AlN Thin Film with Anti-Cracking Function and Its Epitaxial Growth Method

Abstract

The present invention discloses an AlN thin film with an anti-cracking function and an epitaxial growth method thereof. The epitaxial growth method specifically includes the following steps: growing an AlN buffer layer, a first AlN layer, an AlInN layer, and a second AlN layer on a sapphire substrate in sequence; performing an annealing treatment in a pure hydrogen atmosphere until In in the AlInN layer is completely separated, and forming an AlN void layer with a pore structure; continuously growing a third AlN layer on the second AlN layer to obtain an AlN thin film with an anti-cracking function. In the process of depositing the AlN film layer in the present invention, by introducing the AlInN layer and performing an annealing treatment, an AlN void layer with a pore structure is formed, and the thermal stress in the subsequent AlN growth can be fully released by using the pore structure, which can well prevent the AlN film layer from cracking and improve the growth quality of the AlN film layer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and particularly to an AlN thin film with a crack prevention function and an epitaxial growth method thereof. Background Art

[0002] At present, the luminous efficiency of deep ultraviolet LEDs generally does not exceed 5%, which is caused by two factors: low internal quantum efficiency and low light extraction efficiency. The low light extraction efficiency is caused by the essential characteristic that the light emission of high-Al-component AlGaN materials is mainly emitted from the side, while the low internal quantum efficiency is because the crystal quality of high-Al-component AlGaN materials has not yet reached an ideal level, and their dislocation density is mostly in the order of 109 cm -2 Due to the lack of homo-substrates, group-III nitride materials are usually hetero-epitaxially grown on sapphire substrates. In order to reduce the dislocation density of AlGaN materials and improve their crystal quality, a binary AlN material needs to be grown on sapphire first before growing AlGaN materials. On the one hand, there is no compositional segregation problem in binary AlN materials, and the crystal quality of AlN materials grown at high temperatures is better; on the other hand, the lattice constant of AlGaN materials is larger than that of AlN materials, and AlGaN materials will be subjected to compressive stress from AlN materials, which can prevent the AlGaN materials from cracking due to excessive epitaxial thickness. Therefore, improving the crystal quality of the AlN epitaxial layer is a prerequisite for improving the luminous efficiency of deep ultraviolet LEDs. For the epitaxial growth of high-quality AlN materials, due to the lack of homo-substrates, AlN materials are usually grown on sapphire substrates, and a large number of misfit dislocations will penetrate upward to form threading dislocations. At the same time, the thermal stress accumulated during the growth process will cause the AlN epitaxial film to crack. How to filter dislocations and release thermal stress is the key to improving the crystal quality of AlN materials and preventing the epitaxial film from cracking. Therefore, a new epitaxial growth method needs to be proposed to solve the above existing problems. Summary of the Invention

[0003] The purpose of the present invention is to provide an AlN thin film with a crack prevention function and an epitaxial growth method thereof, which are used to solve the problem that the AlN epitaxial film is prone to cracking due to the accumulation of thermal stress during the existing AlN epitaxial growth process.

[0004] To solve the above technical problems, the first solution provided by the present invention is: an epitaxial growth method of an AlN thin film with anti-cracking function, specifically including the following steps: S1, growing an AlN buffer layer, a first AlN layer, an AlInN layer, and a second AlN layer on a sapphire substrate in sequence; S2, performing annealing treatment in a pure hydrogen atmosphere until In in the AlInN layer is completely separated, and forming an AlN void layer with a pore structure; S3, continuously growing a third AlN layer on the second AlN layer to obtain an AlN thin film with anti-cracking function; the annealing treatment temperature in step S2 is less than the growth temperature of the second AlN layer in step S1, and the annealing treatment temperature in step S2 is less than the growth temperature of the third AlN layer in step S3.

[0005] Among them, the specific process steps of the AlN buffer layer in step S1 are: depositing AlN in a pure hydrogen atmosphere at 800 °C to 1100 °C; maintaining the pure hydrogen atmosphere, heating up to 1100 °C to 1300 °C, performing high-temperature annealing, and the annealing time is 5 to 15 minutes; after the annealing is completed, maintaining the temperature, introducing ammonia gas, and performing high-temperature nitridation, and the nitridation time is 5 to 15 minutes to obtain the AlN buffer layer.

