Gallium nitride epitaxial wafer, its manufacturing method, and semiconductor device

Abstract

The present application discloses a gallium nitride epitaxial wafer, a manufacturing method thereof, and a semiconductor device. The gallium nitride epitaxial wafer includes a single-crystal diamond substrate; a lattice matching layer disposed on one side of the diamond substrate; a gallium nitride epitaxial layer disposed on the side of the lattice matching layer away from the diamond substrate; the lattice constant of the side of the lattice matching layer close to the gallium nitride epitaxial layer matches the lattice constant of the gallium nitride material. By providing the lattice matching layer to match the lattice between the single-crystal diamond substrate and the gallium nitride epitaxial layer, the present application can directly fabricate the gallium nitride epitaxial layer on the diamond substrate, achieving the purpose of simplifying the process flow, improving the chip performance, and reducing the manufacturing cost.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular, to a gallium nitride epitaxial wafer, a manufacturing method thereof, and a semiconductor device. Background Art

[0002] Compound semiconductor materials have developed rapidly in recent years and are increasingly widely used in lighting, optical communication, power semiconductor devices, and wireless communication fields. Wide bandgap (bandgap width > 2.3 eV) compound semiconductors include silicon carbide, gallium nitride, gallium oxide, diamond, etc. They have broad application prospects in the development of high-temperature, high-frequency, high-power microwave devices, radiation-resistant devices, ultraviolet detectors, short-wave light-emitting diodes, etc., and are electronic devices urgently needed in fields such as wireless communication, national defense, new energy, and autonomous driving.

[0003] Gallium nitride materials have a wide bandgap (3.4 eV), high electron mobility, and high breakdown electric field, and are important materials for developing high-temperature high-power electronic devices and high-frequency microwave devices. The high electron mobility transistor (HEMT) based on GaN material has a high electron mobility (2000 cm 2 / v·s), high electron saturation velocity (1×10 7 cm / s), and a relatively low dielectric constant, and is the preferred material for making radio frequency microwave devices. GaN devices with substrates such as silicon carbide have good heat dissipation performance, which is beneficial for the devices to work under high-power conditions, and are increasingly widely used in fields such as mobile communication system infrastructure, aerospace, national defense technology, and satellite communication.

[0004] However, the chip thermal effect generated under high-voltage and high-power working conditions affects the performance and reliability of the device, which is one of the factors restricting the further application of gallium nitride chips. Using a diamond substrate with a high thermal conductivity is one of the methods to improve the chip thermal effect. Currently, gallium nitride chips with a diamond substrate have a complex process and high manufacturing cost. Summary of the Invention

[0005] The purpose of the present application is to provide a gallium nitride epitaxial wafer, a manufacturing method thereof, and a semiconductor device with a simple process and high stability.

[0006] The present application discloses a gallium nitride epitaxial wafer, which includes:

[0007] A single-crystal diamond substrate;

[0008] A lattice matching layer, which is disposed on one side of the diamond substrate;

[0009] A gallium nitride epitaxial layer, which is disposed on the side of the lattice matching layer away from the diamond substrate;

[0010] The lattice constant of one side of the lattice matching layer close to the gallium nitride epitaxial layer matches the lattice constant of the gallium nitride material.

[0011] Optionally, the lattice matching layer includes a seed layer, the thickness of the seed layer is greater than or equal to 1 nm and less than or equal to 10 nm; the seed layer is made of aluminum nitride.

[0012] Optionally, the lattice matching layer includes a buffer layer, the thickness of the buffer layer is greater than or equal to 0.2 μm and less than or equal to 2 μm; the buffer layer is made of undoped high-resistance aluminum nitride.

[0013] Optionally, the lattice matching layer includes a transition layer, the thickness of the transition layer is greater than or equal to 0.3 μm and less than or equal to 3 μm; the transition layer is a gallium-containing nitride, and the gallium content on the side of the transition layer close to the diamond substrate is less than that on the side close to the gallium nitride epitaxial layer.

[0014] Optionally, the lattice matching layer includes a transition layer, the thickness of the transition layer is greater than or equal to 0.3 μm and less than or equal to 3 μm; the transition layer is made of indium aluminum nitride, and from the side close to the diamond substrate to the side close to the gallium nitride epitaxial layer, the indium content gradually approaches 17% and the aluminum content gradually approaches 83%.

[0015] Optionally, the lattice matching layer includes a superlattice structure layer, and the superlattice structure layer includes a number of sequentially stacked first superlattice layers, second superlattice layers, ······ nth superlattice layers; the superlattice structure layer is aluminum indium gallium nitride, and the component content of at least one of the three elements of aluminum, indium, and gallium in adjacent superlattice layers is different.

[0016] Optionally, the aluminum content on the side of the superlattice structure layer close to the diamond substrate is greater than that on the side close to the gallium nitride epitaxial layer.

[0017] Optionally, the lattice matching layer further includes:

[0018] A buffer layer disposed on the side of the seed layer away from the diamond substrate, the thickness of the buffer layer is greater than or equal to 0.2 μm and less than or equal to 2 μm; the buffer layer is made of undoped high-resistance aluminum nitride.

