from the z-direction. As illustrated inFIG.7(a), even when the shape of one photomask PM is rectangular, the planar shape of the magnetoresistance effect element13becomes elliptical or the like. This is because some of the light that has passed through the photomask PM is scattered and cures the resist. Additionally, in etching processes such as ion milling, etching proceeds more easily in the areas forming corners.

When external regions A are to be formed outside an elliptical region E as illustrated inFIG.5(c), the photomask is shaped as shown inFIG.7(b)andFIG.7(c). The photomask PM1illustrated inFIG.7(b)has a rectangular region Re in which the ellipse can be inscribed, and projecting regions Pr1at the corners Ed of the rectangular region Re. Additionally, the photomask PM2illustrated inFIG.7(c)has a rectangular region Re in which the ellipse can be inscribed, and projecting regions Pr2on the long sides Sd of the rectangular region Re. The rectangular regions Re inFIGS.7(b) and (c)correspond to the photomask illustrated inFIG.7(a).

By providing projecting regions Pr1at the corners Ed as illustrated inFIG.7(b), it is possible to delay the progress in the etching of the corners Ed during the etching process. As a result thereof, external regions A can be formed as illustrated inFIG.5(c). Additionally, by providing projecting regions Pr2on the sides Sd as illustrated inFIG.7(c), the etching rate difference between the sides Sd and the corners Ed during the etching process can be made larger. As a result thereof, external regions A can be formed as shown inFIG.5(c).

As another method, spot exposure can be performed by using light having directionality, such as a laser. For example, a negative resist is used, and light is shone only at the portions that are to be cured, thereby processing the resist into a predetermined shape. In this case as well, even if the shape of the spot that is exposed is rectangular, the resulting shape will be elliptical.

As mentioned above, even if the shape of the photomask PM is rectangular, the shape of the magnetoresistance effect element13will be a shape not having straight edges, such as an ellipse. For this reason, modifications are needed if the planar shape of the magnetoresistance effect element10when viewed from the z-direction is to be made rectangular, as illustrated inFIG.5(a).

When the planar shape of the magnetoresistance effect element10is to be made rectangular when viewed from the z-direction, the magnetoresistance effect element10is processed in two steps. In other words, the process is divided into a first step of processing a stacked body having the first ferromagnetic metal layer, and the non-magnetic layer and the second ferromagnetic metal layer in one direction, and a second step of processing the stacked body, after having been processed in the one direction, in another direction that intersects with the one direction.

FIG.8is a schematic view for explaining the procedure for fabricating a rectangular magnetoresistance effect element. As illustrated inFIG.8(a), a second ferromagnetic metal layer 2, a non-magnetic layer 3 and a first ferromagnetic metal layer 1 are sequentially stacked onto one surface of spin-orbit torque wiring20and an insulator50, resulting in a stacked body.

Next, the resulting stacked body is processed in one direction. Any direction may be chosen as the one direction. For example, it may be the x-direction in which the spin-orbit torque wiring20extends, it may be the y-direction orthogonal to the x-direction, or it may be a direction that is oblique with respect to both the x-direction and the y-direction.

The stacked body may be processed by using a publicly known processing means, such as a method using photolithography, or a method using a laser or the like. The stacked body, after processing, has some length in the one direction, and thus can directly reflect the shape of the photomask or the like. In other words, the stacked body can be processed into a straight line in the x-direction.

Next, the resulting stacked body is processed in another direction. Any direction intersecting with the one direction may be chosen as the other direction. InFIG.8(c), the stacked body is processed in the y-direction that is orthogonal to the x-direction in which the spin-orbit torque wiring20extends.

The processing in the other direction may also be performed using a publicly known processing means, such as a method using photolithography, or a method using a laser or the like. It is also possible to use a photomask or the like having some length in the other direction when processing the stacked body in the other direction, so the shape of the photomask or the like can thus be directly reflected in the shape after processing. In other words, the stacked body can be processed into a straight line in the y-direction.

