Magnetic storage device

Abstract

The embodiment provides a magnetic storage device capable of stably storing data. The magnetic storage device of the embodiment includes a magnetoresistance effect element including a first magnetic layer having a variable magnetization direction, a second magnetic layer having a variable magnetization direction, a third magnetic layer having a fixed magnetization direction, and a non-magnetic layer, the first magnetic layer being disposed between the second magnetic layer and the third magnetic layer, the non-magnetic layer being disposed between the first magnetic layer and the third magnetic layer, the second magnetic layer having a superlattice structure in which a first element layer formed of a first element and a second element layer formed of a second element are alternately stacked, the first element being cobalt (Co), the second element being selected from platinum (Pt), nickel (Ni), and palladium (Pd), and the second magnetic layer containing chromium (Cr) as a third element.

Description

[0001] [Related Applications]

[0002] This application claims priority to Japanese Patent Application No. 2020-155729 (filed on September 16, 2020). This application incorporates the entire contents of that basic application by reference. Technical Field

[0003] Embodiments of the present invention relate to a magnetic storage device. Background Technology

[0004] A non-volatile magnetic storage device is proposed, which integrates magnetoresistive elements as storage elements on a semiconductor substrate. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a magnetic storage device that can stably store data.

[0006] The magnetic storage device of the embodiment includes a magnetoresistive element, which includes a first magnetic layer having a variable magnetization direction, a second magnetic layer having a variable magnetization direction, a third magnetic layer having a fixed magnetization direction, and a non-magnetic layer. The first magnetic layer is disposed between the second magnetic layer and the third magnetic layer, and the non-magnetic layer is disposed between the first magnetic layer and the third magnetic layer. The second magnetic layer has a superlattice structure formed by alternating layers of a first element and a second element, wherein the first element is cobalt (Co), the second element is selected from platinum (Pt), nickel (Ni), and palladium (Pd), and the second magnetic layer contains chromium (Cr) as the third element. Attached Figure Description

[0007] Figure 1 This is a cross-sectional view schematically illustrating the configuration of the magnetoresistive effect element in an embodiment.

[0008] Figure 2 This is a cross-sectional view schematically showing the structure of the second magnetic layer of the magnetoresistive effect element in an embodiment.

[0009] Figure 3 This is a diagram showing the magnetic properties of the magnetic layer of the magnetoresistive element in the embodiment.

[0010] Figure 4 This is a diagram showing the magnetic properties of the magnetic layer of the magnetoresistive element in the comparative example.

[0011] Figure 5 This is a graph showing the relationship between the saturation magnetization Mst and the thermal stability ΔE of the magnetoresistive effect element in the embodiments and the comparative examples.

[0012] Figure 6 This is a cross-sectional view schematically illustrating a variation of the configuration of the magnetoresistive effect element in the embodiment.

[0013] Figure 7 This is a perspective view schematically illustrating an example of the configuration of a magnetic storage device using a magnetoresistive element according to an embodiment.

[0014] Figure 8 This is a perspective view schematically illustrating another example of the configuration of a magnetic storage device using a magnetoresistive element according to the embodiment. Detailed Implementation

[0015] The embodiments will now be described with reference to the accompanying drawings.

[0016] Figure 1 This is a cross-sectional view schematically illustrating the configuration of a magnetic storage device (non-volatile magnetic storage device) according to an embodiment. Specifically, it is a cross-sectional view schematically illustrating the configuration of a magnetoresistive element according to an embodiment. In this embodiment, the case of using an MTJ (magnetic tunnel junction) element as the magnetoresistive element will be described. In practice, multiple magnetoresistive elements are integrated on a semiconductor substrate.

[0017] Figure 1 The magnetoresistive effect element 100 shown is disposed above a semiconductor substrate (not shown) and has a stacked structure including a first magnetic layer 10, a second magnetic layer 20, a third magnetic layer 30, a fourth magnetic layer 40, a tunnel barrier layer (nonmagnetic layer) 50, an intermediate layer 60, an intermediate layer 70, a capping layer 80 and a lower conductive layer 90.

