AlScN film substrate and preparation method and application thereof

Abstract

The invention discloses an AlScN thin film substrate and a preparation method and application thereof. The preparation method comprises the following steps: after growing an Al thin film layer on the surface of a substrate, carrying out first heat treatment; then, after a first AlN layer, a second AlN layer and an AlN island structure layer are sequentially grown on the surface of the Al thin film layer, secondary heat treatment is carried out, the thickness of the AlN island structure layer is hx, hx is larger than or equal to 5 nm and smaller than or equal to 25 nm, the temperature for growing the AlN island structure layer is Tx, Tx is larger than or equal to 870 DEG C and smaller than or equal to 950 DEG C, the temperature for secondary heat treatment is Ty, and Ty is larger than or equal to 1100 DEG C and smaller than or equal to 1300 DEG C; and growing an AlScN thin film on the surface of the AlN island structure layer subjected to the second heat treatment by adopting a physical vapor deposition method to obtain the AlScN thin film substrate. According to the method, the AlN island structure is grown on the surface of the second AlN layer at low temperature, so that the AlN island structures grown at low temperature can be combined, dislocation aggregation is formed at the combination position, the AlN island structure subjected to the second heat treatment provides a good growth platform for PVD-AlScN, and the problem of overlarge warping of an epitaxial wafer caused by stress accumulation generated by heteroepitaxy is solved.

Description

Technical Field

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

[0002] With the advent of the Sub-6G era, the new generation of filters faces the challenge of higher frequencies. Traditional lithium niobate and lithium tantalate materials are difficult to apply to the development of higher frequency filters due to the characteristics of the materials themselves.

[0003] 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 acoustic wave propagation speed. In addition, the addition of Sc elements to AlN forms an AlScN composite material, which can effectively improve the piezoelectric coefficient of the material. At the same time, ultra-thin AlScN films can be grown epitaxially by PVD (Physical Vapor Deposition) or MOCVD (Metal-organic Chemical Vapor Deposition), which makes AlScN films one of the ideal piezoelectric materials in the field of FBAR filters (Film Bulk Acoustic Resonator).

[0004] Affected by heteroepitaxial growth, AlScN films formed on large-sized substrates have great residual stress, which may cause cracking of the AlScN film or seriously affect the subsequent MEMS (Micro-Electro-Mechanical Systems) process. The MOCVD+PVD method can combine the MOCVD high-quality seed layer and PVD stress regulation to achieve large-sized crack-free AlScN films. However, PVD regulation will introduce compressive stress, and the transformation of tensile stress to compressive stress at the interface will generate a large number of grain boundaries / domain boundaries that cross the c-axis lattice, seriously affecting the piezoelectric constant in the c-axis direction. Summary of the invention

[0005] The embodiments of the present application provide an AlScN thin film substrate and a preparation method and application thereof, which can solve the problem that a large number of grain boundaries / domain boundaries that cross the c-axis lattice and affect the piezoelectric constant during the growth of the AlScN thin film are caused by the sudden change of stress at the interface.

[0006] In a first aspect, the present application provides a method for preparing an AlScN thin film substrate, comprising: Providing a substrate, and performing a first heat treatment after growing an Al thin film layer on the surface of the substrate; Growing a first AlN layer on the surface of the Al thin film layer; growing a second AlN layer on a surface of the first AlN layer; After growing an AlN island structure layer on the surface of the second AlN layer, performing a second heat treatment, wherein the thickness of the AlN island structure layer is hx, 5nm≤hx≤25nm, the temperature for growing the AlN island structure layer is Tx, 870°C≤Tx≤950°C, and the temperature for the second heat treatment is Ty, 1100°C≤Ty≤1300°C; An AlScN film is grown on the surface of the AlN island structure layer after the second heat treatment by using a physical vapor deposition method to obtain an AlScN film substrate.

[0007] In some embodiments, the temperature of the first heat treatment is T0, 1200°C≤T0≤1250°C.

[0008] In some embodiments, the temperature for growing the first AlN layer is T1, 850°C≤T1≤900°C.

[0009] In some embodiments, the temperature of the second AlN layer is T2, 1100°C≤T2≤1150°C.