Thus, by processing the stacked body in two steps, it is possible to make the planar shape of the magnetoresistance effect element10rectangular when viewed from the z-direction.

Additionally, the outer surface of the resulting magnetoresistance effect element may be covered by an insulator. The insulator may be a publicly known insulator such as an oxide film, a nitride film or the like.

A method for fabricating the spin-orbit torque wiring and the magnetoresistance effect element sequentially has been explained to this point. On the other hand, it is also possible to fabricate the spin-orbit torque wiring and the magnetoresistance effect element at the same time.

First, the metal layer constituting the spin-orbit torque wiring and the layers constituting the magnetoresistance effect element are sequentially stacked onto a surface. Next, the spin-orbit torque wiring and the magnetoresistance effect element are processed together by means of photolithography. In a single process, the processing of the spin-orbit torque wiring and the magnetoresistance effect element in a first direction is completed simultaneously. Thereafter, by processing the magnetoresistance effect element in a second direction different from the first direction, a spin-orbit torque type magnetoresistance effect element is obtained.

The present invention is not necessarily limited to the structures and production methods of the spin-orbit torque type magnetoresistance effect element according to the above-described embodiments, and it is possible to make various modifications within a range not departing from the spirit of the present invention.

(Integration Properties of Spin-Orbit Torque Type Magnetoresistance Effect Element)

Next, the integration properties of the spin-orbit torque type magnetoresistance effect element according to the present embodiment will be explained.

<Circuit Structure>

FIG.9andFIG.10are diagrams schematically illustrating integrated circuits in which a plurality of spin-orbit torque type magnetoresistance effect elements100are integrated. The integrated circuit200illustrated inFIG.9and the integrated circuit201illustrated inFIG.10both have only slight current leakage during writing and reading, and the circuits function satisfactorily as elements. In the circuits inFIG.9andFIG.10, the spin-orbit torque wiring20is denoted as resistances21and22.

In the integrated circuit200illustrated inFIG.9and the integrated circuit201illustrated inFIG.10, a read control element110, an element selection control element120and a write control element130are connected to one spin-orbit torque type magnetoresistance effect element100. As these control elements, publicly known transistors or the like, such as FETs (field-effect transistors) are used.

When a read control element110and an element selection control element120are activated (switched to the “ON” state), an electric current can be supplied in the stacking direction of the magnetoresistance effect element10, and changes in the resistance value of the magnetoresistance effect element10can be read. Additionally, when a write control element130and an element selection control element120are activated (switched to the “ON” state), an electric current can be supplied to the spin-orbit torque wiring20, and the magnetization of the second ferromagnetic metal layer 2 in the magnetoresistance effect element10can be reversed (written).

In the integrated circuit200illustrated inFIG.9, the write control elements130span across multiple spin-orbit torque type magnetoresistance effect elements100, and can be provided together on an end portion of the integrated circuit board or the like. In other words, in the integrated circuit200illustrated inFIG.9, the write control elements130do not have much influence on the integration properties of the spin-orbit torque type magnetoresistance effect element100.

Similarly, in the integrated circuit201illustrated inFIG.10, the read control elements110span across multiple spin-orbit torque type magnetoresistance effect elements100, and can be provided together on an end portion of the integrated circuit board or the like. In other words, the read control elements110do not have much influence on the integration properties of the spin-orbit torque type magnetoresistance effect element100.

Therefore, a single unit cell that affects the integration properties of the integrated circuit can be considered to be formed by a single spin-orbit torque type magnetoresistance effect element100and two control elements. The two control elements are the read control element110and the element selection control element120in the integrated circuit200illustrated inFIG.9, and the element selection control element120and the write control element130in the integrated circuit201illustrated inFIG.10.

Conventionally, it was thought that three control elements are necessary for each spin-orbit torque type magnetoresistance effect element100using SOT. However, depending on the arrangement, it is possible to reduce the number of control elements affecting the integration properties to two.