[0006] Preferably, in step S1, the growth temperature of the first AlN layer is 1200 to 1400 °C, and the thickness is 0.1 nm to 500 nm.

[0007] Preferably, in step S1, the growth temperature of the AlInN layer is 700 to 1000 °C.

[0008] Among them, when the size of the sapphire substrate is 2 inches, the thickness of the sapphire substrate is 350 μm to 700 μm, and the thickness of the AlInN layer is 1 nm to 500 nm.

[0009] Among them, when the size of the sapphire substrate is 4 inches, the thickness of the sapphire substrate is 700 μm to 1000 μm, and the thickness of the AlInN layer is 600 nm to 1500 nm.

[0010] Preferably, in step S1, the growth temperature of the second AlN layer is 1100 to 1300 °C, and the thickness is 1 nm to 500 nm.

[0011] Among them, the specific process steps of the annealing treatment in step S2 are: after the growth of the second AlN layer is completed, cooling down to 1000 °C to 1200 °C, performing annealing in a pure hydrogen atmosphere, and the annealing time is 5 to 60 minutes, and an AlN void layer with a pore structure is formed after annealing; after the annealing treatment, there is no pore-like structure in the first AlN layer and the second AlN layer.

[0012] Preferably, in step S3, the growth temperature of the third AlN layer is 1200-1400 °C, and the thickness is 100 nm-5000 nm.

[0013] To solve the above technical problems, the second solution provided by the present invention is: an AlN thin film with an anti-cracking function, and the AlN thin film with an anti-cracking function is prepared by the epitaxial growth method in the foregoing first solution.

[0014] The beneficial effects of the present invention are: different from the prior art, the present invention provides an AlN thin film with an anti-cracking function and an epitaxial growth method thereof. During the deposition of the AlN film layer, by introducing an AlInN layer and annealing treatment, an AlN void layer with a pore structure is formed. The pore structure enables the thermal stress to be fully released during the subsequent growth of AlN, which can well prevent the AlN film layer from cracking and improve the growth quality of the AlN film layer. Description of the Drawings

[0015] Figure 1 is a process flow chart of an embodiment of the epitaxial growth method of the AlN thin film with an anti-cracking function in the present invention;

[0016] Figure 2 is a cross-sectional TEM image of the AlN thin film with an anti-cracking function in Example 1 of the present invention. Detailed Embodiments

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0018] For the first solution provided by the present invention, please refer to Figure 1 , the epitaxial growth method of the AlN thin film with an anti-cracking function specifically includes the following steps:

[0019] S1. Grow an AlN buffer layer, a first AlN layer, an AlInN layer, and a second AlN layer on a sapphire substrate in sequence. In this step, first, the specific process steps of the AlN buffer layer are as follows: Deposit AlN on the sapphire substrate in a pure hydrogen atmosphere at 800°C to 1100°C; maintain the pure hydrogen atmosphere, heat up to 1100°C to 1300°C, and perform high-temperature annealing for 5 to 15 minutes; after the annealing is completed, maintain the temperature and introduce ammonia gas to perform high-temperature nitridation for 5 to 15 minutes to obtain the AlN buffer layer. Here, the AlN buffer layer plays a transitional role. Through high-temperature annealing and nitridation treatment, the AlN buffer layer recrystallizes, so that the subsequent deposited film layers can obtain a better crystal orientation.

[0020] Then, deposit the first AlN layer on the AlN buffer layer. The growth temperature of the first AlN layer is 1200 to 1400°C, and the thickness is 0.1 nm to 500 nm; deposit the AlInN layer on the first AlN layer. The growth temperature of the AlInN layer is 700 to 1000°C; deposit the second AlN layer on the AlInN layer. The growth temperature of the second AlN layer is 1100 to 1300°C, and the thickness is 1 nm to 500 nm.

[0021] Among them, for sapphire substrates of different size specifications, the thickness of the sapphire substrate and the thickness of the AlInN layer will be different. Specifically, when the size of the sapphire substrate is 2 inches, the thickness of the sapphire substrate is 350 μm to 700 μm, and the thickness of the AlInN layer is 1 nm to 500 nm; when the size of the sapphire substrate is 4 inches, the thickness of the sapphire substrate is 700 μm to 1000 μm, and the thickness of the AlInN layer is 600 nm to 1500 nm. The reason for such a setting is that when the size specification of the sapphire substrate is larger, the growth of the AlN thin film is more likely to accumulate thermal stress, and thus more likely to crack; here, for a larger-sized sapphire substrate, a thicker AlInN layer is designed. When the AlInN layer undergoes subsequent annealing treatment, the detachment of In can form more pore structures, which is more conducive to releasing thermal stress.

