A method for preparing single N-polar AlN film
By covering the high-temperature resistant template on a silicon-free substrate and forming an AlON layer, separating and removing the Al polar AlN layer, the problem of difficulty in preparing a single N polar AlN film is successfully solved, and high-efficiency and high-quality film preparation is achieved.
Patent Information
- Application Number
- CN202211414050.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-11
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2042-11-11
AI Technical Summary
It is difficult to prepare a single N-polar AlN film on a silicon-free substrate with a narrow growth window, and usually only a single Al polar AlN and hybrid polar AlN film can be obtained.
By covering the high-temperature resistant first template on the AlN template, high-temperature annealing is performed to form an AlON layer, separate the Al polar AlN layer and the N polar AlN layer, and remove the AlON layer and the Al polar AlN layer under specific etching conditions. A single N-polar AlN film was obtained.
It effectively avoids decomposition and surface damage of AlN film during high-temperature annealing, ensures the preparation of a single N-polar AlN layer, improves the preparation efficiency and quality of the film, and avoids problems such as over-etching and warping.
Smart Images
Figure CN116043188B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing a thin film, and in particular to a method for preparing a single N-polar AlN thin film. Background Art
[0002] In recent years, electronic devices based on N-polar AlN have received extensive attention due to their lower contact resistivity and strong back barrier structure. At the same time, N-polar AlN also has important application prospects in the regulation of polarization fields of light-emitting devices due to its opposite polarization direction. However, due to the very narrow growth window of N-polar AlN films, especially for AlN films grown on silicon-free substrates (i.e., substrates that do not contain Si components, such as excluding SiC substrates and Si substrates), usually only single Al-polar AlN and mixed-polarity (both Al-polar and N-polar) AlN films can be obtained, and it is difficult to obtain single N-polar AlN film materials. Summary of the invention
[0003] In order to solve the problem that a single N-polar AlN thin film material is difficult to prepare, the inventors conducted a lot of research and experiments and found that when the AlN film is annealed, if an AlON layer is formed in the AlN film, the formed AlON layer can separate the N-polar AlN layer and the Al-polar AlN layer formed by the annealing of the AlN film; moreover, the special etching conditions required for the AlON layer can simultaneously ensure the full etching of the Al-polar AlN and avoid the excessive etching of the N-polar AlN. Then, under the condition of a high etching selectivity, after removing the Al-polar AlN layer and the AlON layer, a single N-polar AlN layer can be obtained. To this end, according to one aspect of the present invention, a method for preparing a single N-polar AlN thin film is provided, comprising the following steps:
[0004] S10: covering the AlN template with a first template, wherein the AlN template is an AlN template obtained by depositing an AlN film on a high temperature resistant silicon-free substrate, the first template covers an upper surface of the AlN film in the AlN template, and the first template contains at least one of an Al component and a N component and is resistant to high temperatures;
[0005] S20: annealing the AlN template covered with the first template at a high temperature to form an AlON layer in the AlN film, and forming an N-polar AlN layer and an Al-polar AlN layer on both sides of the AlON layer in the AlN film respectively;
[0006] S30: etching and removing the AlON layer and the Al-polar AlN layer to obtain an AlN template having a single N-polar AlN thin film.
[0007] Since the upper surface of the AlN film is covered with a high-temperature resistant first template containing Al components and / or N components during the high-temperature annealing of the AlN template, the problem of decomposition or surface damage of the AlN film during the high-temperature annealing can be avoided; moreover, the AlN template configured in this way can form an Al-polar AlN layer, an AlON layer and an N-polar AlN layer distributed in sequence during the high-temperature annealing process. Since the etching conditions of the AlON layer are relatively special, the AlON layer located between the Al-polar AlN layer and the N-polar AlN layer can simultaneously ensure sufficient etching of the Al-polar AlN and avoid excessive etching of the N-polar AlN. Therefore, an AlN film with a single N-polarity can be obtained by removing the Al-polar AlN layer and the AlON layer.