<Consideration of Unit Cell Size>

Next, the size of a single unit cell will be considered. A single unit cell is defined by one spin-orbit torque type magnetoresistance effect element100and two control elements. For this reason, the manner in which these elements are to be arranged is an important problem. Additionally, it is necessary to estimate the element sizes that are necessary for appropriately operating the spin-orbit torque type magnetoresistance effect element100and the two control elements.

Additionally, the respective element sizes necessary for appropriately operating the spin-orbit torque type magnetoresistance effect element100and the two control elements will be estimated.

(Spin-Orbit Torque Type Magnetoresistance Effect Element Size)

In SRAM (Static Random Access Memory) using spin-transfer torque (Hereinafter referred to as “STT-SRAM”), as one example, cylindrical magnetoresistance effect elements having a diameter of 90 nm are used. In this case, the cross-sectional area of a magnetoresistance effect element when viewed from the stacking direction is (90/2)2×π=6361 nm2. Magnetoresistance effect elements having cross-sectional areas of this size can stably retain data for 10 years even when subjected to influences such as thermal disturbances.

The cross-sectional area of a magnetoresistance effect element that is necessary for stably retaining data is also about the same for the spin-orbit torque type magnetoresistance effect element100according to the present embodiment. For this reason, when a magnetoresistance effect element is viewed from the stacking direction, a cross-sectional area of approximately 6300 nm2is necessary. This cross-sectional area corresponds to the value of the “length L1 in the x-direction” multiplied by the “length L2 in the y-direction” inFIG.1.

The length L1 in the x-direction and the length L2 in the y-direction can be set to any value. Currently, the smallest processing size (feature size: F) that is possible in a semiconductor is considered to be 7 nm. For this reason, the length L2 in the y-direction must be, at minimum, 7 nm, in which case the length in the x-direction would be 900 nm. Other values could also be set for the length L1 in the x-direction and the length L2 in the y-direction, as shown in Table 1 below. In all cases, “length L2 in the y-direction”×“length L1 in the x-direction”≈6300 nm2, and data can be stably retained.

On the other hand, in order to allow use as a memory element, the data must be capable of being rewritten.

In order to reverse the magnetization of (rewrite the data in) a magnetoresistance effect element in STT-SRAM, a current amount obtained by multiplying the “cross-sectional area of the magnetoresistance effect element” with the “current density necessary for magnetization reversal” is necessary. For example, if the current amount is 400 μA, then the current density that is necessary for magnetization reversal is 400 μA/6361 nm2=6.2×106A/cm2.

In order to rewrite the data in the spin-orbit torque type magnetoresistance effect element100according to the present embodiment, an electric current value obtained by multiplying the “current density necessary for magnetization reversal” with the “cross-sectional area (WH) of the spin-orbit torque wiring20” is necessary.

Since the cross-sectional areas of the magnetoresistance effect elements are the same, the “current density necessary for magnetization reversal” will not significantly differ from the current density that is necessary for magnetization reversal of the magnetoresistance effect elements in STT-SRAM. In other words, it may be 6.2×106A/cm2.

The “cross-sectional area (WH) of the spin-orbit torque wiring20” is determined as follows. The width W of the spin-orbit torque wiring20must be at least the length L2 of the magnetoresistance effect element10in the y-direction. The thickness H of the spin-orbit torque wiring20must be approximately 10 nm in order to supply enough electric current, although this depends also on the width W of the spin-orbit torque wiring20.

In other words, the minimum electric current that is necessary to rewrite the data in the spin-orbit torque type magnetoresistance effect element100according to the present embodiment is a value obtained by multiplying the “length L2 in the y-direction (=width W of the spin-orbit torque wiring20)” and the “thickness H of the spin-orbit torque wiring20” with the “current density necessary for magnetization reversal”.

Table 1 shows the current amounts that are necessary in the magnetoresistance effect element10for different lengths L1 in the x-direction and lengths L2 in the y-direction. All of the current amounts are values that are well short of the 400 μA that are necessary for magnetization reversal in STT-SRAM having the same level of data retention performance.

