Aluminum nitride epitaxial structure, preparation method thereof and semiconductor device

Abstract

The invention discloses an aluminum nitride epitaxial structure and a preparation method thereof, the aluminum nitride epitaxial structure comprises a heterogeneous substrate and an aluminum nitride buffer layer grown on the heterogeneous substrate, and the aluminum nitride buffer layer is provided with a lattice transition layer which is epitaxially grown and contains a first group III nitride; a coarsening layer which is epitaxially grown and comprises a second III-group nitride is arranged on the lattice transition layer; a three-dimensional aluminum nitride layer and a two-dimensional aluminum nitride layer which are sequentially stacked and grown are arranged on the coarsening layer; wherein the first III-group nitride and the second III-group nitride both contain an In element; in the process of adjusting the temperature in the growth cavity to the temperature required for growing the three-dimensional aluminum nitride layer, at least part of In elements are separated out, so that the coarsening layer has a rough surface. By sequentially growing the buffer layer, the lattice transition layer, the coarsening layer, the three-dimensional aluminum nitride layer and the two-dimensional aluminum nitride layer on the substrate, dislocation, especially blade type dislocation, can be reduced or even eliminated, and the crystal quality of the aluminum nitride epitaxial structure is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor material preparation, and particularly to an aluminum nitride epitaxial structure, a preparation method thereof, and a semiconductor device including the aluminum nitride epitaxial structure. Background Art

[0002] Aluminum nitride (AlN) is a material that has attracted much attention in the semiconductor field, standing out with its extremely wide bandgap and large exciton binding energy. Its bandgap width is as high as 6.2 eV, and it belongs to a direct bandgap semiconductor. In addition, aluminum nitride also exhibits many excellent physical properties, such as high breakdown field strength, thermal conductivity, and resistivity, etc. These characteristics have continuously attracted wide attention in the semiconductor field.

[0003] The aluminum nitride template generally grows on a hetero-substrate (such as sapphire). One of the methods to obtain high-quality aluminum nitride materials in the prior art is to improve the quality of the aluminum nitride buffer layer sputtered on the hetero-substrate to enhance the crystal quality of the subsequent growth. However, due to the very flat surface of the sputtered aluminum nitride and the very stable nature of the aluminum nitride material itself, it is impossible to roughen it by methods such as annealing. Therefore, the aluminum nitride grown in this way is often directly two-dimensional growth. Although the screw dislocations are few, due to the absence of the island coalescence process, there are many edge dislocations, resulting in the still not high crystal quality of the overall aluminum nitride material. Summary of the Invention

[0004] The purpose of the present invention is to provide an aluminum nitride epitaxial structure and a preparation method thereof, which are used to solve the problem that there are many edge dislocations caused by the existing solution of improving the quality of the aluminum nitride buffer layer sputtered on the hetero-substrate, resulting in the still not high crystal quality of the overall aluminum nitride material. The present application can reduce or even eliminate dislocations, especially the existence of edge dislocations, and improve the crystal quality of the aluminum nitride epitaxial structure by sequentially growing a buffer layer, a lattice transition layer, a roughening layer, a three-dimensional aluminum nitride layer, and a two-dimensional aluminum nitride layer on the hetero-substrate.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] In the first aspect of the present invention, there is provided an aluminum nitride epitaxial structure, including a hetero-substrate and an aluminum nitride buffer layer grown on the hetero-substrate, and a lattice transition layer containing a first group III nitride is epitaxially grown on the aluminum nitride buffer layer;

[0007] A roughening layer containing a second group III nitride is epitaxially grown on the lattice transition layer;

[0008] A three-dimensional aluminum nitride layer and a two-dimensional aluminum nitride layer are sequentially stacked and grown on the roughening layer;

[0009] Among them, both the first group-III nitride and the second group-III nitride contain In element; during the process of adjusting the temperature in the growth chamber to the temperature required for growing the three-dimensional aluminum nitride layer, the precipitation of at least part of the In element makes the coarsening layer have a rough surface.

[0010] Compared with the prior art, the beneficial effects of the present application are as follows: By providing a lattice transition layer containing a first group-III nitride on the aluminum nitride buffer layer epitaxially grown on a hetero-substrate, it can serve as a lattice transition for the subsequent grown AlN material and introduce the In element in the first group-III nitride; then, a coarsening layer containing a second group-III nitride is provided on the lattice transition layer. Due to the paving of the previous lattice transition layer, during the process of growing the three-dimensional aluminum nitride layer, the In element will be precipitated, and the surface of the coarsening layer will become rough. The rough surface provides a three-dimensional island growth mode for the AlN material grown on the three-dimensional aluminum nitride layer; finally, during the process of growing the two-dimensional aluminum nitride layer, AlN will form a flattened three-dimensional aluminum nitride layer, and finally, an AlN material with a flat surface and high crystal quality, that is, the two-dimensional aluminum nitride layer, can be obtained on the three-dimensional aluminum nitride layer. The aluminum nitride epitaxial structure of the present application reduces and even eliminates the presence of dislocations, especially edge dislocations, and improves the crystal quality.

[0011] In some possible implementation manners of the first aspect, the component ratio of the In element in the first group-III nitride is 10% - 15%; and / or, the component ratio of the In element in the second group-III nitride is 15% - 25%.

[0012] In some possible implementation manners of the first aspect, the lattice transition layer includes a plurality of first periodic structures stacked in sequence, and each first periodic structure includes an AlInN layer and a first GaN layer stacked; the starting layer of the lattice transition layer is an AlInN layer, and the terminating layer of the lattice transition layer is a first GaN layer; and / or,

[0013] The coarsening layer includes a plurality of second periodic structures stacked in sequence, and each second periodic structure includes an InGaN layer and a second GaN layer stacked; the starting layer of the coarsening layer is an InGaN layer, and the terminating layer of the coarsening layer is a second GaN layer.

[0014] In some possible implementation manners of the first aspect, the thickness of the aluminum nitride buffer layer is 10 - 100 nm;

[0015] and / or, the thickness of the lattice transition layer is 50 - 200 nm;

[0016] and / or, the thickness of the coarsening layer is 10 - 100 nm; the thickness of the three-dimensional aluminum nitride layer is 0.2 - 0.5 μm; the thickness of the two-dimensional aluminum nitride layer is 1 - 2 μm;

[0017] And / or, the thickness of the AlInN layer is 2 - 5 nm; the thickness of the first GaN layer is 3 - 10 nm, and the number of the first periodic structures is 10 - 20;

[0018] And / or, the thickness of the InGaN layer is 2 - 4 nm; the thickness of the second GaN layer is 3 - 10 nm, and the number of the second periodic structures is 1 - 10.

[0019] In a second aspect of the present invention, a method for preparing an aluminum nitride epitaxial structure is provided, including:

[0020] Providing a hetero-substrate;

[0021] Successively laminating and growing an aluminum nitride buffer layer, a lattice transition layer containing a first group III nitride, a roughening layer containing a second group III nitride, a three-dimensional aluminum nitride layer, and a two-dimensional aluminum nitride layer on the hetero-substrate to obtain the aluminum nitride epitaxial structure;

[0022] Wherein, both the first group III nitride and the second group III nitride contain In element; during the process of adjusting the temperature in the growth chamber to the temperature required for growing the three-dimensional aluminum nitride layer, the precipitation of at least part of the In element makes the roughening layer have a rough surface.