[0019] Optionally, the lattice matching layer further includes:

[0020] A transition layer disposed on a side of the buffer layer away from the seed layer, the thickness of the transition layer being greater than or equal to 0.3 μm and less than or equal to 3 μm; the transition layer being a gallium-containing nitride, and the gallium content of the transition layer on a side close to the diamond substrate being less than that on a side close to the gallium nitride epitaxial layer.

[0021] Optionally, the lattice matching layer further includes:

[0022] A superlattice structure layer disposed on a side of the buffer layer away from the seed layer, the superlattice structure layer including a plurality of sequentially stacked first superlattice layers, second superlattice layers,..., nth superlattice layers; the superlattice structure layer being an aluminum indium gallium nitride, and the component contents of at least one of the three elements of aluminum, indium, and gallium being different in adjacent superlattice layers; the aluminum content of the superlattice structure layer on a side close to the diamond substrate being greater than that on a side close to the gallium nitride epitaxial layer.

[0023] Optionally, the lattice matching layer further includes:

[0024] A superlattice structure layer disposed on a side of the transition layer away from the buffer layer, the superlattice structure layer including a plurality of sequentially stacked first superlattice layers, second superlattice layers,..., nth superlattice layers; the superlattice structure layer being an aluminum indium gallium nitride, and the component contents of at least one of the three elements of aluminum, indium, and gallium being different in adjacent superlattice layers; the aluminum content of the superlattice structure layer on a side close to the diamond substrate being greater than that on a side close to the gallium nitride epitaxial layer.

[0025] The present application also discloses a method for manufacturing a gallium nitride epitaxial wafer for manufacturing the above-mentioned gallium nitride epitaxial wafer, which includes:

[0026] Manufacturing a lattice matching layer on a single-crystal diamond substrate;

[0027] Manufacturing a gallium nitride epitaxial layer on a side of the lattice matching layer away from the diamond substrate.

[0028] Optionally, the lattice matching layer includes one or two or three or four of the seed layer, buffer layer, transition layer, and superlattice structure layer.

[0029] The present application also discloses a semiconductor device, and the semiconductor device includes the above-mentioned gallium nitride epitaxial wafer.

[0030] Compared with the related art, the present application matches the lattice between the single-crystal diamond substrate and the gallium nitride epitaxial layer by providing a lattice matching layer, so that the gallium nitride epitaxial layer can be directly prepared on the diamond substrate, simplifying the process flow and reducing the manufacturing cost.

[0031] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and do not limit this specification. Description of the Drawings

[0032] The drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with this specification, and are used together with the specification to explain the principles of this specification.

[0033] Figure 1 Schematic diagram of the contact surface between a diamond substrate and a gallium nitride epitaxial layer in the related art.

[0034] Figure 2 Schematic diagram of the structure of a gallium nitride epitaxial wafer in an embodiment of the present application.

[0035] Figure 3 Schematic diagram of the structure of a gallium nitride epitaxial wafer in an embodiment of the present application.

[0036] Figure 4 Schematic diagram of the structure of a gallium nitride epitaxial wafer in an embodiment of the present application.

[0037] Figure 5 Schematic diagram of the structure of a gallium nitride epitaxial wafer in an embodiment of the present application.

[0038] Figure 6 Schematic diagram of the structure of a gallium nitride epitaxial wafer in an embodiment of the present application.

[0039] Figure 7 Schematic diagram of the structure of a gallium nitride epitaxial wafer in an embodiment of the present application.

[0040] Figure 8 Schematic diagram of the structure of a gallium nitride epitaxial wafer in an embodiment of the present application.

[0041] Figure 9 Schematic diagram of the structure of a semiconductor device in an embodiment of the present application. Detailed Embodiments

[0042] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this specification. On the contrary, they are merely examples of devices and methods consistent with some aspects of this specification as detailed in the appended claims.

[0043] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. Unless otherwise defined, technical or scientific terms used in this specification shall have the ordinary meaning as understood by those of ordinary skill in the art to which this application pertains. The terms "first", "second" and similar words used in this specification and the claims do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "a" or "an" do not denote a quantity limitation, but rather denote the presence of one. "Plural" or "several" means two or more. Unless otherwise indicated, words such as "front", "rear", "lower" and / or "upper" are for convenience only and are not limited to one position or a spatial orientation. The words "comprising" or "including" and similar words mean that the elements or items appearing before "comprising" or "including" cover the elements or items listed after "comprising" or "including" and their equivalents, and do not exclude other elements or items. The words "connected" or "coupled" and similar words are not limited to physical or mechanical connections, and may include electrical connections, whether direct or indirect.

[0044] The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms "a", "the" and "said" used in this specification and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0045] As Figure 1 shown, in the related art, the gallium nitride epitaxial layer 300 material and the diamond substrate 100 material have different lattice constants and thermal expansion coefficients. The difference in lattice constants causes lattice mismatch between the diamond substrate 100 and the gallium nitride epitaxial layer 300, resulting in the generation of dislocation defect A. Lattice mismatch also generates stress in the material and causes wafer warping and cracking. Due to the difference in thermal expansion coefficients, when the temperature changes during the growth process, stress is generated in the material, resulting in the generation of warp and crack. The lattice constants of diamond (cubic crystal structure) and gallium nitride crystal are a = 3.57 Å and b = 3.19 Å respectively, and the lattice mismatch is 10.6%. The thermal expansion coefficients of diamond and aluminum nitride materials are 1.2*10 -6 K -1 and 3.17*10 -6 K -1 , with a mismatch of 62%. When the lattice constant of the epitaxial layer material is smaller than that of the substrate, or when the thermal expansion coefficient of the epitaxial material is greater than that of the substrate, the wafer will have concave warping.