TABLE 1Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect ElementSpin-Orbit Torque WiringControl ElementWidth L2ByWidth L1ByCross-ByIntegratedinMinimuminMinimumsectionalReversalFETMinimumCircuity-directionProcessingx-directionProcessingWidthThicknessAreaCurrentWidthProcessingCell Area(nm)Size (n2F)(nm)Size (n1F)(nm)(nm)(nm2)(μA)(nm)Size (n3F)(F2)Example 171F900129F710704.38.682F1056Example 2142F45065F14101408.717.363F544Example 3213F30043F211021013.026.044F368Example 4284F22533F281028017.434.725F288Example 5355F18026F351035021.743.47F232Example 6426F15022F421042026.052.088F200Example 7497F12919F491049030.460.769F176Example 8568F11317F561056034.769.4410F160Example 9639F10015F631063039.178.1212F144Example 107010F9013F701070043.486.813F128Example 117711F8212F771077047.795.4814F136
Size of Control Elements

On the other hand, the electric current necessary for magnetization reversal is controlled by means of the respective control elements. In other words, each control element must have the ability to supply the electric current necessary for magnetization reversal. In other words, the element size necessary for each control element can be estimated from the current amount necessary for magnetization reversal.

FIG.11is a schematic perspective view illustrating a main portion of a control element used in the spin-orbit torque type magnetoresistance effect element according to the present embodiment. Since the same element may be used for the read control element110, the element selection control element120and the write control element130, the element shall be explained herebelow as the control element T. As illustrated inFIG.11, the control element T comprises a source electrode S, a drain electrode D and a channel C.

If the width of the source electrode S, the width of the drain electrode D and the distance between the source electrode S and the drain electrode D are fixed at the minimum processing size F, then a predetermined current amount per unit width Wa that can be supplied between the source electrode S and the drain electrode D can be determined. When the unit width is 1 μm, an example of the predetermined current amount would be 0.5 mA. In this case, if the reversal current that is necessary for magnetization reversal is 4 μA as in Example 1 shown in Table 1, then the width Wc of the control element must be at least 8 μm. Table 1 also shows the widths Wc of the control element that are necessary in other examples.

As mentioned above, it is possible to estimate the respective element sizes that are necessary for appropriately operating a spin-orbit torque type magnetoresistance effect element100and two control elements T. Next, the manner in which one spin-orbit torque type magnetoresistance effect element100and two control elements T are to be arranged will be considered.

Element Arrangement: First Arrangement

FIG.12is a diagram for explaining the cell size necessary for arranging one spin-orbit torque type magnetoresistance effect element and two control elements.

Expressing the size of the spin-orbit torque type magnetoresistance effect element100in terms of the minimum processing size, the length L1 in the x-direction is n1F and the length L2 in the y-direction is n2F. Although n1and n2are designable values, they are correlated as shown in Table 1.

On one hand, the length of one side of a control element T must be 3F in order to be able to accommodate the width of the source electrode, the width of the drain electrode and the channel region between the source electrode and the drain electrode. On the other hand, the length n3F of the other side is determined by the current amount to be supplied to the channel C (see Table 1).

These elements are disposed inside a predetermined region R. The spin-orbit torque type magnetoresistance effect element100and the control elements T do not need to be processed so as to be on the same plane, and they may overlap when viewed from the z-direction. In contrast, the control elements T are arranged in parallel in the y-direction in order to route the wiring or the like.

FIG.13is a schematic perspective view illustrating the element structure of a unit cell when one spin-orbit torque type magnetoresistance effect element and two control elements are arranged in accordance with the arrangement inFIG.12. InFIG.13, an element selection control element120and a write control element130are incorporated as the control elements in a unit cell, and the structure is in accordance with the circuit diagram inFIG.10. As illustrated inFIG.13, the wiring that connects the three control elements is routed without resulting in any short circuits. In other words, it can be seen that the arrangement of the control elements illustrated inFIG.12is also possible when taking the three-dimensional structure into account. It was also confirmed that a three-dimensional structure is possible when following the circuit diagram inFIG.9(not shown in perspective).

