A preparation method of a self-grown micro / nano GaN column array structure and a micro / nano GaN column array structure

Abstract

This invention proposes a method for fabricating a self-grown micro / nano GaN pillar array structure and the micro / nano GaN pillar array structure itself, comprising, from bottom to top, a substrate, an AlN film, and a monolayer PS (polystyrene) colloidal sphere array structure; and from left to right, a SiNx layer, a cavity array structure, and a self-grown micro / nano GaN pillar array structure thereon. This invention employs a process combining self-assembly technology and MOCVD (metal-organic chemical vapor deposition) technology to fabricate ordered micro / nano GaN pillar array structures with adjustable geometric dimensions. The structures fabricated according to this invention have advantages over structures fabricated by existing technologies such as nanoimprinting, photolithography, and electron beam lithography, including lower dislocation density, higher light extraction efficiency, and higher internal quantum efficiency. Furthermore, this invention offers low fabrication costs and flexible process timing, thus showing broad application prospects in fields such as Micro-LED displays, solid-state lighting, photodetectors, and bioimaging.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic materials and device manufacturing technology, specifically a method for preparing a self-grown micro / nano GaN pillar array structure and the micro / nano GaN pillar array structure. Background Technology

[0002] The growth of micro / nano GaN pillar arrays is a rapidly expanding field of semiconductor material and device growth technology, primarily due to the unique functionality and high crystallinity of micro / nano pillars. Typically, a large lattice and thermal mismatch exists between GaN and the substrate, causing relaxation of the lattice's lateral strain, which leads to an increase in surface dislocation density. Dislocations, acting as non-radiative recombination centers or leakage current channels, severely impact device performance. Employing micro / nano GaN pillar arrays can significantly reduce dislocation density because dislocations generated at the nanopillar-substrate interface can bend towards the sidewalls of the micro / nano GaN pillar array. This is particularly effective when the nanopillars have a high aspect ratio, effectively reducing the dislocation density at the top of the micro / nano GaN pillar array. Furthermore, the geometry of micro / nano GaN pillars offers a large surface area to volume ratio, facilitating charge transfer at the interface. In addition, the non-planar absorber geometry of the micro / nano GaN pillar array improves light extraction and absorption efficiency, significantly enhancing the optoelectronic performance of the device.

[0003] Common methods for fabricating micro / nano GaN pillar array structures include photolithography, nanoimprint lithography, and electron beam lithography, such as... Figure 1 As shown. However, photolithography etching can typically only produce micrometer-sized GaN pillar structures, not nanometer-sized GaN pillar array structures. While nanoimprint lithography for fabricating micro / nano GaN pillar array structures has lower fabrication costs, continuous imprinting contaminates the wafer surface, causing the pattern to gradually become blurred, leading to a decrease in product yield. Electron beam lithography for fabricating micro / nano GaN pillar array structures offers high precision, but its time-consuming and costly process makes it unsuitable for mass production. Furthermore, although light-emitting devices with micro / nano GaN pillar structures have been fabricated using traditional self-assembly techniques, the pillar structures are mostly randomly distributed and lack periodicity during the fabrication process. To better control the distribution of micro / nano GaN pillar array structures, growing GaN micro / nano pillars on micro / nano patterned substrates can be used, but these substrates are not only expensive but also have fixed pattern sizes. Summary of the Invention

[0004] Purpose of the invention: To address the shortcomings of traditional fabrication techniques for micro / nano GaN pillar array structures, this invention proposes a method for fabricating self-grown micro / nano GaN pillar array structures and the resulting micro / nano GaN pillar array structure. By combining self-assembly technology with MOCVD processes, ordered micro / nano GaN pillar array structures can be fabricated rapidly and at low cost. Furthermore, by employing a SiNx cavity array structure, not only can structural damage that may be caused by traditional etching techniques be avoided, but the geometric dimensions of the micro / nano GaN pillar array structure can also be arbitrarily adjustable, with the smallest size reaching the tens of nanometers level.