[0046] In the existing manufacturing technology of gallium nitride devices with diamond as the substrate, the substrate is polycrystalline diamond material. First, a gallium nitride epitaxial layer is fabricated on a silicon, silicon carbide, or sapphire substrate, then the gallium nitride epitaxial layer is peeled off from the substrate, and then the gallium nitride epitaxial layer is bonded to the polycrystalline diamond substrate. Finally, gallium nitride devices are fabricated on the gallium nitride epitaxial layer. This process flow is relatively complex, with poor process stability, low chip yield, and high manufacturing cost.

[0047] As Figure 2 shown, to solve the above problems, the present application provides a gallium nitride epitaxial wafer, which includes:

[0048] A single-crystal diamond substrate 100;

[0049] A lattice matching layer 200, which is disposed on one side of the diamond substrate 100;

[0050] A gallium nitride epitaxial layer 300, which is disposed on the side of the lattice matching layer 200 away from the diamond substrate 100;

[0051] The lattice constant of the side of the lattice matching layer 200 close to the gallium nitride epitaxial layer 300 matches the lattice constant of the gallium nitride material.

[0052] The present application simplifies the process flow and reduces the manufacturing cost by setting a lattice matching layer to match the lattices between the single-crystal diamond substrate and the gallium nitride epitaxial layer, so that the gallium nitride epitaxial layer can be directly fabricated on the diamond substrate.

[0053] The following will detail each embodiment of the present application that conforms to the above creative concept.

[0054] As Figure 2 shown, the present application provides a gallium nitride epitaxial wafer, which includes a single-crystal diamond substrate 100, a lattice matching layer 200, and a gallium nitride epitaxial layer 300. The lattice matching layer 200 is disposed on one side of the diamond substrate 100. The gallium nitride epitaxial layer 300 is disposed on the side of the lattice matching layer 200 away from the diamond substrate 100. Inside the lattice matching layer 200, pointing from the diamond substrate 100 to the gallium nitride epitaxial layer 300, the material and / or structure of the lattice matching layer 200 change. The change in the material and / or structure of the lattice matching layer 200 causes a change in the lattice constant inside the lattice matching layer 200, so that the lattice constant of the side of the lattice matching layer 200 close to the gallium nitride epitaxial layer 300 matches the lattice constant of the gallium nitride material. The change in the material and / or structure of the lattice matching layer 200 can be a linear change or a non-linear change. The change in the lattice constant of the lattice matching layer 200 can be a linear change or a non-linear change.

[0055] As Figure 3 shown, in an alternative embodiment, the lattice matching layer 200 includes a seed layer 210. The seed layer 210 is disposed on one side of the diamond substrate 100. The seed layer 210 can be made of aluminum nitride (AlN) material, aluminum gallium nitride (AlGaN) material, or gallium nitride (GaN) material. The thickness of the seed layer 210 is between 1 nm and 10 nm. Optionally, the thickness of the seed layer 210 can be 1 nm, 2 nm, 4 nm, 7 nm, or 10 nm, etc.

[0056] The seed layer 210 can be fabricated by various methods. Optionally, the seed layer 210 can be manufactured by metalorganic chemical vapor deposition (MOCVD). At a relatively low temperature (400°C - 700°C), trimethylaluminum (TMA, C3H9Al) and ammonia (NH3) are used as the aluminum source and nitrogen source respectively, with hydrogen as the carrier gas, to prepare the seed layer 210 in a reaction furnace. By adjusting the pressure, temperature, and gas flow rate of the reaction furnace, a high-quality single-crystal aluminum nitride thin film is grown. Eventually, a high-quality seed layer 210 is fabricated.

[0057] Optionally, the seed layer 210 can be fabricated using atomic layer deposition (ALD). Atomic layer deposition (ALD) is a thin film deposition technique based on the sequential use of gas-phase chemical processes. It is a subclass of chemical vapor deposition. Most ALD reactions use two chemical substances called precursors. These precursors react with the material surface one at a time in a sequential and self-limiting manner. By repeatedly exposing to different precursors, the thin film is slowly deposited. The seed layer 210 can be fabricated by thermal atomic layer deposition (thermal ALD) or by plasma-enhanced atomic layer deposition (PE-ALD). In this embodiment, plasma-enhanced atomic layer deposition (PE-ALD) is used to fabricate the seed layer 210. Before the aluminum nitride growth process begins, the surface of the diamond substrate is cleaned. Optionally, the cleaning can be performed in a hydrogen environment at 1100 °C - 1300 °C. Plasma-enhanced atomic layer deposition (PE-ALD) enables the growth of aluminum nitride thin films at low temperatures between 150 °C and 300 °C. During the preparation of the seed layer 210, the gaseous precursors and oxidants are applied to the substrate in separate pulses, with each pulse adsorbing at most a complete monolayer. Thus, one atomic layer is deposited in each pulse. As the deposition temperature increases, the plasma significantly improves the deposition rate of the aluminum nitride thin film. The preparation of the seed layer 210 can use trimethylaluminum (TMA) or aluminum chloride (AlCl₄) as the aluminum precursor. In this embodiment, using trimethylaluminum (TMA) as the aluminum precursor can achieve a higher deposition rate, and trimethylaluminum (TMA) can reach aluminum saturation at a lower dose, which means more uniform nucleation on the substrate surface in the first deposition cycle and higher crystallinity when growing the aluminum nitride thin film. The preparation of the seed layer 210 can use ammonia (NH₃) as the nitrogen source.

