A ScAlN thin film with high crystallinity and high C-axis preferred orientation, and a preparation method and application thereof

Abstract

The present invention relates to a ScAlN thin film with high crystallinity and high C-axis preferred orientation, and a preparation method and application thereof. The preparation method includes: placing a first target and a second target at a first magnetron sputtering target position and a second magnetron sputtering target position respectively, and using an inert gas plasma to pre-clean a hard substrate at a working vacuum of 0.5 Pa - 1.5 Pa to achieve a soft etching effect; using a nitrogen plasma as a reaction gas and an inert gas as a working gas, and simultaneously reactive co-sputtering the first target and the second target on the surface of the obtained soft-etched hard substrate to obtain a ScAlN thin film with high crystallinity and high C-axis preferred orientation. The present invention combines the pre-cleaning of a hard substrate with an inert gas plasma, the nitrogen plasma-assisted reaction, and the dual-target co-sputtering, and matches a specific working vacuum for pre-cleaning, so as to prepare a ScAlN thin film with a C-axis preferred orientation that has better structural stability, lower surface stress, fewer internal defects, and higher crystallinity.

Description

Technical Field

[0001] The present invention relates to the technical field of ScAlN thin film preparation, and particularly relates to a ScAlN thin film with high crystallinity and high C-axis preferred orientation, and a preparation method and application thereof. Background Art

[0002] Due to the extremely high requirements of 5G communication networks for bandwidth and radio frequency signal processing accuracy, high-frequency filters are the core components of bandwidth and signal processing. The operating frequency not only affects the intensity of the output signal, but also directly determines the energy utilization rate and signal transmission reliability of the communication system. Therefore, strict requirements are imposed on the response rate and electromechanical coupling coefficient of the piezoelectric thin film that constitutes the filter to ensure its stable operation throughout the operating frequency range. However, traditional piezoelectric thin films such as PZT or LN are prone to high-frequency losses and acoustic wave attenuation due to their large dielectric constants, and thus cannot be used in 5G high-frequency signal filters. The ultra-wide bandgap semiconductor thin film AlN has low dielectric loss and acoustic wave attenuation and is considered as the piezoelectric thin film for the next-generation 5G high-frequency filters. However, the intrinsic piezoelectric coefficient of the AlN thin film is low and cannot meet the requirements of 5G filters for efficient conversion and frequency stability. For this reason, by introducing an appropriate amount of scandium (Sc) element, the piezoelectric constant and operating frequency of the AlN thin film can be significantly improved. Sc doping has been proven to not only enhance the piezoelectric response of the AlN thin film, but also enable the AlN thin film to have excellent stability and anti-interference ability in a wide frequency range, making it more suitable for the application requirements of 5G high-frequency filters.

[0003] CN106917088A discloses a process for preparing a ScAlN thin film with highly C-axis orientation, including step 1: placing substrate A in the center of the chemical deposition substrate table, and using chemical deposition method to prepare a layer of nitride Si3N4 on substrate A under a nitrogen atmosphere; step 2: pasting target C and target D and loading them into the sputtering chamber, fixing the substrate obtained in step 1 on the substrate holder, introducing a certain flow rate of nitrogen and argon, and using magnetron sputtering method to deposit a ScAlN thin film on the substrate. From the XRD patterns of the ScAlN thin films prepared on the Si substrate and the Si3N4 / Si substrate under the condition of a sputtering power of 285 W, it can be seen that the peak intensity value of the (002) orientation of the ScAlN thin film deposited on the Si substrate surface reaches 4000, and the peak intensity value of the (002) orientation of the ScAlN thin film deposited on the Si3N4 substrate surface increases by about 600. It can be seen that although pre-preparing a layer of nitride Si3N4 on substrate A can increase the degree of C-axis orientation of the thin film, the relative intensity of the corresponding diffraction peak is still not high, the crystallinity is not high, and the quality of the ScAlN thin film still needs to be improved.

