Preparation method of AlN template with high crystallization quality and AlN template

Abstract

The present invention relates to a method for preparing an AlN template with high crystalline quality and an AlN template, belonging to the technical field of AlN template preparation. The method comprises: forming an AlN buffer layer on the front surface of a substrate to obtain a first initial AlN template; performing a cyclic epitaxial growth process on the first initial AlN template to form a second initial AlN template on the front surface of the AlN buffer layer; and performing a cyclic annealing process on the second initial AlN template to obtain a prepared AlN template. By performing the cyclic epitaxial growth process on the first initial AlN template, the prepared AlN template has fewer impurities and defects and lower internal stress; by performing a layer-by-layer in-situ annealing process on the first initial AlN template and a cyclic annealing process on the second initial AlN template, the warpage of the AlN template is reduced, the dislocation phenomenon within the AlN template is reduced, the dislocation density of the AlN template is reduced, and the crystalline quality of the AlN template is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of AlN template preparation, and in particular to a preparation method of an AlN template with high crystallization quality and the AlN template. Background Art

[0002] High-crystalline-quality AlN (aluminum nitride) templates, as substrate materials for epitaxial growth of AlGaN (aluminum gallium nitride)-based deep-ultraviolet LEDs, can effectively reduce the threading dislocation density of AlGaN and increase the radiative recombination efficiency of electrons and holes in the LED structure, thereby significantly improving the reliability, luminous efficiency, and service life of the LED. Therefore, researching and developing high-crystalline-quality AlN templates is of great significance for promoting the development of deep-ultraviolet LED technology. Currently, there are various AlN templates on the market, mainly divided into single-crystal AlN templates and heterogeneous AlN templates. Single-crystal AlN templates are favored for their excellent crystalline quality and low dislocation density, but their high cost and limited supply limit their widespread application. In contrast, heterogeneous AlN templates are less expensive, but due to their relatively poor crystalline quality and performance stability, heterogeneous AlN templates are difficult to meet the manufacturing requirements of high-end LED devices. Dislocation density is one of the important indicators for measuring the crystallization quality of heterogeneous AlN templates. The existence of dislocations not only affects the mechanical and electrical properties of heterogeneous AlN templates, but may also become a gathering place for impurities and defects. Therefore, reducing dislocations is a powerful means to improve the crystallization quality of heterogeneous AlN templates.

[0003] Existing methods for preparing heterogeneous AlN templates usually use hydrogen as a reaction carrier gas to form an AlN buffer layer on the front side of the substrate by magnetron sputtering, then epitaxially grow a first AlN epitaxial layer on the front side of the AlN buffer layer in a low-temperature environment, and then epitaxially grow a second AlN epitaxial layer on the front side of the first AlN epitaxial layer in a high-temperature environment. The first AlN epitaxial layer grown at a low temperature is prone to lattice mismatch with the substrate or the second AlN epitaxial layer grown subsequently at a high temperature. This mismatch can easily lead to dislocations between the first AlN epitaxial layer and the second AlN epitaxial layer. In addition, due to temperature changes, the first AlN epitaxial layer and the second AlN epitaxial layer experience thermal expansion and contraction, which may lead to internal stress accumulation in the finally prepared AlN template, thereby causing defects such as cracks between the first AlN epitaxial layer and the second AlN epitaxial layer.

[0004] Based on this, there is an urgent need for a technology that can prepare AlN templates with high crystalline quality. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a method for preparing an AlN template with high crystalline quality and an AlN template. The technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing an AlN template with high crystalline quality, comprising the following steps:

[0007] S1, placing a substrate in a magnetron sputtering device, performing magnetron sputtering on the front side of the substrate to form an AlN buffer layer on the front side of the substrate to obtain a first initial AlN template;

[0008] S2, performing a first epitaxial growth process on the first initial AlN template to form a first AlN epitaxial layer on the front surface of the AlN buffer layer, and then performing a first in-situ annealing process; wherein the reaction carrier gas introduced into the first epitaxial growth process is hydrogen, and the protective gas introduced into the first in-situ annealing process is hydrogen;

[0009] S3, performing a second epitaxial growth process on the first initial AlN template that has completed the first in-situ annealing process to form a second AlN epitaxial layer on the front surface of the first AlN epitaxial layer, and then performing a second in-situ annealing process; wherein the reaction carrier gas introduced into the second epitaxial growth process is nitrogen, and the protective gas introduced into the second in-situ annealing process is nitrogen;

[0010] S4, repeating S2 and S3 at least once to perform a cyclic epitaxial growth process on the first initial AlN template to form a second initial AlN template on the front surface of the AlN buffer layer;

[0011] S5, performing a first annealing treatment and a first cooling treatment on the second initial AlN template; wherein the protective gas introduced during the first annealing treatment is nitrogen or hydrogen;

[0012] S6, performing a second annealing treatment and a second cooling treatment on the second initial AlN template after the first cooling treatment; wherein the protective gas introduced into the second annealing treatment is hydrogen or nitrogen, and the protective gas introduced into the second annealing treatment is different from the protective gas introduced into the first annealing treatment;

[0013] S7, repeating S5 and S6 at least once to perform cyclic annealing treatment on the second initial AlN template to obtain a prepared AlN template.

[0014] Optionally, when performing the first epitaxial growth process, the step S2 includes:

[0015] The first initial AlN template is placed in an MOCVD furnace, the temperature of the MOCVD furnace is adjusted to 900°C-1400°C, and ammonia with a flow rate of 1-30L / min and trimethylaluminum with a flow rate of 0.001-10L / min are introduced into the MOCVD furnace, and hydrogen with a flow rate of 1-50L / min is introduced as a reaction carrier gas to perform a first epitaxial growth on the front side of the AlN buffer layer, so that a first AlN epitaxial layer is formed on the front side of the AlN buffer layer. The reaction duration of the first epitaxial growth process is 0.1-2h.

