Epitaxial structure of radio frequency device and method of manufacturing the same

Abstract

The present disclosure provides an epitaxial structure of a radio frequency device and a preparation method thereof, and belongs to the technical field of semiconductors. The epitaxial structure of the radio frequency device comprises a substrate, a nucleation layer, a first AlN layer, a first GaN layer, a second AlN layer, an AlGaN layer and a second GaN layer which are stacked in sequence; the substrate comprises a substrate and an aluminum oxide film, the aluminum oxide film is stacked on the surface of the substrate, and the aluminum oxide film is located between the substrate and the nucleation layer. The present disclosure can improve the problem that the growth quality is affected due to the damage of the substrate during the growth process of the epitaxial structure of the radio frequency device, and improve the growth quality of the epitaxial structure.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and in particular to an epitaxial structure of a radio frequency device and its fabrication method. Background Technology

[0002] Gallium nitride (GaN) materials are widely used in power electronic devices, radio frequency (RF) devices, and optoelectronic devices due to their advantages such as large bandgap and high mobility. RF devices are common semiconductor optoelectronic conversion devices. Among them, the most widely used is the high electron mobility transistor (HEMT).

[0003] In related technologies, the epitaxial structure of radio frequency devices includes a silicon substrate, a nucleation layer, and an AlGaN / GaN heterojunction stacked sequentially.

[0004] However, during the epitaxial growth process, the substrate is susceptible to etching damage caused by temperature, gas, and MO source, which can affect the quality of the epitaxially grown AlN and GaN films. Summary of the Invention

[0005] This disclosure provides an epitaxial structure for a radio frequency (RF) device and its fabrication method, which can improve the growth quality of the RF device epitaxial structure due to substrate damage, thereby enhancing the growth quality of the epitaxial structure. The technical solution is as follows:

[0006] This disclosure provides an epitaxial structure for a radio frequency device, the epitaxial structure comprising a substrate, a nucleation layer, a first AlN layer, a first GaN layer, a second AlN layer, an AlGaN layer, and a second GaN layer stacked sequentially; the substrate comprises a substrate and an aluminum oxide film, the aluminum oxide film being stacked on the surface of the substrate and located between the substrate and the nucleation layer.

[0007] In one implementation of this disclosure, the thickness of the alumina film is 15 nm to 50 nm.

[0008] In another implementation of this disclosure, the nucleation layer includes AlN particles distributed on the surface of the substrate, and the particle density of the AlN particles in the nucleation layer is 10. 8 cm -2 Up to 10 9 cm -2 .

[0009] In another implementation of the present disclosure, the particle size of the AlN particles in the nucleation layer is 50 nm to 100 nm.

[0010] In another implementation of the present disclosure, the thickness of the nucleation layer is 15 nm to 80 nm.

[0011] In another implementation of this disclosure, the thickness of the first AlN layer is 1 μm to 2 μm, and the defect density of the first AlN layer is 5 × 10⁻⁶. 8 cm -2 Up to 5×10 9 cm -2 .

[0012] In another implementation of the present disclosure, the thickness of the first GaN layer is 150 nm to 300 nm; and the thickness of the second AlN layer is 15 nm to 30 nm.

[0013] In another implementation of the present disclosure, the thickness of the AlGaN layer is 15 nm to 30 nm, the molar content of Al in the AlGaN layer is 0.2 to 0.35, and the thickness of the second GaN layer is 3 nm to 15 nm.

[0014] This disclosure provides a method for fabricating an epitaxial structure of a radio frequency device. The method includes: providing a substrate; forming a nucleation layer, a first AlN layer, a first GaN layer, a second AlN layer, an AlGaN layer, and a second GaN layer sequentially on the substrate. The substrate includes a substrate and an aluminum oxide film, the aluminum oxide film being stacked on the surface of the substrate and located between the substrate and the nucleation layer.

[0015] In another implementation of the present disclosure, providing a substrate includes: performing a nitriding treatment on the substrate; depositing an aluminum oxide film on the substrate at a growth temperature controlled at 80°C to 150°C; and annealing the substrate at a temperature of 800°C to 1000°C to obtain the substrate.

