Magnetic storage device

Abstract

It suppresses the degradation of magnetoresistive elements. [Solution] According to the embodiment, the magnetic memory device includes a magnetoresistive element MTJ. The magnetoresistive element MTJ includes a first ferromagnetic layer SL, a second ferromagnetic layer RL, a third ferromagnetic layer SCL, a first non-magnetic layer TB provided between the first and second ferromagnetic layers, a second non-magnetic layer SP provided between the second and third ferromagnetic layers, a third non-magnetic layer 38a containing at least one element selected from Ir, Pt, Au, Rh, Pd, Ag, Ni, and Cu, a fourth non-magnetic layer 38b containing at least one element selected from Ta, W, Nb, Mo, V, and Cr, and a fifth non-magnetic layer 38c containing at least one of Si and Ge.

Description

Technical Field

[0001] Embodiments of the present invention relate to a magnetic storage device.

Background Art

[0002] A magnetic storage device (MRAM: Magnetoresistive Random Access Memory) using a magnetoresistive element as a storage element is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In one embodiment of the present invention, a magnetic storage device capable of suppressing deterioration in the performance of a magnetoresistive element is provided.

Means for Solving the Problems

[0005] The magnetic memory device according to the embodiment includes a magnetoresistive element. The magnetoresistive element includes a first ferromagnetic layer, a second ferromagnetic layer, a third ferromagnetic layer, a first non-magnetic layer provided between the first and second ferromagnetic layers, a second non-magnetic layer provided between the second and third ferromagnetic layers, a third non-magnetic layer containing at least one element selected from iridium (Ir), platinum (Pt), gold (Au), rhodium (Rh), palladium (Pd), silver (Ag), nickel (Ni), and copper (Cu), a fourth non-magnetic layer containing at least one element selected from tantalum (Ta), tungsten (W), niobium (Nb), molybdenum (Mo), vanadium (V), and chromium (Cr), and a fifth non-magnetic layer containing at least one element of silicon (Si) and germanium (Ge). The second ferromagnetic layer is located between the first ferromagnetic layer and the third ferromagnetic layer. The third ferromagnetic layer is located between the second non-magnetic layer and the third non-magnetic layer. The fourth non-magnetic layer is located between the third non-magnetic layer and the fifth non-magnetic layer. [Brief explanation of the drawing]

[0006] [Figure 1] A block diagram showing an example of the overall configuration of a magnetic storage device according to one embodiment. [Figure 2] A circuit diagram showing an example of the circuit configuration of a memory cell array in a magnetic storage device according to one embodiment. [Figure 3] A perspective view showing an example of the structure of a memory cell array in a magnetic storage device according to one embodiment. [Figure 4] A cross-sectional view showing an example of the cross-sectional configuration of a magnetoresistive element in a magnetic storage device according to one embodiment. [Figure 5] This figure shows an example of comparing the characteristics of magnetoresistive elements based on differences in buffer layers. [Figure 6] A circuit diagram showing an example of the circuit configuration of a memory cell array in a modified magnetic storage device. [Figure 7] A cross-sectional view showing an example of the cross-sectional configuration of a memory cell in a modified magnetic storage device. [Modes for carrying out the invention]

[0007] Embodiments will be described below with reference to the drawings. In the following description, components having the same function and configuration will be given a common reference numeral. When multiple components having a common reference numeral need to be distinguished, a subscript will be added to the common reference numeral to distinguish them. When there is no particular need to distinguish between multiple components, only the common reference numeral will be assigned to those components, and no subscript will be added. Here, the subscript is not limited to subscripts or superscripts, but also includes, for example, lowercase alphabet letters added to the end of the reference numeral, and indices indicating arrangement.

[0008] 1. Embodiment A magnetic storage device according to the embodiment will now be described. The magnetic storage device according to the embodiment includes, for example, a magnetic storage device using a perpendicular magnetization method in which an element having a magnetoresistance effect by a magnetic tunnel junction (MTJ) (hereinafter also referred to as an "MTJ element") is used as a resistive switching element.

[0009] The following description will explain the case where an MTJ element is applied as a resistive switching element. For the sake of clarity, the resistive switching element will be referred to as a magnetoresistive effect element (MTJ) in the description of the embodiment.

[0010] 1.1 Overall Configuration of Magnetic Storage Devices First, an example of the overall configuration of the magnetic storage device 1 will be described with reference to Figure 1. Figure 1 is a block diagram showing an example of the overall configuration of the magnetic storage device 1 according to the embodiment. In the example in Figure 1, some of the connections between each component are shown by arrow lines, but the connections between each component are not limited to these.

[0011] As shown in Figure 1, the magnetic storage device 1 includes a memory cell array 10, a row selection circuit 11, a column selection circuit 12, a decoding circuit 13, a writing circuit 14, a reading circuit 15, a voltage generation circuit 16, an input / output circuit 17, and a control circuit 18.

[0012] The memory cell array 10 includes multiple memory cells MC. Each memory cell MC is associated with a row-column pair. Specifically, memory cell MCs in the same row are connected to the same word line WL, and memory cell MCs in the same column are connected to the same bit line BL.