[0016] Optionally, when performing the first in-situ annealing treatment, the step S2 includes:

[0017] The temperature of the MOCVD furnace is regulated to be 1000°C-1700°C, and trimethylaluminum with a flow rate of 0.001-5 L / min is introduced into the MOCVD furnace, and then hydrogen with a flow rate of 1-50 L / min is introduced as a protective gas to perform a first in-situ annealing treatment on the first initial AlN template that has completed the first epitaxial growth treatment. The reaction duration of the first in-situ annealing treatment is 0.1-1 hour.

[0018] Optionally, when performing the second epitaxial growth process, the step S3 includes:

[0019] The temperature of the MOCVD furnace is regulated to be 900°C-1400°C, and ammonia gas with a flow rate of 1-30 L / min and trimethylaluminum with a flow rate of 0.001-10 L / min are introduced into the MOCVD furnace, and nitrogen gas with a flow rate of 1-50 L / min is introduced as a reaction carrier gas to perform a second epitaxial growth on the front side of the first AlN epitaxial layer, so that a second AlN epitaxial layer is formed on the front side of the first AlN epitaxial layer. The reaction duration of the second epitaxial growth process is 0.1-2 hours.

[0020] Optionally, when performing the second in-situ annealing treatment, S3 includes:

[0021] The temperature of the MOCVD furnace is regulated to be 1000°C-1700°C, and trimethylaluminum with a flow rate of 0.001-5 L / min is introduced into the MOCVD furnace, and nitrogen with a flow rate of 1-50 L / min is introduced as a protective gas to perform a second in-situ annealing treatment on the first initial AlN template that has completed the second epitaxial growth treatment. The reaction duration of the second in-situ annealing treatment is 0.1-1 h.

[0022] Optionally, when S5 is specifically implemented, it includes:

[0023] S51, regulating the temperature of the MOCVD furnace to 1000° C.-1700° C., introducing trimethylaluminum at a flow rate of 0.001-5 L / min into the MOCVD furnace, and then introducing nitrogen or hydrogen at a flow rate of 1-20 L / min as a protective gas to perform a first annealing treatment on the second initial AlN template. The reaction duration of the first annealing treatment is 0.1-5 hours;

[0024] S52, regulating the temperature of the MOCVD furnace to 500°C-800°C, so as to perform a first cooling treatment on the second initial AlN template that has completed the first annealing treatment.

[0025] Optionally, when S6 is implemented, it includes:

[0026] S61, regulating the temperature of the MOCVD furnace to 1000-1700° C., introducing trimethylaluminum into the MOCVD furnace at a flow rate of 0.001-5 L / min, and again introducing hydrogen or nitrogen at a flow rate of 1-20 L / min as a protective gas, to perform a second annealing treatment on the second initial AlN template that has completed the first cooling treatment, wherein the reaction duration of the second annealing treatment is 0.1-5 hours; wherein the protective gas introduced into the second annealing treatment is different from the protective gas introduced into the first annealing treatment;

[0027] S62, regulating the temperature of the MOCVD furnace to 500°C-800°C, so as to perform a second cooling treatment on the second initial AlN template that has completed the second annealing treatment.

[0028] Optionally, the cyclic epitaxial growth process in S4 includes repeating S2 and S3 1-50 times; and the cyclic annealing process in S7 includes repeating S5 and S6 1-20 times.

[0029] Optionally, the thickness of the AlN buffer layer is 1-100 nm, and the thickness of the AlN template is 430-1000 μm.

[0030] In a second aspect, the present invention provides an AlN template with high crystalline quality, which is prepared by the above-mentioned method for preparing a high crystalline quality AlN template, and includes a substrate, an AlN buffer layer, at least one first AlN epitaxial layer and at least one second AlN epitaxial layer; the number of layers of the first AlN epitaxial layer is the same as the number of layers of the second AlN epitaxial layer.

[0031] All the above optional technical solutions can be combined arbitrarily, and the present invention does not provide detailed descriptions of the structures after each combination.

[0032] By means of the above solution, the beneficial effects of the present invention are as follows:

[0033] By introducing hydrogen as a reaction carrier gas and a protective gas during the first epitaxial growth treatment and the first in-situ annealing treatment of the first initial AlN template, the hydrogen carrier gas epitaxial layer, i.e., the first AlN epitaxial layer, formed has fewer internal impurities and defects; by introducing nitrogen as a reaction carrier gas and a protective gas during the second epitaxial growth treatment and the second in-situ annealing treatment of the first initial AlN template that has completed the first in-situ annealing treatment, the nitrogen carrier gas epitaxial layer, i.e., the second AlN epitaxial layer, formed can inherit the advantages of the hydrogen carrier gas epitaxial layer with fewer impurities and defects, and take advantage of the low stress of the nitrogen carrier gas epitaxial layer.

[0034] In the preparation method of the AlN template with high crystalline quality provided by the present invention, an in-situ annealing treatment is immediately performed after completing an epitaxial growth process. The in-situ annealing treatment can release the internal stress generated in the current AlN epitaxial layer formed by the epitaxial growth process, and can also rearrange and move the atoms in the current AlN epitaxial layer to reduce lattice distortion, thereby reducing impurities and defects in the current AlN epitaxial layer, thereby reducing the internal stress accumulation phenomenon during the growth of the current AlN epitaxial layer and reducing the situation where impurities and defects in the current AlN epitaxial layer are transmitted to the upper AlN epitaxial layer. At the same time, the dislocation phenomenon between two adjacent AlN epitaxial layers is reduced, the dislocation density of the AlN template is reduced, and the crystalline quality of the AlN template is improved. By performing a cyclic annealing process on the second initial AlN template, the overall warpage of the substrate and the formed AlN template is reduced.

