A method for preparing an aluminum nitride thin film and a device based on the aluminum nitride thin film

Abstract

The present invention relates to a method for preparing an aluminum nitride thin film and a device based on the aluminum nitride thin film. The preparation method includes: providing an aluminum nitride substrate, the aluminum nitride substrate including a substrate and an aluminum nitride layer having a first temperature, which are stacked; providing a protective layer on a surface of the aluminum nitride layer facing away from the substrate, the protective layer including a concave region and a flat region disposed around an outer periphery of the concave region, and a root mean square roughness RMS of a surface of the flat region facing the aluminum nitride layer ranges from 0 nm < RMS ≤ 50 nm; and performing a thermal annealing treatment on the aluminum nitride substrate and the protective layer to obtain the aluminum nitride thin film having a second temperature; wherein the second temperature is greater than the first temperature. The method for preparing the aluminum nitride thin film can prepare an aluminum nitride thin film with high crystal quality, low defect density, and high surface uniformity.

Description

Technical Field

[0001] The present application relates to a preparation process of semiconductor materials, and specifically relates to a method for preparing an aluminum nitride thin film and a device based on the aluminum nitride thin film. Background Art

[0002] Aluminum nitride thin films with high crystal quality and low defect density are important underlying structures for group III nitride-based (such as aluminum gallium nitride, etc.) electronic and optoelectronic devices. Due to the high melting point of aluminum nitride material itself and the large bond energy of aluminum-nitrogen covalent bonds, it is difficult to prepare high-quality and low-cost aluminum nitride thin films by the method of pulling single crystals. Aluminum nitride thin films are mostly on hetero-substrates such as silicon carbide, gallium nitride, sapphire, etc., and are usually obtained by physical deposition or chemical deposition methods. However, due to a certain lattice mismatch and thermal mismatch between the aluminum nitride thin film and the hetero-substrate, there are many grains and grain boundaries in the hetero-epitaxial aluminum nitride thin film, and a large number of dislocations exist inside the aluminum nitride thin film.

[0003] The aluminum nitride thin film can be subjected to thermal annealing treatment to recrystallize part of the grains and grain boundaries in the aluminum nitride thin film into a more stable crystal state, so as to reduce the dislocation density inside the aluminum nitride thin film and improve the crystal quality of the aluminum nitride thin film. Usually, in a nitrogen atmosphere, any high temperature from 1773.15K to 1973.15K (such as 1823.15K, 1923.15K, etc.) is used to perform high-temperature thermal annealing on the aluminum nitride thin film. At high temperatures, the surface of the aluminum nitride thin film will decompose. Therefore, the method of placing the samples face to face is adopted to inhibit the decomposition of the surface of the aluminum nitride thin film during high-temperature thermal annealing. However, there is a phenomenon of adhesion between the samples during the annealing process. After peeling off the adhered samples, the surface roughness of the aluminum nitride thin film increases and the uniformity decreases. At the same time, the improvement of the crystal quality of the aluminum nitride thin film by heat treatment in this temperature range is also quite limited. Summary of the Invention

[0004] In view of this, the present application provides a method for preparing an aluminum nitride thin film and a device based on the aluminum nitride thin film. The method for preparing the aluminum nitride thin film can prepare an aluminum nitride thin film with high crystal quality, low defect density and high surface uniformity.

[0005] The present application provides a method for preparing an aluminum nitride thin film. The preparation method includes: providing an aluminum nitride substrate, where the aluminum nitride substrate includes a substrate and an aluminum nitride layer with a first temperature that are stacked; setting a protective layer on the surface of the aluminum nitride layer facing away from the substrate, where the protective layer includes a concave area and a flat area disposed around the outer periphery of the concave area, and the root mean square roughness RMS of the surface of the flat area facing the aluminum nitride layer ranges from 0nm < RMS ≤ 50nm; and performing thermal annealing treatment on the aluminum nitride substrate and the protective layer to obtain the aluminum nitride thin film with a second temperature; wherein, the second temperature is greater than the first temperature.

[0006] Further, the providing of the aluminum nitride substrate includes: providing a substrate; depositing an aluminum nitride layer at a first temperature on the surface of the substrate, and the deposition methods include but are not limited to sputtering, atomic layer deposition, molecular beam epitaxy, chemical vapor deposition, pulsed laser deposition, etc.

[0007] Further, the providing of the aluminum nitride substrate includes: providing a substrate; depositing an aluminum nitride layer at a first temperature on the surface of the substrate by chemical vapor deposition, where the range of temperature T1 is: 723.15K ≤ T1 ≤ 1873.15K; the range of reaction pressure P1 is: 0 Torr < P1 ≤ 800 Torr, and the range of the thickness d1 of the deposited aluminum nitride layer is: 0 nm < d1 ≤ 1000 nm; wherein, the chemical vapor deposition method is metalorganic chemical vapor deposition.

[0008] Further, the protective layer further includes one or more convex structures, one convex structure is disposed on the surface of the concave area facing the aluminum nitride layer, and a plurality of convex structures are spaced apart on the surface of the concave area facing the aluminum nitride layer. The convex structure has an end face facing the aluminum nitride layer, and the flat sheet area has a preset surface facing the aluminum nitride layer, and the end face is not higher than the preset surface.

[0009] Further, the distance d2 between the two farthest points within the area enclosed by the orthographic projection of the convex structure on the surface of the aluminum nitride facing the protective layer ranges from: 0.1 μm ≤ d2 ≤ 50000 μm; the minimum distance d3 between any two adjacent convex structures ranges from: 0 μm ≤ d3 ≤ 50000 μm.

[0010] Further, along the stacking direction of the substrate and the aluminum nitride layer, the maximum height d4 of the convex structure ranges from: 0 μm < d4 ≤ 200 μm.

[0011] Further, the heat annealing treatment of the aluminum nitride substrate and the protective layer includes: performing heat annealing treatment in an ammonia atmosphere.

[0012] Further, the heat annealing treatment of the aluminum nitride substrate and the protective layer includes: performing heat annealing treatment in an ammonia atmosphere; wherein, the range of the heat annealing temperature T2 is: 773.15K ≤ T2 ≤ 2273.15K; the range of the heat annealing time t1 is: 0 min < t1 ≤ 180 min.

[0013] Further, the aluminum nitride thin film after the heat annealing treatment satisfies at least one of the following conditions: the root mean square roughness of the surface of the aluminum nitride thin film facing away from the substrate is less than 3.3 nm, and the dislocation density of the aluminum nitride thin film is less than 5×10 10 cm-2 The full width at half maximum (FWHM) value of the X-ray rocking curve of the aluminum nitride thin film along the

[0002] direction is less than 0.3°, and the FWHM value of the X-ray rocking curve of the aluminum nitride thin film along the [10-12] direction is less than 0.6°.

[0014] This application also provides a device, which includes the aluminum nitride thin film prepared by the preparation method provided in this application and a functional layer, and the functional layer is disposed on the surface of the aluminum nitride thin film facing away from the substrate.

[0015] In the preparation method of the aluminum nitride thin film provided in this application, a protective layer is disposed on the surface of the aluminum nitride layer having the first temperature facing away from the substrate, which is beneficial to preventing the decomposition of the aluminum nitride layer during the thermal annealing process, and is beneficial to improving the crystal quality of the aluminum nitride thin film having the second temperature and reducing the defect density of the aluminum nitride thin film. In addition, the flat area surrounds the concave area, that is, when the protective layer is disposed on the surface of the aluminum nitride layer facing away from the substrate, the flat area is in contact with the outer periphery of the aluminum nitride layer. The root mean square roughness of the surface of the flat area facing the aluminum nitride layer satisfies the range of 0 nm < RMS ≤ 50 nm, and the surface of the flat area facing the aluminum nitride layer is smoother, so that the contact between the flat area and the aluminum nitride layer is closer, and the concave area is separated from the external environment, which is beneficial to suppressing the decomposition of the aluminum nitride layer during the thermal annealing process, is beneficial to improving the crystal quality of the aluminum nitride thin film, and effectively reduces the defect density of the aluminum nitride thin film through the thermal annealing treatment. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of this application, the drawings required for the implementation will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic flow chart of the preparation method of the aluminum nitride thin film according to an embodiment of this application;

[0018] Figure 2 It is a schematic diagram of the stacked structure of the substrate, aluminum nitride layer and protective layer according to an embodiment of this application;

[0019] Figure 3 It is a side view of the protective layer according to an embodiment of this application;

[0020] Figure 4 It is a schematic diagram of the stacked structure of the substrate, aluminum nitride layer and protective layer according to another embodiment of this application;

[0021] Figure 5 It is a side view of the protective layer according to another embodiment of this application;

[0022] Figure 6 Top view of the protective layer according to an embodiment of the present application;

[0023] Figure 7 Side view of the protective layer according to another embodiment of the present application;

[0024] Figure 8 Schematic diagram of the stacked structure of the substrate, aluminum nitride layer and protective layer according to another embodiment of the present application;

[0025] Figure 9 Schematic diagram of the process for providing a low-temperature aluminum nitride thin film according to an embodiment of the present application;

[0026] Figure 10 Schematic diagram of the structure of the aluminum nitride thin film according to an embodiment of the present application;

[0027] Figure 11 Schematic diagram of the structure of the device according to an embodiment of the present application;

[0028] Figure 12 Schematic diagram of the structure of the ultraviolet light-emitting diode according to an embodiment of the present application.

[0029] Explanation of reference numerals:

[0030] 100 - Aluminum nitride thin film, 110 - Aluminum nitride substrate, 111 - Substrate, 112 - Aluminum nitride layer, 130 - Protective layer, 131 - Concave area, 1311 - Protrusion structure, 1312 - End face, 132 - Body part, 133 - Flat area, 134 - Preset surface, 135 - Groove, 200 - Ultraviolet light-emitting diode, 210 - Light-emitting layer, 211 - Light-emitting unit, 220 - Driving substrate, 300 - Device, 310 - Functional layer. Detailed description of the embodiments

[0031] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0032] In the description and claims of this application and the above-mentioned drawings, terms such as "first" and "second" are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include steps or units not listed, or may optionally further include other steps or units inherent to these processes, methods, products or devices.