As illustrated inFIG.12andFIG.13, a space is needed between adjacent elements that are present on the same plane in order to avoid short circuits between the elements. This space must have a gap of at least the minimum processing size F. In other words, a width of at least 8F is necessary in the y-direction for a unit cell in the integrated circuit.

In the x-direction of the unit cell in the integrated circuit, the size must be at least as large as either the length (n1F) of the spin-orbit torque type magnetoresistance effect element100in the x-direction or the length (n3F) of the control element T in the x-direction. In actual practice, a space (2F) for fabricating a through-via B (seeFIG.12) and a space (1F) for separating adjacent elements are required, so the width must be at least 3F added to either the length (n1F) of the spin-orbit torque type magnetoresistance effect element100in the x-direction or the length (n3F) of the control element T in the x-direction, whichever is greater.

In this case, it is assumed that the size of the through-via B need only be the minimum processing size F in one direction. However, in actual practice, the size that is needed for fabricating a through-via B will differ depending on the manufacturer used. For this reason, if the size that is necessary for fabricating the through-via B is different, then it is necessary to add a value of twice said size in the x-direction. The reason the value must be doubled is because two through-vias are necessary. Additionally, in the y-direction, if a through-via B cannot be overlapped with a control element when viewed from the z-direction, then the size thereof also must be added to 8F.

Although the addition of through-via sizes affects the absolute value of the cell area, the relative relationships are not affected. For this reason, even if calculations are made using hypothetical numerical values, the relative sizes will not change.

As shown in Table 1, in most cases apart from Example 11, the length (n1F) of the spin-orbit torque type magnetoresistance effect element100in the x-direction determines the size necessary in the x-direction for a unit cell in an integrated circuit.

As mentioned above, the cell area necessary for a unit cell in the integrated circuit is 8F×{(n1F or n3F)+3}. In this case, the larger of “n1F or n3F” is chosen. The cell areas that are necessary for different shapes of the magnetoresistance effect element are shown in Table 1.

The cell area becomes larger as the difference between the width L1 (n1F) of the magnetoresistance effect element10in the x-direction and the width (n3F) of the control element T in the x-direction becomes greater. This is because, as illustrated inFIG.12, the dead space DS in which no elements are formed increases. In other words, for the purposes of integration, it is preferable for the difference between the width L1 (n1F) of the magnetoresistance effect element10in the x-direction and the width (n3F) of the control element T in the x-direction to be smaller. As illustrated inFIG.14, the level of integration can be increased by arranging the spin-orbit torque type magnetoresistance effect element100and the control elements T so as to fill in the dead space DS.

Meanwhile, in order to make the reversal current amount smaller, it is preferable to make the width L2 (n2F) of the magnetoresistance effect element10in the y-direction smaller, even if the difference between the width L1 (n2F) of the magnetoresistance effect element10in the x-direction and the width (n3F) of the control element T in the x-direction becomes greater.

Additionally, the results of a similar analysis when assuming the minimum processing size F to be 10 nm are shown in Table 2, and the results of a similar analysis when assuming the minimum processing size F to be 28 nm are shown in Table 3. Similar results were able to be confirmed in Tables 2 and 3.

TABLE 2Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect ElementSpin-Orbit Torque WiringControl ElementWidth L2ByWidth L1ByCross-ByIntegratedinMinimuminMinimumsectionalReversalFETMinimumCircuity-directionProcessingx-directionProcessingWidthThicknessAreaCurrentWidthProcessingCell Area(nm)Size (n2F)(nm)Size (n1F)(nm)(nm)(nm2)(μA)(nm)Size (n3F)(F2)Example 12101F63063F10101006.212.42F528Example 13202F31532F201020012.424.83F280Example 14303F21021F301030018.637.24F192Example 15404F15816F401040024.849.65F152Example 16505F12613F501050031627F128Example 17606F10511F601060037.274.48F112Example 18707F909F701070043.486.89F96