[0008] In some embodiments, the thickness of the AlN film is greater than 20 nm; and / or the thickness of the AlN film is less than 100 nm. Controlling the thickness of the AlN film to be greater than 20 nm can avoid the inability to form an AlON layer during high-temperature annealing due to the AlN film being too thin; controlling the thickness of the AlN film to be less than 100 nm can reduce the workload of removing the Al-polar AlN layer and the AlON layer, and at the same time, can also avoid the AlN template from being severely warped and surface cracked due to the AlN film being too thick.
[0009] In some embodiments, in step S20, the annealing temperature is 1500° C.-1800° C., the annealing atmosphere contains nitrogen, and / or the annealing time is 10 min-24 h, so as to suppress the decomposition of AlN and ensure that the AlN template is subjected to high temperature annealing to sequentially form an Al-polar AlN layer, an AlON layer, and an N-polar AlN layer in the AlN film.
[0010] In some embodiments, the first template is also an AlN template, and when two AlN templates overlap each other, the upper surfaces of the AlN films in the two AlN templates are in contact with each other, thereby doubling the preparation efficiency of a single N-polar AlN film.
[0011] In some embodiments, the silicon-free substrate contains oxygen; and / or the first template contains oxygen. Thus, the first template or silicon-free substrate containing oxygen can provide O elements to the AlN film in the AlN template when the AlN template is subjected to high-temperature annealing, so that the AlN film can form an AlON layer after high-temperature annealing even if the atmosphere of the high-temperature annealing does not contain oxygen; and, since the content of oxygen elements provided by the silicon-free substrate or the first template is low, the formation of a thick AlON layer can be avoided, thereby reducing the time spent on subsequent etching. In particular, when the first template is also an AlN template, and the upper surfaces of the AlN films in the two AlN templates are annealed in a manner that they are in contact with each other, an N-polar AlN layer can be formed on the side of the AlON layer in the AlN film that faces the silicon-free substrate, and an Al-polar AlN layer can be formed on the side of the AlON layer in the AlN film that faces away from the substrate, so as to facilitate the subsequent removal of the AlON layer and the Al-polar AlN layer.
[0012] In some embodiments, the silicon-free substrate is an AlN ceramic substrate or a BN ceramic substrate, thereby making the silicon-free substrate resistant to high temperatures and preventing the AlN film in the AlN template from decomposing during high-temperature annealing.
[0013] In some embodiments, in step S20, the annealing atmosphere further includes oxygen, and the volume percentage of oxygen in the annealing atmosphere is not greater than 2%, so as to ensure that an AlON layer can be formed in the AlN film when the AlN template is subjected to high temperature annealing; and, since the volume percentage of oxygen in the annealing atmosphere is controlled to be not greater than 2%, a thick AlON layer formed in the AlN film during high temperature annealing can be avoided.
[0014] In some embodiments, in step S30, etching and removing the AlON layer and the Al-polar AlN layer is implemented as follows:
[0015] First, the Al-polar AlN layer is removed by etching using an atmosphere containing X2 but not containing BX3;
[0016] Then, the AlON layer is removed by etching using an atmosphere containing BX3 but not containing X2;
[0017] Wherein, X is a halogen element.
[0018] Since X2 has a high etching efficiency for Al-polar AlN layer, and since when the atmosphere does not contain BX3, BX2 that can break the Al-O bond in the AlON layer will not be produced due to the decomposition of BX3 +Therefore, when etching is first performed using an atmosphere containing X2 but not containing BX3, the AlON layer can be almost not etched while the Al polar AlN layer is completely removed, thereby being able to well control the etching endpoint of the Al polar AlN layer; and, since the AlON layer separates the N polar AlN layer from the Al polar AlN layer, it can be ensured that while etching and removing the Al polar AlN layer, the etching atmosphere will not damage the N polar AlN layer. After the Al polar AlN layer is etched, when etching is performed using an atmosphere containing BX3 but not containing X2, since the decomposition efficiency of BX3 is not as high as that of X2, a smaller amount of X is generated compared to X2. - It is beneficial to inhibit the etching of N-polar AlN. Moreover, since the thickness of the AlON layer is thin, even if BX3 decomposes BX2 + Very rarely, complete removal of the AlON layer can be guaranteed.