[0016] The beneficial effects of the technical solutions provided in this disclosure include at least the following:

[0017] The epitaxial structure of the radio frequency device provided in this disclosure includes a substrate, a nucleation layer, a first AlN layer, a first GaN layer, a second AlN layer, an AlGaN layer, and a second GaN layer stacked sequentially. The substrate includes a substrate and an aluminum oxide film, with the aluminum oxide film stacked on the surface of the substrate and located between the substrate and the nucleation layer. By forming an aluminum oxide film on the surface of the substrate, the substrate can be protected from etching damage caused by temperature, gas, and MO sources, improving the growth quality of subsequent film layers. Furthermore, it alters the substrate lattice type, facilitating the high-quality growth of the subsequent nucleation layer, GaN, and AlN layers, resulting in high-quality nucleation layer, first AlN layer, first GaN layer, and second AlN layer. This effectively improves the growth quality of the film layers before the heterojunction layers (AlGaN layer and second GaN layer) and also enhances the growth quality of subsequent heterojunction layers, thereby improving the overall growth quality of the epitaxial structure of the radio frequency device. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the epitaxial structure of a radio frequency device provided in an embodiment of this disclosure;

[0020] Figure 2 This is a flowchart illustrating a method for fabricating an epitaxial structure of a radio frequency device according to an embodiment of this disclosure;

[0021] Figure 3 This is a fabrication state diagram of the epitaxial structure of a radio frequency device provided in an embodiment of this disclosure;

[0022] Figure 4 This is a fabrication state diagram of the epitaxial structure of a radio frequency device provided in an embodiment of this disclosure.

[0023] The markings in the diagram are explained as follows:

[0024] 10. Substrate; 11. Substrate; 12. Alumina film;

[0025] 20. Nucleation layer;

[0026] 31. First AlN layer; 32. First GaN layer; 33. Second AlN layer;

[0027] 41. AlGaN layer; 42. Second GaN layer. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0029] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” “top,” and “bottom,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0030] Figure 1 This is a schematic diagram of the epitaxial structure of a radio frequency device provided in an embodiment of this disclosure. Figure 1 As shown, the epitaxial structure of the radio frequency device includes a substrate 10, a nucleation layer 20, a first AlN layer 31, a first GaN layer 32, a second AlN layer 33, an AlGaN layer 41, and a second GaN layer 42 stacked sequentially.

[0031] like Figure 1 As shown, the substrate 10 includes a substrate 11 and an aluminum oxide film 12, the aluminum oxide film 12 being stacked on the surface of the substrate 11 and the aluminum oxide film 12 being located between the substrate 11 and the nucleation layer 20.

[0032] The epitaxial structure of the radio frequency device provided in this embodiment includes a substrate 10, a nucleation layer 20, a first AlN layer 31, a first GaN layer 32, a second AlN layer 33, an AlGaN layer 41, and a second GaN layer 42 stacked sequentially. The substrate 10 includes a substrate 11 and an aluminum oxide film 12, which is stacked on the surface of the substrate 11 and located between the substrate 11 and the nucleation layer 20. By forming an aluminum oxide film 12 on the surface of the substrate 11, the substrate 11 can be protected from etching damage caused by temperature, gas and MO source, thus improving the growth quality of subsequent film layers. On the other hand, it can change the lattice type of the substrate 11, which facilitates the high-quality growth of the subsequent nucleation layer 20, GaN and AlN layers, so as to obtain high-quality nucleation layer 20, first AlN layer 31, first GaN layer 32 and second AlN layer 33. This effectively improves the growth quality of the film layers before the heterojunction layer (AlGaN layer 41 and second GaN layer 42), and also improves the growth quality of the subsequent heterojunction layer, thereby improving the overall growth quality of the epitaxial structure of the radio frequency device.

[0033] In this embodiment of the disclosure, the substrate 11 in the substrate 10 may include one of a silicon substrate, a sapphire substrate, a silicon carbide substrate, a glass substrate, a gallium arsenide substrate, and a self-supporting substrate.

[0034] For example, substrate 11 may be a silicon substrate. Silicon substrates are large in size, low in cost, and compatible with Si process lines, offering significant cost advantages and large-scale production capabilities.

[0035] Optionally, the thickness of the alumina film 12 is 15 nm to 50 nm.

