Magnetic memory device

Abstract

To provide a magnetic memory device enabling the characteristics of a memory cell to be improved.SOLUTION: A magnetic memory device 1 according to an embodiment comprises: a first ferromagnetic layer 34 having a fixed magnetization direction; a second ferromagnetic layer 36 having a variable magnetization direction; a first non-magnetic layer 35 provided between the first ferromagnetic layer 34 and the second ferromagnetic layer 36; and a second non-magnetic layer 37 provided on the side of the second ferromagnetic layer 36 opposite to the side on which the first non-magnetic layer 35. At least one of the first non-magnetic layer 35 and the second non-magnetic layer 37 is an oxide layer including magnesium (Mg) and a Group 4 element. The Group 4 element includes at least one element selected from the group consisting of zirconium (Zr), hafnium (Hf) and rutherfordium (Rf).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present invention relates to a magnetic storage device. [Background technology]

[0002] 2. Description of the Related Art Magnetic memory devices using magnetoresistive elements as memory elements (Magnetoresistive Random Access Memories (MRAMs)) are known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2019 / 0173001 [Patent Document 2] US Patent Application Publication No. 2016 / 0380185 [Patent Document 3] US Patent Application Publication No. 2017 / 0069687 [Patent Document 4] US Patent Application Publication No. 2018 / 0090671 Summary of the Invention [Problem to be solved by the invention]

[0004] A magnetic memory device capable of improving the characteristics of a memory cell is provided. [Means for solving the problem]

[0005] The magnetic memory device according to the embodiment includes a first ferromagnetic layer having a fixed magnetization direction, a second ferromagnetic layer having a variable magnetization direction, a first nonmagnetic layer provided between the first and second ferromagnetic layers, and a second nonmagnetic layer provided on the opposite side of the second ferromagnetic layer to the side on which the first nonmagnetic layer is provided. At least one of the first and second nonmagnetic layers is an oxide layer containing magnesium (Mg) and a Group 4 element. The Group 4 element includes at least one element selected from the group consisting of zirconium (Zr), hafnium (Hf), and rutherfordium (Rf). [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a memory system including a magnetic memory device according to the embodiment. [Diagram 2] FIG. 2 is a circuit diagram showing an example of a circuit configuration of a memory cell array included in the magnetic memory device according to the embodiment. [Diagram 3] FIG. 3 is a perspective view showing an example of the structure of a memory cell array included in the magnetic memory device according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the cross-sectional structure of a variable resistance element included in a memory cell of the magnetic memory device according to the embodiment. [Diagram 5] FIG. 5 is a perspective view showing a unit lattice of a crystal structure of an example of a material used in the nonmagnetic layer included in the variable resistance element of the magnetic memory device according to the embodiment. [Figure 6] FIG. 6 is a perspective view showing a unit lattice of a crystal structure of an example of a material used in the ferromagnetic layer included in the variable resistance element of the magnetic memory device according to the embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing an example of an interface between a nonmagnetic layer and a ferromagnetic layer when the nonmagnetic layer and the ferromagnetic layer are stacked together and included in the variable resistance element of the magnetic memory device according to the embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing another example of the interface between the nonmagnetic layer and the ferromagnetic layer when the nonmagnetic layer and the ferromagnetic layer included in the variable resistance element of the magnetic memory device according to the embodiment are stacked. [Figure 9] FIG. 9 is a perspective view showing a unit cell of the crystal structure of magnesium oxide. [Figure 10] FIG. 10 is a cross-sectional view showing an example of an interface between a nonmagnetic layer containing magnesium oxide and a ferromagnetic layer when the nonmagnetic layer and the ferromagnetic layer are laminated together. [Figure 11] FIG. 11 is a diagram showing an example of characteristics based on differences in the tunnel barrier layer and the cap layer included in the variable resistance element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, the embodiments will be described with reference to the drawings. The drawings are schematic or conceptual. The dimensions and ratios of each drawing are not necessarily the same as those in reality. In the following description, components having substantially the same functions and configurations are given the same reference symbols. Numbers following letters constituting the reference symbols are used to distinguish between elements that are referred to by the reference symbols containing the same letters and have similar configurations. When it is not necessary to distinguish between elements indicated by reference symbols containing the same letters, these elements are referred to by reference symbols containing only letters.

[0008] 1. Embodiment A magnetic storage device according to an embodiment will be described.

[0009] 1.1 Configuration 1.1.1 Memory System Configuration First, an example of the configuration of a memory system including a magnetic memory device will be described with reference to Fig. 1. Fig. 1 is a block diagram showing an example of the configuration of a memory system including a magnetic memory device according to an embodiment.

[0010] 1, the memory system MS includes a magnetic memory device 1 and a memory controller 2. The magnetic memory device 1 operates under the control of the memory controller 2. In response to a request (command) from an external host device, the memory controller 2 can instruct the magnetic memory device 1 to execute a read operation, a write operation, and the like.

[0011] The magnetic memory device 1 is a memory device that uses MTJ (Magnetic Tunnel Junction) elements in memory cells, and is a type of variable resistance memory. The MTJ elements utilize the magnetoresistance effect caused by a magnetic tunnel junction. The MTJ elements are also called magnetoresistance effect elements. The magnetic memory device 1 includes, for example, a memory cell array 11, an input / output circuit 12, a control circuit 13, a row selection circuit 14, a column selection circuit 15, a write circuit 16, and a read circuit 17.

[0012] The memory cell array 11 includes a plurality of memory cells MC, a plurality of word lines WL, and a plurality of bit lines BL. FIG. 1 shows a set of memory cells MC, word lines WL, and bit lines BL. The memory cells MC can store data in a non-volatile manner. The memory cells MC are connected between one word line WL and one bit line BL, and correspond to a set of a row and a column. A row address is assigned to the word line WL. A column address is assigned to the bit line BL. One or more memory cells MC can be specified by selecting one row and selecting one or more columns.

[0013] The input / output circuit 12 is connected to the memory controller 2 and controls communication between the magnetic memory device 1 and the memory controller 2. The input / output circuit 12 transfers a control signal CNT and a command CMD received from the memory controller 2 to a control circuit 13. The input / output circuit 12 transfers a row address and a column address included in an address signal ADD received from the memory controller 2 to a row selection circuit 14 and a column selection circuit 15, respectively. The input / output circuit 12 transfers data DAT (write data) received from the memory controller 2 to a write circuit 16. The input / output circuit 12 transfers data DAT (read data) received from a read circuit 17 to the memory controller 2.

[0014] The control circuit 13 controls the overall operation of the magnetic memory device 1. For example, the control circuit 13 executes a read operation, a write operation, etc., based on the control indicated by the control signal CNT and the command CMD. For example, the control circuit 13 supplies a voltage used for writing data to the write circuit 16 in a write operation. Also, the control circuit 13 supplies a voltage used for reading data to the read circuit 17 in a read operation.

[0015] The row selection circuit 14 is connected to a plurality of word lines WL. The row selection circuit 14 selects one word line WL specified by a row address. The selected word line WL is electrically connected to, for example, a driver circuit (not shown).

[0016] The column selection circuit 15 is connected to a plurality of bit lines BL. The column selection circuit 15 selects one or a plurality of bit lines BL specified by a column address. The selected bit line BL is electrically connected to, for example, a driver circuit (not shown).

[0017] The write circuit 16 supplies a voltage used for writing data to the column selection circuit 15, based on the control of the control circuit 13 and the data DAT (write data) received from the input / output circuit 12. When a current based on the write data flows through the memory cell MC, the desired data is written to the memory cell MC.

[0018] The read circuit 17 includes a sense amplifier. Based on the control of the control circuit 13, the read circuit 17 supplies a voltage used for reading data to the column selection circuit 15. Then, the sense amplifier judges the data stored in the memory cell MC based on the voltage or current of the selected bit line BL. Then, the read circuit 17 transfers data DAT (read data) corresponding to the judgment result to the input / output circuit 12.

[0019] 1.1.2 Memory cell array configuration Next, an example of the circuit configuration of the memory cell array 11 will be described with reference to Fig. 2. Fig. 2 is a circuit diagram showing an example of the circuit configuration of the memory cell array 11 included in the magnetic memory device 1 according to the embodiment. Fig. 2 shows word lines WL0 and WL1 of the multiple word lines WL, and bit lines BL0 and BL1 of the multiple bit lines BL.

[0020] 2, one memory cell MC is connected between a word line WL0 and a bit line BL0, between a word line WL0 and a bit line BL1, between a word line WL1 and a bit line BL0, and between a word line WL1 and a bit line BL1. In the memory cell array 11, the memory cells MC are arranged, for example, in a matrix.

