Nitride semiconductor epitaxial substrate

Abstract

The invention discloses a nitride semiconductor epitaxial substrate, which comprises a substrate, the substrate is a single-layer Si substrate or a composite substrate of which the surface is made of a monocrystalline silicon material, the nitride semiconductor epitaxial substrate also comprises a 3C-SiC transition layer on the Si substrate and an aluminum-containing nitride nucleating layer on the 3C-SiC transition layer, and the aluminum-containing nitride nucleating layer is prepared by adopting a sputter method. The epitaxial substrate can be used for improving the crystal quality of a nitride epitaxial layer growing on the epitaxial substrate, and meanwhile, the time required by epitaxial growth can be saved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and particularly relates to a nitride semiconductor epitaxial substrate. Background Art

[0002] Nitride semiconductors, as a new type of wide-bandgap semiconductors, can be used to fabricate high-efficiency short-wavelength optoelectronic devices, such as blue, white, or ultraviolet LEDs, due to their direct bandgap nature. These devices are applied in many fields, including solid-state lighting, backlight displays, ultraviolet disinfection, etc. In addition, compared with traditional silicon-based devices, nitride semiconductors have a high breakdown electric field, are more energy-efficient, have more stable physical and chemical properties, can operate at higher ambient temperatures, have a higher switching speed, and can reduce the volume and weight of application systems. They can be used to fabricate power devices for a wide range of applications, such as various household appliances, electric vehicles, new energy power generation like solar and wind energy, electric vehicles, robots, intelligent manufacturing industries, and large data processing centers. Due to the high light transmittance of sapphire substrates and the high crystal quality of epitaxy, sapphire substrates are widely used in nitride LED epitaxy. Currently, nitride power devices mainly grow nitride epitaxial structures on silicon substrates. Growing epitaxy on large-size silicon substrates can achieve the best cost performance. However, directly growing gallium nitride on a silicon substrate will form a silicon-gallium alloy at high temperatures, making it impossible to grow the required high-quality epitaxial thin film. Therefore, generally, a low-temperature aluminum nitride nucleation layer is first grown, and then the temperature is raised to continue growing other epitaxial structures. Due to the presence of deposits generated during the previous growth process in the growth chamber, the cleanliness of the growth chamber has a significant impact on the crystal quality of the grown low-temperature aluminum nitride nucleation layer, and thus has a significant impact on the crystal quality and stress control of the subsequent grown epitaxial thin film. Therefore, in order to improve the stability of epitaxial growth, the industry has developed equipment and processes for high-temperature cleaning of the growth chamber with chlorine gas. After each growth of epitaxial material, chlorine gas is introduced into the growth chamber for high-temperature baking and cleaning to improve production stability. However, the addition of the high-temperature cleaning design using chlorine gas makes the equipment itself more expensive. At the same time, the corrosion of chlorine gas on accessories at high temperatures reduces the lifespan of the accessories and increases the maintenance frequency, further increasing the production cost. The nitride LED epitaxy uses a sapphire substrate with a sputter AlN nucleation layer to grow nitride epitaxy, which is currently the mainstream process in the industry. Growing a sputter AlN nucleation layer on a sapphire substrate can significantly improve the crystal quality of the nitride epitaxial layer compared to using an epitaxially grown nucleation layer, thus improving the LED light efficiency. At the same time, since the cooling and heating processes of the nucleation layer with a relatively low deposition growth temperature are eliminated, the epitaxial growth time is reduced, and the production cost can be saved. If a silicon substrate with a similar sputter AlN is used for nitride epitaxial growth, since the surface of the silicon substrate is not directly in contact with the growth chamber atmosphere as the surface for continuous growth, the requirement for the cleanliness of the growth chamber can be reduced, the high-temperature chlorine gas cleaning step in the growth chamber can be eliminated or the cleaning frequency can be reduced, improving the stability of the growth process. At the same time, since there is no need to deposit a nucleation layer with a relatively low growth temperature, the time for cooling and heating is saved, so the cost of epitaxial growth can be reduced. However, when the sputter AlN nucleation layer is directly used on a silicon substrate, the crystal quality is not significantly improved compared to the epitaxially grown AlN nucleation layer.Previously, Nishino et al. described a method for growing high-quality silicon-based 3C-SiC in the non-patent literature Applied Physics Letters 42, 460 (1983). T. Takeuchi, H. Amano et al. reported the experimental results of successfully growing single-crystal GaN epitaxial layers using 3C-SiC / Si substrates in the non-patent literature Journal of Crystal Growth 115 (1991) 634 - 638. Y. H. Zhu, T. Egawa et al. introduced the experimental results of successfully growing nitride LED epitaxial structures on 3C-SiC / Si substrates in the non-patent literature JOURNAL OF APPLIED PHYSICS 106, 124506 (2009). However, in the above reports, the AlN nucleation layers on the 3C-SiC / Si substrates were all prepared by epitaxial growth methods, and no sputter AlN nucleation layer was proposed. Summary of the Invention