TABLE 3Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect ElementSpin-Orbit Torque WiringControl ElementWidth L2ByWidth L1ByCross-ByIntegratedinMinimuminMinimumsectionalReversalFETMinimumCircuity-directionProcessingx-directionProcessingWidthThicknessAreaCurrentWidthProcessingCell Area(nm)Size (n2F)(nm)Size (n1F)(nm)(nm)(nm2)(μA)(nm)Size (n3F)(F2)Example 19281F2259F281028017.434.72F80Example 20562F1134F561056034.769.43F40Comparative843F753F841084052104.164F56Example 1Comparative1124F563F11210112069138.885F64Example 2Comparative1405F452F14010114087173.67F80Example 3Comparative1686F382F168101680104208.328F88Example 4Comparative1967F322F196101960122243.049F96Example 5

In Comparative Examples 1-5, the width L2 of the magnetoresistance effect element in the y-direction is greater than the width L1 in the x-direction, and a large reversal current amount is necessary for magnetization reversal. Additionally, the width of the cell area of the integrated circuit in the x-direction is dependent on the size of the control elements and the level of integration is made worse.

Element Arrangement: Second Arrangement

In the above-described first arrangement, the control elements are arranged in parallel in the y-direction, but the control elements T may also be arranged in parallel in the x-direction.

FIG.15is a diagram for explaining the cell size necessary for arranging one spin-orbit torque type magnetoresistance effect element and two control elements.FIG.16is a schematic perspective view illustrating the element structure of a unit cell when one spin-orbit torque type magnetoresistance effect element and two control elements are arranged in accordance with the arrangement inFIG.15.

InFIG.16, an element selection control element120and a write control element130are incorporated as the control elements in a unit cell, and the structure is in accordance with the circuit diagram inFIG.10. As illustrated inFIG.16, the wiring that connects the three control elements is routed without resulting in any short circuits. In other words, it can be seen that the arrangement of the control elements illustrated inFIG.16is also possible when taking the three-dimensional structure into account. It was also confirmed that a three-dimensional structure is possible when following the circuit diagram inFIG.9(not shown in perspective).

As illustrated inFIG.15, the sizes of the elements are not different. However, by changing the arrangement, the width in the x-direction that is necessary for providing two control elements changes. The width in the x-direction that is necessary for two control elements is twice the width (3F) of each element in the x-direction, plus the distance (n4F) between the elements. Since the minimum distance between the elements is F, the width in the x-direction that is necessary for the two control elements must be, at minimum, 7F. Additionally, 1F is necessary in order to ensure separation between adjacent unit cells, so at least 8F is necessary.

In other words, when the value (n1F+2F+F) obtained by adding space (2F) for through-vias and space (F) between the cells to the length of the spin-orbit torque type magnetoresistance effect element100in the x-direction is greater than the minimum length (8F) of the control elements T in the x-direction, the size of the former (n1F+2F+F) is necessary in the x-direction for a unit cell in the integrated circuit. Meanwhile, if the value (n1F+2F) obtained by adding the space for two through-vias to the length of the spin-orbit torque type magnetoresistance effect element100in the x-direction is smaller than the minimum length (8F) of the control elements T in the x-direction, the size of the latter (8F) is necessary in the x-direction for a unit cell in the integrated circuit.

On the other hand, in the y-direction of a unit cell in the integrated circuit, the size must be at least either the length (n2F) of the spin-orbit torque type magnetoresistance effect element100in the y-direction or the length (n3F) of a control element T in the y-direction. In actual practice, a space (1F) for separating adjacent elements is required, so the width must be at least F added to either the length (n2F) of the spin-orbit torque type magnetoresistance effect element100in the y-direction or the length (n3F) of a control element T in the y-direction, whichever is greater.

