Composite substrate nitride epitaxial wafer and preparation method thereof

Abstract

The invention discloses a nitride epitaxial wafer with a composite substrate. The composite substrate comprises a silicon substrate and a transition layer on the silicon substrate, a silicon dioxide insulating dielectric layer is formed on the side, close to the silicon substrate, of the transition layer through an oxidation process, a nitride layer is formed on the side, away from the silicon substrate, of the transition layer through a nitridation process, and a nitride epitaxial structure grows on the transition layer. Through the nitriding process, at least part of the transition layer which is oxidized in the previous oxidation process and comprises the surface can be converted into a nitride layer, and the crystal quality of a subsequent nitride epitaxial layer is improved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and specifically relates to a composite substrate nitride epitaxial wafer and a preparation method thereof. Background Art

[0002] As a new type of wide-bandgap semiconductor, nitride power devices offer numerous advantages over traditional silicon devices, including a higher breakdown electric field, greater energy efficiency, more stable physical and chemical properties, operating at higher ambient temperatures, and faster switching speeds, which can reduce the size and weight of application systems. These advantages have led to applications in a wide range of fields, including household appliances, electric vehicles, renewable energy sources such as solar and wind power, robotics, intelligent manufacturing, and large-scale data processing centers. However, nitride power devices are currently primarily used in low- and medium-voltage consumer electronics. One reason for this is that nitride epitaxial materials are grown using a heteroepitaxial method, where thin films of nitride semiconductor material are grown on large silicon substrates. Because a conductive channel forms at the interface between the silicon substrate and the nitride epitaxial layer, the device tends to breakdown vertically under high voltages. Consequently, the voltage withstand of gallium nitride power devices is limited by the voltage withstand capability of the epitaxial material in the vertical direction. Increasing the thickness of the epitaxial material can improve the material's pressure resistance accordingly. However, due to the mismatch between the silicon substrate and the nitride epitaxial material in terms of lattice size and thermal expansion coefficient, the thicker the epitaxial layer grown, the greater the stress inside the epitaxial wafer, making it difficult to control the stress and warping of the epitaxial wafer. At the same time, since the warping of the epitaxial wafer also increases accordingly during the thick film growth process, the growth conditions at different locations of the epitaxial wafer will have greater differences, reducing the uniformity of various parameters of the epitaxial wafer. The warping control problem and the uniformity problem of the epitaxial wafer will affect the yield and cost of the final product. In addition, the thicker the epitaxial material grown, the longer the growth time required. Since epitaxial production equipment is very expensive, this will also increase the cost of the product.

[0003] In previous patent documents CN118919398A and CN118919399A, the present inventors disclosed a technical solution using a silicon substrate or a composite substrate with a silicon surface, on which a transition layer is grown. By converting the silicon material at the interface between the transition layer and the substrate into insulating silicon dioxide or silicon nitride, a portion of the thickness of the substrate Si is converted into a high-voltage insulating dielectric layer. This effectively improves the withstand voltage of nitride epitaxy or reduces power loss in RF devices caused by the substrate. However, during the oxidation process, the transition layer is oxidized, which affects the crystal quality during the subsequent nitride epitaxial growth. Summary of the Invention

[0004] In view of the problems in the background technology, the present invention provides a composite substrate nitride epitaxial wafer.

[0005] including a composite substrate and a nitride epitaxial structure grown on the composite substrate;

[0006] The composite substrate comprises: a silicon substrate, a transition layer grown on the silicon substrate, and a silicon dioxide insulating dielectric layer between the silicon substrate and the transition layer, wherein the silicon dioxide insulating dielectric layer is formed by an oxidation process;

[0007] The nitride epitaxial structure is located above the transition layer. A nitride layer is formed on the transition layer away from the silicon dioxide insulating dielectric layer through a nitridation process, and the nitride epitaxial structure continues to grow above the surface of the nitride layer. The nitridation process can convert at least a portion of the transition layer, including the surface, that was oxidized in the previous oxidation process into a nitride layer, thereby improving the crystal quality of the subsequent nitride epitaxial layer.

[0008] As an optional solution of the present invention, the silicon substrate is any one of a single crystal silicon substrate and a substrate with a single crystal silicon material as a surface, such as SOI.

[0009] As an optional solution of the present invention, the transition layer is gallium nitride, aluminum nitride, indium nitride, or their alloy materials or a multilayer stacked structure of the above materials. It can also include alloys formed by the above nitrides and other elements, such as element Sc, and can also include oxygen elements in any proportion to form nitride oxides. This solution does not limit the other elements to be added; it is also possible to first grow a layer of 3C-SiC or SiN material on the surface of the silicon substrate, and then continue to grow the above-mentioned gallium nitride, aluminum nitride, indium nitride, or their alloy materials or a multilayer stacked structure of the above-mentioned materials.