[0022] S2. Anneal in a pure hydrogen atmosphere until all In in the AlInN layer is separated, and form an AlN void layer with a pore structure. The specific process steps of the annealing treatment in this step are as follows: after the growth of the second AlN layer is completed, cool down to 1000 °C - 1200 °C, and anneal in a pure hydrogen atmosphere for 5 - 60 minutes. After annealing, an AlN void layer with a pore structure is formed. After the annealing treatment, there is no pore-like structure in the first AlN layer and the second AlN layer, and only the pore-like structure exists in the AlN void layer. The thermal stress generated during the subsequent growth of the AlN film layer will be released through the pore structure here, thus avoiding the accumulation of thermal stress during the film layer growth process and greatly avoiding the occurrence of cracking. At the same time, due to the good release of thermal stress, the subsequent film layer deposition is more uniform, and the crystal quality of the AlN material is significantly improved.

[0023] S3. Continue to grow the third AlN layer on the second AlN layer to obtain an AlN thin film with anti-cracking function. In this step, the growth temperature of the third AlN layer is 1200 - 1400 °C, and the thickness is 100 nm - 5000 nm.

[0024] For the second solution provided by the present invention: an AlN thin film with anti-cracking function, which is prepared by the epitaxial growth method in the foregoing first solution.

[0025] Next, the effects of the foregoing AlN thin film with anti-cracking function are characterized and analyzed through specific examples.

[0026] Example 1

[0027] The specific epitaxial growth steps in this example are as follows:

[0028] (1) Deposit AlN on a 2-inch sapphire substrate in a pure hydrogen atmosphere at 900 °C; maintain the pure hydrogen atmosphere, heat up to 1200 °C, and perform high-temperature annealing for 10 minutes; after the annealing is completed, maintain the temperature, introduce ammonia gas, and perform high-temperature nitridation for 10 minutes to obtain an AlN buffer layer.

[0029] (2) Deposit the first AlN layer on the AlN buffer layer. The growth temperature of the first AlN layer is 1300 °C, and the thickness is 200 nm.

[0030] (3) Deposit the AlInN layer on the first AlN layer. The growth temperature of the AlInN layer is 1000 °C, and the thickness is 300 nm.

[0031] (4) Deposit the second AlN layer on the AlInN layer. The growth temperature of the second AlN layer is 1200 °C, and the thickness is 350 nm.

[0032] (5) Cool down to 1000 °C and anneal in a pure hydrogen atmosphere for 30 min. After annealing, an AlN void layer with a pore structure is formed.

[0033] (6) Continue to grow the third AlN layer on the second AlN layer at a growth temperature of 1200 °C and a thickness of 400 nm to obtain an AlN thin film sample.

[0034] The AlN thin film sample prepared in Example 1 was characterized by TEM. Its cross-sectional view is as Figure 2 shown. It can be seen that after annealing, many irregular pore structures are formed in the AlInN layer. It is precisely because the pore structure of the AlN void layer can fully release the thermal stress during the film growth process that the crystal quality of the subsequently grown third AlN layer is excellent.

[0035] Example 2

[0036] The specific epitaxial growth steps in this example are as follows:

[0037] (1) Deposit AlN on a 2-inch sapphire substrate in a pure hydrogen atmosphere at 900 °C; maintain the pure hydrogen atmosphere, heat up to 1200 °C, and perform high-temperature annealing for 10 min; after annealing is completed, maintain the temperature, introduce ammonia gas, and perform high-temperature nitridation for 10 min to obtain an AlN buffer layer.

[0038] (2) Deposit the first AlN layer on the AlN buffer layer. The growth temperature of the first AlN layer is 1300 °C and the thickness is 200 nm.

[0039] (3) Deposit an AlInN layer on the first AlN layer. The growth temperature of the AlInN layer is 1000 °C and the thickness is 300 nm.

[0040] (4) Deposit the second AlN layer on the AlInN layer. The growth temperature of the second AlN layer is 1200 °C and the thickness is 350 nm.