[0019] In some embodiments, after step S30, the preparation method of the present invention further comprises the following steps:
[0020] S40`: preserving the AlN template having a single N-polar AlN film in an oxygen-isolated state.
[0021] This can prevent the surface of the obtained AlN thin film having a single N polarity from being oxidized.
[0022] In some embodiments, after step S30, the preparation method of the present invention further comprises the following steps:
[0023] S40: epitaxially growing an AlN layer on the upper surface of the AlN thin film of the AlN template having a single N-polar AlN thin film.
[0024] Thus, an AlN template having a single N-polar AlN film with good surface flatness and high crystal quality can be obtained.
[0025] In some embodiments, after step S30 and before step S40, the preparation method of the present invention further comprises at least one of the following steps:
[0026] S301: high temperature baking of the AlN template having a single N-polar AlN film;
[0027] S401: performing nitridation treatment on the upper surface of the AlN film of the AlN template having a single N-polar AlN film.
[0028] Therefore, high temperature baking can effectively remove residual oxygen elements on the surface of the AlN film, inhibit the formation of AlON structure in the early growth stage, and thus inhibit the formation of Al-polar AlN in the early growth stage; nitridation treatment can further inhibit the formation of Al-polar AlN in the early growth stage.
[0029] In some embodiments, the baking atmosphere of the high temperature baking contains hydrogen elements, thereby effectively removing oxygen elements and the like remaining on the surface of the AlN film. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 A schematic diagram of a process for preparing a single N-polar AlN thin film according to an embodiment of the present invention;
[0031] Figure 2 for Figure 1 The scanning electron microscope structure diagram of the AlN template obtained after heat treatment in the single N-polar AlN film preparation method shown;
[0032] Figure 3 This is a schematic diagram of the process of oxygen isolation storage according to one embodiment of the present invention;
[0033] Figure 4 A schematic diagram of the process of epitaxial growth according to one embodiment of the present invention;
[0034] Figure 5 A schematic diagram of a high temperature baking process according to an embodiment of the present invention;
[0035] Figure 6 A schematic diagram of a nitriding process according to an embodiment of the present invention;
[0036] Reference numerals: 20, silicon-free substrate; 30, N-polar AlN layer; 40, AlON layer; 50, Al-polar AlN layer. DETAILED DESCRIPTION
[0037] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.
[0038] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include" and "comprise" include not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such processes, methods, articles or equipment. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the existence of other identical elements in the process, method, article or equipment that includes the elements. The terms used in this article are generally commonly used terms by those skilled in the art. If they are inconsistent with commonly used terms, the terms in this article shall prevail.
[0039] Herein, the term "high temperature resistance" refers to the property of not decomposing at a high temperature of 1500°C.
[0040] Herein, the term "silicon-free substrate" refers to a substrate that does not contain silicon element.
[0041] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0042] Figure 1 A method for preparing a single N-polar AlN thin film according to an embodiment of the present invention is schematically shown.
[0043] like Figure 1 As shown, the method for preparing a single N-polar AlN film comprises the following steps:
[0044] S10: covering the first template on the AlN template, wherein the AlN template is an AlN template obtained by depositing an AlN film on a silicon-free substrate, the first template covers the upper surface of the AlN film in the AlN template, and the first template contains at least one of an Al component and a N component and is resistant to high temperature;
[0045] S20: annealing the AlN template covered with the first template at a high temperature to form an AlON layer in the AlN film, and forming an N-polar AlN layer and an Al-polar AlN layer on both sides of the AlON layer in the AlN film respectively;
[0046] S30: etching and removing the AlON layer and the Al-polar AlN layer to obtain an AlN template having a single N-polar AlN thin film.
[0047] In step S10, an AlN (aluminum nitride) template is obtained by depositing an AlN thin film material on a silicon-free substrate. The deposition method may be at least one of metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), physical vapor deposition (PVD), pulsed laser deposition (PLD), and atomic layer deposition (ALD). The specific deposition process may be a deposition process commonly used in the prior art. The present invention does not limit the specific process for depositing the AlN thin film on the silicon-free substrate.