[0021] Each memory cell MC includes a variable resistance element VR and a switching element SEL. The variable resistance element VR and the switching element SEL are connected in series between the associated bit line BL and word line WL. For example, one end of the variable resistance element VR is connected to the bit line BL. The other end of the variable resistance element VR is connected to one end of the switching element SEL. The other end of the switching element SEL is connected to the word line WL. Note that the connection relationship between the variable resistance element VR and the switching element SEL between the bit line BL and the word line WL may be reversed.

[0022] In the present embodiment, the following description will be given assuming that the variable resistance element VR is an MTJ element. That is, the description will be given assuming that the variable resistance element VR is an MTJ element. The variable resistance element VR can store data in a non-volatile manner based on its resistance value. For example, a memory cell MC including the variable resistance element VR in a high resistance state stores data "1". A memory cell MC including the variable resistance element VR in a low resistance state stores data "0". The allocation of data associated with the resistance value of the variable resistance element VR may be set to other values. The resistance state of the variable resistance element VR can change depending on the current flowing through the variable resistance element VR.

[0023] The switching element SEL is, for example, a bidirectional diode. The switching element SEL functions as a selector that controls the supply of current to the associated variable resistance element VR. Specifically, the switching element SEL included in a certain memory cell MC is in an off state when the voltage applied to the memory cell MC is lower than the threshold voltage of the switching element SEL, and is in an on state when the voltage is equal to or higher than the threshold voltage of the switching element SEL. The switching element SEL in the off state functions as an insulator with a large resistance value. When the switching element SEL is in the off state, the flow of current between the word line WL and the bit line BL connected to the memory cell MC is suppressed. The switching element SEL in the on state has a smaller resistance value than the switching element SEL in the off state, making it easier for the current to flow. When the switching element SEL is in the on state, the current flows between the word line WL and the bit line BL connected to the memory cell MC. That is, the switching element SEL can switch whether or not to flow a current depending on the magnitude of the voltage applied to the memory cell MC, regardless of the direction in which the current flows. Note that other elements such as a transistor may be used as the switching element SEL.

[0024] 1.1.3 Memory cell array structure An example of the structure of the memory cell array 11 will be described below. In the following description, an xyz orthogonal coordinate system is used. The X direction corresponds to the extension direction of the bit lines BL. The Y direction corresponds to the extension direction of the word lines WL. The Z direction corresponds to the vertical direction with respect to the surface of the semiconductor substrate used to form the magnetic memory device 1. The description "lower" and its derivatives and related words indicate a position of a smaller coordinate on the z axis. The description "upper" and its derivatives and related words indicate a position of a larger coordinate on the z axis. Hatching is appropriately added to the perspective view. Hatching added to the perspective view does not necessarily relate to the material or characteristics of the component to which the hatching is added. In the perspective view and cross-sectional view, illustration of the configuration such as an interlayer insulating film is omitted.

[0025] 1.1.3.1 Three-dimensional structure of memory cell array First, an example of the three-dimensional structure of the memory cell array 11 will be described with reference to Fig. 3. Fig. 3 is a perspective view showing an example of the structure of the memory cell array 11 included in the magnetic memory device 1 according to the embodiment.

[0026] As shown in FIG. 3, the memory cell array 11 includes a plurality of conductor layers 21 and a plurality of conductor layers 22.

[0027] Each of the plurality of conductive layers 21 has a portion extending in the X direction. The plurality of conductive layers 21 are arranged side by side in the Y direction and spaced apart from each other. Each of the conductive layers 21 is used as a bit line BL.

[0028] Each of the plurality of conductive layers 22 has a portion extending in the Y direction. The plurality of conductive layers 22 are arranged side by side in the X direction and spaced apart from each other. Each of the conductive layers 22 is used as a word line WL.

[0029] A wiring layer in which a plurality of conductor layers 22 are provided is provided above a wiring layer in which a plurality of conductor layers 21 are provided. That is, the conductor layer 22 is provided at a distance from the conductor layer 21. One memory cell MC is provided at each of the intersections between the plurality of conductor layers 21 and the plurality of conductor layers 22. In other words, each memory cell MC is provided in a pillar shape between an associated bit line BL and word line WL. In this example, a variable resistance element VR is provided on the conductor layer 21. A switching element SEL is provided on the variable resistance element VR. A conductor layer 22 is provided on the switching element SEL.

[0030] Although the variable resistance element VR is provided below the switching element SEL in the above example, the variable resistance element VR may be provided above the switching element SEL depending on the circuit configuration of the memory cell array 11. Furthermore, although the word line WL is provided above the bit line BL in the above example, the bit line BL may be provided above the word line WL.

[0031] 1.1.3.2 Cross-sectional structure of a variable resistance element Next, the cross-sectional structure of the variable resistance element VR will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view showing an example of the cross-sectional structure of the variable resistance element VR included in the memory cell MC of the magnetic memory device 1 according to the embodiment.

[0032] As shown in Fig. 4, the variable resistance element VR includes, for example, a nonmagnetic layer 31, a ferromagnetic layer 32, a nonmagnetic layer 33, a ferromagnetic layer 34, a nonmagnetic layer 35, a ferromagnetic layer 36, a nonmagnetic layer 37, and a nonmagnetic layer 38. Note that in Fig. 4, the magnetization directions of the magnetic layers are indicated by arrows. The double-headed arrows indicate that the magnetization direction is variable.

[0033] The nonmagnetic layer 31, the ferromagnetic layer 32, the nonmagnetic layer 33, the ferromagnetic layer 34, the nonmagnetic layer 35, the ferromagnetic layer 36, the nonmagnetic layer 37, and the nonmagnetic layer 38 are stacked in this order, for example, from the conductive layer 21 (bit line BL) side toward the conductive layer 22 (word line WL) side. Specifically, the nonmagnetic layer 31 is provided above the conductive layer 21. The ferromagnetic layer 32 is provided on the nonmagnetic layer 31. The nonmagnetic layer 33 is provided on the ferromagnetic layer 32. The ferromagnetic layer 34 is provided on the nonmagnetic layer 33. The nonmagnetic layer 35 is provided on the ferromagnetic layer 34. The ferromagnetic layer 36 is provided on the nonmagnetic layer 35. That is, the nonmagnetic layer 35 is provided between the ferromagnetic layer 34 and the ferromagnetic layer 36. The nonmagnetic layer 37 is provided on the ferromagnetic layer 36. That is, the nonmagnetic layer 37 is provided on the side of the ferromagnetic layer opposite to the side on which the nonmagnetic layer 35 is provided. The nonmagnetic layer is provided on the nonmagnetic layer 37. The conductive layer 22 is provided above the nonmagnetic layer .

[0034] The nonmagnetic layer 31 is a nonmagnetic conductor. The nonmagnetic layer 31 is used as an underlayer UL. The underlayer UL may function as an electrode that improves electrical connectivity with the bit line BL or the word line WL. The nonmagnetic layer 31 includes, for example, a high-melting-point metal. The high-melting-point metal is, for example, a material having a melting point higher than iron (Fe) and cobalt (Co). The high-melting-point metal includes, for example, at least one element selected from the group consisting of zirconium (Zr), hafnium (Hf), tungsten (W), chromium (Cr), molybdenum (Mo), niobium (Nb), titanium (Ti), tantalum (Ta), vanadium (V), ruthenium (Ru), and platinum (Pt).

[0035] The ferromagnetic layer 32 is a ferromagnetic conductor. The ferromagnetic layer 32 has an easy axis of magnetization perpendicular to the film surface. In the example shown in FIG. 4, the magnetization direction of the ferromagnetic layer 32 is toward the ferromagnetic layer 34. The magnitude of the magnetic field required to reverse the magnetization direction of the ferromagnetic layer 32 is, for example, larger than that of the ferromagnetic layer 34. The leakage magnetic field from the ferromagnetic layer 32 reduces the influence of the leakage magnetic field from the ferromagnetic layer 34 on the magnetization direction of the ferromagnetic layer 36. That is, the ferromagnetic layer 32 functions as a shift cancelling layer SCL. The ferromagnetic layer 32 includes at least one element selected from the group consisting of iron (Fe), cobalt (Co), and nickel (Ni). The ferromagnetic layer 32 may also include at least one element selected from the group consisting of platinum (Pt) and palladium (Pd). Specifically, the ferromagnetic layer 32 includes at least one alloy layer selected from, for example, cobalt platinum (CoPt), cobalt nickel (CoNi), and cobalt palladium (CoPd).

[0036] The nonmagnetic layer 33 is a nonmagnetic conductor. The nonmagnetic layer 33 is used as a spacer layer SP (Spacer Layer), and the ferromagnetic layer 32 and the ferromagnetic layer 34 are antiferromagnetically coupled by designing the nonmagnetic layer 33 to have a certain thickness. As a result, the magnetization direction of the ferromagnetic layer 32 is fixed in a direction antiparallel to the magnetization direction of the ferromagnetic layer 34. Such a magnetization coupling structure of the ferromagnetic layer 32 and the ferromagnetic layer 34 via the nonmagnetic layer 33 is called a SAF (Synthetic Anti-Ferromagnetic) structure. The nonmagnetic layer 33 contains at least one element selected from the group consisting of, for example, ruthenium (Ru), osmium (Os), iridium (Ir), vanadium (V), and chromium (Cr).