[0013] The row selection circuit 11 is a circuit that selects row-direction wiring (word lines WL). The row selection circuit 11 is connected to the memory cell array 10 via the word lines WL. The row selection circuit 11 is also connected to the decode circuit 13 and the control circuit 18. The row selection circuit 11 receives the decoding result of address ADD (row address) from the decode circuit 13. Based on the decoding result of address ADD, the row selection circuit 11 sets the corresponding word line WL to a selected state.

[0014] The column selection circuit 12 is a circuit that selects wiring (bit lines BL) in the column direction. The column selection circuit 12 is connected to the memory cell array 10 via the bit lines BL. The column selection circuit 12 is also connected to the decode circuit 13, the write circuit 14, the read circuit 15, and the control circuit 18. The column selection circuit 12 receives the decoding result of address ADD (column address) from the decode circuit 13. Based on the decoding result of address ADD, the column selection circuit 12 sets the corresponding bit line BL to a selected state.

[0015] The decoding circuit 13 is a circuit that decodes the address ADD received from the input / output circuit 17. The decoding circuit 13 is connected to the row selection circuit 11, the column selection circuit 12, the input / output circuit 17, and the control circuit. The address ADD includes the column address and the row address. The decoding circuit 13 transmits the decoding result of address ADD to the row selection circuit 11 and the column selection circuit 12.

[0016] The write circuit 14 is a circuit that writes data DAT to thememory cell MC. The write circuit 14 is connected to the column selection circuit 12, the voltage generation circuit 16, the input / output circuit 17, and the control circuit 18. The write circuit 14 receives the data DAT from the input / output circuit 17. The write circuit 14 supplies a write current (voltage) based on the data DAT to the memory cell MC via the column selection circuit 12. The write circuit 14 includes, for example, a write driver (not shown).

[0017] The read circuit 15 is a circuit that reads data DAT from the memory cell MC. The read circuit 15 is connected to the column selection circuit 12, the voltage generation circuit 16, the input / output circuit 17, and the control circuit 18. The read circuit 15 reads the data DAT from the memory cell MC via the column selection circuit 12. The read circuit 15 transmits the read data DAT to the input / output circuit 17. The read circuit 15 includes, for example, a sense amplifier (not shown).

[0018] The voltage generation circuit 16 is a circuit that generates voltages used for various operations in the magnetic storage device 1 using a power supply voltage provided from outside the magnetic storage device 1 (not shown). The voltage generation circuit 16 is connected to the write circuit 14, the read circuit 15, and the control circuit 18. For example, the voltage generation circuit 16 generates a voltage (current) used for the write operation and supplies it to the write circuit 14. Also, for example, the voltage generation circuit 16 generates a voltage (current) used for the read operation and supplies it to the read circuit 15.

[0019] The input / output circuit 17 is a circuit that performs input and output of control signals CNT, commands CMD, addresses ADD, data DAT, etc., to and from the outside of the magnetic storage device 1. The input / output circuit 17 is connected to the decode circuit 13, the write circuit 14, the read circuit 15, and the control circuit 18. The input / output circuit 17 transmits the address ADD received from outside the magnetic storage device 1 to the decode circuit 13. The input / output circuit 17 transmits the command CMD and control signals CNT received from outside the magnetic storage device 1 to the control circuit 18. The input / output circuit 17 sends and receives various control signals CNT between the outside of the magnetic storage device 1 and the control circuit 18. The input / output circuit 17 transmits the data DAT received from outside the magnetic storage device 1 to the write circuit 14. The input / output circuit 17 transmits the data DAT received from the read circuit 15 to the outside of the magnetic storage device 1.

[0020] The control circuit 18 controls the operation of the row selection circuit 11, column selection circuit 12, decoding circuit 13, writing circuit 14, reading circuit 15, voltage generation circuit 16, and input / output circuit 17 in the magnetic storage device 1 based on the control signal CNT and command CMD. The control circuit 18 also controls the writing and reading operations.

[0021] 1.2 Circuit configuration of memory cell array Next, an example of the circuit configuration of the memory cell array 10 will be described with reference to Figure 2. Figure 2 is a circuit diagram showing an example of the circuit configuration of the memory cell array 10 provided in the magnetic storage device 1 according to this embodiment.

[0022] As shown in Figure 2, the memory cell array 10 is provided with M+1 word lines WL (WL_0, WL_1, ..., and WL_M) and N+1 bit lines BL (BL_0, BL_1, ..., and BL_N). M and N are each positive integers.

[0023] Each memory cell MC includes a magnetoresistive element MTJ and a switching element SE. The magnetoresistive element MTJ and the switching element SE are connected in series between the associated bit line BL and word line WL. For example, one end of the magnetoresistive element MTJ is connected to the bit line BL. The other end of the magnetoresistive element MTJ is connected to one end of the switching element SE. The other end of the switching element SE is connected to the word line WL. Note that the connection relationship between the magnetoresistive element MTJ and the switching element SE between the bit line BL and the word line WL may be reversed.

[0024] A magnetoresistive element (MTJ) corresponds to an MTJ element. A magnetoresistive element (MTJ) can store data non-volatilely based on its resistance value. For example, a memory cell (MC) containing a magnetoresistive element (MTJ) in a high-resistance state stores "1" data. A memory cell (MC) containing a magnetoresistive element (MTJ) in a low-resistance state stores "0" data. The assignment of data associated with the resistance value of a magnetoresistive element (MTJ) may be other settings. The resistance state of a magnetoresistive element (MTJ) may change depending on the current flowing through the magnetoresistive element (MTJ).