[0035] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the preparation process of the present invention;

[0037] Figure 2 Schematic diagram of the timing of preparing the AlN template in the present invention;

[0038] Figure 3 Schematic diagram of the structure of the AlN template in the present invention;

[0039] Figure 4 Schematic diagram of the warpage test results of the AlN template in the present invention;

[0040] Figure 5 Schematic diagram of the roughness test results of the AlN template in the present invention;

[0041] Figure 6 Schematic diagram of the stress state test results of the AlN template in the present invention;

[0042] Figure 7 Schematic diagram of the results of the crystallization quality test of the AlN template in the present invention;

[0043] Figure 8 Schematic diagram of the results of cross-sectional delamination test of the AlN template in the present invention;

[0044] Description of Figure Numbers:

[0045] 1. Substrate; 2. AlN buffer layer; 3. First AlN epitaxial layer; 4. Second AlN epitaxial layer; 5. AlN template. DETAILED DESCRIPTION

[0046] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0047] like Figure 1 and Figure 2 As shown, the present invention provides a method for preparing an AlN template with high crystalline quality, comprising the following steps:

[0048] S1, placing a substrate 1 in a magnetron sputtering device, performing magnetron sputtering treatment on the front side of the substrate 1 to form an AlN buffer layer 2 on the front side of the substrate 1, thereby obtaining a first initial AlN template;

[0049] S2, performing a first epitaxial growth process on the first initial AlN template to form a first AlN epitaxial layer 3 on the front surface of the AlN buffer layer 2, and then performing a first in-situ annealing process; wherein the reaction carrier gas introduced in the first epitaxial growth process is hydrogen, and the protective gas introduced in the first in-situ annealing process is hydrogen;

[0050] S3, performing a second epitaxial growth process on the first initial AlN template that has completed the first in-situ annealing process to form a second AlN epitaxial layer 4 on the front surface of the first AlN epitaxial layer 3, and then performing a second in-situ annealing process; wherein the reaction carrier gas introduced into the second epitaxial growth process is nitrogen, and the protective gas introduced into the second in-situ annealing process is nitrogen;

[0051] S4, repeating S2 and S3 at least once to perform a cyclic epitaxial growth process on the first initial AlN template to form a second initial AlN template on the front surface of the AlN buffer layer 2;

[0052] S5, performing a first annealing treatment and a first cooling treatment on the second initial AlN template; wherein the protective gas introduced during the first annealing treatment is nitrogen or hydrogen;

[0053] S6, performing a second annealing treatment and a second cooling treatment on the second initial AlN template after the first cooling treatment; wherein the protective gas introduced into the second annealing treatment is hydrogen or nitrogen, and the protective gas introduced into the second annealing treatment is different from the protective gas introduced into the first annealing treatment;

[0054] S7 , repeating S5 and S6 at least once to perform cyclic annealing treatment on the second initial AlN template to obtain a prepared AlN template 5 .

[0055] Specifically, the material of the substrate 1 in the present invention can be sapphire, silicon nitride, silicon carbide or silicon wafer.

[0056] By introducing hydrogen as a reaction carrier gas and a protective gas during the first epitaxial growth treatment and the first in-situ annealing treatment of the first initial AlN template, the hydrogen carrier gas epitaxial layer, i.e., the first AlN epitaxial layer 3, formed has fewer internal impurities and defects; by introducing nitrogen as a reaction carrier gas and a protective gas during the second epitaxial growth treatment and the second in-situ annealing treatment of the first initial AlN template that has completed the first in-situ annealing treatment, the nitrogen carrier gas epitaxial layer, i.e., the second AlN epitaxial layer 4, formed can inherit the advantages of the hydrogen carrier gas epitaxial layer with fewer impurities and defects, and give full play to the advantage of the nitrogen carrier gas epitaxial layer with low stress.

[0057] In the preparation method of the high-crystalline quality AlN template provided by the present invention, after completing an epitaxial growth process, an in-situ annealing process is immediately performed, and the in-situ annealing process can release the internal stress generated by the current AlN epitaxial layer formed by the epitaxial growth process, and can also rearrange and move the atoms of the current AlN epitaxial layer to reduce lattice distortion, thereby reducing impurities and defects in the current AlN epitaxial layer, thereby reducing the internal stress accumulation phenomenon during the growth of the current AlN epitaxial layer and reducing the impurities and defects of the current AlN epitaxial layer to the upper AlN epitaxial layer. At the same time, the dislocation phenomenon between the two adjacent AlN epitaxial layers is reduced, the dislocation density of the AlN template 5 is reduced, and the crystal quality of the AlN template 5 is improved; by performing a cyclic annealing process on the second initial AlN template, it is beneficial to reduce the overall warping of the substrate 1 and the formed AlN template 5.

[0058] Optionally, when performing the first epitaxial growth process, the step S2 includes:

[0059] The first initial AlN template is placed in an MOCVD furnace, the temperature of the MOCVD furnace is adjusted to 900°C-1400°C, and ammonia with a flow rate of 1-30L / min and trimethylaluminum with a flow rate of 0.001-10L / min are introduced into the MOCVD furnace, and then hydrogen with a flow rate of 1-50L / min is introduced as a reaction carrier gas to perform the first epitaxial growth on the front side of the AlN buffer layer 2, so that the first AlN epitaxial layer 3 is formed on the front side of the AlN buffer layer 2. The reaction duration of the first epitaxial growth treatment is 0.1-2h.

[0060] In a specific embodiment, if multiple AlN templates 5 are prepared simultaneously in a single process, ammonia, trimethylaluminum, and hydrogen can be introduced into the MOCVD furnace at different flow rates during the first epitaxial growth process for different AlN templates 5. This results in different growth rates and thicknesses of the first AlN epitaxial layer 3 formed on the front surface of the AlN buffer layer 2, ultimately resulting in different internal structures of the first AlN epitaxial layer 3. Therefore, the flow rates of ammonia, trimethylaluminum, and hydrogen introduced into the MOCVD furnace can be adjusted based on the specific conditions of the on-site preparation. The thickness of the first AlN epitaxial layer 3 is 1 nm to 100 nm.

