AlScN film and preparation method and application thereof

Abstract

The invention discloses an AlScN thin film and a preparation method and application thereof, and the method comprises the following steps: S100, epitaxially growing a GaN film layer on a sapphire substrate, the surface roughness of the GaN film layer being within 0.5 nm, S200, sequentially growing an AlGaN layer and an AlN layer on the GaN film layer in the step S100 in situ, the thickness of the AlGaN layer being 50-150 nm, and S300, carrying out ion bombardment on the AlN layer in the step S200, the method comprises the following steps of: S100, growing an AlN intermediate layer with a high / low table top on the AlN intermediate layer in the step S300 to obtain an AlN intermediate layer with a high / low table top, S400, growing an AlN epitaxial film with the thickness of 50nm-200nm on the AlN intermediate layer in the step S300, and S500, depositing an AlScN layer on the AlN epitaxial film in the step S400 to obtain the AlScN thin film. According to the preparation method, the AlScN thin film which is high in crystal quality, low in surface roughness and easy to peel can be prepared.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to an AlScN film and a preparation method and application thereof. Background Art

[0002] Aluminum nitride (AlN) is a new type of piezoelectric material. Compared with traditional materials such as lithium niobate, lithium tantalate, and zinc oxide, it has the characteristics of high thermal conductivity, high stability, and high sound wave propagation speed. Adding Sc elements to AlN to form AlScN composite materials can effectively improve the piezoelectric coefficient of the material, making AlScN an ideal piezoelectric material in the field of FBAR filters. At present, it is difficult to grow crack-free AlScN films on large-size Si substrates using metal organic chemical vapor deposition (MOCVD) technology. Although the use of magnetron sputtering (PVD) technology can effectively solve the problem of cracks, the crystal quality of the grown AlScN film is poor and the surface roughness is high. Summary of the invention

[0003] In view of this, the present application provides an AlScN film and a preparation method and application thereof. The AlScN film prepared in the present application has better crystal quality and lower residual stress. When the AlScN film prepared in the present application is assembled in an FBAR filter, the FBAR filter has a better quality factor.

[0004] In the first aspect, the present application provides a method for preparing an AlScN thin film, the preparation method comprising the following steps: S100, epitaxially growing a GaN film layer on a sapphire substrate, the thickness of the GaN film layer being 0.5 μm to 2 μm, the half-width of the (002) crystal plane of the GaN film layer being within 200 arcsec, the half-width of the (102) crystal plane being within 500 arcsec, and the surface roughness being within 0.5 nm. S200, sequentially in-situ growing an AlGaN layer and an AlN layer on the GaN film layer in step S100, the thickness of the AlGaN layer being 50 nm to 150 nm, and the thickness of the AlN layer being 20 nm to 70 nm. S300, ion bombarding the AlN layer in step S200 to obtain an AlN intermediate layer having a nanoscale pit structure. S400, growing an AlN epitaxial film on the AlN intermediate layer in step S300, wherein the thickness of the AlN epitaxial film is 50nm to 200nm, the half-width of the (002) crystal plane of the AlN epitaxial film is within 300arcsec, the half-width of the (102) crystal plane of the AlN epitaxial film is within 1500arcsec, and the surface roughness is within 1nm. S500, depositing an AlScN layer on the AlN epitaxial film in step S400, thereby obtaining an AlScN thin film. The present application firstly epitaxies a high-quality GaN template (i.e., a GaN film layer) on sapphire, and the GaN template serves as the bottom buffer layer of AlScN, providing an ultra-high-quality substrate for AlScN. Secondly, the present application sequentially in-situ grows an AlGaN layer and an AlN layer on the GaN film layer. The AlGaN layer, as the transition layer interface between the GaN film layer and the AlN layer, is conducive to stress relaxation and can greatly relax most of the stress. At the same time, it can also cut off the threading dislocations that emerge, preventing the dislocations from continuing to extend upward. Moreover, the present application further performs ion bombardment on the above-mentioned AlN layer to form a nanoscale pit structure (high / low table). The nanoscale pit can promote the lateral epitaxy of the upper AlN epitaxial film and reduce dislocations. At the same time, it can also relax the interface stress between the bottom GaN film layer and the upper AlScN layer, reducing the internal stress of the final epitaxial film (AlScN film). The present application then grows an AlN epitaxial film on the bombarded AlN layer (AlN intermediate layer), so that an ultra-high-quality AlN epitaxial film can be formed, providing an excellent base layer for the subsequent AlScN piezoelectric film. At the same time, the present application further optimizes the process conditions of MOCVD technology and PVD technology, which can achieve the crystal quality and surface roughness of the AlScN layer continuing the GaN film layer, thereby improving the comprehensive performance of the PVD-AlScN film. In addition, the purpose of using the GaN film layer is to provide a sacrificial layer for laser stripping for the substrate laser stripping technology, thereby perfectly transferring the AlScN to the Si substrate with the filter bottom structure and electrodes already prepared, greatly reducing the difficulty of the subsequent filter chip process.