[0023] In some possible embodiments of the second aspect, the component ratio of In element in the first group III nitride is 10% - 15%; and / or, the component ratio of In element in the second group III nitride is 15% - 25%;

[0024] And / or, the growth temperature of the roughening layer is lower than the growth temperature of the three-dimensional aluminum nitride layer;

[0025] And / or, the growth temperature of the two-dimensional aluminum nitride layer is higher than the growth temperature of the three-dimensional aluminum nitride layer;

[0026] And / or, the V / III ratio for growing the two-dimensional aluminum nitride layer is lower than the V / III ratio for growing the three-dimensional aluminum nitride layer;

[0027] And / or, the growth pressure of the three-dimensional aluminum nitride layer is higher than the growth pressure of the two-dimensional aluminum nitride layer.

[0028] In some possible embodiments of the second aspect, growing the lattice transition layer includes:

[0029] Forming a plurality of successively stacked first periodic structures on the aluminum nitride buffer layer to obtain a lattice transition layer with a thickness of 50 - 200 nm;

[0030] Wherein, the growth of each first periodic structure includes:

[0031] Under the conditions that the growth pressure is 500 - 760 torr, the growth temperature is 700 - 800 °C, and the flow rate ratio of growth source TMIn to growth source TMAl is 1:1 - 5:1, an AlInN layer with a thickness of 2 - 5 nm is grown;

[0032] Under the conditions that the growth pressure is 500 - 760 torr, the growth temperature is 900 - 1000 °C, and the flow rate of growth source TMGa is 100 - 1000 μmol / min, a first GaN layer with a thickness of 3 - 10 nm is grown on the AlInN layer.

[0033] In some possible embodiments of the second aspect, growing the roughened layer includes:

[0034] Forming a plurality of second periodic structures stacked in sequence on the lattice transition layer to obtain a roughened layer with a thickness of 10 - 100 nm;

[0035] Among them, the growth of each second periodic structure includes:

[0036] Under the conditions that the growth pressure is 300 - 500 torr, the growth temperature is 600 - 700 °C, and the flow rate ratio of growth source TMIn to growth source TMGa is 5:1 - 1:1, an InGaN layer with a thickness of 2 - 4 nm is grown;

[0037] Under the conditions that the growth pressure is 300 - 500 torr, the growth temperature is 800 - 900 °C, and the flow rate of growth source TMGa is 100 - 1000 μmol / min, a second GaN layer with a thickness of 3 - 10 nm is grown on the InGaN layer.

[0038] In some possible embodiments of the second aspect, the growth of the aluminum nitride buffer layer includes: under the conditions that the magnetron sputtering pressure is 10 -7 - 10 -9 torr, the magnetron sputtering power is 10 - 30 kW, and the magnetron sputtering time is 30 s - 3 min, an aluminum nitride buffer layer with a thickness of 10 - 100 nm is grown on the hetero - substrate; and / or,

[0039] The growth of the three - dimensional aluminum nitride layer includes: under the conditions that the growth pressure is 200 - 400 torr, the growth temperature is 1150 - 1250 °C, and the V / III ratio is 500 - 1000, a three - dimensional aluminum nitride layer with a thickness of 0.2 - 0.5 μm is grown on the roughened layer; and / or,

[0040] The growth of the two-dimensional aluminum nitride layer includes: growing a two-dimensional aluminum nitride layer with a thickness of 1-2 μm on the three-dimensional aluminum nitride layer under the conditions of a growth pressure of 25-75 torr, a growth temperature of 1250-1350 °C, and a V / III ratio of 100-200.

[0041] In a third aspect of the present invention, a semiconductor device is provided, which includes the aluminum nitride epitaxial structure as described above.

[0042] Beneficial effects: Different from traditional preparation methods, after sputtering an aluminum nitride layer buffer layer on a heterogeneous substrate in the present invention, the growth of a lattice transition layer containing a first group III nitride is first carried out. The lattice transition layer serves as a lattice transition for the AlN material, and the purpose is to introduce the In element in the first group III nitride. The multiple first-period structures of AlInN and GaN (i.e., the periodic alternating growth structure of the AlInN layer / the first GaN layer) increase the stability for lattice-matched growth within their respective growth temperature ranges; then, the growth of a roughening layer containing a second group III nitride is carried out on the lattice transition layer, that is, the growth of multiple second-period structures of InGaN and GaN (i.e., the periodic alternating growth structure of the InGaN layer / the second GaN layer). Due to the previous paving of AlInN / GaN, the In component of InGaN in the roughening layer can reach 15%-25%; then, during the heating process to the growth of the two-dimensional aluminum nitride layer, the In element will be precipitated, and the surface of the roughening layer will become rough. The rough surface provides a three-dimensional island growth mode for the AlN material for the growth of the three-dimensional aluminum nitride layer; finally, during the growth of the two-dimensional aluminum nitride layer, due to the further increase in temperature and the further decrease in the V / III ratio, AlN will form a flattened two-dimensional aluminum nitride layer, and finally, an AlN material with a flat surface and high crystal quality can be formed on the three-dimensional aluminum nitride layer, that is, the two-dimensional aluminum nitride layer. Description of the Drawings

[0043] Figure 1 It is a schematic structural diagram of the aluminum nitride epitaxial structure provided by this application;

[0044] Figure 2 It is a schematic structural diagram of the lattice transition layer in the aluminum nitride epitaxial structure provided by this application;

[0045] Figure 3 It is a schematic structural diagram of the roughening layer in the aluminum nitride epitaxial structure provided by this application;

[0046] Figure 4 It is a flow chart of the preparation method of the aluminum nitride epitaxial structure provided by this application;

[0047] Figure 5 It is a TEM image of the aluminum nitride epitaxial structure in Example 1;

[0048] Figure 6 It is the TEM image of the aluminum nitride epitaxial structure in Example 2;

[0049] Figure 7 It is the TEM image of the aluminum nitride epitaxial structure in Example 3;

[0050] Figure 8 It is the TEM image of the aluminum nitride epitaxial structure in the comparative example;

[0051] Figure 9 It is the TEM image of the aluminum nitride epitaxial structure in Example 4;

[0052] Figure 10 It is the TEM image of the aluminum nitride epitaxial structure in Example 5;

[0053] Figure 11 It is the TEM image of the aluminum nitride epitaxial structure in Example 6.

[0054] Note: TEM (Transmission Electron Microscope ， transmission electron microscope), which is used for the metrology and material characterization of sub-nanometer-sized device features in semiconductor technology, Figures 5 - 7 and the TEM images of 9 - 11 are obtained at a resolution of 500 nm; Figure 8 The TEM image of is obtained at a resolution of 1 μm.

[0055] In the figure, 1, hetero-substrate; 2, aluminum nitride buffer layer; 3, lattice transition layer; 4, roughened layer; 5, three-dimensional aluminum nitride layer; 6, two-dimensional aluminum nitride layer; 31, first-period structure; 41, second-period structure; 311, AlInN layer; 312, first GaN layer; 411, InGaN layer; 412, second GaN layer. Detailed implementation manners

[0056] Now, the exemplary embodiments will be described more comprehensively with reference to the accompanying drawings. However, the exemplary embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the present invention is more comprehensive and complete, and the concept of the exemplary embodiments is fully conveyed to those skilled in the art. Identical reference numerals in the figures denote identical or similar structures, and thus their repeated description will be omitted.

