Substrate plasma processing method for GaN growth single crystal

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and relates to a substrate plasma processing method for GaN growth of single crystals. The method comprises the following steps: depositing a layer of GaN film on a substrate; performing high-temperature corrosion on the GaN film by using strong phosphoric acid to obtain a GaN surface with a porous structure; sputtering a layer of metal mask on the GaN surface, and then performing high-temperature annealing to obtain a metal mask with a porous structure; plasma treatment is carried out on the porous structure, and then GaN single crystal growth is carried out. According to the method, the plasma is adopted to process the surface of the porous substrate, the surface microstructure of the porous substrate is changed, the quality of subsequently grown GaN single crystals can be effectively improved, and cracks generated in the growth process are reduced. According to the method, a layer of GaN thin film is firstly deposited, then the GaN thin film is processed to grow the GaN single crystal, and the homoepitaxy method is adopted, so that the defects of dislocation, microtubes and the like caused by lattice mismatch of heteroepitaxy can be avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor manufacturing, and relates to a method for substrate plasma treatment for GaN single crystal growth. Background Art

[0002] As a typical representative of the third-generation semiconductor materials, GaN has become an ideal material for fabricating blue-green lasers, radio frequency microwave devices, and power electronic devices due to its excellent properties such as wide bandgap width, high breakdown electric field, and high electron saturation drift velocity. Sapphire has good stability, mature production technology, and low price, and is one of the most widely used substrate materials for heteroepitaxial growth of GaN at present. However, due to the serious lattice constant mismatch and thermal expansion coefficient mismatch between the GaN material and the sapphire substrate, a large number of line dislocation densities (10 9 ~10 11 cm －2 ) are generated inside the epitaxial material, which greatly affects the internal quantum efficiency and light extraction efficiency of GaN-based LED devices.

[0003] To overcome the above problems, researchers have proposed various methods to improve the quality of the GaN epitaxial layer. Among them, plasma treatment technology has attracted much attention due to its simple operation and remarkable effect. Plasma treatment can form a specific microscopic morphology and chemical state on the substrate surface through high-energy particle bombardment and chemical reactions, such as introducing nitrogen vacancies or activating surface atoms, thereby changing the surface energy state distribution, optimizing the nucleation conditions of GaN, promoting two-dimensional growth of the epitaxial layer, and reducing the defect density.

[0004] Currently, there have been some research reports on plasma treatment of substrates for growing GaN single crystals. For example, Chinese Patent Document 202211675344.3 discloses a method for repairing lattice defects on the surface of a wafer epitaxial wafer. The surface of the wafer epitaxial wafer is treated with a plasma of an oxidizing gas such as N2O or O2 to form a uniform oxide layer; then the oxide layer is removed by plasma treatment with a chlorine-based gas; finally, the lattice defects are repaired by plasma treatment with a mixed gas of chlorine and fluorine-based gases; it can improve the uniformity and consistency of the epitaxial wafer, but its process is too complex, and multi-step treatment increases the operation difficulty and cost. Moreover, the synergy of different gas plasma treatments requires high requirements for equipment and process control. If not controlled properly, it may affect the repair effect.

[0005] Chinese Patent (Application No. 202110300393.8) discloses a method for growing gallium nitride on hexagonal boron nitride. After transferring the wrinkled hexagonal boron nitride to other substrates, the wrinkles of the hexagonal boron nitride are treated with oxygen plasma to generate defects and atomic steps in the form of N-O and B-O dangling bonds at the wrinkles, and gallium nitride thin films are grown laterally. Since this method grows gallium nitride on wrinkled boron nitride, only one layer of gallium nitride thin film can be generated, and a thick gallium nitride single crystal cannot be generated. Moreover, there is a lattice mismatch between boron nitride and gallium nitride, and the quality of heteroepitaxially grown gallium nitride is poor.

[0006] Therefore, it is of great significance to develop a substrate surface treatment method with simple process, remarkable effect and applicable to various substrate materials. Summary of the Invention

[0007] The present invention aims to provide a new substrate plasma treatment method for growing single crystal GaN to solve the problems existing in the above-mentioned prior art and achieve high-quality growth of GaN single crystal.

[0008] To achieve the above invention purpose, the present invention provides the following technical solutions: A substrate plasma treatment method for growing single crystal GaN includes the following steps: (1) Depositing a layer of GaN thin film on the substrate; (2) Corroding the GaN thin film with concentrated phosphoric acid at high temperature to obtain a GaN surface with a porous structure; (3) Sputtering a metal mask on the GaN surface, and then performing high-temperature annealing to obtain a metal mask with a porous structure; (4) Performing plasma treatment on the porous structure, and then growing GaN single crystal.

