Magnetic storage device

Abstract

According to an embodiment, a magnetic storage device has a layered structure including: a first magnetic layer having a fixed magnetization direction; a second magnetic layer having a variable magnetization direction; a non-magnetic layer disposed between the first magnetic layer and the second magnetic layer; a molybdenum (Mo) layer disposed on an opposite side of the non-magnetic layer from the second magnetic layer; and an oxide layer disposed between the second magnetic layer and the Mo layer, containing a predetermined element selected from among rare earth elements, silicon (Si), and aluminum (Al).

Description

[0001] This application is based on, and seeks the interest in, the entire contents of, Japanese Patent Application No. 2021-43141, filed on March 17, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The embodiments described herein generally relate to magnetic memory devices. Background Technology

[0003] A magnetic storage device is proposed that integrates multiple nonvolatile magnetoresistance effect elements on a semiconductor substrate. Summary of the Invention

[0004] Generally, according to one embodiment, a magnetic storage device has a stacked structure comprising: a first magnetic layer having a fixed magnetization direction; a second magnetic layer having a variable magnetization direction; a non-magnetic layer disposed between the first magnetic layer and the second magnetic layer; a molybdenum (Mo) layer disposed on the opposite side of the non-magnetic layer relative to the second magnetic layer; and an oxide layer disposed between the second magnetic layer and the molybdenum (Mo) layer, containing a predetermined element selected from rare earth elements, silicon (Si), and aluminum (Al). Attached Figure Description

[0005] Figure 1 This is a cross-sectional view schematically showing the structure of the stacked magnetoresistive effect element included in the magnetic storage device of the first embodiment.

[0006] Figure 2 This is a cross-sectional view schematically showing the structure of the stacked magnetoresistive effect element included in the magnetic storage device of the second embodiment.

[0007] Figure 3 This is a perspective view schematically showing the structure of a magnetic storage device using the magnetoresistive effect element shown in the first and second embodiments. Detailed Implementation

[0008] The embodiments will now be described with reference to the accompanying drawings.

[0009] (Implementation Method 1)

[0010] Figure 1This is a schematic cross-sectional view illustrating the structure of the stacked structure of the magnetoresistive effect element included in the magnetic storage device of the first embodiment. A magnetic tunnel junction (MTJ) element is used as the magnetoresistive effect element.

[0011] A stacked structure 100 is provided above the semiconductor substrate 10. The stacked structure 100 has the following layers stacked sequentially from the lower layer side (semiconductor substrate 10 side) toward the upper layer side: a buffer layer 11, a silicon boron (SiB) layer 12, a displacement elimination layer (third magnetic layer) 13, a spacer layer 14, a reference layer (first magnetic layer) 15, a tunnel barrier layer (nonmagnetic layer) 16, a storage layer (second magnetic layer) 17, an oxide layer 18, a molybdenum (Mo) layer 19, and an upper capping layer 20.

[0012] Specifically, the stacked structure 100 includes a reference layer 15, a storage layer 17, a tunnel barrier layer 16 disposed between the reference layer 15 and the storage layer 17, a molybdenum (Mo) layer 19 disposed on the opposite side of the tunnel barrier layer 16 relative to the storage layer 17, an oxide layer 18 disposed between the storage layer 17 and the molybdenum (Mo) layer 19, a displacement elimination layer 13 disposed on the opposite side of the tunnel barrier layer 16 relative to the reference layer 15, a buffer layer 11 disposed on the opposite side of the reference layer 15 relative to the displacement elimination layer 13, a silicon boron (SiB) layer 12 disposed between the displacement elimination layer 13 and the buffer layer 11, a spacer layer 14 disposed between the reference layer 15 and the displacement elimination layer 13, and an upper capping layer 20 disposed on the opposite side of the oxide layer 18 relative to the molybdenum (Mo) layer 19.

