Preparation method of patterned composite substrate for growing gallium nitride single crystal

Abstract

The invention belongs to the technical field of semiconductor growth, and relates to a preparation method of a patterned composite substrate for growing gallium nitride single crystals. The method comprises the following steps: depositing a layer of GaN film on a patterned substrate; performing high-temperature corrosion to form a porous structure; growing a layer of silicon dioxide film; growing a metal layer; performing high-temperature annealing to expose the silicon dioxide layer on the substrate; etching the exposed silicon dioxide by using ICP (Inductively Coupled Plasma) to expose the GaN layer; and carrying out GaN single crystal growth on the processed substrate. The GaN single crystal grows on the substrate prepared through the method, the X-ray diffraction (002) (102) half-peak width can be effectively reduced, the dislocation density of GaN is reduced, and the quality of the GaN single crystal is improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor growth technology and relates to a method for preparing a patterned composite substrate for growing gallium nitride single crystals. Background Technology

[0002] Third-generation semiconductors refer to wide-bandgap semiconductor materials represented by gallium nitride (GaN), silicon carbide (SiC), diamond, and zinc oxide (ZnO). Compared with traditional first- and second-generation semiconductor materials silicon (Si) and gallium arsenide (GaAs), third-generation semiconductor GaN possesses unique properties such as a large bandgap, high breakdown electric field, high thermal conductivity, high electron saturation drift velocity, and low dielectric constant. These properties give it enormous potential in optoelectronic devices, power electronics, radio frequency microwave devices, lasers, and detectors, making it a hot topic in semiconductor research worldwide. Because GaN crystals have a very high melting point (above 2200℃), but its decomposition point is around 900℃, the existence of GaN at its melting point requires extremely high equilibrium nitrogen pressure (above 6 GPa). Therefore, naturally occurring GaN bulk single crystal materials are scarce in nature. Common GaN crystal growth methods include high-pressure nitrogen solution growth, ammonothermal growth, flux growth, and hydride vapor phase epitaxy (HVPE). Due to lattice mismatch and thermal expansion coefficient mismatch in heteroepitaxial growth, high-density dislocations and cracks are typically generated in the epitaxial layer. To reduce defect density and obtain high-quality GaN crystals, two-step growth techniques, buffer layer techniques, substrate surface treatment, flexible substrate techniques, and lateral epitaxial growth have been gradually developed.

[0003] The most significant challenge in GaN crystal growth lies in the lack of suitable seed crystals. Currently, commercially available GaN-based devices primarily utilize sapphire, GaAs, and Si as seed crystals for heteroepitaxial growth. However, these seed crystals exhibit greater lattice and thermal mismatches compared to GaN, resulting in higher stress and dislocation density during GaN single-crystal growth, severely impairing the performance of GaN-based devices. Therefore, selecting seed crystals that effectively reduce stress and dislocation density in epitaxial GaN crystals is crucial for growing high-quality GaN crystals. In existing technologies, such as… Figure 1 As shown, a gallium nitride thin film is typically grown on a sapphire substrate, and then gallium nitride single crystals are grown on the gallium nitride thin film.

[0004] Currently, there are some research reports on the growth of GaN single crystals on porous substrates. For example, Chinese patent document CN101807518A discloses a method for preparing a GaN-based patterned substrate template based on anodic aluminum oxide. The method involves growing a GaN-based template on a substrate; depositing an aluminum layer on the GaN-based template; then laying a microsphere layer on the surface of the aluminum layer; performing metal evaporation on the substrate; removing the monolayer structure of the microsphere layer by ultrasonic vibration to obtain a patterned metal layer; using this metal layer as a mask to etch pits on the surface of the aluminum layer; removing the metal layer to form a porous aluminum oxide layer; using the porous aluminum oxide layer as a mask to transfer the pattern on the aluminum oxide layer to the GaN-based template; and finally removing the porous aluminum oxide layer to obtain the GaN-based material patterned substrate template. This invention is a simple, low-cost method for preparing micron-scale GaN-based patterned substrates with controllable pit size and spacing. However, this process is cumbersome, and the resulting gallium nitride-based patterned substrate is expensive, making it unsuitable for application in gallium nitride single crystal growth.

[0005] Chinese patent document CN103866380A discloses a method for growing GaN single crystals using a patterned annealed porous structure. The method involves preparing a SiO2 patterned mask on a GaN epitaxial wafer; then annealing the GaN epitaxial wafer with the SiO2 patterned mask at high temperature in a vacuum furnace; finally, forming a porous GaN substrate from the annealed GaN epitaxial wafer with the SiO2 patterned mask; and finally, epitaxially growing a GaN single crystal on the porous GaN substrate using HVPE (High-Voltage High-Pressure Polymerization). This method can grow gallium nitride single crystals, but as the crystal thickness increases, the stress increases, increasing the risk of crystal cracking.