[0010] In some embodiments, the thickness of the first AlN layer is h1, 10 nm ≤ h1 ≤ 20 nm; In some embodiments, the thickness of the second AlN layer is h2, 80nm≤h2≤90nm.

[0011] In some embodiments, the pressure range for growing the first AlN layer is 70 Torr ~ 80 Torr, the flow range of TMAl is 150 sccm ~ 250 sccm, and the flow range of NH3 is 4.5 sccm ~ 5.5 sccm.

[0012] In some embodiments, the pressure range for growing the second AlN layer is 35 Torr ~ 50 Torr, the flow range of TMAl is 250 sccm ~ 350 sccm, and the flow range of NH3 is 18 sccm ~ 24 sccm.

[0013] In some embodiments, the pressure range for growing the AlN island structure layer is 70 Torr ~ 80 Torr, the flow range of TMAl is 150 sccm ~ 250 sccm, and the flow range of NH3 is 4.5 sccm ~ 5.5 sccm.

[0014] In some embodiments, the first heat treatment has a pressure range of 35 Torr to 50 Torr, a N2 flow range of 2 slm to 10 slm, and a time range of 5 min to 15 min; In some embodiments, the second heat treatment has a pressure range of 35 Torr to 50 Torr, a H2 flow range of 5 slm to 20 slm, and a time range of 1 min to 5 min.

[0015] In some embodiments, the physical vapor deposition method is a magnetron sputtering method, and the Ar flow range of the magnetron sputtering method is 20 sccm ~30 sccm, the N2 flow range is 120 sccm ~180 sccm, the pressure range is 0.2Torr ~ 0.4Torr, the temperature range is 500℃ ~ 700℃, and the power range is 1800w ~ 3000w.

[0016] In some embodiments, the AlScN film is Al 1-x Sc x N film, 0≤x≤0.4.

[0017] In some embodiments, the thickness of the AlScN film is h4, 100nm≤h4≤1000nm.

[0018] In a second aspect, the present application provides an AlScN thin film substrate obtained by the preparation method as described above.

[0019] In a third aspect, the present application provides an application of the AlScN thin film substrate as described above, wherein the application includes a filter.

[0020] Based on the AlScN thin film substrate and its preparation method and application in the embodiment of the present application, a first AlN layer is grown on the Al layer at low temperature, and a second AlN layer is grown on the surface of the first AlN layer at high temperature, and then an AlN island structure layer is grown on the surface of the second AlN layer at low temperature, so that the low-temperature grown AlN island structure layers can be merged and form dislocation aggregation at the merger. On the one hand, the low-temperature grown AlN island structure layer can relax part of the interface stress, which can provide a larger space for the subsequent PVD growth of ScAlN film with biased tensile stress growth. On the other hand, the dislocation aggregation points at the merger of the low-temperature grown AlN island structure layers can induce the dislocation aggregation here to extend upward along the c-axis, further reducing the defects across the c-axis. At the same time, after a layer of AlN island structure layer is grown at low temperature, a second heat treatment is performed. The AlN island structure layer after the second heat treatment provides a good growth platform for PVD growth of ScAlN film, further ensuring the crystal quality of the AlScN film substrate, improving the lattice order of the AlScN film, reducing the dislocation density and surface roughness of the AlScN film, and at the same time, reducing the problem of excessive warping of the epitaxial wafer caused by stress accumulation caused by heteroepitaxial growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A schematic diagram of a process for preparing an AlScN thin film substrate according to an embodiment of the present application; Figure 2 This is a schematic diagram of the structure of the AlScN thin film substrate of Example 1 of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. 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.

