ScAlN thin film with high crystallinity and high C-axis preferred orientation and preparation method and application of ScAlN thin film

Abstract

The invention relates to a high-crystallinity and high-C-axis preferred orientation ScAlN film and a preparation method and application thereof.The preparation method comprises the steps that a first target material and a second target material are placed in a first magnetron sputtering target position and a second magnetron sputtering target position respectively, and a hard substrate is pre-cleaned under the working vacuum degree of 0.5 Pa-1. 5 Pa through inert gas plasmas to achieve the soft etching effect; and by taking nitrogen plasma as reaction gas and inert gas as working gas, reacting and co-sputtering the first target material and the second target material on the surface of the soft etching hard substrate at the same time to obtain the ScAlN film with high crystallinity and high C-axis preferred orientation. According to the preparation method, hard substrate inert gas plasma pre-cleaning, nitrogen plasma auxiliary reaction and double-target co-sputtering are combined, and the working vacuum degree of specific pre-cleaning is matched, so that the ScAlN film with C-axis preferred orientation, which is better in structural stability, lower in surface stress, fewer in internal defects and higher in crystallinity, can be prepared.

Description

Technical Field

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

[0002] Since 5G communication networks have extremely high requirements for bandwidth and RF signal processing accuracy, high-frequency filters are the core components of bandwidth and signal processing. The operating frequency not only affects the strength of the output signal, but also directly determines the energy utilization rate and signal transmission reliability of the communication system. Therefore, strict requirements are placed on the response rate and electromechanical coupling coefficient of the piezoelectric film that constitutes the filter to ensure its stable operation over the entire operating frequency range. However, traditional piezoelectric films such as PZT or LN are prone to high-frequency loss and acoustic wave attenuation due to their large dielectric constants, so they cannot be used in 5G high-frequency signal filters. Ultra-wide bandgap semiconductor film AlN has low dielectric loss and acoustic wave attenuation, and is considered to be the next generation of 5G high-frequency filter piezoelectric film. However, the intrinsic piezoelectric coefficient of AlN film is low, which cannot meet the requirements of 5G filters for efficient conversion and frequency stability. To this end, the piezoelectric constant and operating frequency of AlN film can usually be significantly improved by introducing an appropriate amount of scandium (Sc) element. Sc doping has been shown to not only enhance the piezoelectric response of AlN films, but also enable AlN films to have excellent stability and anti-interference capabilities over a wider frequency range, making them more capable of meeting the application requirements of 5G high-frequency filters.

[0003] CN106917088A discloses a process for preparing a highly C-axis oriented ScAlN film, comprising the steps of placing a substrate A in the center of a chemical deposition substrate table, and preparing a layer of nitride Si3N4 on the substrate A by chemical deposition in a nitrogen atmosphere; and placing a target C and a target D in a sputtering chamber, fixing the substrate obtained in step 1 on a substrate rack, introducing a certain flow of nitrogen and argon, and depositing a ScAlN film on the substrate by magnetron sputtering. The XRD graph of the ScAlN film prepared on the Si substrate and the Si3N4 / Si substrate under the condition of a sputtering power of 285W shows that the peak intensity value of the (002) orientation of the ScAlN film deposited on the surface of the Si substrate reaches 4000, and the peak intensity value of the (002) orientation of the ScAlN film deposited on the surface of the Si3N4 substrate increases by about 600. It can be seen that although pre-preparing a layer of nitride Si3N4 on substrate A can increase the C-axis orientation of the film, the relative intensity of the corresponding diffraction peak is still not high, and the crystallinity is not high either. The quality of the ScAlN film needs to be improved.

[0004] CN107012439A discloses a scandium-doped aluminum nitride film and a preparation method thereof, comprising placing a scandium-aluminum alloy target and a pre-cleaned alloy substrate in a reaction chamber of a magnetron sputtering reaction device, and after vacuuming, dehumidification and ventilation, sputtering and depositing a Sc-doped AlN film. XRD analysis shows that although all film samples have a highly single (002) orientation and the peak intensity increases with the increase of sputtering power, the XRD diagram shows that the corresponding ScAlN film has a low crystallinity, a large number of lattice defects inside the film, and a poor quality and stability of the ScAlN film.