[0006] Chinese patent document CN101640169B discloses a method for preparing a nanoscale patterned substrate for nitride epitaxial growth. The method involves depositing a thin aluminum layer on the substrate; etching the surface of the aluminum layer using a femtosecond laser to form periodic shallow pits; anodizing the prepared aluminum layer using an electrochemical method to form a porous mesh alumina layer with nanoscale patterns; removing the blocking layer at the bottom of the pores in the alumina layer and performing appropriate pore enlargement treatment; using the alumina layer as a mask, transferring the nanoscale patterns on the alumina layer to the substrate through etching; removing the alumina layer by etching with an acid or alkaline solution to obtain the substrate with nanoscale patterns; cleaning the substrate with nanoscale patterns, and then performing nitride epitaxial growth and subsequent device fabrication processes. This invention mainly improves the periodicity of the pattern arrangement of porous alumina, thereby increasing the orderliness of the substrate pattern. It is suitable for growing nitride thin films but not suitable for growing nitride single crystals.

[0007] Therefore, there is an urgent need to develop a new patterned substrate to obtain high-quality GaN single crystals. Summary of the Invention

[0008] To address the problems in existing technologies, this invention provides a method for preparing a patterned composite substrate for growing gallium nitride (GaN) single crystals, achieving high-quality GaN single crystal growth. This invention prepares a patterned composite substrate for growing GaN single crystals. After growing a GaN thin film on a sapphire patterned substrate (PSS), a porous structure is then prepared using chemical methods to grow stress-free, self-peeling GaN crystals. This effectively improves the quality of the GaN single crystal, facilitates crystal peeling, and the process is simple, low-cost, and suitable for mass production.

[0009] This invention is achieved through the following technical solution: A method for fabricating a patterned composite substrate for growing gallium nitride single crystals, comprising the following steps: (1) On a patterned substrate (e.g.) Figure 2 a) Deposit a GaN thin film (e.g.) Figure 2 b) (2) The GaN thin film is etched at high temperature into a porous structure (e.g., Figure 2 c) (3) A silicon dioxide thin film is grown on the substrate after the treatment in step (2), and then a metal layer (such as...) is grown. Figure 2 d); (4) The substrate after step (3) is subjected to high-temperature annealing to expose the silicon dioxide layer (e.g., Figure 2 e); (5) Then use ICP to etch away the exposed silicon dioxide to expose the GaN layer (e.g. Figure 2 f); thus obtaining the patterned composite substrate used for growing gallium nitride single crystals.

[0010] Preferably, in step (1), the substrate includes, but is not limited to, at least one of silicon, silicon carbide, sapphire, gallium nitride, aluminum nitride, and gallium oxide.

[0011] Preferably, in step (1), the deposition method includes, but is not limited to, physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), etc.

[0012] Preferably, in step (2), the high-temperature corrosion is carried out by strong acid or strong alkali corrosion solution, or by electrochemical corrosion. Preferably, in step (2), the corrosion temperature is 200-300℃ and the corrosion time is 15-90min.

[0013] Preferably, in step (3), the thickness of the silicon dioxide film is 10-1000 nm; the thickness of the metal layer is 10-1000 nm, and the metal includes, but is not limited to, one of aluminum, nickel, and titanium.

[0014] Preferably, in step (4), the high-temperature annealing temperature is 500-1500℃ and the annealing time is 10-30min.

[0015] The patterned composite substrate prepared by the above method.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a patterned composite substrate for growing gallium nitride (GaN) single crystals to effectively reduce the full width at half maximum (FWHM) of X-ray diffraction (XRD) values ​​(002) and (102), thereby reducing the dislocation density of GaN and improving the quality of GaN single crystals. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of a common substrate; Figure 2 This is the process for preparing patterned composite substrates used to grow gallium nitride single crystals. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0019] Example 1 A method for fabricating a patterned composite substrate for growing gallium nitride single crystals, comprising the following steps: (1) A GaN thin film is MOCVD on a sapphire patterned substrate; (2) The GaN film was etched at a high temperature of 240°C for 30 min using concentrated phosphoric acid (75%) to obtain a porous GaN film; (3) A silicon dioxide film with a thickness of 20 nm is grown on the porous GaN film obtained in step (2) by PECVD, and then a metal aluminum film with a thickness of 50 nm is grown by magnetron sputtering. (4) Anneal the substrate after step (3) at 800°C for 15 min to expose the silicon dioxide layer; (5) The exposed silicon dioxide film is etched away by ICP to expose the gallium nitride layer; thus, the patterned composite substrate for growing gallium nitride single crystal is obtained.