[0010] The present invention provides a method for preparing a composite substrate nitride epitaxial wafer, which is prepared according to the following method:

[0011] providing a silicon substrate;

[0012] growing a transition layer on a silicon substrate;

[0013] The silicon material at the interface between the transition layer and the silicon substrate is oxidized by an oxidation process to form a silicon dioxide insulating dielectric layer;

[0014] converting at least a portion of the transition layer including the surface into a nitride layer through a nitriding process;

[0015] A nitride epitaxial structure is grown over the transition layer.

[0016] An oxidation process oxidizes the silicon material at the interface between the transition layer and the silicon substrate, forming a silicon dioxide insulating dielectric layer. A nitridation process nitrides part or all of the transition layer, including the surface, before growing a nitride epitaxial structure atop the nitrided transition layer. The nitridation process converts at least part of the transition layer, including the surface, that was oxidized during the oxidation process into a nitride layer, improving the crystal quality of the subsequent nitride epitaxial layer.

[0017] As an optional solution of the present invention, the method of growing the transition layer includes: one or more of physical vapor deposition, sputtering, and chemical vapor deposition.

[0018] As an optional solution of the present invention, the oxidation process is one or more of a dry oxidation process, a wet oxidation process, a gas-assisted oxidation process, and a plasma-enhanced oxidation process.

[0019] Furthermore, dry oxidation uses oxygen or other oxygen-containing gases to cause an oxidation reaction between the nitride and the silicon at the interface of the silicon substrate at high temperature to produce SiO2, and the reaction temperature can be 400-1400°C; the wet oxidation process uses water vapor or a gas containing water such as oxygen to cause an oxidation reaction between the nitride and the silicon at the interface of the silicon substrate at high temperature to produce SiO2, and the reaction temperature can be 400-1400°C; the gas-assisted oxidation process uses O3, NO, NO2 and other oxidizing gases to cause an oxidation reaction between the nitride and the silicon at the interface of the silicon substrate at a temperature of 400-1400°C to produce SiO2; the plasma-enhanced oxidation process exposes the substrate to a plasma atmosphere containing the O element to cause an oxidation reaction between the nitride and the silicon at the interface of the silicon substrate to convert into SiO2.

[0020] As an optional solution of the present invention, the nitridation process is one or more of a nitrogen ion implantation process, a thermochemical nitridation process, and a plasma enhanced nitridation process.

[0021] Furthermore, the nitrogen ion implantation process uses nitrogen ions to implant the transition layer;

[0022] Thermochemical nitriding process treats the transition layer with nitrogen-containing gas at a temperature of 400-1400°C to nitride at least a portion of the transition layer including the surface;

[0023] The plasma-enhanced nitridation process exposes the transition layer to a plasma atmosphere containing nitrogen, nitriding at least a portion of the transition layer, including the surface. The nitridation process can also penetrate the entire transition layer and even the silicon dioxide layer generated by the oxidation process.

[0024] As an optional solution of the present invention, the method for growing the nitride epitaxial structure above the transition layer includes but is not limited to: MOCVD, atomic layer deposition (ALD), sputtering, and molecular beam epitaxy (MBE).

[0025] Compared with the prior art, the present invention provides a composite substrate nitride epitaxial wafer, which has the following beneficial effects:

[0026] The present invention oxidizes the silicon material at the interface between the transition layer and the silicon substrate through an oxidation process, forming a silicon dioxide insulating dielectric layer. A nitridation process nitrides part or all of the transition layer, including the surface, before growing a nitride epitaxial structure over the nitrided transition layer. The nitridation process converts at least part of the transition layer, including the surface, that was oxidized during the oxidation process into a nitride layer, thereby improving the crystal quality of the subsequent nitride epitaxial layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the epitaxial wafer structure of Example 1 of the present invention.

[0028] Figures 2a to 2d This is a flow chart for epitaxial wafer production in Example 1.

[0029] Figure 3 This is a schematic diagram of the epitaxial wafer structure of Example 2 of the present invention.

[0030] Figures 4a to 4d This is a flow chart for epitaxial wafer production in Example 2.

[0031] Among them: 10 - substrate; 11 - SiO2 dielectric layer; 12 - transition layer; 13 - buffer layer 13; 14 - channel layer; 15 - barrier layer; 20 - substrate; 21 - SiO2 dielectric layer 21; 22 - transition layer; 23 - buffer layer; 24 - channel layer; 25 - barrier layer 25; 26 - p-type GaN layer 26. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention may be implemented in various forms, and the present invention should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the embodiments of the present invention and various other modifications based on the core technical content of the present invention.