[0057] In the present invention, the words expressing position and direction are described by taking the accompanying drawings as examples, but can be changed according to needs, and all changes made are included in the protection scope of the present invention.

[0058] It is worth noting that the V / III ratio in the present invention is the molar flow ratio of group V elements to group III elements.

[0059] Combined with the attached Figure 1 As shown, in the first aspect of the present application, an aluminum nitride epitaxial structure is provided. The aluminum nitride epitaxial structure includes a hetero-substrate 1 and an aluminum nitride buffer layer 2 grown on the hetero-substrate 1. An epitaxially grown lattice transition layer 3 containing a first group III nitride is provided on the aluminum nitride buffer layer 2.

[0060] For the hetero-substrate 1, the present application has no special limitation, and any suitable hetero-substrate 1 in the art can be used to implement the technical solution of the present application. In some embodiments of the present application, the substrate used may be selected from a sapphire substrate, a silicon carbide substrate or a metal substrate, preferably a sapphire substrate. The said metal substrate may be a high-temperature resistant metal such as molybdenum or titanium.

[0061] For the aluminum nitride buffer layer 2, since the surface of the hetero-substrate 1 may not be flat enough or contaminated, the sputtered aluminum nitride buffer layer 2 can provide a cleaner and smoother surface, which is beneficial to subsequent epitaxial growth.

[0062] It should be noted that the aluminum nitride buffer layer 2 can also play a role in stress buffering. Due to the different thermal expansion coefficients of AlN and the substrate material, thermal stress will be generated during the cooling process, resulting in film cracking or warping. The stress accumulation caused by thermal mismatch can be reduced through the aluminum nitride buffer layer 2, and the mechanical stability of the subsequently grown aluminum nitride epitaxial structure can be improved.

[0063] It should be further noted that since the lattice constant of AlN is different from that of the substrate material such as sapphire (Al2O3), direct growth may also lead to a high defect density. The aluminum nitride buffer layer 2 can effectively relieve lattice mismatch and reduce the defect density, thereby improving the crystal quality.

[0064] The thickness of the aluminum nitride buffer layer 2 is 10 - 100 nm, for example: 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm. The aluminum nitride buffer layer 2 in this thickness range has a better effect and higher crystal quality.

[0065] It should be noted that the first group III nitride contains In element. By introducing In into the lattice transition layer 3, the purpose is to perform stress relaxation for the subsequently grown coarsening layer (i.e., the second-period structure of InGaN / GaN). Incorporating In with a large atomic radius in AlN can develop the epitaxial structure towards the tensile stress direction that is more likely to incorporate In, so as to increase the stability for the lattice matching growth of the second-period structure of InGaN / GaN with a higher In composition in the later stage.

[0066] On the lattice transition layer 3, there is a coarsening layer 4 of epitaxially grown second group-III nitride. On the coarsening layer 4, there are a three-dimensional aluminum nitride (3D AlN) layer 5 and a two-dimensional aluminum nitride (2D AlN) layer 6 that are sequentially grown in a stacked manner.

[0067] It should be noted that the second group-III nitride also contains In element. During the process of adjusting the temperature in the growth chamber to the temperature required for growing the three-dimensional aluminum nitride layer 5, due to the bedding of In element in the lattice transition layer 3, the content of In element in the coarsening layer 4 will increase, and at least part of the In element will precipitate, making the coarsening layer 4 have a rough surface. The rough surface provides a three-dimensional island growth mode for the AlN material grown on the three-dimensional aluminum nitride layer 5. Since the lattice constants of the two-dimensional aluminum nitride layers are exactly the same Growing the two-dimensional aluminum nitride layer on the three-dimensional aluminum nitride layer can eliminate defects such as dislocations and stacking faults caused by lattice mismatch in traditional heteroepitaxy (such as growing AlN on sapphire). And because the thermal expansion coefficients of the three-dimensional aluminum nitride layer and the two-dimensional aluminum nitride layer are the same (both are 4.2×10 -6 / K), it is possible to avoid interface cracking or warping caused by thermal mismatch, thereby forming an AlN material with a flat surface and high crystal quality.

[0068] Furthermore, as a preferred embodiment of the present application, the component ratio of In element in the first group-III nitride is 10% - 15%, for example: 10%, 11%, 12%, 13%, 14% or 15%. The reason is that when the In component is less than 18%, it is more matched with the AlN lattice. Since the lower layer is the AlN buffer layer, for better lattice transition and stress release for the later high-In component, the proportion of In element in the first group-III nitride should not be too high; and / or, the component ratio of In element in the second group-III nitride is 15% - 25%, for example: 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25%. Preferably, the component ratio of In element in the second group-III nitride is 18% - 25%. The reason is that when the In component is greater than or equal to 18%, it is more matched with the GaN lattice, thus gradually transitioning from AlN to the (In)GaN material system. Only in this way is it possible to successfully grow high-In component InGaN, that is, the crystal quality of InGaN / GaN is better and the component can also be improved more. At the same time, the high-In component in the second group-III nitride will be used as the precipitated component to regulate the coarsening conditions later. Therefore, the gradient growth of In element in the lattice transition layer 3 and the coarsening layer 4 is very crucial. Only when the transition is good can the In component of the coarsening layer 4 be made high and there will be more room for regulating the coarsening.

[0069] Furthermore, as a preferred embodiment of the present application, in combination with the attached Figure 1 WithFigure 2 As shown, the lattice transition layer 3 includes a plurality of first periodic structures 31 stacked in sequence. Each first periodic structure 31 includes an AlInN layer 311 and a first GaN layer 312 arranged in layers. The starting layer of the lattice transition layer 3 is the AlInN layer 311, and the terminating layer of the lattice transition layer is the first GaN layer 312. Among them, the thickness of the lattice transition layer 3 is 50 - 200 nm, for example: 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, 175 nm or 200 nm.

[0070] The function of the AlInN layer 311 is to serve as a lattice transition between the AlN buffer layer and the InGaN material system. Since the quality of simply growing the AlInN layer 311 as the lattice transition layer 3 is not ideal, the first GaN layer 312 is continuously grown on the AlInN layer 311. By adopting the first periodic structure of AlInN / GaN, high-quality growth with a relatively large thickness can be ensured, playing a better role in lattice transition.

[0071] It should be noted that the thickness of the AlInN layer 311 is 2 - 5 nm, for example: 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm; the thickness of the first GaN layer 312 is 3 - 10 nm, for example: 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm. Since the quality of AlInN is poor, GaN material is needed to improve the quality after growing to a certain thickness. The AlInN 311 layer with a thickness range of 2 - 5 nm and the first GaN layer 312 with a thickness range of 3 - 10 nm can form an AlInN / GaN superlattice structure (i.e., the first periodic structure). Moreover, the thickness difference between AlInN and GaN also brings different In components in the superlattice structure. Within this thickness range, a better combination of the AlInN / GaN superlattice structure with crystal quality can be sought.

[0072] Furthermore, the number n of the first periodic structures 31 is 10 - 20, for example: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20. The number of the first periodic structures 31 is related to the total thickness of the AlInN / GaN superlattice structure. Among them, the change in thickness causes the effects of lattice transition and stress relaxation. The first periodic structures 31 in the range of 10 - 20 can significantly increase the In component of InGaN in the second III-group nitride.