[0024] The inventors found that the MOCVD+PVD method can combine the MOCVD growth of high-quality AlN seed crystal layer and the PVD regulation of the stress of the AlScN film to achieve the growth of large-sized crack-free AlScN films. By reducing the power during the PVD growth process, the overall growth process of the AlScN film can be grown in a bias stress mode, and the tensile stress brought by the MOCVD growth of the AlN film forms stress compensation, reduces the warping of the epitaxial wafer (i.e., the AlScN film substrate), and avoids stress accumulation leading to cracking of the AlScN film. However, the process of the sudden change from tensile stress to compressive stress causes a large number of dislocations, domain boundaries or grain boundaries oriented across the c-axis (i.e., the substrate thickness direction) in the range of 200nm-300nm (even derived to the surface of the AlScN film) near the interface of the two adjacent films. Such defects will affect the piezoelectric effect along the c-axis direction, reduce the piezoelectric constant in the c-axis direction, and thus affect the overall performance of the FBAR filter using the AlScN film substrate. Based on this, the embodiment of the present application provides a method for preparing an AlScN film substrate.

[0025] like Figure 1 FIG. 1 is a flow chart of a method for preparing an AlScN thin film substrate provided in an embodiment of the present application. The method for preparing an AlScN thin film substrate comprises: Step S1, providing a substrate, and performing a first heat treatment after growing an Al thin film layer on the surface of the substrate.

[0026] Step S2: growing a first AlN layer on the surface of the Al thin film layer.

[0027] Step S3, growing a second AlN layer on the surface of the first AlN layer.

[0028] Step S4, after growing the AlN island structure layer on the surface of the second AlN layer, performing a second heat treatment, wherein the thickness of the AlN island structure layer is hx, 5nm≤hx≤25nm, the temperature for growing the AlN island structure layer is Tx, 870℃≤Tx≤950℃, and the temperature for the second heat treatment is Ty, 1100℃≤Ty≤1300℃.

[0029] Step S5, growing an AlScN thin film on the surface of the AlN island structure layer after the second heat treatment by using a physical vapor deposition method to obtain an AlScN thin film substrate.

[0030] In the present application, a first AlN layer is grown on the Al layer at low temperature, and a second AlN layer is grown on the surface of the first AlN layer at high temperature, and then an AlN island structure is grown on the surface of the second AlN layer at low temperature, so that the low-temperature grown AlN island structures can be merged and form dislocation aggregation at the merging point. On the one hand, the low-temperature grown AlN island structure layer can relax part of the interface stress, and can provide more space for the tensile stress growth of the ScAlN film in the subsequent PVD process. On the other hand, the low-temperature grown AlN island structure layer can relax part of the stress caused by ScAlN / AlN to a certain extent, and can also serve as a transition layer for the transformation of tensile stress to compressive stress at the interface between MOCVD-grown multi-layer AlN layers (first AlN layer, second AlN layer and AlN island structure layer) and PVD-grown ScAlN film, thereby alleviating the lattice disorder caused by the sudden change of stress. At the same time, after a layer of AlN island structure layer is grown at low temperature, a second heat treatment is performed. The second heat treatment uses high temperature, which can achieve atomic reshoots to a certain extent and improve the lattice orientation difference brought by the AlN island structure layer. At the same time, high-temperature H2 has a certain etching effect, which can etch dislocations or defects on the surface of the AlN island structure layer to form holes. These holes can also relax stress during the secondary growth process and cooperate with the AlN island structure layer to greatly alleviate the stress accumulation phenomenon, thereby greatly alleviating the contradictory relationship between stress and piezoelectric constant, and achieving the unity of low warpage and high piezoelectric constant.

[0031] Among them, the temperature Tx for growing the AlN island structure layer satisfies 870℃≤Tx≤950℃. In this temperature range, the AlN single crystal nucleation layer can be epitaxially grown to form an AlN island structure, and the nucleation size is small, which reduces the surface roughness of the subsequent ScAlN. The temperature Ty of the second heat treatment satisfies 1100℃≤Ty≤1300℃. In this temperature range, atomic reshoots can be achieved to a certain extent, the lattice orientation difference brought by the AlN island structure layer can be improved, and the atomic rearrangement of the entire AlN film (including the first AlN layer, the second AlN layer and the AlN island structure layer) caused by excessive temperature is avoided, and stress mutations are prevented from causing cracks in the epitaxial wafer (i.e., the AlScN film substrate). The thickness hx of the AlN island structure layer satisfies 5nm≤hx≤25nm. In this thickness range, a complete AlN island structure can be formed, and the surface roughness caused by the AlN island structure layer being too thick is avoided. Preferably, 10nm≤hx≤20nm.