[0025] The switching element SE functions as a switch that controls the supply of current to the corresponding magnetoresistive element MTJ during writing and reading operations to the MTJ. More specifically, for example, the switching element SE in a memory cell MC acts as a high-resistance insulator, blocking the current (turning off) when the voltage applied to the memory cell MC is below a preset threshold voltage. On the other hand, the switching element SE acts as a low-resistance conductor, allowing current to flow (turning on) when the voltage applied to the memory cell MC is above the threshold voltage. In other words, the switching element SE has the function of switching whether to allow or block current flow depending on the magnitude of the voltage applied to the memory cell MC, regardless of the direction of the flowing current.

[0026] The switching element SE may be, for example, a two-terminal switching element. When the voltage applied between the two terminals is below the threshold voltage, the switching element SE is in a high-resistance state where almost no electricity flows, or in a non-conductive state. When the voltage applied between the two terminals is above the threshold voltage, the switching element SE is in a low-resistance state, i.e., electrically conductive. The switching element SE can have this function regardless of the polarity of the voltage. Note that other elements such as transistors may be used as the switching element SE.

[0027] 1.3 Structure of a memory cell array Next, an example of the structure of a memory cell array will be described with reference to Figure 3. Figure 3 is a perspective view showing an example of the structure of a memory cell array 10 provided in a magnetic storage device 1 according to this embodiment.

[0028] The following explanation uses the xyz Cartesian coordinate system. The X direction corresponds to the extension direction of the word line WL. The Y direction intersects the X direction and corresponds to the extension direction of the bit line BL. The Z direction intersects both the X and Y directions.

[0029] As shown in Figure 3, the memory cell array 10 includes a plurality of wiring layers 21 and a plurality of wiring layers 22.

[0030] The wiring layer 21 has a portion that extends in the X direction. Multiple wiring layers 21 are arranged side by side in the Y direction and spaced apart from one another. Each wiring layer 21 functions as a word line WL.

[0031] The wiring layer 22 has a portion that extends in the Y direction. Multiple wiring layers 22 are provided above multiple wiring layers 21 in the Z direction. Multiple wiring layers 22 are provided side by side in the X direction and are spaced apart from each other. Each wiring layer 22 functions as a bit line BL.

[0032] In a top view from the Z direction, one memory cell MC is provided at each intersection of multiple wiring layers 21 and multiple wiring layers 22. In other words, each memory cell MC is provided in a columnar shape between the associated bit line BL and word line WL. In this example, a switching element SE is provided on the wiring layer 21. A magnetoresistive element MTJ is provided on the switching element SE. A wiring layer 22 is provided on the magnetoresistive element MTJ.

[0033] In the example shown in Figure 3, the magnetoresistive element MTJ is provided on top of the switching element SE, but the switching element SE may be provided on top of the magnetoresistive element MTJ. In the example shown in Figure 3, the bit line BL is provided above the word line WL, but the word line WL may be provided above the bit line BL. Furthermore, a structure in which two or more memory cells MC are stacked in the Z direction via the bit line BL or the word line WL may also be possible.

[0034] 1.4 Cross-sectional structure of magnetoresistive element Next, an example of the cross-sectional structure of a magnetoresistive element MTJ will be described with reference to Figure 4. Figure 4 is a cross-sectional view showing an example of the cross-sectional configuration of a magnetoresistive element MTJ provided in the magnetic memory device 1 according to this embodiment.

[0035] As shown in Figure 4, the magnetoresistive element MTJ includes a non-magnetic layer 31, a non-magnetic layer 32, a ferromagnetic layer 33, a non-magnetic layer 34, a laminate 35, a non-magnetic layer 36, a ferromagnetic layer 37, and a laminate 38. The non-magnetic layer 31 functions, for example, as a top layer. The non-magnetic layer 32 functions as a capping layer. The ferromagnetic layer 33 functions as a storage layer. The non-magnetic layer 34 functions as a tunnel barrier layer. The laminate 35 functions as a reference layer. The non-magnetic layer 36 functions as a spacer layer. The ferromagnetic layer 37 functions as a shift cancelling layer. The laminate 38 functions as a buffer layer. Each of the storage layer SL, reference layer RL, and shift cancelling layer SCL can be considered as a ferromagnetic structure as a whole. The buffer layer (BUF) can be considered as a non-magnetic structure as a whole.

[0036] For example, the laminate 38, ferromagnetic layer 37, non-magnetic layer 36, laminate 35, non-magnetic layer 34, ferromagnetic layer 33, non-magnetic layer 32, and non-magnetic layer 31 are stacked in order from the word line WL side toward the bit line BL side (in the Z direction). For example, the magnetization direction of the magnetic material constituting the magnetoresistive element MTJ is perpendicular to the respective film surface. Therefore, the magnetoresistive element MTJ functions as a perpendicular magnetization type MTJ element. Note that the magnetoresistive element MTJ may include further layers (not shown) between each of the above-mentioned layers 31 to 38.

[0037] The non-magnetic layer 31 is a non-magnetic conductor and functions as a top electrode to improve the electrical connectivity between the upper end of the magnetoresistive element MTJ and the bit line BL or word line WL. The non-magnetic layer 31 includes, for example, at least one element or compound selected from tungsten (W), tantalum (Ta), tantalum nitride (TaN), titanium (Ti), and titanium nitride (TiN).