[0033] Example 1

[0034] In the first exemplary embodiment, referring to Figure 1 The structure of the composite substrate nitride semiconductor epitaxial wafer provided in this embodiment includes a substrate 10, and a transition layer 12, a buffer layer 13, a channel layer 14, and a barrier layer 15 sequentially formed on the substrate 10. Between the substrate 10 and the transition layer 12, a silicon material having a certain thickness is converted into a SiO2 dielectric layer 11 through a wet oxidation process.

[0035] The substrate 10 of this embodiment is a silicon material substrate. The transition layer 12 is a 3C-SiC / AlN composite layer with a thickness of 0.1-200nm. The buffer layer 13 may include a structure of AlN, AlGaN, GaN single layer or multilayer stack, AlN / GaN, AlN / AlGaN, AlGaN / GaN superlattice structure, or a combination of the above structures. The thickness of the buffer layer is generally 0.5-7μm. The channel layer 14 is generally a GaN material with a thickness of 20-1000nm. The barrier layer 15 may include an AlGaN layer, an AlN layer, AlInN, AlInGaN, or a multiple superposition of the above material layers. The thickness is 1-30nm. An AlN insertion layer may or may not be included below the barrier layer, with a thickness of 0.1-2nm. The barrier layer may include a GaN cap layer with a thickness of 0.1-10 nm, or an in-situ SiN dielectric layer with a thickness of 0.5-150 nm, or a p-type GaN layer with a thickness of 10-200 nm, or may not include it.

[0036] Reference Figure 2a-2d As shown, this embodiment provides a process flow for preparing the composite substrate nitride epitaxial wafer.

[0037] Step 1, such as Figure 2a As shown, a silicon substrate 10 is provided, on which a transition layer 12 is grown. The growth process is metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), sputtering, or other vapor deposition processes. In this embodiment, the transition layer is formed using MOCVD and includes a 10nm thick 3C-SiC layer and a 30nm thick AlN nucleation layer grown thereon.

[0038] Step 2, such as Figure 2b As shown, the epitaxial wafer with the transition layer 12 grown thereon is subjected to a wet oxidation process commonly used in silicon processing technology. Water vapor is introduced at high temperature to oxidize a silicon material layer of a certain thickness at the interface between the silicon substrate 10 and the transition layer 12, converting it into a SiO2 insulating dielectric layer 11.

[0039] Step 3, such as Figure 2c As shown, the substrate is placed in the MOCVD growth chamber, the substrate temperature is raised to 800°C, H2 is introduced as a carrier gas, and 10SLM NH3 is introduced. The substrate temperature is further raised to 1000°C and maintained for 10 minutes to nitride the transition layer. The chamber pressure is maintained at 266mPa.

[0040] Step 4, such as Figure 2dAs shown, a nitride buffer layer is grown on top of the epitaxial wafer, including a 25nm 800°C low-temperature AlN layer, a 100nm 1080°C high-temperature AlN layer, a 50nm AlGaN layer, and a 3000nm AlN / GaN superlattice structure. A 300nm GaN channel layer, a 1nm AlN insertion layer (not shown in the schematic), and a 25nm AlGaN barrier layer are then grown on top of the buffer layer.

[0041] Example 2

[0042] Reference Figure 3 The structure of the composite substrate nitride semiconductor epitaxial wafer provided in this embodiment includes a substrate 20, and a transition layer 22, a buffer layer 23, a channel layer 24, a barrier layer 25, and a p-type GaN layer 26 sequentially formed on the substrate 20. Between the substrate 20 and the transition layer 22, a silicon material of a certain thickness is converted into a SiO2 dielectric layer 21 through a dry oxidation process.

[0043] The substrate 20 of this embodiment is a 6-inch silicon (111) substrate with a thickness of 1 mm. The transition layer 22 is an AlN layer with a thickness of 0.1-200 nm. The buffer layer 23 may include a structure of AlN, AlGaN, GaN single layer or multilayer stack, AlN / GaN, AlN / AlGaN, AlGaN / GaN superlattice structure, or a combination of the above structures. The thickness of the buffer layer is generally 0.5-7 μm. The channel layer 24 is generally a GaN material with a thickness of 20-1000 nm. The barrier layer 25 may include an AlGaN layer, an AlN layer, AlInN, AlInGaN, or a multiple superposition of the above material layers. The thickness is 1-30 nm. An AlN insertion layer may or may not be included below the barrier layer, with a thickness of 0.1-2 nm. The barrier layer may include a GaN cap layer with a thickness of 0.1-10 nm, or an in-situ SiN dielectric layer with a thickness of 0.5-150 nm, or a p-type GaN layer with a thickness of 10-200 nm, or may not include it.

[0044] Reference Figure 4a-4d As shown, this embodiment provides a process flow for preparing the composite substrate nitride epitaxial wafer.