[0041] (5) Anneal at 1250 °C in a pure hydrogen atmosphere for 30 min. After annealing, an AlN void layer with a pore structure is formed.

[0042] (6) Continue to grow the third AlN layer on the second AlN layer at a growth temperature of 1200 °C and a thickness of 400 nm to obtain an AlN thin film sample.

[0043] Comparing the preparation steps of this Example 1, only the annealing temperature in step (5) is changed to 1250 °C in this example, and other process conditions are the same as those in Example 1.

[0044] Example 3

[0045] (1) Deposit AlN on a 2-inch sapphire substrate under a pure hydrogen atmosphere at 900 °C; maintain the pure hydrogen atmosphere, heat up to 1200 °C, perform high-temperature annealing for 10 min; after annealing, maintain the temperature, introduce ammonia gas, perform high-temperature nitridation for 10 min to obtain an AlN buffer layer.

[0046] (2) Deposit the first AlN layer on the AlN buffer layer. The growth temperature of the first AlN layer is 1300 °C and the thickness is 200 nm.

[0047] (3) Deposit an AlInN layer on the first AlN layer. The growth temperature of the AlInN layer is 1000 °C and the thickness is 300 nm.

[0048] (4) Deposit the second AlN layer on the AlInN layer. The growth temperature of the second AlN layer is 1200 °C and the thickness is 350 nm.

[0049] (5) Anneal at 1350 °C in a pure hydrogen atmosphere for 30 min to form an AlN void layer with a pore structure after annealing.

[0050] (6) Continuously grow the third AlN layer on the second AlN layer. The growth temperature is 1200 °C and the thickness is 400 nm to obtain an AlN thin film sample.

[0051] Comparing with the preparation steps of Example 1, in this example, only the annealing temperature in step (5) is changed to 1350 °C, and other process conditions are the same as those in Example 1.

[0052] Example 4

[0053] The specific epitaxial growth steps in this example are as follows:

[0054] (1) Deposit AlN on a 4-inch sapphire substrate under a pure hydrogen atmosphere at 900 °C; maintain the pure hydrogen atmosphere, heat up to 1200 °C, perform high-temperature annealing for 10 min; after annealing, maintain the temperature, introduce ammonia gas, perform high-temperature nitridation for 10 min to obtain an AlN buffer layer.

[0055] (2) Deposit the first AlN layer on the AlN buffer layer. The growth temperature of the first AlN layer is 1300 °C and the thickness is 200 nm.

[0056] (3) Deposit an AlInN layer on the first AlN layer. The growth temperature of the AlInN layer is 1000 °C and the thickness is 750 nm.

[0057] (4) Deposit a second AlN layer on the AlInN layer. The growth temperature of the second AlN layer is 1200 °C and the thickness is 350 nm.

[0058] (5) Cool down to 1000 °C and perform annealing in a pure hydrogen atmosphere. The annealing time is 30 min. After annealing, an AlN void layer with a pore structure is formed.

[0059] (6) Continue to grow a third AlN layer on the second AlN layer. The growth temperature is 1200 °C and the thickness is 400 nm to obtain an AlN thin film sample.

[0060] Comparing with the preparation steps of Example 1, in this example, the sapphire substrate has a specification of 4 inches, and the thickness of the AlInN layer in step (3) is set to 750 nm, and other process conditions are the same as those in Example 1.

[0061] Example 5

[0062] The specific epitaxial growth steps in this example are as follows:

[0063] (1) Deposit AlN on a 4-inch sapphire substrate under a pure hydrogen atmosphere at 900 °C; maintain the pure hydrogen atmosphere, heat up to 1200 °C, and perform high-temperature annealing for 10 min; after the annealing is completed, maintain the temperature, introduce ammonia gas, and perform high-temperature nitridation for 10 min to obtain an AlN buffer layer.

[0064] (2) Deposit a first AlN layer on the AlN buffer layer. The growth temperature of the first AlN layer is 1300 °C and the thickness is 200 nm.

[0065] (3) Deposit an AlInN layer on the first AlN layer. The growth temperature of the AlInN layer is 1000 °C and the thickness is 400 nm.

[0066] (4) Deposit a second AlN layer on the AlInN layer. The growth temperature of the second AlN layer is 1200 °C and the thickness is 350 nm.

[0067] (5) Cool down to 1000 °C and perform annealing in a pure hydrogen atmosphere. The annealing time is 30 min. After annealing, an AlN void layer with a pore structure is formed.

