Body-centered cubic tantalum film and preparation method and application thereof

Abstract

The present invention provides a body-centered cubic tantalum film and a preparation method and application thereof, belonging to the technical field of magnetron sputtering coating. <111> The body-centered cubic tantalum film of the present invention has <111> Crystal orientation, compared to <110> Oriented films have fewer crystal domains and line defects.

Description

Technical Field

[0001] The invention relates to the technical field of magnetron sputtering coating, and in particular to a body-centered cubic lattice tantalum film and a preparation method and application thereof. Background Art

[0002] Epitaxial coating helps to obtain high-quality single-crystal thin films. Conventional epitaxial coating methods include: molecular beam epitaxial coating, plasma enhanced chemical vapor deposition, organic metal chemical vapor deposition, thermal evaporation, etc. Epitaxial coating methods for metal films mainly include: thermal evaporation, electron beam evaporation, magnetron sputtering coating and other physical coating methods.

[0003] Tantalum metal coating is usually done by magnetron sputtering. Common tantalum films include body-centered cubic tantalum films (α-Ta) and tetragonal tantalum films (β-Ta). At present, most of the body-centered cubic tantalum films prepared by common magnetron sputtering epitaxial coating are <110> Crystal direction. <110> From the crystal downward, there are many crystal domains and internal defects inside the tantalum film. Summary of the invention

[0004] In view of this, in order to solve at least one of the above-mentioned technical problems, the present invention provides a body-centered cubic lattice tantalum film and a preparation method and application thereof.

[0005] According to an embodiment of one aspect of the present invention, a body-centered cubic tantalum film is provided. The body-centered cubic tantalum film has <111> Crystal orientation of epitaxial tantalum films.

[0006] According to some embodiments of the present invention, the (110) crystal plane of the body-centered cubic tantalum film is relative to <111> The crystal orientation has three-fold rotational symmetry.

[0007] According to some embodiments of the present invention, the thickness of the body-centered cubic tantalum film is 100-200 nm; the X-ray diffraction spectrum of the body-centered cubic tantalum film has a characteristic peak at 108.4° with an error of ±0.2°.

[0008] According to some embodiments of the present invention, there is no lattice defect in the internal lattice of the body-centered cubic tantalum film, and there is no obvious crystal domain distribution on the surface of the body-centered cubic tantalum film.

[0009] According to an embodiment of another aspect of the present invention, a method for preparing a body-centered cubic lattice tantalum film as described above is provided, comprising: sequentially performing chemical solution cleaning and oxygen plasma cleaning on an initial substrate to obtain a substrate; using a tantalum target to prepare a body-centered cubic lattice tantalum film on the substrate by magnetron sputtering; wherein the coating temperature of the magnetron sputtering is 700~950°C.

[0010] According to some embodiments of the present invention, before preparing the body-centered cubic tantalum film, the substrate is annealed at a temperature of 650-950° C.; the substrate is a sapphire substrate.

[0011] According to some embodiments of the present invention, the chemical solution cleaning includes: acid washing the substrate to remove contaminants on the surface of the substrate.

[0012] According to some embodiments of the present invention, the power of oxygen plasma cleaning is 100-300 W, the oxygen pressure is 500-600 mTorr, and the cleaning time is 3-7 min.

[0013] According to some embodiments of the present invention, the sputtering power of magnetron sputtering is 100-250 W, the pressure is 2.0-6 mTorr, and the coating rate of magnetron sputtering is 0.5-3 A / s.

[0014] According to another embodiment of the present invention, there is provided an application of the body-centered cubic lattice tantalum film as described above in the fields of low-temperature physics, superconducting detectors, and superconducting quantum chip technology.

[0015] According to some embodiments of the present invention, the present invention provides a body-centered cubic tantalum film prepared by an optimized magnetron sputtering process, which has a specific crystal orientation different from that of conventional processes. <111> The body-centered cubic tantalum film of the present invention exhibits different characteristics in physical and electrical properties, with fewer crystal domains and internal defects (line defects). Applying the body-centered cubic tantalum film of the present invention to superconducting quantum chips can reduce the number of non-superconducting regions, help reduce the noise caused by grain boundaries and defects, and improve the performance and stability of superconducting quantum chips.