[0004] CN107012439A discloses a scandium-doped aluminum nitride thin film and a preparation method thereof. First, a scandium-aluminum alloy target and a pre-cleaned alloy substrate are placed in the reaction chamber of a magnetron sputtering reaction device. After vacuum pumping, dehumidification, and gas introduction, sputtering deposition of a Sc-doped AlN thin film is started. After XRD analysis, it is shown that although all the thin film samples are highly single (002) oriented and the peak intensity increases with the increase of the sputtering power, through the XRD pattern, it can be analyzed that the corresponding ScAlN thin film has a low crystallinity, more lattice defects inside the thin film, a poor quality of the ScAlN thin film, and a poor stability.

[0005] Therefore, how to provide a preparation method of ScAlN thin film, which can realize the preparation of a ScAlN piezoelectric thin film with a high content of Sc element doping, and at the same time take into account the high C-axis orientation, high crystallinity, low surface stress, and low defects of the thin film, is a technical problem to be solved urgently, and will also bring a huge technical breakthrough to the design and application of 5G filters, and will promote the rapid development of 5G technology. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a ScAlN thin film with high crystallinity and high C-axis preferred orientation, a preparation method thereof, and an application. The ScAlN thin film provided by the present invention adopts a method combining hard substrate inert gas plasma pre-cleaning (a process of soft etching the surface of the hard substrate) + nitrogen plasma-assisted reaction + dual-target co-sputtering, with a working vacuum degree of the pre-cleaning being 0.5 Pa - 1.5 Pa. The prepared ScAlN thin film has a high crystallinity and grows along a specific C-axis preferred orientation, and the diffraction peak intensity of the C-axis (002) crystal plane is extremely high. The ScAlN thin film has better structural stability, lower surface stress, fewer internal lattice defects, and higher quality.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a preparation method of a ScAlN thin film with high crystallinity and high C-axis preferred orientation, and the preparation method includes the following steps:

[0009] (1) Place the first target at the first magnetron sputtering target position and the second target at the second magnetron sputtering target position. Use inert gas plasma to pre-clean the hard substrate at a working vacuum degree of 0.5 Pa - 1.5 Pa and achieve a soft etching effect to obtain a soft-etched hard substrate. For example, the working vacuum degree can be 0.5 Pa, 0.6 Pa, 0.7 Pa, 0.8 Pa, 0.9 Pa, 1.0 Pa, 1.1 Pa, 1.2 Pa, 1.3 Pa, 1.4 Pa, or 1.5 Pa, etc.;

[0010] (2) Using nitrogen plasma as the reaction gas and inert gas as the working gas, the first target and the second target are simultaneously subjected to reactive co-sputtering on the surface of the hard substrate for soft etching to obtain a ScAlN thin film with high crystallinity and high C-axis preferred orientation.

[0011] The present invention adopts a method of hard substrate inert gas plasma pre-cleaning (the process of soft etching the surface of the hard substrate) + nitrogen plasma-assisted reaction + dual-target co-sputtering. With the working vacuum degree of pre-cleaning being 0.5 Pa - 1.5 Pa, the prepared ScAlN thin film has high crystallinity and grows along a specific C-axis preferred orientation. Moreover, the relative intensity of the diffraction peak of the C-axis (002) crystal plane is extremely high, the surface stress is lower, the internal lattice defects are fewer, and the quality is higher.

[0012] Further, by adjusting the working vacuum degree during the pre-cleaning process to 0.5 Pa - 1.5 Pa, the present invention can ensure that the hard substrate realizes the effect of soft etching while being cleaned, so that its surface has sufficient surface energy for the crystallization and C-axis preferred growth of the ScAlN thin film. If the working vacuum degree is too high, the hard substrate will be severely etched, resulting in subsequent coating failure; if the working vacuum degree is too low, the cleaning effect and the soft etching effect will be poor, which is not conducive to the crystallization and C-axis preferred growth of the subsequent ScAlN thin film.