[0036] By setting the thickness of the alumina film 12 within the above-mentioned range, the thickness of the alumina film 12 can be reasonably controlled, which can avoid the alumina film 12 deposited on the substrate 11 being too thick and increasing the preparation cost; it can also avoid the alumina film 12 deposited on the substrate 11 being too thin and failing to protect the substrate 11 from etching damage caused by temperature, gas and MO source.

[0037] As an example, in this embodiment of the disclosure, the thickness of the alumina film 12 is 30 nm. This thickness of the alumina film 12 can protect the substrate 11 from etching damage caused by temperature, gas, and MO source, thereby improving the growth quality of subsequent film layers.

[0038] Optionally, the nucleation layer 20 includes AlN particles distributed on the surface of the substrate 10. The nucleation layer 20 is a film formed by the deposition of AlN particles, and the particle distribution density of the AlN particles in the nucleation layer 20 is 10. 8 cm -2 Up to 10 9 cm -2 .

[0039] The particle distribution density of the nucleation layer 20 refers to the number of AlN particles distributed per unit area within the nucleation layer 20. A higher particle distribution density indicates a greater number of AlN particles per unit area, meaning a denser AlN particle distribution; conversely, a lower particle distribution density indicates a smaller number of AlN particles per unit area, meaning a sparser AlN particle distribution.

[0040] In the above implementation, the nucleation layer 20 is formed by depositing AlN particles. Since the particles can effectively relieve stress, the nucleation layer 20 formed by the particles is more likely to relieve stress accumulation, thereby effectively balancing the stress accumulation of the subsequent epitaxial structure, improving the stress mismatch between the substrate 11 and the gallium nitride material, and improving the growth quality of the AlGaN / GaN heterojunction.

[0041] In this embodiment of the disclosure, by setting the particle distribution density of the AlN particles in the nucleation layer 20 within the above-mentioned range, it is possible to avoid the distribution of AlN particles being too sparse or too dense, which would make it difficult to effectively balance the stress accumulation of the subsequent epitaxial structure.

[0042] For example, the particle distribution density of AlN particles is 10. 8 cm -2 .

[0043] Optionally, the particle size of the AlN particles in the nucleation layer 20 is 20 nm to 80 nm.

[0044] By setting the particle size of the AlN particles in the nucleation layer 20 within the above-mentioned range, the size of the AlN particles in the nucleation layer 20 can be reasonably controlled, avoiding the AlN particles being too large or too small, which would affect the stress relief effect of the particles.

[0045] For example, the AlN particles of the nucleation layer 20 can be spherical, and the particle size of the AlN particles of the nucleation layer 20 can be 50 nm.

[0046] Optionally, the thickness of the nucleation layer 20 is 15 nm to 80 nm.

[0047] By setting the thickness of the nucleation layer 20 within the above-mentioned range, the thickness of the nucleation layer 20 can be reasonably controlled. This can prevent the thickness of the nucleation layer 20 deposited on the substrate 11 from being too large, which would increase the preparation cost. It can also prevent the thickness of the nucleation layer 20 deposited on the substrate 11 from being too small, which would prevent the formation of AlN particles and thus fail to effectively balance the stress accumulation of the subsequent epitaxial structure.

[0048] As an example, in this embodiment of the disclosure, the nucleation layer 20 has a thickness of 50 nm. This thickness of the nucleation layer 20 can effectively and appropriately sized AlN particles to balance the stress accumulation effect of subsequent epitaxial structures, improve the stress mismatch between the substrate 11 and the gallium nitride material, and enhance the growth quality of the AlGaN / GaN heterojunction.

[0049] Optionally, the thickness of the first AlN layer 31 is 1 μm to 2 μm. The thickness direction of the first AlN layer 31 is perpendicular to the substrate 10.

[0050] In the above implementation, by growing a thicker first AlN layer 31, lattice relaxation can be achieved, which facilitates the subsequent epitaxial growth of a high-quality GaN crystal film.

[0051] For example, the thickness of the first AlN layer 31 is 1.5 μm.

[0052] Optionally, the defect density of the first AlN layer 31 is 5 × 10⁻⁶. 8 cm -2 Up to 5×10 9 cm -2 .

[0053] As an example, in this embodiment of the present disclosure, the defect density of the first AlN layer 31 is 5 × 10⁻⁶. 8 cm -2 .