[0033] Reference to "embodiment" or "embodiment mode" herein means that a specific feature, structure or characteristic described in connection with the embodiment or embodiment mode can be included in at least one embodiment of this application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] Aluminum nitride thin film is an important underlying structure for high-performance group III nitride-based (such as aluminum gallium nitride, etc.) electronic and optoelectronic devices. Usually, a heteroepitaxial method is used to deposit an aluminum nitride layer on a hetero-substrate such as silicon carbide, gallium nitride, sapphire, etc. by physical or chemical methods. However, there is a certain lattice mismatch and thermal mismatch between the aluminum nitride layer and the hetero-substrate, and the nitrogen-aluminum covalent bond of aluminum nitride itself has a large bond energy, resulting in a relatively large defect density in the aluminum nitride layer. Therefore, it is usually necessary to perform thermal annealing on the aluminum nitride layer. When the annealed sample is a single piece, the surface of the annealed sample on which the aluminum nitride layer is deposited is stacked with the smooth surface of a brand-new substrate in a face-to-face manner; when the annealed sample is two pieces, the surfaces of the two annealed samples on which the aluminum nitride layer is deposited are stacked together in a face-to-face manner. The above-mentioned sample is placed in a high-temperature annealing furnace, and in a nitrogen atmosphere, within the range of an annealing temperature of 1373.15 K to 2073.15 K (such as 1373.15 K, 1573.15 K, 1973.15 K or 2073.15 K, etc.), the above-mentioned sample is thermally annealed to finally obtain an aluminum nitride thin film.

[0035] In the process of preparing the above-mentioned aluminum nitride thin film, nitrogen is used as the protective gas for thermal annealing. Since nitrogen is stable in nature and cannot decompose and provide -N groups at the thermal annealing temperature of 1373.15K to 2073.15K, it is impossible to inhibit the decomposition of the aluminum nitride layer into -Al and -N at the thermal annealing temperature of 1373.15K to 2073.15K, resulting in relatively poor crystal quality and still a large defect density of the prepared aluminum nitride thin film. In addition, during the thermal annealing process, when the annealed sample is a single piece, the aluminum nitride layer will partially adhere to the brand-new smooth substrate after annealing; when the annealed sample is two pieces, the aluminum nitride layers of the two samples will adhere together after annealing, making the surface morphology of the finally obtained aluminum nitride thin film uneven, which is not conducive to the further preparation of high-performance devices.

[0036] Please refer to Figures 1 to 3 , an embodiment of the present application provides a method for preparing an aluminum nitride thin film 100, and the preparation method includes:

[0037] S101, providing an aluminum nitride substrate 110, where the aluminum nitride substrate 110 includes a substrate 111 and an aluminum nitride layer 112 having a first temperature, which are stacked.

[0038] Optionally, the material of the substrate 111 includes at least one of silicon, silicon carbide, gallium nitride, aluminum oxide, etc.

[0039] Preferably, in some embodiments, the material of the substrate 111 is aluminum oxide.

[0040] It can be understood that the value of the first temperature Ta satisfies the range of 723.15K ≤ Ta ≤ 1873.15K. Specifically, the value of the first temperature Ta can be, but is not limited to, 723.15K, 773.15K, 793.15K, 813.15K, 853.15K, 873.15K, 933.15K, 953.15K, 973.15K, 993.15K, 1073.15K, 1133.15K, 1193.15K, 1273.15K, 1333.15K, 1393.15K, 1473.15K, 1533.15K, 1593.15K, 1673.15K, 1733.15K, 1793.15K, 1873.15K, etc.

[0041] S102, providing a protective layer 130 on the surface of the aluminum nitride layer 112 facing away from the substrate 111, where the protective layer 130 includes a concave area 131 and a flat area 133 disposed around the outer periphery of the concave area 131, and the root mean square roughness RMS of the surface of the flat area 133 facing the aluminum nitride layer 112 ranges from: 0nm < RMS ≤ 50nm.

[0042] Understandably, the protective layer includes a body portion 132, the body portion 132 having a preset surface 134 facing the aluminum nitride layer 112 and a groove 135 recessed from the preset surface 134. The recessed area 131 covers the groove 135, and the flat piece area 133 is disposed around the outer periphery of the groove 135.

[0043] Understandably, in the embodiment of the present application, the substrate 111, the aluminum nitride layer 112, and the protective layer 130 are sequentially stacked. In other words, the surface of the substrate 111 on which the aluminum nitride layer 112 is deposited is placed opposite to the side of the protective layer 130 provided with the flat piece area 133 and the recessed area 131, so as to prevent nitrogen and aluminum elements in the aluminum nitride layer 112 from evaporating from the surface of the aluminum nitride layer 112 during the thermal annealing process, thereby inhibiting the decomposition of the aluminum nitride layer 112.

[0044] Specifically, the root mean square roughness RMS value of the surface of the flat piece area 133 facing the aluminum nitride layer 112 can be, but is not limited to, 0.1 nm, 1 nm, 1.6 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, 33 nm, 37 nm, 39 nm, 42 nm, 43 nm, 46 nm, and 50 nm, etc. When the root mean square roughness RMS value of the surface of the flat piece area 133 facing the aluminum nitride layer 112 satisfies the range 0 nm < RMS ≤ 50 nm, the flat piece area 133 is in closer contact with the aluminum nitride layer 112, which is beneficial to separating the recessed area 131 from the outside, is beneficial to inhibiting the evaporation of nitrogen and aluminum elements in the aluminum nitride layer 112 from the surface of the aluminum nitride layer 112 during the thermal annealing process, thereby inhibiting the decomposition of the aluminum nitride layer 112, is beneficial to improving the crystal quality of the aluminum nitride thin film 100, and is also beneficial to the peeling of the aluminum nitride thin film 100 from the protective layer 130 after thermal annealing. When the root mean square roughness RMS value of the surface of the flat piece area 133 facing the aluminum nitride layer 112 is greater than 50 nm, the surface of the flat piece area 133 facing the aluminum nitride layer 112 is relatively rough, and it is difficult for the protective layer 130 to be in close contact with the aluminum nitride layer 112, and it is difficult to separate the recessed area 131 from the external environment, which is not beneficial to inhibiting the evaporation of nitrogen and aluminum elements in the aluminum nitride layer 112 from the surface of the aluminum nitride layer 112 during the thermal annealing process, reduces the crystal quality of the aluminum nitride thin film 100, and it is difficult to effectively reduce the defect density of the aluminum nitride thin film 100 through thermal annealing treatment.

[0045] S103, thermally anneal the aluminum nitride substrate 110 and the protective layer 130 to obtain the aluminum nitride thin film 100 having a second temperature; wherein, the second temperature is greater than the first temperature.

[0046] Understandably, the value of the second temperature Tb satisfies the range 773.15K ≤ Tb ≤ 2273.15K. Specifically, the value of the second temperature Tb can be, but is not limited to, 773.15K, 823.15K, 873.15K, 1000.15K, 1078.15K, 1098.15K, 1123.15K, 1173.15K, 1223.15K, 1273.15K, 1300.15K, 1323.15K, 1350.15K, 1373.15K, 1393.15K, 1473.15K, 1533.15K, 1593.15K, 1673.15K, 1733.15K, 1793.15K, 1873.15K, 1973.15K, 2073.15K, 2173.15K, 2273.15K, etc.

[0047] In an embodiment of the present application, a protective layer 130 is provided on the surface of the aluminum nitride layer 112 having the first temperature facing away from the substrate 111, which is beneficial to preventing the aluminum nitride layer 112 from decomposing during the thermal annealing process, and is beneficial to improving the crystal quality of the aluminum nitride thin film 100 having the second temperature and reducing the defect density of the aluminum nitride thin film 100. In addition, the flat area 133 is disposed around the concave area 131, that is, when the protective layer 130 is provided on the surface of the aluminum nitride layer 112 facing away from the substrate 111, the flat area 133 is in contact with the outer periphery of the aluminum nitride layer 112, and the concave area 131 is in contact with the area of the aluminum nitride layer 112 far from the outer periphery. In other words, the concave area 131 is in contact with the middle area of the aluminum nitride layer 112. The root mean square roughness of the surface of the flat area 133 facing the aluminum nitride layer 112 satisfies the range 0nm < RMS ≤ 50nm, and the surface of the flat area 133 facing the aluminum nitride layer 112 is smoother, so that the contact between the flat area 133 and the aluminum nitride layer 112 is closer, and the concave area 131 is separated from the external environment, which is beneficial to suppressing the evaporation of nitrogen and aluminum elements from the surface of the aluminum nitride layer 112 during the thermal annealing process, thereby suppressing the decomposition of the aluminum nitride layer 112, being beneficial to improving the crystal quality of the aluminum nitride thin film 100, and effectively reducing the defect density of the aluminum nitride thin film 100 through the thermal annealing process.

[0048] Optionally, in some embodiments, the substrate 111 is a patterned substrate 111. The patterned substrate 111 can change the epitaxy of the aluminum nitride layer 112 from longitudinal to lateral, effectively reducing the dislocation density of the aluminum nitride layer 112. When the aluminum nitride thin film 100 is applied to optoelectronic devices, the aluminum nitride layer 112 with a smaller dislocation density can reduce the non-radiative recombination in the active region and reduce the reverse leakage current, thereby prolonging the service life of the optoelectronic device; in addition, the light emitted from the active region undergoes multiple scatterings at the interface between the aluminum nitride layer 112 and the patterned substrate 111, and the exit angle of the total reflected light changes, increasing the probability of the light of the flip-chip optoelectronic device exiting from the substrate 111, thereby improving the light extraction efficiency.

[0049] Optionally, in some other embodiments, the substrate 111 is a flat substrate 111. Compared with the patterned substrate 111, the flat substrate 111 has a simple preparation process and lower cost, but the performance of the prepared device 300 is relatively poor. When the flat substrate 111 and the aluminum nitride layer 112 are stacked, the aluminum nitride layer 112 epitaxially grows longitudinally on the substrate 111, resulting in a relatively large dislocation density of the aluminum nitride layer 112, which is not conducive to the preparation of high-performance aluminum nitride thin films 100.

[0050] Optionally, in some embodiments, the thickness h1 of the substrate 111 ranges from 200 μm ≤ h1 ≤ 1500 μm. Specifically, the value of the thickness h1 of the substrate 111 can be, but is not limited to, 200 μm, 220 μm, 250 μm, 280 μm, 300 μm, 320 μm, 350 μm, 380 μm, 400 μm, 450 μm, 480 μm, 500 μm, 530 μm, 560 μm, 600 μm, 650 μm, 800 μm, 900 μm, 1150 μm, 1200 μm, 1300 μm, and 1500 μm, etc.