[0016] According to some embodiments of the present invention, after the initial substrate is cleaned with a chemical solution and then cleaned with an oxygen plasma, magnetron sputtering is performed at a specific temperature, thereby suppressing the phenomenon of more crystal domains and more internal defects that are likely to occur in the process of preparing a tantalum film, thereby improving the surface flatness of the tantalum film and reducing the defect density of the tantalum film. The process of the present invention is relatively simple and is conducive to large-scale promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of a method for preparing a body-centered cubic tantalum thin film in an embodiment of the present invention is shown;

[0018] Figure 2a The figure shows an X-ray diffraction spectrum of the body-centered cubic lattice tantalum film 1' in Comparative Example 1 of the present invention, which characterizes the crystal orientation of the film;

[0019] Figure 2bThe figure shows an X-ray diffraction spectrum of the body-centered cubic tantalum film 1 in Example 1 of the present invention, which characterizes the crystal orientation of the film;

[0020] Figure 3a The comparative example 1 of the present invention is shown <110> X-ray diffraction spectrum of the body-centered cubic tantalum film 1' characterizing the lattice symmetry;

[0021] Figure 3b The present invention is shown in Example 1 <111> X-ray diffraction spectrum of body-centered cubic tantalum film 1 characterizing the lattice symmetry;

[0022] Figure 4a The comparative example 1 of the present invention is shown <110> Atomic force microscope image of body-centered cubic lattice tantalum film 1';

[0023] Figure 4b The present invention is shown in Example 1 <111> Atomic force microscopy image of body-centered cubic tantalum film 1 with different crystal orientations;

[0024] Figure 5a The comparative example 1 of the present invention is shown <110> Transmission electron microscope image of the body-centered cubic tantalum film 1' at a 2nm scale;

[0025] Figure 5b The present invention is shown in Example 1 <111> Transmission electron microscope image of the body-centered cubic lattice tantalum film 1 at a 2nm scale;

[0026] Figure 6a The comparative example 1 of the present invention is shown <110> Transmission electron microscope image of the body-centered cubic tantalum film 1' at a scale of 50nm;

[0027] Figure 6b The present invention is shown in Example 1 <111> Transmission electron microscope image of the body-centered cubic lattice tantalum film 1 at a 50nm scale. DETAILED DESCRIPTION

[0028] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0029] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0030] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0031] The advantages of thermal evaporation and electron beam evaporation are fast coating rate, good uniformity of epitaxial film, and good vacuum degree. However, both coating methods are mostly suitable for metal materials with relatively low melting points. The film prepared by magnetron sputtering coating method has the characteristics of good density and slow coating speed. Due to the high melting point of metallic tantalum and the existence of various lattice structures, it is difficult to use thermal evaporation or electron beam evaporation for coating. Currently common tantalum films include body-centered cubic lattice tantalum film (α-Ta) and tetragonal lattice tantalum film (β-Ta). Compared with tetragonal lattice tantalum film, body-centered cubic lattice tantalum film has the characteristics of fewer lattice defects, small resistance value, stable structure and wide application. However, conventional magnetron sputtering epitaxial tantalum films are mostly <110> The body-centered cubic tantalum film still has many crystal domains and internal defects.

[0032] In the process of realizing the concept of the present invention, it is found that by optimizing the magnetron sputtering process and coordinating with chemical solution cleaning and oxygen plasma cleaning, it is helpful to prepare a body-centered cubic lattice tantalum film with a crystal orientation different from that obtained by conventional processes. Chemical solution cleaning helps to clean carbon contamination on the surface of the initial substrate, and oxygen plasma cleaning helps to further remove carbon contamination on the surface of the initial substrate, repair damage to the surface of the initial substrate and remove carbon contamination on the surface of the substrate. Chemical solution cleaning and oxygen plasma cleaning cooperate to adjust the temperature of magnetron sputtering to a suitable temperature range, which helps to prepare a body-centered cubic lattice tantalum film with a specific crystal orientation, and the body-centered cubic lattice tantalum film has fewer crystal domains and fewer line defects.

[0033] Specifically, according to an embodiment of one aspect of the present invention, a method for preparing a body-centered cubic tantalum thin film is provided. Figure 1 FIG. 1 shows a flow chart of a method for preparing a body-centered cubic tantalum thin film according to an embodiment of the present invention. Figure 1 As shown, the method includes operations S101-S102.