[0068] (6) Continue to grow a third AlN layer on the second AlN layer. The growth temperature is 1200 °C and the thickness is 400 nm to obtain an AlN thin film.

[0069] Comparing with the preparation steps of Example 4, in this example, the sapphire substrate has a specification of 4 inches, and the thickness of the AlInN layer in step (3) is set to 400 nm, and other process conditions are the same as those in Example 4.

[0070] Comparative Example 1

[0071] The specific epitaxial growth steps in this comparative example are as follows:

[0072] (1) Deposit AlN on a 2-inch sapphire substrate under a pure hydrogen atmosphere at 900 °C; maintain the pure hydrogen atmosphere, heat up to 1200 °C, perform high-temperature annealing, and the annealing time is 10 min; after the annealing is completed, maintain the temperature, introduce ammonia gas, and perform high-temperature nitridation, and the nitridation time is 10 min to obtain an AlN buffer layer.

[0073] (2) Deposit the first AlN layer on the AlN buffer layer. The growth temperature of the first AlN layer is 1300 °C and the thickness is 200 nm.

[0074] (3) Deposit the second AlN layer on the first AlN layer. The growth temperature of the second AlN layer is 1200 °C and the thickness is 350 nm.

[0075] (4) Continuously grow the third AlN layer on the second AlN layer. The growth temperature is 1200 °C and the thickness is 400 nm to obtain an AlN thin film sample.

[0076] In this comparative example, the growth and annealing steps of the AlInN layer are removed, and the other steps are the same as those in Example 1.

[0077] Comparative Example 2

[0078] The specific epitaxial growth steps in this comparative example are as follows:

[0079] (1) Deposit AlN on a 4-inch sapphire substrate under a pure hydrogen atmosphere at 900 °C; maintain the pure hydrogen atmosphere, heat up to 1200 °C, perform high-temperature annealing, and the annealing time is 10 min; after the annealing is completed, maintain the temperature, introduce ammonia gas, and perform high-temperature nitridation, and the nitridation time is 10 min to obtain an AlN buffer layer.

[0080] (2) Deposit the first AlN layer on the AlN buffer layer. The growth temperature of the first AlN layer is 1300 °C and the thickness is 200 nm.

[0081] (3) Deposit the second AlN layer on the first AlN layer. The growth temperature of the second AlN layer is 1200 °C and the thickness is 350 nm.

[0082] (4) Continuously grow the third AlN layer on the second AlN layer. The growth temperature is 1200 °C and the thickness is 400 nm to obtain an AlN thin film sample.

[0083] In this comparative example, the growth and annealing steps of the AlInN layer are removed, and the other steps are the same as those in Example 4.

[0084] The cracking situation, surface morphology, and crystal quality of the prepared AlN thin film samples in the above Examples 1-5 and Comparative Examples 1-2 were counted, and the results are shown in Table 1.

[0085] Table 1

[0086]

[0087] In Table 1, Comparative Example 1 and Comparative Example 2 are actually traditional AlN thin film preparation methods under different substrate specifications, that is, the AlInN layer is not introduced and annealing is not performed on it. It can be seen that as the substrate size specification increases, the AlN thin film is more likely to crack, and the surface morphology and crystal quality are also relatively poor. After introducing the AlN void layer with a pore structure, both Example 1 and Example 4 can effectively avoid film layer cracking, and the surface morphology and crystal quality are also improved.

[0088] Based on the content recorded in Table 1, by comparing Examples 1-3, it can be seen that under the same substrate specification conditions, the annealing temperature of Example 2 exceeds the growth temperature of the second AlN layer, and the annealing temperature of Example 3 exceeds the growth temperatures of the first AlN layer and the second AlN layer. Since the annealing temperature exceeds the previously defined requirements, the surface damage of the AlN thin film sample becomes more serious. Therefore, the annealing temperature conditions of the AlInN layer need to be strictly controlled to obtain an AlN thin film with better surface morphology.