[0054] In the above implementation, by controlling the defect density of the first AlN layer 31 within the above range, a high-quality first AlN layer 31 is formed to complete the lattice transformation, so that the subsequent film structures can be grown with high quality.

[0055] Optionally, the thickness of the first GaN layer 32 is 150 nm to 300 nm, and the O content in the first GaN layer 32 is 5 × 10⁻⁶. 16 cm -3 Up to 5×10 17 cm -3 .

[0056] As an example, in this embodiment of the present disclosure, the thickness of the first GaN layer 32 is 200 nm, and the O content in the first GaN layer 32 is 5 × 10⁻⁶. 16 cm -3 .

[0057] In the above implementation, by controlling the thickness of the first GaN layer 32 within the above range and the O content in the first GaN layer 32 within the above range, a high-quality first GaN layer 32 can be formed, so that the subsequent film structures can be grown with high quality.

[0058] In this embodiment, the second AlN layer 33 is a high-resistivity layer. By setting the high-resistivity layer, the leakage current of the radio frequency device can be effectively reduced, the additional capacitance can be reduced, so as to achieve efficient growth of the heterojunction layer and improve the growth quality of AlGaN / GaN heterojunction.

[0059] Optionally, the thickness of the second AlN layer 33 is 15 nm to 30 nm.

[0060] By setting the thickness of the second AlN layer 33 within the above range, it is possible to avoid the second AlN layer 33 being too thin, which would affect its performance in improving the leakage current of the RF device, and it is also possible to avoid the second AlN layer 33 being too thick, which would increase the manufacturing cost.

[0061] As an example, in this embodiment of the disclosure, the thickness of the second AlN layer 33 is 20 nm.

[0062] Optionally, in the heterojunction layer, the AlGaN layer 41 has a thickness of 15 nm to 30 nm, and the molar content of Al in the AlGaN layer 41 is 0.2 to 0.35. The second GaN layer 42 has a thickness of 3 nm to 15 nm, and the second GaN layer 42 is undoped.

[0063] By setting the thickness of the AlGaN layer 41 and the thickness of the second GaN layer 42 within the aforementioned range, it is possible to avoid the AlGaN layer 41 and the second GaN layer 42 being too thin, which would affect the function of the heterojunction layer. It is also possible to avoid the AlGaN layer 41 and the second GaN layer 42 being too thick, which would increase manufacturing costs. Simultaneously, setting the molar content of Al in the AlGaN layer 41 within the aforementioned range ensures the function of the heterojunction layer.

[0064] As an example, in this embodiment of the disclosure, the thickness of AlGaN layer 41 is 20 nm, the molar content of Al in AlGaN layer 41 is 0.3, and the thickness of the second GaN layer 42 is 10 nm.

[0065] Figure 2 This is a flowchart illustrating a method for fabricating an epitaxial structure of a radio frequency device according to an embodiment of this disclosure. Figure 2 As shown, this preparation method is suitable for preparing, for example... Figure 1 The epitaxial structure of the radio frequency device shown includes:

[0066] Step S11: Provide a substrate 10;

[0067] Step S12: A nucleation layer 20, a first AlN layer 31, a first GaN layer 32, a second AlN layer 33, an AlGaN layer 41, and a second GaN layer 42 are sequentially formed on the substrate 10.

[0068] The substrate 10 includes a substrate 11 and an aluminum oxide film 12, wherein the aluminum oxide film 12 is stacked on the surface of the substrate 11 and is located between the substrate 11 and the nucleation layer 20.

[0069] The epitaxial structure of the radio frequency device provided in this embodiment includes a substrate 10, a nucleation layer 20, a first AlN layer 31, a first GaN layer 32, a second AlN layer 33, an AlGaN layer 41, and a second GaN layer 42, which are stacked sequentially. The substrate 10 includes a substrate 11 and an aluminum oxide film 12, which is stacked on the surface of the substrate 11 and located between the substrate 11 and the nucleation layer 20. By forming an aluminum oxide film 12 on the surface of the substrate 11, the substrate 11 can be protected from etching damage caused by temperature, gas, and MO sources, thus improving the growth quality of subsequent film layers. Furthermore, it alters the lattice type of the substrate 11, facilitating the high-quality growth of the subsequent nucleation layer 20, GaN, and AlN layers, resulting in high-quality nucleation layer 20, first AlN layer 31, first GaN layer 32, and second AlN layer 33. This effectively improves the growth quality of the film layers before the heterojunction layer and also enhances the growth quality of the subsequent heterojunction layer, thereby improving the overall growth quality of the epitaxial structure of the radio frequency device.