[0034] In operation S101 , a chemical solution cleaning and an oxygen plasma cleaning are sequentially performed on an initial substrate to obtain a substrate.

[0035] According to some embodiments of the present invention, chemical solution cleaning is a surface pretreatment step before coating to remove carbon contamination on the surface of the initial substrate. Oxygen plasma is a dry cleaning method. Oxygen is introduced into the reaction chamber to form oxygen plasma under the action of a pressurized electric field. The free radicals and ions in the oxygen plasma react with the pollutants on the surface of the initial substrate, converting them into gaseous products such as carbon dioxide and water vapor, thereby further removing carbon contamination. Oxygen plasma cleaning also helps to repair damage caused by chemical solution cleaning of the initial substrate, making the substrate surface smoother and easier to grow epitaxially of a body-centered cubic tantalum film.

[0036] In operation S102 , a body-centered cubic tantalum thin film is formed on a substrate by magnetron sputtering using a tantalum target.

[0037] According to some embodiments of the present invention, a tantalum target is placed in a vacuum chamber, and argon gas is introduced into the reaction chamber to form an argon plasma by applying a DC or RF voltage. The argon plasma is accelerated to hit the surface of the tantalum target, so that tantalum atoms are sputtered from the surface of the target and deposited on the surface of the substrate to form a body-centered cubic tantalum film.

[0038] According to some embodiments of the present invention, the temperature of magnetron sputtering is 700-950°C. By setting the temperature in the above range, it is helpful to improve the mobility of tantalum atoms on the substrate surface and to form a body-centered cubic lattice structure. The present invention cooperates with oxygen plasma cleaning and magnetron sputtering in a specific temperature range to help prepare a substrate having <111> The body-centered cubic tantalum film with a crystal orientation suppresses the problem of more crystal domains and more internal defects in the tantalum film, especially more line defects, which are easy to appear in the process of preparing the tantalum film, and improves the surface flatness of the tantalum film. The process is relatively simple and is conducive to large-scale promotion. Specifically, the temperature of magnetron sputtering can be, for example, 700°C, 750°C, 800°C, 850°C, 900°C or 950°C.

[0039] Preferably, the temperature of magnetron sputtering is 700-800°C. When the temperature of magnetron sputtering is set to 700-800°C, the prepared body-centered cubic lattice tantalum film has fewer crystal domains, almost no lattice defects, and its surface is smoother. More preferably, the temperature of magnetron sputtering is 750°C. Before preparing the body-centered cubic lattice tantalum film, the substrate is annealed at a temperature of 600-950°C. Annealing helps to remove elements such as water and hydrogen on the surface of the substrate to ensure the cleanliness of the substrate. Specifically, the annealing temperature can be, for example, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, etc., preferably 650-850°C. The substrate is a sapphire substrate. The sapphire substrate has a very high melting point (about 2050°C), is relatively stable in a magnetron sputtering environment, and is suitable for a higher temperature magnetron sputtering process. The sapphire substrate has good chemical stability and thermal conductivity, especially the good lattice matching between the sapphire substrate and the tantalum film, which helps to reduce the stress and defects of the tantalum film and improve the film quality.

[0040] According to some embodiments of the present invention, in operation S101, the chemical solution cleaning includes: pickling the initial substrate to remove contaminants on the surface of the initial substrate. The surface of the initial substrate may contain grease, organic residues, inorganic contaminants or other contaminants. Pickling helps to improve the cleanliness of the surface of the initial substrate and provide a clean surface for subsequent coating. In the case where the substrate used is a sapphire substrate, contaminants such as carbon elements, zinc elements, etc. on the surface of the sapphire substrate during the preparation and storage process are removed by pickling.

[0041] Specifically, pickling can use one acid or several acids, for example. The pickling solution used in the present invention is a piranha solution, that is, a mixture of sulfuric acid and hydrogen peroxide for pickling.

[0042] More specifically, in the piranha solution used in pickling, the molar ratio of sulfuric acid to hydrogen peroxide is 1:1 to 3:1, for example, 1:1, 2:1 or 3:1, preferably 2:1. The pickling temperature is 50 to 90°C, for example, 50°C, 60°C, 70°C, 80°C or 90°C, preferably 70 to 90°C, more preferably 80°C. The pickling time is 10 to 30 minutes, for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes, preferably 20 minutes.