[0073] Furthermore, as a preferred implementation mode of the present application, in combination with the attached Figure 1 And Figure 3As shown, the roughening layer 4 includes a plurality of second periodic structures 41 stacked in sequence. Each second periodic structure 41 includes an InGaN layer 411 and a second GaN layer 412 arranged in layers. The starting layer of the roughening layer 4 is the InGaN layer 411, and the terminating layer of the roughening layer 4 is the second GaN layer 412. Among them, the thickness of the roughening layer 4 is 10 - 100 nm, for example: 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm.

[0074] The InGaN layer 411 can provide necessary conditions for the subsequent In precipitation behavior to roughen the surface of the epitaxial layer. The higher the In composition, the greater the precipitation redundancy, making the regulation range of the subsequent AlN three-dimensional growth wider. The second GaN layer is related to the InGaN layer with a higher In composition and the InGaN layer 411 with a lower crystal quality, providing subsequent quality compensation for InGaN.

[0075] It should be noted that the thickness of the InGaN layer 411 is 2 - 4 nm, for example: 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm, 3 nm, 3.2 nm, 3.4 nm, 3.6 nm, 3.8 nm or 4 nm; the thickness of the second GaN layer 412 is 3 - 10 nm, for example: 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm. In the InGaN layer with a thickness range of 2 - 4 nm, as the thickness increases, the In composition in the second periodic structure of InGaN / GaN is higher; however, as the thickness increases, the crystal quality will decrease. To ensure the crystal quality, the second GaN layer 412 with a thickness range of 3 - 10 nm is used to compensate the quality of the InGaN layer 411.

[0076] Furthermore, the number m of the second periodic structures 41 is 1 - 10, for example: 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. The number of the second periodic structures 41 determines the total thickness. The second periodic structures 42 in the range of 1 - 10 can ensure the strength of the entire In precipitation structure and improve the size of the longitudinal nucleation of the subsequent 3D AlN growth.

[0077] Furthermore, the thickness of the three-dimensional aluminum nitride layer 5 is 0.2 - 0.5 μm, for example: 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm or 0.5 μm; the thickness of the two-dimensional aluminum nitride layer 6 is 1.0 - 2.0 μm, for example: 1 μm, 1.25 μm, 1.5 μm, 1.75 μm or 2 μm.

[0078] The thickness range of the three-dimensional aluminum nitride layer 5 is lower than that of the two-dimensional aluminum nitride layer 6, which can not only enable the AlN material of the three-dimensional aluminum nitride layer 5 to achieve three-dimensional longitudinal growth, but also promote the complete merger of the AlN material of the later two-dimensional aluminum nitride layer 6 with the three-dimensional aluminum nitride layer 5 and the annihilation of dislocations, forming a step-flow growth mode. Due to the complete merger, dislocations, especially the existence of edge dislocations, can be reduced or even eliminated, improving the crystal quality of the aluminum nitride epitaxial structure.

[0079] In the second aspect of the present application, a method for preparing the above-mentioned aluminum nitride epitaxial structure is provided. As shown in the accompanying Figure 4 figures, it includes the following steps S1 - step S2.

[0080] Step S1: Provide a hetero-substrate.

[0081] As described above, the hetero-substrate is preferably a sapphire substrate.

[0082] Step S2: Sequentially stack and grow an aluminum nitride buffer layer, a lattice transition layer containing a first group III nitride, a roughening layer containing a second group III nitride, a three-dimensional aluminum nitride layer, and a two-dimensional aluminum nitride layer on the hetero-substrate to obtain an aluminum nitride epitaxial structure.

[0083] It should be noted in detail that step S2 includes steps S21 - step S25.

[0084] Step S21: Grow an aluminum nitride buffer layer with a thickness of 10 - 100 nm on the hetero-substrate under the conditions that the magnetron sputtering pressure is 10 -7 ~10 -9 torr, the magnetron sputtering power is 10 - 30 kW, and the magnetron sputtering time is 30 s - 3 min.

[0085] The magnetron sputtering pressure can be 10 -7 torr, 2.5×10 -7 torr, 5×10 -7 torr, 7.5×10 -7 torr, 10 - 8 torr, 2.5×10 -8 torr, 5×10 -8 torr, 7.5×10 -8 torr or 10 -9 torr, the magnetron sputtering power can be 10 kW, 12.5 kW, 15 kW, 17.5 kW, 20 kW, 22.5 kW, 25 kW, 27.5 kW or 30 kW, and the magnetron sputtering time can be 30 s, 1 min, 1.5 min, 2 min, 2.5 min or 3 min.

[0086] The aluminum nitride buffer layer grown under these conditions has the characteristics of a denser film, higher flatness, and better crystal quality.

[0087] Step S22: Form a plurality of the first periodic structures stacked in sequence on the aluminum nitride buffer layer to obtain a lattice transition layer with a thickness of 50 - 200 nm.

[0088] The thickness of the lattice transition layer can be 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, 175 nm, or 200 nm. It should be noted that the first group-III nitride contains In element, and the component ratio of In element in the first group-III nitride is 10% - 15%. Under this In element ratio, the lattice transition layer has a better stress release effect, laying a foundation for the growth of InGaN with a high In component in the coarsening layer of the second group-III nitride.

[0089] Further, as a preferred embodiment of the present application, the growth of each first periodic structure includes Step S221 - Step S222.

[0090] Step S221: Grow an AlInN layer with a thickness of 2 - 5 nm under the conditions of a growth pressure of 500 - 760 torr, a growth temperature of 700 - 800 °C, and a flow rate ratio of growth source TMIn to growth source TMAl of 1:1 - 5:1.

[0091] The growth pressure of the AlInN layer can be 500 torr, 530 torr, 560 torr, 590 torr, 620 torr, 650 torr, 690 torr, 720 torr, or 760 torr; the growth temperature of the AlInN layer can be 700 °C, 710 °C, 720 °C, 730 °C, 740 °C, 750 °C, 760 °C, 770 °C, 780 °C, 790 °C, or 800 °C; the flow rate ratio of TMIn to TMAl can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, or 5:1.

[0092] The AlInN layer grown under these conditions has the characteristics that In components are more likely to enter and the surface roughness is smaller.

[0093] Step S222: Grow a first GaN layer with a thickness of 3 - 10 nm on the AlInN layer under the conditions of a growth pressure of 500 - 760 torr, a growth temperature of 900 - 1000 °C, and a flow rate of growth source TMGa of 100 - 1000 μmol / min.

[0094] The growth pressure of the first GaN layer can be 500 torr, 530 torr, 560 torr, 590 torr, 620 torr, 650 torr, 690 torr, 720 torr or 760 torr; the growth temperature of the first GaN layer can be 900 °C, 910 °C, 920 °C, 930 °C, 940 °C, 950 °C, 960 °C, 970 °C, 980 °C, 990 °C or 1000 °C; the flow rate of TMGa can be 100 μmol / min, 200 μmol / min, 300 μmol / min, 400 μmol / min, 500 μmol / min, 600 μmol / min, 700 μmol / min, 800 μmol / min, 900 μmol / min or 1000 μmol / min.

[0095] The first GaN layer grown under these conditions has the characteristics of higher crystal quality and better surface flatness.

