Magnetic storage device
By using rare earth elements and boron oxide layers adjacent to the storage layer in the magnetic storage device, the problems of increased storage layer thickness and write current are solved, resulting in higher thermal stability and lower write error rate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KIOXIA CORP
- Filing Date
- 2021-09-14
- Publication Date
- 2026-06-23
AI Technical Summary
Existing technologies struggle to reduce the saturation magnetization and thickness of the storage layer in magnetic storage devices while simultaneously preventing increased write current and decreased thermal stability, which can lead to write error rates and balling issues.
An oxide layer containing rare earth elements and boron is placed adjacent to the storage layer to improve the vertical magnetic anisotropy of the storage layer, improve wettability, reduce the thickness of the storage layer to suppress aggregation, and reduce write current and thermal stability.
It effectively reduces the saturation magnetization of the storage layer, reduces the increase in write current and the decrease in thermal stability, and improves the write error rate and balling problem of magnetoresistive elements.
Smart Images
Figure CN115117231B_ABST
Abstract
Description
[0001] This application is based on, and seeks the interest in, the entire contents of, Japanese Patent Application No. 2021-43842, 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 nonvolatile magnetic storage device is proposed that integrates multiple magnetoresistive effect elements on a semiconductor substrate. Summary of the Invention
[0004] In general, according to one embodiment, the magnetic storage device has a stacked structure comprising: a first magnetic layer having a variable magnetization direction; a second magnetic layer having a fixed magnetization direction; a non-magnetic layer disposed between the first magnetic layer and the second magnetic layer; and an oxide layer adjacent to the first magnetic layer, the first magnetic layer being disposed between the non-magnetic layer and the oxide layer, the oxide layer containing rare earth elements, boron (B), and oxygen (O). 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 diagram showing the improved characteristics of the magnetoresistive effect element according to the first embodiment.
[0007] Figure 3 This is a diagram showing the improved characteristics of the magnetoresistive effect element according to the first embodiment.
[0008] Figure 4 The graph shows the characteristics when the ratio of the concentration of boron (B) to the total concentration of rare earth elements and boron (B) in the oxide layer of the magnetoresistive effect element in the first embodiment is changed.
[0009] Figure 5 The graph shows the characteristics when the ratio of the concentration of boron (B) to the total concentration of rare earth elements and boron (B) in the oxide layer of the magnetoresistive effect element in the first embodiment is changed.
[0010] Figure 6This 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.
[0011] Figure 7 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
[0012] The embodiments will now be described with reference to the accompanying drawings.
[0013] (Implementation Method 1)
[0014] Figure 1 This 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.
[0015] The stacked structure 100 includes a storage layer (first magnetic layer) 11, a reference layer (second magnetic layer) 12, a tunnel barrier layer (nonmagnetic layer) 13, a displacement elimination layer (third magnetic layer) 14, a spacer layer 15, an oxide layer 16, a buffer layer 17, a top layer 18, and an upper capping layer 19.
[0016] The storage layer (first magnetic layer) 11 is a ferromagnetic layer with a variable magnetization direction. Furthermore, the variable magnetization direction means that the magnetization direction changes relative to a predetermined write current. The storage layer 11 is formed of an FeCoB layer containing iron (Fe), cobalt (Co), and boron (B).
[0017] The reference layer (second magnetic layer) 12 is a ferromagnetic layer with a fixed magnetization direction. Furthermore, a fixed magnetization direction means that the magnetization direction remains unchanged relative to a predetermined write current. The reference layer 12 includes a first layer portion 12a and a second layer portion 12b. The first layer portion 12a is formed of an FeCoB layer containing iron (Fe), cobalt (Co), and boron (B). The second layer portion 12b contains at least one element selected from cobalt (Co), platinum (Pt), nickel (Ni), and palladium (Pd).
[0018] The tunnel barrier layer (non-magnetic layer) 13 is an insulating layer disposed between the storage layer 11 and the reference layer 12. The tunnel barrier layer 13 is formed of an MgO layer containing magnesium (Mg) and oxygen (O).
[0019] The displacement elimination layer (third magnetic layer) 14 is a ferromagnetic layer having a fixed magnetization direction that is antiparallel to the magnetization direction of the reference layer 12, and has the function of eliminating the magnetic field applied from the reference layer 12 to the storage layer 11. The displacement elimination layer 14 contains at least one element selected from cobalt (Co), platinum (Pt), nickel (Ni) and palladium (Pd).
[0020] A spacer layer 15 is disposed between the reference layer 12 and the displacement elimination layer 14, through which the reference layer 12 and the displacement elimination layer 14 are antiferromagnetically coupled. That is, the reference layer 12, the displacement elimination layer 14, and the spacer layer 15 form a SAF (Synthetic Anti-Ferromagnetic) structure. The spacer layer 15 is formed of a ruthenium (Ru) layer or an iridium (Ir) layer.