[0058] As Figure 4 shown, in an alternative embodiment, the lattice matching layer 200 includes a buffer layer 220. The buffer layer 220 is made of undoped high-resistivity aluminum nitride. The thickness of the buffer layer 220 is between 0.2 and 2 μm. Optionally, the thickness of the buffer layer 220 can be 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, or 2 μm, etc. Along the direction from the diamond substrate 100 towards the gallium nitride epitaxial layer 300 in the buffer layer 220, the lattice constant of the buffer layer 220 gradually approaches the lattice constant of the aluminum nitride crystal itself until it is the same as the lattice constant of the aluminum nitride itself. That is, the lattice constant of the side of the buffer layer 220 close to the gallium nitride epitaxial layer 300 is equal to the lattice constant of the aluminum nitride itself, reaching 3.11 Å.

[0059] The buffer layer 220 can be fabricated by various methods. Optionally, the buffer layer 220 can be fabricated by methods such as direct nitridation of aluminum, high nitrogen pressure solution growth (HNPSG), hydride vapor phase epitaxy growth (HVPE), metal organic chemical vapor deposition (MOCVD), or physical vapor transport growth (PVT), i.e., any method that can grow single-crystalline aluminum nitride on a substrate can be used to fabricate the buffer layer 220. In this embodiment, the metal organic chemical vapor deposition (MOCVD) method is used to fabricate the buffer layer 220. Trimethylaluminum (TMA, C3H9Al) and ammonia (NH3) are used as the aluminum source and nitrogen source respectively, and hydrogen is used as the carrier gas to fabricate the buffer layer 220 through a reaction furnace. By adjusting the pressure, temperature, and gas flow rate of the reaction furnace, a high-quality single-crystalline aluminum nitride thin film can be grown, thereby fabricating a high-quality buffer layer 220.

[0060] Such as Figure 5As shown, in an optional embodiment, the lattice matching layer 200 includes a transition layer 230. The transition layer 230 may be a gallium-containing nitride material, for example, the transition layer 230 may be aluminum gallium nitride (AlGaN) or indium aluminum gallium nitride (InAlGaN). In this embodiment, the transition layer 230 is aluminum gallium nitride (AlGaN). The thickness of the transition layer 230 is between 0.3 μm and 3 μm. Optionally, the thickness of the transition layer 230 may be 0.3 μm, 0.5 μm, 1 μm, 2 μm or 3 μm. In the transition layer 230, the aluminum content in the aluminum gallium nitride (AlGaN) gradually decreases and the gallium content gradually increases along the direction from the diamond substrate 100 to the gallium nitride epitaxial layer 300. For example, on the side of the transition layer 230 close to the diamond substrate 100, the aluminum content is 100% and the gallium content is 0%. In the process of transitioning from the side of the transition layer 230 close to the diamond substrate 100 to the side of the transition layer 230 close to the gallium nitride epitaxial layer 300, the content of aluminum gradually decreases and the content of gallium gradually increases. Finally, on the side of the transition layer 230 close to the gallium nitride epitaxial layer 300, the content of aluminum is 0% and the content of gallium is 100%. Of course, on the side of the transition layer 230 close to the diamond substrate 100, the content of aluminum can be any content between 20% and 100%. Optionally, on the side of the transition layer 230 close to the diamond substrate 100, the content of aluminum can be 20%, 30%, 50%, 80% or 100%. In the transition layer 230, the composition change from the side close to the diamond substrate 100 to the side close to the gallium nitride epitaxial layer 300 can be a linear change or a nonlinear change, such as a step-like change. The composition change process may be throughout the entire transition layer 230 , or the composition of the transition layer 230 of a certain thickness may change while the composition of the transition layer 230 of other thicknesses may not change.

[0061] In this embodiment, the transition layer 230 can be made by metal organic chemical vapor deposition (MOCVD). Trimethylaluminum (TMA, C3H9Al) can be used as an aluminum source, ammonia (NH3) can be used as a nitrogen source, trimethylgallium (TMG, C3H9Ga) can be used as a gallium source, and hydrogen can be used as a carrier gas. In the process of manufacturing the transition layer 230, the content of aluminum and gallium in the transition layer 230 at the current thickness can be controlled by adjusting the content of trimethylgallium (TMG, C3H9Ga) and trimethylaluminum (TMA, C3H9Al) in the gas source. The high-quality transition layer 230 can be grown by adjusting the pressure, temperature, and gas flow rate of the reactor.