[0048] In step S10, exemplarily, the first template can adopt an epitaxial structure whose substrate is an AlN ceramic substrate or a BN (boron nitride) ceramic substrate, or an AlN template. As long as the first template contains Al component and / or N component and has high temperature resistance, it can become a candidate material for the first template of the present invention.
[0049] In step S20, the ALN template covered with the first template is subjected to high temperature annealing, specifically, the upper surface of the AlN film of the AlN template in step S10 (ie, the surface of the AlN film facing away from the silicon-free substrate) is covered with the first template and then subjected to high temperature annealing.
[0050] In step S20 , the high temperature annealing process is selected to form an AlON layer in the AlN film, and to form an N-polar AlN layer and an Al-polar AlN layer on both sides of the AlON layer in the AlN film.
[0051] In step S30, the process for etching away the AlON layer and the Al-polar AlN layer can adopt the process for etching away the AlON layer and the Al-polar AlN layer in the prior art. For example, the etching is performed by using an inductively coupled plasma etching (ICP etching for short) technique. As one implementation method for confirming the etching endpoint, the etching endpoint can be determined by controlling the etching thickness. As another implementation method for confirming the etching endpoint, the surface morphology after etching can also be observed by an electron microscope to determine that the AlON layer and the Al-polar AlN layer are completely removed.
[0052] When the preparation method of the present invention is adopted, since the upper surface of the AlN film is covered with a high-temperature resistant first template containing an Al component and / or an N component during the high-temperature annealing of the AlN template, the problem of decomposition or surface damage of the AlN film during the high-temperature annealing can be avoided; and the AlN template arranged in this way can form an Al-polar AlN layer, an AlON layer and an N-polar AlN layer distributed in sequence during the high-temperature annealing, thereby, an AlN film with a single N polarity can be obtained by removing the Al-polar AlN layer and the AlON layer.
[0053] In some preferred embodiments, in step S10, the thickness of the AlN film is controlled to be greater than 20 nm, thereby preventing the AlON layer from being unable to be formed during the high-temperature annealing treatment due to the AlN film being too thin.
[0054] In some preferred embodiments, in step S10, the thickness of the AlN film is controlled to be less than 100 nm, thereby avoiding the problem of time-consuming removal of the Al-polar AlN layer and the AlON layer due to the thick Al-polar AlN layer and the AlON layer, and also avoiding severe warping and surface cracking of the AlN template due to the thick AlN film.
[0055] In some preferred embodiments, in step S10, the thickness of the AlN film is controlled to be greater than 20 nm, and the thickness of the AlN film is controlled to be less than 100 nm. Thus, the conditions for forming the AlON layer, quickly removing the Al-polar AlN layer and the AlON layer, and avoiding severe warping and surface cracking of the AlN film can be met at the same time.
[0056] In some preferred embodiments, in step S10, the first template is also an AlN template, and when the two AlN templates overlap each other, the upper surfaces of the AlN films in the two AlN templates are in contact with each other. Thus, after one annealing treatment, two AlN films with a single N-polarity can be obtained, thereby doubling the preparation efficiency of the single N-polarity AlN film. Moreover, when the first template is also an AlN template, and the upper surfaces of the AlN films in the two AlN templates are annealed in a contact manner, an N-polar AlN layer can be formed on the side of the AlON layer in the AlN film facing the silicon-free substrate, and an Al-polar AlN layer can be formed on the side of the AlON layer in the AlN film facing away from the substrate. Therefore, only the Al-polar AlN layer and the AlON layer need to be removed subsequently to expose the N-polar AlN layer without removing the silicon-free substrate, thereby greatly improving the preparation efficiency of a single N-polar AlN film; moreover, a single N-polar AlN layer can be obtained by completely removing the AlON layer. For example, when removing the AlON layer by etching, the etching can be performed to a position 4nm-5nm below the AlON layer (the side of the AlON layer facing the silicon-free substrate) to ensure that the AlON layer is completely etched away.