[0038] The non-magnetic layer 32 is a non-magnetic layer that suppresses the increase in the damping constant of the ferromagnetic layer 33 and has the function of reducing the writing current. The non-magnetic layer 32 includes, for example, magnesium oxide (MgO), aluminum oxide (AL2O3), or rare earth oxides. The non-magnetic layer 32 may also be a mixture of these oxides. That is, the non-magnetic layer 32 is not limited to a binary compound consisting of two elements, but may also include a ternary compound consisting of three elements, such as magnesium aluminum oxide (MgAl2O4).

[0039] The ferromagnetic layer 33 is ferromagnetic and has an easy magnetization axis perpendicular to the film surface. The ferromagnetic layer 33 has a magnetization direction along the Z direction, either toward the bit line BL side or the word line WL side. The ferromagnetic layer 33 contains iron (Fe) and may further contain at least one of cobalt (Co) and nickel (Ni). The ferromagnetic layer 33 may further contain boron (B). More specifically, for example, the ferromagnetic layer 33 may contain iron-cobalt-boron (FeCoB) or iron boride (FeB) and have a body-centered cubic (bcc) crystal structure.

[0040] The non-magnetic layer 34 is a non-magnetic insulator, for example, containing magnesium oxide (MgO). The non-magnetic layer 34 has an NaCl crystal structure with its film surface oriented to the (001) plane, and functions as a seed material that acts as a nucleus for growing a crystalline film from the interface with the ferromagnetic layer 33 during the crystallization treatment of the ferromagnetic layer 33. The non-magnetic layer 34 is provided between the ferromagnetic layer 33 and the laminate 35, and together with these two ferromagnetic layers, forms a magnetic tunnel junction.

[0041] The laminate 35 can be considered as a single ferromagnetic layer and has an easy magnetization axis perpendicular to the film surface. The laminate 35 has a magnetization direction along the Z direction, either toward the bit line BL side or the word line WL side. The magnetization direction of the laminate 35 is fixed and, in the example shown in Figure 4, is oriented toward the ferromagnetic layer 37. Note that "the magnetization direction is fixed" means that the magnetization direction does not change due to a current (spin torque) of a magnitude that could reverse the magnetization direction of the ferromagnetic layer 33.

[0042] More specifically, the laminate 35 includes a ferromagnetic layer 35a, a non-magnetic layer 35b, and a ferromagnetic layer 35c. The ferromagnetic layer 35a functions as an interface layer (IL). The non-magnetic layer 35b functions as a function layer (FL). The ferromagnetic layer 35c functions as a main reference layer (MRL) 35c. For example, the ferromagnetic layer 35a, the non-magnetic layer 35b, and the ferromagnetic layer 35c are laminated in this order between the lower surface of the non-magnetic layer 34 and the upper surface of the non-magnetic layer 36.

[0043] For example, the upper surface of the ferromagnetic layer 35a is in contact with the non-magnetic layer 34. The ferromagnetic layer 35a is a ferromagnetic conductor and may contain, for example, iron (Fe), and at least one of cobalt (Co) and nickel (Ni). The ferromagnetic layer 35a may also contain boron (B). More specifically, for example, the ferromagnetic layer 35a may contain iron-cobalt-boron (FeCoB) or iron boride (FeB) and have a body-centered cubic crystal structure.

[0044] The non-magnetic layer 35b is provided between the ferromagnetic layer 35a and the ferromagnetic layer 35c. The non-magnetic layer 35b is a non-magnetic conductor and includes, for example, at least one metal selected from tantalum (Ta), hafnium (Hf), tungsten (W), zirconium (Zr), molybdenum (Mo), niobium (Nb), and titanium (Ti). The non-magnetic layer 35b has the function of maintaining the exchange coupling between the ferromagnetic layer 35a and the ferromagnetic layer 35c.

[0045] For example, the lower surface of the ferromagnetic layer 35c is in contact with the non-magnetic layer 36. The ferromagnetic layer 35c may include at least one multilayer film selected from, for example, a multilayer film of cobalt (Co) and platinum (Pt) (Co / Pt multilayer film), a multilayer film of cobalt (Co) and nickel (Ni) (Co / Ni multilayer film), and a multilayer film of cobalt (Co) and palladium (Pd) (Co / Pd multilayer film). Of the multilayer films constituting the ferromagnetic layer 35c, the layer in contact with the non-magnetic layer 36 includes, for example, cobalt (Co).

[0046] The non-magnetic layer 36 is a non-magnetic conductor and contains at least one element selected from, for example, ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), vanadium (V), and chromium (Cr).

[0047] The ferromagnetic layer 37 has an easy magnetization axis perpendicular to the film surface. The ferromagnetic layer 37 has a magnetization direction along the Z direction, either toward the bit line BL side or the word line WL side. The magnetization direction of the ferromagnetic layer 37 is fixed, similar to that of the laminate 35, and in the example shown in Figure 4, it is oriented toward the direction of the laminate 35. The ferromagnetic layer 37 functions as an anti-ferromagnetic coupling layer (AFL). The ferromagnetic layer 37 is a ferromagnetic conductor having a hexagonal close-packed (hcp) or face-centered cubic (fcc) crystal structure, and may contain, for example, cobalt (Co). The ferromagnetic layer 37 may include at least one multilayer film selected from a multilayer film of cobalt (Co) and platinum (Pt) (Co / Pt multilayer film), a multilayer film of cobalt (Co) and nickel (Ni) (Co / Ni multilayer film), and a multilayer film of cobalt (Co) and palladium (Pd) (Co / Pd multilayer film).