[0020] GaN single crystal growth was performed on the substrate after the treatment in step (5) using the HVPE method.

[0021] Example 2 A method for fabricating a patterned composite substrate for growing gallium nitride single crystals, comprising the following steps: (1) A GaN thin film is MOCVD on a sapphire patterned substrate; (2) The GaN film was etched at a high temperature of 240°C for 50 min using concentrated phosphoric acid (75%) to obtain a porous GaN film; (3) A silicon dioxide film with a thickness of 50 nm is grown on the porous GaN film obtained in step (2) by PECVD, and then a metal nickel film with a thickness of 50 nm is grown by magnetron sputtering. (4) Anneal the substrate after step (3) at 1500℃ for 20 min; (5) The exposed silicon dioxide film is etched away by ICP to expose the gallium nitride layer; thus, the patterned composite substrate for growing gallium nitride single crystal is obtained.

[0022] GaN single crystal growth was performed on the substrate after the treatment in step (5) using the HVPE method.

[0023] Comparative Example 1 A method for preparing a patterned composite substrate for growing gallium nitride single crystals differs from Example 1 in that: in step (1), a sapphire patterned substrate is used, and the processes in steps (2)-(5) are not performed. The XRD test data of the grown single crystal are shown in Table 1.

[0024] Comparative Example 2 A method for fabricating patterned composite substrates for growing gallium nitride single crystals differs from Example 1 in that: Step (1) uses a sapphire patterned substrate, without the processing in steps (3)-(5). The XRD test data of the grown single crystal are shown in Table 1.

[0025] Comparative Example 3 A method for preparing a patterned composite substrate for growing gallium nitride single crystals differs from Example 1 in that: step (1) uses a sapphire patterned substrate; in step (3), only a silicon dioxide layer is grown, without a metal layer; step (4) is not performed; and then step (5) is performed to grow GaN single crystals on the prepared substrate using the HVPE method. The XRD test data of the grown single crystals are shown in Table 1.

[0026] Comparative Example 4 A method for preparing a patterned composite substrate for growing gallium nitride single crystals differs from Example 1 in that: step (1) uses a sapphire patterned substrate; in step (3), no silicon dioxide layer is grown, only a metal Al layer is grown; step (4) is performed; step (5) is not performed; and finally, GaN single crystals are grown using the HVPE method. The XRD test data of the grown single crystals are shown in Table 1.

[0027] Table 1. Technical parameters of GaN single crystals grown on the substrates of the examples and comparative examples.

[0028] As shown in Table 1, the intrinsic full width at half maximum (FWHM) of most semiconductor crystals is around 10 s. Dislocations, point defects, surface mechanical damage, and ion implantation can all destroy the integrity of the crystal. XRD can be used to determine the defect content by measuring the width of the diffraction peaks. The larger the value, the worse the crystal quality.

Claims

1. A method for preparing a patterned composite substrate for growing gallium nitride single crystals, characterized in that, The steps are as follows: (1) Deposit a GaN thin film on the patterned substrate; (2) The GaN thin film is etched into a porous structure at high temperature; (3) A silicon dioxide thin film is grown on the substrate after the treatment in step (2), and then a metal layer is grown; (4) The substrate after step (3) is subjected to high-temperature annealing to expose the silicon dioxide layer. (5) Then use ICP to etch away the exposed silicon dioxide to expose the GaN layer, thus obtaining the patterned composite substrate used to grow gallium nitride single crystals.

2. The preparation method according to claim 1, characterized in that, In step (1), the substrate includes, but is not limited to, at least one of silicon, silicon carbide, sapphire, gallium nitride, aluminum nitride, and gallium oxide.

3. The preparation method according to claim 1, characterized in that, In step (1), the deposition method includes, but is not limited to, physical vapor deposition, chemical vapor deposition, and atomic layer deposition.

4. The preparation method according to claim 1, characterized in that, In step (2), the corrosion temperature is 200-300℃ and the corrosion time is 15-90min.

5. The preparation method according to claim 1, characterized in that, In step (2), the high-temperature corrosion is carried out by strong acid or strong alkali corrosion solution, or by electrochemical corrosion.

6. The preparation method according to claim 1, characterized in that, In step (3), the thickness of the silicon dioxide film is 10-1000 nm; the thickness of the metal layer is 10-1000 nm, and the metal includes, but is not limited to, one of aluminum, nickel, and titanium.

7. The preparation method according to claim 1, characterized in that, In step (4), the high-temperature annealing temperature is 500-1500℃ and the annealing time is 10-30min.

8. The patterned composite substrate prepared by the preparation method according to any one of claims 1-7.

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