[0096] Step S23: Form a plurality of second-period structures stacked in sequence on the lattice transition layer to obtain a roughened layer with a thickness of 10 - 100 nm.

[0097] The thickness of the roughened layer can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0098] It should be noted that the second group-III nitride also contains In element, and the component ratio of In element in the second group-III nitride is 15% - 25%. The roughened layer under this In element ratio has a higher incorporation efficiency of In with higher component and a relatively high crystal quality of InGaN.

[0099] The roughened layer at this thickness has the function of not affecting the overall crystal quality of the later AlN thick film and being repairable for three-dimensional growth.

[0100] Furthermore, as a preferred embodiment of the present application, the growth of each of the second-period structures includes step S231 - step S232.

[0101] Step S231: Grow an InGaN layer with a thickness of 2 - 4 nm under the conditions that the growth pressure is 300 - 500 torr, the growth temperature is 600 - 700 °C, and the flow rate ratio of the growth source TMIn to the growth source TMGa is 5:1 - 1:1.

[0102] The growth pressure of the InGaN layer can be 300 to 500 torr, for example: 300 torr, 325 torr, 350 torr, 375 torr, 400 torr, 425 torr, 450 torr, 475 torr or 500 torr; the flow rate ratio of TMIn to TMGa can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1.

[0103] The InGaN layer grown under these conditions has the characteristics of better In incorporation efficiency and a relatively flat surface.

[0104] Step S232: Grow a second GaN layer with a thickness of 3 to 10 nm on the InGaN layer under the conditions that the growth pressure is 300 to 500 torr, the growth temperature is 800 to 900 °C, and the flow rate of the growth source TMGa is 100 to 1000 μmol / min.

[0105] The growth pressure of the second GaN layer can be 300 to 500 torr, for example: 300 torr, 325 torr, 350 torr, 375 torr, 400 torr, 425 torr, 450 torr, 475 torr or 500 torr; the growth temperature of the second GaN layer can be 800 to 900 °C, for example: 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, 860 °C, 870 °C, 880 °C, 890 °C or 900 °C; the flow rate of TMGa is 100 μmol / min, 200 μmol / min, 300 μmol / min, 400 μmol / min, 500 μmol / min, 600 μmol / min, 700 μmol / min, 800 μmol / min, 900 μmol / min or 1000 μmol / min.

[0106] The second GaN layer grown under these conditions has the characteristic of improving the overall crystal quality of the InGaN / GaN structure.

[0107] Step S24: Grow a three-dimensional aluminum nitride layer with a thickness of 0.2 to 0.5 μm on the roughened layer under the conditions that the growth pressure is 200 to 400 torr, the growth temperature is 1150 to 1250 °C, and the V / III ratio is 500 to 1000.

[0108] The growth pressure of the three-dimensional aluminum nitride layer can be 200 - 400 torr, such as: 200 torr, 225 torr, 250 torr, 275 torr, 300 torr, 325 torr, 350 torr, 375 torr or 400 torr; the growth temperature of the three-dimensional aluminum nitride layer can be 1150 - 1250 °C, such as: 1150 °C, 1160 °C, 1170 °C, 1180 °C, 1190 °C, 1200 °C, 1210 °C, 1220 °C, 1230 °C, 1240 °C or 1250 °C; the V / III ratio is 500 - 1000, such as: 500, 550, 600, 650, 700, 750, 800, 850, 900, 950 or 1000.

[0109] The three-dimensional aluminum nitride layer grown under these conditions has the characteristics of reducing the nucleation density, reducing the coalescence interface, and reducing the edge dislocation density.

[0110] Furthermore, the inventors discovered through in-depth research that when the growth temperature of the coarsening layer is lower than that of the three-dimensional aluminum nitride layer, during the process of adjusting the temperature in the growth chamber to the temperature required for growing the three-dimensional aluminum nitride layer, the precipitation of at least part of the In element makes the coarsening layer have a rough surface. The rough surface provides a three-dimensional island growth mode for the grown AlN material, and thus forms a three-dimensional aluminum nitride layer, forcing the growth mode of AlN to change from two-dimensional lateral growth to three-dimensional longitudinal growth.

[0111] It should be further noted that after the coarsening layer is grown, with the increase in temperature and the increase in duration in the reaction chamber, the coarsening of the coarsening layer can be enhanced, reducing the nucleation density of the crystal and thus reducing the generation of edge dislocations.

[0112] Step S25: Grow a two-dimensional aluminum nitride layer with a thickness of 1 - 2 μm on the three-dimensional aluminum nitride layer under the conditions of a growth pressure of 25 - 75 torr, a growth temperature of 1250 - 1350 °C, and a V / III ratio of 100 - 200.

[0113] The growth pressure of the two-dimensional aluminum nitride layer can be 25 to 75 torr, for example: 25 torr, 30 torr, 35 torr, 40 torr, 45 torr, 50 torr, 55 torr, 60 torr, 65 torr, 70 torr or 75 torr; the growth temperature of the two-dimensional aluminum nitride layer can be 1250 to 1350 °C, for example: 1250 °C, 1260 °C, 1270 °C, 1280 °C, 1290 °C, 1300 °C, 1310 °C, 1320 °C, 1330 °C, 1340 °C or 1350 °C; the V / III ratio is 100 to 200, for example: 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200.

[0114] Under these conditions, the lateral coalescence growth of the two-dimensional aluminum nitride layer is faster, which is more beneficial for the island surface of the three-dimensional aluminum nitride layer to recover flat.

[0115] Furthermore, through in-depth research and exploration, the inventors found that when the growth pressure of the three-dimensional aluminum nitride layer is greater than that of the two-dimensional aluminum nitride layer, the growth temperature of the two-dimensional aluminum nitride layer is greater than that of the three-dimensional aluminum nitride layer, and the V / III ratio for growing the two-dimensional aluminum nitride layer is less than the V / III ratio for growing the three-dimensional aluminum nitride layer, in the same reaction chamber, due to the further increase in growth temperature, the further decrease in V / III ratio and growth pressure, AlN will flatten the three-dimensional aluminum nitride layer, enabling the surface of the three-dimensional aluminum nitride layer to obtain an atomic-level step-flow morphology, providing an ideal nucleation substrate for the two-dimensional aluminum nitride layer, and well promoting the coalescence growth of the AlN materials in the two-dimensional aluminum nitride layer and the three-dimensional aluminum nitride layer, thereby forming an AlN material with a flat surface and high crystal quality, which can significantly reduce the generation of screw dislocations and reduce the density of edge dislocation growth.

[0116] It should be noted in particular that since the internal coarsening of the coarsening layer will be filled by the AlN material grown subsequently, a high-quality aluminum nitride epitaxial structure can be obtained without peeling.

[0117] In the third aspect of the present application, a semiconductor device is provided, and the semiconductor device includes the above-mentioned aluminum nitride epitaxial structure. The semiconductor device using the aluminum nitride epitaxial structure has characteristics such as high breakdown field strength and high breakdown voltage.

[0118] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0119] It should be noted that for those without specific conditions indicated in the following examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without the manufacturer indicated, they are all conventional products that can be obtained through commercial purchase.

[0120] Example 1

[0121] A method for preparing an aluminum nitride epitaxial structure is provided, including the following steps S1 - step S2.