[0070] In step S11, the substrate 10 includes a substrate 11 and an aluminum oxide film 12 located on the substrate 11. The substrate 11 includes one of a silicon substrate, a sapphire substrate, a silicon carbide substrate, a glass substrate, a gallium arsenide substrate, and a self-supporting substrate.

[0071] The substrate 11 can be a silicon substrate. Silicon substrates are large in size and low in cost, and are compatible with Si process lines, giving them significant cost advantages and large-scale production capabilities.

[0072] Optionally, such as Figure 3 As shown, the process of forming substrate 10 may include the following steps:

[0073] The first step is to perform nitriding on substrate 11.

[0074] Specifically, this may include, after cleaning the surface of the substrate 11, introducing nitrogen gas to dry the substrate 11 in order to perform nitriding treatment on the substrate 11.

[0075] The second step involves controlling the growth temperature to 80°C to 150°C to deposit an aluminum oxide film 12 on the substrate 11.

[0076] For example, an alumina film 12 is deposited at 100°C.

[0077] The thickness of the deposited alumina film 12 is 15 nm to 50 nm.

[0078] By setting the thickness of the alumina film 12 within the above-mentioned range, the thickness of the alumina film 12 can be reasonably controlled, which can avoid the alumina film 12 deposited on the substrate 11 being too thick and increasing the preparation cost; it can also avoid the alumina film 12 deposited on the substrate 11 being too thin and failing to protect the substrate 11 from etching damage caused by temperature, gas and MO source.

[0079] As an example, in this embodiment of the disclosure, the thickness of the alumina film 12 is 30 nm.

[0080] The third step is to anneal the substrate 11 at a temperature of 800°C to 1000°C to obtain the substrate 10.

[0081] For example, the substrate 11 is annealed at a temperature of 900°C for a time of 5 to 20 minutes. Annealing the substrate 11 eliminates stress between the alumina film 12 and the substrate 11, thereby improving the stability of the alumina film 12.

[0082] In step S12, as Figure 4 As shown, the growth of nucleation layer 20 may include: controlling the temperature to be 400°C to 800°C, the molar ratio of ammonia gas to metal Mo source to be 3000 to 10000, and depositing AlN particles on the substrate to form nucleation layer.

[0083] The substrate is a heterogeneous substrate. A heterogeneous substrate is a substrate made of a material with a lattice different from that of the epitaxial material. For example, a heterogeneous substrate can be a silicon wafer, sapphire, diamond, GaAs, or InP.

[0084] Specifically, it may include: First, adjusting the temperature to 600℃, controlling the molar ratio of the introduced ammonia gas to the metal Mo source to be 5000, depositing AlN particles, and forming a nucleation layer 20 on the substrate 11.

[0085] The particle distribution density of AlN particles in nucleation layer 20 is 10. 8 cm -2 Up to 10 9 cm -2 .

[0086] By using AlN particles to deposit and form a nucleation layer 20, since particles can effectively relieve stress, the nucleation layer 20 formed by particles is more likely to relieve stress accumulation, thereby effectively balancing the stress accumulation of subsequent epitaxial structures, improving the stress mismatch between the substrate 11 and the gallium nitride material, and improving the growth quality of AlGaN / GaN heterojunction.

[0087] In this embodiment of the disclosure, by setting the particle distribution density of the AlN particles in the nucleation layer 20 within the above-mentioned range, it is possible to avoid the distribution of AlN particles being too sparse or too dense, which would make it difficult to effectively balance the stress accumulation of the subsequent epitaxial structure.

[0088] For example, the particle distribution density of AlN particles is 10. 8 cm -2 .

[0089] Optionally, the particle size of the AlN particles in the nucleation layer 20 is 20 nm to 80 nm.

[0090] By reasonably controlling the size of AlN particles in the nucleation layer 20, the particle size of AlN particles can be avoided from being too large or too small, which would affect the stress relief effect of the particles.