[0062] like Figure 5As shown, in an alternative embodiment, the lattice matching layer 200 includes a transition layer 230, and the transition layer 230 can be made of indium aluminum nitride (InAlN). The thickness of the transition layer 230 is between 0.3 μm and 3 μm. Optionally, the thickness of the transition layer 230 can be 0.3 μm, 0.5 μm, 1 μm, 2 μm, or 3 μm, etc. Along the direction from the diamond substrate 100 to the gallium nitride epitaxial layer 300 in the transition layer 230, the content of aluminum in the indium aluminum nitride (InAlN) gradually approaches 83%, and the content of indium gradually approaches 17%. For example, on the side of the transition layer 230 close to the diamond substrate 100, the content of aluminum is 50% and the content of indium is 50%. During the transition from the side of the transition layer 230 close to the diamond substrate 100 to the side of the transition layer 230 close to the gallium nitride epitaxial layer 300, the content of aluminum gradually increases and the content of indium gradually decreases. Finally, on the side of the transition layer 230 close to the gallium nitride epitaxial layer 300, the content of aluminum is 83% and the content of indium is 17%. From the side of the transition layer 230 close to the diamond substrate 100 to the side close to the gallium nitride epitaxial layer 300, the component change therein can be a linear change or a non-linear change, such as a stepwise change. The process of component change can penetrate the entire transition layer 230, or the component change can occur in a transition layer 230 of a certain thickness while the components of the transition layer 230 of other thicknesses do not change. In this embodiment, the transition layer 230 can be fabricated by metalorganic chemical vapor deposition (MOCVD). Trimethylaluminum (TMA, C3H9Al) can be used as the aluminum source, ammonia gas (NH3) can be used as the nitrogen source, and trimethylindium (TMI, C3H9In) can be used as the indium source, with hydrogen as the carrier gas. During the manufacturing process of the transition layer 230, the content of aluminum and indium in the transition layer 230 at the current thickness can be controlled by regulating the content of trimethylindium (TMI, C3H9In) and trimethylaluminum (TMA, C3H9Al) in the gas source. By adjusting the pressure, temperature, and gas flow rate of the reaction furnace, a high-quality transition layer 230 can be grown.

[0063] As Figure 6 shown, in an alternative embodiment, the lattice matching layer 200 includes a superlattice structure layer 240. The superlattice structure layer 240 includes a plurality of superlattice layers. A first superlattice layer, a second superlattice layer, ······ a first n superlattice layer are sequentially stacked from the diamond substrate 100 side to the gallium nitride epitaxial layer 300 side. The stacked structure of the superlattice structure layer 240 can effectively reduce the stress generated by different thermal expansion coefficients between materials, thereby reducing or eliminating the wafer warping or cracking caused by stress. The superlattice structure layer 240 is aluminum indium gallium nitride, and each superlattice layer is also aluminum indium gallium nitride. The component content of at least one of the three elements of aluminum, indium, and gallium in adjacent superlattice layers is different. For example, the composition of the first superlattice layer is Alx1 In y1 Ga (1-x1-y1) N, the composition of the second superlattice layer is Al x2 In y2 Ga (1-x2-y2) N, the composition of the third superlattice layer is Al x3 In y3 Ga (1-x3-y3) N, then x1≠x2 and / or y1≠y2 and x2≠x3 and / or y2≠y3. And so on, the composition of the (n - 1)-th superlattice layer is Al xn-1 In yn-1 Ga (1-xn-1-yn-1) N, the composition of the n-th superlattice layer is Al xn In yn Ga (1-xn-yn)N, xn-1 ≠ xn and / or yn-1 ≠ yn. The value of n is greater than or equal to 6 and less than or equal to 120. That is, the superlattice structure layer 240 includes 6 to 120 superlattice layers. Optionally, the superlattice structure layer 240 may include 6 superlattice layers, 20 superlattice layers, 60 superlattice layers, 100 superlattice layers, or 120 superlattice layers. The thickness of a single superlattice layer is between 1 nm and 20 nm, including 1 nm and 20 nm. Optionally, the thickness of a single superlattice layer may be 1 nm, 3 nm, 7 nm, 14 nm, or 20 nm. Optionally, in the superlattice structure layer 240, the aluminum content in the superlattice layer closer to the diamond substrate 100 is greater than the aluminum content in the superlattice layer closer to the gallium nitride epitaxial layer 300. For example, the aluminum content in the first superlattice layer is greater than the aluminum content in the second superlattice layer, the aluminum content in the second superlattice layer is greater than the aluminum content in the third superlattice layer... the aluminum content in the (n - 1)th superlattice layer is greater than the aluminum content in the nth superlattice layer. Optionally, in the superlattice structure layer 240, the gallium content in the superlattice layer closer to the diamond substrate 100 is less than the gallium content in the superlattice layer closer to the gallium nitride epitaxial layer 300. For example, the gallium content in the first superlattice layer is less than the gallium content in the second superlattice layer, the gallium content in the second superlattice layer is less than the gallium content in the third superlattice layer... the gallium content in the (n - 1)th superlattice layer is less than the gallium content in the nth superlattice layer. Optionally, the component contents of the three elements of aluminum, indium, and gallium at different thickness positions in a single superlattice layer are different. For example, in the first superlattice layer, the aluminum content on the side closer to the diamond substrate 100 is greater than the aluminum content on the side farther from the diamond substrate 100, and the gallium content on the side closer to the diamond substrate 100 is less than the gallium content on the side farther from the diamond substrate 100. Another example is that in the nth superlattice layer, the aluminum content on the side closer to the gallium nitride epitaxial layer 300 is less than the aluminum content on the side farther from the gallium nitride epitaxial layer 300, and the gallium content on the side closer to the gallium nitride epitaxial layer 300 is greater than the gallium content on the side farther from the gallium nitride epitaxial layer 300.