[0048] The ferromagnetic layers 35c and 37 are antiferromagnetically coupled by the non-magnetic layer 36. That is, the ferromagnetic layer 35c (more specifically, the layer in contact with the non-magnetic layer 36 among the multilayer films constituting the ferromagnetic layer 35c) and the ferromagnetic layer 37 are coupled so that they have magnetization directions that are antiparallel to each other. Therefore, in the example shown in Figure 4, the magnetization directions of the ferromagnetic layers 35c and 37 are oriented in directions opposite to each other. This coupling structure of the ferromagnetic layer 35c, the non-magnetic layer 36, and the ferromagnetic layer 37 is called a SAF (Synthetic Anti-Ferromagnetic) structure. The ferromagnetic layer 37 can cancel out the effect of the leakage magnetic field of the laminate 35 on the magnetization direction of the ferromagnetic layer 33. Therefore, the occurrence of asymmetry in the ease with which the magnetization of the ferromagnetic layer 33 reverses due to the leakage magnetic field of the laminate 35, etc. (that is, the ease with which the magnetization of the ferromagnetic layer 33 reverses direction differs depending on whether it reverses from one direction to the other or in the opposite direction) is suppressed.

[0049] Furthermore, the ferromagnetic layer 37 may also contain at least one element, either silicon (Si) or germanium (Ge). For example, iron (Fe) contained in the ferromagnetic layer 35a, etc., has the property of easily diffusing into the SAF structure under high-temperature environments such as the annealing process after the deposition of each layer in the magnetoresistive element MTJ. For example, when iron (Fe) diffuses into the SAF structure, the bonding force of the antiferromagnetic bond weakens. In contrast, silicon (Si) and germanium (Ge) have the property of suppressing the diffusion of iron (Fe) into the SAF structure. That is, the ferromagnetic layer 37 has the property of suppressing the diffusion of iron (Fe) into the SAF structure by containing silicon (Si) or germanium (Ge). In the following explanation, elements that easily diffuse during the annealing process, such as iron (Fe), will also be referred to as "easily diffusible elements." Also, elements that have the function of suppressing the diffusion of easily diffusible elements to other layers, such as the silicon (Si) or germanium (Ge) mentioned above, will also be referred to as "diffusion-suppressing elements."

[0050] The laminate 38 can be considered as a single non-magnetic layer and functions as an electrode to improve electrical connectivity with the bit line BL and word line WL. The laminate 38 has a three-layer structure. The laminate 38 includes non-magnetic layers 38a, 38b, and 38c. Non-magnetic layer 38a has a face-centered cubic crystal structure, non-magnetic layer 38b has a body-centered cubic crystal structure, and non-magnetic layer 38c has a diamond structure. For example, the non-magnetic layers 38a, 38b, and 38c are laminated in this order from the bottom surface of the ferromagnetic layer 37 (shift-cancellation layer SCL).

[0051] The non-magnetic layer 38a is a non-magnetic conductor having a face-centered cubic lattice and contains at least one element selected from, for example, iridium (Ir), platinum (Pt), gold (Au), rhodium (Rh), palladium (Pd), silver (Ag), nickel (Ni), and copper (Cu). The non-magnetic layer 38a is in contact with the ferromagnetic layer 37. The non-magnetic layer 38a has the function of separating the crystal structure of the upper layer (ferromagnetic layer 37) and the lower layer (non-magnetic layer 38b) of the non-magnetic layer 38a.

[0052] The non-magnetic layer 38b is a non-magnetic conductor having a body-centered cubic lattice and contains at least one element selected from, for example, tantalum (Ta), tungsten (W), niobium (Nb), molybdenum (Mo), vanadium (V), and chromium (Cr). The non-magnetic layer 38b is in contact with the surface of the non-magnetic layer 38a that is in contact with the ferromagnetic layer 37 and the surface that is opposite to it. The non-magnetic layer 38b has the function of separating the crystal structure of the upper layer (non-magnetic layer 38a) and the lower layer (non-magnetic layer 38c) of the non-magnetic layer 38b.

[0053] The non-magnetic layer 38c is a non-magnetic conductor having a diamond lattice and contains, for example, at least one element such as silicon (Si) and germanium (Ge) that functions as a diffusion-inhibiting element. The non-magnetic layer 38c is in contact with the surface of the non-magnetic layer 38b that is in contact with the non-magnetic layer 38a. In the film formation stage (i.e., the stage before the annealing process), the non-magnetic layer 38c functions as a source for supplying diffusion-inhibiting elements into the ferromagnetic layer 37. As a result, the laminate 38 can exhibit in the ferromagnetic layer 37 the property of suppressing the diffusion of iron (Fe) contained in the ferromagnetic layer 35a, etc., into the SAF structure prior to the annealing process.

[0054] The crystal structure described above can be confirmed, for example, by a transmission electron microscope (TEM). Furthermore, the material can be confirmed by electron energy loss spectroscopy (EELS) or energy dispersive X-ray spectroscopy (EDX).