[0061] Optionally, when performing the first in-situ annealing treatment, the step S2 includes:

[0062] The temperature of the MOCVD furnace is regulated to be 1000°C-1700°C, and trimethylaluminum with a flow rate of 0.001-5 L / min is introduced into the MOCVD furnace, and then hydrogen with a flow rate of 1-50 L / min is introduced as a protective gas to perform a first in-situ annealing treatment on the first initial AlN template that has completed the first epitaxial growth treatment. The reaction duration of the first in-situ annealing treatment is 0.1-1 hour.

[0063] Optionally, when performing the second epitaxial growth process, the step S3 includes:

[0064] The temperature of the MOCVD furnace is regulated to 900°C-1400°C, and ammonia with a flow rate of 1-30 L / min and trimethylaluminum with a flow rate of 0.001-10 L / min are introduced into the MOCVD furnace, and nitrogen with a flow rate of 1-50 L / min is introduced as a reaction carrier gas to perform a second epitaxial growth on the front side of the first AlN epitaxial layer 3, so that a second AlN epitaxial layer 4 is formed on the front side of the first AlN epitaxial layer 3. The reaction duration of the second epitaxial growth process is 0.1-2 hours.

[0065] In a specific embodiment, if multiple AlN templates 5 are prepared simultaneously in a single process, ammonia, trimethylaluminum, and nitrogen can be introduced into the MOCVD furnace at different flow rates for different AlN templates 5 during the second epitaxial growth process. This results in different growth rates and thicknesses of the second AlN epitaxial layer 4 formed on the front surface of the first AlN epitaxial layer 3, ultimately resulting in different internal structures of the second AlN epitaxial layer 4. Therefore, the flow rates of ammonia, trimethylaluminum, and nitrogen introduced into the MOCVD furnace can be adjusted according to the specific conditions of the on-site preparation. The thickness of the second AlN epitaxial layer 4 is 1 nm to 100 nm.

[0066] It should be noted that during the first in-situ annealing treatment and the second in-situ annealing treatment, the first AlN epitaxial layer 3 and the second AlN epitaxial layer 4 are both in a suspended growth state, so that the first in-situ annealing treatment and the second in-situ annealing treatment are only performed on the first AlN epitaxial layer 3 and the second AlN epitaxial layer 4 that have been grown, so as to achieve the best annealing effect.

[0067] Optionally, when performing the second in-situ annealing treatment, S3 includes:

[0068] The temperature of the MOCVD furnace is regulated to be 1000°C-1700°C, and trimethylaluminum with a flow rate of 0.001-5 L / min is introduced into the MOCVD furnace, and nitrogen with a flow rate of 1-50 L / min is introduced as a protective gas to perform a second in-situ annealing treatment on the first initial AlN template that has completed the second epitaxial growth treatment. The reaction duration of the second in-situ annealing treatment is 0.1-1 h.

[0069] During the first epitaxial growth process and the second epitaxial growth process, trimethylaluminum metal source, hydrogen or trimethylaluminum metal source, and nitrogen are introduced simultaneously, so that a layer of trimethylaluminum metal source is attached to the surface of the formed first AlN epitaxial layer 3 and the second AlN epitaxial layer 4, blocking the atomic migration inside the first AlN epitaxial layer 3 and the second AlN epitaxial layer 4, enhancing the stability of the first AlN epitaxial layer 3 and the second AlN epitaxial layer 4, thereby avoiding the etching of the first AlN epitaxial layer 3 and the second AlN epitaxial layer 4 during the first in-situ annealing process and the second in-situ annealing process, thereby ensuring a smooth AlN epitaxial layer surface.

[0070] Optionally, when S5 is specifically implemented, it includes:

[0071] S51, regulating the temperature of the MOCVD furnace to 1000° C.-1700° C., introducing trimethylaluminum at a flow rate of 0.001-5 L / min into the MOCVD furnace, and then introducing nitrogen or hydrogen at a flow rate of 1-20 L / min as a protective gas to perform a first annealing treatment on the second initial AlN template. The reaction duration of the first annealing treatment is 0.1-5 hours;

[0072] S52, regulating the temperature of the MOCVD furnace to 500°C-800°C, so as to perform a first cooling treatment on the second initial AlN template that has completed the first annealing treatment.

[0073] Optionally, when S6 is implemented, it includes:

[0074] S61, regulating the temperature of the MOCVD furnace to 1000-1700° C., introducing trimethylaluminum into the MOCVD furnace at a flow rate of 0.001-5 L / min, and again introducing hydrogen or nitrogen at a flow rate of 1-20 L / min as a protective gas, to perform a second annealing treatment on the second initial AlN template that has completed the first cooling treatment, wherein the reaction duration of the second annealing treatment is 0.1-5 hours; wherein the protective gas introduced into the second annealing treatment is different from the protective gas introduced into the first annealing treatment;

[0075] S62, regulating the temperature of the MOCVD furnace to 500°C-800°C, so as to perform a second cooling treatment on the second initial AlN template that has completed the second annealing treatment.

[0076] In a specific embodiment, in the present invention, the protective gas introduced into the MOCVD furnace during the first annealing process may be nitrogen, and the protective gas introduced into the MOCVD furnace during the second annealing process may be hydrogen. Of course, the protective gas introduced into the MOCVD furnace during the first annealing process may also be hydrogen, and the protective gas introduced into the MOCVD furnace during the second annealing process may be nitrogen, as long as the protective gases introduced during the first annealing process and the second annealing process are different. It is also necessary to ensure that the protective gas introduced during the first annealing process is different from the reactive carrier gas introduced during the final in-situ annealing process in the cyclic epitaxial growth process.