[0064] In this embodiment, the superlattice structure layer 240 can be fabricated by metalorganic chemical vapor deposition (MOCVD). Trimethylaluminum (TMA, C3H9Al) can be used as the aluminum source, trimethylgallium (TMG, C3H9Ga) as the gallium source, ammonia (NH3) as the nitrogen source, and trimethylindium (TMI, C3H9In) as the indium source, with hydrogen as the carrier gas. During the fabrication of the superlattice structure layer 240, the component contents of aluminum and gallium in the superlattice layer can be adjusted by controlling the amounts of the aluminum-containing gas source and the gallium-containing gas source. For example, the component content of aluminum in the superlattice layer can be increased by increasing the content of trimethylaluminum (TMA, C3H9Al) in the gas source. Another example is that the component content of gallium in the superlattice layer can be decreased by reducing the content of trimethylgallium (TMG, C3H9Ga) in the gas source. Additionally, a high-quality superlattice structure layer 240 can be grown by adjusting the pressure, temperature, and gas flow rate of the reaction furnace.

[0065] As Figures 2 to 7 shown, in an alternative embodiment, the lattice-matching layer 200 includes two, three, or four of the seed layer 210, the buffer layer 220, the transition layer 230, and the superlattice structure layer 240.

[0066] Optionally, the lattice-matching layer 200 can include any two of the seed layer 210, the buffer layer 220, the transition layer 230, and the superlattice structure layer 240. For example, the lattice-matching layer 200 can include the seed layer 210 and the buffer layer 220. The seed layer 210 is disposed on the side of the diamond substrate 100 close to the gallium nitride epitaxial layer 300, and the buffer layer 220 is disposed on the side of the seed layer 210 close to the gallium nitride epitaxial layer 300. Another example is that the lattice-matching layer 200 can include the buffer layer 220 and the transition layer 230. The buffer layer 220 is disposed on the side of the diamond substrate 100 close to the gallium nitride epitaxial layer 300, and the transition layer 230 is disposed on the side of the buffer layer 220 close to the gallium nitride epitaxial layer 300. Another example is that the lattice-matching layer 200 can include the buffer layer 220 and the superlattice structure layer 240. The buffer layer 220 is disposed on the side of the diamond substrate 100 close to the gallium nitride epitaxial layer 300, and the superlattice structure layer 240 is disposed on the side of the buffer layer 220 close to the gallium nitride epitaxial layer 300.

[0067] Optionally, the lattice matching layer 200 includes any three of a seed layer 210, a buffer layer 220, a transition layer 230, and a superlattice structure layer 240. For example, the lattice matching layer 200 may include the seed layer 210, the buffer layer 220, and the transition layer 230. The seed layer 210 is disposed on a side of the diamond substrate 100 close to the gallium nitride epitaxial layer 300, the buffer layer 220 is disposed on a side of the seed layer 210 close to the gallium nitride epitaxial layer 300, and the transition layer 230 is disposed on a side of the buffer layer 220 close to the gallium nitride epitaxial layer 300. As another example, the lattice matching layer 200 may include the seed layer 210, the buffer layer 220, and the superlattice structure layer 240. The seed layer 210 is disposed on a side of the diamond substrate 100 close to the gallium nitride epitaxial layer 300, the buffer layer 220 is disposed on a side of the seed layer 210 close to the gallium nitride epitaxial layer 300, and the superlattice structure layer 240 is disposed on a side of the buffer layer 220 close to the gallium nitride epitaxial layer 300.

[0068] Optionally, the lattice matching layer 200 may include the seed layer 210, the buffer layer 220, the transition layer 230, and the superlattice structure layer 240. For example, the seed layer 210 is disposed on a side of the diamond substrate 100 close to the gallium nitride epitaxial layer 300, the buffer layer 220 is disposed on a side of the seed layer 210 close to the gallium nitride epitaxial layer 300, the superlattice structure layer 240 is disposed on a side of the buffer layer 220 close to the gallium nitride epitaxial layer 300, and the transition layer 230 is disposed on a side of the superlattice structure layer 240 close to the gallium nitride epitaxial layer 300. As another example, the seed layer 210 is disposed on a side of the diamond substrate 100 close to the gallium nitride epitaxial layer 300, the buffer layer 220 is disposed on a side of the seed layer 210 close to the gallium nitride epitaxial layer 300, the transition layer 230 is disposed on a side of the buffer layer 220 close to the gallium nitride epitaxial layer 300, and the superlattice structure layer 240 is disposed on a side of the transition layer 230 close to the gallium nitride epitaxial layer 300.

[0069] As Figure 8 shown, in an alternative embodiment, the gallium nitride epitaxial layer 300 includes a channel layer 310, a barrier layer 330, a cap layer 340, and a first passivation layer 350.