[0003] In view of the problems in the background art, the present invention provides 1. A nitride semiconductor epitaxial substrate, including a substrate, characterized in that the substrate is a single-layer Si substrate or a composite substrate with a single-crystalline silicon material on its surface, and further includes a 3C-SiC transition layer on the Si substrate, and an aluminum-containing nitride nucleation layer on the 3C-SiC transition layer, and the aluminum-containing nitride nucleation layer is prepared by sputtering.

[0004] The epitaxial substrate can be used to improve the crystal quality of the nitride epitaxial layer grown thereon, and at the same time can save the time required for epitaxial growth. By providing a high-quality 3C-SiC transition layer, and due to the relatively smaller lattice difference between 3C-SiC and AlN, compared with directly depositing a sputter AlN nucleation layer on a Si substrate, the quality of the aluminum-containing nitride nucleation layer can be improved, thereby improving the crystal quality of the nitride epitaxial layer grown thereon. At the same time, the stability of epitaxial growth can be improved, and the time required for epitaxial growth can be saved. Compared with using a 3C-SiC composite substrate on a Si substrate, the growth time of the epitaxial process can be saved by sputtering the nucleation layer, and at the same time, the crystal quality can be improved. Moreover, when simply using a 3C-SiC composite substrate on a Si substrate, since the extremely thin 3C-SiC layer is difficult to completely cover the surface of the silicon substrate, this composite substrate is similar to the silicon substrate, and the requirement for the cleanliness of the cavity is still relatively high. If a thicker 3C-SiC epitaxial layer is to be grown continuously, the required growth time, the difficulty of stress control of the 3C-SiC epitaxial layer, and the cost of the high-temperature epitaxial process will increase significantly compared with the sputter AlN process. By providing a 3C-SiC layer, the quality of the aluminum-containing nitride nucleation layer can be improved, thereby improving the crystal quality of the nitride epitaxial layer grown thereon. At the same time, the stability of epitaxial growth can be improved, and the time required for epitaxial growth can be saved.

[0005] As an alternative embodiment of the present invention, the composite substrate with a single-crystalline silicon material surface can be a SOI substrate, a single-layer Si substrate, or the single-crystalline silicon material on the surface of the composite substrate is the 111 plane or the 100 plane. As a preferred embodiment of the present invention, the single-crystalline silicon material on the surface of the single-layer Si substrate or the composite substrate adopts the 111 plane.

[0006] As an alternative embodiment of the present invention, the 3C-SiC transition layer is prepared by chemical vapor deposition, atomic layer deposition process, or high-temperature carbonization process. Such as MOCVD, LPCVD, PECVD, ALD, etc. As a preferred embodiment of the present invention, the 3C-SiC transition layer is prepared by adopting the LPCVD process.

[0007] As an alternative embodiment of the present invention, when preparing the 3C-SiC transition layer by chemical vapor deposition method, one or several C-containing gas sources (such as methane, ethylene, acetylene, propane, C4H 10 , C6H 12 , trimethylaluminum or triethylaluminum, etc.) are used to react with a Si-containing gas source (such as silane, SiH3Cl, SiH2Cl2) to generate.

[0008] As an alternative embodiment of the present invention, when preparing the 3C-SiC transition layer by chemical vapor deposition method, a C and Si-containing gas source (such as monomethylsilane) is used to react at high temperature to generate.

[0009] As an alternative embodiment of the present invention, when preparing the 3C-SiC transition layer by chemical vapor deposition method, one or several of the above-mentioned carbon-containing gas sources (such as methane, ethylene, acetylene, propane, C4H 10， C6H 12 , trimethylaluminum or triethylaluminum, etc.) are used to carbonize the surface of the Si substrate at high temperature, and the 3C-SiC layer can be continuously epitaxially grown by the above two methods as needed.