[0005] Therefore, how to provide a method for preparing ScAlN thin films that can achieve the preparation of ScAlN piezoelectric films doped with high content of Sc elements while taking into account the high C-axis orientation, high crystallinity, low surface stress and low defects of the films is a technical problem that needs to be solved urgently. It will also bring huge technological breakthroughs to the design and application of 5G filters and will promote the rapid development of 5G technology. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a ScAlN film with high crystallinity and high C-axis preferred orientation, and a preparation method and application thereof. The ScAlN 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, and the working vacuum degree of pre-cleaning is 0.5Pa-1.5Pa. The prepared ScAlN film has 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 film has better structural stability, lower surface stress, fewer internal lattice defects, and higher quality.

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

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

[0009] (1) placing a first target material at a first magnetron sputtering target position, placing a second target material at a second magnetron sputtering target position, and using an inert gas plasma to pre-clean the hard substrate at a working vacuum of 0.5 Pa-1.5 Pa to achieve a soft etching effect, thereby obtaining a soft-etched hard substrate; for example, the working vacuum 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 a reaction gas and an inert gas as a working gas, the first target material and the second target material are simultaneously reactively co-sputtered on the surface of the soft-etched hard substrate to obtain a ScAlN 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 (a process of soft etching the surface of the hard substrate) + nitrogen plasma assisted reaction + dual-target co-sputtering, and the working vacuum degree of the pre-cleaning is 0.5Pa-1.5Pa. The prepared ScAlN film has high crystallinity and grows along a specific C-axis preferential orientation. The diffraction peak relative intensity 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] Furthermore, the present invention can ensure that the hard substrate can achieve the effect of soft etching while cleaning by adjusting the working vacuum degree in the pre-cleaning process to 0.5Pa-1.5Pa, so that the surface of the hard substrate has sufficient surface energy for crystallization and C-axis preferential growth of the ScAlN film. If the working vacuum degree is too high, the hard substrate will be severely etched, which will cause subsequent coating failure; if the working vacuum degree is too low, the cleaning effect and soft etching effect will be poor, which is not conducive to the subsequent crystallization and C-axis preferential growth of the ScAlN film.

[0013] The whole preparation process has the following advantages: ① pre-cleaning of the hard substrate by inert gas plasma, nitrogen plasma-assisted reaction and dual-target co-sputtering are integrated, which simplifies the process operation procedure, improves the production efficiency and has a wide application prospect; ② the ion source can provide a high-kinetic energy and high-reactivity reaction gas plasma beam, increase the collision frequency between the reaction gas plasma and the metal atoms of the sputtering target, enhance the interaction between the particles, thereby improving the sputtering deposition rate, providing additional reaction crystallization energy, accelerating nucleation and grain growth, and preparing a ScAlN film with high crystallinity and C-axis preferential growth at a low temperature; ③ the method of dual-target co-sputtering can flexibly and accurately control the proportion of Sc components in the ScAlN film, which is convenient for preparing ScAlN films with different Sc doping amounts; ④ the surface of the hard substrate is cleaned and soft-etched by inert gas plasma, so that the surface of the hard substrate has a higher surface energy, which is conducive to the preferential growth of the ScAlN film on the surface of the hard substrate along the C-axis direction; based on the above advantages, the ScAlN film prepared by the preparation method of the present invention has a higher crystallinity and a better C-axis orientation preferential growth, and at the same time has a lower preparation cost.

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

[0015] Preferably, in step (1), the first target material and the second target material each independently include 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 material is an aluminum target or a scandium target, the second target material is different from the first target material. Similarly, if the second target material is an aluminum target or a scandium target, the first target material is also different from the second target material. For example, if the first target material is an aluminum target, the second target material is a target material other than an aluminum target.

[0017] Preferably, the material of the hard substrate in step (1) includes 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), the process also includes evacuating the reaction chamber to a background vacuum of ≤8×10 -5 Pa, for example 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 et al.

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

[0020] Preferably, the inert gas comprises argon.

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

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

[0023] Preferably, the ion source comprises 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, for example, 100 mA, 150 mA, 200 mA, 250 mA, 300 mA, 350 mA, 400 mA or 450 mA.

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

[0026] As a preferred technical solution of the present invention, the nitrogen plasma in step (2) is obtained by passing nitrogen into an ion source for ionization, and the flow ratio of the nitrogen to the inert gas in step (2) is (1-3):1, for example, 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, nitrogen plasma is used as a reactive gas to react with the sputtered metal atoms to obtain a ScAlN film, and inert gas argon is used as a working gas to sputter the metal atoms. By adjusting the flow rate ratio of nitrogen to the inert gas in step (2) to (1-3):1, the ScAl:N ratio in the ScAlN film can be made closer to its target stoichiometric ratio, and a high C-axis preferred orientation and piezoelectric coefficient can be ensured.