[0057] In some preferred embodiments, in step S10, the silicon-free substrate contains oxygen; and / or the first template contains oxygen. The silicon-free substrate containing oxygen may be, for example, a sapphire substrate. Thus, the first template containing oxygen or the silicon-free substrate may provide oxygen to the AlN film in the AlN template when the AlN template is subjected to high-temperature annealing, so that the AlN film may form an AlON layer after high-temperature annealing even if the atmosphere of the high-temperature annealing does not contain oxygen; and, since the content of oxygen provided by the silicon-free substrate or the first template is low, the formation of a thick AlON layer may be avoided, thereby reducing the time spent on subsequent etching.
[0058] In other preferred embodiments, in step S10, the silicon-free substrate is an AlN ceramic substrate or a BN ceramic substrate. In this way, the silicon-free substrate can be made to have high temperature resistance and the AlN film in the AlN template can be prevented from decomposing during the high temperature annealing process. Specifically, when the silicon-free substrate is an oxygen-free substrate such as an AlN ceramic substrate or a BN ceramic substrate, and the first template also does not contain oxygen, it is necessary to introduce an oxygen-containing atmosphere into the annealing atmosphere in step S20 to ensure that the AlN film in the AlN template can form a thin AlON layer during the high temperature annealing process.
[0059] In some preferred embodiments, in step S20, the annealing temperature is 1500°C-1800°C, the annealing atmosphere contains nitrogen, and / or the annealing time is 10min-24h. Thus, by setting nitrogen in the annealing atmosphere, the decomposition of AlN during high-temperature annealing can be avoided, and the problem that the AlN template cannot be effectively heat-treated due to too low a temperature or too short a time, resulting in the inability to form an Al-polar AlN layer, an AlON layer, and an N-polar AlN layer in the AlN film can be avoided; moreover, the problem that AlN is decomposed due to too high a temperature or too long a time, or the Al-polar AlN layer, an AlON layer, and an N-polar AlN layer formed are recrystallized can be avoided.
[0060] In some preferred embodiments, in step S20, the annealing atmosphere also includes oxygen, and the volume percentage of oxygen in the annealing atmosphere is not greater than 2%, especially when the silicon-free substrate and the first template do not contain oxygen. Thus, when the AlN template is subjected to high-temperature annealing, oxygen elements can be introduced into the AlN film in the AlN template, thereby ensuring that a thinner AlON layer can be formed in the AlN film when the AlN template is subjected to high-temperature annealing. In this embodiment, if the thickness of the AlN film in the AlN template is controlled to be 20nm-100nm, after annealing, an AlON layer with a high oxygen content will be formed at a position of 10nm-30nm above the AlN / silicon-free substrate interface (the junction of the AlN film and the silicon-free substrate) (located in the AlN film), the thickness of the AlON layer is less than 2nm, the AlON layer is a single N-polar AlN layer below, and the AlON layer (the side of the AlON layer away from the silicon-free substrate) is a single Al-polar AlN layer above. Therefore, when the AlON layer and the Al-polar AlN layer are subsequently removed, the end point of the removal can be controlled by controlling the thickness of the removed AlON layer and the Al-polar AlN layer.
[0061] In some preferred embodiments, in step S30, etching and removing the AlON layer and the Al-polar AlN layer is implemented as follows:
[0062] First, the Al-polar AlN layer is removed by etching using an atmosphere containing X2 but not containing BX3;
[0063] Then, the AlON layer is removed by etching using an atmosphere containing BX3 but not containing X2;
[0064] Wherein, X is a halogen element, for example, X is F, Cl, Br, I, etc. Exemplarily, X2 is Cl2, and BX3 is BCl3. Since Cl2 has a high etching efficiency for the Al-polar AlN layer, and since when the atmosphere does not contain BCl3, BCl3 will not be decomposed to produce BCl2 that can break the Al-O bond in the AlON layer. +Therefore, when etching is first performed using an atmosphere containing Cl2 but not containing BCl3, the AlON layer can be almost not etched while the Al polar AlN layer is completely removed, thereby being able to well control the etching endpoint of the Al polar AlN layer; and, since the AlON layer separates the N polar AlN layer from the Al polar AlN layer, it can be ensured that while etching and removing the Al polar AlN layer, the etching atmosphere will not damage the N polar AlN layer. After the Al polar AlN layer is etched, when etching is performed using an atmosphere containing BCl3 but not containing Cl2, since the decomposition efficiency of BCl3 is not as high as that of Cl2, less Cl is produced compared to Cl2. - It is beneficial to inhibit the etching of N-polar AlN. Moreover, since the thickness of the AlON layer is thin, even if BCl3 decomposes BCl2 + Very rarely, complete removal of the AlON layer can be guaranteed.