[0010] As an alternative embodiment of the present invention, the reaction temperature is 700 - 1400 °C when preparing the 3C-SiC transition layer by chemical vapor deposition method.

[0011] As an alternative embodiment of the present invention, the thickness of the 3C-SiC transition layer is 0.5 - 2000 nm. As a preferred embodiment of the present invention, the C-SiC transition layer is an ultra-thin transition layer with a thickness of 0.5 - 15 nm.

[0012] As an alternative embodiment of the present invention, the aluminum nitride-containing nucleation layer can be an Al x Ga y In (1-x-y) N alloy, where 0 < x ≤ 1, 0 ≤ y ≤ 1, the thickness of the aluminum nitride-containing nucleation layer is 10 - 300 nm, and the aluminum nitride-containing nucleation layer preferably uses AlN; as an alternative embodiment of the present invention, B element can also be doped into the alloy.

[0013] As an alternative embodiment of the present invention, the aluminum nitride-containing nucleation layer can be a single-layer Al x GayIn (1-x-y) N alloy, or a multi-layer AlGaInN alloy with different compositions, and B element can also be doped into the alloy.

[0014] As an alternative embodiment of the present invention, the aluminum nitride-containing nucleation layer is prepared by sputtering process, and the crystal quality of the nucleation layer is improved by high-temperature annealing process after sputtering.

[0015] Compared with the prior art, the present invention provides a nitride semiconductor epitaxial substrate, which has the following beneficial effects:

[0016] By setting a high-quality 3C-SiC transition layer, and due to the relatively smaller lattice difference between 3C-SiC and AlN, compared with directly depositing a sputter AlN nucleation layer on a Si substrate, the quality of the aluminum-containing nitride nucleation layer can be improved, thereby improving the crystal quality of the nitride epitaxial layer grown thereon. At the same time, the stability of epitaxial growth can be improved, and the time required for epitaxial growth can be saved. Compared with using a 3C-SiC composite substrate on a Si substrate, the epitaxial process growth time can be saved by the sputter nucleation layer, and the crystal quality can be improved simultaneously. Description of the Drawings

[0017] Figure 1 Schematic diagram of the epitaxial wafer structure of Embodiment 1 of the present invention.

[0018] Figures 2a to 2c Flow chart for fabricating the epitaxial wafer of Embodiment 1.

[0019] Figure 3 Schematic diagram of the epitaxial wafer structure of Embodiment 2 of the present invention.

[0020] Figures 4a to 4c Flow chart for fabricating the epitaxial wafer of Embodiment 2.

[0021] Wherein: 10 - substrate; 101 - silicon substrate; 102 - 3C-SiC transition layer; 103 - aluminum-containing nitride nucleation layer; 11 - nitride epitaxial layer; 20 - substrate; 201 - SOI substrate 202 - 3C-SiC transition layer 203 - aluminum-containing nitride nucleation layer; 21 - buffer layer; 22 - channel layer; 23 - barrier layer; 24 - p-type GaN cap layer. Detailed Embodiments

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be implemented in different forms, and the present invention should not be construed as being limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the invention and its practical applications, so that other technicians in the art can understand the embodiments of the present invention and various other modifications based on the core technical content of the present invention.

[0023] Embodiment 1

[0024] In the first exemplary embodiment, referring to Figure 1 , the nitride semiconductor epitaxial substrate 10 provided in this embodiment includes a silicon substrate 101, and a 3C-SiC transition layer 102 formed sequentially on the silicon substrate 101, and an aluminum-containing nitride nucleation layer 103 on the transition layer 102. A high-quality nitride epitaxial layer 11 can be continuously grown on the substrate 10.

[0025] The substrate 10 of this embodiment includes a lower silicon material layer 101 with a thickness of 1000 μm, a diameter of 150 mm, and a crystal plane of (111); the middle transition layer 102 is a 3C-SiC layer with a thickness of 3 nm; the upper aluminum nitride-containing nucleation layer 103 is AlN with a thickness of 40 nm. The nitride epitaxial layer 11 is GaN with a thickness of 1000 nm.

[0026] Referring to Figures 2a - 2c As shown, this embodiment provides the preparation process flow of the nitride semiconductor epitaxial substrate and epitaxy.