[0091] For example, the AlN particles of the nucleation layer 20 can be spherical, and the particle size of the AlN particles of the nucleation layer 20 can be 50 nm.

[0092] Optionally, the thickness of the nucleation layer 20 is 15 nm to 80 nm.

[0093] By reasonably controlling the thickness of the nucleation layer 20, it is possible to avoid the nucleation layer 20 deposited on the substrate 11 being too thick, thus increasing the preparation cost; it is also possible to avoid the nucleation layer 20 deposited on the substrate 11 being too thin, thus failing to form AlN particles and failing to effectively balance the stress accumulation of the subsequent epitaxial structure.

[0094] As an example, in this embodiment of the disclosure, the thickness of the nucleation layer 20 is 50 nm.

[0095] In step S12, as Figure 4 As shown, after the formation of the nucleation layer 20, the process includes: growing a first AlN layer 31 on the nucleation layer 20.

[0096] The thickness of the first AlN layer 31 is 1 μm to 2 μm. The thickness direction of the first AlN layer 31 is perpendicular to the substrate 10.

[0097] For example, the thickness of the first AlN layer 31 is 1.5 μm. By growing a relatively thick first AlN layer 31, lattice relaxation can be achieved, which facilitates the subsequent epitaxial growth of high-quality GaN crystal films.

[0098] The growth temperature of the first AlN layer 31 can be from 1000℃ to 1200℃.

[0099] Optionally, the defect density of the first AlN layer 31 is 5 × 10⁻⁶. 8 cm -2 Up to 5×10 9 cm-2 .

[0100] As an example, in this embodiment of the present disclosure, the defect density of the first AlN layer 31 is 5 × 10⁻⁶. 8 cm -2 .

[0101] In the above implementation, by controlling the defect density of the first AlN layer 31 within the above range, a high-quality first AlN layer 31 is formed to complete the lattice transformation, so that the subsequent film structures can be grown with high quality.

[0102] In step S12, as Figure 4 As shown, after forming the first AlN layer 31, the process includes growing a first GaN layer 32 on the first AlN layer 31.

[0103] The thickness of the first GaN layer 32 is 150 nm to 300 nm, and the O content in the first GaN layer 32 is 5 × 10⁻⁶. 16 cm -3 Up to 5×10 17 cm -3 .

[0104] As an example, in this embodiment of the present disclosure, the thickness of the first GaN layer 32 is 200 nm, and the O content in the first GaN layer 32 is 5 × 10⁻⁶. 16 cm -3 .

[0105] In the above implementation, by controlling the thickness of the first GaN layer 32 within the above range and the O content in the first GaN layer 32 within the above range, a high-quality first GaN layer 32 can be formed, so that the subsequent film structures can be grown with high quality.

[0106] The growth temperature of the first GaN layer 32 can be between 1000℃ and 1200℃.

[0107] In step S12, as Figure 4 As shown, after forming the first GaN layer 32, the process includes growing a second AlN layer 33 on the first GaN layer 32.

[0108] By setting the second AlN layer 33 as a high-resistivity layer, the leakage current of RF devices can be effectively reduced, and the additional capacitance can be reduced, so as to achieve efficient growth of the heterojunction layer and improve the growth quality of AlGaN / GaN heterojunction.

[0109] The thickness of the second AlN layer 33 is 15nm to 30nm.

[0110] By setting the thickness of the second AlN layer 33 within the above range, it is possible to avoid the second AlN layer 33 being too thin, which would affect its performance in improving the leakage current of the RF device, and it is also possible to avoid the second AlN layer 33 being too thick, which would increase the manufacturing cost.

[0111] As an example, in this embodiment of the disclosure, the thickness of the second AlN layer 33 is 20 nm.

[0112] The growth temperature of the second AlN layer 33 can be from 1000℃ to 1200℃.

[0113] In step S12, as Figure 1 As shown, the formation of a heterojunction layer includes the following two steps:

[0114] The first step is to adjust the temperature to 1000℃ to 1200℃ and grow an AlGaN layer 41 on the second AlN layer 33.

[0115] The second step involves adjusting the temperature to 1000℃ to 1200℃ to grow a second GaN layer 42 on the AlGaN layer 41.