[0055] In this embodiment, a spin injection writing method is employed in which a writing current is directly passed through the magnetoresistive element MTJ, and a spin torque is injected into the memory layer SL and the reference layer RL by this writing current, thereby controlling the magnetization direction of the memory layer SL and the reference layer RL. The magnetoresistive element MTJ can take on either a low-resistance state or a high-resistance state depending on whether the relative relationship of the magnetization directions of the memory layer SL and the reference layer RL is parallel or antiparallel.

[0056] When a write current Ic0 of a certain magnitude is passed through the magnetoresistive element MTJ in the direction of arrow A1 in Figure 4, that is, from the memory layer SL to the reference layer RL, the relative relationship of the magnetization directions of the memory layer SL and the reference layer RL becomes parallel. In this parallel state, the resistance value of the magnetoresistive element MTJ becomes the lowest, and the magnetoresistive element MTJ is set to a low-resistance state. This low-resistance state is called the "P (Parallel) state" and is defined, for example, as the data "0" state.

[0057] Furthermore, when a write current Ic1 greater than the write current Ic0 is applied to the magnetoresistive element MTJ in the direction of arrow A2 in Figure 4, i.e., from the reference layer RL to the memory layer SL (opposite direction to arrow A1), the relative relationship of the magnetization directions of the memory layer SL and the reference layer RL becomes antiparallel. In this antiparallel state, the resistance value of the magnetoresistive element MTJ becomes the highest, and the magnetoresistive element MTJ is set to a high-resistance state. This high-resistance state is called the "AP (Anti-Parallel) state" and is defined, for example, as the data "1" state.

[0058] In the following explanation, we will follow the data definition method described above, but the definition of data "1" and data "0" is not limited to the example given above. For example, state P may be defined as data "1" and state AP as data "0".

[0059] 1.5 Comparison of Magnetoresistive Effects Based on Differences in Buffer Layers Next, with reference to Figure 5, a comparison of the p-characteristics of magnetoresistive element MTJs based on differences in the buffer layer BUF will be explained. Figure 5 is a diagram showing an example of a comparison of the characteristics of magnetoresistive element MTJs based on differences in the buffer layer BUF. Figure 5 shows an embodiment, a first comparative example, and a second comparative example based on this embodiment. The characteristic values ​​of each example shown in Figure 5 are normalized values ​​with the first comparative example set to 1 (reference). In addition, the cross-sectional structure of each example shows the shift cancellation layer SCL and buffer layer BUF extracted from the cross-sectional structure of the magnetoresistive element MTJ. The structure other than the buffer layer BUF is substantially the same in the embodiment, the first comparative example, and the second comparative example.

[0060] As shown in Figure 5, the buffer layer BUF of the example has a three-layer structure consisting of silicon (Si), molybdenum (Mo), and platinum (Pt) from the bottom layer. That is, the non-magnetic layers 38a, 38b, and 38c are platinum (Pt) with a face-centered cubic lattice, molybdenum (Mo) with a body-centered cubic lattice, and silicon (Si) with a diamond lattice, respectively. In contrast, the buffer layer BUF of the first comparative example has a four-layer structure consisting of hafnium (Hf), molybdenum (Mo), silicon (Si), and platinum (Pt) from the bottom layer. The buffer layer BUF of the second comparative example has a three-layer structure consisting of tantalum (Ta), silicon (Si), and platinum (Pt) from the bottom layer. In the example, platinum (Pt) with a face-centered cubic lattice and molybdenum (Mo) with a body-centered cubic lattice are provided between the shift-cancellation layer SCL and Si. In contrast, in the first and second comparative examples, a platinum (Pt) layer with a face-centered cubic lattice is provided between the shift-canceling layer SCL and Si, and no layer with a body-centered cubic lattice (e.g., molybdenum (Mo)) is provided.

[0061] First, comparing the magnetoresistance ratio (MR), the magnetoresistance ratio MR of the example was 0.97, similar to that of the first comparative example. In contrast, the magnetoresistance ratio MR of the second comparative example was 0.86, which was lower than that of both the example and the first comparative example.

[0062] When comparing the area resistance RA (Resistance Area) of the magnetoresistive element MTJ, the area resistance RA of the Example and the Second Comparative Example were all 1, indicating that equivalent results were obtained in all three examples regardless of the structure of the buffer layer BUF.

[0063] Comparing the index Hex0 corresponding to the magnitude of the external magnetic field required to reverse the magnetization direction of the reference layer RL, the index Hex0 values ​​for the example and the second comparative example were 0.98 and 1.02, respectively, indicating that equivalent results were obtained in all three examples. For example, to obtain an ideal value for index Hex0, it is desirable to have a small amount of impurities (e.g., iron (Fe)) that inhibit antiferromagnetic coupling in the SAF structure. The structure of the example, like the first and second comparative examples, can reduce the amount of easily diffusible elements such as iron (Fe) that diffuse into the SAF structure during the annealing process, thereby suppressing a decrease in the bonding strength of the antiferromagnetic coupling.

[0064] Comparing the saturation magnetization (Ms*tSCL) of the entire shift cancellation layer SCL, the result for Example was 1, and regardless of the structure of the buffer layer BUF, equivalent results were obtained between Example and the first comparative example.

[0065] Comparing the anisotropic magnetic field (HkSCL) of the shift cancellation layer SCL, the example showed a value of 0.95, indicating that equivalent results were obtained between the example and the first comparative example, regardless of the structure of the buffer layer BUF.