[0013] The reference layer (first magnetic layer) 15 is a ferromagnetic layer disposed on the displacement elimination layer 13 and having a fixed magnetization direction. Furthermore, the fixed magnetization direction means that the magnetization direction remains unchanged relative to a predetermined write current. The reference layer 15 includes a first layer portion 15a and a second layer portion 15b, with the first layer portion 15a disposed on the second layer portion 15b. The first layer portion 15a is formed of an FeCoB layer containing iron (Fe), cobalt (Co), and boron (B). The second layer portion 15b contains at least one element selected from cobalt (Co), platinum (Pt), nickel (Ni), and palladium (Pd).

[0014] The tunnel barrier layer (non-magnetic layer) 16 is an insulating layer disposed on the reference layer 15. The tunnel barrier layer 16 is formed of an MgO layer containing magnesium (Mg) and oxygen (O).

[0015] The storage layer (second magnetic layer) 17 is a ferromagnetic layer disposed on the tunnel barrier layer 16 and having a variable magnetization direction. Furthermore, the variable magnetization direction means that the magnetization direction changes relative to a predetermined write current. The storage layer 17 is formed of an FeCoB layer containing iron (Fe), cobalt (Co), and boron (B).

[0016] A displacement elimination layer (third magnetic layer) 13 is disposed on the buffer layer 11 through a silicon boron (SiB) layer 12. The displacement elimination layer 13 is a strongly magnetic layer with a fixed magnetization direction that is antiparallel to the magnetization direction of the reference layer 15, and functions to eliminate the magnetic field applied from the reference layer 15 to the storage layer 17. The displacement elimination layer 13 contains at least one element selected from cobalt (Co), platinum (Pt), nickel (Ni), and palladium (Pd).

[0017] In this embodiment, the displacement elimination layer 13 has a superlattice structure with alternating layers of Co and Pt. Furthermore, the displacement elimination layer 13 has an FCC (face-centered cubic) crystal structure or an HCP (hexagonal close-packed) crystal structure. In the case of the FCC crystal structure, the displacement elimination layer 13 has a (111) facet in a direction perpendicular to the stacking direction of the stacked structure 100. In the case of the HCP crystal structure, the displacement elimination layer 13 has a (0001) facet in a direction perpendicular to the stacking direction of the stacked structure 100.

[0018] A spacer layer 14 is disposed between the reference layer 15 and the displacement elimination layer 13, and the reference layer 15 and the displacement elimination layer 13 are antiferromagnetically coupled through the spacer layer 14. That is, the reference layer 15, the displacement elimination layer 13, and the spacer layer 14 form a SAF (Synthetic Anti-Ferromagnetic) structure. The spacer layer 14 is formed of a ruthenium (Ru) layer or an iridium (Ir) layer.

[0019] The silicon-boron (SiB) layer 12 is a layer containing silicon (Si) and boron (B) and is disposed on the lower side of the displacement elimination layer 13. By providing the SiB layer 12, the perpendicular magnetic anisotropy of the displacement elimination layer 13 can be improved. Furthermore, by using the SiB layer 12, heat diffusion can be suppressed, resulting in a magnetoresistive element with excellent heat resistance. Moreover, in... Figure 1 In the example shown, a SiB layer 12 is provided on the lower surface of the displacement elimination layer 13, but a SiB layer 12 can also be provided on the upper surface of the displacement elimination layer 13, or a SiB layer 12 can be provided within the displacement elimination layer 13.

[0020] A buffer layer 11 is disposed below the SiB layer 12 and the displacement elimination layer 13. That is, the SiB layer 12 and the displacement elimination layer 13 are disposed on the buffer layer 11. The buffer layer 11 includes a first layer portion 11a and a second layer portion 11b disposed on the first layer portion 11a.

[0021] The first layer portion 11a has an amorphous structure and is formed of hafnium (Hf) or hafnium boron (HfB).

[0022] The second layer portion 11b is formed of at least one element selected from molybdenum (Mo), tungsten (W), and tantalum (Ta). That is, the second layer portion 11b can be a molybdenum (Mo) layer, a tungsten (W) layer, or a tantalum (Ta) layer. Alternatively, the second layer portion 11b can also be an alloy layer of two or more elements selected from molybdenum (Mo), tungsten (W), and tantalum (Ta). The second layer portion 11b has a BCC (body-centered cubic) crystal structure and has a (110) facet of the BCC crystal structure in a direction perpendicular to the stacking direction of the stacked structure 100. By using such a second layer portion 11b, the displacement elimination layer 13 can be well oriented in the FCC (111) facet or the HCP (0001) facet, and the perpendicular magnetic anisotropy of the displacement elimination layer 13 can be improved.