[0013] The whole preparation process has the following advantages: ① The hard substrate inert gas plasma pre-cleaning, nitrogen plasma-assisted reaction, and dual-target co-sputtering are integrated, simplifying the process operation procedure, improving the production efficiency, and having a wide application prospect; ② The ion source can provide a reaction gas plasma beam with high kinetic energy and high reactivity, increasing the collision frequency between the reaction gas plasma and the sputtered target metal atoms, enhancing the interaction between particles, thereby improving the sputtering deposition rate, providing additional reaction crystallization energy, accelerating nucleation and grain growth, and enabling the preparation of a ScAlN thin film with high crystallinity and C-axis preferred growth at low temperature; ③ By adopting the method of dual-target co-sputtering, the proportion of Sc component in the ScAlN thin film can be flexibly and precisely adjusted, facilitating the preparation of ScAlN thin films with different Sc doping amounts; ④ Using inert gas plasma to clean and soft-etch the surface of the hard substrate makes the surface of the hard substrate have higher surface energy, which is conducive to the C-axis direction preferred growth of the ScAlN thin film on the surface of the hard substrate; Combining the above advantages, the ScAlN thin film prepared by the preparation method of the present invention has higher crystallinity and more excellent C-axis orientation preferred growth, and at the same time has a lower preparation cost.

[0014] As a preferred technical solution of the present invention, the purity of the first target and the second target in step (1) is independently ≥ 6N.

[0015] Preferably, each of the first target and the second target in step (1) independently comprises any one of an aluminum target, a scandium target, or an aluminum scandium alloy target.

[0016] It should be noted that in the present invention, if the first target is an aluminum target or a scandium target, the second target is different from the first target. Similarly, if the second target is an aluminum target or a scandium target, the first target is also different from the second target. For example, if the first target is an aluminum target, the second target is other targets except the aluminum target.

[0017] Preferably, the material of the hard substrate in step (1) comprises any one of sapphire, silicon wafer, aluminum nitride, or silicon carbide.

[0018] As a preferred technical solution of the present invention, before the pre-cleaning in step (1), it further includes evacuating to a background vacuum of the reaction chamber ≤ 8×10 -5 Pa, such as 8×10 -5 Pa, 7×10 -5 Pa, 6×10 -5 Pa, 5×10 -5 Pa, 4×10 -5 Pa, 3×10 - 5 Pa, 2×10 -5 Pa, 1×10 -5 Pa or 0.5×10 -5 Pa, etc.

[0019] As a preferred technical solution of the present invention, the inert gas plasma in step (1) is obtained by ionizing an inert gas introduced into an ion source.

[0020] Preferably, the inert gas includes argon.

[0021] During the pre-cleaning process of the present invention, there are no specific requirements and special limitations on the flow rate of the inert gas. Because in the actual process, the volume of the reaction chamber is different. After the flow rate of the inert gas is coordinated with the opening of the flow limiting valve, it only needs to meet the working vacuum degree of 0.5 Pa - 1.5 Pa. Those skilled in the art can adaptively select and adjust the flow rate of the inert gas according to the actual situation.

[0022] As a preferred technical solution of the present invention, during the process of introducing the inert gas into the ion source for ionization, the ion source power is 100 W - 400 W, such as 100 W, 150 W, 200 W, 250 W, 300 W, 350 W, or 400 W, etc.

[0023] Preferably, the ion source includes any one of an anode ion source, a radio frequency ion source, or a Kaufman ion source.

[0024] Preferably, the current of the ion source is 100 mA - 450 mA, such as 100 mA, 150 mA, 200 mA, 250 mA, 300 mA, 350 mA, 400 mA or 450 mA, etc.

[0025] Preferably, the time for the pre - cleaning in step (1) is 10 min - 60 min, such as 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, etc.

[0026] As a preferred technical solution of the present invention, the nitrogen plasma in step (2) is obtained by ionizing nitrogen introduced into the ion source, and the flow rate ratio of the nitrogen to the inert gas in step (2) is (1 - 3):1, such as 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, etc.

[0027] Preferably, the inert gas in step (2) includes argon.

[0028] In the reactive co - sputtering process of the present invention, the nitrogen plasma is used as a reactive gas to react with the sputtered metal atoms to obtain the ScAlN thin film, and the inert gas argon is used as a working gas for sputtering metal atoms. By adjusting the flow rate ratio of nitrogen to the inert gas in step (2) to be (1 - 3):1, the ScAl:N ratio in the ScAlN thin film can be made closer to its target stoichiometric ratio, and high c - axis preferred orientation and piezoelectric coefficient can be ensured.