[0029] In the reactive co-sputtering process of the present invention, no specific requirements or special limitations are made on the flow rates of nitrogen and inert gas respectively. In the actual process, the volume of the reaction chamber varies. It is only necessary to meet the pressure of reactive co-sputtering of 0.2Pa-0.8Pa. Those skilled in the art can adaptively select and adjust the flow rates of nitrogen and inert gas respectively according to the actual situation while ensuring that the flow ratio of nitrogen to inert gas is (1-3):1.

[0030] As a preferred technical solution of the present invention, in the process of introducing nitrogen into the ion source for ionization, the power of the ion source is 50W-200W, such as 50W, 100W, 150W or 200W.

[0031] Preferably, the ion source comprises 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, for example, 100 mA, 150 mA, 200 mA, 250 mA, 300 mA, 350 mA, 400 mA or 450 mA.

[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, in step (2), the sputtering powers of the first target and the second target are independently 100 W-500 W, for example, 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 adjusting the sputtering power of the first target and the second target to be 100W-500W respectively, the first target and the second target can have independent and different sputtering rates, which is convenient for adjusting and preparing ScAlN films doped with Sc elements of different atomic percentages.

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

[0037] In the present invention, by adjusting the pressure of the reactive co-sputtering to 0.2Pa-0.8Pa, the sputtering rate of the entire film can be made different, which facilitates the adjustment of the deposition rate of the ScAlN film.

[0038] In the present invention, there is no specific requirement or special limitation on the time of the reactive co-sputtering, and those skilled in the art can adaptively select and adjust it according to the required ScAlN film thickness in the actual process.

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

[0040] (1) Place the first target material at the first magnetron sputtering target position and the second target material at the second magnetron sputtering target position, and evacuate the reaction chamber to a background vacuum of ≤8×10 -5 Pa, an inert gas is introduced into an ion source, ionized at an ion source power of 100W-400W and an ion source current of 100mA-450mA to obtain an inert gas plasma, and at a working vacuum degree of 0.5Pa-1.5Pa, the hard substrate is pre-cleaned for 10min-60min using the inert gas plasma to achieve a soft etching effect, thereby obtaining a soft-etched hard substrate;

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

[0042] In a second aspect, the present invention further provides a ScAlN film with high crystallinity and high C-axis preferred orientation, wherein the ScAlN 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 present invention, there is no specific requirement or special limitation on the atomic percentage of Sc element in the ScAlN film with high crystallinity and high C-axis preferred orientation. Those skilled in the art can make adaptive selection and adjustment according to actual needs. For example, it can be 0at%-50at%, and not 0.

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

[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 inert gas plasma pre-cleaning of a hard substrate (a process of soft etching the surface of a hard substrate) + nitrogen plasma assisted reaction + dual-target co-sputtering, under low gas pressure and without any heating of the hard substrate, and without inserting any transition layer between the hard substrate and the prepared ScAlN film, a ScAlN film with high crystallinity and high C-axis (002) 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 process of the present invention are integrated, the preparation process is simple, the cost is low, and it has broad application prospects.

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

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

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

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

[0052] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of 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 commercially available or can be prepared by known methods.

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

[0055] Example 1

[0056] This embodiment provides a method for preparing a ScAlN film with high crystallinity and high C-axis preferred orientation, the preparation method comprising the following steps:

[0057] (1) The Al target was placed in the first magnetron sputtering target position, the Sc target was placed in the second magnetron sputtering target position, and the quartz glass substrate was used as the optical substrate (diameter 30 mm). The optical substrate was immersed in an organic solvent and ultrasonically cleaned for 20 min, then rinsed with ultrapure water, and finally blown with nitrogen. The (100) oriented silicon wafer was immersed in a hydrofluoric acid solution for surface treatment for 30 s, immersed in an organic solvent and ultrasonically cleaned for 20 min, then rinsed with ultrapure water, and finally blown with nitrogen to obtain a hard substrate. The reaction chamber was evacuated to a background vacuum of 5×10 -5Pa, the flow limiting valve opening is 15%, Ar is introduced into the ion source at a flow rate of 30sccm, the ion source current is set to 450mA, the power is set to 200W, the anode ion source is turned on, the Ar is ionized, the working vacuum is 1.5Pa, and the silicon wafer is pre-cleaned with Ar plasma for 30min to obtain a soft-etched hard substrate.