[0037] The ferromagnetic layer 34 is a ferromagnetic conductor. The ferromagnetic layer 34 has an easy axis perpendicular to the film surface. The magnetization direction of the ferromagnetic layer 34 is fixed to the ferromagnetic layer 32 side or the ferromagnetic layer 36 side. Note that "the magnetization direction of the ferromagnetic layer 34 is fixed to the ferromagnetic layer 32 side or the ferromagnetic layer 36 side" means that the magnetization direction of the ferromagnetic layer 36 is not changed by a torque having a magnitude capable of reversing the magnetization direction of the ferromagnetic layer 36. In other words, when a current (or a voltage) for changing the magnetization direction of the ferromagnetic layer 36 is supplied to the variable resistance element VR, the magnetization direction of the ferromagnetic layer 34 does not change before and after the current (or voltage) is supplied. In the example shown in FIG. 4, the magnetization direction of the ferromagnetic layer 34 is fixed to the ferromagnetic layer 32 side. As a result, the ferromagnetic layer 34 is used as a reference layer RL (Reference Layer) of the MTJ element. The reference layer RL may be called a "pinned layer" or a "fixed layer". The ferromagnetic layer 34 includes at least one element selected from the group consisting of iron (Fe), cobalt (Co), and nickel (Ni). The ferromagnetic layer 34 may also include at least one element selected from the group consisting of boron (B), phosphorus (P), carbon (C), aluminum (Al), silicon (Si), tantalum (Ta), molybdenum (Mo), chromium (Cr), hafnium (Hf), tungsten (W), and titanium (Ti) as an impurity. Specifically, the ferromagnetic layer 34 includes, for example, iron cobalt boron (FeCoB) or iron boride (FeB).

[0038] The nonmagnetic layer 35 is a nonmagnetic insulator. The nonmagnetic layer 35 forms a magnetic tunnel junction together with the ferromagnetic layers 34 and 36. That is, the nonmagnetic layer 35 functions as a tunnel barrier layer TB of the MTJ element. The nonmagnetic layer 35 also functions as a seed material in a crystallization process of the ferromagnetic layers 34 and 36 included in the manufacturing process of the magnetic storage device 1. This seed material corresponds to a material that serves as a nucleus for growing a crystalline film from the interface between the ferromagnetic layers 34 and 36. The nonmagnetic layer 35 is provided between the ferromagnetic layers 34 and 36. The nonmagnetic layer 35 is, for example, a ternary oxide containing magnesium (Mg) and a Group 4 element, or magnesium oxide (MgO). The Group 4 element contained in the nonmagnetic layer 35 includes, for example, at least one element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf), and rutherfordium (Rf). Specifically, the nonmagnetic layer 35 contains, for example, magnesium titanium oxide (MgTiO3), magnesium zirconium oxide (MgZrO3), magnesium hafnium oxide (MgHfO3), or magnesium rutherfordium oxide (MgRfO3). Hereinafter, a ternary oxide containing magnesium (Mg) and a Group 4 element is also referred to as "Mg-XO." X is a Group 4 element.

[0039] The formation energy of the ternary oxide (Mg-XO) is relatively close to that of magnesium oxide (MgO). In addition, the formation energy of magnesium oxide (MgO) is relatively low, so magnesium oxide (MgO) can be formed relatively stably. Therefore, the ternary oxide (Mg-XO) can be formed relatively stably, similar to magnesium oxide (MgO). As a result, when the nonmagnetic layer 35 is formed using the ternary oxide (Mg-XO), the nonmagnetic layer 35 can be formed relatively stably, similar to when the nonmagnetic layer 35 is formed using magnesium oxide (MgO).

[0040] The ternary oxide (Mg-XO) has a narrower band gap than magnesium oxide (MgO), and therefore has a lower RA (resistance multiplied by area) than magnesium oxide (MgO). Therefore, the ternary oxide (Mg-XO) can be made thicker than magnesium oxide (MgO) while maintaining the RA at the same level as magnesium oxide (MgO). As a result, when the nonmagnetic layer 35 is formed using the ternary oxide (Mg-XO), breakdown (dielectric breakdown) of the nonmagnetic layer 35 can be suppressed more than when the nonmagnetic layer 35 is formed using magnesium oxide (MgO).

[0041] The ternary oxide (Mg-XO) has a function of improving the interface perpendicular magnetic anisotropy (iPMA) of the ferromagnetic layer 36. The interface perpendicular magnetic anisotropy is the perpendicular magnetic anisotropy of the magnetic layer that occurs at the interface between a nonmagnetic layer and a magnetic layer with which the nonmagnetic layer is in direct contact. For example, the ternary oxide (Mg-XO) improves the interface perpendicular magnetic anisotropy of the ferromagnetic layer 36 more than magnesium oxide (MgO). As a result, when the nonmagnetic layer 35 is formed using the ternary oxide (Mg-XO), the interface perpendicular magnetic anisotropy of the ferromagnetic layer 36 can be improved more than when the nonmagnetic layer 35 is formed using magnesium oxide (MgO). Details will be described later.

[0042] The ferromagnetic layer 36 is a ferromagnetic conductor. The ferromagnetic layer 36 has an easy axis direction perpendicular to the film surface. The magnetization direction of the ferromagnetic layer 36 is a direction toward either the ferromagnetic layer 34 side or the nonmagnetic layer 37 side. The magnetization direction of the ferromagnetic layer 36 is configured to be easily reversed compared to the ferromagnetic layer 34. The ferromagnetic layer 36 has a variable magnetization direction. This means that the magnetization direction of the ferromagnetic layer 36 can be changed before (before writing) and after (after writing) a write current is passed through the variable resistance element VR. This allows the ferromagnetic layer 36 to be used as a storage layer SL of the MTJ element. The storage layer SL may be called a "free layer". The ferromagnetic layer 36 includes at least one element selected from the group consisting of iron (Fe), cobalt (Co), and nickel (Ni), for example. The ferromagnetic layer 36 may also contain at least one element selected from the group consisting of boron (B), phosphorus (P), carbon (C), aluminum (Al), silicon (Si), tantalum (Ta), molybdenum (Mo), chromium (Cr), hafnium (Hf), tungsten (W), and titanium (Ti) as an impurity. Specifically, the ferromagnetic layer 36 contains, for example, iron cobalt boron (FeCoB) or iron boride (FeB).

[0043] The nonmagnetic layer 37 is a nonmagnetic oxide. The nonmagnetic layer 37 is used as a cap layer Cap for the ferromagnetic layer 36 (memory layer SL). The nonmagnetic layer 37 can have a function of suppressing an increase in the damping constant of the ferromagnetic layer 36 and reducing a write current. The nonmagnetic layer 37 is in contact with the ferromagnetic layer 36. The nonmagnetic layer 37 is, for example, a ternary oxide containing magnesium (Mg) and a Group 4 element, or magnesium oxide (MgO). The Group 4 element contained in the nonmagnetic layer 37 includes, for example, at least one element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf), and rutherfordium (Rf). Specifically, the nonmagnetic layer 37 includes, for example, magnesium titanium oxide (MgTiO3), magnesium zirconium oxide (MgZrO3), magnesium hafnium oxide (MgHfO3), or magnesium rutherfordium oxide (MgRfO3).

[0044] As described above, the ternary oxide (Mg-XO) can be formed relatively stably, similar to magnesium oxide (MgO). Therefore, when the nonmagnetic layer 37 is formed using the ternary oxide (Mg-XO), the nonmagnetic layer 37 can be formed relatively stably, similar to when the nonmagnetic layer 37 is formed using magnesium oxide (MgO).

[0045] As described above, the ternary oxide (Mg-XO) has a lower RA than magnesium oxide (MgO). Therefore, the ternary oxide (Mg-XO) can lower the RA while maintaining the film thickness at the same level as that of magnesium oxide (MgO). That is, the ternary oxide (Mg-XO) can reduce the parasitic resistance while maintaining the film thickness at the same level as that of magnesium oxide (MgO). As a result, when the non-magnetic layer 37 is formed using the ternary oxide (Mg-XO), the write voltage can be reduced more than when the non-magnetic layer 37 is formed using magnesium oxide (MgO). In addition, the reduction in parasitic resistance increases the MR (magnetoresistance ratio), so that the voltage margin is increased when reading the memory cell MC including the variable resistance element VR in the low resistance state and when reading the memory cell MC including the variable resistance element VR in the high resistance state. As a result, when the non-magnetic layer 37 is formed using the ternary oxide (Mg-XO), the read error can be improved more than when the non-magnetic layer 37 is formed using magnesium oxide (MgO).