[0027] Step 1, as Figure 2a shown, provide a silicon substrate 101 with a thickness of 1000 microns, a diameter of 150 mm, and a crystal plane of (111). Place the substrate into the LPCVD equipment cavity, and introduce a mixed gas of H2 and a carbon source-containing gas into the cavity. In this embodiment, propane is introduced, and the volume ratio of propane in the mixed gas is 1%. While introducing the mixed gas, quickly heat the cavity to 1200 °C to carbonize the silicon wafer surface, forming an extremely thin 3C-SiC layer with a thickness of about 5 nm. Using the LPCVD process, substrates can be processed in large quantities (about 200 wafers can be processed per single-tube process each time), improving production capacity and reducing costs.

[0028] Step 2, as Figure 2b shown, continue to deposit the aluminum nitride-containing nucleation layer 103 on the substrate, and the deposition process is the sputter process. In this embodiment, the sputter RF power is 800 W, an aluminum target with a purity higher than 5N is used, a mixed gas of 10 sccm of nitrogen and argon is introduced as the sputter gas, the nitrogen flow ratio is 40%, the sputter cavity pressure is 1.33 Pa, and the substrate temperature is 600 °C. In this embodiment, the aluminum nitride-containing nucleation layer is an AlN nucleation layer with a thickness of 30 nm. Each existing mass-production Sputter device can process about 10,000 6-inch substrates per month. Compared with using expensive MOCVD equipment to grow the nucleation layer, it has higher processing capacity and lower cost.

[0029] Step 3, as Figure 2c shown, place the substrate 10 deposited with the AlN nucleation layer 103 into the growth cavity of a metalorganic chemical vapor deposition (MOCVD) equipment, introduce ammonia, trimethylgallium, and the carrier gas H2, and continue to grow a 1000 nm GaN epitaxial layer.

[0030] Embodiment 2

[0031] Referring to Figure 3, the nitride semiconductor epitaxial substrate 20 provided in this embodiment includes an SOI substrate 201, and a 3C-SiC transition layer 202 formed sequentially on the SOI substrate 201, and an aluminum-containing nitride nucleation layer 203 on the transition layer 202. A high-quality nitride epitaxial layer can be continuously grown on this substrate 20.

[0032] The SOI substrate 201 in this embodiment has a diameter of 150 mm, includes an upper silicon material layer of 1 μm with a crystal plane of (111); a middle SiO2 insulating material layer with a thickness of 500 nm, and a lower silicon material layer of (111) with a thickness of 990 μm. The middle transition layer 202 is a 3C-SiC layer with a thickness of 1000 nm; the upper aluminum-containing nitride nucleation layer 203 is AlN with a thickness of 40 nm. Above the substrate 20 on which the AlN nucleation layer 203 is deposited, a nitride high electron mobility transistor (HEMT) epitaxial structure is continuously grown, including a buffer layer 21, a channel layer 22, a barrier layer 23, and a p-type GaN cap layer 24. The buffer layer 21 can include a single layer or a multi-layer stack structure of AlN, AlGaN, GaN, an AlN / GaN, AlN / AlGaN, AlGaN / GaN superlattice structure, or a combined structure including the above structures, and the thickness is generally 0.5 - 7 μm. The channel layer 22 is generally made of GaN material with a thickness of 20 - 1000 nm. The barrier layer 23 can include an AlGaN layer, an AlN layer, AlInN, AlInGaN, or a multiple stack of the above material layers, with a thickness of 1 - 30 nm. The p-type GaN layer 24 has a thickness of 10 - 200 nm.

[0033] Refer to Figures 4a - 4c As shown, this embodiment provides the preparation process flow of the nitride semiconductor epitaxial substrate and epitaxy.

[0034] Step 1, as Figure 4a As shown, provide an SOI substrate 201 with a diameter of 150 mm, including an upper silicon material layer of 1 μm, a middle SiO2 insulating material layer with a thickness of 500 nm, and a lower silicon material layer with a thickness of 990 μm.

[0035] Grow a 3C-SiC middle transition layer 202 on this substrate. Place the substrate in the LPCVD equipment cavity, and introduce a mixed gas of H2 and a carbon source-containing gas into the cavity. In this embodiment, propane is introduced, and the volume ratio of propane in the mixed gas is 1%. While introducing the mixed gas, quickly heat the cavity to 1200 °C to carbonize the silicon wafer surface to form an extremely thin 3C-SiC layer with a thickness of about 5 nm. Introduce SiH2Cl2 gas and continue to grow a 3C-SiC layer with a thickness of 1000 nm.