[0089] Based on the content recorded in Table 1, by comparing Examples 1, 4, and 5, it can be seen that compared with Example 1, in Example 4, due to the increase in the substrate size specification, in order to meet the demand for the release of its thermal stress, the thickness of the AlInN layer is thickened and meets the previously defined range. At this time, the thermal stress can be released well, and cracking can be effectively avoided. In Example 5, after the substrate size specification increases, the thickness of the AlInN layer increases less and does not meet the previously defined range. At this time, the pore structure in the AlN void layer after annealing is not sufficient to fully release the thermal stress, resulting in a certain accumulation of thermal stress, and thus there will be a slight cracking phenomenon. This shows that for different substrate specifications, different thicknesses of the AlInN layer need to be used to achieve the effect of fully releasing the thermal stress.

[0090] Different from the prior art, the present invention provides an AlN thin film with an anti-cracking function and its epitaxial growth method. During the deposition of the AlN film layer, by introducing the AlInN layer and performing annealing treatment, an AlN void layer with a pore structure is formed. The pore structure enables the thermal stress to be fully released during the subsequent growth of AlN, which can effectively prevent the cracking of the AlN film layer and improve the growth quality of the AlN film layer.

[0091] It should be noted that the above embodiments all belong to the same inventive concept. Each embodiment has its own focus in description. For the parts not described in detail in individual embodiments, reference can be made to the descriptions in other embodiments.

[0092] The above-described embodiments only express the implementation manners of the present invention. The descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An epitaxial growth method of an AlN thin film with a crack prevention function, characterized in that, It includes the following steps: S1, grow an AlN buffer layer, a first AlN layer, an AlInN layer, and a second AlN layer on a sapphire substrate in sequence; S2, perform an annealing treatment in a pure hydrogen atmosphere until In in the AlInN layer is completely separated, and form an AlN void layer with a pore structure; S3, continue to grow a third AlN layer on the second AlN layer to obtain an AlN thin film with an anti-cracking function; In the S1 step, the growth temperature of the AlInN layer is 700 - 1000 °C; The annealing temperature in the S2 step is lower than the growth temperature of the second AlN layer in the S1 step, and the annealing temperature in the S2 step is lower than the growth temperature of the third AlN layer in the S3 step; The specific process steps of the annealing treatment in the S2 step are: after the growth of the second AlN layer is completed, cool down to 1000 °C - 1200 °C, perform annealing in a pure hydrogen atmosphere, the annealing time is 5 - 60 min, and an AlN void layer with a pore structure is formed after annealing; after the annealing treatment, there is no pore-like structure in the first AlN layer and the second AlN layer.

2. The epitaxial growth method of the AlN thin film with anti-cracking function according to claim 1, characterized in that, The specific process steps of the AlN buffer layer in the S1 step are: Deposit AlN in a pure hydrogen atmosphere at 800 °C - 1100 °C; Maintain the pure hydrogen atmosphere, heat up to 1100 °C - 1300 °C, perform high-temperature annealing, and the annealing time is 5 - 15 min; After the annealing is completed, maintain the temperature, introduce ammonia gas, perform high-temperature nitridation, and the nitridation time is 5 - 15 min to obtain an AlN buffer layer.

3. The epitaxial growth method of the AlN thin film with anti-cracking function according to claim 1, characterized in that, In the S1 step, the growth temperature of the first AlN layer is 1200 - 1400 °C, and the thickness is 0.1 nm - 500 nm.

4. The epitaxial growth method of the AlN thin film with anti-cracking function according to claim 1, characterized in that, The size of the sapphire substrate is 2 inches, the thickness of the sapphire substrate is 350 μm - 700 μm, and the thickness of the AlInN layer is 1 nm - 500 nm.

5. The epitaxial growth method of the AlN film with anti-cracking function according to claim 1, characterized in that, The size of the sapphire substrate is 4 inches, the thickness of the sapphire substrate is 700 μm - 1000 μm, and the thickness of the AlInN layer is 600 nm - 1500 nm.

6. The epitaxial growth method of the AlN thin film with an anti-cracking function according to claim 1, wherein, In the S1 step, the growth temperature of the second AlN layer is 1100 - 1300 °C, and the thickness is 1 nm - 500 nm.

7. The epitaxial growth method of the AlN thin film with anti-cracking function according to claim 1, characterized in that, In the S3 step, the growth temperature of the third AlN layer is 1200 - 1400 °C, and the thickness is 100 nm - 5000 nm.

8. An AlN thin film with a function of preventing cracking, characterized in that, The AlN thin film with an anti-cracking function is prepared by the epitaxial growth method described in any one of claims 1 - 7.

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