[0045] Step 1, such as Figure 4a As shown, a silicon substrate 20 is provided, on which a transition layer 22 is grown. The growth process is metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), sputtering, or other vapor deposition processes. In this embodiment, the transition layer includes a 10 nm thick 3C-SiC layer grown using LPCVD, and a 100 nm thick AlN nucleation layer grown using sputtering.

[0046] Step 2, such as Figure 4b As shown, the epitaxial wafer with the transition layer 22 grown thereon is subjected to a dry oxidation process commonly used in silicon processing technology. O2 is introduced at high temperature to oxidize a silicon material layer of a certain thickness at the interface between the silicon substrate 20 and the transition layer 22, and transform it into a SiO2 insulating dielectric layer 21.

[0047] Step 3, such as Figure 4c As shown, a substrate is placed in a sputter chamber, the substrate is heated to 650° C., a mixed gas of nitrogen and argon is introduced to generate N plasma to nitride the substrate, and then a 25 nm AlN layer is sputtered and deposited.

[0048] Step 4, such as Figure 4d As shown, a nitride buffer layer is grown on top of the epitaxial wafer, including a 200nm AlN layer, a 50nm AlGaN layer, and a 3000nm AlN / GaN superlattice structure. A 300nm GaN channel layer, a 1nm AlN insertion layer (not shown in the schematic), a 25nm AlGaN barrier layer, and an 80nm p-type GaN layer are then grown on top of the buffer layer.

[0049] The above description is merely a specific implementation of the embodiments of the present invention, but the scope of protection of the embodiments of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the scope of protection of the embodiments of the present invention. Therefore, the scope of protection of the embodiments of the present invention should be based on the scope of protection of the claims.

Claims

1. A composite substrate nitride epitaxial wafer, characterized in that: including a composite substrate and a nitride epitaxial structure grown on the composite substrate; The composite substrate comprises: a silicon substrate, a transition layer grown on the silicon substrate, and a silicon dioxide insulating dielectric layer between the silicon substrate and the transition layer, wherein the silicon dioxide insulating dielectric layer is formed by an oxidation process; The nitride epitaxial structure is located above the transition layer. The nitride epitaxial structure forms a nitride layer on the transition layer away from the silicon dioxide insulating dielectric layer through a nitridation process, and finally continues to grow the nitride epitaxial structure above the surface of the nitride layer.

2. The composite substrate nitride epitaxial wafer according to claim 1, characterized in that: The silicon substrate is any one of a single crystal silicon substrate and a substrate with a single crystal silicon material as a surface.

3. The composite substrate nitride epitaxial wafer according to claim 2, characterized in that: The transition layer is a metal nitride layer or a metal oxynitride layer; The metal in the metal nitride or metal oxynitride includes at least one or more of gallium, aluminum, and indium; The transition layer is a single layer or a multi-layer stacked structure formed by metal nitrides or metal nitride oxides of different components. 4 . The composite substrate nitride epitaxial wafer according to claim 3 , wherein a layer of 3C-SiC material or a layer of SiN material is grown on the surface of the silicon substrate before depositing the transition layer, or no growth is performed.

5. A method for preparing a composite substrate nitride epitaxial wafer, characterized in that: Prepare as follows: providing a silicon substrate; growing a transition layer on a silicon substrate; The silicon material at the interface between the transition layer and the silicon substrate is oxidized by an oxidation process to form a silicon dioxide insulating dielectric layer; converting at least a portion of the transition layer including the surface into a nitride layer through a nitriding process; A nitride epitaxial structure is grown over the transition layer.

6. The method for preparing a composite substrate nitride epitaxial wafer according to claim 5, characterized in that: Methods for growing the transition layer include: one or more of physical vapor deposition, sputtering, and chemical vapor deposition.

7. The method for preparing a composite substrate nitride epitaxial wafer according to claim 5, characterized in that: The oxidation process is one or more of a dry oxidation process, a wet oxidation process, a gas-assisted oxidation process, and a plasma-enhanced oxidation process.

8. The method for preparing a composite substrate nitride epitaxial wafer according to claim 5, characterized in that: The nitridation process is one or more of a nitrogen ion implantation process, a thermochemical nitridation process, and a plasma enhanced nitridation process.

9. The method for preparing a composite substrate nitride epitaxial wafer according to claim 8, characterized in that: The nitrogen ion implantation process uses nitrogen ions to implant the transition layer; Thermochemical nitriding process treats the transition layer with nitrogen-containing gas at a temperature of 400-1400°C to nitride at least a portion of the transition layer including the surface; The plasma enhanced nitridation process exposes the transition layer to a plasma atmosphere containing N element, so as to nitride at least a portion of the transition layer including the surface.

10. The method for preparing a composite substrate nitride epitaxial wafer according to claim 5, characterized in that: The nitride epitaxial structure growth method above the transition layer is one or more of MOCVD, sputtering, atomic layer deposition, and molecular beam epitaxy.

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