[0032] In addition, it should be noted that in the embodiment of the present application, from a microscopic point of view, there are certain protrusions on the surface of the grown first AlN layer, the second AlN layer and the AlN island structure layer. The first AlN layer mainly relaxes the stress of the second AlN layer, and at the same time creates protrusions to promote the formation of lateral epitaxy during the growth of the second AlN layer, thereby improving the crystal quality of the second AlN layer. However, due to the high crystal quality of the second AlN layer, if the AlScN layer continues to grow on it, it will cause excessive stress accumulation, resulting in large warping or epitaxial wafer cracking. Therefore, an AlN island structure layer is inserted in the middle to relax the stress caused by AlScN. At the same time, based on the AlN island structure layer, the upper AlScN layer can rearrange atoms during the annealing process to form a better lattice. While improving the quality, it avoids stress accumulation caused by lattice rearrangement.

[0033] In step S1, before growing the Al thin film layer on the substrate surface, the surface perpendicular to the thickness direction of the substrate is cleaned, that is, the substrate surface is cleaned. The temperature range of cleaning the substrate is 800°C ~ 900°C, the pressure range is 70Torr ~ 80Torr, the flow range of H2 is 5sccm ~ 20sccm, and the time range is 2min ~ 10min. The oxides and impurities on the substrate surface are removed by H2 reduction.

[0034] In some embodiments, the substrate provided in step S1 may be a Si substrate, a sapphire substrate or a SiC substrate. The thickness of the substrate ranges from 430 nm to 1100 nm and the surface area may be 2-12 inches. That is, in the embodiment of the present application, an Al thin film layer, a first AlN layer, a second AlN layer, an AlN island structure layer and an AlScN thin film may be sequentially grown on the surface of a larger substrate.

[0035] In some embodiments, the temperature range for growing the Al thin film layer on the substrate surface is 850°C~900°C, the pressure range is 70Torr~80Torr, the flow range of TMAl is 10sccm~30sccm, and the Al thin film layer with a thickness range of 1≤Hd≤10 atomic layers is grown at low temperature.

[0036] In some embodiments, the temperature of the first heat treatment is T0, 1200°C≤T0≤1250°C, and the first heat treatment is performed within this temperature range, wherein the substrate is a Si-containing substrate, and the first heat treatment is performed in a nitrogen atmosphere, and in the nitrogen atmosphere, nitrogen can form an ultra-thin AlN atomic layer with the Al atomic layer of the Al thin film layer on the substrate, preventing AlN from growing directly on the substrate to form a Si-Al-N mixture, thereby improving the consistency of subsequent AlN nucleation orientation and improving the crystal quality of AlN.

[0037] In some embodiments, the pressure range of the first heat treatment is 35 Torr~50 Torr, the flow range of N2 is 2slm~10 slm, and the time range is 0.8min~1.2min. Under this treatment condition, in a nitrogen atmosphere, an ultra-thin AlN atomic layer can be formed with the Al atomic layer on Si, preventing AlN from directly growing on the substrate to form a Si-Al-N mixture, reducing the nucleation orientation of the subsequent first AlN layer, and improving the crystal quality of the first AlN layer.

[0038] In some embodiments, the temperature for growing the first AlN layer is T1, 850°C≤T1≤900°C. Within this temperature range, an AlN single crystal nucleation layer (i.e., the first AlN layer) can be epitaxially grown, which can provide a lateral epitaxial substrate for the subsequent growth of the second AlN layer and the AlN island structure layer. The lateral epitaxial growth induces mutual annihilation of dislocations, reduces the dislocation density of the second AlN layer and the AlN island structure layer, and improves the crystal quality of the second AlN layer and the AlN island structure layer.

[0039] In some embodiments, the pressure range of growing the first AlN layer is 70 Torr ~ 80 Torr, the flow range of TMAl is 150 sccm ~ 250 sccm, and the flow range of NH3 is 4.5 sccm ~ 5.5 sccm.

[0040] In some embodiments, the thickness of the first AlN layer satisfies: 13 nm≤h1≤17 nm, and more preferably, h1 is 15 nm.