[0070] The channel layer 310 is disposed on a side of the lattice-matching layer 200 away from the diamond substrate 100. The channel layer 310 is made of gallium nitride, and its thickness is 0.5 μm to 5 μm. Optionally, the thickness of the channel layer 310 can be 0.5 μm, 1 μm, 2 μm, 4 μm, or 5 μm. The channel layer 310 can be fabricated by methods such as metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In this embodiment, the channel layer 310 is fabricated by metal-organic chemical vapor deposition (MOCVD). Trimethylgallium (TMG, C3H9Ga) is used as the gallium source, ammonia (NH3) is used as the nitrogen source, and hydrogen is used as the carrier gas. This method can control the synthesis of an atomically thin film, i.e., a novel nanomaterial film. It can also be made into a large-area uniform film, which is easy to industrialize. It can also achieve pure material growth. Since it does not use liquid containers and low-temperature growth technologies, the pollution source is minimized, and the material purity is improved by an order of magnitude compared to other semiconductor material growth technologies.

[0071] The barrier layer 330 is disposed on a side of the channel layer 310 away from the lattice-matching layer 200. The barrier layer 330 can be aluminum nitride, indium nitride, indium aluminum nitride, aluminum gallium nitride, indium aluminum gallium nitride, or other binary, ternary, or quaternary nitrides. The thickness of the barrier layer 330 is 3 nm to 50 nm. Optionally, the thickness of the barrier layer 330 can be 3 nm, 5 nm, 10 nm, 20 nm, or 50 nm, etc. The barrier layer 330 can be fabricated by methods such as metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In this embodiment, the barrier layer 330 is fabricated by metal-organic chemical vapor deposition (MOCVD). The barrier layer 330 can supply electrons to the channel layer 310.

[0072] Optionally, an isolation layer 320 is disposed between the barrier layer 330 and the channel layer 310. The isolation layer 320 is made of aluminum nitride, and the thickness of the isolation layer 320 is 5 Å - 20 Å. Optionally, the thickness of the isolation layer 320 can be 5 Å, 7 Å, 10 Å, 15 Å, or 20 Å, etc. The isolation layer 320 can be fabricated by methods such as metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). In this embodiment, the isolation layer 320 is fabricated by metal-organic chemical vapor deposition (MOCVD). The isolation layer 320 can restrict the movement of electrons in the thickness direction to increase the density of the two-dimensional electron gas.

[0073] The cap layer 340 is disposed on a side of the barrier layer 330 away from the channel layer 310. The cap layer 340 is made of gallium nitride, and the thickness of the cap layer 340 is 2 nm to 10 nm. Optionally, the thickness of the cap layer 340 can be 2 nm, 4 nm, 5 nm, 8 nm, 10 nm, etc. The first passivation layer 350 is disposed on a side of the cap layer 340 away from the barrier layer 330. The first passivation layer 350 is made of silicon nitride. The thickness of the first passivation layer 350 is 2 nm to 20 nm. Optionally, the thickness of the first passivation layer 350 can be 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, etc. The first passivation layer 350 can prevent the oxidation of the barrier layer and reduce the resistance of the source-drain ohmic contact.

[0074] The present application also discloses a method for manufacturing a gallium nitride epitaxial wafer for manufacturing the above-mentioned gallium nitride epitaxial wafer, which includes:

[0075] Manufacture a lattice-matched layer 200 on the single-crystal diamond substrate 100;

[0076] Manufacture a gallium nitride epitaxial layer 300 on a side of the lattice-matched layer 200 away from the diamond substrate 100.

[0077] The lattice-matched layer 200 includes one or two or three or four of the seed layer 210, the buffer layer 220, the transition layer 230, and the superlattice structure layer 240.

[0078] As Figure 9 shown, the present application also discloses a semiconductor device, which includes the above-mentioned gallium nitride epitaxial wafer.

[0079] In an alternative embodiment, the semiconductor device is a high electron mobility transistor (HEMT). The high electron mobility transistor includes a diamond substrate 100, a lattice-matched layer 200, a gallium nitride epitaxial layer 300, a second passivation layer 410 covering the gallium nitride epitaxial layer 300, a first metal layer 460 disposed on the second passivation layer 410, a metal interlayer dielectric layer 420 covering the first metal layer 460, and a second metal layer 470 disposed on the metal interlayer dielectric layer 420.

[0080] The high electron mobility transistor includes a source 430 and a drain 440. The source 430 and the drain 440 can be directly fabricated on the surface of the cap layer 340, or grooves (not shown in the figure) can be etched in the gallium nitride epitaxial layer 300 first, and then the source 430 and the drain 440 can be fabricated in the grooves. The source 430 and the drain 440 can form an alloy through high-temperature annealing by a combination of several metals, which can reduce the contact resistance. These metals include Ti, Al, Ni, and Au, etc. The source 430 and the drain 440 can be fabricated by depositing layer by layer onto the wafer through metal evaporation or sputtering. The source 430 and the drain 440 are connected through a first metal layer 460 and a second metal layer 470. Optionally, according to actual requirements, the semiconductor device can be provided with more metal layers, insulating layers, or other dielectric layers, etc.

[0081] The high electron mobility transistor further includes a gate 450. The gate 450 can be directly disposed on the barrier layer 330. Optionally, an insulating layer (not shown in the figure) can be provided between the gate 450 and the gallium nitride epitaxial layer 300, and then the gate 450 is provided on the insulating layer to form a MIS (metal-insulator-semiconductor) structure. The insulating layer can be made of materials such as silicon nitride, silicon dioxide, or aluminum oxide, etc. The gate 450 can be composed of metals such as Ni, Au, Pt, Ti, Al, etc., and is deposited layer by layer onto the wafer through metal evaporation or sputtering.