[0116] In the heterojunction layer, the AlGaN layer 41 has a thickness of 15 nm to 30 nm, and the molar content of Al in the AlGaN layer 41 is 0.2 to 0.35. The second GaN layer 42 has a thickness of 3 nm to 15 nm and is undoped.

[0117] By setting the thickness of the AlGaN layer 41 and the thickness of the second GaN layer 42 within the aforementioned range, it is possible to avoid the AlGaN layer 41 and the second GaN layer 42 being too thin, which would affect the function of the heterojunction layer. It is also possible to avoid the AlGaN layer 41 and the second GaN layer 42 being too thick, which would increase manufacturing costs. Simultaneously, setting the molar content of Al in the AlGaN layer 41 within the aforementioned range ensures the function of the heterojunction layer.

[0118] As an example, in this embodiment of the disclosure, the thickness of AlGaN layer 41 is 20 nm, the molar content of Al in AlGaN layer 41 is 0.3, and the thickness of the second GaN layer 42 is 10 nm.

[0119] Finally, after epitaxial growth is complete, the structure is cooled to room temperature and removed for later use.

[0120] The above is not intended to limit this disclosure in any way. Although this disclosure has been disclosed above through embodiments, it is not intended to limit this disclosure. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this disclosure. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this disclosure without departing from the content of the technical solution of this disclosure shall still fall within the scope of the technical solution of this disclosure.

Claims

1. An epitaxial structure for a radio frequency device, characterized in that, The epitaxial structure includes a substrate (10), a nucleation layer (20), a first AlN layer (31), a first GaN layer (32), a second AlN layer (33), an AlGaN layer (41), and a second GaN layer (42) stacked sequentially. The substrate (10) includes a substrate (11) and an aluminum oxide film (12), wherein the aluminum oxide film (12) is stacked on the surface of the substrate (11) and the aluminum oxide film (12) is located between the substrate (11) and the nucleation layer (20); The nucleation layer (20) includes AlN particles distributed on the surface of the substrate (10), and the particle density of the AlN particles in the nucleation layer (20) is 10. 8 cm -2 Up to 10 9 cm -2 The nucleation layer (20) is a film formed by the deposition of ALN particles.

2. The epitaxial structure according to claim 1, characterized in that, The thickness of the alumina film (12) is 15 nm to 50 nm.

3. The epitaxial structure according to claim 1, characterized in that, The particle size of the AlN particles in the nucleation layer (20) is 50 nm to 100 nm.

4. The epitaxial structure according to claim 1, characterized in that, The thickness of the nucleation layer (20) is 15 nm to 80 nm.

5. The epitaxial structure according to any one of claims 1 to 4, characterized in that, The thickness of the first AlN layer (31) is 1 μm to 2 μm, and the defect density of the first AlN layer (31) is 5 × 10⁻⁶. 8 cm -2 Up to 5×10 9 cm -2 .

6. The epitaxial structure according to any one of claims 1 to 4, characterized in that, The thickness of the first GaN layer (32) is 150 nm to 300 nm; the thickness of the second AlN layer (33) is 15 nm to 30 nm.

7. The epitaxial structure according to any one of claims 1 to 4, characterized in that, The AlGaN layer (41) has a thickness of 15 nm to 30 nm, the molar content of Al in the AlGaN layer (41) is 0.2 to 0.35, and the thickness of the second GaN layer (42) is 3 nm to 15 nm.

8. A method for fabricating an epitaxial structure of a radio frequency device, characterized in that, The preparation method includes: Provide a substrate; A nucleation layer, a first AlN layer, a first GaN layer, a second AlN layer, an AlGaN layer, and a second GaN layer are sequentially formed on the substrate. The substrate includes a substrate and an alumina film, the alumina film being stacked on the surface of the substrate and located between the substrate and the nucleation layer. The nucleation layer includes AlN particles distributed on the surface of the substrate, and the particle density of the AlN particles in the nucleation layer is 10. 8 cm -2 Up to 10 9 cm -2 The nucleation layer is a film formed by the deposition of ALN particles.

9. The preparation method according to claim 8, characterized in that, The provision of a substrate includes: Nitriding treatment is performed on the substrate; An aluminum oxide film is deposited on the substrate by controlling the growth temperature to be between 80°C and 150°C. The substrate is annealed at a temperature of 800°C to 1000°C to obtain the substrate.

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