[0065] In some preferred embodiments, after step S30, Figure 3 As shown, the preparation method of the present invention also includes the following steps:
[0066] S40`: preserving the AlN template having a single N-polar AlN film in an oxygen-isolated state.
[0067] Thus, the surface of the obtained single N-polar AlN film can be prevented from being oxidized to regenerate AlON. Exemplarily, the oxygen-isolated storage can be performed by placing the AlN template having the single N-polar AlN film obtained after the step S30 in an inert gas such as neon or argon.
[0068] In some other preferred embodiments, after step S30, Figure 4 As shown, the preparation method of the present invention also includes the following steps:
[0069] S40: epitaxially growing an AlN layer on the upper surface of the AlN thin film of the AlN template having a single N-polar AlN thin film.
[0070] Exemplarily, at least one of MOCVD, MBE, PVD, PLD and ALD can be used, and the specific deposition process can adopt the deposition process commonly used in the prior art. The present invention does not limit the specific process of epitaxially growing the AlN layer on the upper surface of the AlN film of the AlN template with a single N-polar AlN film. Thus, an AlN template with a single N-polar AlN film having good surface flatness and high crystal quality can be obtained.
[0071] In some preferred embodiments, after step S30 and before step S40, as Figure 5As shown, the preparation method of the present invention also includes the following steps:
[0072] S301: High temperature baking is performed on the AlN template having a single N-polar AlN film. The temperature of the high temperature baking is controlled at 1050-1500° C. If the temperature is too low, the O element cannot be removed. If the temperature is too high, the N-polar AlN is easily decomposed.
[0073] Exemplarily, the AlN template with a single N-polar AlN film obtained in step S30 can be heated to above 1500°C, and the baking equipment can be, for example, an epitaxial growth equipment. Thus, the oxygen elements and the like remaining on the surface of the AlN film can be effectively removed, and the formation of the AlON structure in the early growth stage can be suppressed, thereby suppressing the formation of Al-polar AlN in the early growth stage. Furthermore, the baking atmosphere of the high-temperature baking contains hydrogen elements. Thus, the oxygen elements and the like remaining on the surface of the AlN film can be more effectively removed.
[0074] In some preferred embodiments, after step S30 and before step S40, as Figure 6 As shown, the preparation method of the present invention also includes the following steps:
[0075] S401: performing nitridation treatment on the upper surface of the AlN film of the AlN template having a single N-polar AlN film.
[0076] For example, during the baking process, a proper amount of nitrogen source is introduced into the reaction chamber to perform nitridation treatment on the upper surface of the AlN film of the AlN template having a single N-polar AlN film, thereby further suppressing the formation of Al-polar AlN in the early growth stage.
[0077] In some preferred implementations, step S301 and step S401 may be selected separately or applied in combination, and when the two are applied in combination, there is no strict requirement on the order of application, that is, step S301 may be performed before step S401 or after step S401.
[0078] Example 1
[0079] In the first step, an AlN film is deposited on a sapphire substrate by MOCVD, and the deposited film thickness is 20 nm to obtain an AlN template.
[0080] In the second step, two AlN templates are placed opposite to each other so that the upper surfaces of the AlN films in the two AlN templates are attached to each other to form a dual template unit.
[0081] The third step is to subject the double template unit to high temperature annealing treatment, specifically: placing the double template unit in an annealing furnace with an annealing atmosphere of oxygen and nitrogen volume ratio of 1:99, annealing for 24 hours at an annealing temperature of 1500°C. The structure of the treated AlN template is shown in the figure Figure 2 As shown, after the AlN film is subjected to high temperature annealing treatment, an N-polar AlN layer and an Al-polar AlN layer are formed in the AlN film, and an AlON layer is formed in the N-polar AlN layer and the Al-polar AlN layer. Meanwhile, the N-polar AlN layer is adjacent to the sapphire substrate.