[0122] Step S1: Provide a hetero-substrate.

[0123] The hetero-substrate is a sapphire substrate.

[0124] Step S2: Sequentially stack-grow an aluminum nitride buffer layer, a lattice transition layer containing a first group III nitride, a roughening layer containing a second group III nitride, a three-dimensional aluminum nitride layer, and a two-dimensional aluminum nitride layer on the hetero-substrate to obtain an aluminum nitride epitaxial structure.

[0125] Step S2 includes steps S21 - step S25.

[0126] Step S21: Grow an aluminum nitride buffer layer with a thickness of 10 nm on the hetero-substrate under the conditions that the magnetron sputtering pressure is 10 -7 torr, the magnetron sputtering power is 10 kW, and the magnetron sputtering time is 30 s.

[0127] Step S22: Form 10 successively stacked first-period structures on the aluminum nitride buffer layer to obtain a lattice transition layer with a thickness of 50 nm.

[0128] It should be noted that the first group III nitride contains In element, and the component proportion of In element in the first group III nitride is 10%.

[0129] The growth of each first-period structure includes steps S221 - step S222.

[0130] Step S221: Grow an AlInN layer with a thickness of 2 nm under the conditions that the growth pressure is 500 torr, the growth temperature is 700 °C, and the flow ratio of the growth source TMIn to the growth source TMAl is 1:1.

[0131] Step S222: Grow a first GaN layer with a thickness of 3 nm on the AlInN layer under the conditions that the growth pressure is 500 torr, the growth temperature is 900 °C, and the flow rate of the growth source TMGa is 100 μmol / min.

[0132] Step S23: Form 2 successively stacked second-period structures on the lattice transition layer to obtain a roughening layer with a thickness of 10 nm.

[0133] It should be noted that the second group III nitride also contains In element, and the component ratio of In element in the second group III nitride is 15%.

[0134] The growth of each second-period structure includes Step S231 - Step S232.

[0135] Step S231: Grow an InGaN layer with a thickness of 2 nm under the conditions that the growth pressure is 300 torr, the growth temperature is 600 °C, and the flow rate ratio of the growth source TMIn to the growth source TMGa is 1:1.

[0136] Step S232: Grow a second GaN layer with a thickness of 3 nm on the InGaN layer under the conditions that the growth pressure is 300 torr, the growth temperature is 800 °C, and the flow rate of the growth source TMGa is 100 μmol / min.

[0137] Step S24: Grow a three-dimensional aluminum nitride layer with a thickness of 0.2 μm on the roughened layer under the conditions that the growth pressure is 200 torr, the growth temperature is 1150 °C, and the V / III ratio is 500.

[0138] Step S25: Grow a two-dimensional aluminum nitride layer with a thickness of 1 μm on the three-dimensional aluminum nitride layer under the conditions that the growth pressure is 25 torr, the growth temperature is 1250 °C, and the V / III ratio is 100, to obtain an aluminum nitride epitaxial structure.

[0139] It should be especially noted that since the internal roughening of the roughened layer will be filled by the subsequently grown AlN material, a high-quality aluminum nitride epitaxial structure can be obtained without peeling.

[0140] Example 2

[0141] Provide a preparation method of an aluminum nitride epitaxial structure, including the following steps S1 - Step S2.

[0142] Step S1: Provide a hetero-substrate.

[0143] The hetero-substrate is a sapphire substrate.

[0144] Step S2: Sequentially stack and grow an aluminum nitride buffer layer, a lattice transition layer containing a first group III nitride, a roughened layer containing a second group III nitride, a three-dimensional aluminum nitride layer, and a two-dimensional aluminum nitride layer on the hetero-substrate to obtain an aluminum nitride epitaxial structure.

[0145] Step S2 includes Step S21 - Step S25.

[0146] Step S21: At a magnetron sputtering pressure of 10 -8Under the conditions of a pressure of torr, a magnetron sputtering power of 20 kW, and a magnetron sputtering time of 1.5 min, an aluminum nitride buffer layer with a thickness of 60 nm was grown on a heterogeneous substrate.

[0147] Step S22: Form 15 successively stacked first-period structures on the aluminum nitride buffer layer to obtain a lattice transition layer with a thickness of 150 nm.

[0148] It should be noted that the first group-III nitride contains In element, and the component ratio of In element in the first group-III nitride is 13%.

[0149] The growth of each first-period structure includes Step S221 - Step S222.

[0150] Step S221: Grow an AlInN layer with a thickness of 3 nm under the conditions of a growth pressure of 620 torr, a growth temperature of 750 °C, and a flow rate ratio of growth source TMIn to growth source TMAl of 3:1.

[0151] Step S222: Grow a first GaN layer with a thickness of 7 nm on the AlInN layer under the conditions of a growth pressure of 620 torr, a growth temperature of 950 °C, and a flow rate of growth source TMGa of 500 μmol / min.

[0152] Step S23: Form 6 successively stacked second-period structures on the lattice transition layer to obtain a roughened layer with a thickness of 60 nm.

[0153] It should be noted that the second group-III nitride also contains In element, and the component ratio of In element in the second group-III nitride is 20%.

[0154] The growth of each second-period structure includes Step S231 - Step S232.

[0155] Step S231: Grow an InGaN layer with a thickness of 3 nm under the conditions of a growth pressure of 400 torr, a growth temperature of 650 °C, and a flow rate ratio of growth source TMIn to growth source TMGa of 3:1.

[0156] Step S232: Grow a second GaN layer with a thickness of 7 nm on the InGaN layer under the conditions of a growth pressure of 400 torr, a growth temperature of 850 °C, and a flow rate of growth source TMGa of 600 μmol / min.

[0157] Step S24: Grow a three-dimensional aluminum nitride layer with a thickness of 0.35 μm on the roughened layer under the conditions of a growth pressure of 300 torr, a growth temperature of 1200 °C, and a V / III ratio of 750.

[0158] Step S25: Grow a two-dimensional aluminum nitride layer with a thickness of 1.5 μm on the three-dimensional aluminum nitride layer under the conditions of a growth pressure of 50 torr, a growth temperature of 1300 °C, and a V / III ratio of 150 to obtain an aluminum nitride epitaxial structure.

[0159] It should be particularly noted that since the internal roughening of the roughening layer will be filled by the subsequently grown AlN material, a high-quality aluminum nitride epitaxial structure can be obtained without peeling.

[0160] Example 3

[0161] Provide a preparation method of an aluminum nitride epitaxial structure, including the following steps S1 - step S2.

[0162] Step S1: Provide a hetero-substrate.

[0163] The hetero-substrate is a sapphire substrate.

[0164] Step S2: Sequentially stack and grow an aluminum nitride buffer layer, a lattice transition layer containing a first group III nitride, a roughening layer containing a second group III nitride, a three-dimensional aluminum nitride layer, and a two-dimensional aluminum nitride layer on the hetero-substrate to obtain an aluminum nitride epitaxial structure.

[0165] Step S2 includes steps S21 - step S25.

[0166] Step S21: Grow an aluminum nitride buffer layer with a thickness of 100 nm on the hetero-substrate under the conditions of a magnetron sputtering pressure of 10 -9 torr, a magnetron sputtering power of 30 kW, and a magnetron sputtering time of 3 min.