[0005] Technical solution: In a first aspect, this invention proposes a method for fabricating a self-grown micro / nano GaN pillar array structure, comprising:

[0006] An AlN film was physically vapor-deposited on a substrate, and the surface was bombarded with a plasma cleaner to obtain a hydrophilic composite substrate.

[0007] After the polystyrene colloidal sphere solution is mixed evenly with ethanol, the mixture is dropped onto a silicon wafer to cover it. The silicon wafer is then immersed in a glass container filled with ultrapure water. The polystyrene colloidal sphere mixture diffuses on the surface of the ultrapure water and forms a continuous monolayer array of polystyrene colloidal spheres.

[0008] By using the aforementioned hydrophilic composite substrate to retrieve a single-layer polystyrene colloidal sphere array from the surface of ultrapure water, and then etching the single-layer polystyrene colloidal sphere array, a single-layer polystyrene colloidal sphere array structure is formed on the hydrophilic composite substrate.

[0009] A SiNx layer is deposited on a surface hydrophilic composite substrate on which the monolayer polystyrene colloidal sphere array structure is formed;

[0010] Adhesive tape is applied to the surface of a hydrophilic composite substrate on which a SiNx layer has been deposited, and the tape is in contact with the upper surface of a monolayer polystyrene colloidal sphere array structure. The monolayer polystyrene colloidal sphere array structure is removed by peeling off the tape to form a cavity array structure.

[0011] GaN nucleation and growth were first performed on a hydrophilic composite substrate with a cavity array structure on its surface, followed by 2D growth. Micro / nano GaN pillar array structures were obtained by longitudinal growth in the cavity array structure region.

[0012] Furthermore, the substrate is any one of sapphire, silicon carbide, silicon, gallium nitride, or aluminum nitride with any crystal orientation.

[0013] Furthermore, the geometric dimensions and spacing of the polystyrene spheres in the monolayer polystyrene colloidal sphere array are obtained by changing the etching conditions.

[0014] Furthermore, the growth thickness of the SiNx layer is smaller than the radius of the etched polystyrene colloidal sphere.

[0015] Secondly, this invention proposes a self-grown micro / nano GaN pillar array structure, which is prepared using the above-disclosed method for preparing a self-grown micro / nano GaN pillar array structure.

[0016] Furthermore, it includes a surface hydrophilic composite substrate, and a SiNx layer and a self-grown micro / nano GaN pillar array structure on the surface hydrophilic composite substrate, which are arranged from left to right.

[0017] Beneficial Effects: This invention uses a monolayer PS micro / nanosphere array structure, formed by the self-assembly of PS colloidal spheres on substrates such as sapphire, as a mask. The size and spacing of the PS colloidal spheres are precisely controlled by reactive ion etching (RIE). Then, a micro / nano-scale cavity array is formed by depositing a SiNx layer using ICP-CVD technology and removing the PS colloidal sphere array as a mask. Finally, MOCVD technology is used to realize the self-grown micro / nano GaN pillar array structure. Compared with existing technologies, the self-grown micro / nano GaN pillar array structure and its fabrication method provided by this invention have significant advantages such as simple fabrication process, adjustable structural geometry, and low dislocation density. Therefore, it has broad application prospects in fields such as Micro-LED displays, solid-state lighting, photodetectors, and bioimaging. Attached Figure Description

[0018] Figure 1 A schematic diagram of the process flow for fabricating micro / nano GaN pillar array structures using existing technologies such as photolithography, micro / nano imprinting, and electron beam lithography.

[0019] Figure 2 A schematic diagram of a self-grown micro / nano GaN pillar array structure and its preparation method provided by the present invention;

[0020] Figure 3 This is a detailed process flow diagram illustrating the self-growth of micro / nano GaN pillar array structures on substrates such as sapphire and its fabrication method; wherein: Figure 3 (A) in the diagram shows any planar substrate; Figure 3 (B) shows an AlN film deposited on the substrate using a PVD method; Figure 3 (C) in the figure shows a monolayer PS colloidal sphere array structure that is self-assembled on an AlN film; Figure 3 (D) shows the monolayer PS colloidal sphere array structure after RIE etching; Figure 3 (E) in the image shows a SiNx layer grown on a monolayer PS colloidal sphere array using ICP-VD; Figure 3 (F) shows the cavity array structure formed after removing the PS colloidal ball array with tape; Figure 3 (G) in the figure shows a self-grown micro / nano GaN pillar array structure prepared by MOCVD technology. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the following description, in conjunction with the accompanying drawings and embodiments, will further illustrate a self-growing micro / nano GaN pillar array structure and its preparation method.

