CN116791201A - High conductivity ruthenium metal film and preparation method thereof - Google Patents

Abstract

The invention relates to a high conductivity ruthenium metal film and a preparation method thereof. According to an embodiment, a method of forming a ruthenium metal film may include using metallic ruthenium or ruthenium oxide as a growth source or target material to epitaxially or directionally grow a ruthenium metal layer on a substrate having a perovskite crystal structure. The surface of the substrate may be a (110) crystal plane, the formed ruthenium metal layer is a single crystal ruthenium metal layer, and its surface is a (002) crystal plane. The substrate may include LaAlO ₃ .

Description

High conductivity ruthenium metal film and preparation method thereof

Technical field

The present invention generally relates to the field of materials, and more particularly, to a high conductivity ruthenium metal film and a preparation method thereof.

Background technique

Ruthenium is one of the six platinum group metals. It has low resistivity and good chemical stability. At the same time, ruthenium has excellent catalytic activity, so it is widely used in electronic information, electrochemistry and other fields. In addition to its catalytic effect, ruthenium metal thin films are widely used in semiconductor devices in the electronic information industry. They are used as copper bonding layers/diffusion barrier layers in integrated circuits and as intermediate layers/seed layers in magnetic recording media. In addition, It has a wide range of applications in anti-oxidation protective layer materials and electrical contact materials.

Metal ruthenium has a close-packed hexagonal structure at room temperature. The lattice parameters are a=b=270.59pm, c=428.15pm, and the axis angles α=β=90° and γ=120°. The melting point of ruthenium is as high as about 2310°C, and it needs to be deposited at a higher temperature. It is generally deposited on Si, glass, Al ₂ O ₃ , TiO ₂ and other substrates. Amorphous and polycrystalline samples are obtained, and it is difficult to obtain samples with Ruthenium metal in good single crystal form.

Contents of the invention

The present invention provides a method for preparing a ruthenium metal film, which can prepare a high-quality single crystal ruthenium metal film. The obtained ruthenium film has high electrical conductivity and is suitable for use in various applications.

One aspect of the present invention provides a method for forming a ruthenium metal film, which includes using metal ruthenium or ruthenium oxide as a growth source or target material to epitaxially or directionally grow a ruthenium metal layer on a substrate with a perovskite crystal structure.

In some embodiments, the ruthenium metal layer is a single crystal ruthenium metal layer

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.

In some embodiments, the substrate having a perovskite crystal structure includes LaAlO3.

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

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

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

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

In some embodiments, the ruthenium metal layer is epitaxially or orientationally grown using a physical vapor deposition process, including magnetron sputtering, pulsed laser deposition, or ion beam sputtering.

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

The above and other features and advantages of the present invention will become apparent from the following description of specific embodiments taken in conjunction with the accompanying drawings.

Description of the drawings

FIG. 1 shows a crystal structure diagram of a substrate for preparing a ruthenium metal film according to an embodiment of the present invention.

Figure 2 shows an X-ray diffraction curve of a ruthenium metal film prepared according to an embodiment of the present invention.

Figure 3 shows a scanning tunneling microscope photograph of a ruthenium metal film prepared according to an embodiment of the present invention.

FIG. 4 shows a graph of the resistivity of a ruthenium metal film prepared according to an embodiment of the present invention as a function of temperature.

Detailed ways

Hereinafter, example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Note that the figures may not be drawn to scale. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application, and the present application is not limited by the example embodiments described here.

The present invention proposes a method for preparing a single crystal ruthenium metal film, which uses a substrate with a perovskite crystal structure to form a ruthenium metal film on the substrate through a thin film physical vapor deposition method. The method of the present invention can prepare high-quality single crystal ruthenium metal films. The obtained ruthenium metal films have good surface uniformity, continuity and density. Due to the excellent crystal quality, the obtained ruthenium metal films have high electrical conductivity. Therefore suitable for use in a variety of applications.

Figure 1 shows a schematic diagram of the perovskite crystal structure. Perovskite originally refers to CaTiO ₃ , which has a cubic crystal structure as shown in Figure 1. Many materials that can be represented by the chemical formula ABO ₃ also have this crystal structure, so they are all called perovskite crystal structures, in which A atoms occupy the vertex position of the cube, B atoms occupy the body center position of the cube, and O atoms occupy the cube The center position of the face.

In embodiments of the present invention, a material with a perovskite crystal structure is used as a substrate, and a ruthenium metal layer is formed thereon. As mentioned above, the substrate material can be represented by ABO ₃ , 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 regarded as a transition metal. An appropriate substrate material ABO ₃ can be selected so 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 may be _LaAlO crystal.

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 film. For example, a single crystal ruthenium film can be grown on the (110) crystal plane of _LaAlO3 crystal.

The method of growing a single crystal ruthenium film may include various thin film physical vapor deposition methods, such as but not limited to magnetron sputtering, pulsed laser deposition, ion beam sputtering, etc. Since these processes are all known in the relevant fields, they will not be discussed here. Describe in detail one by one. In these processes, metallic ruthenium or ruthenium oxide materials can be used as growth sources or targets. It should be understood that although ruthenium oxide is used as the target material, because the ruthenium element has excellent chemical stability and is not easily oxidized, and by selecting an appropriate substrate, a metal ruthenium film instead of a ruthenium dioxide film can still be formed.