[0051] In the embodiments of the present application, when the thickness h1 of the substrate 111 satisfies the range 200 μm ≤ h1 ≤ 1500 μm, the thickness of the substrate 111 is within a reasonable range, such that after the thermal annealing treatment is completed, the substrate 111 is easy to be peeled off from the aluminum nitride layer 112. When the thickness h1 of the substrate 111 is less than 200 μm, the thickness of the substrate 111 is too small, and after the thermal annealing treatment is completed, it is difficult for the substrate 111 to be peeled off from the aluminum nitride layer 112, resulting in poor surface uniformity of the prepared aluminum nitride thin film 100. When the thickness h1 of the substrate 111 is greater than 1500 μm, the thickness of the substrate 111 is too large, which will increase the production cost of the substrate 111.

[0052] Optionally, in some embodiments, the thickness h2 of the protective layer 130 ranges from 100 μm to 800 μm. Specifically, the value of the thickness h2 of the protective layer 130 can be, but is not limited to, 100 μm, 150 μm, 200 μm, 220 μm, 250 μm, 280 μm, 300 μm, 320 μm, 350 μm, 380 μm, 400 μm, 430 μm, 450 μm, 480 μm, 500 μm, 560 μm, 600 μm, 650 μm, 750 μm, 800 μm, etc.

[0053] It can be understood that the thickness h2 of the protective layer 130 refers to the maximum distance between the two opposite surfaces of the protective layer 130 along the lamination direction of the protective layer 130 and the substrate 111.

[0054] In the embodiments of the present application, when the thickness h2 of the protective layer 130 satisfies the range of 100 μm ≤ h2 ≤ 800 μm, the thickness of the protective layer 130 is within a reasonable range, so that after the thermal annealing treatment is completed, the protective layer 130 is easy to be peeled off from the aluminum nitride layer 112. When the thickness h2 of the protective layer 130 is less than 100 μm, the thickness of the protective layer 130 is too small, and after the thermal annealing treatment is completed, it is difficult for the protective layer 130 to be peeled off from the aluminum nitride layer 112, resulting in poor surface uniformity of the prepared aluminum nitride thin film 100. When the thickness h2 of the protective layer 130 is greater than 800 μm, the thickness of the protective layer 130 is too large, which will increase the production cost of the protective layer 130.

[0055] In some embodiments, providing the aluminum nitride substrate 110 includes: providing a substrate 111; depositing an aluminum nitride layer 112 having a first temperature on the surface of the substrate 111 by physical or chemical methods, and the deposition methods can be, but are not limited to, sputtering, atomic layer deposition, molecular beam epitaxy, chemical vapor deposition, pulsed laser deposition, etc.

[0056] In the embodiments of the present application, the aluminum nitride substrate 110 includes a substrate 111 and an aluminum nitride layer 112 having a first temperature which are sequentially stacked. One surface of the substrate 111 is the deposition surface to be deposited, and an aluminum nitride layer 112 having a first temperature is deposited on the deposition surface to be deposited of the substrate 111 by one of the methods such as sputtering, atomic layer deposition, molecular beam epitaxy, chemical vapor deposition, pulsed laser deposition, etc., which is beneficial to providing a good substrate for the protective layer 130, so that the protective layer 130 is further deposited on the surface of the aluminum nitride layer 112 facing away from the substrate 111.

[0057] Preferably, in some embodiments, the method of depositing the aluminum nitride layer 112 on the surface of the substrate 111 is metal-organic chemical vapor deposition. The method has a relatively high deposition rate of the aluminum nitride layer 112, and the deposited aluminum nitride layer 112 has good uniformity and repeatability.

[0058] Please refer to Figures 4 to 6 , in some embodiments, the protective layer 130 further includes one or more protrusion structures 1311. One protrusion structure 1311 is disposed on the surface of the recessed area 131 facing the aluminum nitride layer 112, and a plurality of the protrusion structures 1311 are spaced apart on the surface of the recessed area 131 facing the aluminum nitride layer 112. The protrusion structure 1311 has an end face 1312 facing the aluminum nitride layer. The flat sheet area 133 has a preset surface 134 facing the aluminum nitride layer 112, and the end face 1312 is not higher than the preset surface 134. In other words, the protective layer 130 includes a main body portion 132 and at least one protrusion structure 1311. The main body portion 132 has a preset surface 134 facing the aluminum nitride layer 112 and a groove 135 recessed from the preset surface 134. The protrusion structures 1311 are spaced apart in the groove 135. The protrusion structure 1311 has an end face 1312 facing the aluminum nitride layer 112, and the end face 1312 is not higher than the preset surface 134.

[0059] Optionally, in some embodiments, the preset surface 134 and the end face 1312 are coplanar. In other words, the preset surface 134 and the end face 1312 are flush. In some other embodiments, the end face 1312 is lower than the preset surface 134.

[0060] Optionally, the recessed area 131 and the protrusion structure 1311 are obtained by etching a flat sheet, or the end face 1312 can be made not higher than the preset surface 134 by grinding, polishing, etc.

[0061] In an embodiment of the present application, the protruding structure 1311 is disposed in the recessed area 131, and the end face 1312 of the protruding structure 1311 is not higher than the preset surface 134. When a protective layer 130 is disposed on the surface of the aluminum nitride layer 112 facing away from the substrate 111, the protective layer 130 can be stacked with the aluminum nitride layer 112 flatly, avoiding unevenness of the aluminum nitride substrate 110 caused by the uneven surface of the protective layer 130 facing the aluminum nitride, improving the surface uniformity of the aluminum nitride thin film 100, and being beneficial to further fabricating high-performance devices 300. In addition, the recessed area 131 can be separated from the external environment, which is beneficial to suppressing the decomposition of the aluminum nitride layer 112 during the thermal annealing process, beneficial to improving the crystal quality of the aluminum nitride thin film 100, and effectively reducing the defect density of the aluminum nitride thin film 100 through the thermal annealing treatment. When the preset surface 134 is lower than the end face 1312, the aluminum nitride layer 112 cannot be in close contact with the flat area 133, so that the recessed area 131 cannot be effectively separated from the external environment, which is not beneficial to suppressing the decomposition of the aluminum nitride layer 112 during the thermal annealing process, reducing the crystal quality of the aluminum nitride thin film 100, and it is difficult to effectively reduce the defect density of the aluminum nitride thin film 100 through the thermal annealing treatment. Furthermore, when the protective layer 130 includes one protruding structure 1311, it is beneficial to save raw materials and simplify the assembly process. When the protective layer 130 includes a plurality of protruding structures 1311, compared with the solution of only setting one protruding structure 1311, the plurality of protruding structures 1311 can provide support for the aluminum nitride 112, which is beneficial to improving the surface uniformity of the aluminum nitride thin film 100.

[0062] It can be understood that a plurality of protruding structures 1311 are disposed on the surface of the recessed area 131 facing the aluminum nitride layer 112 at intervals, and the roughness of the recessed area 131 is greater than that of the flat area 133; in other words, the flat area 133 is smoother than the recessed area 131.

[0063] Optionally, the protruding structure 1311 can be, but is not limited to, a cone, a pyramid, a frustum of a pyramid, etc.

[0064] Preferably, the protruding structure 1311 is a cone. Compared with other protruding structures 1311, the cone can minimize the contact area between the recessed area 131 and the aluminum nitride layer 112, increase the roughness of the recessed area 131, and the manufacturing process of the cone is simple, which is beneficial to reducing the manufacturing cost of the recessed area 131.

[0065] Optionally, in some embodiments, the value of the height difference h3 between the preset surface 134 and the end face 1312 satisfies 0 nm ≤ h3 ≤ 50 nm. Specifically, the value of the height difference h3 between the preset surface 134 and the end face 1312 may be, but is not limited to, 0 nm, 5 nm, 8 nm, 15 nm, 18 nm, 20 nm, 25 nm, 28 nm, 30 nm, 35 nm, 38 nm, 40 nm, 43 nm, 45 nm, 50 nm, etc.

[0066] In the embodiments of the present application, the value of the height difference h3 between the preset surface 134 and the end face 1312 satisfies the range 0 nm ≤ h3 ≤ 50 nm, so that the end face 1312 of the convex structure 1311 can provide support for the aluminum nitride layer 112, so that the aluminum nitride layer 112 will not be deformed due to its own gravity during the thermal annealing process, so that the prepared aluminum nitride thin film 100 has good surface uniformity. In addition, the end face 1312 of the convex structure 1311 is lower than the preset surface 134, so that the contact area between the convex structure 1311 of the concave region 131 and the aluminum nitride layer 112 is small or almost zero, thereby reducing the contact area between the protective layer 130 and the aluminum nitride layer 112, so that the adhesion between the aluminum nitride layer 112 and the protective layer 130 is small. When the thermal annealing process ends, the probability of adhesion between the aluminum nitride layer 112 and the protective layer 130 is reduced, so that the surface of the aluminum nitride thin film 100 has high surface uniformity, which is beneficial to further preparing high-performance devices 300.

[0067] In some embodiments, when the aluminum nitride substrate 110 and the protective layer 130 are closely stacked together, the positive projection area of the concave region 131 of the protective layer 130 on the surface facing away from the aluminum nitride layer 112 and the positive projection of the surface of the protective layer 130 facing away from the aluminum nitride layer 112 are concentric circle structures. The diameter of the positive projection area of the concave region 131 on the surface of the protective layer 130 facing away from the aluminum nitride layer 112 is D1, and the diameter of the surface of the protective layer 130 facing away from the aluminum nitride layer 112 is D2, then 0.6D2 ≤ D1 ≤ 0.95D2. Specifically, the diameter D1 of the concave region 131 may be, but is not limited to, 0.6D2, 0.63D2, 0.68D2, 0.71D2, 0.74D2, 0.78D2, 0.81D2, 0.83D2, 0.84D2, 0.86D2, 0.89D2, 0.93D2, 0.95D2, etc.

[0068] When the diameter D1 of the projection area of the concave area 131 on the surface of the protective layer 130 facing away from the aluminum nitride layer 112 and the diameter D2 of the surface of the protective layer 130 facing away from the aluminum nitride layer 112 satisfy the conditional formula 0.6D2 ≤ D1 ≤ 0.95D2, the area of the concave area 131 and the area of the flat area 133 are within a reasonable range, so that the flat area 133 can be in close contact with the protective layer 130 to inhibit the decomposition of the aluminum nitride layer 112 during the thermal annealing process, and the concave area 131 can improve the adhesion between the aluminum nitride layer 112 and the protective layer 130, so that the prepared aluminum nitride thin film 100 has high crystal quality, low defect density, low cost and high surface uniformity. When the diameter D1 of the concave area 131 is less than 0.6D2, the diameter of the concave area 131 is too small, so that the area of the concave area 131 is small. Then, during the thermal annealing process, the effect of the concave area 131 on improving the adhesion between the aluminum nitride layer 112 and the protective layer 130 is poor and a small device 300 area is caused, resulting in poor surface uniformity and high cost of the aluminum nitride thin film 100. When the diameter D1 of the concave area 131 is greater than 0.95D2, the diameter of the concave area 131 is too large, so that the area of the concave area 131 is large and the area of the flat area 133 is small, which is not conducive to the close contact between the protective layer 130 and the aluminum nitride layer 112. It is difficult for the concave area 131 to be separated from the external environment, which is not conducive to inhibiting the decomposition of the aluminum nitride layer 112 during the thermal annealing process, resulting in poor crystal quality and large defect density of the aluminum nitride thin film 100.