[0077] The preparation method provided by the present invention realizes repeated heating of the second initial AlN template by repeatedly performing a first annealing treatment, a first cooling treatment, a second annealing treatment, and a second cooling treatment, thereby promoting atomic rearrangement within the multilayer AlN epitaxial layer in the second initial AlN template, thereby improving the internal stress of the second initial AlN template, reducing the dislocation phenomenon between the multilayer AlN epitaxial layers, and reducing the dislocation density within the multilayer AlN epitaxial layer.

[0078] In the present invention, the first in-situ annealing treatment, the second in-situ annealing treatment, and the annealing temperatures during the first annealing treatment and the second annealing treatment are all higher than the temperatures during the first epitaxial growth treatment and the second epitaxial growth treatment.

[0079] It should be noted that, in a specific implementation, a temperature difference between the temperature of the MOCVD furnace during the first annealing process and the temperature during the second annealing process can be controlled, and the temperature difference can be 0°C-100°C. If the temperature difference between the first annealing process and the second annealing process is large, the lattice parameter within the second initial AlN template may change, resulting in a lattice mismatch between the second initial AlN template and the substrate 1. Therefore, a smaller temperature difference helps maintain the continuity and matching of the lattice between the substrate 1 and the second initial AlN template, reducing internal stress and defects in the second initial AlN template. In addition, an excessively large temperature difference can easily cause thermal expansion or contraction within the second initial AlN template, resulting in the accumulation of internal stress. A smaller temperature difference can avoid thermal expansion or contraction, thereby reducing the internal stress of the second initial AlN template and preventing defects such as cracks in the second initial AlN template.

[0080] During the first in-situ annealing treatment, the second in-situ annealing treatment, the first annealing treatment, and the second annealing treatment, a certain flow of trimethylaluminum must be introduced when the temperature of the MOCVD furnace exceeds 1000°C to prevent atomic migration within the multilayer AlN epitaxial layer in the high temperature environment, thereby preventing etching, and further ensuring the quality and integrity of the multilayer AlN epitaxial layer.

[0081] Optionally, the cyclic epitaxial growth process in S4 includes repeating S2 and S3 1-50 times; and the cyclic annealing process in S7 includes repeating S5 and S6 1-20 times.

[0082] Specifically, the present invention does not limit the number of times S2 and S3 are repeated, and it is sufficient to ensure that the number of cycles of S2 and S3 is the same; the present invention does not limit the number of times S5 and S6 are repeated, and it is sufficient to ensure that the number of cycles of S5 and S6 is the same.

[0083] like Figure 2 As shown, Figure 2 Where n is the number of times S2 and S3 are repeated in the present invention, and m is the number of times S5 and S6 are repeated in the present invention.

[0084] It should be noted that, in the process of repeating S2, ammonia, trimethylaluminum and hydrogen can be introduced into the MOCVD furnace at different flow rates, so that the speed of forming the multi-layer first AlN epitaxial layer 3 on the front side of the AlN buffer layer 2 is different, and the thickness of the formed multi-layer first AlN epitaxial layer 3 is different; in the process of repeating S3, ammonia, trimethylaluminum and nitrogen can be introduced into the MOCVD furnace at different flow rates, so that the speed of forming the second AlN epitaxial layer 4 on the front side of each layer of the first AlN epitaxial layer 3 is different, and the thickness of the formed multi-layer second AlN epitaxial layer 4 is different.

[0085] Optionally, the thickness of the AlN buffer layer 2 is 1-100 nm, and the thickness of the AlN template 5 is 430-1000 μm. Preferably, the thickness of the AlN buffer layer 2 is 1-50 nm, and the thickness of the AlN template 5 is 430 μm.

[0086] The thickness of the AlN template 5 obtained by the preparation method provided by the present invention is the same as that of the AlN template prepared in the prior art. Therefore, while having the same thickness as the AlN template prepared in the prior art, the AlN template 5 prepared by the present invention has the advantages of fewer impurities, fewer defects, and fewer dislocations.

[0087] The present invention also provides an AlN template with high crystalline quality, wherein the AlN template with high crystalline quality is prepared by the above-mentioned method for preparing an AlN template with high crystalline quality, such as Figure 3 As shown, it includes a substrate 1, an AlN buffer layer 2, at least one first AlN epitaxial layer 3 and at least one second AlN epitaxial layer 4; the number of layers of the first AlN epitaxial layer 3 is the same as the number of layers of the second AlN epitaxial layer 4.

[0088] According to the content of the preparation method of the above-mentioned AlN template, S2 is performed once to obtain a first AlN epitaxial layer 3; S3 is performed once to obtain a second AlN epitaxial layer 4. Therefore, the number of layers of the first AlN epitaxial layer 3 and the second AlN epitaxial layer 4 is related to the number of times S2 and S3 are repeated.

[0089] To verify the beneficial effects of the method for preparing a high-crystalline quality AlN template provided by the present invention, three examples are set up to prepare AlN templates 5. Multiple tests are performed on the AlN templates 5 prepared in the three examples, and the test results are compared. Example 1 is the preparation method provided by the present invention. The AlN template 5 obtained is the first AlN template. The specific preparation process of the first AlN template is as follows:

[0090] S1a, placing the substrate 1 in a magnetron sputtering device, and forming an AlN buffer layer on the front surface of the substrate 1 by magnetron sputtering to obtain a first initial AlN template; wherein the sputtering temperature is 500° C.-700° C., the sputtering time is 0.5 min-20 min, and the thickness of the AlN buffer layer 2 is 1 nm-50 nm;