[0043] According to some embodiments of the present invention, after pickling, water washing and blow-drying operations may be performed as needed.

[0044] According to some embodiments of the present invention, the power of oxygen plasma cleaning is 100-300W, the oxygen pressure is 500-600mTorr, and the cleaning time is 3-7min. The parameters of oxygen plasma cleaning are set within the above range, which helps to repair the cleaning damage that may exist in the initial substrate after pickling. The power of oxygen plasma cleaning can be, for example, 100W, 200W or 300W, preferably 180-220W, and more preferably 200W. The oxygen pressure is 500mTorr, 550mTorr or 600mTorr, preferably 560-600mTorr, and more preferably 580mTorr. The cleaning time can be, for example, 3min, 4min, 5min, 6min or 7min, preferably 5min.

[0045] According to some embodiments of the present invention, the sputtering power of magnetron sputtering is 100~250W, the pressure is 2.0~6mTorr, and the coating rate of magnetron sputtering is 0.5~3A / s. Setting the parameters of magnetron sputtering within the above range helps to cooperate with the temperature of magnetron sputtering to promote the formation of a body-centered cubic lattice tantalum film with a specific crystal orientation, thereby improving the crystal domains and internal line defects of the body-centered cubic lattice tantalum film. The sputtering power can be, for example, 100W, 200W or 250W, preferably 120~130W, and more preferably 125W. The coating pressure can be, for example, 2.0mTorr, 3.0mTorr, 4.0mTorr, 5.0mTorr, 6.0mTorr, preferably 2.5~3.5mTorr, and more preferably 3mTorr. The deposition rate may be, for example, 0.5 A / s, 1 A / s, 2.0 A / s or 3.0 A / s, preferably 0.5 A / s to 1.5 A / s, and more preferably 1 A / s.

[0046] According to another embodiment of the present invention, a body-centered cubic tantalum film is provided. The body-centered cubic tantalum film has <111> Crystal orientation of epitaxial tantalum films.

[0047] According to some embodiments of the present invention, the body-centered cubic tantalum film prepared by the optimized magnetron sputtering process has a specific crystal orientation different from that of the conventional process. <111> Crystal orientation, the body-centered cubic lattice tantalum film of the present invention will show different characteristics in physical and electrical properties, with fewer crystal domains and internal defects (line defects).

[0048] According to some embodiments of the present invention, an X-ray diffraction device can be used to measure <111> The body-centered cubic tantalum film with a crystal orientation can measure the relative <111> The crystal orientation has three-fold rotational symmetry, and the scanning peak has the characteristics of high peak intensity and narrow peak width. For the body-centered cubic lattice structure, the (110) crystal plane is <111> The crystal orientation has three-fold rotational symmetry. If an ideal body-centered cubic lattice sample is tested with an X-ray diffraction device, the rotational symmetry peak measured should have a very narrow slit width and a very high peak intensity. <111> The body-centered cubic tantalum film has the characteristics of high peak intensity and narrow peak width, which means that the lattice mismatch, film stress, and lattice in-plane rotation are very small. <111> The crystal body-centered cubic tantalum film has a higher quality film. When it is subsequently used in superconducting detectors or superconducting quantum chips, this higher quality film quality will help to increase the superconducting critical temperature, increase the residual resistivity of the superconducting film, and improve the performance of the superconducting film.

[0049] According to some embodiments of the present invention, the thickness of the body-centered cubic tantalum film is 100-200 nm, for example, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm or 200 nm. The X-ray diffraction spectrum of the body-centered cubic tantalum film has a characteristic peak at 108.4°, with an error of ±0.2°. When the body-centered cubic tantalum film of the present invention is characterized by an X-ray diffractometer, it is found that in addition to the substrate peak, only the diffraction peak of the (222) crystal plane of the body-centered cubic tantalum film can be seen. The reason is that the (111) crystal plane cannot be detected due to the influence of interference extinction. Therefore, it can be concluded that the body-centered cubic tantalum film of the present invention has <111> Single crystal with different crystal orientations.