[0018] Specifically, the magnetoresistive element 100 has a first magnetic layer 10 and a third magnetic layer 30 disposed between the second magnetic layer 20 and the fourth magnetic layer 40, a first magnetic layer 10 disposed between the second magnetic layer 20 and the third magnetic layer 30, and a tunnel barrier layer (non-magnetic layer) 50 disposed between the first magnetic layer 10 and the third magnetic layer 30. Additionally, an intermediate layer 60 is disposed between the first magnetic layer 10 and the second magnetic layer 20, and an intermediate layer 70 is disposed between the third magnetic layer 30 and the fourth magnetic layer 40. These layers 10 to 70 are located between the capping layer 80 and the lower conductive layer 90.

[0019] The first magnetic layer 10 is formed of a ferromagnetic layer having a variable magnetization direction and functions as part of the storage layer of the magnetoresistive element 100. A variable magnetization direction refers to a magnetization direction that changes relative to a specific write current. The first magnetic layer 10 contains at least one of cobalt (Co) and iron (Fe). Specifically, the first magnetic layer 10 is formed of CoFeB containing cobalt (Co), iron (Fe), and boron (B).

[0020] The second magnetic layer 20 is also formed of a ferromagnetic material with a variable magnetization direction and functions as part of the storage layer of the magnetoresistive effect element 100. The magnetization direction of the second magnetic layer 20 varies in the same direction as the magnetization direction of the first magnetic layer 10.

[0021] Figure 2 This is a cross-sectional view schematically showing the structure of the second magnetic layer 20.

[0022] The second magnetic layer 20 has a superlattice structure formed by alternating layers of a first-element layer 21 and a second-element layer 22. The first element is cobalt (Co), and the second element is platinum (Pt), nickel (Ni), or palladium (Pd). Additionally, the second magnetic layer 20 contains chromium (Cr) as a third element. The bottom layer of the second magnetic layer 20 (the layer in contact with the intermediate layer 60) can be either the first-element layer 21 or the second-element layer 22. Similarly, the top layer of the second magnetic layer 20 (the layer in contact with the capping layer 80) can also be either the first-element layer 21 or the second-element layer 22.

[0023] Furthermore, in the following description, it will be explained that the first element is cobalt (Co), the second element is platinum (Pt), the second magnetic layer 20 has a superlattice structure formed by alternating layers of Co and Pt, and the superlattice structure contains Cr.

[0024] The third magnetic layer 30 is formed of a ferromagnetic material with a fixed magnetization direction and functions as part of the reference layer of the magnetoresistive element 100. A fixed magnetization direction means that the magnetization direction does not change relative to a specific write current. The third magnetic layer 30 contains at least one of cobalt (Co) and iron (Fe). Specifically, the third magnetic layer 30 is formed of CoFeB containing cobalt (Co), iron (Fe), and boron (B).

[0025] The fourth magnetic layer 40 is also formed of a ferromagnetic material with a fixed magnetization direction and has antiferromagnetic coupling. That is, the fourth magnetic layer 40 has SAF coupling (synthetic antiferromagnetic coupling) and functions as part of the reference layer of the magnetoresistive effect element 100. For example, the fourth magnetic layer 40 includes a first layer portion 41 formed of a Co layer or a Co / Pt superlattice layer, a second layer portion 42 formed of a Co / Pt superlattice layer, and a third layer portion 43 formed of a ruthenium (Ru) layer or an iridium (Ir) layer, and the first layer portion 41 and the second layer portion 42 are antiferromagnetically coupled through the third layer portion 43.

[0026] The tunnel barrier layer 50 is a non-magnetic layer disposed between the first magnetic layer 10 and the third magnetic layer 30, and is formed of an insulating material. The tunnel barrier layer 50 contains magnesium (Mg) and oxygen (O). Specifically, the tunnel barrier layer 50 is formed of MgO.