[0029] In the reactive co - sputtering process of the present invention, there are no specific requirements and special limitations on the respective flow rates of nitrogen and the inert gas. Because in the actual process, the volume of the reaction chamber is different, it only needs to satisfy that the pressure of the reactive co - sputtering is 0.2 Pa - 0.8 Pa. Those skilled in the art can, on the premise of ensuring that the flow rate ratio of nitrogen to the inert gas is (1 - 3):1, adaptively select and adjust the respective flow rates of nitrogen and the inert gas according to the actual situation.

[0030] As a preferred technical solution of the present invention, during the process of ionizing nitrogen introduced into the ion source, the power of the ion source is 50 W - 200 W, such as 50 W, 100 W, 150 W or 200 W, etc.

[0031] Preferably, the ion source includes any one of an anode ion source, a radio - frequency ion source or a Kaufman ion source.

[0032] Preferably, the current of the ion source is 100 mA - 450 mA, such as 100 mA, 150 mA, 200 mA, 250 mA, 300 mA, 350 mA, 400 mA or 450 mA, etc.

[0033] As a preferred technical solution of the present invention, the magnetron sputtering power supply used in the reactive co-sputtering in step (2) includes any one of a radio frequency power supply, a direct current power supply, or a high power pulsed magnetron sputtering power supply.

[0034] Preferably, the sputtering powers of the first target and the second target in step (2) are independently 100 W - 500 W, such as 100 W, 120 W, 150 W, 180 W, 200 W, 220 W, 250 W, 280 W, 300 W, 320 W, 350 W, 380 W, 400 W, 420 W, 450 W, 480 W, or 500 W, etc.

[0035] In the present invention, by controlling the sputtering powers of the first target and the second target to be independently 100 W - 500 W, it can ensure that the first target and the second target have independent and different sputtering rates, which is convenient for controlling and preparing ScAlN films doped with Sc elements with different atomic percentages.

[0036] Preferably, the pressure of the reactive co-sputtering in step (2) is 0.2 Pa - 0.8 Pa, such as 0.2 Pa, 0.3 Pa, 0.4 Pa, 0.5 Pa, 0.6 Pa, 0.7 Pa, or 0.8 Pa, etc.

[0037] In the present invention, by controlling the pressure of the reactive co-sputtering to be 0.2 Pa - 0.8 Pa, the sputtering rates of the overall film can be made different, which is convenient for controlling the deposition rate of the ScAlN film.

[0038] In the present invention, no specific requirements or special limitations are imposed on the time of the reactive co-sputtering. Those skilled in the art can make adaptive selection and adjustment according to the thickness of the ScAlN film required in the actual process.

[0039] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0040] (1) Place the first target in the first magnetron sputtering target position and the second target in the second magnetron sputtering target position, evacuate to a background vacuum of the reaction chamber ≤ 8×10 -5 Pa, introduce an inert gas into the ion source, ionize it at an ion source power of 100 W - 400 W and an ion source current of 100 mA - 450 mA to obtain an inert gas plasma, and use the inert gas plasma to pre-clean the hard substrate for 10 min - 60 min at a working vacuum degree of 0.5 Pa - 1.5 Pa to achieve a soft etching effect and obtain a soft-etched hard substrate.

[0041] (2) Nitrogen and an inert gas are respectively introduced into the ion source and the reaction chamber, and the flow rate ratio of nitrogen to the inert gas is (1 - 3):1. Nitrogen is ionized at an ion source power of 50 W - 200 W and an ion source current of 100 mA - 450 mA to obtain nitrogen plasma. Among them, the nitrogen plasma serves as the reaction gas, and the inert gas serves as the working gas. At a reaction co-sputtering pressure of 0.2 Pa - 0.8 Pa, the first target is at a power of 100 W - 500 W, and the second target is at a power of 100 W - 500 W, and they are simultaneously reaction co-sputtered on the surface of the soft-etching hard substrate to obtain a ScAlN thin film with high crystallinity and high C-axis preferred orientation.

[0042] In a second aspect, the present invention also provides a ScAlN thin film with high crystallinity and high C-axis preferred orientation, and the ScAlN thin film with high crystallinity and high C-axis preferred orientation is prepared according to the preparation method described in the first aspect.

[0043] It should be noted that in the ScAlN thin film with high crystallinity and high C-axis preferred orientation of the present invention, there are no specific requirements and special limitations on the atomic percentage of Sc element. Those skilled in the art can make adaptive selections and adjustments according to actual needs. For example, it can be 0 at% - 50 at%, and it is not 0.