[0058] (2) Nitrogen and Ar were introduced into the ion source and reaction chamber at flow rates of 22.5 sccm and 7.5 sccm, respectively. The ion source current was set to 100 mA and the power was set to 50 W. The ion source was turned on to ionize the nitrogen to obtain nitrogen plasma. Under the working gas pressure of 0.8 Pa (reactive co-sputtering pressure), the sputtering power of the Al target was set to 450 W and the sputtering power of the Sc target was set to 300 W. The RF power was turned on, and the nitrogen plasma reacted with the co-sputtered Al and Sc metal atoms for sputtering for 1 h. A ScAlN film with high crystallinity and high C-axis preferential orientation (thickness of 800 nm, atomic percentage of Sc of 30 at%) was obtained 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 the preparation method and Example 1 is that the pre-cleaning of the silicon wafer by Ar plasma in step (1) is omitted, and reactive co-sputtering is directly performed on the surface of the silicon wafer. The rest of the preparation method and parameters are consistent with 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 the preparation method and Example 1 is that the process of ionizing nitrogen in step (2) is omitted, and nitrogen is directly used as the reaction gas. The rest of the preparation method and parameters are consistent with 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 the preparation method and Example 1 is that in step (1), the pre-cleaning working vacuum is adjusted to 0.2 Pa, and the rest of the preparation method and parameters are consistent with 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 the preparation method and Example 1 is that in step (1), the pre-cleaning working vacuum is adjusted to 2.0 Pa, and the rest of the preparation method and parameters are consistent with Example 1.

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

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

[0069] Table 1

[0070]

[0071] The test results show that:

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

[0073] (2) By comparing 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 0.5Pa-1.5Pa. Within this vacuum degree, a ScAlN film with high crystallinity and high C-axis preferential orientation growth can be obtained, thereby ensuring that the ScAlN film has a high quality. If the pre-cleaning working vacuum degree is low, the prepared ScAlN film will have more defects and will not be able to perform C-axis preferential orientation growth; if the pre-cleaning working vacuum degree is high, the hard substrate will be severely etched, which will cause 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 (a process of soft etching the surface of the hard substrate) + nitrogen plasma assisted reaction + dual-target co-sputtering, and the working vacuum degree of the pre-cleaning is 0.5Pa-1.5Pa. The prepared ScAlN film has high crystallinity and grows along a specific C-axis preferential 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 a specific implementation mode 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 shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a ScAlN film with high crystallinity and high C-axis preferred orientation, characterized in that: The preparation method comprises the following steps: (1) placing a first target material at a first magnetron sputtering target position, placing a second target material at a second magnetron sputtering target position, and using an inert gas plasma to pre-clean the hard substrate at a working vacuum of 0.5 Pa-1.5 Pa to achieve a soft etching effect, thereby obtaining a soft-etched hard substrate; (2) Using nitrogen plasma as a reaction gas and an inert gas as a working gas, the first target material and the second target material are simultaneously reactively co-sputtered on the surface of the soft-etched hard substrate to obtain a ScAlN film with high crystallinity and high C-axis preferred orientation.

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

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

4. The preparation method according to claim 1, characterized in that: The inert gas plasma in step (1) is obtained by passing an inert gas into an ion source for ionization; The inert gas includes argon.

5. The preparation method according to claim 4, characterized in that: In the process of introducing the inert gas into the ion source for ionization, the power of the ion source is 100W-400W; The ion source includes any one of an anode ion source, a radio frequency ion source or a Kaufman ion source.

6. The preparation method according to claim 1, characterized in that: The nitrogen plasma in step (2) is obtained by passing nitrogen into an ion source for ionization, and the flow ratio of the nitrogen to the inert gas in step (2) is (1-3):1; The inert gas in step (2) includes argon.

7. The preparation method according to claim 6, characterized in that: In the process of introducing nitrogen into the ion source for ionization, the power of the ion source is 50W-200W.

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

9. A ScAlN film with high crystallinity and high C-axis preferred orientation, characterized in that: The ScAlN film with high crystallinity and high C-axis preferred orientation Prepared according to the preparation method according to any one of claims 1 to 8.

10. Application of a ScAlN film with high crystallinity and high C-axis preferred orientation, characterized in that: The ScAlN film with high crystallinity and high C-axis preferred orientation prepared by the preparation method according to any one of claims 1 to 8, or the ScAlN film with high crystallinity and high C-axis preferred orientation according to claim 9, is used to prepare a high-frequency filter.

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