[0069] Preferably, in some embodiments, the diameter D1 of the concave area 131 = 0.85D2. The area of the concave area 131 and the area of the flat area 133 are within a reasonable range, so that the flat area 133 can be in close contact with the protective layer 130 to inhibit the decomposition of the aluminum nitride layer 112 during the thermal annealing process, and the concave area 131 can improve the adhesion between the aluminum nitride layer 112 and the protective layer 130. The prepared aluminum nitride thin film 100 has high crystal quality, low defect density and high surface uniformity.

[0070] Optionally, in some embodiments, on a plane perpendicular to the stacking direction of the substrate 111 and the aluminum nitride layer 112, the contact area of the concave area 131 per unit area with the aluminum nitride layer 112 is smaller than the contact area of the flat area 133 per unit area with the aluminum nitride layer 112. It can be understood that the direction perpendicular to the stacking direction of the substrate 111 and the aluminum nitride layer 112 can be the thickness direction of the aluminum nitride thin film 100 to be processed.

[0071] In an embodiment of the present application, the recessed area 131 includes one or a plurality of protruding structures 1311 arranged at intervals, and an end surface 1312 of the protruding structure 1311 is coplanar with a preset surface 134 of the protective layer 130, so that along a stacking direction perpendicular to the substrate 111 and the aluminum nitride layer 112, a contact area of the recessed area 131 per unit area with the aluminum nitride layer 112 is smaller than a contact area of the flat area 133 per unit area with the aluminum nitride layer 112. The smaller contact area of the recessed area 131 with the aluminum nitride layer 112 results in a smaller adhesion force between the aluminum nitride layer 112 and the protective layer 130. When the thermal annealing process ends, the probability of adhesion between the aluminum nitride layer 112 and the protective layer 130 decreases, and the surface of the aluminum nitride thin film 100 has a higher surface uniformity, which is beneficial to further fabricating a high-performance device 300.

[0072] In some embodiments, on a plane along a stacking direction perpendicular to the substrate 111 and the aluminum nitride layer 112, a contact area of the recessed area 131 per unit area with the aluminum nitride layer 112 is 9.75% to 64% of a contact area of the flat area 133 per unit area with the aluminum nitride layer 112. Specifically, the contact area of the recessed area 131 per unit area with the aluminum nitride layer 112 can be, but is not limited to, 9.75%, 10%, 15%, 17%, 19%, 21%, 25%, 29%, 33%, 38%, 45%, 48%, 50%, 56%, 60%, 64%, etc. of the contact area of the flat area 133 per unit area with the aluminum nitride layer 112.

[0073] In an embodiment of the present application, when the contact area of the concave region 131 per unit area with the aluminum nitride layer 112 is 9.75% to 64% of the contact area of the flat region 133 per unit area with the aluminum nitride layer 112, the contact area of the concave region 131 per unit area with the aluminum nitride layer 112 is within a reasonable range, the processing difficulty of the convex structure 1311 is relatively small, and the contact area between the concave region 131 and the aluminum nitride layer 112 is relatively small. When the thermal annealing process ends, the area where the aluminum nitride layer 112 adheres to the protective layer 130 is relatively small, so that the obtained aluminum nitride thin film 100 has high surface uniformity. When the contact area of the concave region 131 per unit area with the aluminum nitride layer 112 is less than 9.75% of the contact area of the flat region 133 per unit area with the aluminum nitride layer 112, the contact area of the concave region 131 per unit area with the aluminum nitride layer 112 is too small, which increases the processing difficulty of the convex structure 1311 in the concave region 131. When the contact area of the concave region 131 per unit area with the aluminum nitride layer 112 is greater than 64% of the contact area of the flat region 133 per unit area with the aluminum nitride layer 112, the contact area of the concave region 131 per unit area with the aluminum nitride layer 112 is too large, so that the contact area between the concave region 131 and the aluminum nitride layer 112 is too large. When the thermal annealing process ends, the area where the aluminum nitride layer 112 adheres to the protective layer 130 is relatively large, so that the surface uniformity of the obtained aluminum nitride thin film 100 is poor.

[0074] Please refer to Figure 7 and Figure 8 , optionally, in some embodiments, both opposite surfaces of the protective layer 130 have concave regions 131. In this embodiment, when performing thermal annealing treatment, an aluminum nitride substrate 110 can be provided on both opposite surfaces of the protective layer 130, and the aluminum nitride layer 112 is disposed facing the protective layer 130. In other words, when performing thermal annealing treatment, the substrate 111, the aluminum nitride layer 112, the protective layer 130, the aluminum nitride layer 112, and the substrate 111 are sequentially stacked. Compared with the scheme of providing one protective layer 130 for one aluminum nitride substrate 110, in the embodiment of the present application, only one protective layer 130 needs to be provided for two aluminum nitride substrates 110, and only two protective layers 130 need to be provided for four aluminum nitride substrates 110, and so on. This is beneficial to reducing the usage amount of the protective layer 130 by half, simplifying the assembly process of the protective layer 130 while increasing the number of samples for a single thermal annealing treatment. In other words, both opposite surfaces of the protective layer 130 have concave regions 131, which improves the utilization rate of the protective layer 130 and increases the number of layers of the aluminum nitride layer 112 for a single thermal annealing treatment.

[0075] In some embodiments, the distance d2 between the two points farthest apart within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 ranges from 0.1 μm to 50000 μm. Specifically, the value of the distance d2 between the two points farthest apart within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 may be, but is not limited to, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 17 μm, 18 μm, 20 μm, 22 μm, 24 μm, 27 μm, 28 μm, 31 μm, 33 μm, 35 μm, 37 μm, 42 μm, 45 μm, 48 μm, 50 μm, 65 μm, 80 μm, 140 μm, 170 μm, 230 μm, 450 μm, 500 μm, 780 μm, 1000 μm, 1200 μm, 1500 μm, 2500 μm, 3800 μm, 5800 μm, 8000 μm, 10000 μm, 15000 μm, 30000 μm, 40000 μm, 50000 μm, etc.

[0076] In the embodiments of the present application, when the distance d2 between the two points farthest apart within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 satisfies the range of 0.1 μm ≤ d2 ≤ 50000 μm, the distance between the two points farthest apart within the region enclosed by the orthographic projection of the convex structure 1311 is within a reasonable range, and the convex structures 1311 in the concave region 131 have a reasonable density, which is conducive to the contact between the protective layer 130 and the aluminum nitride layer 112, improving the surface uniformity of the aluminum nitride thin film 100; at the same time, the processing difficulty of the convex structure 1311 is reduced. When the value of the distance d2 between the two points farthest apart within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 is less than 0.1 μm, the distance between the two points farthest apart within the region enclosed by the orthographic projection of the convex structure 1311 is too small, increasing the processing difficulty of the convex structure 1311 and making it difficult to meet the height requirements of the convex structure 1311, thereby affecting the surface uniformity of the aluminum nitride thin film 100. When the value of the distance d2 between the two points farthest apart within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 is greater than 50000 μm, the convex structure 1311 can hardly provide a supporting effect for the concave region 131 of the protective layer 130.

[0077] Preferably, the distance d2 between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 ranges from 0.1 μm to 500 μm. Specifically, the value of the distance d2 between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 can be, but is not limited to, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 17 μm, 18 μm, 20 μm, 22 μm, 24 μm, 27 μm, 28 μm, 31 μm, 33 μm, 35 μm, 37 μm, 42 μm, 45 μm, 48 μm, 50 μm, 65 μm, 80 μm, 140 μm, 170 μm, 230 μm, 450 μm, 500 μm, etc. When the distance d2 between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 satisfies the range of 0.1 μm ≤ d2 ≤ 500 μm, the distance between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 is within a more reasonable range, and the convex structures 1311 in the concave region 131 have a more reasonable density, which is conducive to the contact between the protective layer 130 and the aluminum nitride layer 112, further improving the surface uniformity of the aluminum nitride thin film 100; at the same time, the processing difficulty of the convex structure 1311 is further reduced.

[0078] More preferably, the distance d2 between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 ranges from 0.1 μm to 65 μm. Specifically, the value of the distance d2 between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 can be, but is not limited to, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 17 μm, 18 μm, 20 μm, 22 μm, 24 μm, 27 μm, 28 μm, 31 μm, 33 μm, 35 μm, 37 μm, 42 μm, 45 μm, 48 μm, 50 μm, 55 μm, 60 μm, 65 μm, etc. When the distance d2 between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 satisfies the range of 0.1 μm ≤ d2 ≤ 65 μm, the distance between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 is within a more reasonable range, and the convex structures 1311 in the concave region 131 have a more reasonable density, which is conducive to the contact between the protective layer 130 and the aluminum nitride layer 112, greatly improving the surface uniformity of the aluminum nitride thin film 100; at the same time, the processing difficulty of the convex structure 1311 is greatly reduced.

[0079] In some preferred embodiments, the value of the distance d2 between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 is 27 μm. The distance between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 is within a reasonable range, and the convex structures 1311 in the recessed area 131 have a reasonable density, which is conducive to the contact between the protective layer 130 and the aluminum nitride layer 112, improving the surface uniformity of the aluminum nitride thin film 100; at the same time, the processing difficulty of the convex structure 1311 is reduced.

[0080] Optionally, in some embodiments, the convex structure 1311 is a cone, then the distance d2 between the two farthest points within the region enclosed by the orthographic projection of the convex structure 1311 on the surface of the aluminum nitride facing the protective layer 130 is the diameter of the bottom surface of the cone, and the diameter d2 of the bottom surface of the convex structure satisfies the range 0.1 μm ≤ d2 ≤ 50000 μm.