[0167] Step S22: Form 12 sequentially stacked first-period structures on the aluminum nitride buffer layer to obtain a lattice transition layer with a thickness of 180 nm.

[0168] It should be noted that the first group III nitride contains In element, and the component ratio of In element in the first group III nitride is 15%.

[0169] The growth of each first-period structure includes steps S221 - step S222.

[0170] Step S221: Grow an AlInN layer with a thickness of 5 nm under the conditions of a growth pressure of 760 torr, a growth temperature of 800 °C, and a flow rate ratio of growth source TMIn to growth source TMAl of 5:1.

[0171] Step S222: Grow a first GaN layer with a thickness of 10 nm on the AlInN layer under the conditions of a growth pressure of 760 torr, a growth temperature of 1000 °C, and a flow rate of growth source TMGa of 1000 μmol / min.

[0172] Step S23: Form seven successively stacked second-period structures on the lattice transition layer to obtain a roughened layer with a thickness of 98 nm.

[0173] It should be noted that the second group-III nitride also contains In element, and the component ratio of In element in the second group-III nitride is 25%.

[0174] The growth of each second-period structure includes Step S231 - Step S232.

[0175] Step S231: Grow an InGaN layer with a thickness of 4 nm under the conditions of a growth pressure of 500 torr, a growth temperature of 700 °C, and a flow ratio of growth source TMIn to growth source TMGa of 5:1.

[0176] Step S232: Grow a second GaN layer with a thickness of 10 nm on the InGaN layer under the conditions of a growth pressure of 500 torr, a growth temperature of 900 °C, and a flow rate of growth source TMGa of 1000 μmol / min.

[0177] Step S24: Grow a three-dimensional aluminum nitride layer with a thickness of 0.5 μm on the roughened layer under the conditions of a growth pressure of 400 torr, a growth temperature of 1250 °C, and a V / III ratio of 1000.

[0178] Step S25: Grow a two-dimensional aluminum nitride layer with a thickness of 2 μm on the three-dimensional aluminum nitride layer under the conditions of a growth pressure of 75 torr, a growth temperature of 1350 °C, and a V / III ratio of 200 to obtain an aluminum nitride epitaxial structure.

[0179] It should be particularly noted that since the internal roughening of the roughened layer will be filled by the subsequently grown AlN material, a high-quality aluminum nitride epitaxial structure can be obtained without peeling.

[0180] Example 4

[0181] The difference from Example 1 is: Step S25: The growth temperature is 1150 °C; others are the same and will not be elaborated here.

[0182] Example 5

[0183] The difference from Example 1 is: Step S25: The V / III ratio is 300; others are the same and will not be elaborated here.

[0184] Example 6

[0185] The difference from Example 1 is: Step S25: The growth pressure is 300 torr; others are the same and will not be elaborated here.

[0186] Comparative Example

[0187] A method for preparing an aluminum nitride epitaxial structure is provided, including the following steps S1 - S2.

[0188] Step S1: Provide a hetero-substrate.

[0189] The hetero-substrate is a sapphire substrate.

[0190] Step S2: Sequentially stack-grow an aluminum nitride buffer layer and a two-dimensional aluminum nitride layer on the hetero-substrate to obtain an aluminum nitride epitaxial structure.

[0191] Step S2 includes steps S21 - S23.

[0192] Step S21: Grow an aluminum nitride buffer layer with a thickness of 10 nm on the hetero-substrate under the conditions of a magnetron sputtering pressure of 10 -7 torr, a magnetron sputtering power of 10 kW, and a magnetron sputtering time of 30 s.

[0193] Step S22: Grow a three-dimensional aluminum nitride layer with a thickness of 0.2 μm on the roughened layer under the conditions of a growth pressure of 200 torr, a growth temperature of 1150 °C, and a V / III ratio of 500.

[0194] Step S23: Grow a two-dimensional aluminum nitride layer with a thickness of 1 μm on the aluminum nitride buffer layer under the conditions of a growth pressure of 25 torr, a growth temperature of 1250 °C, and a V / III ratio of 100 to obtain an aluminum nitride epitaxial structure.

[0195] Next, in combination with the attached Figures 5 - 11 , Examples 1 - 6 and the comparative example are analyzed as follows:

[0196] 1. From the TEM images of the aluminum nitride epitaxial structure in Figures 5 - 7 and Figure 8 , it can be seen that, compared with the TEM images of Examples 1 - 3, the number of stripes in the TEM image of the comparative example is significantly more than that of Examples 1 - 3, indicating that the density of edge dislocations generated in the aluminum nitride epitaxial structure of the comparative example is greater. This means that the crystal quality of the AlN material in the aluminum nitride epitaxial structure of the present application is higher, which can significantly reduce the generation of screw dislocations and reduce the density of edge dislocations.

[0197] 2. In combination with the attached Figure 5 and Figure 9It can be seen from the TEM image of the aluminum nitride epitaxial structure that when the growth temperature of the two-dimensional aluminum nitride layer is lower than that of the three-dimensional aluminum nitride layer, the number of stripes in the TEM image of Example 4 is significantly more than that of Example 1, indicating that the density of edge dislocations generated in the aluminum nitride epitaxial structure of Example 4 is greater. This means that the crystal quality of the AlN material in the aluminum nitride epitaxial structure of this application is higher, and it can significantly reduce the generation of screw dislocations and decrease the density of edge dislocations.

[0198] 3. Combining the attached Figure 5 and Figure 10 It can be seen from the TEM image of the aluminum nitride epitaxial structure that when the growth ratio of the two-dimensional aluminum nitride layer is greater than that of the three-dimensional aluminum nitride layer, the number of stripes in the TEM image of Example 5 is significantly more than that of Example 1, indicating that the density of edge dislocations generated in the aluminum nitride epitaxial structure of Example 5 is greater. This means that the crystal quality of the AlN material in the aluminum nitride epitaxial structure of this application is higher, and it can significantly reduce the generation of screw dislocations and decrease the density of edge dislocations.

[0199] 4. Combining the attached Figure 5 and Figure 11 It can be seen from the TEM image of the aluminum nitride epitaxial structure that when the growth pressure of the three-dimensional aluminum nitride layer is greater than that of the two-dimensional aluminum nitride layer, the number of stripes in the TEM image of Example 6 is significantly more than that of Example 1, indicating that the density of edge dislocations generated in the aluminum nitride epitaxial structure of Example 6 is greater. This means that the crystal quality of the AlN material in the aluminum nitride epitaxial structure of this application is higher, and it can significantly reduce the generation of screw dislocations and decrease the density of edge dislocations.

[0200] Different from the traditional preparation method, after sputtering an aluminum nitride layer buffer layer on a heterogeneous substrate in the present invention, the growth of a lattice transition layer containing a first group III nitride is first carried out. The lattice transition layer serves as a lattice transition of the AlN material, and the purpose is to introduce the In element in the first group III nitride. The multiple first-period structures of AlInN and GaN (i.e., the periodic alternating growth structure of the AlInN layer / the first GaN layer) increase the stability for lattice-matched growth within each other's growth temperature ranges; then a roughening layer containing a second group III nitride is grown on the lattice transition layer, that is, the growth of multiple second-period structures including InGaN and GaN (i.e., the periodic alternating growth structure of the InGaN layer / the second GaN layer) is carried out. Due to the previous paving of AlInN / GaN, the In component of InGaN in the roughening layer can reach 15-25%; then during the process of heating up to grow the three-dimensional aluminum nitride layer, the In element will be precipitated, and the surface of the roughening layer will become rough. The rough surface provides a three-dimensional island growth mode for the AlN material growing the three-dimensional aluminum nitride layer; finally, during the growth of the two-dimensional aluminum nitride, due to the further increase in temperature and the further decrease in the V / III ratio, AlN will form a flattened two-dimensional aluminum nitride layer, and finally a two-dimensional aluminum nitride layer with a flat surface and high crystal quality can be formed on the three-dimensional aluminum nitride layer.