[0036] Step 2, as Figure 4bAs shown, an aluminum nitride-containing nucleation layer 103 is continuously deposited on the substrate, and the deposition process is a sputter process. In this embodiment, the aluminum nitride-containing nucleation layer is an AlN nucleation layer with a thickness of 40 nm, and the deposition process conditions are the same as those in Embodiment 1.

[0037] Step 3, as Figure 4c shown, the substrate 20 deposited with the AlN nucleation layer 203 is placed in the growth chamber of a metalorganic chemical vapor deposition (MOCVD) apparatus to continuously grow a nitride high electron mobility transistor epitaxial structure. The buffer layer 21 includes a 100-nm AlN layer, a 50-nm AlGaN layer, and a 3000-nm AlN / GaN superlattice structure. A 300-nm GaN channel layer 22, a 15-nm Al 0.25 Ga 0.75 GaN barrier layer 23, and an 80-nm p-type GaN cap layer 24 are sequentially grown above the buffer layer 21.

[0038] As described above, the above are only the specific implementation manners of the embodiments of the present invention, but the protection scope of the embodiments of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the embodiments of the present invention, and all should be covered within the protection scope of the embodiments of the present invention. Therefore, the protection scope of the embodiments of the present invention shall be subject to the protection scope of the claims.

Claims

1. A nitride semiconductor epitaxial substrate, comprising a substrate, characterized in that: The substrate is a single-layer Si substrate or a composite substrate whose surface is a single-crystal silicon material, and also includes a 3C-SiC transition layer on the Si substrate and an aluminum-containing nitride nucleation layer on the 3C-SiC transition layer, wherein the aluminum-containing nitride nucleation layer is prepared by sputtering.

2. A nitride semiconductor epitaxial substrate according to claim 1, characterized in that: The composite substrate with a surface of single crystal silicon material is selected from a SOI substrate, a single-layer Si substrate or a composite substrate, and the single crystal silicon material on the surface is a 111 face or a 100 face.

3. The nitride semiconductor epitaxial substrate according to claim 1, characterized in that: The 3C-SiC transition layer is prepared by chemical vapor deposition or atomic layer deposition process or high temperature carbonization process.

4. The nitride semiconductor epitaxial substrate according to claim 3, characterized in that: When preparing the 3C-SiC transition layer by chemical vapor deposition, one or more C-containing gas sources are reacted with Si-containing gas sources to form the transition layer; It can also be generated by reacting gas sources containing C and Si at high temperature; Alternatively, the surface of the Si substrate is carbonized at high temperature using the C-containing gas source.

5. The nitride semiconductor epitaxial substrate according to claim 3, characterized in that: When the 3C-SiC transition layer is prepared by chemical vapor deposition, the reaction temperature is 700-1400°C.

6. The nitride semiconductor epitaxial substrate according to claim 3, characterized in that: The thickness of the 3C-SiC transition layer is 0.5-2000nm.

7. The nitride semiconductor epitaxial substrate according to claim 3, characterized in that: The 3C-SiC transition layer uses an ultra-thin transition layer with a thickness of 0.5-15nm.

8. The nitride semiconductor epitaxial substrate according to claim 1, characterized in that: The aluminum nitride nucleation layer may be Al x Ga y In (1-x-y) N alloy, wherein 0<x≤1, 0≤y≤1, and the thickness of the aluminum nitride nucleation layer is 10-300nm.

9. The nitride semiconductor epitaxial substrate according to claim 8, characterized in that: The aluminum nitride nucleation layer can be a single layer or a multilayer Al x Ga y In (1-x-y) N alloy, when the aluminum nitride nucleation layer is multi-layer, each layer of Al x Ga y In (1-x-y) N alloys with the same or different compositions, single or multi-layer Al x Ga y In (1-x-y) N alloy with or without B element added.

10. The nitride semiconductor epitaxial substrate according to claim 1, characterized in that: The aluminum nitride nucleation layer is prepared by a sputtering process, and a high temperature annealing process is used after the sputtering process to improve the crystal quality of the nucleation layer.

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