For this reason, the cell area necessary for a unit cell in the integrated circuit is {(n1F+2F+F) or 8F}×{(n2F+F) or (n3F+F)}. The “or” in the cell area measurement calculation indicates that the larger of the two values is chosen.

The cell areas that are necessary for different shapes of the magnetoresistance effect element, when the minimum processing size F is assumed to be 7 nm, are shown in Table 4. The cell areas that are necessary for different shapes of the magnetoresistance effect element, when the minimum processing size F is assumed to be 10 nm, are shown in Table 5. The cell areas that are necessary for different shapes of the magnetoresistance effect element, when the minimum processing size F is assumed to be 28 nm, are shown in Table 6. Since the sizes of the elements are unchanged, the values other than the cell sizes of the integrated circuits match with those in Tables 1 to 3.

TABLE 4Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect ElementSpin-Orbit Torque WiringControl ElementWidth L2ByWidth L1ByCross-ByIntegratedinMinimuminMinimumsectionalReversalFETMinimumCircuity-directionProcessingx-directionProcessingWidthThicknessAreaCurrentWidthProcessingCell Area(nm)Size (n2F)(nm)Size (n1F)(nm)(nm)(nm2)(μA)(nm)Size (n3F)(F2)Example 2171F900129F710704.38.682F396Example 22142F45065F14101408.717.363F272Example 23213F30043F211021013.026.044F230Example 24284F22533F281028017.434.725F216Example 25355F18026F351035021.743.47F232Example 26426F15022F421042026.052.088F225Example 27497F12919F491049030.460.769F220Example 28568F11317F561056034.769.4410F220Example 29639F10015F631063039.178.1212F234Example 307010F9013F701070043.486.813F224Example 317711F8212F771077047.795.4814F225

TABLE 5Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect ElementSpin-Orbit Torque WiringControl ElementWidth L2ByWidth L1ByCross-ByIntegratedinMinimuminMinimumsectionalReversalFETMinimumCircuity-directionProcessingx-directionProcessingWidthThicknessAreaCurrentWidthProcessingCell Area(nm)Size (n2F)(nm)Size (n1F)(nm)(nm)(nm2)(μA)(nm)Size (n3F)(F2)Example 32101F63063F10101006.212.42F198Example 33202F31532F201020012.424.83F140Example 34303F21021F301030018.637.24F120Example 35404F15816F401040024.849.65F114Example 36505F12613F501050031627F128Example 37606F10511F601060037.274.48F126Example 38707F909F701070043.486.89F120

TABLE 6Spin-Orbit Torque Type Magnetoresistance Effect ElementMagnetoresistance Effect ElementSpin-Orbit Torque WiringControl ElementWidth L2ByWidth L1ByCross-ByIntegratedinMinimuminMinimumsectionalReversalFETMinimumCircuity-directionProcessingx-directionProcessingWidthThicknessAreaCurrentWidthProcessingCell Area(nm)Size (n2F)(nm)Size (n1F)(nm)(nm)(nm2)(μA)(nm)Size (n3F)(F2)Example 39281F2259F281028017.434.72F36Example 40562F1134F561056034.769.43F32Comparative843F753F841084052104.164F40Example 6Comparative1124F563F11210112069138.885F48Example 7Comparative1405F452F14010114087173.67F64Example 8Comparative1686F382F168101680104208.328F72Example 9Comparative1967F322F196101960122243.049F80Example 10

REFERENCE SIGNS LIST

1First ferromagnetic metal layer2Second ferromagnetic metal layer3Non-magnetic layer11,12,13,14,15Magnetoresistance effect element20Spin-orbit torque wiring30First wiring40Second wiring50Insulator100,102Spin-orbit torque type magnetoresistance effect element101Spin-transfer torque type magnetoresistance effect element110Read control element120Element selection control element130Write control elementT Control elementS Source electrodeD Drain electrodeC Channele1First end portione2Second end portione3Third end portione4Fourth end portionS1First spinS2Second spinI Electric currentJs Pure spin currentPM Photomask