[0046] As described above, the ternary oxide (Mg-XO) improves the interfacial perpendicular magnetic anisotropy of the ferromagnetic layer 36 more than magnesium oxide (MgO). As a result, when the nonmagnetic layer 37 is formed using the ternary oxide (Mg-XO), the interfacial perpendicular magnetic anisotropy of the ferromagnetic layer 36 can be improved more than when the nonmagnetic layer 37 is formed using magnesium oxide (MgO). Details will be described later.

[0047] Regarding the non-magnetic layers 35 and 37, one of the non-magnetic layers 35 and 37 may be a ternary oxide (Mg-XO), or both of the non-magnetic layers 35 and 37 may be a ternary oxide (Mg-XO).

[0048] The nonmagnetic layer 38 is a nonmagnetic conductor. The nonmagnetic layer 38 is used as a top layer TL. The top layer TL can have, for example, a function as a hard mask or a function as an electrode that improves electrical connectivity with the word line WL or the bit line BL. The nonmagnetic layer 38 includes, for example, at least one element or compound selected from the group consisting of tungsten (W), tantalum (Ta), tantalum nitride (TaN), titanium (Ti), titanium nitride (TiN), ruthenium (Ru), molybdenum (Mo), and hafnium (Hf).

[0049] The variable resistance element VR described above functions as a perpendicular magnetization MTJ element utilizing the TMR (Tunneling Magnetoresistance) effect. The variable resistance element VR can be in either a low resistance state or a high resistance state depending on the relative relationship between the magnetization directions of the ferromagnetic layers 34 and 36. Specifically, the variable resistance element VR is in a high resistance state when the magnetization directions of the reference layer RL and the memory layer SL are in an anti-parallel state (AP (Anti-Parallel) state), and is in a low resistance state when the magnetization directions of the reference layer RL and the memory layer SL are in a parallel state (P (Parallel) state).

[0050] The magnetic memory device 1 can store desired data in the memory cell MC by changing the magnetization direction of the ferromagnetic layer 36 (memory layer SL). Specifically, the magnetic memory device 1 injects spin torque into the memory layer SL and the reference layer RL by passing a write current through the variable resistance element VR, thereby controlling the magnetization direction of the memory layer SL. This type of write method is called a "spin injection write method."

[0051] In this example, the variable resistance element VR is in the AP state when a write current is passed in a direction from the ferromagnetic layer 34 to the ferromagnetic layer 36, and is in the P state when a write current is passed in a direction from the ferromagnetic layer 36 to the ferromagnetic layer 34. The variable resistance element VR is configured so that the magnetization direction of the ferromagnetic layer 34 does not change when a current of a magnitude capable of reversing the magnetization direction of the ferromagnetic layer 36 is passed through the variable resistance element VR. In other words, "the magnetization direction is fixed" means that the magnetization direction does not change due to a current of a magnitude capable of reversing the magnetization direction of the ferromagnetic layer 36.

[0052] The variable resistance element VR may include other layers, and each magnetic layer may be composed of multiple layers. For example, the ferromagnetic layer 34 may be a laminate of multiple layers. The laminate constituting the ferromagnetic layer 34 may have, for example, a layer containing iron cobalt boron (FeCoB) or iron boride (FeB) as an interface layer with the nonmagnetic layer 35, and may have an additional ferromagnetic layer between the interface layer and the nonmagnetic layer 33 via a nonmagnetic conductor.

[0053] 1.2 Interfacial perpendicular magnetic anisotropy Next, the interface perpendicular magnetic anisotropy will be described. The interface perpendicular magnetic anisotropy is generated by, for example, coupling between iron (Fe) atoms or cobalt (Co) atoms contained in the magnetic layer and oxygen (O) atoms contained in the non-magnetic layer in contact with the magnetic layer. Specifically, the interface perpendicular magnetic anisotropy is generated when, for example, the non-magnetic layer 35 contains oxygen (O) atoms and the ferromagnetic layer 36 contains iron (Fe) atoms or cobalt (Co) atoms, or when the ferromagnetic layer 36 contains iron (Fe) atoms or cobalt (Co) atoms and the non-magnetic layer 37 contains oxygen (O) atoms.

[0054] In the following, as an example, the interface perpendicular magnetic anisotropy in the case where a nonmagnetic layer 35 containing a ternary oxide (Mg-XO) and a ferromagnetic layer 36 containing iron cobalt boron (FeCoB) are laminated will be described.

[0055] When iron cobalt boron (FeCoB) is deposited as the ferromagnetic layer 36, the ferromagnetic layer 36 has an amorphous structure. After all layers (layers 31 to 38) are laminated, an annealing process is performed as a crystallization process of the ferromagnetic layer 36. The annealing temperature is, for example, 350° C. The annealing process removes boron (B) from the ferromagnetic layer 36. As a result, iron (Fe) and cobalt (Co) remain in the ferromagnetic layer 36. In reality, boron (B) also remains in the ferromagnetic layer 36, but the amount is relatively small. Therefore, the ferromagnetic layer 36 after the annealing process is considered to have a crystal structure of iron cobalt (FeCo). Therefore, hereinafter, the interface perpendicular magnetic anisotropy when a ternary oxide (Mg-XO) and iron cobalt (FeCo) are laminated will be described.

[0056] (Ternidic oxide structure) The structure of a ternary oxide (Mg-XO) will be described with reference to Fig. 5. Fig. 5 is a perspective view showing a unit lattice of a crystal structure of a ternary oxide (Mg-XO), which is an example of a material used for the nonmagnetic layers 35 and 37 included in the variable resistance element VR of the magnetic memory device 1 according to the embodiment. Fig. 5 shows the crystal structure of MgHfO3 as an example of the crystal structure of a ternary oxide (Mg-XO). Note that the crystal structures of MgTiO3, MgZrO3, and MgRfO3 also have the same structure as the crystal structure shown in Fig. 5.

[0057] The ternary oxide (Mg-XO) has a perovskite structure. The perovskite structure has a cubic unit lattice. In the ternary oxide (Mg-XO), a magnesium (Mg) atom is located at each vertex of the unit lattice, an X atom is located at the center (body center) of the unit lattice, and an oxygen (O) atom is located at the center (face center) of each face of the unit lattice. In the example shown in FIG. 5, a hafnium (Hf) atom is located at the center of the unit lattice. The lattice constant (length of one side of the unit lattice) a_MgXO is, for example, 4.072 Å.

[0058] The top surface of the unit lattice of the ternary oxide (Mg-XO) is expressed as the (001) plane, for example, using Miller indices. A magnesium (Mg) atom is located at each vertex of the (001) plane, and an oxygen (O) atom is located at the center of the (001) plane. Hereinafter, the (001) plane of the unit lattice of the ternary oxide (Mg-XO) and planes equivalent to the (001) plane (e.g., the (100) plane and the (010) plane, etc.) are collectively referred to as the {001} plane group of the unit lattice of the ternary oxide (Mg-XO). In addition, any one of the planes included in the {001} plane group of the unit lattice of the ternary oxide (Mg-XO) is referred to as the "first plane S1".

[0059] The plane passing through the midpoints of the four sides along the vertical direction of the unit lattice of the ternary oxide (Mg-XO) is expressed as the (002) plane, for example, using Miller indices. An X atom is located at the center of the (002) plane, and an oxygen (O) atom is located at the midpoint of each side of the (002) plane. In the example shown in FIG. 5, a hafnium (Hf) atom is located at the center of the (002) plane. Hereinafter, the (002) plane of the unit lattice of the ternary oxide (Mg-XO) and planes equivalent to the (002) plane (e.g., the (200) plane and the (020) plane, etc.) are collectively referred to as the {002} plane group of the unit lattice of the ternary oxide (Mg-XO). In addition, any one of the planes included in the {002} plane group of the unit lattice of the ternary oxide (Mg-XO) is referred to as the "second plane S2".

[0060] In the case of a ternary oxide (Mg-XO), for example, the first surface S1 or the second surface S2 can be the surface.

[0061] (Structure of iron-cobalt) The structure of iron-cobalt (FeCo) will be described with reference to Fig. 6. Fig. 6 is a perspective view showing a unit lattice of a crystal structure of iron-cobalt (FeCo), which is an example of a material used for the ferromagnetic layer 36 included in the variable resistance element VR of the magnetic memory device 1 according to the embodiment.

[0062] Iron cobalt (FeCo) has a body-centered cubic lattice structure. A body-centered cubic lattice structure has a cubic unit cell. In iron cobalt (FeCo), an iron (Fe) atom or a cobalt (Co) atom is located at each vertex and the center (body center) of the unit cell. The lattice constant a_FeCo is, for example, 2.842 Å.