[0082] In the fourth step, the annealed AlN template is etched from its upper surface by ICP method. First, the Al-polar AlN layer is removed by etching with an atmosphere containing Cl2 but not containing BCl3. Then, the AlON layer is removed by etching with an atmosphere containing BCl3 but not containing Cl2. Until the upper surface of the AlN template is an N-polar AlN layer, an AlN template with a single N-polar AlN film is formed.
[0083] Example 2
[0084] In the first step, an AlN film is deposited on a sapphire substrate by PVD, and the deposited film thickness is 100 nm to obtain an AlN template.
[0085] In the second step, two AlN templates are placed opposite to each other so that the upper surfaces of the AlN films in the two AlN templates are attached to each other to form a dual template unit.
[0086] The third step is to subject the double template unit to high temperature annealing treatment, specifically: placing the double template unit in an annealing furnace with an annealing atmosphere of oxygen and nitrogen volume ratio of 2:98, annealing for 10 minutes, and the annealing temperature is 1800°C.
[0087] In the fourth step, the annealed AlN template is etched from its upper surface by ICP method. First, the Al-polar AlN layer is removed by etching with an atmosphere containing Cl2 but not containing BCl3. Then, the AlON layer is removed by etching with an atmosphere containing BCl3 but not containing Cl2. Until the upper surface of the AlN template is an N-polar AlN layer, an AlN template with a single N-polar AlN film is formed.
[0088] Example 3
[0089] The difference between this embodiment and embodiment 2 mainly lies in the third step, in which:
[0090] In the third step, the double template unit is subjected to high temperature annealing treatment, specifically: the double template unit is placed in an annealing furnace with an annealing atmosphere of pure nitrogen, annealed for 2 hours, and the annealing temperature is 1800°C.
[0091] Example 4
[0092] The difference between this embodiment and embodiment 1 mainly lies in the first step, in which:
[0093] In the first step, an AlN thin film is deposited on an AlN ceramic substrate using PLD, and the deposited film thickness is 30 nm to obtain an AlN template.
[0094] Example 5
[0095] The difference between this embodiment and embodiment 1 mainly lies in the first step, in which:
[0096] In the first step, an AlN film is deposited on a BN ceramic substrate using MBE, and the deposited film thickness is 50 nm to obtain an AlN template.
[0097] Example 6
[0098] The difference between this embodiment and embodiment 5 mainly lies in the second step, in which:
[0099] In the second step, the first template obtained by preparing an epitaxial structure on an AlN ceramic substrate is covered on the AlN template, and the epitaxial structure of the substrate being the AlN ceramic substrate is covered on the upper surface of the AlN film in the AlN template to form a dual template unit.
[0100] Example 7
[0101] The difference between this embodiment and embodiment 1 mainly lies in the first step and the second step, wherein:
[0102] In the first step, an AlN film is deposited on a sapphire substrate by ALD, and the deposited film thickness is 60 nm to obtain an AlN template.
[0103] In the second step, the first template obtained by preparing an epitaxial structure on an AlN ceramic substrate is covered on the AlN template, and the epitaxial structure of the substrate being the AlN ceramic substrate is covered on the upper surface of the AlN film in the AlN template to form a dual template unit.
[0104] Example 8
[0105] The main difference between this embodiment and embodiment 1 is that after the fourth step, the following steps are further included:
[0106] Step 5: baking the AlN template with a single N-polar AlN film under the protection of a hydrogen atmosphere by PVD;
[0107] Step 6, continuing to use PVD to perform nitridation treatment on the upper surface of the AlN film of the AlN template having a single N-polar AlN film;
[0108] In the seventh step, an AlN epitaxial growth layer is epitaxially grown on the upper surface of the AlN film of the AlN template having a single N-polar AlN film by PVD to obtain a single N-polar AlN film product.