[0201] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Without departing from the principles and purposes of the present invention, those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the invention, and all these changes should fall within the protection scope of the claims of the present invention.

Claims

1. An aluminum nitride epitaxial structure, characterized in that: It comprises a foreign substrate and an aluminum nitride buffer layer grown on the foreign substrate, wherein the aluminum nitride buffer layer has an epitaxially grown lattice transition layer containing a first group III nitride; The lattice transition layer has an epitaxially grown roughened layer containing a second group III nitride; The roughening layer has a three-dimensional aluminum nitride layer and a two-dimensional aluminum nitride layer that are grown in sequence; Wherein, both the first group III nitride and the second group III nitride contain In element; in the process of adjusting the temperature in the growth chamber to the temperature required for growing the three-dimensional aluminum nitride layer, at least part of the In element is precipitated so that the roughened layer has a rough surface.

2. The aluminum nitride epitaxial structure according to claim 1, characterized in that: The composition ratio of In element in the first group III nitride is 10% to 15%; and / or the composition ratio of In element in the second group III nitride is 15% to 25%.

3. The aluminum nitride epitaxial structure according to claim 1, characterized in that: The lattice transition layer comprises a plurality of first periodic structures stacked in sequence, each of the first periodic structures comprises an AlInN layer and a first GaN layer stacked in layers; the starting layer of the lattice transition layer is an AlInN layer, and the ending layer of the lattice transition layer is a first GaN layer; and / or, The roughening layer includes a plurality of second periodic structures stacked in sequence, each of the first periodic structures includes an InGaN layer and a second GaN layer stacked in layers; the starting layer of the roughening layer is an InGaN layer, and the ending layer of the roughening layer is a second GaN layer.

4. The aluminum nitride epitaxial structure according to claim 3, characterized in that: The thickness of the aluminum nitride buffer layer is 10 to 100 nm; And / or, the thickness of the lattice transition layer is 50 to 200 nm; And / or, the thickness of the roughening layer is 10-100 nm; the thickness of the three-dimensional aluminum nitride layer is 0.2-0.5 μm; the thickness of the two-dimensional aluminum nitride layer is 1-2 μm; And / or, the thickness of the AlInN layer is 2-5 nm; the thickness of the first GaN layer is 3-10 nm, and the number of the first periodic structures is 10-20; And / or, the thickness of the InGaN layer is 2-4 nm; the thickness of the second GaN layer is 3-10 nm, and the number of the second periodic structures is 1-10.

5. A method for preparing an aluminum nitride epitaxial structure, characterized in that: include: providing a foreign substrate; An aluminum nitride buffer layer, a lattice transition layer comprising a first group III nitride, a roughening layer comprising a second group III nitride, a three-dimensional aluminum nitride layer and a two-dimensional aluminum nitride layer are sequentially grown on the heterogeneous substrate to obtain the aluminum nitride epitaxial structure; Wherein, both the first group III nitride and the second group III nitride contain In element; in the process of adjusting the temperature in the growth chamber to the temperature required for growing the three-dimensional aluminum nitride layer, at least part of the In element is precipitated so that the roughened layer has a rough surface.

6. The preparation method according to claim 5, characterized in that: The composition ratio of In element in the first group III nitride is 10% to 15%; and / or the composition ratio of In element in the second group III nitride is 15% to 25%; and / or, the growth temperature of the roughened layer is lower than the growth temperature of the three-dimensional aluminum nitride layer; and / or, the growth temperature of the two-dimensional aluminum nitride layer is greater than the growth temperature of the three-dimensional aluminum nitride layer; and / or, the V / III ratio for growing the two-dimensional aluminum nitride layer is less than the V / III ratio for growing the three-dimensional aluminum nitride layer; And / or, the growth pressure of the three-dimensional aluminum nitride layer is greater than the growth pressure of the two-dimensional aluminum nitride layer.

7. The preparation method according to claim 5, characterized in that: Growing the lattice transition layer comprises: Forming a plurality of first periodic structures stacked in sequence on the aluminum nitride buffer layer to obtain a lattice transition layer with a thickness of 50 to 200 nm; Wherein, the growth of each of the first periodic structures comprises: Under the conditions of a growth pressure of 500 to 760 torr, a growth temperature of 700 to 800° C., and a flow ratio of a growth source TMIn to a growth source TMAl of 1:1 to 5:1, an AlInN layer with a thickness of 2 to 5 nm is grown; A first GaN layer with a thickness of 3 to 10 nm is grown on the AlInN layer under the conditions of a growth pressure of 500 to 760 torr, a growth temperature of 900 to 1000° C., and a flow rate of a growth source TMGa of 100 to 1000 μmol / min.

8. The preparation method according to claim 5, characterized in that: Growing the roughening layer comprises: forming a plurality of second periodic structures stacked in sequence on the lattice transition layer to obtain a roughening layer with a thickness of 10 to 100 nm; Wherein, the growth of each of the second periodic structures comprises: Under the conditions of a growth pressure of 300 to 500 torr, a growth temperature of 600 to 700° C., and a flow ratio of a growth source TMIn to a growth source TMGa of 5:1 to 1:1, an InGaN layer with a thickness of 2 to 4 nm is grown; A second GaN layer with a thickness of 3 to 10 nm is grown on the InGaN layer under the conditions of a growth pressure of 300 to 500 torr, a growth temperature of 800 to 900° C., and a flow rate of a growth source TMGa of 100 to 1000 μmol / min.

9. The preparation method according to claim 8, characterized in that: The growth of the aluminum nitride buffer layer comprises: at a magnetron sputtering pressure of 10 -7 ~10 -9 torr, a magnetron sputtering power of 10 to 30 kW, and a magnetron sputtering time of 30 s to 3 min, growing an aluminum nitride buffer layer with a thickness of 10 to 100 nm on the foreign substrate; and / or, The growth of the three-dimensional aluminum nitride layer comprises: growing a three-dimensional aluminum nitride layer with a thickness of 0.2 to 0.5 μm on the roughened layer under the conditions of a growth pressure of 200 to 400 torr, a growth temperature of 1150 to 1250° C., and a V / III ratio of 500 to 1000; and / or, The growth of the two-dimensional aluminum nitride layer includes: growing a two-dimensional aluminum nitride layer with a thickness of 1 to 2 μm on the three-dimensional aluminum nitride layer under the conditions of a growth pressure of 25 to 75 torr, a growth temperature of 1250 to 1350° C., and a V / III ratio of 100 to 200.

10. A semiconductor device, characterized in that: The semiconductor device comprises the aluminum nitride epitaxial structure as described in any one of claims 1 to 4 or the aluminum nitride epitaxial structure obtained by the preparation method as described in any one of claims 5 to 9.

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