[0091] S2a, placing the first initial AlN template into an MOCVD furnace, adjusting the temperature of the MOCVD furnace to 1000° C.-1200° C., introducing ammonia gas at a flow rate of 1-10 L / min and trimethylaluminum at a flow rate of 5-10 L / min into the MOCVD furnace, and simultaneously introducing hydrogen gas at a flow rate of 30-50 L / min as a reaction carrier gas, to perform a first epitaxial growth on the front surface of the AlN buffer layer 2, so that a first AlN epitaxial layer 3 is formed on the front surface of the AlN buffer layer 2. The reaction duration of the first epitaxial growth process is 0.1-0.5 h, and the thickness of the first AlN epitaxial layer 3 is 1-50 nm;

[0092] S3a, regulating the temperature of the MOCVD furnace to 1400-1700° C., introducing hydrogen at a flow rate of 30-50 L / min as a protective gas into the MOCVD furnace, and simultaneously introducing trimethylaluminum at a flow rate of 2-5 L / min to perform a first in-situ annealing treatment on the first initial AlN template that has completed the first epitaxial growth treatment. The reaction duration of the first in-situ annealing treatment is 0.1-0.5 h;

[0093] S4a, regulating the MOCVD temperature to drop to 1000° C.-1200° C., introducing ammonia gas at a flow rate of 1-10 L / min and trimethylaluminum at a flow rate of 5-10 L / min into the MOCVD furnace, and simultaneously introducing nitrogen gas at a flow rate of 30-50 L / min as a reaction carrier gas, to perform a second epitaxial growth on the front surface of the first AlN epitaxial layer 3, so that a second AlN epitaxial layer 4 is formed on the front surface of the first AlN epitaxial layer 3. The reaction duration of the second epitaxial growth process is 0.1-0.5 h, and the thickness of the second AlN epitaxial layer 4 is 1-50 nm;

[0094] S5a, regulating the temperature of the MOCVD furnace to 1400-1700° C., introducing nitrogen at a flow rate of 30-50 L / min as a protective gas into the MOCVD furnace, and simultaneously introducing trimethylaluminum at a flow rate of 2-5 L / min to perform a second in-situ annealing treatment on the first initial AlN template that has completed the second epitaxial growth treatment. The reaction duration of the second in-situ annealing treatment is 0.1-0.5 h;

[0095] S6a, repeating steps S2a-S5a 20-40 times to perform a cyclic epitaxial growth process on the first initial AlN template to form a second initial AlN template on the front surface of the AlN buffer layer 2;

[0096] S7a, regulating the temperature of the MOCVD furnace to 1500° C.-1700° C., introducing nitrogen or hydrogen at a flow rate of 10-20 L / min into the MOCVD furnace as a protective gas, and simultaneously introducing trimethylaluminum at a flow rate of 2-5 L / min to perform a first annealing treatment on the second initial AlN template. The reaction duration of the first annealing treatment is 1-3 hours;

[0097] S8a, regulating the temperature of the MOCVD furnace to drop to 700° C.-800° C. to perform a first cooling treatment on the second initial AlN template that has completed the first annealing treatment;

[0098] S9a, regulating the temperature of the MOCVD furnace to 1500° C.-1700° C., introducing hydrogen or nitrogen at a flow rate of 10-20 L / min into the MOCVD furnace as a protective gas, and simultaneously introducing trimethylaluminum at a flow rate of 2-5 L / min to perform a second annealing treatment on the second initial AlN template that has completed the first cooling treatment, wherein the reaction duration of the second annealing treatment is 1-3 hours; wherein the protective gas introduced into the second annealing treatment is different from the protective gas introduced into the first annealing treatment;

[0099] S10a, regulating the temperature of the MOCVD furnace to drop to 700° C.-800° C. to perform a second cooling treatment on the second initial AlN template that has completed the second annealing treatment;

[0100] S11a, repeating steps S7a-S10a 1-10 times to perform an out-of-cycle annealing treatment on the second initial AlN template to obtain a prepared AlN template 5; wherein the reaction duration of the cyclic annealing treatment is 1-3 hours.

[0101] The difference between Example 2 and Example 1 is that S7a-S11a is missing, that is, the cyclic annealing treatment described in S7a-S11a is missing, and the AlN template 5 obtained in Example 2 is the second AlN template; the difference between Example 3 and Example 1 is that S3a and S5a are missing, that is, the first in-situ annealing treatment and the second in-situ annealing treatment described in S3a and S5a are missing, and the AlN template 5 obtained in Example 3 is the third AlN template.

[0102] The AlN templates 5 prepared by the above three embodiments were subjected to a warpage test (BowX test), and the test results of the AlN templates 5 prepared by the three embodiments were compared. The comparison results are shown in FIG. Figure 4As shown in the figure, the average warpage of the first AlN template is 19.97 μm, the average warpage of the second AlN template is 28.05 μm, and the average warpage of the third AlN template is 26.98 μm; the standard warpage value of the first AlN template is 0.60 μm, the standard warpage value of the second AlN template is 2.98 μm, and the standard warpage value of the third AlN template is 0.99 μm; it can be concluded that the first AlN template obtained by the preparation method provided by the present invention has a smaller warpage and is flatter overall.

[0103] The roughness test (AFM test) of the AlN templates 5 prepared by the above three embodiments was performed using an atomic force microscope, and the test results of the AlN templates 5 prepared by the three embodiments were compared. The comparison results are shown in FIG. Figure 5 As shown in the figure, the average roughness of the first AlN template is 0.33 nm, the average roughness of the second AlN template is 1.06 nm, and the average roughness of the third AlN template is 1.96 nm; the standard roughness value of the first AlN template is 0.06 nm, the standard roughness value of the second AlN template is 0.58 nm, and the standard roughness value of the third AlN template is 0.20 nm; thus, it can be concluded that the roughness of the first AlN template obtained by the preparation method provided by the present invention is smaller and the surface is smoother.