[0066] From the above results, comparing the example with the first comparative example, the three-layer buffer layer BUF shown in the example yields results equivalent to the four-layer buffer layer BUF shown in the first comparative example. That is, by providing platinum (Pt) with a face-centered cubic lattice and molybdenum (Mo) with a body-centered cubic lattice between the shift-cancellation layer SCL and Si, the same results as the first comparative example can be obtained. Therefore, with the configuration according to this embodiment, the number of layers in the buffer layer BUF can be reduced from four to three. Consequently, manufacturing costs can be reduced. Furthermore, comparing the example with the second comparative example which has a three-layer structure, the magnetoresistance ratio MR is improved (the decrease in the magnetoresistance ratio MR is suppressed) by providing platinum (Pt) with a face-centered cubic lattice and molybdenum (Mo) with a body-centered cubic lattice between the shift-cancellation layer SCL and Si. By placing face-centered cubic platinum (Pt) and body-centered cubic molybdenum (Mo) between the shift-cancellation layer SCL and the diamond-lattice-containing Si, the disruption of the crystal structure of the shift-cancellation layer SCL due to the influence of the crystal structure on the diamond lattice can be suppressed. In other words, the disruption of the interface between the shift-cancellation layer SCL and the buffer layer BUF can be suppressed. As a result, the degradation of the magnetoresistance ratio MR can be suppressed.

[0067] 1.6 Effects of this embodiment The magnetic memory device 1 of this embodiment can suppress the degradation of the performance of the magnetoresistive element MTJ. More specifically, in the configuration according to the embodiment, the buffer layer BUF can be made into a three-layer structure consisting of a non-magnetic layer 38a having a face-centered cubic lattice, a non-magnetic layer 38b having a body-centered cubic lattice, and a non-magnetic layer 38c having a diamond lattice, from the shift-cancellation layer SCL side. By providing non-magnetic layers 38a and 38b between the shift-cancellation layer SCL and the non-magnetic layer 38c, disorder in the crystal structure of the shift-cancellation layer SCL can be suppressed. Therefore, the degradation of the magnetoresistance ratio MR can be suppressed.

[0068] Furthermore, in the configuration according to this embodiment, the non-magnetic layer 38c contains at least one element, silicon (Si) and germanium (Ge). This reduces the amount of easily diffusible elements such as iron (Fe) that diffuse into the SAF structure during the annealing process, thereby suppressing a decrease in the bonding strength of the antiferromagnetic bond.

[0069] Furthermore, with the configuration according to this embodiment, the buffer layer BUF can be made into a three-layer structure. This reduces the manufacturing cost of the magnetoresistive element.

[0070] 2. Variant Furthermore, various modifications are applicable, not limited to the embodiments described above.

[0071] For example, in the above-described embodiment, a two-terminal switching element was used as the switching element SE in the memory cell MC, but a MOS (metal oxide semiconductor) transistor may also be used as the switching element SE.

[0072] Figure 6 is a circuit diagram showing an example of the circuit configuration of a memory cell array 10A of a modified magnetic storage device. Figure 6 corresponds to the memory cell array 10 of the magnetic storage device 1 described in Figure 1 of the embodiment.

[0073] As shown in Figure 6, the memory cell array 10A comprises multiple memory cells MC, each associated with a row and a column. Memory cells MC in the same row are connected to the same word line WL, and both ends of memory cells MC in the same column are connected to the same bit line BL and the same source line BL.

[0074] Figure 7 is a cross-sectional view showing an example of the cross-sectional configuration of a memory cell MC of a modified magnetic storage device. Figure 7 corresponds to the memory cell MC described in Figure 3 of the embodiment.

[0075] As shown in Figure 7, the memory cell MC includes a selection transistor 41 (Tr) and a magnetoresistive element 42 (MTJ).

[0076] The selection transistor 41 is a MOS transistor. The selection transistor 41 is provided on a semiconductor substrate 40. The selection transistor 41 functions as a switching element SE. The selection transistor 41 includes a gate insulating film 43, a gate electrode 44, and two diffusion layer regions 45.

[0077] The gate insulating film 43 is provided on the semiconductor substrate 40. For example, the gate insulating film 43 contains silicon oxide (SiO).

[0078] The gate electrode 44 is provided on the gate insulating film 43. The gate electrode 44 functions as a word line WL. The gate electrode 44 extends, for example, along the X direction and is commonly connected to a plurality of select transistors 41 aligned in the X direction.

[0079] The two diffusion layer regions 45 function as a pair of source and drain regions, respectively. For example, the two diffusion layer regions 45 are provided in the region near the upper surface of the semiconductor substrate 40 at both ends along the Y direction of the gate electrode 44.

[0080] The configuration of the magnetoresistive element 42 is the same as that of the magnetoresistive element MTJ shown in Figure 4 of the embodiment.

[0081] A contact plug 46 is provided on the diffusion layer region 45 (either source or drain) at the first end of the selection transistor 41. The contact plug 46 is connected to the lower surface (first end) of the magnetoresistive element 42. A contact plug 47 is provided on the upper surface (second end) of the magnetoresistive element 42, and the upper surface of the contact plug 47 is connected to a wiring layer 48 that functions as a bit line BL. The wiring layer 48 extends, for example, along the Y direction and is commonly connected to the second ends of multiple magnetoresistive elements 42 (not shown) aligned along the Y direction.