[0005] In some embodiments, in step S100, epitaxially growing a GaN film layer on a sapphire substrate includes: sputtering an AlN seed crystal layer on the sapphire substrate by a PVD device, then placing the AlN-3D layer in an MOCVD device for epitaxial growth, and then epitaxially growing the GaN film layer on the GaN-3D layer, wherein the thickness of the GaN-3D layer is 40 nm.

[0006] Specific process parameter examples are shown in Table 1:

[0007] Table 1

[0008]

[0009] Note: “ / ” means no relevant parameters.

[0010] The exemplary process parameters are intended to epitaxially grow an ultra-high-quality GaN template on sapphire. Using the exemplary process parameters, the half-width at half-maximum of the prepared GaN film layer (002) crystal plane can be within 200 arcsec, the half-width at half-maximum of the (102) crystal plane can be within 500 arcsec, and the surface roughness can be within 0.5 nm.

[0011] In some embodiments, in step S200, sequentially in-situ growing an AlGaN layer and an AlN layer on the GaN film layer in step S100 includes: using MOCVD equipment, adjusting the pressure of a reaction chamber of the MOCVD equipment to 30 torr to 50 torr, adjusting the gallium source flow rate to 100 sccm to 200 sccm, adjusting the aluminum source flow rate to 300 sccm to 500 sccm, adjusting the ammonia flow rate to 10 sccm to 20 sccm, adjusting the temperature to 1040° C. to 1100° C., and growing the AlGaN layer, wherein the mass percentage of Al element in the AlGaN layer is 35 wt% to 60 wt%; thereafter, closing the gallium source, adjusting the aluminum source flow rate to 600 sccm to 700 sccm, adjusting the reaction chamber temperature to 1150° C. to 1250° C., and growing the AlN layer. The present application sequentially in-situ grows an AlGaN layer and an AlN layer on a GaN film layer through MOCVD technology. The AlGaN transition layer can alleviate the lattice mismatch between the GaN film layer and the AlN layer, reduce the strong strain caused by stress on AlN, and reduce the generation of interface dislocations under strong coupling. At the same time, the present application further regulates the content of the Al element in the AlGaN layer within the range of 35wt% to 60wt%. This is because when the content of the Al element in the AlGaN layer is not appropriate, there is still a large interface stress between the AlN layer and the AlGaN layer. If the thickness of the AlGaN layer is too thin (for example, less than 50nm), it cannot play a role in overstressing. If the thickness of the AlGaN layer is too thick (for example, greater than 200nm), the AlGaN itself will introduce new stress, resulting in a more complex stress state.

[0012] The specific process parameters are shown in Table 2:

[0013] Table 2

[0014]

[0015] In some embodiments, in step S300, ion bombarding the AlN layer in step S200 includes: using a PVD device, closing the nitrogen channel of the reaction chamber of the PVD device and opening the argon channel of the reaction chamber of the PVD device, which is recorded as the first PVD device, and introducing argon into its reaction chamber, the argon flow rate is 100sccm to 200sccm, the DC power is 2500W to 3500W, and the reaction time is 20s to 2min. Argon is bombarded by high-speed electrons to form Ar ions, and the Ar ions are accelerated by the electric field to bombard the surface of the epitaxial film, and the surface is bombarded by the Ar ions to sputter AlN to form an AlN intermediate layer with uniformly distributed micro-nano-sized high and low terraces. The AlN intermediate layer can promote the lateral epitaxy of the upper AlN epitaxial film and reduce dislocations. It can also relax the interface stress between part of the bottom GaN film layer and the upper AlScN film, reducing the internal stress of the final epitaxial film. At the same time, the construction method using this structure is more convenient and simplifies the process steps compared to traditional photolithography patterns and nanoimprint patterns, optimizes the epitaxial wafer, and improves production efficiency. Preferably, the argon gas flow rate in the reaction chamber of the first PVD device is 100sccm to 150sccm, the DC power of the first PVD device is 2800W to 3200W, and the reaction time is 30s to 1min.