[0050] According to some embodiments of the present invention, the lattice constants of the body-centered cubic tantalum film are a = 330.13 pm, b = 330.13 pm, c = 330.13 pm, α = 90°, β = 90°, γ = 90°.

[0051] According to some embodiments of the present invention, the body-centered cubic lattice tantalum film has no lattice defects in the internal lattice, and there is no obvious domain distribution on the surface of the body-centered cubic lattice tantalum film. The domain can be understood as the distribution of grains. It can be understood that there is no obvious domain distribution on the surface of the film, which means that the film has higher quality and uniformity. Tantalum films with no lattice defects in the internal lattice have lower resistance. When used in superconducting detectors or superconducting quantum chips, this higher quality film quality helps to increase the superconducting critical temperature, increase the residual resistivity of the superconducting film, and improve the performance of the superconducting film. The tantalum film has no lattice defects, which makes it have higher mechanical properties and better thermal stability.

[0052] According to another embodiment of the present invention, there is provided an application of the body-centered cubic lattice tantalum film as described above in the fields of low-temperature physics, superconducting detectors, and superconducting quantum chip technology.

[0053] According to some embodiments of the present invention, the body-centered cubic tantalum film of the present invention has fewer crystal domains and fewer internal line defects, and has higher quality and better surface flatness. It has a wide range of applications in the fields of low-temperature physics, superconducting detectors, and superconducting quantum chips, can reduce the number of non-superconducting regions, help reduce noise caused by grain boundaries and defects, and improve the performance and stability of superconducting quantum chips, and has greater application scenarios and potential.

[0054] The present invention is further described below by examples, drawings and related test experiments and results thereof. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined arbitrarily into other feasible embodiments.

[0055] It should be noted that the following specific examples are only for illustration, and the protection scope of the present invention is not limited thereto. The chemicals and raw materials used in the following examples are all commercially available or homemade by recognized processing methods.

[0056] It should be noted that the oxygen plasma cleaning equipment, X-ray diffractometer, atomic force microscope, focused ion beam, scanning electron microscope and transmission electron microscope used in the present invention are all commonly used equipment in the field. The magnetron sputtering coating equipment used in the present invention is a device with a heating temperature of up to 900°C.

[0057] Embodiment 1:

[0058] Preparation process of epitaxial growth of body-centered cubic tantalum thin film 1 using magnetron sputtering equipment:

[0059] A sapphire substrate was prepared and cleaned with a piranha solution having a molar ratio of H2SO4 to H2O2 of 2:1, heated to 80°C, and cleaned for 20 minutes. After cleaning, the sapphire substrate was repeatedly cleaned with deionized water and dried with nitrogen.

[0060] After the sapphire substrate is dried, it is transferred to the vacuum chamber of the oxygen plasma equipment for cleaning within 5 minutes. The cleaning power is set to 200 W, the oxygen pressure is introduced to 580 mTorr, and the cleaning time is 5 minutes. After the cleaning is completed, the cleaning step of the sapphire substrate is completed.

[0061] The cleaned sapphire substrate was quickly loaded into the magnetron sputtering equipment and pretreated at high temperature in the coating machine at a temperature of 600° C. The temperature was raised to 750° C. for magnetron sputtering, the magnetron sputtering power was adjusted to 125 W, the gas pressure was 3 mTorr, the coating rate was 1 A / s, and the thickness of the formed body-centered cubic tantalum film 1 was between 100 and 200 nm.

[0062] Comparative Example 1:

[0063] The pickling step of this comparative example 1 is the same as that of Example 1, and will not be repeated here. After the sapphire substrate is dried, it is quickly fed into the magnetron sputtering equipment and subjected to high-temperature pretreatment in the coating machine at a pretreatment temperature of 900°C. The temperature is lowered to 500°C for magnetron sputtering, the magnetron sputtering power is adjusted to 250W, the gas pressure is 5mTorr, the coating rate is 1A / s, and the thickness of the formed body-centered cubic tantalum film 1' is between 100 and 200nm.