[0081] Optionally, the range of the minimum distance d3 between any two adjacent convex structures 1311 is: 0 μm ≤ d3 ≤ 50000 μm. Specifically, the value of the minimum distance d3 between any two adjacent convex structures 1311 can be, but is not limited to, 0 μm, 1 μm, 1.3 μm, 2.5 μm, 3.8 μm, 4 μm, 5.8 μm, 6 μm, 6.3 μm, 6.8 μm, 7.2 μm, 7.8 μm, 8.5 μm, 9.5 μm, 12.5 μm, 13 μm, 13.8 μm, 15 μm, 25 μm, 38 μm, 40 μm, 58 μm, 60 μm, 63 μm, 68 μm, 72 μm, 78 μm, 85 μm, 95 μm, 100 μm, 1000 μm, 10000 μm, 20000 μm, 30000 μm, 40000 μm, 50000 μm, etc.

[0082] In an embodiment of the present application, when the value of the minimum distance d3 between any two adjacent convex structures 1311 satisfies the range of 0 μm ≤ d3 ≤ 50000 μm, the minimum distance between any two adjacent convex structures 1311 is within a reasonable range, and the arrangement density of the convex structures 1311 in the concave region 131 is moderate, which is beneficial to the contact between the concave region 131 and the aluminum nitride layer 112 and plays a supporting role. In addition, when the minimum distance between any two adjacent convex structures 1311 is within a reasonable range, the aluminum nitride layer 112 and the protective layer 130 can be in contact with each other and have a small adhesive force. When the thermal annealing process ends, the probability of adhesion between the aluminum nitride layer 112 and the protective layer 130 is reduced, and the surface of the aluminum nitride thin film 100 has high surface uniformity, which is beneficial to the further preparation of high-performance devices 300. When the value of the minimum distance d3 between any two adjacent convex structures 1311 is 0, the arrangement of the convex structures 1311 in the concave region 131 is too dense, increasing the probability of adhesion between the aluminum nitride layer 112 and the protective layer 130; when the value of the minimum distance d3 between any two adjacent convex structures 1311 is greater than 50000 μm, the arrangement of the convex structures 1311 in the concave region 131 is too sparse, and the supporting effect on the concave region 131 of the protective layer 130 and the aluminum nitride layer 112 is limited.

[0083] Preferably, the range of the minimum distance d3 between any two adjacent convex structures 1311 is: 0 μm ≤ d3 ≤ 100 μm. Specifically, the value of the minimum distance d3 between any two adjacent convex structures 1311 can be, but is not limited to, 0 μm, 1 μm, 1.3 μm, 2.5 μm, 3.8 μm, 4 μm, 5.8 μm, 6 μm, 6.3 μm, 6.8 μm, 7.2 μm, 7.8 μm, 8.5 μm, 9.5 μm, 12.5 μm, 13 μm, 13.8 μm, 15 μm, 25 μm, 38 μm, 40 μm, 58 μm, 60 μm, 63 μm, 68 μm, 72 μm, 78 μm, 85 μm, 95 μm, and 100 μm, etc. When the minimum distance d3 between any two adjacent convex structures 1311 satisfies the range of 0 μm ≤ d3 ≤ 100 μm, it is beneficial to further improve the surface uniformity of the aluminum nitride thin film 100 and further prepare high-performance devices 300.

[0084] More preferably, the range of the minimum distance d3 between any two adjacent convex structures 1311 is: 0 μm ≤ d3 ≤ 15 μm. Specifically, the value of the minimum distance d3 between any two adjacent convex structures 1311 can be, but is not limited to, 0 μm, 1 μm, 1.3 μm, 2.5 μm, 3.8 μm, 4 μm, 5.8 μm, 6 μm, 6.3 μm, 6.8 μm, 7.2 μm, 7.8 μm, 8.5 μm, 9.5 μm, 12.5 μm, 13 μm, 13.8 μm, 15 μm, etc. When the minimum distance d3 between any two adjacent convex structures 1311 satisfies the range 0 μm ≤ d3 ≤ 15 μm, it is beneficial to further improve the surface uniformity of the aluminum nitride thin film 100 and further fabricate high-performance devices 300.

[0085] In some preferred embodiments, the minimum distance between any two adjacent convex structures 1311 is 4 μm. The minimum distance between any two adjacent convex structures 1311 is within a reasonable range, the arrangement density of the convex structures 1311 in the concave region 131 is moderate, the aluminum nitride layer 112 and the protective layer 130 can effectively contact and the adhesive force between them is small, which is beneficial to improving the surface uniformity of the aluminum nitride surface. When the thermal annealing process ends, the probability of adhesion between the aluminum nitride layer 112 and the protective layer 130 decreases, and the surface of the aluminum nitride thin film 100 has high surface uniformity, which is beneficial to further fabricating high-performance devices 300.

[0086] In some embodiments, along the stacking direction of the substrate 111 and the aluminum nitride layer 112, the range of the maximum height d4 of the convex structure 1311 is: 0 μm < d4 ≤ 200 μm. Specifically, the value of the maximum height d4 of the convex structure 1311 can be, but is not limited to, 0.2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 17 μm, 21 μm, 22 μm, 24 μm, 26 μm, 27 μm, 28 μm, 30 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 58 μm, 75 μm, 89 μm, 100 μm, 110 μm, 135 μm, 155 μm, 165 μm, 178 μm, 186 μm, 190 μm, 195 μm, 200 μm, etc.

[0087] It can be understood that along the stacking direction of the substrate 111 and the aluminum nitride layer 112, it can be the thickness direction of the aluminum nitride thin film 100 to be processed.

[0088] Understandably, the maximum height of the convex structure 1311 can be the distance from the end of the convex structure 1311 farthest from the concave region 131 to the surface of the concave region 131 facing the aluminum nitride layer 112 along the stacking direction of the substrate 111 and the aluminum nitride layer 112.

[0089] In an embodiment of the present application, when the value of the maximum height d4 of the convex structure 1311 satisfies the range 0 μm < d4 ≤ 200 μm, the maximum height of the convex structure 1311 is within a reasonable range, and the aluminum nitride layer 112 can be tightly combined with the concave region 131 and the flat region 133, so that the concave region 131 is effectively separated from the external environment, which is beneficial to suppressing the decomposition of the aluminum nitride layer 112 during the thermal annealing process, improving the crystal quality of the aluminum nitride thin film 100, and effectively reducing the defect density of the aluminum nitride thin film 100 and improving the surface uniformity of the aluminum nitride thin film 100 through the thermal annealing treatment. When the value of the maximum height d4 of the convex structure 1311 is greater than 200 μm, the maximum height of the convex structure 1311 is too large, making it difficult for the aluminum nitride layer 112 to be in close contact with the flat region 133, making it impossible to effectively separate the concave region 131 from the external environment, which is not conducive to suppressing the decomposition of the aluminum nitride layer 112 during the thermal annealing process, reducing the crystal quality of the aluminum nitride thin film 100, and making it difficult to effectively reduce the defect density of the aluminum nitride thin film 100 through the thermal annealing treatment.

[0090] Preferably, the range of the maximum height d4 of the convex structure 1311 is: 0 μm < d4 ≤ 50 μm. Specifically, the value of the maximum height d4 of the convex structure 1311 can be, but is not limited to, 0.2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 17 μm, 21 μm, 22 μm, 24 μm, 26 μm, 27 μm, 28 μm, 30 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, and 50 μm, etc.

[0091] In some preferred embodiments, the value of the maximum height d4 of the convex structure 1311 is 17 μm. The value of the maximum height of the convex structure 1311 is within a reasonable range, and the aluminum nitride layer 112 can be tightly combined with the concave region 131 and the flat region 133, so that the concave region 131 is effectively separated from the external environment, which is beneficial to suppressing the decomposition of the aluminum nitride layer 112 during the thermal annealing process, improving the crystal quality and surface uniformity of the aluminum nitride thin film 100, and effectively reducing the defect density of the aluminum nitride thin film 100.

[0092] Optionally, in some embodiments, the convex structure 1311 is a cone, and the maximum height of the convex structure 1311 is the height of the cone.

[0093] In some embodiments, the thermal annealing treatment of the aluminum nitride substrate 110 and the protective layer 130 includes: performing the thermal annealing treatment in an ammonia atmosphere.

[0094] The substrate 111, the aluminum nitride layer 112, and the protective layer 130 that are sequentially stacked are subjected to thermal annealing treatment at a high temperature. The aluminum nitride layer 112 will thermally decompose into -Al groups and -N groups at a high temperature. In the embodiments of the present application, the thermal annealing treatment process is carried out in an ammonia atmosphere. The aluminum nitride layer 112 can decompose into -N and -NH2 groups at a high temperature, so that there are saturated -N groups in the ambient atmosphere of the thermal annealing treatment. The saturated -N groups can effectively inhibit the decomposition of the aluminum nitride layer 112 at a high temperature, which is beneficial to improving the crystal quality of the aluminum nitride thin film 100. The defect density of the aluminum nitride thin film 100 is effectively reduced through the thermal annealing treatment to obtain an aluminum nitride thin film 100 with a low defect density.

[0095] In some embodiments, the thermal annealing treatment of the aluminum nitride substrate and the protective layer includes: the range of the temperature T2 is: 773.15K ≤ T2 ≤ 2273.15K; performing the thermal annealing treatment in an ammonia atmosphere. Specifically, the temperature for performing the thermal annealing treatment can be, but is not limited to, 773.15K, 823.15K, 873.15K, 923.15K, 973.15K, 1023.15K, 1073.15K, 1123.15K, 1273.15K, 1323.15K, 1473.15K, 1573.15K, 1623.15K, 1673.15K, 1723.15K, 1773.15K, 1823.15K, 1873.15K, 1923.15K, 1973.15K, 2023.15K, 2073.15K, 2123.15K, 2173.15K, 2223.15K, and 2273.15K, etc.

[0096] In the embodiments of the present application, when the value of the temperature T2 of the thermal annealing satisfies the range 773.15K ≤ T2 ≤ 2273.15K, the temperature of the thermal annealing is within a reasonable range, enabling the aluminum nitride thin film 100 to be fully recrystallized during the thermal annealing process, effectively reducing the defect density of the aluminum nitride thin film 100 during the thermal annealing treatment, and resulting in a relatively low defect density of the aluminum nitride thin film 100. When the value of the temperature T2 of the thermal annealing is less than 773.15K, the temperature of the thermal annealing is too low, making it difficult for the aluminum nitride thin film 100 to be fully recrystallized during the thermal annealing process and difficult to achieve the purpose of reducing the defect density of the aluminum nitride thin film 100, resulting in a relatively high defect density of the aluminum nitride thin film 100. When the value of the temperature T2 of the thermal annealing is greater than 2273.15K, the temperature of the thermal annealing is too high, and cracks are likely to appear on the surface of the aluminum nitride thin film 100, subsequently affecting the normal use of the aluminum nitride thin film 100 and being unfavorable for further fabricating high-performance devices 300.