[0027] The intermediate layer 60 is a non-magnetic layer disposed between the first magnetic layer 10 and the second magnetic layer 20, and is formed of a specific metallic material. As described below, this intermediate layer 60 can also function as a third element containing chromium (Cr) as a third element.

[0028] The intermediate layer 70 is a non-magnetic layer disposed between the third magnetic layer 30 and the fourth magnetic layer 40, and is formed of a specific metallic material (such as molybdenum (Mo), tantalum (Ta), or tungsten (W)).

[0029] The capping layer 80 is a non-magnetic layer disposed on the second magnetic layer 20. In addition to its function as a capping layer, the capping layer 80 also functions as a third element-containing layer containing chromium (Cr) as a third element. The capping layer 80 will be described in detail below.

[0030] The lower conductive layer 90 is a non-magnetic layer disposed below the fourth magnetic layer 40, and is formed of a tantalum (Ta) layer or the like.

[0031] The magnetoresistive element 100 is an STT (spin transfer torque) type magnetoresistive element with perpendicular magnetization. That is, the first magnetic layer 10, the second magnetic layer 20, the third magnetic layer 30, and the fourth magnetic layer 40 all have a magnetization direction perpendicular to their film surface.

[0032] Furthermore, the magnetoresistive element 100 exhibits a relatively low resistance when the magnetization direction of the first magnetic layer 10 is parallel to the magnetization direction of the third magnetic layer 30, and a relatively high resistance when the magnetization direction of the first magnetic layer 10 is antiparallel to the magnetization direction of the third magnetic layer 30. Therefore, the magnetoresistive element 100 can store binary data based on its resistance state (low resistance state or high resistance state). Additionally, the resistance state (low resistance state or high resistance state) of the magnetoresistive element 100 can be set according to the direction of the current flowing into it.

[0033] According to this embodiment, a magnetoresistive element with low saturation magnetization (Mst) and high perpendicular magnetic anisotropy can be obtained. Therefore, a magnetoresistive element can be obtained that can stably store data even with advancements in miniaturization and high integration of integrated circuits. The following is a detailed description.

[0034] To stably store data in magnetoresistive elements, it is crucial to achieve high thermal stability ΔE. However, with advancements in miniaturization and high integration of integrated circuits, the influence of the stray magnetic field between adjacent magnetoresistive elements increases. Therefore, it becomes increasingly difficult to obtain magnetoresistive elements with high thermal stability ΔE while simultaneously reducing saturation magnetization Mst.

[0035] In this embodiment, Cr is included as a third element in the second magnetic layer 20, which has a superlattice structure having a first element layer (e.g., a Co layer) 21 and a second element layer (e.g., a Pt layer) 22. In this way, by using a second magnetic layer 20 containing Cr, the perpendicular magnetic anisotropy of the second magnetic layer 20 can be improved, and a high thermal stability ΔE can be ensured even if the saturation magnetization Mst is low.

[0036] Figure 3 This is a graph showing the magnetic properties (relationship between external magnetic field Hex and magnetization Mt) of the magnetic layer (a Co / Pt superlattice layer containing Cr) in this embodiment. Figure 4 This is a graph showing the magnetic properties of the magnetic layer of the comparative example (a Cr-free Co / Pt superlattice layer). According to... Figure 3 and Figure 4 It can be seen that this implementation method ( Figure 3 ) and comparative example ( Figure 4 Compared to ), saturation magnetization is lower.

[0037] Figure 5 This is a graph showing the relationship between saturation magnetization Mst and thermal stability ΔE. In case (a) where the magnetic layer of this embodiment (a Co / Pt superlattice layer containing Cr) is used as the second magnetic layer 20, the thermal stability ΔE is significantly improved compared to case (b) where the magnetic layer of the comparative example (a Co / Pt superlattice layer without Cr) is used as the second magnetic layer 20. In other words, in this embodiment, even with a low saturation magnetization Mst, a high thermal stability ΔE can be obtained.