[0021] The oxide layer 16 is disposed adjacent to the storage layer 11, with the storage layer 11 located between the tunnel barrier layer 13 and the oxide layer 16. More specifically, the oxide layer 16 is disposed on the upper side of the storage layer 11 and is in contact with it. The oxide layer 16 contains rare earth elements (gadolinium (Gd), scandium (Sc), yttrium (Y), etc.), boron (B), and oxygen (O). The oxide layer 16 also functions as a capping layer.
[0022] The buffer layer 17 is disposed on the lower side of the displacement elimination layer 14 and is formed of a predetermined conductive material.
[0023] The top layer 18 is disposed on the upper side of the oxide layer 16 and is formed of a predetermined conductive material such as ruthenium (Ru) or tantalum (Ta).
[0024] The upper cover layer 19 is disposed on the upper side of the top layer 18 and is formed of a predetermined conductive material.
[0025] The magnetoresistive element constructed from the aforementioned stacked structure 100 is an STT (SpinTransfer Torque) type magnetoresistive element with perpendicular magnetization. That is, the magnetization directions of the storage layer 11, the reference layer 12, and the displacement elimination layer 14 are perpendicular to their respective film surfaces.
[0026] When the magnetization direction of the storage layer 11 is parallel to the magnetization direction of the reference layer 12, the magnetoresistive element is in a relatively low-resistance state; when the magnetization direction of the storage layer 11 is antiparallel to the magnetization direction of the reference layer 12, the magnetoresistive element is in a relatively 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.
[0027] As described above, in this embodiment, the oxide layer 16 containing rare earth elements, boron (B), and oxygen (O) is disposed adjacent to the storage layer 11. Therefore, as described below, a magnetoresistive element with excellent characteristics can be obtained.
[0028] Generally, reducing the saturation magnetization (Mst) of the storage layer (Ms) and its thickness (t) is effective in improving the write error rate (WER) and ballooning of magnetoresistive elements. Ballooning refers to the poor write performance caused by the formation of magnetic regions (domains) in the storage layer during writing, which stabilize by becoming closed magnetic circuits, thus hindering the reversal of magnetization. However, if the storage layer thickness falls below a certain threshold, agglomeration of particles within the storage layer occurs. This results in deterioration of the wettability of the storage layer interface and an increase in surface roughness. Due to this agglomeration, it becomes difficult to reduce the storage layer thickness (t).
[0029] Therefore, in order to reduce the mean current (Mst) of the memory layer, memory layers rich in boron (B) or containing non-magnetic elements such as molybdenum (Mo) are generally used. However, in this case, problems arise such as an increase in write current (Ic) and a decrease in thermal stability (Δ).
[0030] Therefore, it is important to reduce the Mst of the storage layer while suppressing the increase of write current Ic and the decrease of thermal stability Δ.
[0031] In this embodiment, as described above, the oxide layer 16 contains rare earth elements and boron. By containing rare earth elements in the oxide layer 16, the perpendicular magnetic anisotropy of the storage layer 11 can be improved. Furthermore, by containing boron in the oxide layer 16, the wettability between the storage layer 11 and the oxide layer 16, which functions as a capping layer, can be improved, thereby suppressing aggregation and reducing the thickness t of the storage layer 11. For these reasons, in this embodiment, the Mst of the storage layer 11 can be reduced while suppressing the increase in write current Ic and the decrease in thermal stability Δ.
[0032] Figure 2 and Figure 3 This is a graph illustrating the improved characteristics of the magnetoresistive effect element according to this embodiment.
[0033] also, Figure 2 The horizontal axis represents the Mst of storage layer 11. Figure 2 The vertical axis represents the coercive force Hc of storage layer 11. Figure 3 The horizontal axis represents the product of the Mst of storage layer 11 and the anisotropic magnetic field Hk (corresponding to thermal stability Δ). Figure 3 The vertical axis represents the coercivity Hc of the storage layer 11. This coercivity Hc is a parameter that increases or decreases relative to the formation of defects and the increase in roughness of the storage layer caused by aggregation. If aggregation progresses due to the thinning of the storage layer, the coercivity Hc also increases monotonically. Therefore, in order to reduce the Mst of the storage layer, it is important to suppress the increase of coercivity Hc (suppress aggregation).
[0034] In addition, Figure 2 and Figure 3 In the figures, (a) shows the characteristics when the oxide layer of this embodiment (an oxide layer containing rare earth elements and boron) is used, (b) shows the characteristics when the oxide layer of the first comparative example (an oxide layer containing rare earth elements but not boron) is used, and (c) shows the characteristics when the oxide layer of the second comparative example (an oxide layer containing hafnium (Hf)) is used. Furthermore, the oxide layer of this embodiment contains gadolinium (Gd) as a rare earth element.
[0035] from Figure 2 and Figure 3 As can be seen, in this embodiment, the coercivity Hc is reduced compared to the first and second comparative examples. Therefore, by using the oxide layer of this embodiment, the improved properties described above can be obtained.
[0036] As described above, in this embodiment, since the oxide layer 16 containing rare earth elements, boron (B) and oxygen (O) is disposed adjacent to the storage layer 11, it is possible to suppress the increase of write current Ic and the decrease of thermal stability Δ while reducing the Mst of the storage layer, thereby improving the WER and spheroidization of the magnetoresistive effect element.