[0009] It is difficult to directly heteroepitaxially grow gallium nitride. The present invention uses inexpensive sapphire as the substrate, and then deposits a layer of GaN thin film for subsequent homoepitaxial growth of GaN single crystal. This method can relieve the stress and defects caused by lattice mismatch and thermal mismatch, and at the same time can significantly reduce the cost and improve the quality of GaN crystals.

[0010] Sputtering the metal mask is to filter out dislocations by using the mask, so that the mask layer blocks the continued extension of penetrating dislocations, and then high-temperature annealing forms a porous structure to facilitate the upward homoepitaxial growth of the underlying GaN thin film, further reducing the dislocation density of GaN single crystal.

[0011] Preferably, in step (1), the substrate includes but is not limited to silicon, silicon carbide, sapphire, gallium nitride, aluminum nitride, and gallium oxide with a size of 2-8 inches.

[0012] 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), and the film thickness is 2 - 10 μm.

[0013] Preferably, in step (2), the temperature of the high-temperature corrosion is 200 - 300 °C, and the corrosion time is 15 - 90 min.

[0014] Preferably, in step (3), the metal mask is Ni, Al, Cr, or Co, and the thickness is 5 - 100 nm.

[0015] Preferably, in step (3), the annealing temperature is 600 - 2000 °C.

[0016] Preferably, in step (4), the plasma is at least one of oxygen, argon, helium, and nitrogen plasmas.

[0017] Preferably, in step (4), the power of the plasma treatment is 1 - 200 W.

[0018] Preferably, in step (4), the plasma treatment time is 1 - 10 min, and the flow rate is 10 - 200 sccm.

[0019] Preferably, in step (4), the GaN single crystal growth method includes but is not limited to hydride vapor phase epitaxy (HVPE), sodium flux method, ammonothermal method, metalorganic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE).

[0020] Compared with the prior art, the present invention has the following beneficial effects: First, the present invention uses plasma to treat the surface of the porous substrate, changing its surface microstructure, which can effectively improve the quality of the subsequently grown GaN single crystal and reduce the cracks generated during the growth process.

[0021] Second, the present invention first deposits a layer of GaN film and then processes it to grow GaN single crystal. The method of homoepitaxy can avoid defects such as dislocations and microtubes caused by lattice mismatch in heteroepitaxy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of the plasma-treated substrate; Figure 2 is a comparison diagram of the growth of gallium nitride single crystal by the methods of Example 1 and Comparative Example 1; Figure 3 is the XRD test result of the growth of gallium nitride single crystal by the methods of Example 1 and Comparative Example 1; Figure 4 is a single crystal diagram grown in Comparative Example 2; Figure 5 Single crystal diagram grown for Comparative Example 3. Specific embodiments

[0023] The present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings of the specification, but not limited thereto. The growth of GaN single crystals in all embodiments and comparative examples of the present invention is the same except for the difference in the substrate, and other growth conditions are the same.

[0024] Example 1 A method for substrate plasma treatment for GaN single crystal growth, comprising the following steps: (1) Deposit a layer of GaN film on a sapphire substrate, and the film thickness is 5 μm; (2) Corrode the GaN film with phosphoric acid at a high temperature of 240 °C for 30 min to obtain a porous GaN surface; (3) Sputter a layer of Ni metal mask on the GaN surface, with a thickness of 10 nm, and then perform high-temperature annealing at 1400 °C to make the metal mask form a porous structure; (4) Perform oxygen plasma treatment on the porous structure of the above metal mask at 100 W for 1 min, with a flow rate of 20 sccm; then perform GaN single crystal growth thereon using the HVPE method.

[0025] Example 2 A method for substrate plasma treatment for GaN single crystal growth, comprising the following steps: (1) Deposit a layer of GaN film on a sapphire substrate, and the film thickness is 5 μm; (2) Corrode the GaN film with phosphoric acid at a high temperature of 220 °C for 50 min to obtain a porous GaN surface; (3) Sputter a layer of Cr metal mask on the GaN surface, with a thickness of 10 nm, and then perform high-temperature annealing at 1800 °C to make the metal mask form a porous structure; (4) Perform nitrogen plasma treatment on the porous structure of the above metal mask at 50 W for 2 min, with a flow rate of 20 sccm; then perform GaN single crystal growth using the same HVPE method as in Example 1.