[0044] In a third aspect, the present invention also provides an application of a ScAlN thin film with high crystallinity and high C-axis preferred orientation. The ScAlN thin film with high crystallinity and high C-axis preferred orientation prepared by the preparation method described in the first aspect, or the ScAlN thin film with high crystallinity and high C-axis preferred orientation described in the second aspect, is applied to the preparation of high-frequency filters.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects:

[0046] 1) The method provided by the present invention combines hard substrate inert gas plasma pre-cleaning (the process of soft-etching the hard substrate surface), nitrogen plasma-assisted reaction, and dual-target co-sputtering. Under low pressure and without any heating of the hard substrate, and without inserting any transition layer between the hard substrate and the prepared ScAlN thin film, a ScAlN thin film with high crystallinity and high C-axis (002) crystal plane preferred orientation growth can be obtained.

[0047] 2) The hard substrate inert gas plasma pre-cleaning (the process of soft-etching the hard substrate surface), nitrogen plasma-assisted reaction, and dual-target co-sputtering processes of the present invention are integrated, the preparation process is simple, the cost is low, and it has a wide application prospect.

[0048] 3) The ScAlN thin film prepared by the preparation method of the present invention has a full width at half maximum of the (002) crystal plane ≤ 0.250° and a diffraction peak intensity value of the (002) crystal plane ≥ 70000, and has high crystallinity and high C-axis preferred orientation. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is the XRD pattern of the ScAlN thin film with high crystallinity and high C-axis preferred orientation provided in Example 1 of the present invention.

[0050] Figure 2 is the XRD pattern of the ScAlN thin film with high crystallinity and high C-axis preferred orientation provided in Comparative Example 1 of the present invention.

[0051] Figure 3 is the XRD pattern of the ScAlN thin film with high crystallinity and high C-axis preferred orientation provided in Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0052] The technical solution of the present invention will be further described below with reference to the drawings and through specific embodiments. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0053] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0054] The magnetron sputtering equipment used in the specific embodiment part of the present invention is the magnetron sputtering coating device disclosed in Patent CN119082689A.

[0055] Example 1

[0056] This example provides a method for preparing a ScAlN thin film with high crystallinity and high C-axis preferred orientation. The preparation method includes the following steps:

[0057] (1) Place the Al target in the first magnetron sputtering target position, the Sc target in the second magnetron sputtering target position, and the quartz glass substrate as the optical substrate (diameter 30 mm). Immerse the optical substrate in an organic solvent and ultrasonically clean it for 20 min, then rinse it with ultrapure water, and finally blow it with nitrogen. Immerse the (100)-oriented silicon wafer in a hydrofluoric acid solution for surface treatment for 30 s, immerse it in an organic solvent and ultrasonically clean it for 20 min, then rinse it with ultrapure water, and finally dry it with nitrogen to obtain a hard substrate; evacuate to a background vacuum of 5×10 -5Pa, the opening degree of the flow-limiting valve is 15%. Introduce Ar into the ion source at a flow rate of 30 sccm. Set the ion source current to 450 mA and the power to 200 W. Turn on the anode ion source to ionize Ar. The working vacuum degree is 1.5 Pa. Use the Ar plasma to pre-clean the silicon wafer for 30 min to obtain a soft-etched hard substrate.

[0058] (2) Introduce nitrogen and Ar into the ion source and the reaction chamber at flow rates of 22.5 sccm and 7.5 sccm respectively. Set the ion source current to 100 mA and the power to 50 W. Turn on the ion source to ionize nitrogen to obtain nitrogen plasma. Under the working gas of 0.8 Pa (the total sputtering pressure of the reaction), set the sputtering power of the Al target to 450 W and the sputtering power of the Sc target to 300 W. Turn on the radio frequency power supply. The nitrogen plasma reacts with the co-sputtered Al and Sc metal atoms by sputtering for 1 h to obtain a ScAlN film with high crystallinity and high C-axis preferred orientation (thickness is 800 nm, and the atomic percentage of Sc is 30 at%) on the surface of the soft-etched hard substrate.