[0037] Figure 4 and Figure 5 This is a graph showing the characteristics of the oxide layer (an oxide layer containing rare earth elements and boron) in this embodiment when the ratio R of the boron concentration to the total concentration of rare earth elements and boron is changed.
[0038] also, Figure 4 The horizontal axis represents the Mst of storage layer 11. Figure 4 The vertical axis represents the coercivity Hc of storage layer 11. Figure 5 The horizontal axis represents the product of the Mst of storage layer 11 and the anisotropic magnetic field Hk (corresponding to thermal stability Δ). Figure 5 The vertical axis represents the coercivity Hc of storage layer 11.
[0039] In addition, Figure 4 and Figure 5 In (a), R = 0%; in (b), R = 10%; in (c), R = 20%; and in (d), R = 50%. Furthermore, regardless of whether it is (a), (b), (c), or (d), the oxide layer contains gadolinium (Gd) as a rare earth element.
[0040] like Figure 4 and Figure 5 As shown, compared to (a) and (b), the coercivity Hc decreases in (c) and (d). Furthermore, there is no significant difference in coercivity Hc in (c) and (d). Therefore, it can be considered that if the ratio R is 20% or higher, sufficient wettability to suppress aggregation can be obtained at the interface between the storage layer and the oxide layer, and it can be considered that the aforementioned... Figure 2 and Figure 3 The same effect. Therefore, the ratio R of boron concentration to the total concentration of rare earth elements and boron concentration is preferably 20% or more.
[0041] (Implementation Method 2)
[0042] Figure 6 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. Furthermore, the basic aspects are the same as in the first embodiment described above, and explanations of aspects described in the first embodiment are omitted.
[0043] In the first embodiment, a top-free type magnetoresistive effect element with the storage layer 11 located on the upper side of the reference layer 12 was used. However, in this embodiment, a bottom-free type magnetoresistive effect element with the storage layer 11 located on the lower side of the reference layer 12 is used.
[0044] In this embodiment, similar to the first embodiment, the oxide layer 16 is disposed adjacent to the storage layer 11, and the storage layer 11 is disposed between the tunnel barrier layer 13 and the oxide layer 16. More specifically, the oxide layer 16 is disposed on the lower side of the storage layer 11 and is in contact with the storage layer 11. In addition, similar to the first embodiment, the oxide layer 16 contains rare earth elements (gadolinium (Gd), scandium (Sc), yttrium (Y), etc.), boron (B), and oxygen (O).
[0045] In addition, a displacement elimination layer 14 is provided on the upper side of the reference layer 12, and a capping layer 20 is provided on the upper side of the displacement elimination layer 14. The capping layer 20 may use the same material as the oxide layer 16 shown in the first embodiment, or it may use a different material.
[0046] In this embodiment, the oxide layer 16 containing rare earth elements, boron (B) and oxygen (O) is also disposed adjacent to the storage layer 11. Therefore, similar to the first embodiment, it is possible to suppress the increase of write current Ic and the decrease of thermal stability Δ while reducing the Mst of the storage layer, thereby improving the WER and spheroidization of the magnetoresistive effect element.
[0047] (Application Example)
[0048] Figure 7 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.
[0049] Figure 7 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.
[0050] 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.
[0051] 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.
[0052] also, Figure 7 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.
[0053] 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 variable magnetization direction; The second magnetic layer has a fixed magnetization direction; A non-magnetic layer is disposed between the first magnetic layer and the second magnetic layer; and An oxide layer, adjacent to the first magnetic layer, The first magnetic layer is disposed between the non-magnetic layer and the oxide layer. The oxide layer contains rare earth elements, boron (B), and oxygen (O). The rare earth elements mentioned are gadolinium (Gd) or yttrium (Y). The concentration of boron (B) in the oxide layer is at least 20% relative to the total concentration of gadolinium (Gd) or yttrium (Y) and boron (B).
2. The magnetic storage device according to claim 1, The first magnetic layer contains iron (Fe), cobalt (Co), and boron (B).
3. The magnetic storage device according to claim 1, The first magnetic layer and the second magnetic layer are vertically magnetized.
4. The magnetic storage device according to claim 1, The stacked structure further includes a third magnetic layer that eliminates the magnetic field applied from the second magnetic layer to the first magnetic layer.
5. The magnetic storage device according to claim 4, The second magnetic layer and the third magnetic layer are antiferromagnetically coupled.
6. The magnetic storage device according to claim 1, The first magnetic layer is located on the upper side than the second magnetic layer.
7. The magnetic storage device according to claim 1, The first magnetic layer is located on the lower side than the second magnetic layer.
8. The magnetic storage device according to claim 1, The non-magnetic layer contains magnesium (Mg) and oxygen (O).
9. The magnetic storage device according to claim 1, The oxide layer is in contact with the first magnetic layer.
10. The magnetic storage device according to claim 1, The stacked structure is contained within a magnetoresistive effect element.
11. The magnetic storage device according to claim 10, It also includes a switching element connected in series with the magnetoresistive effect element.