[0016] In some embodiments, in step S400, growing an AlN epitaxial film on the AlN intermediate layer in step S300 includes: using MOCVD equipment, the pressure of the reaction chamber of the MOCVD equipment is 30torr to 50torr, the aluminum source flow rate is 600sccm to 700sccm, the ammonia flow rate is 10sccm to 20sccm, and the reaction chamber temperature is 1150°C to 1250°C. By adjusting the condition parameters of the MOCVD equipment within the above range, an AlN epitaxial film with ultra-high quality can be formed, providing an excellent base layer for the subsequent AlScN film. Preferably, the thickness of the AlN epitaxial film is 100nm to 150nm.

[0017] In some embodiments, in step S500, depositing an AlScN layer on the AlN epitaxial film in step S400 includes: using a PVD device, opening a nitrogen channel and an argon channel of a reaction chamber of the PVD device, denoted as a second PVD device, adjusting the temperature of the reaction chamber of the second PVD device to 500°C to 750°C, introducing argon and nitrogen into the reaction chamber, the argon flow rate is 20sccm to 40sccm, the nitrogen flow rate is 120sccm to 240sccm, and the DC power is 1500W to 2000W. Preferably, the reaction chamber temperature of the second PVD device is 600°C to 700°C, the argon flow rate in the reaction chamber of the second PVD device is 25sccm to 35sccm, the nitrogen flow rate in the reaction chamber of the second PVD device is 150sccm to 210sccm, and the DC power of the second PVD device is 1700W to 1900W. More preferably, the temperature of the reaction chamber of the second PVD equipment is 650°C, the argon flow rate in the reaction chamber of the second PVD equipment is 30sccm, the nitrogen flow rate in the reaction chamber of the second PVD equipment is 180sccm, and the DC power of the second PVD equipment is 1800W.

[0018] In a second aspect, the present application provides an AlScN film, wherein the AlScN film is prepared by any one of the preparation methods of the first aspect.

[0019] In a third aspect, the present application provides an FBAR high-frequency broadband filter device, wherein the FBAR high-frequency broadband filter device contains an AlScN film, wherein the AlScN film is obtained by any one of the preparation methods of the first aspect above; or, the AlScN film is the AlScN film of the second aspect above. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in combination with embodiments and comparative examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] Example 1

[0022] Preparation method of AlScN film

[0023] S100, epitaxially growing a GaN film layer on a sapphire substrate.

[0024] A layer of AlN seed crystal (20nm) is sputtered on the sapphire substrate by PVD equipment, and then the sputtered epitaxial wafer is placed in MOCVD equipment for high-temperature cleaning (clean). After cleaning, GaN-3D is directly epitaxially grown on the epitaxial wafer, and then GaN is epitaxially grown on GaN-3D. The process parameters are shown in Table 3:

[0025] Table 3

[0026]

[0027] TMGa is trimethylgallium, and its CAS number is: 1445-79-0; TMAl is trimethylaluminum, and its CAS number is: 75-24-1.

[0028] S200 , sequentially in-situ growing an AlGaN layer and an AlN layer on the GaN film layer in step S100 .

[0029] After the AlN layer is grown on GaN by in-situ MOCVD, the pressure of the reaction chamber of the MOCVD equipment is adjusted to 30torr-50torr, the gallium source flow rate is adjusted to 100sccm-200sccm, the aluminum source flow rate is adjusted to 300sccm-500sccm, the ammonia flow rate is adjusted to 10sccm-20sccm, the temperature is adjusted to 1040℃-1100℃, and the AlGaN layer is grown. The mass percentage of Al element in the AlGaN layer is 35wt%-60wt%; then, the gallium source is turned off, the aluminum source flow rate is adjusted to 600sccm-700sccm, the reaction chamber temperature is adjusted to 1150℃-1250℃, and then the AlN layer is grown. The process parameters are shown in Table 4:

[0030] Table 4

[0031]

[0032] S300 , performing ion bombardment on the AlN layer in step S200 to obtain an AlN intermediate layer with uniformly distributed high / low terraces.

