Highly conductive ruthenium metal thin films and methods of making the same

Abstract

The present invention relates to a high-conductivity ruthenium metal thin film and a method of making the same. According to one embodiment, a method of forming a ruthenium metal thin film can include epitaxially or orientally growing a ruthenium metal layer on a substrate having a perovskite crystal structure using metallic ruthenium or ruthenium oxide as a growth source or target. The surface of the substrate can be a (110) crystal plane, the formed ruthenium metal layer can be a single-crystal ruthenium metal layer, and the surface thereof can be a (002) crystal plane. The substrate can include LaAlO3.

Description

Technical Field

[0001] This invention relates generally to the field of materials, and more particularly to a high-conductivity ruthenium metal thin film and its preparation method. Background Technology

[0002] Ruthenium, one of the six platinum group metals, possesses low resistivity and good chemical stability. It also exhibits excellent catalytic activity, making it widely used in electronics, electrochemistry, and other fields. Besides catalysis, ruthenium thin films are widely used in semiconductor devices in the electronics industry, serving as a copper bonding layer / diffusion barrier layer in integrated circuits, an intermediate layer / seed layer in magnetic recording media, and also finding broad applications in antioxidant protective layers and electrical contact materials.

[0003] At room temperature, metallic ruthenium has a close-packed hexagonal structure with lattice parameters a = b = 270.59 pm, c = 428.15 pm, axial angles α = β = 90°, and γ = 120°. Ruthenium has a high melting point of approximately 2310°C, requiring deposition at high temperatures. It is typically deposited on substrates such as Si, glass, Al₂O₃, and TiO₂, yielding amorphous and polycrystalline samples, making it difficult to obtain metallic ruthenium with a good single-crystal morphology. Summary of the Invention

[0004] This invention provides a method for preparing ruthenium metal thin films, which can produce high-quality single-crystal ruthenium metal thin films with high electrical conductivity, suitable for use in various applications.

[0005] One aspect of the present invention provides a method for forming a ruthenium metal thin film, comprising using metallic ruthenium or ruthenium oxide as a growth source or target to epitaxially or orientally grow a ruthenium metal layer on a substrate having a perovskite crystal structure.

[0006] In some embodiments, the ruthenium metal layer is a single-crystal ruthenium metal layer.

[0007] In some embodiments, the surface of the substrate having a perovskite crystal structure is a (110) crystal plane, and the surface of the single-crystal ruthenium metal layer is a (002) crystal plane.

[0008] In some embodiments, the substrate having a perovskite crystal structure comprises LaAlO3.

[0009] In some embodiments, the lattice matching degree between the substrate having a perovskite crystal structure and the single-crystal ruthenium metal layer is within the range of ±3%.

[0010] In some embodiments, the ruthenium metal layer has a room temperature resistivity of less than 20 μΩcm, preferably less than 10 μΩcm.

[0011] In some embodiments, the method further includes using argon, nitrogen, or oxygen as a carrier gas when epitaxially or orientedly growing a ruthenium metal layer.

[0012] In some embodiments, the gas pressure during epitaxial or oriented growth of a ruthenium metal layer on a substrate having a perovskite crystal structure is below 1 Pa, and the temperature is in the range of 250-750°C.

[0013] In some embodiments, a physical vapor deposition process is used to epitaxially or orientally grow the ruthenium metal layer, the physical vapor deposition process including magnetron sputtering, pulsed laser deposition, or ion beam sputtering.

[0014] Another aspect of the present invention provides a single-crystal ruthenium metal layer, which is prepared according to the above method.

[0015] The above and other features and advantages of the present invention will become apparent from the following description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 A crystal structure diagram of a substrate for preparing a ruthenium metal thin film according to an embodiment of the present invention is shown.

[0017] Figure 2 The X-ray diffraction pattern of a ruthenium metal thin film prepared according to an embodiment of the present invention is shown.

[0018] Figure 3 A scanning tunneling microscope image of a ruthenium metal thin film prepared according to an embodiment of the present invention is shown.

[0019] Figure 4 A graph showing the resistivity of a ruthenium metal thin film prepared according to an embodiment of the present invention as a function of temperature is shown. Detailed Implementation

[0020] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Note that the drawings may not be drawn to scale. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments of this application, and this application is not limited to the exemplary embodiments described herein.

[0021] This invention proposes a method for preparing single-crystal ruthenium metal thin films. The method utilizes a substrate with a perovskite crystal structure to form a ruthenium metal thin film via thin-film physical vapor deposition. This method can produce high-quality single-crystal ruthenium metal thin films with excellent surface uniformity, continuity, and density. Due to the superior crystal quality, the resulting ruthenium metal thin films exhibit high electrical conductivity, making them suitable for various applications.

[0022] Figure 1A schematic diagram showing the crystal structure of perovskite. Perovskite originally referred to CaTiO3, which has... Figure 1 The diagram shows a cubic crystal structure. Many materials that can be represented by the chemical formula ABO3 also have this crystal structure, and therefore they are all called perovskite crystal structures, where A atoms occupy the vertex positions of the cube, B atoms occupy the body center positions of the cube, and O atoms occupy the face centers positions of the cube.

[0023] In embodiments of the present invention, a material with a perovskite crystal structure is used as a substrate, on which a ruthenium metal layer is formed. As described above, the substrate material can be represented by ABO3, where A includes rare earth or alkaline earth metals, and B includes transition metals or Al. Although Al belongs to Group IIIA elements, it is sometimes considered a transition metal. A suitable substrate material, ABO3, can be selected such that the lattice matching degree between the substrate and the single-crystal ruthenium metal layer is within ±5%, more preferably within ±3%. In some embodiments, the substrate can be LaAlO3 crystal.