[0026] Example 3 A method for substrate plasma treatment for GaN single crystal growth, comprising the following steps: (1) Deposit a layer of GaN film on a sapphire substrate, and the film thickness is 8 μm; (2) Corrode the GaN film with phosphoric acid at a high temperature of 240 °C for 30 min to obtain a porous GaN surface; (3) Sputter a Ni metal mask on the GaN surface with a thickness of 20 nm, and then perform high-temperature annealing at 1400 °C to form a porous structure of the metal mask; (4) Perform argon plasma treatment on the porous structure of the above metal mask at 50 W for 2 min, with a flow rate of 50 sccm; then use the HVPE method in Example 1 to grow GaN single crystals.

[0027] Comparative Example 1 A substrate plasma treatment method for growing GaN single crystals includes the following steps: Different from the substrate plasma treatment method for growing GaN single crystals described in Example 1: In step (4), without plasma treatment, directly grow GaN single crystals by the HVPE method. The physical diagrams of the single crystals grown by the two different methods are shown in Figure 2 , (a) is the GaN single crystal diagram grown by the method of Comparative Example 1; (b) is the GaN single crystal diagram grown by the method of Example 1. The XRD test data is shown in Figure 3 , and the full width at half maximum (FWHM) test data is shown in Table 1.

[0028] Table 1. XRD full width at half maximum test data of GaN single crystals obtained in Example 1 and Comparative Example 1

[0029] It can be seen from Table 1 that when growing GaN single crystals under the same conditions, after the treatment of the present invention, the full width at half maximum values of the 002 plane and the 102 plane both become smaller, indicating that the dislocations in the GaN crystal decrease and the crystal quality becomes better. Therefore, the plasma treatment process proposed by the present invention can effectively improve the crystallization quality of GaN crystals.

[0030] Comparative Example 2 A substrate plasma treatment method for growing GaN single crystals includes the following steps: Different from the substrate plasma treatment method for growing GaN single crystals described in Example 1: Do not perform the operation in step (2). The quality of the GaN crystals obtained by this method is slightly worse, but better than that of Comparative Example 1, as shown in Figure 4 .

[0031] Comparative Example 3 A substrate plasma treatment method for growing GaN single crystals includes the following steps: Different from the substrate plasma treatment method for growing GaN single crystals described in Example 1: Do not perform the operation in step (3). The quality of the GaN crystals obtained by this method is poor, but better than that of Comparative Example 1, as shown in Figure 5 .

[0032] The present invention will be further described below in conjunction with specific embodiments. The advantages and features of the present invention will be more clearly reflected in the description. However, the embodiments are only for demonstration and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that without departing from the spirit and scope of the present invention, modifications or substitutions can be made to the details and forms of its technical solutions, and these modifications and substitutions all fall within the protection scope of the present invention.

Claims

1. A substrate plasma processing method for GaN single crystal growth, characterized in that, It includes the following steps: (1) Deposit a layer of GaN thin film on a substrate; (2) Use concentrated phosphoric acid to etch the GaN thin film at high temperature to obtain a GaN surface with a porous structure; (3) Sputter a metal mask on the GaN surface, and then perform high-temperature annealing to obtain a metal mask with a porous structure; (4) Perform plasma treatment on the porous structure, and then grow GaN single crystals.

2. The substrate plasma processing method for GaN single crystal growth according to claim 1, wherein In step (1), the substrate includes but is not limited to silicon, silicon carbide, sapphire, gallium nitride, aluminum nitride, and gallium oxide with a size of 2-8 inches.

3. A substrate plasma processing method for GaN single crystal growth 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, and the thickness of the thin film is 2-10 μm.

4. A substrate plasma processing method for GaN single crystal growth according to claim 1, characterized in that, In step (2), the temperature of the high-temperature etching is 200-300 °C, and the etching time is 15-90 min.

5. A substrate plasma processing method for GaN single crystal growth according to claim 1, characterized in that, In step (3), the metal mask is Ni, Al, Cr, or Co, and the thickness is 5-100 nm.

6. A substrate plasma processing method for GaN single crystal growth according to claim 1, characterized in that, In step (3), the annealing temperature is 600-2000 °C.

7. A substrate plasma processing method for GaN single crystal growth according to claim 1, characterized in that, In step (4), the plasma is at least one of oxygen, argon, helium, and nitrogen plasmas.

8. A substrate plasma processing method for GaN single crystal growth according to claim 1, characterized in that In step (4), the power of the plasma treatment is 1-200 W.

9. A substrate plasma processing method for GaN single crystal growth according to claim 1, characterized in that, In step (4), the time of the plasma treatment is 1-10 min, and the flow rate is 10-200 sccm.

10. A substrate plasma processing method for GaN single crystal growth according to claim 1, characterized in that, In step (4), the methods used for GaN single crystal growth include but are not limited to hydride vapor phase epitaxy, sodium flux method, ammonothermal method, metal organic chemical vapor deposition, and molecular beam epitaxy.

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