[0033] The above epitaxial wafer is placed in the PA cavity of the PVD equipment (the PA cavity has no target), the nitrogen channel of the reaction cavity of the PVD equipment is closed, and argon gas is introduced into the cavity, and the argon flow rate is 100sccm to 200sccm, preferably 100sccm to 150sccm; the DC power is 2500W to 3500W, preferably the DC power is 2800W to 3200W, and the time is 20s to 2min, and the preferred time is 30s to 1min. Ar gas is bombarded by high-speed electrons to form Ar ions, and the Ar ions are accelerated by the electric field to bombard the surface of the epitaxial film. The surface is bombarded by Ar ions and sputters AlN to form a uniformly distributed high / low table structure. Based on the total area of ​​the AlN layer, the high table accounts for 30% to 60%, and the height difference of the high / low table is 20nm to 100nm. In this way, it is more conducive to the formation of an AlN epitaxial film with ultra-high quality, providing an excellent base layer for the subsequent AlScN piezoelectric film.

[0034] S400 , growing an AlN epitaxial film on the AlN intermediate layer in step S300 .

[0035] The MOCVD equipment is used, the pressure of the reaction chamber of the MOCVD equipment is 30torr~50torr, the flow rate of the aluminum source is 600sccm~700sccm, the flow rate of the ammonia is 10sccm~20sccm, and the temperature of the reaction chamber is 1150℃~1250℃. The growth conditions are shown in Table 5:

[0036] Table 5

[0037] Temperature / ℃ Pressure (torr) TMGa(sccm) TMAl(sccm) <![CDATA[NH 3 (sccm)]]> Thickness(nm) High temperature AlN 1150-1250 30-50 / 600-700 10-20 50-200

[0038] S500 , depositing an AlScN layer on the AlN epitaxial film in step S400 .

[0039] Use PVD equipment, adjust the temperature of the reaction chamber of the PVD equipment to 500℃~750℃, introduce argon into the reaction chamber, the argon flow rate is 20sccm~40sccm, open the nitrogen channel of the reaction chamber of the PVD equipment, the nitrogen flow rate is 120sccm~240sccm, and the DC power is 1500W~2000W. The process parameters are shown in Table 6:

[0040] Table 6

[0041] PVD Equipment temperature Ar(sccm) <![CDATA[N 2 (sccm)]]> Power(W) Interval 500-750 20-40 120-240 1500-2000 Best 600-700 25-35 150-210 1700-1900 More preferred 650 30 180 1800

[0042] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Unless otherwise stated, the parts, percentages and ratios listed are all based on mass.

[0043] Example 1

[0044] Preparation method of AlScN film

[0045] Step 1: Sputter an AlN seed crystal layer on a sapphire substrate using a PVD device, then place the sputtered epitaxial wafer into an MOCVD device for high-temperature cleaning, directly grow a GaN-3D layer on the cleaned epitaxial wafer, and then grow a GaN film layer on the GaN-3D layer. Specific process parameters are shown in Table 7:

[0046] Table 7

[0047]

[0048] Step 2: Adjust the pressure of the reaction chamber of the MOCVD equipment to 40torr, the gallium source flow rate to 150sccm, the aluminum source flow rate to 450sccm, the ammonia flow rate to 15sccm, and the temperature to 1050°C to grow the AlGaN layer; then, turn off the gallium source, adjust the aluminum source flow rate to 600sccm, adjust the reaction chamber temperature to 1150°C, and then grow the AlN layer. The aluminum content in the AlGaN layer is 43%, and the specific process parameters are shown in Table 8:

[0049] Table 8

[0050]

[0051] Step 3: Place the above epitaxial wafer into the PA chamber of the PVD equipment (the PA chamber has no target and the gas bombards the substrate), close the nitrogen channel of the reaction chamber of the PVD equipment, and introduce Ar gas into the chamber with a flow rate of 130sccm, a DC power of 3100W, and a time of 1min. The high table accounts for 30% to 60%, and the height difference between the high and low table is 20nm to 100nm.