[0063] In the unit lattice of iron cobalt (FeCo), an iron (Fe) atom or a cobalt (Co) atom is located at each vertex of the (001) plane. Hereinafter, the (001) plane of the unit lattice of iron cobalt (FeCo) and planes equivalent to the (001) plane are collectively referred to as the {001} plane group of the unit lattice of iron cobalt (FeCo). In addition, any one plane included in the {001} plane group of the unit lattice of iron cobalt (FeCo) is referred to as the "third plane S3". In iron cobalt (FeCo), for example, the third plane S3 can be the surface.

[0064] (Layered structure of ternary oxide and iron-cobalt) A laminated structure of a ternary oxide (Mg-XO) and iron cobalt (FeCo) will be described. As described above, in the ternary oxide (Mg-XO), for example, the first surface S1 or the second surface S2 can be the surface. In the case of iron cobalt (FeCo), for example, the third surface S3 can be the surface. For this reason, the laminated structure of a ternary oxide (Mg-XO) and iron cobalt (FeCo) includes a structure in which the first surface S1 is the surface of the ternary oxide (Mg-XO), the third surface S3 is the surface of the iron cobalt (FeCo), and the third surface S3 of the iron cobalt (FeCo) is laminated on the first surface S1 of the ternary oxide (Mg-XO) (hereinafter, also referred to as the "first laminated structure"). In addition, there is a structure in which the second surface S2 is a surface of a ternary oxide (Mg-XO), the third surface S3 is a surface of iron-cobalt (FeCo), and the third surface S3 of iron-cobalt (FeCo) is laminated on the second surface S2 of the ternary oxide (Mg-XO) (hereinafter also referred to as the "second laminated structure").

[0065] 7 is a cross-sectional view showing an example of an interface between a nonmagnetic layer 35 and a ferromagnetic layer 36 included in the variable resistance element VR of the magnetic memory device 1 according to the embodiment when the nonmagnetic layer 35 and the ferromagnetic layer 36 are stacked.

[0066] In the first stacked structure, for example, as shown in FIG. 7, a third surface S3 of iron cobalt (FeCo) rotated by 45 degrees is stacked on a first surface S1 of two arranged ternary oxides (Mg-XO). As a result, iron (Fe) atoms or cobalt (Co) atoms are stacked on magnesium (Mg) atoms. Iron (Fe) atoms or cobalt (Co) atoms are stacked on oxygen (O) atoms. In FIG. 7, for ease of understanding, magnesium (Mg) atoms and iron (Fe) atoms or cobalt (Co) atoms are shown shifted, and oxygen (O) atoms and iron (Fe) atoms or cobalt (Co) atoms are shown shifted. The distance d1 between magnesium (Mg) atoms and oxygen (O) atoms in the first stacked structure (hereinafter also referred to as "lattice constant a_MgXOa") is a_MgXO×1 / √2.

[0067] When an iron (Fe) atom or a cobalt (Co) atom is located directly above or below an oxygen (O) atom in the stacking direction (vertical direction), that is, when an iron (Fe) atom or a cobalt (Co) atom overlaps with an oxygen (O) atom in the stacking direction, the bond between the iron (Fe) atom or the cobalt (Co) atom and the oxygen (O) atom becomes the strongest. At this time, the interface perpendicular magnetic anisotropy of the ferromagnetic layer 36 becomes the highest.

[0068] Whether or not iron (Fe) atoms or cobalt (Co) atoms overlap with oxygen (O) atoms in the stacking direction depends on the lattice constant of the crystal structure of the nonmagnetic layer 35 and the lattice constant of the crystal structure of the ferromagnetic layer 36 (in the example of FIG. 7, the lattice constant d1 of the ternary oxide (Mg-XO) and the lattice constant of iron cobalt (FeCo)). When the lattice constants of both layers match, iron (Fe) atoms or cobalt (Co) atoms overlap with oxygen (O) atoms in the stacking direction. On the other hand, when the lattice constants of both layers do not match, that is, when there is a difference (deviation) between the lattice constants of both layers, iron (Fe) atoms or cobalt (Co) atoms do not overlap with oxygen (O) atoms in the stacking direction.

[0069] As an index representing the difference in lattice constant, for example, the lattice mismatch ratio LMR is used. The lattice mismatch ratio LMR is expressed, for example, as the ratio (Δa / a1)×100[%] of the difference Δa between the lattice constant a1 of one material and the lattice constant a2 of the other material to the lattice constant a1 of the one material. The lower the lattice mismatch ratio LMR, the higher the interfacial perpendicular magnetic anisotropy of the ferromagnetic layer 36. The higher the interfacial perpendicular magnetic anisotropy of the ferromagnetic layer 36, the more difficult it is to reverse the magnetization direction of the ferromagnetic layer 36.

[0070] For example, in the case of the first stacked structure, the lattice mismatch ratio LMR is ((d1-a_FeCo) / a_FeCo)×100=((a_MgXOa-a_FeCo) / a_FeCo)×100. The lattice constant a_MgXOa (=a_MgXO×1 / √2=4.072×1 / √2) is larger than the lattice constant a_FeCo (=2.842). When the lattice constant a_MgXOa is larger than the lattice constant a_FeCo, the lattice mismatch ratio LMR is a positive value. In other words, when the lattice mismatch ratio LMR is a positive value, the area of ​​a square consisting of magnesium (Mg) atoms and oxygen (O) atoms of the ternary oxide (Mg-XO) is larger than the area of ​​a square consisting of iron (Fe) atoms or cobalt (Co) atoms of iron cobalt (FeCo). On the other hand, when the lattice constant a_MgXOa is smaller than the lattice constant a_FeCo, the lattice mismatch ratio LMR is a negative value. In other words, when the lattice mismatch ratio LMR is a negative value, the area of ​​a square consisting of magnesium (Mg) atoms and oxygen (O) atoms of the ternary oxide (Mg-XO) is smaller than the area of ​​a square consisting of iron (Fe) atoms or cobalt (Co) atoms of iron-cobalt (FeCo). In this way, since the lattice mismatch ratio LMR is a positive or negative value, the smaller the absolute value of the lattice mismatch ratio LMR, the higher the interface perpendicular magnetic anisotropy of the ferromagnetic layer 36.

[0071] Next, the second stacked structure will be described. Fig. 8 is a cross-sectional view showing another example of the interface between the nonmagnetic layer 35 and the ferromagnetic layer 36 included in the variable resistance element VR of the magnetic memory device 1 according to the embodiment when the nonmagnetic layer 35 and the ferromagnetic layer 36 are stacked.

[0072] In the second stacked structure, for example, as shown in FIG. 8, a third surface S3 of iron cobalt (FeCo) rotated by 45 degrees is stacked on a second surface S2 of a ternary oxide (Mg-XO). As a result, iron (Fe) atoms or cobalt (Co) atoms are stacked on oxygen (O) atoms. In FIG. 8, for ease of understanding, the oxygen (O) atoms are shown shifted from the iron (Fe) atoms or cobalt (Co) atoms. The distance d2 between the oxygen (O) atoms and the oxygen (O) atoms in the second stacked structure (hereinafter also referred to as the "lattice constant a_MgXOb") is a_MgXO×1 / √2.

[0073] For example, in the case of the second stacked structure, the lattice mismatch ratio LMR = ((d2 - a_FeCo) / a_FeCo) x 100 = ((a_MgXOb - a_FeCo) / a_FeCo) x 100. The lattice constant a_MgXOb (= a_MgXO x 1 / √2 = 4.072 x 1 / √2) is larger than the lattice constant a_FeCo (= 2.842).

[0074] Here, the interfacial perpendicular magnetic anisotropy when magnesium oxide (MgO) and iron cobalt (FeCo) are laminated will be described.

[0075] (Magnesium oxide structure) The structure of magnesium oxide (MgO) will be described with reference to Fig. 9. Fig. 9 is a perspective view showing a unit lattice of the crystal structure of magnesium oxide (MgO).

[0076] Magnesium oxide (MgO) has a NaCl type structure. The NaCl type structure has a cubic unit lattice. In magnesium oxide (MgO), magnesium (Mg) atoms are located at each vertex and the center (face center) of each face of the unit lattice, and oxygen (O) atoms are located at the center (body center) of the unit lattice and the midpoint of each side. The lattice constant a_MgO is larger than the lattice constant a_MgXO of the ternary oxide (Mg-XO).

[0077] In the unit lattice of magnesium oxide (MgO), magnesium (Mg) atoms are located at each vertex and center of the (001) plane, and oxygen (O) atoms are located at the midpoints of each side of the (001) plane. Hereinafter, the (001) plane of the unit lattice of magnesium oxide (MgO) and planes equivalent to the (001) plane are collectively referred to as the {001} plane group of the unit lattice of magnesium oxide (MgO). In addition, any one plane included in the {001} plane group of the unit lattice of magnesium oxide (MgO) is referred to as the "fourth plane S4". In magnesium oxide (MgO), for example, the fourth plane S4 can be the surface.