[0041] In some embodiments, the temperature for growing the second AlN layer is T2, 1100°C≤T2≤1150°C. In this temperature range, the surface diffusion length of Al atoms is longer, and it is easier to migrate to an ideal lattice position, forming two-dimensional growth, thereby improving the crystal quality of the second AlN layer and reducing the surface roughness of the second AlN layer.

[0042] In some embodiments, the pressure range for growing the second AlN layer is 35 Torr-50 Torr, the flow rate range of TMAl is 250 sccm-350 sccm, and the flow rate range of NH 3 is 18 sccm-24 sccm.

[0043] In some embodiments, the thickness of the second AlN layer is h2, 80nm≤h2≤90nm. In this thickness range, the surface of the first AlN layer can be filled by two-dimensional growth, and the surface roughness of the second AlN layer is low, and sufficient space is provided for dislocation annihilation at the merging point of the second AlN layer and the AlN island structure layer, so as to avoid the emergence of unannihilated dislocations, improve the crystal quality of the AlN island structure layer, and at the same time, avoid the greater in-plane stress caused by the excessive thickness of the second AlN layer. Preferably, 83nm≤h2≤87nm, and more preferably, h2 is 85nm.

[0044] In some embodiments, the pressure range for growing the AlN island structure layer is 70 Torr ~ 80 Torr, the flow range of TMAl is 150 sccm ~ 250 sccm, and the flow range of NH3 is 4.5 sccm ~ 5.5 sccm.

[0045] In some embodiments, the second heat treatment has a pressure range of 35 Torr to 50 Torr, a H2 flow range of 5 slm to 20 slm, and a time range of 1 min to 5 min. Under these treatment conditions.

[0046] In some embodiments, the AlScN film is Al 1-x Sc x N film, 0≤x≤0.4.

[0047] In some embodiments, the physical vapor deposition method is a magnetron sputtering method, and the AlScN film is grown on the surface of the AlN island structure layer by the magnetron sputtering method, including: the Sc element content in the AlSc alloy target is 0 at%-40 at%, the Ar flow range is 20sccm~30 sccm, the N2 flow range is 120 sccm~180 sccm, the pressure range is 0.2Torr~0.4Torr, the temperature range is 500℃~700℃, and the power range is 1800w~3000w.

[0048] In some embodiments, the thickness of the AlScN film is h4, 100nm≤h4≤1000nm. Within this thickness range, the requirements of the subsequent FBAR filter for the thickness of the epitaxial film can be met, and stress accumulation caused by excessive thickness can also be avoided.

[0049] The present application also provides an AlScN thin film substrate, such as Figure 2 , which is a schematic structural diagram of an AlScN thin film substrate according to an embodiment of the present application. The AlScN thin film substrate is obtained by the preparation method described above.

[0050] An embodiment of the present application also provides an application of the AlScN thin film substrate as described above, the application including a filter, and the filter is a FBAR filter.

[0051] The following will introduce the method for preparing the AlScN thin film substrate of the present application in conjunction with specific embodiments.

[0052] Example 1 Step S110, provide a 6-inch, 675 μm thick Si substrate. Place the Si substrate in an organic metal chemical vapor deposition device, introduce H2 with a flow rate of 15 sccm, and clean the surface of the Si substrate at a temperature of 1225° C., a pressure of 40 Torr, and a time of 5 minutes.

[0053] Step S120 , introducing TMAl with a flow rate of 20 sccm, at a temperature of 850° C., a pressure of 75 Torr, and a time of 45 s, to grow an Al thin film layer with a thickness of 5 atomic layers on the Si substrate.

[0054] Step S130, introducing N2 with a flow rate of 10 slm, performing the first heat treatment at a temperature of 870° C., a pressure of 45 Torr, and a time of 2 min.

[0055] Step S140, introducing TMAl with a flow rate of 205 sccm and NH3 with a flow rate of 5 slm, at a temperature of 870°C, a pressure of 75 Torr, and a time of 1 min, to grow a first AlN layer with a thickness h1 of 10 nm on the surface of the Al thin film layer.