[0052] Step 4: Use MOCVD equipment, the pressure of the reaction chamber of the MOCVD equipment is 40 torr, the flow rate of the aluminum source is 600 sccm, the flow rate of the ammonia is 15 sccm, and the temperature of the reaction chamber is 1250°C. The specific process parameters are shown in Table 9:

[0053] Table 9

[0054] MOCVD Equipment Temperature(℃) Pressure (torr) TMGa(sccm) TMAl(sccm) <![CDATA[NH 3 (sccm)]]> Thickness(nm) AlN epitaxial film 1250 40 / 600 15 150

[0055] The half-width at half maximum of the (002) crystal plane of the AlN epitaxial film is 592 arcsec, the half-width at half maximum of the (102) crystal plane of the AlN epitaxial film is 1300 arcsec, and the surface roughness of the AlN epitaxial film is 0.239 nm.

[0056] Step 5: Using PVD equipment, adjust the temperature of the reaction chamber of the PVD equipment to 650°C, introduce argon into the reaction chamber with a flow rate of 30 sccm, open the nitrogen channel of the reaction chamber of the PVD equipment with a nitrogen flow rate of 180 sccm, and the DC power is 1800W.

[0057] The half-width at half maximum of the (002) crystal plane of the AlScN film is 1608 arcsec, the half-width at half maximum of the (102) crystal plane is 2800 arcsec, and the RMS value is 0.650 nm.

[0058] Example 2

[0059] Preparation method of AlScN film

[0060] Step 1: epitaxially grow a GaN film layer on a sapphire substrate, see Example 1.

[0061] Step 2: Adjust the pressure of the reaction chamber of the MOCVD equipment to 40torr, the gallium source flow rate to 150sccm, the aluminum source flow rate to 450sccm, the ammonia flow rate to 15sccm, and the temperature to 1050°C to grow the AlGaN layer; then, turn off the gallium source, adjust the aluminum source flow rate to 600sccm, adjust the reaction chamber temperature to 1150°C, and then cyclically grow the AlN transition layer and the AlN layer. The aluminum content in the AlGaN transition layer is 43%, and the specific process parameters are shown in Table 10:

[0062] Table 10

[0063]

[0064] Step 3: Place the above epitaxial wafer into the PA chamber of the PVD equipment (the PA chamber has no target), close the nitrogen channel of the reaction chamber of the PVD equipment, and introduce Ar gas into the chamber at a flow rate of 200 sccm, a DC power of 2500 W, and a time of 2 minutes.

[0065] Step 4: Use MOCVD equipment, the pressure of the reaction chamber of the MOCVD equipment is 40 torr, the aluminum source flow rate is 600 sccm, the ammonia flow rate is 15 sccm, and the reaction chamber temperature is 1250°C. The specific process parameters are shown in Table 11:

[0066] Table 11

[0067] MOCVD Equipment Temperature(℃) Pressure (torr) TMGa(sccm) TMAl(sccm) <![CDATA[NH 3 (sccm)]]> Thickness(nm) AlN epitaxial film 1250 40 / 600 15 150

[0068] Step 5: Using PVD equipment, adjust the temperature of the reaction chamber of the PVD equipment to 500°C, introduce argon into the reaction chamber with a flow rate of 20 sccm, open the nitrogen channel of the reaction chamber of the PVD equipment with a nitrogen flow rate of 120 sccm, and the DC power is 1500W.

[0069] The half-width at half maximum of the (002) crystal plane of the AlScN film is 2234 arcsec, the half-width at half maximum of the (102) crystal plane is 3002 arcsec, and the RMS value is 0.782 nm.