[0078] (Layered structure of magnesium oxide and iron cobalt) A laminated structure of magnesium oxide (MgO) and iron cobalt (FeCo) will be described. As described above, in magnesium oxide (MgO), for example, the fourth surface S4 can be the surface. In iron cobalt (FeCo), for example, the third surface S3 can be the surface. For this reason, the laminated structure of magnesium oxide (MgO) and iron cobalt (FeCo) includes a structure in which the fourth surface S4 is the surface of magnesium oxide (MgO), the third surface S3 is the surface of iron cobalt (FeCo), and the third surface S3 of iron cobalt (FeCo) is laminated on the fourth surface S4 of magnesium oxide (MgO) (hereinafter, also referred to as a "third laminated structure").

[0079] 10 is a cross-sectional view showing an example of an interface between a non-magnetic layer 35 containing magnesium oxide (MgO) and a ferromagnetic layer 36 when the non-magnetic layer 35 and the ferromagnetic layer 36 are laminated together.

[0080] In the third stacked structure, for example, as shown in FIG. 10, a third surface S3 of iron cobalt (FeCo) rotated by 45 degrees is stacked on a fourth surface S4 of magnesium oxide (MgO). As a result, iron (Fe) atoms or cobalt (Co) atoms are stacked on oxygen (O) atoms. In FIG. 10, for ease of understanding, the oxygen (O) atoms are shown shifted from the iron (Fe) atoms or cobalt (Co) atoms. The distance d3 between the oxygen (O) atoms and the oxygen (O) atoms in the third stacked structure (hereinafter also referred to as "lattice constant a_MgO'") is a_MgO×1 / √2.

[0081] As described above, the lattice constant a_MgO is larger than the lattice constant a_MgXO. Therefore, the lattice constant a_MgO' is larger than the lattice constants a_MgXOa and a_MgXOb. Furthermore, the lattice constants a_MgXOa and a_MgXOb are larger than the lattice constant a_FeCo. From the above, the difference between the lattice constant a_MgXOa (a_MgXOb) and the lattice constant a_FeCo is smaller than the difference between the lattice constant a_MgO' and the lattice constant a_FeCo.

[0082] Therefore, the lattice mismatch ratio LMR of the first stacked structure and the lattice mismatch ratio LMR of the second stacked structure are smaller than the lattice mismatch ratio LMR of the third stacked structure, so that the interface perpendicular magnetic anisotropy per coupling between an iron (Fe) atom or a cobalt (Co) atom and an oxygen (O) atom is higher in the ferromagnetic layer 36 in the first stacked structure and the ferromagnetic layer 36 in the second stacked structure than in the ferromagnetic layer 36 in the third stacked structure.

[0083] The number of couplings between iron (Fe) or cobalt (Co) atoms and oxygen (O) atoms in the first stacked structure is half the number of couplings between iron (Fe) or cobalt (Co) atoms and oxygen (O) atoms in the third stacked structure. Therefore, the contribution of the couplings between iron (Fe) or cobalt (Co) atoms and oxygen (O) atoms in the first stacked structure to the interface perpendicular magnetic anisotropy of the ferromagnetic layer 36 is half that in the third stacked structure.

[0084] The number of couplings between iron (Fe) or cobalt (Co) atoms and oxygen (O) atoms in the second stack structure is equal to the number of couplings between iron (Fe) or cobalt (Co) atoms and oxygen (O) atoms in the third stack structure. Therefore, the contribution of the couplings between iron (Fe) or cobalt (Co) atoms and oxygen (O) atoms in the second stack structure to the interface perpendicular magnetic anisotropy of the ferromagnetic layer 36 is the same as in the third stack structure.

[0085] The interface perpendicular magnetic anisotropy when a ferromagnetic layer 36 containing iron cobalt boron (FeCoB) and a non-magnetic layer 37 containing a ternary oxide (Mg-XO) are laminated is similar to that when a non-magnetic layer 35 containing a ternary oxide (Mg-XO) and a ferromagnetic layer 36 containing iron cobalt boron (FeCoB) are laminated. In this case, the laminated structure of the ternary oxide (Mg-XO) and iron cobalt (FeCo) includes a structure in which a first surface S1 of the ternary oxide (Mg-XO) is laminated on a third surface S3 of iron cobalt (FeCo) (hereinafter, also referred to as a "fourth laminated structure"). Also, there is a structure in which a second surface S2 of the ternary oxide (Mg-XO) is laminated on a third surface S3 of iron cobalt (FeCo) (hereinafter, also referred to as a "fifth laminated structure"). The interfacial perpendicular magnetic anisotropy per coupling between an iron (Fe) atom or a cobalt (Co) atom and an oxygen (O) atom is higher in the ferromagnetic layer 36 in the fourth stack structure and in the ferromagnetic layer 36 in the fifth stack structure than in the ferromagnetic layer 36 in the third stack structure, as in the first and second stack structures.

[0086] MgHfO3 has a smaller lattice mismatch ratio (LMR) with FeCo than MgTiO3 and MgZrO3. Therefore, MgHfO3 has a higher interface perpendicular magnetic anisotropy with FeCo due to coupling with FeCo than MgTiO3 and MgZrO3.

[0087] In addition, the formation energy of MgHfO3 is similar to that of MgO. The formation energy of MgHfO3 is lower than that of MgTiO3 and MgZrO3. Therefore, MgHfO3 is easier to form than MgTiO3 and MgZrO3.

[0088] In view of the above, it is more preferable to select hafnium (Hf) as the Group 4 element contained in the nonmagnetic layers 35 and 37, for example.

[0089] 1.3 Comparison of characteristics based on differences in tunnel barrier layer and cap layer Next, characteristics based on the difference between the tunnel barrier layer TB and the cap layer Cap will be described with reference to Fig. 11. Fig. 11 is a diagram showing an example of characteristics based on the difference between the tunnel barrier layer TB and the cap layer Cap included in the variable resistance element VR. Fig. 11 shows first to fifth configuration examples based on this embodiment and a comparative example. The cross-sectional structure of each example in Fig. 11 shows an excerpt of the ferromagnetic layer 34 (reference layer RL), nonmagnetic layer 35 (tunnel barrier layer TB), ferromagnetic layer 36 (memory layer SL), nonmagnetic layer 37 (cap layer Cap), and nonmagnetic layer 38 (top layer TL) of the layer structure corresponding to the variable resistance element VR formed on a silicon substrate.

[0090] The RA of the MTJ element is equal to the sum of the RA of the tunnel barrier layer TB and the RA of the cap layer Cap. The RA of the tunnel barrier layer TB changes due to the magnetoresistance effect. On the other hand, the RA of the cap layer Cap does not change, and therefore becomes a parasitic resistance. In the first to fifth configuration examples and the comparative example, the RA of the tunnel barrier layer TB is designed to have the same value. Therefore, the film thickness of the tunnel barrier layer TB in the second configuration example and the comparative example is approximately the same. The film thickness of the tunnel barrier layer TB in the fourth configuration example and the fifth configuration example is approximately the same, and is thicker than the film thickness of the tunnel barrier layer TB in the second configuration example and the comparative example. The film thickness of the tunnel barrier layer TB in the first configuration example and the third configuration example is approximately the same, and is thicker than the film thickness of the tunnel barrier layer TB in the fourth configuration example and the fifth configuration example. The film thickness and size of each layer other than the tunnel barrier layer TB in the first to fifth configuration examples and the comparative example are approximately the same.

[0091] In addition, in the first to fifth configuration examples and the comparative example in FIG. 11, the film thickness of the cap layer Cap is designed to be equal.

[0092] FIG. 11 also shows the characteristics (interfacial perpendicular magnetic anisotropy iPMA of the memory layer SL, RA of the cap layer Cap, and reliability of the tunnel barrier layer TB) of the first to fifth configuration examples in comparison with the comparative example.

[0093] 11, the reference layer RL and the memory layer SL of the first to fifth configuration examples and the comparative example are made of iron cobalt boron (FeCoB). The top layer TL of the first to fifth configuration examples and the comparative example is made of tungsten (W). The tunnel barrier layer TB and the cap layer Cap of the comparative example are made of magnesium oxide (MgO).

[0094] The first configuration example is different from the comparative example in the tunnel barrier layer TB. Specifically, the tunnel barrier layer TB of the first configuration example is made of a ternary oxide (Mg-XO). The cap layer Cap of the first configuration example is made of magnesium oxide (MgO).

[0095] The second configuration example is different from the first configuration example in the tunnel barrier layer TB and the cap layer Cap. Specifically, the tunnel barrier layer TB of the second configuration example is made of magnesium oxide (MgO). The cap layer Cap of the second configuration example is made of a ternary oxide (Mg-XO).