[0109] Example 9
[0110] The main difference between this embodiment and embodiment 1 is that after the fourth step, the following steps are further included:
[0111] Step 5: baking the AlN template with a single N-polar AlN film under the protection of a hydrogen atmosphere by MOCVD;
[0112] In the sixth step, an AlN epitaxial growth layer is epitaxially grown on the upper surface of the AlN film of the AlN template having a single N-polar AlN film by using MOCVD to obtain a single N-polar AlN film product.
[0113] Example 10
[0114] The main difference between this embodiment and embodiment 1 is that after the fourth step, the following steps are further included:
[0115] Step 5, using ALD to perform nitridation treatment on the upper surface of the AlN film of the AlN template having a single N-polar AlN film;
[0116] In the sixth step, an AlN epitaxial growth layer is epitaxially grown on the upper surface of the AlN film of the AlN template having a single N-polar AlN film by using ALD to obtain a single N-polar AlN film product.
[0117] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.
Claims
1. A method for preparing a single N-polar AlN thin film, characterized in that: The following steps are involved: S10: Covering a first template on an AlN template, wherein the AlN template is an AlN template obtained by depositing an AlN thin film on a high temperature resistant silicon-free substrate, the first template covers an upper surface of the AlN thin film in the AlN template, and the first template contains at least one of an Al component and a N component and is resistant to high temperatures; S20: annealing the AlN template covered with the first template at a high temperature to form an AlON layer in the AlN film, and forming an N-polar AlN layer and an Al-polar AlN layer on both sides of the AlON layer in the AlN film respectively; S30: etching and removing the AlON layer and the Al-polar AlN layer to obtain an AlN template having a single N-polar AlN film; In step S20, the annealing temperature is 1500°C-1800°C; In step S30, the etching and removing of the AlON layer and the Al-polar AlN layer is implemented as follows: firstly, the Al-polar AlN layer is etched and removed using an atmosphere containing X2 but not containing BX3, and then, the AlON layer is etched and removed using an atmosphere containing BX3 but not containing X2, where X is a halogen element; Wherein, the silicon-free substrate contains oxygen; the first template contains oxygen; and / or in step S20, the annealing atmosphere includes nitrogen and oxygen, and the volume percentage of oxygen in the annealing atmosphere is not greater than 2%.
2. The preparation method according to claim 1, characterized in that: The thickness of the AlN film is greater than 20 nm; and / or The thickness of the AlN film is less than 100 nm.
3. The preparation method according to claim 1, characterized in that: In step S20, the annealing time is 10 minutes to 24 hours.
4. The preparation method according to claim 1, characterized in that: The first template is also an AlN template. When two AlN templates cover each other, the upper surfaces of the AlN films in the two AlN templates are in contact with each other.
5. The preparation method according to claim 1, characterized in that: The silicon-free substrate is an AlN ceramic substrate or a BN ceramic substrate.
6. The preparation method according to claim 2, characterized in that: The silicon-free substrate is an AlN ceramic substrate or a BN ceramic substrate.
7. The preparation method according to claim 3, characterized in that: The silicon-free substrate is an AlN ceramic substrate or a BN ceramic substrate.
8. The preparation method according to claim 4, characterized in that: The silicon-free substrate is an AlN ceramic substrate or a BN ceramic substrate.
9. The preparation method according to any one of claims 1 to 8, characterized in that: After step S30, the method further includes the following steps: S40`: preserving the AlN template having a single N-polar AlN film in an oxygen-isolated state.
10. The preparation method according to any one of claims 1 to 8, characterized in that: After step S30, the method further includes the following steps: S40: epitaxially growing an AlN layer on the upper surface of the AlN thin film of the AlN template having a single N-polar AlN thin film.
11. The preparation method according to claim 10, characterized in that: After step S30 and before step S40, at least one of the following steps is further included: S301: performing high temperature baking on the AlN template having a single N-polar AlN film; S401: performing nitridation treatment on the upper surface of the AlN film of the AlN template having a single N-polar AlN film.
12. The preparation method according to claim 11, characterized in that: The baking atmosphere of the high-temperature baking contains hydrogen element.