[0070] Example 3

[0071] Step 1: Sputter an AlN seed layer on a sapphire substrate using a PVD device, then place the sputtered epitaxial wafer into an MOCVD device for high-temperature cleaning, directly grow a GaN-3D layer on the cleaned epitaxial wafer, and then grow a GaN film layer on the GaN-3D layer. Specific process parameters are shown in Table 12:

[0072] Table 12

[0073]

[0074]

[0075] Step 2: Adjust the pressure of the reaction chamber of the MOCVD equipment to 40torr, the gallium source flow rate to 150sccm, the aluminum source flow rate to 450sccm, the ammonia flow rate to 15sccm, and the temperature to 1050°C to grow the AlGaN layer; then, turn off the gallium source, adjust the aluminum source flow rate to 600sccm, adjust the reaction chamber temperature to 1150°C, and then grow the AlN layer. The aluminum content in the AlGaN transition layer is 43%, and the specific process parameters are shown in Table 13:

[0076] Table 13

[0077]

[0078] Step 3: Place the above epitaxial wafer into the PA chamber of the PVD equipment (the PA chamber has no target), close the nitrogen channel of the reaction chamber of the PVD equipment, and introduce Ar gas into the chamber with a flow rate of 80sccm, a DC power of 2000W, and a time of 1min. The high table accounts for 15% to 30%, and the height difference between the high and low table is 5nm to 15nm.

[0079] Step 4: Use MOCVD equipment, the pressure of the reaction chamber of the MOCVD equipment is 40 torr, the flow rate of the aluminum source is 600 sccm, the flow rate of the ammonia is 15 sccm, and the temperature of the reaction chamber is 1250°C. The specific process parameters are shown in Table 14:

[0080] Table 14

[0081] MOCVD Equipment Temperature(℃) Pressure (torr) TMGa(sccm) TMAl(sccm) <![CDATA[NH 3 (sccm)]]> Thickness(nm) AlN epitaxial film 1250 40 / 600 15 150

[0082] The half-width at half maximum of the (002) crystal plane of the AlN epitaxial film is 1975 arcsec, and the half-width at half-maximum of the (102) crystal plane is 2904 arcsec.

[0083] Comparative Example 1

[0084] Step 1: Sputter an AlN seed crystal layer on a sapphire substrate using a PVD device, then place the sputtered epitaxial wafer into an MOCVD device for high-temperature cleaning, directly grow a GaN-3D layer on the epitaxial wafer after cleaning, and then grow a GaN film layer on the GaN-3D layer. Specific process parameters are shown in Table 15:

[0085] Table 15

[0086]

[0087] Step 2: Adjust the pressure of the reaction chamber of the MOCVD equipment to 40 torr, the aluminum source flow rate to 600 sccm, the ammonia flow rate to 15 sccm, the reaction chamber temperature to 1150°C, and the AlN layer.

[0088] Step 3: Place the above epitaxial wafer into the PA chamber of the PVD equipment (the PA chamber has no target), close the nitrogen channel of the reaction chamber of the PVD equipment, and introduce Ar gas into the chamber at a flow rate of 130sccm, a DC power of 3100W, and a time of 1min.

[0089] Step 4: Use MOCVD equipment, the pressure of the reaction chamber of the MOCVD equipment is 40 torr, the aluminum source flow rate is 600 sccm, the ammonia flow rate is 15 sccm, and the reaction chamber temperature is 1250°C. The specific process parameters are shown in Table 16:

[0090] Table 16

[0091] MOCVD Equipment Temperature(℃) Pressure (torr) TMGa(sccm) TMAl(sccm) <![CDATA[NH 3 (sccm)]]> Thickness(nm) AlN epitaxial film 1250 40 / 600 15 150

[0092] The half-width at half maximum of the (002) crystal plane of the AlN epitaxial film is 1521 arcsec, and the half-width at half-maximum of the (102) crystal plane is 2688 arcsec.

[0093] Comparative Example 2

[0094] Compared with the embodiment, the difference is that there is no step 3 in comparative example 2, that is, the AlN epitaxial film is directly in-situ grown on the AlN layer in comparative example 2. The half-width of the (002) crystal plane of the AlN epitaxial film is 1688 arcsec, and the half-width of the (102) crystal plane is 2785 arcsec.

[0095] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing an AlScN thin film, characterized in that: The preparation method comprises the following steps: S100, epitaxially growing a GaN film on a sapphire substrate, with a surface roughness within 0.5 nm; S200, sequentially in-situ growing an AlGaN layer and an AlN layer on the GaN film layer in step S100, wherein the thickness of the AlGaN layer is 50 nm to 150 nm; S300, performing ion bombardment on the AlN layer in step S200 to obtain an AlN intermediate layer with high / low terraces; S400, growing an AlN epitaxial film on the AlN intermediate layer in step S300, wherein the thickness of the AlN epitaxial film is 50 nm to 200 nm; S500 , depositing an AlScN layer on the AlN epitaxial film in step S400 to obtain an AlScN thin film.