[0096] The third configuration example is different from the first configuration example in the cap layer Cap. Specifically, the cap layer Cap of the third configuration example is made of a ternary oxide (Mg-XO). The tunnel barrier layer TB of the third configuration example is made of a ternary oxide (Mg-XO).

[0097] The fourth configuration example is different from the first configuration example in the tunnel barrier layer TB. Specifically, the tunnel barrier layer TB of the fourth configuration example has a structure in which magnesium oxide (MgO), a ternary oxide (Mg-XO), and magnesium oxide (MgO) are laminated in this order. The cap layer Cap of the fourth configuration example uses magnesium oxide (MgO).

[0098] The fifth configuration example is different from the fourth configuration example in the cap layer Cap. Specifically, the cap layer Cap of the fifth configuration example uses a ternary oxide (Mg-XO). The tunnel barrier layer TB of the fifth configuration example uses a structure in which magnesium oxide (MgO), a ternary oxide (Mg-XO), and magnesium oxide (MgO) are laminated in this order.

[0099] (Interface perpendicular magnetic anisotropy of memory layer SL) In the first configuration example, the tunnel barrier layer TB includes a ternary oxide (Mg-XO), and the memory layer SL is in contact with the ternary oxide (Mg-XO) of the tunnel barrier layer TB. Here, in the first configuration example, a case is considered in which the ternary oxide (Mg-XO) of the tunnel barrier layer TB and the iron-cobalt (FeCo) of the memory layer SL have the second structure. In this case, the lattice mismatch rate LMR between the tunnel barrier layer TB and the memory layer SL in the first configuration example is lower than the lattice mismatch rate LMR between the tunnel barrier layer TB and the memory layer SL in the comparative example. As a result, the interface perpendicular magnetic anisotropy of the memory layer SL in the first configuration example is higher than the interface perpendicular magnetic anisotropy of the memory layer SL in the comparative example.

[0100] In the second configuration example, the cap layer Cap includes a ternary oxide (Mg-XO), and the memory layer SL is in contact with the ternary oxide (Mg-XO) of the cap layer Cap. Here, in the second configuration example, a case is considered in which the ternary oxide (Mg-XO) of the cap layer Cap and the iron-cobalt (FeCo) of the memory layer SL have a fifth structure. In this case, the lattice mismatch factor LMR between the memory layer SL and the cap layer Cap in the second configuration example is lower than the lattice mismatch factor LMR between the memory layer SL and the cap layer Cap in the comparative example. As a result, the interface perpendicular magnetic anisotropy of the memory layer SL in the second configuration example is higher than the interface perpendicular magnetic anisotropy of the memory layer SL in the comparative example. The interface perpendicular magnetic anisotropy of the memory layer SL in the second configuration example is equivalent to the interface perpendicular magnetic anisotropy of the memory layer SL in the first configuration example.

[0101] In the third configuration example, the tunnel barrier layer TB and the cap layer Cap include a ternary oxide (Mg-XO), and the memory layer SL is in contact with the ternary oxide (Mg-XO) of the tunnel barrier layer TB and the cap layer Cap. Here, in the third configuration example, a case is considered in which the ternary oxide (Mg-XO) of the tunnel barrier layer TB and the iron-cobalt (FeCo) of the memory layer SL have the second structure, and the ternary oxide (Mg-XO) of the cap layer Cap and the iron-cobalt (FeCo) of the memory layer SL have the fifth structure. In this case, the lattice mismatch rate LMR between the tunnel barrier layer TB and the memory layer SL in the third configuration example is lower than the lattice mismatch rate LMR between the tunnel barrier layer TB and the memory layer SL in the comparative example, and the lattice mismatch rate LMR between the memory layer SL and the cap layer Cap in the third configuration example is lower than the lattice mismatch rate LMR between the memory layer SL and the cap layer Cap in the comparative example. As a result, the interfacial perpendicular magnetic anisotropy of the memory layer SL in the third configuration example is higher than that of the memory layer SL in the comparative example. Since the effect of improving the interfacial perpendicular magnetic anisotropy of the memory layer SL can be obtained from both the tunnel barrier layer TB and the cap layer Cap, the interfacial perpendicular magnetic anisotropy of the memory layer SL in the third configuration example is higher than that of the memory layer SL in the first configuration example.

[0102] In the fourth configuration example, the tunnel barrier layer TB includes a ternary oxide (Mg-XO), and the memory layer SL is in contact with the magnesium oxide (MgO) of the tunnel barrier layer TB. Therefore, the lattice mismatch factor LMR between the tunnel barrier layer TB and the memory layer SL in the fourth configuration example is equivalent to the lattice mismatch factor LMR between the tunnel barrier layer TB and the memory layer SL in the comparative example. As a result, the interface perpendicular magnetic anisotropy of the memory layer SL in the fourth configuration example is equivalent to the interface perpendicular magnetic anisotropy of the memory layer SL in the comparative example.

[0103] In the fifth configuration example, the tunnel barrier layer TB includes a ternary oxide (Mg-XO), and the memory layer SL is in contact with the magnesium oxide (MgO) of the tunnel barrier layer TB. The cap layer Cap includes a ternary oxide (Mg-XO), and the memory layer SL is in contact with the ternary oxide (Mg-XO) of the cap layer Cap. Here, in the fifth configuration example, a case is considered in which the ternary oxide (Mg-XO) of the cap layer Cap and the iron-cobalt (FeCo) of the memory layer SL have a fifth structure. In this case, the lattice mismatch rate LMR between the tunnel barrier layer TB and the memory layer SL in the fifth configuration example is equivalent to the lattice mismatch rate LMR between the tunnel barrier layer TB and the memory layer SL in the comparative example, and the lattice mismatch rate LMR between the memory layer SL and the cap layer Cap in the fifth configuration example is lower than the lattice mismatch rate LMR between the memory layer SL and the cap layer Cap in the comparative example. As a result, the interfacial perpendicular magnetic anisotropy of the memory layer SL in the fifth configuration example is higher than that of the memory layer SL in the comparative example. The interfacial perpendicular magnetic anisotropy of the memory layer SL in the fifth configuration example is equivalent to that of the memory layer SL in the first configuration example.

[0104] From the above, the magnitude relationship of the interfacial perpendicular magnetic anisotropy of the memory layer SL in the first to fifth configuration examples is: fourth configuration example<first configuration example=second configuration example=fifth configuration example<third configuration example.

[0105] (RA of Cap layer Cap) In the first configuration example, the cap layer Cap contains magnesium oxide (MgO). Therefore, the RA of the cap layer Cap in the first configuration example is equivalent to the RA of the cap layer Cap in the comparative example. The same is true for the fourth configuration example.

[0106] In the second configuration example, the cap layer Cap contains a ternary oxide (Mg-XO). Therefore, the RA of the cap layer Cap in the second configuration example is lower than the RA of the cap layer Cap in the comparative example. The same is true for the third and fifth configuration examples.

[0107] From the above, the magnitude relationship of RA of the cap layer Cap in the first to fifth configuration examples is: second configuration example=third configuration example=fifth configuration example<first configuration example=fourth configuration example.

[0108] (Reliability of tunnel barrier layer TB) In the first configuration example, the tunnel barrier layer TB includes a ternary oxide (Mg-XO), and the thickness of the tunnel barrier layer TB is thicker than that of the tunnel barrier layer TB in the comparative example. Therefore, the reliability of the tunnel barrier layer TB in the first configuration example is higher than that of the tunnel barrier layer TB in the comparative example. The same is true for the third configuration example.

[0109] In the second configuration example, the tunnel barrier layer TB contains magnesium oxide (MgO) and has a thickness that is approximately the same as that of the tunnel barrier layer TB in the comparative example, so that the reliability of the tunnel barrier layer TB in the second configuration example is equivalent to that of the tunnel barrier layer TB in the comparative example.

[0110] In the fourth configuration example, the tunnel barrier layer TB includes a ternary oxide (Mg-XO), and the thickness of the tunnel barrier layer TB is thicker than that of the tunnel barrier layer TB in the comparative example. Therefore, the reliability of the tunnel barrier layer TB in the fourth configuration example is higher than that of the tunnel barrier layer TB in the comparative example. Also, in the fourth configuration example, the thickness of the tunnel barrier layer TB is thinner than that of the tunnel barrier layer TB in the first configuration example. Therefore, the reliability of the tunnel barrier layer TB in the fourth configuration example is lower than that of the tunnel barrier layer TB in the first configuration example. The same applies to the fifth configuration example.

[0111] From the above, the magnitude relationship of the reliability of the tunnel barrier layer TB in the first to fifth configuration examples is: second configuration example<fourth configuration example=fifth configuration example<first configuration example=third configuration example.

[0112] 1.4 Effects of the embodiment According to the magnetic memory device 1 according to the embodiment described above, the characteristics of the memory cells MC can be improved. The effects of the magnetic memory device 1 according to the embodiment will be described in detail below.