[0097] Preferably, in some embodiments, the thermal annealing treatment is carried out at a temperature T2 of 2073.15K in an ammonia atmosphere. The relatively high temperature of the thermal annealing enables the aluminum nitride thin film 100 to be fully recrystallized during the thermal annealing process, effectively reducing the defect density of the aluminum nitride thin film 100 during the thermal annealing treatment, improving the crystal quality of the aluminum nitride thin film 100, and making it less likely for cracks to appear on the surface of the aluminum nitride thin film 100, resulting in the formed aluminum nitride thin film 100 having high crystal quality, low defect density, and high surface uniformity.

[0098] In some embodiments, the thermal annealing treatment includes: the range of the thermal annealing time t1 is 0min < t1 ≤ 180min; the thermal annealing treatment is carried out in an ammonia atmosphere. Specifically, the value of the thermal annealing time t1 can be, but is not limited to, 3min, 5min, 8min, 10min, 15min, 20min, 25min, 30min, 38min, 40min, 45min, 50min, 66min, 78min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, and 180min, etc.

[0099] In an embodiment of the present application, when the value of the thermal annealing time t1 satisfies the range 0 min < t1 ≤ 180 min, the thermal annealing time is within a reasonable range. The aluminum nitride thin film 100 can not only achieve sufficient recrystallization but also maintain the surface uniformity of the aluminum nitride thin film 100, and the purpose of reducing the defect density of the aluminum nitride thin film 100 is achieved through the thermal annealing treatment. When the value of the thermal annealing time t1 is greater than 180 min, the time for the thermal annealing treatment is too long, resulting in the surface of the aluminum nitride thin film 100 being too rough, which is not conducive to the further preparation of high-performance devices 300.

[0100] Preferably, in some embodiments, for the thermal annealing treatment, the thermal annealing time t1 is 90 min, and the thermal annealing treatment is carried out in an ammonia atmosphere. The thermal annealing time is within a reasonable range. The aluminum nitride thin film 100 can not only achieve sufficient recrystallization but also maintain the surface uniformity of the aluminum nitride thin film 100, and an aluminum nitride thin film 100 with a low defect density is obtained.

[0101] Please refer to Figure 9 , in some embodiments, the providing of the aluminum nitride substrate 110 includes:

[0102] S1011, providing a substrate 111.

[0103] Optionally, the material of the substrate 111 includes at least one of silicon, silicon carbide, alumina, etc. Preferably, the material of the substrate 111 is aluminum nitride.

[0104] Optionally, the thickness range of the substrate 111 is 200 μm ≤ h1 ≤ 1500 μm. The thickness of the substrate 111 is within a reasonable range, which is beneficial to obtaining a better-quality aluminum nitride layer 112 and is beneficial to saving production costs.

[0105] S1012, depositing an aluminum nitride layer 112 with a first temperature on the surface of the substrate 111 by chemical vapor deposition. The range of the temperature T1 is: 723.15 K ≤ T1 ≤ 1873.15 K; the range of the reaction pressure P1 is: 0 Torr < P1 ≤ 800 Torr. The range of the thickness d1 of the deposited aluminum nitride layer 112 is: 0 nm < d1 ≤ 1000 nm; wherein, the chemical vapor deposition method is metalorganic chemical vapor deposition.

[0106] In the embodiments of the present application, an aluminum nitride layer 112 with a first temperature is deposited on the surface of the substrate 111 by metal-organic chemical vapor deposition. The temperature range of T1 is: 723.15K ≤ T1 ≤ 1873.15K; the reaction pressure range of P1 is: 0 Torr < P1 ≤ 800 Torr. An aluminum nitride layer 112 is deposited on the surface of the substrate 111, so that the deposited aluminum nitride layer 112 has good quality and surface uniformity, which is beneficial to the further preparation of a high-performance aluminum nitride substrate 110. In addition, the deposition rate of the aluminum nitride layer 112 is relatively fast, and the deposition efficiency is relatively high, which is beneficial to improving the deposition efficiency of the aluminum nitride substrate 110. In the embodiments of the present application, the method for depositing the aluminum nitride layer 112 on the surface of the substrate 111 is metal-organic chemical vapor deposition. The method for depositing the aluminum nitride layer 112 has a relatively fast deposition rate, and the deposited aluminum nitride layer 112 has good uniformity and repeatability.

[0107] It can be understood that when the value of the temperature T1 satisfies the range of 723.15K ≤ T1 ≤ 1873.15K, the temperature for depositing the aluminum nitride layer 112 on the surface of the substrate 111 is within a reasonable range, so that the deposited aluminum nitride layer 112 has good quality and surface uniformity. When the value of the temperature T1 is less than 723.15K, the temperature for depositing the aluminum nitride layer 112 on the surface of the substrate 111 is too low, resulting in poor quality of the deposited aluminum nitride layer 112; when the value of the temperature T1 is greater than 1873.15K, the temperature for depositing the aluminum nitride layer 112 on the surface of the substrate 111 is too high, making it easy for cracks to occur on the surface of the deposited aluminum nitride layer 112, which is not conducive to the further preparation of a high-performance aluminum nitride substrate 110.

[0108] Specifically, the value of the temperature T1 can be, but is not limited to, 723.15K, 823.15K, 873.15K, 923.15K, 973.15K, 1023.15K, 1073.15K, 1123.15K, 1173.15K, 1223.15K, 1273.15K, 1323.15K, 1373.15K, 1423.15K, 1473.15K, 1523.15K, 1573.15K, 1623.15K, 1673.15K, 1723.15K, 1773.15K, 1823.15K, 1873.15K, etc. Preferably, the value of the temperature T1 is 1373.15K. The aluminum nitride layer 112 deposited at this temperature has good quality and surface uniformity.

[0109] Understandably, when the value of the reaction pressure P1 satisfies the range 0 Torr < P1 ≤ 800 Torr, the reaction pressure for depositing the aluminum nitride layer 112 on the surface of the substrate 111 is within a reasonable range, such that the aluminum nitride layer 112 has good quality and a high deposition rate. When the value of the reaction pressure P1 is greater than 800 Torr, the reaction pressure for depositing the aluminum nitride layer 112 on the surface of the substrate 111 is too high, causing the deposition rate of the aluminum nitride layer 112 on the surface of the substrate 111 to slow down, reducing the efficiency of depositing the aluminum nitride layer 112 on the surface of the substrate 111.

[0110] Specifically, the value of the reaction pressure P1 can be, but is not limited to, 0.001 Torr, 0.004 Torr, 0.01 Torr, 0.1 Torr, 1 Torr, 10 Torr, 20 Torr, 30 Torr, 40 Torr, 45 Torr, 50 Torr, 60 Torr, 70 Torr, 80 Torr, 90 Torr, 100 Torr, 150 Torr, 200 Torr, 230 Torr, 300 Torr, 350 Torr, 390 Torr, 420 Torr, 470 Torr, 550 Torr, 610 Torr, 650 Torr, 720 Torr, 750 Torr, and 800 Torr, etc. Preferably, the value of the reaction pressure P1 is 50 Torr. The aluminum nitride layer 112 deposited under this reaction pressure has good quality and a relatively fast deposition rate.

[0111] Optionally, in some embodiments, the thickness d1 of the aluminum nitride layer 112 deposited on the surface of the substrate 111 ranges from 0 nm < d1 ≤ 1000 nm. When the thickness d1 of the aluminum nitride layer 112 deposited on the surface of the substrate 111 satisfies the range 0 nm < d1 ≤ 1000 nm, the aluminum nitride layer 112 has good quality and surface uniformity. When the thickness of the aluminum nitride layer 112 is greater than 1000 nm, the aluminum nitride layer 112 is too thick, and the probability of cracks appearing on the surface of the aluminum nitride layer 112 due to stress increases, which is not conducive to further fabricating a high-performance aluminum nitride substrate 110.

[0112] Specifically, the value of the thickness d1 of the aluminum nitride layer 112 deposited on the surface of the substrate 111 can be, but is not limited to, 10 nm, 50 nm, 60 nm, 100 nm, 150 nm, 200 nm, 320 nm, 400 nm, 450 nm, 500 nm, 650 nm, 700 nm, 750 nm, 800 nm, 860 nm, 890 nm, 900 nm, 950 nm, 980 nm, 1000 nm, etc. Preferably, the value of the thickness d1 of the aluminum nitride layer 112 deposited on the surface of the substrate 111 is 600 nm. The thickness of the aluminum nitride layer 112 is appropriate, and the aluminum nitride layer 112 has good quality and surface uniformity.

[0113] Optionally, in some embodiments, before the thermal annealing treatment is performed, the root mean square roughness value of the surface of the aluminum nitride layer 112 facing away from the substrate 111 is greater than or equal to 3.3 nm. Specifically, the root mean square roughness value of the surface of the aluminum nitride layer 112 facing away from the substrate 111 can be, but is not limited to, 3.3 nm, 3.4 nm, 3.5 nm, 3.6 nm, 3.7 nm, 3.9 nm, 4.0 nm, 4.1 nm, 4.2 nm, 4.4 nm, 4.5 nm, 4.6 nm, 4.8 nm, 4.9 nm, 5.0 nm, 5.1 nm, etc.

[0114] It can be understood that the root mean square roughness of the surface of the aluminum nitride layer 112 facing away from the substrate 111 reflects the roughness of the surface of the aluminum nitride layer 112 facing away from the substrate 111. The larger the root mean square roughness of the surface of the aluminum nitride layer 112 facing away from the substrate 111, the rougher the surface of the aluminum nitride layer 112 facing away from the substrate 111, and the worse the surface uniformity of the aluminum nitride layer 112 facing away from the substrate 111; the smaller the root mean square roughness of the surface of the aluminum nitride layer 112, the smoother the surface of the aluminum nitride layer 112 facing away from the substrate 111, and the better the surface uniformity of the aluminum nitride layer 112 facing away from the substrate 111. In the embodiments of the present application, the surface roughness of the aluminum nitride layer 112 is relatively large, and the surface uniformity of the aluminum nitride layer 112 is not good enough.