[0056] Step S150, introducing TMAl with a flow rate of 300 sccm and NH3 with a flow rate of 22 slm, at a temperature of 1125° C., a pressure of 40 Torr, and a time of 20 min, to grow a second AlN layer with a thickness h2 of 85 nm on the surface of the first AlN layer.

[0057] Step S160, introducing TMAl with a flow rate of 205 sccm and NH3 with a flow rate of 5 slm, at a temperature of 900°C, a pressure of 75 Torr, and a time of 2 min, to grow an AlN island structure layer with a thickness hx of 10 nm on the surface of the second AlN layer.

[0058] Step S170, introducing H2 at a flow rate of 10 slm, at a temperature of 1200°C, a pressure of 40 Torr, and a time of 3 min, to perform a second heat treatment.

[0059] Step S180, placing the Si substrate with the Al thin film layer, the first AlN layer, the second AlN layer and the AlN island structure layer grown on the surface thereof in a magnetron sputtering device, wherein the content of Sc element in the AlSc alloy target of the magnetron sputtering device is 20at%, the flow rate of Ar is 25sccm, the flow rate of N2 is 125sccm, and the pressure is selected to be 0.28Torr, the temperature is 650℃, and the power of the magnetron sputtering device is 2000w, and a layer of Al with a thickness of h4 of 500nm is deposited on the surface of the AlN island structure layer. 0.8 Sc 0.2 N thin film to obtain an AlScN thin film substrate.

[0060] Example 2 The difference from Example 1 is: In step S160, an AlN island structure layer with a thickness hx of 5 nm is grown on the surface of the second AlN layer at a growth temperature of 870°C.

[0061] Example 3 The difference from Example 1 is: In step S160 , an AlN island structure layer with a thickness hx of 25 nm is grown on the surface of the second AlN layer at a growth temperature of 950° C.

[0062] Comparative Example 1 The difference from Example 1 is: In step S160 , after an AlN island structure layer with a thickness hx of 10 nm is grown on the surface of the second AlN layer, step S180 is directly performed.

[0063] Comparative Example 2 The difference from Example 1 is: In step S160, an AlN island structure layer with a thickness hx of 30 nm is grown on the surface of the second AlN layer.

[0064] Comparative Example 3 The difference from Example 1 is: In step S160, an AlN island structure layer with a thickness hx of 3 nm is grown on the surface of the second AlN layer.

[0065] Comparative Example 4 The difference from Example 1 is: In step S160 , an AlN island structure layer with a thickness hx of 10 nm is grown on the surface of the second AlN layer at a growth temperature of 800° C.

[0066] Comparative Example 5 The difference from Example 1 is: In step S160 , an AlN island structure layer with a thickness hx of 10 nm is grown on the surface of the second AlN layer at a growth temperature of 1000° C.

[0067] Comparative Example 6 The difference from Example 1 is: In step S170, a second heat treatment is performed at a temperature of 1000°C.

[0068] Comparative Example 7 The difference from Example 1 is: In step S170, a second heat treatment is performed at a temperature of 1350°C.

[0069] Comparative Example 8 The difference from Example 1 is: In step S180, the power of the magnetron sputtering device is 1500w.

[0070] Comparative Example 9 The difference from Example 1 is: In step S180, the power of the magnetron sputtering device is 3300w.

[0071] The AlScN thin film substrates obtained in Examples 1 to 3 and Comparative Examples 1 to 10 were subjected to the following tests: (1) Detection of Al using atomic force microscopy 1-x Sc x N film surface roughness.

[0072] (2) Use an optical microscope (OM) with a maximum magnification of more than 1000 times to detect Al 1-x Sc x Surface cracks of N film.

[0073] (3) Using X-ray diffraction (XRD) to detect Al 1-x Sc x XRD rocking curve of (002) plane of N thin film (thickness 500nm).

[0074] (4) Using backscattered electron diffraction (EBSD) to test Al 1-x Scx Al on the surface of N film 1-x Sc x N film - c-axis orientation.

[0075] (5) Using D33 tester to detect Al 1-x Sc x Piezoelectric constant of N film.

[0076] (6) Use photoluminescence tester (PL) to detect Al 1-x Sc x NThe warpage of the film.