[0038] according to Figure 3 , Figure 4 and Figure 5 It can be seen that, in this embodiment, by using the second magnetic layer 20 containing Cr, a magnetoresistive effect element with high thermal stability ΔE can be obtained even with a low saturation magnetization Mst.

[0039] The second magnetic layer 20 containing Cr can be formed by heat treatment to diffuse Cr from the capping layer 80, which is a Cr-containing layer, into the second magnetic layer 20. In this way, by diffusing Cr from the capping layer 80 into the second magnetic layer 20, the second magnetic layer 20 can contain Cr while maintaining the superlattice structure of the second magnetic layer (Co / Pt superlattice layer) 20.

[0040] Generally, when the second magnetic layer (Co / Pt superlattice layer) 20 is disposed on the upper side of the tunnel barrier layer 50, it is difficult to form a Co / Pt superlattice layer with high vertical magnetic anisotropy. In this embodiment, by diffusing Cr from the capping layer 80 into the second magnetic layer (Co / Pt superlattice layer) 20, Cr can be easily incorporated into the second magnetic layer 20, thereby forming a second magnetic layer 20 with high vertical magnetic anisotropy.

[0041] The following is an example of a capping layer (including a Cr layer) 80.

[0042] In the first example, a Cr layer that actually contains only Cr (the third element) was used as the capping layer (containing a Cr layer) 80.

[0043] In the second example, the capping layer (containing a Cr layer) 80 contains at least one element selected from Cr (the third element), Co (the first element), and Pt (the second element). Specifically, in the second example, a CrCo alloy layer, a CrPt alloy layer, or a CrCoPt alloy layer is used as the capping layer (containing a Cr layer) 80.

[0044] Furthermore, in both the first and second examples, the uppermost layer of the second magnetic layer 20 (the layer in contact with the capping layer 80) can be either a Co layer or a Pt layer.

[0045] Furthermore, in this embodiment, in order to introduce the Cr contained in the capping layer 80 into the second magnetic layer 20, the concentration of Cr contained in the capping layer (Cr-containing layer) 80 is higher than the concentration of Cr contained in the second magnetic layer (Co / Pt superlattice layer) 20.

[0046] Alternatively, the Cr-containing layer described above can be used for the capping layer 80, and further, the Cr-containing layer described above can also be used for the intermediate layer 60. That is, as the intermediate layer (Cr-containing layer) 60, a Cr layer that actually contains only Cr (the third element) can be used, or an alloy layer containing at least one of Cr (the third element) and Co (the first element) and Pt (the second element) can be used.

[0047] In this way, by also using a Cr-containing layer in the intermediate layer 60, Cr can diffuse from the upper and lower surfaces of the capping layer 80 and the intermediate layer 60, i.e., the second magnetic layer 20. Therefore, Cr can be introduced into the second magnetic layer 20 more efficiently. In this case, the concentration of Cr in the capping layer (Cr-containing layer) 80 and the concentration of Cr in the intermediate layer (Cr-containing layer) 60 are both higher than the concentration of Cr in the second magnetic layer (Co / Pt superlattice layer) 20.

[0048] Furthermore, in the example described, the case of using a Co / Pt superlattice layer as the second magnetic layer 20, that is, using cobalt (Co) as the first element constituting the superlattice layer and platinum (Pt) as the second element, was explained. However, the case of using nickel (Ni) or palladium (Pd) instead of platinum (Pt) as the second element is also the same.

[0049] Next, variations of this embodiment will be described. Furthermore, the basic matters are the same as in the previous embodiment, and the descriptions of matters already described in the previous embodiment will be omitted.

[0050] Figure 6 This is a cross-sectional view schematically illustrating the configuration of the non-volatile magnetic storage device (magnetoresistive element) of this variation example.