[0115] In some embodiments, before the thermal annealing treatment is performed, the dislocation density of the aluminum nitride layer 112 deposited on the surface of the substrate 111 is greater than or equal to 5×10 10 cm -2 . Specifically, the dislocation density of the aluminum nitride layer 112 deposited on the substrate 111 can be, but is not limited to, 5×10 10 cm -2 , 5.02×10 10 cm -2 , 5.3×10 10 cm-2 , 6.5×10 10 cm -2 , 7.3×10 10 cm -2 , 7.8×10 10 cm -2 , 8.0×10 10 cm -2 , 9.1×10 10 cm -2 and 9.3×10 10 cm -2 etc.

[0116] It can be understood that the dislocation density refers to the number of distortions per unit area. Then, the larger the dislocation density, the poorer the crystal quality of the aluminum nitride layer 112; the smaller the dislocation density, the better the crystal quality of the aluminum nitride layer 112. In the embodiments of the present application, the aluminum nitride layer 112 deposited on the surface of the substrate 111 still has a relatively large dislocation density, the defect density of the aluminum nitride layer 112 is large, and the crystal quality is poor.

[0117] In some embodiments, before the thermal annealing treatment, the full width at half maximum value of the X-ray rocking curve of the aluminum nitride layer 112 along the

[0002] direction is greater than or equal to 0.46°. Specifically, the full width at half maximum value of the X-ray rocking curve of the aluminum nitride layer 112 along the

[0002] direction can be, but is not limited to, 0.46°, 0.47°, 0.48°, 0.50°, 0.52°, 0.54°, 0.56°, 0.58°, 0.6°, 0.62°, 0.70°, 0.85°, 0.95°, and 1.05°, etc.

[0118] It can be understood that the full width at half maximum values of the aluminum nitride layer 112 in different directions can be obtained through X-ray rocking curve testing to obtain the grain size of the grains in the aluminum nitride layer 112. When the full width at half maximum value of the aluminum nitride layer 112 is smaller, the grains in the aluminum nitride layer 112 are larger, and the crystal quality of the aluminum nitride layer 112 is better; when the full width at half maximum value of the aluminum nitride layer 112 is larger, the grains in the aluminum nitride layer 112 are smaller, and the crystal quality of the aluminum nitride layer 112 is poorer. In the embodiments of the present application, the full width at half maximum value of the X-ray rocking curve of the aluminum nitride layer 112 along the

[0002] direction is relatively large, then the grains of the aluminum nitride layer 112 are smaller, and the crystal quality of the aluminum nitride layer 112 is poorer.

[0119] In some embodiments, before the thermal annealing treatment, the full width at half maximum (FWHM) value of the X-ray rocking curve of the aluminum nitride layer 112 along the [10-12] direction is greater than or equal to 0.6°. Specifically, the FWHM value of the X-ray rocking curve of the aluminum nitride layer 112 along the [10-12] direction can be, but is not limited to, 0.6°, 0.65°, 0.67°, 0.68°, 0.69°, 0.70°, 0.71°, 0.72°, 0.73°, 0.74°, 1.00°, 1.25°, 1.50°, etc. In the embodiments of the present application, if the FWHM value of the X-ray rocking curve of the aluminum nitride layer 112 along the [10-12] direction is relatively large, the grains of the aluminum nitride layer 112 are smaller and the crystal quality of the aluminum nitride layer 112 is poorer.

[0120] Optionally, in some embodiments, the aluminum nitride thin film 100 after the thermal annealing treatment satisfies at least one of the following conditions: the root mean square roughness of the surface of the aluminum nitride thin film 100 facing away from the substrate 111 is less than 3.3 nm; the dislocation density of the aluminum nitride thin film 100 is less than 5×10 10 cm -2 ; and the FWHM value of the X-ray rocking curve of the aluminum nitride thin film 100 along the

[0002] direction is less than 0.3°; the FWHM value of the X-ray rocking curve of the aluminum nitride thin film 100 along the [10-12] direction is less than 0.6°. It can be understood that the aluminum nitride thin film 100 satisfies one or more of the above conditions. When the aluminum nitride thin film 100 satisfies one or more of the above conditions, the aluminum nitride thin film 100 has good crystal quality, which is beneficial to further fabricating higher-performance devices 300.

[0121] In some embodiments, the root mean square roughness of the surface of the aluminum nitride thin film 100 facing away from the substrate 111 is less than 3.3 nm. Specifically, the value of the root mean square roughness of the surface of the aluminum nitride thin film 100 facing away from the substrate 111 can be, but is not limited to, 0.6 nm, 0.8 nm, 0.9 nm, 1.0 nm, 1.2 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2 nm, 2.2 nm, 2.5 nm, 2.6 nm, 2.8 nm, 3.0 nm, 3.1 nm, and 3.2 nm, etc.

[0122] In the embodiments of the present application, the root mean square roughness value of the surface of the aluminum nitride thin film 100 facing away from the substrate 111 is less than 3.3 nm, while the root mean square roughness value of the surface of the aluminum nitride layer 112 before thermal annealing treatment is greater than or equal to 3.3 nm. Compared with the root mean square roughness of the surface of the aluminum nitride layer 112 before thermal annealing treatment, in the embodiments of the present application, when the aluminum nitride thin film 100 is subjected to thermal annealing treatment, it is disposed opposite to the protective layer 130 having the concave region 131 and the flat region 133. The concave region 131 reduces the contact area with the aluminum nitride layer 112, so that after the thermal annealing treatment is completed, there will be no excessive adhesion between the protective layer 130 and the aluminum nitride layer 112 and it is easy to peel off. Finally, the surface of the aluminum nitride thin film 100 facing away from the substrate 111 is relatively smooth and has good surface uniformity.

[0123] In some embodiments, the dislocation density of the aluminum nitride thin film 100 is less than 5×10 10 cm -2 . Specifically, the dislocation density of the aluminum nitride thin film 100 can be, but is not limited to, 4.9×10 10 cm -2 , 4.75×10 10 cm -2 , 4.3×10 10 cm -2 , 3.9×10 10 cm -2 , 3.75×10 10 cm -2 , 3.5×10 10 cm -2 , 3.0×10 10 cm -2 , 2.85×10 10 cm -2 , 2.6×10 10 cm -2 , 2.3×10 10 cm -2 , 2.0×10 10 cm -2 , 1.95×10 10 cm -2 , 1.6×10 10 cm -2 , 1.35×10 10 cm -2 , and 1.0×10 10 cm -2 etc.

[0124] In the embodiments of the present application, the dislocation density of the aluminum nitride thin film 100 is less than 5×10 10 cm -2, and the dislocation density of the aluminum nitride layer 112 before thermal annealing treatment is greater than or equal to 5×10 10 cm -2 , compared with the aluminum nitride layer 112 before thermal annealing treatment, the temperature T1 and thermal annealing time t1, etc. of the aluminum nitride thin film 100 in the embodiments of the present application during thermal annealing treatment are within a reasonable range, so that the aluminum nitride layer 112 can be fully recrystallized during thermal annealing, and the defect density of the aluminum nitride layer 112 can be effectively reduced during thermal annealing treatment, and finally an aluminum nitride thin film 100 with low defect density and high crystal quality is obtained.

[0125] In some embodiments, the full width at half maximum value of the X-ray rocking curve of the aluminum nitride thin film 100 along the

[0002] direction is less than 0.3°. Specifically, the full width at half maximum value of the X-ray rocking curve of the aluminum nitride thin film 100 along the

[0002] direction can be, but is not limited to, 0.05°, 0.07°, 0.09°, 0.10°, 0.11°, 0.12°, 0.13°, 0.14°, 0.15°, 0.16°, 0.17°, 0.18°, 0.20°, 0.22°, 0.23°, 0.24°, 0.25°, 0.28°, and 0.29°, etc.

[0126] In the embodiments of the present application, the full width at half maximum value of the X-ray rocking curve of the aluminum nitride thin film 100 along the

[0002] direction is less than 0.3°, while the full width at half maximum value of the X-ray rocking curve of the aluminum nitride layer 112 before thermal annealing treatment along the

[0002] direction is greater than or equal to 0.3°. The full width at half maximum value of the X-ray rocking curve of the aluminum nitride thin film 100 in the embodiments of the present application along the

[0002] direction is smaller, then the grains of the aluminum nitride thin film 100 are larger, and the aluminum nitride thin film 100 after thermal annealing treatment has better crystal quality.

[0127] In some embodiments, the full width at half maximum value of the X-ray rocking curve of the aluminum nitride thin film 100 along the [10-12] direction is less than 0.6°. Specifically, the full width at half maximum value of the X-ray rocking curve of the aluminum nitride thin film 100 along the [10-12] direction can be, but is not limited to, 0.05°, 0.07°, 0.09°, 0.10°, 0.11°, 0.12°, 0.13°, 0.14°, 0.15°, 0.16°, 0.17°, 0.19°, 0.2°, 0.24°, 0.29°, 0.34°, 0.38°, 0.42°, 0.46°, 0.54°, 0.57°, and 0.59°, etc.

[0128] The full width at half maximum (FWHM) value of the X-ray rocking curve of the aluminum nitride thin film 100 in the [10-12] direction in the embodiment of the present application is less than 0.6°, while the FWHM value of the X-ray rocking curve of the aluminum nitride layer 112 in the [10-12] direction before thermal annealing treatment is greater than or equal to 0.6°. Since the FWHM value of the X-ray rocking curve of the aluminum nitride thin film 100 in the [10-12] direction in the embodiment of the present application is smaller, the grains of the aluminum nitride thin film 100 after thermal annealing treatment are larger, and the aluminum nitride thin film 100 after thermal annealing has better crystal quality.

[0129] Please refer to Figure 10 and Figure 11 , the present application also provides a device 300 based on an aluminum nitride thin film. The device 300 is fabricated on the aluminum nitride thin film 100 after thermal annealing treatment. The device 300 includes: an aluminum nitride thin film 100 prepared by the preparation method of the aluminum nitride thin film 100 provided by the present application and a functional layer 310. The functional layer 310 is disposed on the surface of the aluminum nitride thin film 100 facing away from the substrate 111.

[0130] In the embodiment of the present application, the functional layer 310 is disposed on the surface of the aluminum nitride thin film 100 facing away from the substrate 111. The aluminum nitride thin film 100 prepared by the preparation method provided by the present application has better crystal quality, lower defect density and better surface uniformity, so that the device 300 fabricated on the surface of the aluminum nitride thin film 100 has better performance.

[0131] Optionally, the device 300 can be, but is not limited to, at least one of an ultraviolet light-emitting diode, a power device, a radio frequency power device, an optical waveguide device, an ultraviolet laser, a photodetector, etc.