[0059] Comparative Example 1

[0060] This comparative example provides a method for preparing a ScAlN film with high crystallinity and high C-axis preferred orientation. The difference between this preparation method and that of Example 1 is that the pre-cleaning of the silicon wafer using Ar plasma in step (1) is omitted, and the reaction co-sputtering is directly carried out on the surface of the silicon wafer. The remaining preparation methods and parameters are the same as those of Example 1.

[0061] Comparative Example 2

[0062] This comparative example provides a method for preparing a ScAlN film with high crystallinity and high C-axis preferred orientation. The difference between this preparation method and that of Example 1 is that the process of ionizing nitrogen in step (2) is omitted, and nitrogen is directly used as the reaction gas. The remaining preparation methods and parameters are the same as those of Example 1.

[0063] Comparative Example 3

[0064] This comparative example provides a method for preparing a ScAlN film with high crystallinity and high C-axis preferred orientation. The difference between this preparation method and that of Example 1 is that in step (1), the working vacuum degree for pre-cleaning is adjusted to 0.2 Pa, and the remaining preparation methods and parameters are the same as those of Example 1.

[0065] Comparative Example 4

[0066] This comparative example provides a method for preparing a ScAlN film with high crystallinity and high C-axis preferred orientation. The difference between this preparation method and that of Example 1 is that in step (1), the working vacuum degree for pre-cleaning is adjusted to 2.0 Pa, and the remaining preparation methods and parameters are the same as those of Example 1.

[0067] The ScAlN thin films with high crystallinity and high C-axis preferred orientation prepared in Example 1 and Comparative Examples 1-4 were subjected to XRD testing. The specific testing conditions were as follows: A Rigaku SmartLab X-ray diffractometer was used, with a Cu target as the instrument's X-ray source, a wavelength of 0.154056 nm, a tube current of 200 mA, a tube voltage of 45 kV. The scanning speed was set to 3.0° / min for continuous scanning. According to the phase of the thin film, the scanning angle range was set to 20° - 50°. Through analysis and calculation of the XRD pattern, the full width at half maximum, I (002) value, and I (002) / I (100) value of the (002) crystal plane of the C-axis were determined. The specific test results are shown in Table 1.

[0068] Figure 1 The XRD pattern of the ScAlN thin film with high crystallinity and high C-axis preferred orientation provided in Example 1 of the present invention is shown. Figure 2 The XRD pattern of the ScAlN thin film with high crystallinity and high C-axis preferred orientation provided in Comparative Example 1 of the present invention is shown. Figure 3 The XRD pattern of the ScAlN thin film with high crystallinity and high C-axis preferred orientation provided in Comparative Example 2 of the present invention is shown. As can be seen from the figure, ① the peak position of the (002) crystal plane diffraction peak in Example 1 is at 36.2°, the peak position of the (002) crystal plane diffraction peak in Comparative Example 1 is at 36.1°, and the peak position of the (002) crystal plane diffraction peak in Comparative Example 2 is at 36.1°. The (002) crystal plane diffraction peak of the thin film in the AlN standard card should appear at 36°, indicating that the prepared AlN thin film is indeed doped with Sc element, so there is a deviation; ② compared with Comparative Example 1, the intensity value of the (002) crystal plane diffraction peak in Example 1 increased by 70315. Compared with Comparative Example 2, the intensity value of the (002) crystal plane diffraction peak in Example 1 also increased by 66189. In Example 1, Comparative Example 1, and Comparative Example 2, the full width at half maximum of the (002) crystal plane is 0.246°, 0.278°, and 0.268° respectively. The above test results show that by combining the method of pre-cleaning with inert gas plasma on a hard substrate + nitrogen plasma-assisted reaction + co-sputtering with two targets, after combining the above processes, the C-axis orientation of the ScAlN thin film can be significantly enhanced, and at the same time, it also has a high degree of crystallinity.

[0069] Table 1

[0070]

[0071] It can be seen from the test results that:

[0072] (1)From the comparison between Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that the present invention adopts a method combining hard substrate inert gas plasma pre-cleaning + nitrogen plasma-assisted reaction + dual-target co-sputtering, and then with the pre-cleaning working vacuum degree of 0.5 Pa - 1.5 Pa. The full width at half maximum of the (002) crystal plane of the prepared ScAlN film is relatively narrow, and the intensity value of the diffraction peak of the (002) crystal plane is extremely high, significantly higher than that of Comparative Example 1 and Comparative Example 2. It has higher crystallinity, obvious C-axis preferred orientation, better structural stability, lower surface stress, fewer internal lattice defects, and higher quality.