[0051] In the described embodiment, a magnetoresistive element with the storage layer on the upper side and the reference layer on the lower side (a top-free type magnetoresistive element) was described. However, in this variation, a magnetoresistive element with the storage layer on the lower side and the reference layer on the upper side (a bottom-free type magnetoresistive element) is used.

[0052] In this variation, the capping layer 80 also uses a Cr-containing layer as described in the embodiments, and the intermediate layer 60 also uses a Cr-containing layer as described in the embodiments.

[0053] In this variation, by diffusing the Cr contained in the capping layer 80 to the fourth magnetic layer 40, the perpendicular magnetic anisotropy of the fourth magnetic layer 40 can be improved. Similarly, by diffusing the Cr contained in the intermediate layer 60 to the second magnetic layer 20, the perpendicular magnetic anisotropy of the second magnetic layer 20 can be improved. Therefore, in this variation, similar to the described embodiment, a high thermal stability ΔE can be ensured.

[0054] Figure 7 This is a perspective view schematically illustrating an example of the configuration of a magnetic storage device using the magnetoresistive element 100 described in the embodiments and variations.

[0055] Figure 7 The illustrated magnetic storage device includes: a plurality of first wirings 410 extending in the X direction; a plurality of second wirings 420 extending in the Y direction; and a storage cell 300 connected between the first wirings 410 and the second wirings 420. One of the first wirings 410 and the second wirings 420 corresponds to a word line, and the other corresponds to a bit line. Each storage cell 300 includes a magnetoresistive element 100 and a selector (switching element) 200 connected in series with respect to the magnetoresistive element 100.

[0056] The magnetoresistive effect element 100 can use the magnetoresistive effect element described in the embodiments and variations.

[0057] Selector 200 may, for example, use a two-terminal switching element. When the voltage applied between the two terminals is less than a threshold, the switching element is in a "high resistance state," for example, a non-conducting state. When the voltage applied between the two terminals is above the threshold, the switching element is in a "low resistance state," for example, a conducting state.

[0058] By applying a specific voltage between the first wiring 410 and the second wiring 420 connected to the requested memory cell 300, the selector 200 contained in the requested memory cell 300 becomes in the ON state (ON state), thereby writing to or reading from the magnetoresistive element 100 contained in the requested memory cell 300.

[0059] Figure 8 This is a perspective view schematically illustrating another example of the configuration of a magnetic storage device using the magnetoresistive effect element 100 described in the embodiments and variations.

[0060] exist Figure 7 In the example shown, the magnetoresistive element 100 is located on the lower layer and the selector 200 is located on the upper layer, but... Figure 8 In the example shown, the magnetoresistive element 100 is located on the upper layer and the selector 200 is located on the lower layer. Other basic configurations are similar. Figure 7 The example shown is the same.

[0061] By using the magnetoresistive effect element 100 of this embodiment as such Figure 7 and Figure 8 The magnetic storage device shown can provide a magnetic storage device that can stably store data.

[0062] Several embodiments of the present invention have been described, but these embodiments are provided by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in many other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments or variations thereof are included in the scope or spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

[0063] [Explanation of Symbols]

[0064] 10 First magnetic layer

[0065] 20 Second magnetic layer

[0066] 21. First Element Layer

[0067] 22 Element Layer 2

[0068] 30 Third magnetic layer

[0069] 40 Fourth magnetic layer

[0070] 41 Part 1

[0071] 42 Part 2

[0072] 43 Part 3

[0073] 50. Tunnel barrier layer (non-magnetic layer)

[0074] 60. Intermediate layer (layer containing the 3rd element)

[0075] 70 Intermediate Layer

[0076] 80. Cover layer (layer containing element 3)

[0077] 90 Lower conductive layer

[0078] 100 Magnetoresistive element

[0079] 200 Selector (Switching Element)

[0080] 300 storage units

[0081] 410 Wiring 1

[0082] 420 Second wiring.