[0024] In some embodiments, the (110) crystal plane of a substrate having a perovskite crystal structure can be used as a growth surface for growing a single-crystal ruthenium thin film. For example, a single-crystal ruthenium thin film can be grown on the (110) crystal plane of a LaAlO3 crystal.

[0025] Methods for growing single-crystal ruthenium thin films can include various thin-film physical vapor deposition methods, such as, but not limited to, magnetron sputtering, pulsed laser deposition, and ion beam sputtering. Since these processes are well-known in the relevant fields, they will not be described in detail here. In these processes, metallic ruthenium or ruthenium oxide materials can be used as the growth source or target. It should be understood that although ruthenium oxide is used as the target, due to the excellent chemical stability of ruthenium and its resistance to oxidation, and by selecting an appropriate substrate, a metallic ruthenium thin film, rather than a ruthenium dioxide thin film, can still be formed.

[0026] When epitaxially or orientally growing ruthenium metal thin films on a substrate using the above-described physical vapor deposition process, a vacuum can be first applied, followed by the introduction of a carrier gas, and the deposition process can be performed at a predetermined pressure. For example, commonly used argon or nitrogen can be used as the carrier gas, or oxygen can also be used. Due to the excellent chemical stability of ruthenium, ruthenium dioxide thin films will not form even when using a small amount of oxygen as the carrier gas. The carrier gas pressure can be below 1 Pa, for example, 100 mTorr, 200 mTorr, or 500 mTorr. The growth temperature can be in the range of 250-750 °C, preferably in the range of 300-700 °C.

[0027] It is understandable that selecting an appropriate substrate is crucial for film quality. However, in addition to lattice matching, other factors are also very important, such as the flatness of the growth crystal plane and the affinity of the growth interface. This invention utilizes perovskite crystal substrates, especially LaAlO3 substrates, and uses the (110) crystal plane as the growth surface to obtain high-quality single-crystal ruthenium metal thin films. Figure 2 The X-ray diffraction (XRD) curves of a ruthenium metal thin film grown on the (110) crystal plane of a LaAlO3 substrate are shown. The growth process was magnetron sputtering, with ruthenium dioxide as the target, argon as the carrier gas, a pressure of 200 mTorr, and a temperature of approximately 420 degrees Celsius. Figure 2 It can be seen that the XRD curve of the obtained sample has only one Ru(002) peak, indicating that a high-quality single crystal or a highly oriented ruthenium metal layer was obtained without defects or impurity phases. Figure 3 This is a scanning tunneling microscope image of the sample, which clearly shows a high-quality single-crystal ruthenium thin film formed on the substrate. The film has a highly uniform orientation structure, with the surface of the ruthenium film being a (002) crystal plane. Figure 3 As shown, the formed single-crystal ruthenium thin film is a continuous single-crystal structure with good consistency and density, which is far superior to the film quality in the prior art.

[0028] Figure 4 It shows the Figure 3 The resistivity curve of the sample shown is a temperature-dependent measurement obtained from the sample. Figure 4 Experimental data show that the resistivity of single-crystal ruthenium metal films at room temperature is below 10 μΩcm, approximately 9.7 μΩcm, which is better than the room-temperature resistivity of Pt metal (10.1 μΩcm). This indicates that ruthenium films with good single-crystal structures have lower resistivity. It is understandable that when different substrate materials are chosen, the single-crystal quality of the formed ruthenium metal films will vary due to differences in lattice matching, thus causing fluctuations in resistivity, which may exceed 10 μΩcm. However, generally speaking, the resistivity of ruthenium metal films formed on perovskite crystal structure substrates is below 20 μΩcm.

[0029] As described above, the present invention can form ruthenium thin films with good single-crystal structures. In addition to its wide application in traditional fields such as electronic information and electrochemistry, high-quality epitaxial single-crystal ruthenium metal films grown on perovskite substrates also have wide applications in oxide electronics and spintronics. In particular, it has significant basic research and industrial application value in fields such as thin-film resistors, ferroelectric random access memory, dynamic random access memory, magnetic tunnel junctions, organic thin-film transistors, magnetic thermoelectric devices such as spin Seebeck effect devices, supercapacitors, electrochemical electrolyzers, photoelectric water splitting, and fuel cell electrodes.

[0030] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0031] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0032] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0033] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0034] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for forming a ruthenium metal thin film, comprising using metallic ruthenium or ruthenium oxide as a growth source or target, and epitaxially or orientally growing a single-crystal ruthenium metal layer on a substrate having a perovskite crystal structure. in, The surface of the substrate with the perovskite crystal structure is a (110) crystal plane, and the surface of the single crystal ruthenium metal layer is a (002) crystal plane.

2. The method as described in claim 1, wherein, The substrate having a perovskite crystal structure includes LaAlO3.

3. The method of claim 1, wherein, The lattice matching degree between the substrate with the perovskite crystal structure and the single-crystal ruthenium metal layer is within the range of ±3%.

4. The method of claim 1, wherein, The ruthenium metal layer has a room temperature resistivity of less than 20 μΩcm.

5. The method of claim 4, wherein, The ruthenium metal layer has a room temperature resistivity of less than 10 μΩcm.

6. The method of claim 1, further comprising: Argon, nitrogen, or oxygen are used as carrier gases when epitaxially or orientedly growing ruthenium metal layers.

7. The method of claim 1, wherein, The gas pressure for epitaxial or oriented growth of ruthenium metal layers on substrates with perovskite crystal structures is below 1 Pa, and the temperature is in the range of 250-750℃.

8. The method of claim 1, wherein, The ruthenium metal layer is epitaxially or oriented using a physical vapor deposition process, including magnetron sputtering, pulsed laser deposition, or ion beam sputtering.

9. A single-crystal ruthenium metal layer formed according to the method of any one of claims 1 to 8.

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