[0104] The stress state test (Raman test) of the AlN template 5 prepared by the above three embodiments was performed using a Raman spectrometer, and the test results of the AlN template 5 prepared by the three embodiments were compared. The comparison results are shown in FIG. Figure 6 As shown: The average stress of the first AlN template is 660.25cm -1 The average stress of the second AlN template is 659.63 cm -1 The average stress of the third AlN template is 659.94 cm -1 ; The stress standard value of the first AlN template is 1.00cm -1 The stress standard value of the second AlN template is 0.94cm -1 The stress standard value of the third AlN template is 0.94cm -1 ; It can be seen that there is no significant difference in the stress state of the AlN template 5 prepared in the three embodiments.

[0105] The AlN templates 5 prepared by the above three embodiments were tested for crystal quality (XRC102FWHM test) by X-ray diffractometer, and the test results of the AlN templates 5 prepared by the three embodiments were compared. Figure 7As shown in the figure: the average crystallization quality of the first AlN template is 211.4 arcsec, the average crystallization quality of the second AlN template is 338.8 arcsec, and the average crystallization quality of the third AlN template is 244.4 arcsec; the standard crystallization quality value of the first AlN template is 7.24 arcsec, the standard crystallization quality value of the second AlN template is 9.63 arcsec, and the standard crystallization quality value of the third AlN template is 9.71 arcsec; it can be concluded that the crystallization quality of the first AlN template obtained by the preparation method provided by the present invention is the best.

[0106] The AlN templates 5 prepared by the above three embodiments were subjected to cross-sectional layering tests (cross-sectional SEM tests) using a scanning electron microscope, and the test results of the AlN templates 5 prepared by the three embodiments were compared. The comparison results are shown in FIG. Figure 8 As shown, the AlN templates 5 prepared in the three embodiments have uniform morphology, smooth cross-section and no delamination phenomenon. Therefore, it can be concluded that the AlN templates 5 prepared in the three embodiments do not experience delamination during the preparation process.

[0107] According to the comparison results of the above multiple tests, Example 1 performed layer-by-layer in-situ annealing and cyclic annealing during the preparation process, Example 2 performed layer-by-layer in-situ annealing during the preparation process, and Example 3 performed cyclic annealing during the preparation process. There is no significant difference in the internal stress of the AlN templates 5 prepared by the three examples, and there is no delamination phenomenon in the cross-section of the AlN templates 5 prepared by the three examples. It can be concluded that performing layer-by-layer in-situ annealing on the layered grown AlN epitaxial layer or performing cyclic annealing on the second initial AlN template can reduce the internal stress of the prepared AlN template 5 and eliminate the delamination phenomenon.

[0108] Compared with Examples 2 and 3, in Example 1, during the process of preparing the first AlN template, the layered grown AlN epitaxial layer is subjected to in-situ annealing treatment layer by layer, so that the first initial AlN template has a low impurity content and a low internal stress, and the dislocation phenomenon between the two adjacent AlN epitaxial layers is reduced; in Example 1, during the process of preparing the first AlN template, the second initial AlN template is also subjected to cyclic annealing treatment, which further reduces the dislocation phenomenon of the prepared first AlN template and the dislocation density inside the first AlN template; and because trimethylaluminum is introduced during the layer-by-layer in-situ annealing treatment and the cyclic annealing treatment, the defects on the surface of the first AlN template are further reduced, so that the surface of the first AlN template is smooth at the atomic level, and the warping and roughness of the first AlN template are further reduced, thereby greatly improving the crystallization quality of the first AlN template.

[0109] In summary, the preparation method of the high crystalline quality AlN template provided by the present invention is to carry out layered growth of multiple AlN epitaxial layers on the surface of the substrate 1 and perform in-situ annealing treatment layer by layer, and introduce different reaction carrier gases during the process of in-situ annealing treatment layer by layer, so that the formed multi-layer AlN epitaxial layer combines the advantages of hydrogen carrier gas epitaxial layer and nitrogen carrier gas epitaxial layer, so that the prepared AlN template 5 has fewer impurities, fewer defects, and less internal stress, and also improves the crystallization quality.

[0110] The introduction of trimethylaluminum during the layer-by-layer in-situ annealing process can inhibit the migration of atoms within the multi-layer AlN epitaxial layer under high temperature, thereby preventing the multi-layer AlN epitaxial layer from being etched, thereby ensuring that the surface of the AlN template 5 is smooth at the atomic level, which is beneficial to the growth of the subsequent epitaxial layer and can also reduce the dislocation phenomenon between two adjacent AlN epitaxial layers.

[0111] By performing a cyclic annealing treatment on the second initial AlN template and introducing different protective gases, the dislocation phenomenon between the two adjacent AlN epitaxial layers can be further reduced, and the warping of the prepared AlN template 5 can be further reduced, and the impurities and defects of the prepared AlN template 5 can be reduced, ultimately making the surface of the AlN template 5 smoother and the crystal quality significantly improved.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an AlN template with high crystalline quality, characterized in that: The following steps are involved: S1, placing a substrate (1) in a magnetron sputtering device, performing magnetron sputtering treatment on the front side of the substrate (1) to form an AlN buffer layer (2) on the front side of the substrate (1), and obtaining a first initial AlN template; S2, performing a first epitaxial growth process on the first initial AlN template to form a first AlN epitaxial layer (3) on the front surface of the AlN buffer layer (2), and then performing a first in-situ annealing process; wherein the reaction carrier gas introduced in the first epitaxial growth process is hydrogen, and the protective gas introduced in the first in-situ annealing process is hydrogen; S3, performing a second epitaxial growth process on the first initial AlN template that has completed the first in-situ annealing process to form a second AlN epitaxial layer (4) on the front surface of the first AlN epitaxial layer (3), and then performing a second in-situ annealing process; wherein the reaction carrier gas introduced into the second epitaxial growth process is nitrogen, and the protective gas introduced into the second in-situ annealing process is nitrogen; S4, repeating S2 and S3 at least once to perform a cyclic epitaxial growth process on the first initial AlN template to form a second initial AlN template on the front surface of the AlN buffer layer (2); S5, performing a first annealing treatment and a first cooling treatment on the second initial AlN template; wherein the protective gas introduced during the first annealing treatment is nitrogen or hydrogen; S6, performing a second annealing treatment and a second cooling treatment on the second initial AlN template after the first cooling treatment; wherein the protective gas introduced into the second annealing treatment is hydrogen or nitrogen, and the protective gas introduced into the second annealing treatment is different from the protective gas introduced into the first annealing treatment; S7, repeating S5 and S6 at least once to perform cyclic annealing treatment on the second initial AlN template to obtain a prepared AlN template (5).