[0113] As the memory cells MC become finer and have a narrower pitch, there is a demand for improving the interfacial perpendicular magnetic anisotropy of the memory layer SL. The interfacial perpendicular magnetic anisotropy of the memory layer SL is highest when the lattice constant of the memory layer SL matches the lattice constant of the non-magnetic layer in contact with the memory layer SL. Therefore, the greater the difference (lattice mismatch rate LMR) between the lattice constant of the memory layer SL and the lattice constant of the non-magnetic layer in contact with the memory layer SL, the lower the interfacial perpendicular magnetic anisotropy of the memory layer SL. The lower the interfacial perpendicular magnetic anisotropy of the memory layer SL, the easier it is for the magnetization direction of the memory layer SL to be reversed. If the magnetization direction of the memory layer SL becomes easier to be reversed, the retention characteristics of the memory cells MC may be reduced, and defects of the memory cells MC may occur.

[0114] In addition, as the memory cells MC become finer and the pitch becomes narrower, there is a demand for reducing the resistance of the memory cells MC by thinning the tunnel barrier layer TB. If the tunnel barrier layer TB is relatively thin, breakdown of the tunnel barrier layer TB may occur, causing defects in the memory cells MC.

[0115] In contrast, in the configuration according to the present embodiment, a ternary oxide (Mg-XO) can be used as the tunnel barrier layer TB or the cap layer Cap. This allows the lattice mismatch factor LMR between the tunnel barrier layer TB and the memory layer SL to be reduced compared to when magnesium oxide (MgO) is used as the tunnel barrier layer TB. Also, the lattice mismatch factor LMR between the memory layer SL and the cap layer Cap can be reduced compared to when magnesium oxide (MgO) is used as the cap layer Cap. Therefore, the interface perpendicular magnetic anisotropy of the memory layer SL is higher compared to when magnesium oxide (MgO) is used as the tunnel barrier layer TB or the cap layer Cap. This allows the retention characteristics of the memory cell MC to be improved, and the occurrence of defects in the memory cell MC to be suppressed.

[0116] In addition, by using a ternary oxide (Mg-XO) as the tunnel barrier layer TB, the film thickness of the tunnel barrier layer TB can be made thicker than that of the tunnel barrier layer TB made of magnesium oxide (MgO) when the same RA is set. This makes it possible to suppress breakdown of the tunnel barrier layer TB. Therefore, it is possible to improve the reliability of the tunnel barrier layer TB and suppress the occurrence of defects in the memory cells MC.

[0117] Furthermore, by using a ternary oxide (Mg-XO) as the cap layer Cap, the RA of the cap layer Cap can be lowered compared to when magnesium oxide (MgO) is used as the cap layer Cap. Since the RA of the cap layer Cap leads to the parasitic resistance of the memory cell MC, the write voltage can be reduced by lowering the RA of the cap layer Cap. In addition, the voltage margin between the low resistance (P state) bit and the high resistance (AP state) bit during reading is increased, thereby suppressing the occurrence of read failures.

[0118] In addition, by using a ternary oxide (Mg-XO) as the tunnel barrier layer TB or the cap layer Cap, the tunnel barrier layer TB or the cap layer Cap can be formed relatively stably, similar to the case where magnesium oxide (MgO) is used as the tunnel barrier layer TB or the cap layer Cap.

[0119] 2. Modifications, etc. As described above, the magnetic memory device 1 of the embodiment comprises a first ferromagnetic layer 34 whose magnetization direction is fixed, a second ferromagnetic layer 36 whose magnetization direction is variable, a first non-magnetic layer 35 provided between the first ferromagnetic layer 34 and the second ferromagnetic layer 36, and a non-magnetic layer 37 provided on the side of the ferromagnetic layer 36 opposite to the side on which the non-magnetic layer 35 is provided. At least one of the first nonmagnetic layer 35 and the second nonmagnetic layer 37 is an oxide layer containing magnesium (Mg) and a Group 4 element. The Group 4 element includes at least one element selected from the group consisting of zirconium (Zr), hafnium (Hf), and rutherfordium (Rf).

[0120] The embodiment is not limited to the above-described embodiment, and various modifications are possible.

[0121] In the embodiment, the magnetic storage device 1 has been described as an example of a magnetic device including an MTJ element (variable resistance element VR), but the present invention is not limited to this. The magnetic device may be other devices that require a magnetic element having interfacial perpendicular magnetic anisotropy, such as a sensor or a medium. The magnetic element may at least use a variable resistance element VR.

[0122] In this specification, "connection" refers to electrical connection and does not exclude the presence of another element between them. Each of the nonmagnetic layers 31, 33, and 38 may be called a "conductor layer." Each of the nonmagnetic layers 35 and 37 may be called an "oxide layer." The elements contained in each layer of the MTJ element can be measured, for example, by using electron energy loss spectroscopy (EELS) using a scanning transmission electron microscope (STEM).

[0123] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0124] 1...magnetic storage device, 2...memory controller, 11...memory cell array, 12...input / output circuit, 13...control circuit, 14...row selection circuit, 15...column selection circuit, 16...write circuit, 17...read circuit, 21, 22...conductive layer, 32, 34, 36...ferromagnetic layer, 31, 33, 35, 37, 38...non-magnetic layer

Claims

1. a first ferromagnetic layer having a fixed magnetization direction; a second ferromagnetic layer having a variable magnetization direction; a first nonmagnetic layer provided between the first ferromagnetic layer and the second ferromagnetic layer; a second nonmagnetic layer provided on the second ferromagnetic layer opposite to the side on which the first nonmagnetic layer is provided; Equipped with At least one of the first nonmagnetic layer and the second nonmagnetic layer is an oxide layer containing magnesium (Mg) and a Group 4 element, The Group 4 element includes at least one element selected from the group consisting of zirconium (Zr), hafnium (Hf), and rutherfordium (Rf); Magnetic storage device.

2. the first nonmagnetic layer is the oxide layer, the oxide layer is in contact with the second ferromagnetic layer; 2. The magnetic storage device according to claim 1.

3. the second nonmagnetic layer is the oxide layer, the oxide layer is in contact with the second ferromagnetic layer; 3. The magnetic storage device according to claim 1.

4. the first nonmagnetic layer is the oxide layer, the oxide layer has a structure in which a first oxide layer, a second oxide layer, and a third oxide layer are laminated in this order; the first oxide layer and the third oxide layer contain magnesium (Mg); The second oxide layer contains magnesium (Mg) and the Group 4 element.

2. The magnetic storage device according to claim 1.

5. The oxide layer has a perovskite structure.

2. The magnetic storage device according to claim 1.

6. a surface of the oxide layer in contact with the second ferromagnetic layer is a first surface in which magnesium (Mg) atoms are located at each vertex and an oxygen (O) atom is located at the center of a unit lattice of a crystal structure of the oxide layer; 6. The magnetic storage device according to claim 5.

7. a surface of the oxide layer in contact with the second ferromagnetic layer is a second face in a unit lattice of a crystal structure of the oxide layer, the second face having an atom of the Group 4 element at its center and oxygen (O) atoms at the midpoints of each side; 6. The magnetic storage device according to claim 5.

8. The band gap of the oxide layer is narrower than the band gap of magnesium oxide (MgO).

2. The magnetic storage device according to claim 1.

9. The second ferromagnetic layer contains at least one element selected from the group consisting of iron (Fe), cobalt (Co), and nickel (Ni); 2. The magnetic storage device according to claim 1.

10. the second ferromagnetic layer includes iron (Fe) and cobalt (Co); the lattice mismatch rate between the oxide layer and the second ferromagnetic layer is lower in absolute value than the lattice mismatch rate between magnesium oxide (MgO) and the second ferromagnetic layer; 2. The magnetic storage device according to claim 1.

11. a first conductive layer extending in a first direction; a second conductive layer extending in a second direction intersecting the first direction and spaced apart from the first conductive layer; a memory cell provided between the first conductive layer and the second conductive layer; Further comprising: the memory cell includes the first ferromagnetic layer, the first nonmagnetic layer, the second ferromagnetic layer, and the second nonmagnetic layer; 2. The magnetic storage device according to claim 1.

12. The memory cell includes a variable resistance element. The magnetic storage device according to claim 11.

13. the variable resistance element is a magnetoresistive effect element; 13. The magnetic storage device according to claim 12.

14. a first ferromagnetic layer having a fixed magnetization direction; a second ferromagnetic layer having a variable magnetization direction; a first nonmagnetic layer provided between the first ferromagnetic layer and the second ferromagnetic layer; a second nonmagnetic layer provided on the second ferromagnetic layer opposite to the side on which the first nonmagnetic layer is provided; Equipped with At least one of the first nonmagnetic layer and the second nonmagnetic layer is an oxide layer containing magnesium (Mg) and titanium (Ti), The oxide layer has a perovskite structure. Magnetic storage device.

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