Claims

1. A magnetic storage device, characterized in that: Equipped with magnetoresistive elements, The magnetoresistive element comprises: a first magnetic layer having a variable magnetization direction, a second magnetic layer having a variable magnetization direction and containing a third element, a third magnetic layer having a fixed magnetization direction, a non-magnetic layer, and a third element-containing layer containing the third element. The first magnetic layer is disposed between the second magnetic layer and the third magnetic layer, the second magnetic layer is disposed between the first magnetic layer and the third element-containing layer, and the non-magnetic layer is disposed between the first magnetic layer and the third magnetic layer; and The second magnetic layer has a superlattice structure formed by alternating layers of a first element formed by a first element and a second element formed by a second element. The first element is cobalt (Co), and the second element is selected from platinum (Pt), nickel (Ni), and palladium (Pd). The third element is chromium (Cr), and the concentration of the third element in the third element-containing layer is higher than the concentration of the third element in the second magnetic layer.

2. The magnetic storage device according to claim 1, characterized in that: The third element contains a layer that also contains at least one of the first element and the second element.

3. A magnetic storage device, characterized in that: Equipped with magnetoresistive elements, The magnetoresistive element comprises: a first magnetic layer having a variable magnetization direction, a second magnetic layer having a variable magnetization direction and containing a third element, a third magnetic layer having a fixed magnetization direction, a non-magnetic layer, and a third element-containing layer containing the third element. The first magnetic layer is disposed between the second magnetic layer and the third magnetic layer, the third element-containing layer is disposed between the first magnetic layer and the second magnetic layer, and the non-magnetic layer is disposed between the first magnetic layer and the third magnetic layer; and The second magnetic layer has a superlattice structure formed by alternating layers of a first element formed by a first element and a second element formed by a second element. The first element is cobalt (Co), and the second element is selected from platinum (Pt), nickel (Ni), and palladium (Pd). The third element is chromium (Cr), and the concentration of the third element in the third element-containing layer is higher than the concentration of the third element in the second magnetic layer.

4. The magnetic storage device according to claim 3, characterized in that: The third element contains a layer that also contains at least one of the first element and the second element.

5. The magnetic storage device according to claim 1 or 3, characterized in that: The magnetization direction of the second magnetic layer changes in the same direction as the magnetization direction of the first magnetic layer.

6. The magnetic storage device according to claim 1 or 3, characterized in that: The magnetoresistive element is vertically magnetized.

7. The magnetic storage device according to claim 1 or 3, characterized in that: The first magnetic layer contains at least one of cobalt (Co) and iron (Fe).

8. The magnetic storage device according to claim 1 or 3, characterized in that: The third magnetic layer contains at least one of cobalt (Co) and iron (Fe).

9. The magnetic storage device according to claim 1 or 3, characterized in that: The non-magnetic layer contains magnesium (Mg) and oxygen (O).

10. The magnetic storage device according to claim 1 or 3, characterized in that: The magnetoresistive element further comprises a fourth magnetic layer, which has a fixed magnetization direction and antiferromagnetic coupling, and The first magnetic layer and the third magnetic layer are disposed between the second magnetic layer and the fourth magnetic layer.

11. The magnetic storage device according to claim 1 or 3, characterized in that: It also includes a switching element connected in series with the magnetoresistive effect element, and The memory cell is composed of the magnetoresistive element and the switching element.

12. The magnetic storage device according to claim 11, characterized in that: The switching element is a two-terminal switching element. When the voltage applied between the two terminals is less than a threshold, it is in a high-resistance state; when the voltage applied between the two terminals is above the threshold, it is in a low-resistance state.

13. The magnetic storage device according to claim 11, characterized in that: It also has a first wiring harness and a second wiring harness, and The storage unit is connected between the first wiring and the second wiring.

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