[0077] The test results of the AlScN thin film substrates obtained from Examples 1 to 3 and Comparative Examples 1 to 9 are shown in Table 1.

[0078] Table 1

[0079] According to the results in Table 1, it can be seen that the AlScN thin film substrate obtained in Example 1 of the present application has no cracks in the AlScN thin film. 1-x Sc x The rocking curve of the XRD (002) plane of the N film (thickness 500nm) can reach more than 1990arcsec, and the crack-free AlScN film presents a high C-axis orientation, and the piezoelectric constant is close to that of an ideal crystal.

[0080] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate an orientation or position relationship based on the orientation or position relationship shown in the drawings, it is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0081] 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 substrate, characterized in that: include: Providing a substrate, and performing a first heat treatment after growing an Al thin film layer on the surface of the substrate; Growing a first AlN layer on the surface of the Al thin film layer; growing a second AlN layer on a surface of the first AlN layer; After growing an AlN island structure layer on the surface of the second AlN layer, performing a second heat treatment, wherein the thickness of the AlN island structure layer is hx, 5nm≤hx≤25nm, the temperature for growing the AlN island structure layer is Tx, 870°C≤Tx≤950°C, and the temperature for the second heat treatment is Ty, 1100°C≤Ty≤1300°C; An AlScN film is grown on the surface of the AlN island structure layer after the second heat treatment by using a physical vapor deposition method to obtain an AlScN film substrate.

2. The method for preparing an AlScN thin film substrate according to claim 1, characterized in that: The temperature of the first heat treatment is T0, 1200°C≤T0≤1250°C; The temperature for growing the first AlN layer is T1, 850° C.≤T1≤900° C.; The temperature for growing the second AlN layer is T2, 1100°C≤T2≤1150°C.

3. The method for preparing an AlScN thin film substrate according to claim 1, characterized in that: The thickness of the first AlN layer is h1, 10nm≤h1≤20nm; The thickness of the second AlN layer is h2, 80nm≤h2≤90nm.

4. The method for preparing an AlScN thin film substrate according to claim 1, characterized in that: The pressure range for growing the first AlN layer is 70 Torr ~ 80 Torr, the flow range of TMAl is 150 sccm ~ 250 sccm, and the flow range of NH3 is 4.5 sccm ~ 5.5 sccm.

5. The method for preparing an AlScN thin film substrate according to claim 1, characterized in that: The pressure range for growing the second AlN layer is 35 Torr ~50 Torr, the flow range of TMAl is 250 sccm ~350 sccm, and the flow range of NH3 is 18 sccm ~24 sccm.

6. The method for preparing an AlScN thin film substrate according to claim 1, characterized in that: The pressure range for growing the AlN island structure layer is 70 Torr ~ 80 Torr, the flow range of TMAl is 150 sccm ~ 250 sccm, and the flow range of NH3 is 4.5 sccm ~ 5.5 sccm.

7. The method for preparing an AlScN thin film substrate according to claim 1, characterized in that: The pressure range of the first heat treatment is 35 Torr ~ 50 Torr, the flow range of N2 is 2slm-10slm, and the time range is 5min ~ 15min; The pressure range of the second heat treatment is 35 Torr ~ 50 Torr, the flow range of H2 is 5slm ~ 20slm, and the time range is 1min ~ 5min.

8. The method for preparing an AlScN thin film substrate according to claim 1, characterized in that: The physical vapor deposition method is a magnetron sputtering method, wherein the flow rate range of Ar in the magnetron sputtering method is 20 sccm to 30 sccm, the flow rate range of N2 is 120 sccm to 180 sccm, the pressure range is 0.2 Torr to 0.4 Torr, the temperature range is 500° C. to 700° C., and the power range is 1800w to 3000w; Wherein, the AlScN film is Al 1-x Sc x N film, 0≤x≤0.4; The thickness of the AlScN film is h4, 100nm≤h4≤1000nm.

9. An AlScN thin film substrate, characterized in that: The method is obtained by the preparation method described in any one of claims 1 to 8.

10. An application of the AlScN thin film substrate according to claim 9, characterized in that: The applications include filters.

Images