[0023] An oxide layer 18 is disposed on and in contact with the storage layer 17, and functions as a capping layer. The oxide layer 18 contains a predetermined element selected from rare earth elements (gadolinium (Gd), scandium (Sc), yttrium (Y), etc.), silicon (Si), and aluminum (Al). That is, the oxide layer 18 is formed of rare earth element oxides, silicon oxides, or aluminum oxides.

[0024] A molybdenum (Mo) layer 19 is disposed on and in contact with the oxide layer 18. The molybdenum (Mo) layer 19 is formed of molybdenum (Mo) and functions as a top layer.

[0025] The upper cover layer 20 is disposed on the molybdenum (Mo) layer 19 and is formed of a predetermined conductive material.

[0026] The magnetoresistive element constructed from the aforementioned stacked structure 100 is an STT (Spin Transfer Torque) type magnetoresistive element with perpendicular magnetization. That is, the magnetization directions of the storage layer 17, the reference layer 15, and the displacement elimination layer 13 are perpendicular to their respective film surfaces.

[0027] When the magnetization direction of the storage layer 17 is parallel to the magnetization direction of the reference layer 15, the magnetoresistive element is in a low-resistance state; when the magnetization direction of the storage layer 17 is antiparallel to the magnetization direction of the reference layer 15, the magnetoresistive element is in a high-resistance state. Therefore, the magnetoresistive element can store binary data based on its resistance state. Furthermore, the magnetoresistive element can be set to a low-resistance state or a high-resistance state depending on the direction of the current flowing into it.

[0028] As described above, in the magnetoresistive effect element of this embodiment, an oxide layer 18 containing a predetermined element selected from rare earth elements, silicon (Si), and aluminum (Al) is provided on the storage layer 17, and a molybdenum (Mo) layer 19 is provided on the oxide layer 18. With this structure, in this embodiment, as described below, a magnetoresistive effect element with excellent heat resistance and good characteristics can be obtained.

[0029] As described above, in this embodiment, an oxide layer 18 containing a predetermined element selected from rare earth elements, silicon (Si), and aluminum (Al) is provided on the storage layer 17. By using an oxide layer 18 containing such an element as a capping layer, the perpendicular magnetic anisotropy of the storage layer 17 can be improved. However, when an oxide layer 18 containing such an element is used as a capping layer, the element contained in the storage layer 17, especially iron (Fe), diffuses to the outside of the storage layer 17 during heat treatment, which may degrade the characteristics of the storage layer.

[0030] In this embodiment, a molybdenum (Mo) layer 19 is provided on the oxide layer 18 used as a capping layer. The diffusion of elements contained in the storage layer 17 can be suppressed by the molybdenum (Mo) layer 19, and thus the MR ratio of the storage layer can be improved by high-temperature heat treatment.

[0031] As described above, in this embodiment, the perpendicular magnetic anisotropy of the storage layer 17 can be improved, and the diffusion of elements (especially Fe) contained in the storage layer 17 during heat treatment can be suppressed. Therefore, in this embodiment, a magnetoresistive element with excellent heat resistance and good characteristics can be obtained.

[0032] (Implementation Method 2)

[0033] Figure 2 This is a schematic cross-sectional view showing the structure of the stacked magnetoresistive effect elements included in the magnetic storage device of the second embodiment. The basic aspects are the same as in the first embodiment, and the descriptions of aspects described in the first embodiment are omitted.

[0034] In this embodiment, the laminated structure 100 further includes a ruthenium (Ru) layer 21 disposed on the molybdenum (Mo) layer 19 and formed of ruthenium (Ru). That is, the laminated structure 100 also includes a ruthenium (Ru) layer 21 disposed on the opposite side of the oxide layer 18 relative to the molybdenum (Mo) layer 19. Other structures are similar to... Figure 1 The structure of the first embodiment shown is the same.