[0073] (2)From the comparison between Example 1, Comparative Example 3 and Comparative Example 4, it can be seen that the present invention also needs to be combined with a pre-cleaning working vacuum degree of 0.5 Pa - 1.5 Pa. Within this vacuum degree, a ScAlN film with high crystallinity and high C-axis preferred orientation growth can be obtained, thereby ensuring that the ScAlN film has higher quality. If the pre-cleaning working vacuum degree is too low, it will lead to more defects in the prepared ScAlN film and the inability to grow along the C-axis preferred orientation; if the pre-cleaning working vacuum degree is too high, the hard substrate will be severely etched, resulting in subsequent coating failure.

[0074] In summary, the ScAlN film provided by the present invention adopts a method combining hard substrate inert gas plasma pre-cleaning (the process of soft etching the surface of the hard substrate) + nitrogen plasma-assisted reaction + dual-target co-sputtering, and is combined with a pre-cleaning working vacuum degree of 0.5 Pa - 1.5 Pa. The prepared ScAlN film has higher crystallinity and grows along a specific C-axis preferred orientation, and the diffraction peak intensity of the C-axis (002) crystal plane is extremely high. The ScAlN film has better structural stability, lower surface stress, fewer internal lattice defects, and higher quality.

[0075] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a ScAlN thin film with high crystallinity and high C-axis preferred orientation, characterized in that, The preparation method includes the following steps: (1) Place the first target on the first magnetron sputtering target position and the second target on the second magnetron sputtering target position. Use inert gas plasma to pre-clean the hard substrate for 10 min - 60 min at a working vacuum of 1 Pa - 1.5 Pa to achieve a soft etching effect, and obtain a soft-etched hard substrate; Among them, the inert gas plasma is obtained by ionizing an inert gas introduced into an ion source, and the power of the ion source is 100 W - 400 W; The ion source is an anode ion source; (2) Use nitrogen plasma as the reaction gas and an inert gas as the working gas. The first target and the second target are simultaneously subjected to reactive co-sputtering on the surface of the soft-etched hard substrate to obtain a ScAlN thin film with high crystallinity and high C-axis preferred orientation; The full width at half maximum of the (002) crystal plane of the ScAlN thin film ≤ 0.250°, and the diffraction peak intensity value of the (002) crystal plane ≥ 70000.

2. The preparation method according to claim 1, wherein In step (1), the first target and the second target each independently include any one of an aluminum target, a scandium target, or an aluminum scandium alloy target; In step (1), the material of the hard substrate includes any one of sapphire, silicon wafer, aluminum nitride, or silicon carbide.

3. The preparation method according to claim 1, wherein Before the pre-cleaning described in step (1), it also includes evacuating the reaction chamber to a background vacuum of ≤ 8×10 -5 Pa.

4. The preparation method according to claim 1, wherein The inert gas includes argon.

5. The preparation method according to claim 1, wherein In step (2), the nitrogen plasma is obtained by ionizing nitrogen introduced into an ion source, and the flow rate ratio of the nitrogen to the inert gas in step (2) is (1 - 3):1; In step (2), the inert gas includes argon.

6. The preparation method according to claim 5, wherein During the process of ionizing nitrogen introduced into the ion source, the power of the ion source is 50 W - 200 W.

7. The preparation method according to claim 1, characterized in that, In step (2), the sputtering power of the first target and the second target is each independently 100 W - 500 W; In step (2), the pressure of the reactive co-sputtering is 0.2 Pa - 0.8 Pa.

8. A ScAlN thin film with high crystallinity and high C-axis preferred orientation, characterized in that, The ScAlN thin film with high crystallinity and high C-axis preferred orientation is prepared by the preparation method according to any one of claims 1 - 7.

9. Application of a ScAlN thin film with high crystallinity and high C-axis preferred orientation, characterized in that, The ScAlN thin film with high crystallinity and high C-axis preferred orientation according to claim 8 is applied to the preparation of high-frequency filters.

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