[0064] The body-centered cubic tantalum films prepared in Example 1 and Comparative Example 1 were characterized, and the results are as follows:

[0065] Figure 2a The X-ray diffraction spectrum of the body-centered cubic tantalum film 1' in Comparative Example 1 of the present invention is shown, which characterizes the crystal orientation of the film. Figure 2b FIG. 1 shows an X-ray diffraction spectrum of the body-centered cubic tantalum film 1 in Example 1 of the present invention, which characterizes the crystal orientation of the film. Figure 2a~Figure 2b As shown, the X-ray test diffraction peak is related to the lattice structure. For body-centered cubic tantalum film, the diffraction peak of the (110) crystal plane is around 38.5°, and the diffraction peak of the (222) crystal plane is around 108.4°. Therefore, according to the data in the X-ray diffraction spectrum, Figure 2a In the figure, except for the substrate peaks (substrate peak 0003, substrate peak 0006, substrate peak 0009, where 0003, 0006, 0009, etc. represent multiples), only the diffraction peak of α-Ta (110) crystal plane can be seen, so it is judged to be α-Ta <110> Single crystal. Figure 2b In the figure, except for the substrate peaks (substrate peak 0006, substrate peak 00012, where 0006, 00012, etc. represent multiples), only the diffraction peak of the α-Ta (222) crystal plane can be seen, and the (111) crystal plane cannot be detected due to interference extinction. Therefore, it is judged to be α-Ta <111> Single crystal.

[0066] Figure 3a The comparative example 1 of the present invention is shown <110> X-ray diffraction spectrum of the body-centered cubic lattice tantalum film 1' characterizing the lattice symmetry. Figure 3bThe present invention is shown in Example 1 <111> X-ray diffraction spectrum of body-centered cubic tantalum film 1 characterizing the lattice symmetry of the crystal orientation. <110> The body-centered cubic tantalum film 1' was rotated to face the (002) crystal plane upward, and the X-ray diffraction phi scan was performed. Figure 3a In the phi scan, a total of 6 peaks were observed. For the body-centered cubic tantalum film, the (002) crystal plane was <110> The crystal orientation shows two three-fold symmetric rotations, which is consistent with the results shown in the figure. <111> The body-centered cubic tantalum film 1 was rotated to face the (110) crystal plane upward, and the X-ray diffraction phi scan was performed. Figure 3b In the phi scan, a total of three sharp peaks were observed. For the body-centered cubic tantalum film, the (110) crystal plane was <111> The crystal orientation shows a three-fold symmetric rotation, which is consistent with the results shown in the figure.

[0067] Figure 4a The comparative example 1 of the present invention is shown <110> Atomic force microscope image of a body-centered cubic tantalum film 1' with different crystal orientations. Figure 4b The present invention is shown in Example 1 <111> Atomic force microscope image of body-centered cubic tantalum film 1 with different crystal orientations. Figure 4a As shown, <110> There is a clear crystal domain distribution on the surface of the tantalum film with crystal orientation, such as Figure 4b As shown, <111> No domain distribution was observed in the tantalum film with a crystal orientation. <111> The surface roughness of the tantalum film with crystal orientation is smaller.

[0068] Figure 5a The comparative example 1 of the present invention is shown <110> Transmission electron microscope image of the body-centered cubic lattice tantalum film 1' at a 2nm scale. Figure 5b The present invention is shown in Example 1 <111> Transmission electron microscope image of a body-centered cubic tantalum film 1 with a crystal orientation at a 2nm scale. Figure 5a~Figure 5b As shown in the figure, a clear epitaxial structure can be seen at the interface between the two tantalum films and the sapphire substrate, and the interface layer is also very thin. <110> There are line defects inside the tantalum film with different lattice structures on both sides of the defect. <111> No lattice defects were found in the tantalum films with the same crystal orientation.

[0069] Figure 6a The comparative example 1 of the present invention is shown <110> Transmission electron microscope image of a body-centered cubic tantalum film 1' with a crystalline orientation at a 50nm scale. Figure 6b The present invention is shown in Example 1 <111> Transmission electron microscope image of a body-centered cubic tantalum film 1 at a 50nm scale. Figure 6a~Figure 6b As shown, <110> Characterization of the tantalum film with different crystal orientations revealed that there were many line defects inside. <111> No lattice defects were found in the tantalum film with a crystal orientation, and the surface was smoother.