2. The preparation method according to claim 1, characterized in that: In step S100, epitaxially growing a GaN film layer on a sapphire substrate includes: Sputtering an AlN seed crystal layer on a sapphire substrate by a PVD device, then placing the substrate in an MOCVD device to grow a GaN-3D layer, and then growing the GaN film layer on the GaN-3D layer; The thickness of the GaN-3D layer is 40 nm, and the thickness of the GaN film layer is 0.5 μm to 2 μm.

3. The preparation method according to claim 1, characterized in that: In step S200, sequentially in-situ growing an AlGaN layer and an AlN layer on the GaN film layer in step S100 includes: Using MOCVD equipment, adjusting the pressure of the reaction chamber of the MOCVD equipment to 30 torr to 50 torr, adjusting the gallium source flow rate to 100 sccm to 200 sccm, adjusting the aluminum source flow rate to 300 sccm to 500 sccm, adjusting the ammonia flow rate to 10 sccm to 20 sccm, adjusting the temperature to 1040° C. to 1100° C., growing the AlGaN layer, wherein the mass percentage of Al element in the AlGaN layer is 35 wt% to 60 wt%; then, The gallium source is turned off, the flow rate of the aluminum source is adjusted to 600 sccm-700 sccm, the temperature of the reaction chamber is adjusted to 1150° C.-1250° C., and the AlN layer is grown. The thickness of the AlN layer is 20 nm to 70 nm.

4. The preparation method according to claim 1, characterized in that: In step S300, ion bombarding the AlN layer in step S200 includes: A PVD device is used, the nitrogen channel of the reaction chamber of the PVD device is closed and the argon channel of the reaction chamber of the PVD device is opened, which is recorded as the first PVD device. Argon gas is introduced into the reaction chamber of the first PVD device, the argon gas flow rate is 100 sccm to 200 sccm, the DC power is 2500 W to 3500 W, and the reaction time is 20 s to 2 min.

5. The preparation method according to claim 4, characterized in that: The first PVD device satisfies at least one of the following conditions: (1) The argon gas flow rate in the reaction chamber is 100 sccm to 150 sccm; (2) DC power is 2800W to 3200W; (3) The reaction time is 30s to 1min.

6. The preparation method according to claim 1, characterized in that: In step S400, growing an AlN epitaxial film on the AlN intermediate layer in step S300 includes: The MOCVD equipment is used, the pressure of the reaction chamber of the MOCVD equipment is 30torr-50torr, the flow rate of the aluminum source is 600sccm-700sccm, the flow rate of the ammonia gas is 10sccm-20sccm, and the temperature of the reaction chamber is 1150°C-1250°C.

7. The preparation method according to claim 4, characterized in that: In step S500, depositing an AlScN layer on the AlN epitaxial film in step S400 includes: Use a PVD device, open the nitrogen channel and the argon channel of the reaction chamber of the PVD device, record it as the second PVD device, adjust the temperature of the reaction chamber of the second PVD device to 500℃~750℃, introduce argon and nitrogen into its reaction chamber, the argon flow rate is 20sccm~40sccm, the nitrogen flow rate is 120sccm~240sccm, and the DC power is 1500W~2000W.

8. The preparation method according to claim 7, characterized in that: The second PVD equipment satisfies at least one of the following conditions: (1) The temperature of the reaction chamber is 600°C to 700°C; (2) The argon gas flow rate in the reaction chamber is 25 sccm to 35 sccm; (3) The nitrogen flow rate in the reaction chamber is 150 sccm to 210 sccm; (4) DC power is 1700W~1900W.

9. An AlScN film, characterized in that: The AlScN film is prepared by the preparation method according to any one of claims 1 to 8.

10. A FBAR high-frequency broadband filter device, characterized in that: The FBAR high-frequency broadband filter device contains an AlScN film; Wherein, the AlScN film is obtained by the preparation method according to any one of claims 1 to 8; or, The AlScN film is the AlScN film according to claim 9.

Images