When using the above-mentioned physical vapor deposition process to epitaxially or directionally grow a ruthenium metal film on a substrate, a vacuum can be first evacuated, and then a carrier gas can be introduced to perform the deposition process under a predetermined gas pressure. For example, commonly used argon or nitrogen can be used as the carrier gas, or oxygen can also be used as the carrier gas. Due to the excellent chemical stability of the ruthenium element, a ruthenium dioxide film will not be formed when a small amount of oxygen is used as the carrier gas. The pressure of the carrier gas may be below 1 Pa, for example, 100 mTorr, 200 mTorr or 500 mTorr. The growth temperature may be in the range of 250-750°C, preferably in the range of 300-700°C.

It can be understood that selecting an appropriate substrate is very important for film formation quality. However, in addition to lattice matching, there are some other factors that are also very important, such as the flatness of the growth crystal plane, the affinity of the growth interface and other factors. The present invention uses a perovskite crystal substrate, especially a LaAlO ₃ substrate, and uses the (110) crystal plane as the growth surface to obtain a high-quality single-crystal structure ruthenium metal film. Figure 2 shows the X-ray diffraction (XRD) curve of the ruthenium metal film grown on the (110) crystal plane of the LaAlO ₃ substrate. The growth process is magnetron sputtering, the target material is ruthenium dioxide, and the carrier gas Argon gas is used, the pressure is 200mTorr, and the temperature is about 420 degrees Celsius. As can be seen from Figure 2, the XRD curve of the obtained sample has only one Ru(002) peak, indicating that a good quality single crystal or highly oriented ruthenium metal layer was obtained without defects or impurity phases. Figure 3 is a scanning tunneling microscope photo of the sample, which clearly shows the high-quality single-crystal ruthenium film formed on the substrate. The film has a highly consistent orientation structure, in which the surface of the ruthenium film is the (002) crystal plane. . As shown in Figure 3, the formed single crystal ruthenium film has a continuous single crystal structure, has good consistency and density, and is far superior to the film formation quality in the existing technology.

Figure 4 shows the measured resistivity as a function of temperature for the sample shown in Figure 3. It can be seen from the experimental data in Figure 4 that the resistivity of the single crystal ruthenium metal film at room temperature is below 10 μΩcm, about 9.7 μΩcm, which is better than the room temperature resistivity of Pt metal, which is 10.1 μΩcm. This shows that the ruthenium film with good single crystal structure has smaller resistivity. It can be understood that when different substrate materials are selected, due to differences in lattice matching, the single crystal quality of the formed ruthenium metal film will also be different, so the resistivity of the ruthenium metal film will fluctuate, such as It may exceed 10μΩcm, but generally speaking, the resistivity of ruthenium metal films formed on substrates with a perovskite crystal structure is below 20μΩcm.

As mentioned above, the present invention can form a metal ruthenium film with a good single crystal structure. In addition to being widely used in traditional electronic information, electrochemistry and other fields, the present invention can also form high-quality epitaxial single crystals grown on perovskite substrates. Ruthenium metal films are also widely used in oxide electronics and spin electronics, especially thin film resistors, ferroelectric random access memories, dynamic random access memories, magnetic tunnel junctions, organic thin film transistors, and magnetic thermoelectric devices such as the spin Seebeck effect. Devices, supercapacitors, electrochemical electrolysis cells, photoelectrolysis of water, and fuel cell electrodes all have significant basic research and industrial application value.

The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, advantages, effects, etc. mentioned in this application are only examples and not limitations. These advantages, advantages, effects, etc. cannot be considered to be Each embodiment of this application must have. In addition, the specific details disclosed above are only for the purpose of illustration and to facilitate understanding, and are not limiting. The above details do not limit the application to be implemented using the above specific details.

The block diagrams of the devices, devices, equipment, and systems involved in this application are only 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, devices, equipment, and systems may be connected, arranged, and configured in any manner. Words such as "includes," "includes," "having," etc. are open-ended terms that mean "including, but not limited to," and may be used interchangeably therewith. As used herein, the words "or" and "and" refer to the words "and/or" and are used interchangeably therewith unless the context clearly dictates otherwise. As used herein, the word "such as" refers to the phrase "such as, but not limited to," and may be used interchangeably therewith.

It should also be pointed out that in the device, equipment and method of the present application, each component or each step can be decomposed and/or recombined. These decompositions and/or recombinations shall be considered equivalent versions of this application.

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

The foregoing description has been presented for the purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the form disclosed herein. Although various example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims (10)

1. A method of forming a ruthenium metal film, including using metal ruthenium or ruthenium oxide as a growth source or target material, and epitaxially or directionally growing a ruthenium metal layer on a substrate with a perovskite crystal structure. 2. The method of claim 1, wherein the ruthenium metal layer is a single crystal ruthenium metal layer. 3. The method of claim 2, wherein 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. 4. The method of claim 1, wherein the substrate having a perovskite crystal structure includes _LaAlO3 . 5. The method of claim 1, wherein a lattice matching degree of the substrate having a perovskite crystal structure and the single crystal ruthenium metal layer is within a range of ±3%. 6. The method of claim 1, wherein the ruthenium metal layer has a room temperature resistivity of less than 20 μΩcm, preferably less than 10 μΩcm. 7. The method of claim 1, further comprising: When epitaxially or directionally growing a ruthenium metal layer, argon, nitrogen or oxygen is used as a carrier gas. 8. The method of claim 1, wherein the gas pressure during the epitaxial or directional growth of the ruthenium metal layer on the substrate having a perovskite crystal structure is below 1 Pa, and the temperature is in the range of 250-750°C. 9. The method of claim 1, wherein the ruthenium metal layer is epitaxially or orientationally grown using a physical vapor deposition process, including magnetron sputtering, pulsed laser deposition, or ion beam sputtering. 10. A single crystal ruthenium metal layer formed according to the method of any one of claims 1 to 9.