[0070] Please continue to refer to Figure 3a~Figure 3b , it can be seen that Figure 3a The phi scan peak in Figure 3b The phi scan peak in Figure 3a The peak strength is weaker than Figure 3b The peak strength in Figure 3a The peak width in Figure 3b The peak width in Figure 4a~Figure 4b , Figure 5a~Figure 5b as well as Figure 6a~Figure 6b By comparison, we can see <110> The crystal orientation of body-centered cubic tantalum film 1' is <111> The body-centered cubic lattice tantalum thin film 1 has poor single crystallinity.

[0071] Comparative Example 2:

[0072] In this comparative example 2, the sapphire substrate is not subjected to any pretreatment, and is directly plated in a magnetron sputtering coating device. The coating temperature is set between 400 and 700°C, and the other parameters are basically the same as those of Example 1. In this comparative example 2, the tetragonal tantalum film (β-Ta) is mainly formed. The reason is that the carbon contamination on the surface of the substrate makes it difficult to prepare a body-centered cubic tantalum film. However, if the sapphire substrate used is a newer substrate, it is possible to plate a body-centered cubic tantalum film (α-Ta), but its surface flatness is poor, and there are many crystal domains and internal defects in the film.

[0073] Comparative Example 3:

[0074] The operation steps of Comparative Example 3 are substantially the same as those of Example 1, except that, in Comparative Example 3, only chemical solution cleaning is performed before coating, and oxygen plasma cleaning is not performed. The thickness of the formed body-centered cubic tantalum film 3' is between 100 and 200 nm.

[0075] The tantalum films prepared in Example 1 and Comparative Example 3 were compared by preparing the quality factor of the ultra-low temperature test under the resonant cavity test. It can be seen from the relevant comparison that at ultra-low temperatures, the quality factor of the body-centered cubic lattice tantalum film 3' is worse than the quality factor of the body-centered cubic lattice tantalum film 1. Based on the above comparison, it can be seen that chemical solution cleaning, oxygen plasma cleaning and magnetron sputtering at a specific temperature can help reduce the number of crystal domains and internal defects of the body-centered cubic lattice tantalum film. It can also improve the surface flatness of the tantalum film, which is helpful for subsequent applications in low-temperature physics and other fields, and helps to improve the performance and stability of superconducting quantum chips.

[0076] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A body-centered cubic tantalum film, characterized in that: The body-centered cubic tantalum film has <111> A single crystal epitaxial tantalum film with a crystal orientation; the thickness of the body-centered cubic tantalum film is 100-200 nm; The body-centered cubic tantalum film has no lattice defects in its internal lattice, and the body-centered cubic tantalum film has no obvious crystal domain distribution on its surface; The body-centered cubic tantalum film is prepared by the following steps: The initial substrate is sequentially cleaned with a chemical solution and cleaned with oxygen plasma to obtain a substrate; Using a tantalum target to prepare a body-centered cubic tantalum film on the substrate by magnetron sputtering; The coating temperature of the magnetron sputtering is 700-950° C.; the power of the oxygen plasma cleaning is 100-300 W, the oxygen pressure is 500-600 mTorr, and the cleaning time is 3-7 min.

2. The body-centered cubic tantalum thin film according to claim 1, characterized in that: The (110) crystal plane of the body-centered cubic tantalum film is relative to <111> The crystal orientation has three-fold rotational symmetry.

3. The body-centered cubic tantalum thin film according to claim 1, characterized in that: The X-ray diffraction spectrum of the body-centered cubic lattice tantalum film has a characteristic peak at 108.4° with an error of ±0.2°.

4. The body-centered cubic tantalum thin film according to claim 1, characterized in that: Before preparing the body-centered cubic tantalum film, the substrate is annealed at a temperature of 650-950° C. The substrate is a sapphire substrate.

5. The body-centered cubic tantalum thin film according to claim 1, characterized in that: The chemical solution cleaning comprises: The initial substrate is pickled to remove pollutants on the surface of the initial substrate.

6. The body-centered cubic tantalum thin film according to claim 1, characterized in that: The sputtering power of the magnetron sputtering is 100-250W, the pressure is 2.0-6mTorr, and the coating rate of the magnetron sputtering is 0.5-3A / s.

7. An application of the body-centered cubic tantalum film according to any one of claims 1 to 6 in the fields of low-temperature physics, superconducting detectors, and superconducting quantum chip technology.

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