[0082] Optionally, the back surface of the high electron mobility transistor can be thinned and polished. The back surface of the diamond substrate 100 can also be etched with back holes to form back holes 480. For example, back holes can be etched by laser at the position on the back surface of the diamond substrate 100 corresponding to the source 430, and the etched back holes 480 communicate the back surface of the diamond substrate 100 with the source 430. Then, a back surface metallization process can be implemented on the back surface of the diamond substrate 100 to make the back surface metal 490 cover the back surface of the diamond substrate 100 and the hole walls of the back holes 480. The back surface metal 490 can be a metal such as Au or Al. The thickness of the back surface metal 490 is 1μm to 7μm. Optionally, the thickness of the back surface metal 490 can be 1μm, 2μm, 3μm, 5μm, or 7μm, etc.

[0083] Optionally, other components can also be included in the semiconductor device, such as thin film resistors, capacitors, inductors, etc. A variety of components can be connected through metal wires to form a monolithic integrated circuit.

[0084] Those skilled in the art will readily conceive of other embodiments of the present specification after considering the specification and practicing the invention claimed herein. This specification is intended to cover any variations, uses, or adaptations of the present specification, which follow the general principles of the present specification and include common general knowledge or conventional technical means in the technical field not claimed in the present specification. The specification and examples are only to be regarded as exemplary, and the true scope and spirit of the present specification are pointed out by the following claims.

[0085] It should be understood that the present specification is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present specification is only limited by the appended claims.

[0086] The above are only the preferred embodiments of the present specification and are not intended to limit the present specification. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present specification shall be included within the scope of protection of the present specification.

Claims

1. A gallium nitride epitaxial wafer, characterized in that, Comprising: Single-crystal diamond substrate; Lattice-matching layer, which is disposed on one side of the diamond substrate; Gallium nitride epitaxial layer, which is disposed on the side of the lattice-matching layer away from the diamond substrate; The lattice constant of the side of the lattice-matching layer close to the gallium nitride epitaxial layer matches the lattice constant of the gallium nitride material; The lattice-matching layer includes: Buffer layer, the thickness of the buffer layer is greater than or equal to 0.2 μm and less than or equal to 2 μm; the buffer layer is made of undoped high-resistance aluminum nitride material; Transition layer, which is disposed on the side of the buffer layer away from the single-crystal diamond substrate, the thickness of the transition layer is greater than or equal to 0.3 μm and less than or equal to 3 μm; the transition layer is made of indium aluminum nitride material, and from the side close to the diamond substrate to the side close to the gallium nitride epitaxial layer, the content of indium gradually decreases to 17% and the content of aluminum gradually increases to 83%; Superlattice structure layer, which is disposed on the side of the transition layer away from the buffer layer, the superlattice structure layer includes a plurality of sequentially stacked first superlattice layers, second superlattice layers, ······ nth superlattice layers; the superlattice structure layer is aluminum indium gallium nitride, and the component content of at least one of the three elements of aluminum, indium, and gallium in adjacent superlattice layers is different; the aluminum content on the side of the superlattice structure layer close to the diamond substrate is greater than the aluminum content on the side close to the gallium nitride epitaxial layer.

2. The gallium nitride epitaxial wafer according to claim 1, wherein The lattice-matching layer includes a seed layer, the thickness of the seed layer is greater than or equal to 1 nm and less than or equal to 10 nm; the seed layer is made of aluminum nitride material.

3. A method for manufacturing a gallium nitride epitaxial wafer, which is used to manufacture the gallium nitride epitaxial wafer according to any one of claims 1-2, characterized in that, Comprising: Manufacturing a lattice-matching layer on a single-crystal diamond substrate; Manufacturing a gallium nitride epitaxial layer on the side of the lattice-matching layer away from the diamond substrate; The lattice constant of the side of the lattice-matching layer close to the gallium nitride epitaxial layer matches the lattice constant of the gallium nitride material; The lattice-matching layer includes: Seed layer, which is located on one side of the single-crystal diamond substrate; Buffer layer, which is located on the side of the seed layer away from the single-crystal diamond substrate, the thickness of the buffer layer is greater than or equal to 0.2 μm and less than or equal to 2 μm; the buffer layer is made of undoped high-resistance aluminum nitride material; Transition layer, which is disposed on the side of the buffer layer away from the seed layer, the thickness of the transition layer is greater than or equal to 0.3 μm and less than or equal to 3 μm; the transition layer is made of indium aluminum nitride material, and from the side close to the diamond substrate to the side close to the gallium nitride epitaxial layer, the content of indium gradually approaches 17% and the content of aluminum gradually approaches 83%; A superlattice structure layer is disposed on a side of the transition layer away from the buffer layer. The superlattice structure layer includes a plurality of first superlattice layers, second superlattice layers, ······, nth superlattice layers stacked in sequence; the superlattice structure layer is an aluminum indium gallium nitride, and the component contents of at least one of the three elements of aluminum, indium, and gallium in adjacent superlattice layers are different; the aluminum content on a side of the superlattice structure layer close to the diamond substrate is greater than the aluminum content on a side close to the gallium nitride epitaxial layer.

4. A semiconductor device, characterized in that, The semiconductor device includes the gallium nitride epitaxial wafer according to any one of claims 1-2.

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