[0132] Optionally, please refer to Figure 12 , in some embodiments, the device 300 is an ultraviolet light-emitting diode 200, and the functional layer 310 of the device 300 is a light-emitting layer 210. The ultraviolet light-emitting diode 200 includes an aluminum nitride thin film 100 prepared by the preparation method provided by the present application and a light-emitting layer 210. The light-emitting layer 210 is disposed on the surface of the aluminum nitride thin film 100 facing away from the substrate 111 and is used to generate ultraviolet light. The aluminum nitride thin film 100 prepared by the preparation method provided by the present application has high crystal quality, low defect density and high surface uniformity. When the light-emitting layer 210 is disposed on the surface of the aluminum nitride thin film 100, the aluminum nitride thin film 100 with high crystal quality can enable the light-emitting layer 210 to obtain higher output power and higher photoelectric conversion efficiency under the same current.

[0133] Specifically, if the light-emitting layer 210 is directly disposed on the surface of the aluminum nitride layer 112 having the first temperature, when the ultraviolet light-emitting diode 200 emits ultraviolet light with a wavelength of 270 nm at a current of 20 mA, its output power is only 0.1 mW and the internal quantum efficiency is only 14%. When the light-emitting layer 210 is disposed on the surface of the aluminum nitride thin film 100 having the second temperature, when the ultraviolet light-emitting diode 200 emits ultraviolet light with a wavelength of 270 nm at a current of 20 mA, its output power can reach 0.8 mW and the internal quantum efficiency is higher than 14%. The aluminum nitride thin film 100 provides a substrate with better performance for the ultraviolet light-emitting diode 200, so that the ultraviolet light-emitting diode 200 has better performance.

[0134] Optionally, in some embodiments, the light-emitting layer 210 includes a plurality of light-emitting units 211, and the plurality of light-emitting units 211 are arranged in an array. The arrangement of the plurality of light-emitting units 211 in an array increases the utilization rate of the unit area of the light-emitting layer 210 and improves the product yield.

[0135] Optionally, in some embodiments, the ultraviolet light-emitting diode 200 includes a driving substrate 220, a driving circuit is disposed on the driving substrate 220, and the driving substrate 220 is electrically connected to the light-emitting layer 210 for driving the light-emitting layer 210 to emit light. Specifically, each of the light-emitting units 211 electrically connected to the driving substrate 220 is used to drive each of the light-emitting units 211 to emit light. In some embodiments, the driving substrate 220 may be a thin film transistor (TFT) substrate. In the embodiments of the present application, the light-emitting layer 210 is disposed on the driving substrate 220, and the aluminum nitride thin film is disposed on the surface of the light-emitting layer 210 facing away from the driving substrate 220. In other words, the driving substrate 220, the light-emitting layer 210, and the aluminum nitride thin film are sequentially stacked. The driving substrate 220 drives the light-emitting layer 210 to emit light, and the aluminum nitride thin film 100 is beneficial to improving the output power of the light emitted by the light-emitting layer 210 and the photoelectric conversion efficiency under the same current.

[0136] Optionally, in some embodiments, the device 300 is a power device. The power device includes an aluminum nitride thin film 100, a buffer layer, a channel layer, and a first barrier layer that are sequentially stacked. The functional layer 310 of the device 300 includes the buffer layer, the channel layer, and the first barrier layer. The buffer layer is used to form a two-dimensional electron gas. The channel layer is used to provide a place for the movement of the two-dimensional electron gas. The first barrier layer is used to provide a high enough barrier height to prevent carriers from crossing over. The functional layer 310 of the power device is disposed on the surface of the aluminum nitride thin film 100. The aluminum nitride thin film 100 has a low defect density and good performance, providing a substrate with good performance for the functional layer 310, so that the power device has good performance.

[0137] Optionally, in some embodiments, the device 300 is a photodetector. The photodetector includes an aluminum nitride thin film 100, a contact layer, a second barrier layer, and an absorption layer that are sequentially stacked. The functional layer 310 of the device 300 includes the contact layer, the second barrier layer, and the absorption layer. Among them, the absorption layer is used to absorb photo-generated carriers generated under light illumination conditions. The second barrier layer is used to prevent the movement of carriers under non-light illumination conditions. The contact layer is used to amplify the electrical signal formed by the obtained photo-generated carriers. The functional layer 310 of the photodetector is disposed on the surface of the aluminum nitride thin film 100. The aluminum nitride thin film 100 has a low defect density and good performance, providing a substrate with good performance for the functional layer 310, so that the photodetector has good performance.

[0138] Optionally, in some embodiments, the device 300 is an optical waveguide device. The optical waveguide device includes an aluminum nitride thin film 100, a first cladding layer, a waveguide layer, and a second cladding layer that are sequentially stacked. The functional layer 310 of the device 300 includes the first cladding layer, the waveguide layer, and the second cladding layer. The waveguide layer is used to propagate optical signals. The first cladding layer and the second cladding layer are used to confine the optical signals within the waveguide layer. The functional layer 310 of the optical waveguide device is disposed on the surface of the aluminum nitride thin film 100. The aluminum nitride thin film 100 has a low defect density and good performance, providing a substrate with good performance for the functional layer 310, so that the optical waveguide device has good performance.

[0139] Optionally, in some embodiments, the device 300 is an ultraviolet laser, and the ultraviolet laser includes an aluminum nitride thin film 100, an N-type cladding layer, an active region, and a P-type cladding layer that are sequentially stacked. The functional layer 310 of the device 300 includes the N-type cladding layer, the active region, and the P-type cladding layer. The N-type cladding layer is used to generate and conduct electrons, the P-type cladding layer is used to generate holes, and the cladding layer is used to conduct and amplify the generated laser. The functional layer 310 of the ultraviolet laser is disposed on the surface of the aluminum nitride thin film 100. The aluminum nitride thin film 100 has a low defect density and good performance, providing a substrate with good performance for the functional layer 310, so that the ultraviolet laser has good performance.

[0140] In this application, the mention of "embodiment" or "embodiment manner" means that the specific features, structures, or characteristics described in connection with the embodiment may be included in at least one embodiment of this application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described in this application can be combined with other embodiments. In addition, it should also be understood that the features, structures, or characteristics described in each embodiment of this application can be combined arbitrarily without conflict with each other to form another embodiment that does not depart from the spirit and scope of the technical solution of this application.

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although the technical solutions of this application have been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that modifications or equivalent replacements can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A method for preparing an aluminum nitride thin film, characterized in that, The preparation method includes: Providing an aluminum nitride substrate, the aluminum nitride substrate including a substrate and an aluminum nitride layer having a first temperature T1 arranged in a stacked manner; Providing a protective layer on a surface of the aluminum nitride layer facing away from the substrate, the protective layer including a recessed area and a flat area arranged around an outer periphery of the recessed area, a root mean square roughness RMS of a surface of the flat area facing the aluminum nitride layer being in a range of: 0 nm < RMS ≤ 50 nm; and Performing a thermal annealing treatment on the aluminum nitride substrate and the protective layer to obtain the aluminum nitride thin film having a second temperature T2; wherein, the second temperature is greater than the first temperature; the first temperature T1 is in a range of: 723.15 K ≤ T1 ≤ 1873.15 K; the second temperature T2 is in a range of: 773.15 K ≤ T2 ≤ 2273.15 K.

2. The preparation method of the aluminum nitride thin film according to claim 1, wherein The providing of the aluminum nitride substrate includes: Providing a substrate; Depositing an aluminum nitride layer having a first temperature on a surface of the substrate by a physical or chemical method, the deposition method including at least one of sputtering, atomic layer deposition, molecular beam epitaxy, chemical vapor deposition, and pulsed laser deposition.

3. The method for preparing an aluminum nitride thin film according to claim 2, wherein, The providing of the aluminum nitride substrate includes: Providing a substrate; Depositing an aluminum nitride layer having a first temperature on a surface of the substrate by a chemical vapor deposition method, at a reaction pressure P1 in a range of: 0 Torr < P1 ≤ 800 Torr, a thickness d1 of the deposited aluminum nitride layer being in a range of: 0 nm < d1 ≤ 1000 nm; wherein, the chemical vapor deposition method is a metalorganic chemical vapor deposition method.

4. The method for preparing an aluminum nitride thin film according to claim 1, wherein The protective layer further includes one or more convex structures, one convex structure being arranged on a surface of the recessed area facing the aluminum nitride layer, a plurality of the convex structures being arranged at intervals on the surface of the recessed area facing the aluminum nitride layer, the convex structure having an end face facing the aluminum nitride layer, the flat area having a preset surface facing the aluminum nitride layer, and the end face not being higher than the preset surface.

5. The preparation method of the aluminum nitride thin film according to claim 4, characterized in that, A distance d2 between two points farthest apart from each other on an area surrounded by a positive projection of the convex structure on a surface of the aluminum nitride facing the protective layer is in a range of: 0.1 μm ≤ d2 ≤ 50000 μm; A minimum distance d3 between any two adjacent convex structures is in a range of: 0 μm ≤ d3 ≤ 50000 μm.

6. The method for preparing an aluminum nitride thin film according to claim 4, wherein In a stacking direction of the substrate and the aluminum nitride layer, a maximum height d4 of the convex structure is in a range of: 0 μm < d4 ≤ 200 μm.

7. The method for preparing an aluminum nitride thin film according to claim 1, wherein The performing of the thermal annealing treatment on the aluminum nitride substrate and the protective layer includes: performing the thermal annealing treatment in an ammonia atmosphere.

8. The method for preparing an aluminum nitride thin film according to claim 7, wherein The performing of the thermal annealing treatment on the aluminum nitride substrate and the protective layer includes: performing the thermal annealing treatment in an ammonia atmosphere; wherein, a thermal annealing time t1 is in a range of: 0 min < t1 ≤ 180 min.

9. The method for preparing an aluminum nitride thin film according to claim 1, wherein, The aluminum nitride thin film after thermal annealing treatment satisfies at least one of the following conditions: the root mean square roughness of the surface of the aluminum nitride thin film facing away from the substrate is less than 3.3 nm, the dislocation density of the aluminum nitride thin film is less than 5×10 10 cm -2 , the full width at half maximum value of the X-ray rocking curve of the aluminum nitride thin film along the [0002] direction is less than 0.3°, and the full width at half maximum value of the X-ray rocking curve of the aluminum nitride thin film along the [10-12] direction is less than 0.6°.

10. A device based on aluminum nitride thin film, characterized in that, The device is prepared on the aluminum nitride thin film after the thermal annealing treatment, the device including: The aluminum nitride thin film prepared by the preparation method according to any one of claims 1 to 9; and A functional layer, the functional layer being arranged on a surface of the aluminum nitride thin film facing away from the substrate.

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