[0035] In this embodiment, the basic structure of the stacked structure 100 is the same as that in the first embodiment, and the same effects as those described in the first embodiment can be obtained.

[0036] Furthermore, in this embodiment, by providing a ruthenium (Ru) layer 21 on the molybdenum (Mo) layer 19, the resistance to the etching solution can be improved. For example, when the upper electrode connected to the stacked structure 100 is formed by etching, the lower layer of the ruthenium (Ru) layer 21 can be protected against the etching solution by the ruthenium (Ru) layer 21. Therefore, the deterioration of the characteristics of the magnetoresistive element constituted by the stacked structure 100 can be suppressed.

[0037] Furthermore, in this embodiment, the oxide layer 18 is not limited to an oxide layer containing a predetermined element selected from rare earth elements (gadolinium (Gd), scandium (Sc), yttrium (Y), etc.), silicon (Si), and aluminum (Al), and other oxide layers can also be used.

[0038] (Application example)

[0039] Figure 3 This is a perspective view schematically showing the structure of a magnetic storage device using the magnetoresistive effect element shown in the first and second embodiments described above.

[0040] Figure 3 The illustrated magnetic storage device includes a plurality of first wirings 210 extending in the X direction, a plurality of second wirings 220 extending in the Y direction intersecting the X direction, and a plurality of storage cells 230 connecting the plurality of first wirings 210 and the plurality of second wirings 220. For example, one of the first wirings 210 and the second wirings 220 corresponds to a word line, and the other corresponds to a bit line.

[0041] Each storage cell 230 includes a magnetoresistive element 240 and a selector (switching element) 250 connected in series with respect to the magnetoresistive element 240.

[0042] By applying a predetermined voltage between the first wiring 210 and the second wiring 220 connected to the desired memory cell 230, the selector 250 contained in the desired memory cell 230 becomes ON, enabling the reading or writing of the magnetoresistive element 240 contained in the desired memory cell 230.

[0043] also, Figure 3 The magnetic storage device shown has a structure in which the selector 250 is provided on the upper side of the magnetoresistive element 240, but it can also have a structure in which the selector 250 is provided on the lower side of the magnetoresistive element 240.

[0044] While certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. In fact, the novel embodiments described herein can be embodied in many other forms; moreover, various omissions, substitutions, and changes can be made to the forms of the embodiments described herein without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover such forms or modifications that fall within the scope and spirit of the invention.

Claims

1. A magnetic storage device having a stacked structure, the stacked structure comprising: The first magnetic layer has a fixed magnetization direction; The second magnetic layer has a variable magnetization direction; A non-magnetic layer is disposed between the first magnetic layer and the second magnetic layer; The molybdenum layer, or Mo layer, is disposed on the opposite side of the non-magnetic layer, relative to the second magnetic layer. An oxide layer is disposed between the second magnetic layer and the molybdenum layer (Mo layer); The ruthenium layer, i.e., the Ru layer, is disposed on the opposite side of the oxide layer, i.e., the molybdenum layer; A third magnetic layer is disposed on the opposite side of the non-magnetic layer relative to the first magnetic layer and eliminates the magnetic field applied from the first magnetic layer to the second magnetic layer; and A layer containing silicon (Si) and boron (B) is disposed on the opposite side of the first magnetic layer relative to the third magnetic layer.

2. The magnetic storage device according to claim 1, The second magnetic layer contains iron, i.e., Fe.

3. The magnetic storage device according to claim 1, The second magnetic layer contains iron (Fe), cobalt (Co), and boron (B).

4. The magnetic storage device according to claim 1, The first magnetic layer and the second magnetic layer are vertically magnetized.

5. The magnetic storage device according to claim 1, The first magnetic layer and the third magnetic layer are antiferromagnetically coupled.

6. The magnetic storage device according to claim 1, The stacked structure further includes a buffer layer disposed on the opposite side of the first magnetic layer relative to the third magnetic layer.

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