2. The method for preparing a high-crystalline quality AlN template according to claim 1, characterized in that: When performing the first epitaxial growth process, the step S2 includes: The first initial AlN template is placed in an MOCVD furnace, the temperature of the MOCVD furnace is adjusted to 900° C.-1400° C., ammonia with a flow rate of 1-30 L / min and trimethylaluminum with a flow rate of 0.001-10 L / min are introduced into the MOCVD furnace, and hydrogen with a flow rate of 1-50 L / min is introduced as a reaction carrier gas to perform a first epitaxial growth on the front surface of the AlN buffer layer (2), so that a first AlN epitaxial layer (3) is formed on the front surface of the AlN buffer layer (2), and the reaction duration of the first epitaxial growth process is 0.1-2 hours.

3. The method for preparing a high-crystalline quality AlN template according to claim 2, characterized in that: When performing the first in-situ annealing process, S2 includes: The temperature of the MOCVD furnace is regulated to be 1000°C-1700°C, and trimethylaluminum with a flow rate of 0.001-5 L / min is introduced into the MOCVD furnace, and then hydrogen with a flow rate of 1-50 L / min is introduced as a protective gas to perform a first in-situ annealing treatment on the first initial AlN template that has completed the first epitaxial growth treatment. The reaction duration of the first in-situ annealing treatment is 0.1-1 hour.

4. The method for preparing a high-crystalline quality AlN template according to claim 1, wherein: When performing the second epitaxial growth process, the step S3 includes: The temperature of the MOCVD furnace is regulated to be 900° C.-1400° C., and ammonia gas with a flow rate of 1-30 L / min and trimethylaluminum with a flow rate of 0.001-10 L / min are introduced into the MOCVD furnace, and nitrogen gas with a flow rate of 1-50 L / min is introduced as a reaction carrier gas, so as to perform a second epitaxial growth on the front surface of the first AlN epitaxial layer (3), so that a second AlN epitaxial layer (4) is formed on the front surface of the first AlN epitaxial layer (3), and the reaction duration of the second epitaxial growth process is 0.1-2 hours.

5. The method for preparing an AlN template with high crystalline quality according to claim 4, characterized in that: When performing the second in-situ annealing process, S3 includes: The temperature of the MOCVD furnace is regulated to be 1000°C-1700°C, and trimethylaluminum with a flow rate of 0.001-5 L / min is introduced into the MOCVD furnace, and nitrogen with a flow rate of 1-50 L / min is introduced as a protective gas to perform a second in-situ annealing treatment on the first initial AlN template that has completed the second epitaxial growth treatment. The reaction duration of the second in-situ annealing treatment is 0.1-1 h.

6. The method for preparing an AlN template with high crystalline quality according to claim 1, wherein: When S5 is specifically implemented, it includes: S51, regulating the temperature of the MOCVD furnace to 1000° C.-1700° C., introducing trimethylaluminum at a flow rate of 0.001-5 L / min into the MOCVD furnace, and then introducing nitrogen or hydrogen at a flow rate of 1-20 L / min as a protective gas to perform a first annealing treatment on the second initial AlN template. The reaction duration of the first annealing treatment is 0.1-5 hours; S52, regulating the temperature of the MOCVD furnace to 500°C-800°C, so as to perform a first cooling treatment on the second initial AlN template that has completed the first annealing treatment.

7. The method for preparing a high-crystalline quality AlN template according to claim 6, characterized in that: When S6 is specifically implemented, it includes: S61, regulating the temperature of the MOCVD furnace to 1000-1700° C., introducing trimethylaluminum into the MOCVD furnace at a flow rate of 0.001-5 L / min, and again introducing hydrogen or nitrogen at a flow rate of 1-20 L / min as a protective gas, to perform a second annealing treatment on the second initial AlN template that has completed the first cooling treatment, wherein the reaction duration of the second annealing treatment is 0.1-5 hours; wherein the protective gas introduced into the second annealing treatment is different from the protective gas introduced into the first annealing treatment; S62, regulating the temperature of the MOCVD furnace to 500°C-800°C, so as to perform a second cooling treatment on the second initial AlN template that has completed the second annealing treatment.

8. The method for preparing an AlN template with high crystalline quality according to claim 1, wherein: The cyclic epitaxial growth process in S4 includes repeating S2 and S3 1-50 times; The cyclic annealing treatment in S7 includes repeating S5 and S6 1-20 times.

9. The method for preparing an AlN template with high crystalline quality according to claim 1, characterized in that: The thickness of the AlN buffer layer (2) is 1-100 nm, and the thickness of the AlN template (5) is 430-1000 μm.

10. An AlN template with high crystalline quality, characterized in that: The AlN template with high crystalline quality is prepared by the method for preparing an AlN template with high crystalline quality according to any one of claims 1 to 9, comprising: A substrate (1), an AlN buffer layer (2), at least one first AlN epitaxial layer (3), and at least one second AlN epitaxial layer (4); The number of layers of the first AlN epitaxial layer (3) is the same as the number of layers of the second AlN epitaxial layer (4).

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