[0082] A contact plug 49 is provided on the diffusion layer region 45 (the other of the source or drain) located at the second end of the selection transistor 41. The contact plug 49 is connected to the underside of a wiring layer 50 that functions as a bit line / BL. The wiring layer 50 extends, for example, along the Y direction and is commonly connected to the second ends of multiple selection transistors 41 (not shown) that are aligned along the Y direction. The wiring layers 48 and 50 are aligned, for example, along the Y direction. The wiring layer 48 is located, for example, above the wiring layer 50. The wiring layers 48 and 50 are arranged to avoid physical and electrical interference with each other. The selection transistor 41, magnetoresistive element 42, gate insulating film 43, gate electrode 44, diffusion layer region 45, contact plugs 46, 47, and 49, and wiring layers 48 and 50 are covered by an interlayer insulating film 51.

[0083] By configuring the device as described above, even when a MOS transistor, which is a three-terminal switching element, is used instead of a two-terminal switching element for the switching element SE, the same effects as in the embodiment can be achieved.

[0084] 3. Others While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0085] 1…Magnetic storage device 10, 10A…Memory cell array 11... Row selection circuit 12…Column selection circuit 13…Decode circuit 14…Writing circuit 15...Readout circuit 16…Voltage generation circuit 17…Input / Output Circuits 18…Control circuits 21, 22, 48, 50...wiring layer 31, 32, 34, 35b, 36, 38a, 38b, 38c...Nonmagnetic layer 33, 35a, 35c, 37...Ferromagnetic layer 35, 38... Laminate 40… Semiconductor substrates 41…Selection transistor 43…Gate insulating film 44… Gateway 45...Diffusion layer region 46, 47, 49... Contact plugs 51...Interlayer insulating film 42. MTJ…Magnetoresistive element BL, / BL... bit line MC…Memory Cell SE... Switching element WL...Word line

Claims

1. Equipped with a magnetoresistive element, The magnetoresistive element is The first ferromagnetic layer and The second ferromagnetic layer, The third ferromagnetic layer, A first non-magnetic layer is provided between the first ferromagnetic layer and the second ferromagnetic layer, A second non-magnetic layer is provided between the second ferromagnetic layer and the third ferromagnetic layer, A third non-magnetic layer comprising at least one element selected from iridium (Ir), platinum (Pt), gold (Au), rhodium (Rh), palladium (Pd), silver (Ag), nickel (Ni), and copper (Cu), A fourth nonmagnetic layer comprising at least one element selected from tantalum (Ta), tungsten (W), niobium (Nb), molybdenum (Mo), vanadium (V), and chromium (Cr), A fifth nonmagnetic layer containing at least one element of silicon (Si) and germanium (Ge) Includes, The second ferromagnetic layer is located between the first ferromagnetic layer and the third ferromagnetic layer. The third ferromagnetic layer is located between the second nonmagnetic layer and the third nonmagnetic layer. The fourth non-magnetic layer is located between the third non-magnetic layer and the fifth non-magnetic layer. Magnetic storage device.

2. The third nonmagnetic layer has a face-centered cubic lattice, The fourth nonmagnetic layer has a body-centered cubic lattice. The fifth nonmagnetic layer has a diamond lattice, The magnetic storage device according to claim 1.

3. The third ferromagnetic layer comprises cobalt (Co) and at least one of silicon (Si) and germanium (Ge). The magnetic storage device according to claim 1.

4. The first ferromagnetic layer contains iron (Fe), The magnetic storage device according to claim 1.

5. The first ferromagnetic layer further comprises at least one of cobalt (Co) and nickel (Ni). The magnetic storage device according to claim 4.

6. The first ferromagnetic layer further comprises boron (B), The magnetic storage device according to claim 4.

7. The second ferromagnetic layer contains iron (Fe), The magnetic storage device according to claim 1.

8. The second ferromagnetic layer further comprises at least one of cobalt (Co) and nickel (Ni). The magnetic storage device according to claim 7.

9. The second ferromagnetic layer further comprises boron (B), The magnetic storage device according to claim 7.

10. The first non-magnetic layer comprises an oxide containing magnesium (Mg), The magnetic storage device according to claim 1.

11. The second non-magnetic layer comprises at least one element selected from ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), vanadium (V), and chromium (Cr). The magnetic storage device according to claim 1.

12. The second ferromagnetic layer and the third ferromagnetic layer have opposite magnetization directions. The magnetic storage device according to claim 1.

13. The magnetoresistive element is When the magnetization direction of the first ferromagnetic layer and the magnetization direction of the second ferromagnetic layer are parallel, the resistance value becomes the first value. When the magnetization direction of the first ferromagnetic layer and the magnetization direction of the second ferromagnetic layer are antiparallel, the second resistance value is obtained. The magnetic storage device according to claim 1.

14. The first resistance value is smaller than the second resistance value. The magnetic storage device according to claim 13.

15. The device further comprises a switching element connected in series with the magnetoresistive element. The magnetic storage device according to claim 1.

16. The aforementioned switching element is a two-terminal switching element. The magnetic storage device according to claim 15.

17. The switching element is a MOS (Metal Oxide Semiconductor) transistor. The magnetic storage device according to claim 15.

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