[0022] Example 1:

[0023] This invention proposes a method for fabricating a self-grown micro / nano GaN pillar array structure, which mainly includes the following steps:

[0024] The substrate is placed in a plasma cleaner, and Ar gas is introduced to bombard the substrate surface, making the substrate surface hydrophilic. For example... Figure 3 As shown in (A), the substrate is any one of the following substrate materials with any crystal orientation: sapphire, silicon carbide, silicon, gallium nitride, aluminum nitride, etc.

[0025] AlN films are deposited on substrates using PVD (physical vapor deposition) methods, such as... Figure 3 As shown in (A), its thickness is 10~100 nm. The physical vapor deposition growth conditions are: operating power of 10~100 W, Ar gas flow rate of 25~100 sccm, and operating pressure of 0.6~3 Pa. A hydrophilic composite substrate is formed by the AlN film and the substrate.

[0026] After thoroughly mixing the PS colloidal sphere solution with ethanol, use a pipette to drop the mixture onto a silicon wafer with a diameter of 2-6 inches. Once the mixture has dispersed, slowly immerse the silicon wafer covered with the PS colloidal sphere mixture into a glass container filled with ultrapure water at a specific angle. The PS colloidal sphere mixture diffuses on the water surface, forming a continuous monolayer array of PS colloidal spheres. Figure 3 As shown in (B), a single-layer PS colloidal sphere array is retrieved from the water surface using a hydrophilic composite substrate composed of an AlN film and a substrate. Excess water is then absorbed from the edges using absorbent paper, forming a single-layer ordered PS colloidal sphere array on the hydrophilic composite substrate. Finally, the PS colloidal sphere array is etched using a reactive ion etching (RIE) system, as shown in [image B]. Figure 3As shown in (C) above. The RIE etching conditions are: operating power of 50~100 W, O2 gas flow rate of 50~200 sccm, and operating pressure of 20~100 Pa. The geometry and spacing of the PS colloidal spheres can be flexibly adjusted by changing the etching conditions as needed. For example, the diameter of the PS colloidal spheres in a single-layer PS colloidal sphere array structure can be 50~2000 nm.

[0027] SiNx layers were deposited on a PS colloidal sphere array using the ICP-CVD (Inductively Coupled Plasma Chemical Vapor Deposition) method, such as... Figure 3 As shown in (D) in the figure. The deposition conditions for the SiNx layer are: substrate temperature 250~300 ℃, ICP source power 700~1000 W, bias RF 100~300 W, cavity pressure 0.3~0.6 Torr, and deposition rate of 5~10 nm / min. The core raw materials are silane (SiH4) and ammonia (NH3), with N2 / Ar as dilution carrier gas. The SiH4:NH3 flow ratio is 1:3~1:5, the SiH4 flow rate is 30~50 sccm, and the NH3 flow rate is 120~200 sccm to achieve the required SiNx film density, optical properties, and stress state. The growth thickness of the SiNx layer should be controlled to be smaller than the radius of the etched PS colloidal spheres.

[0028] Adhesive tape is used to adhere to the substrate surface on which the SiNx layer has been deposited on the PS colloidal sphere array. Since the contact surfaces with the tape are all on the upper surface of the PS colloidal sphere array, the PS colloidal sphere array can be removed by peeling off the tape, forming a cavity array structure. Figure 3 As shown in (E), the size (period) of the cavity array structure is 20~2000 nm, which can be controlled by changing the etching conditions of the PS colloidal sphere array.

[0029] A substrate with a cavity array structure on its surface was heated at a high temperature of 1000–1080 °C in an H2 atmosphere and purged with H2 for at least 1–5 min to remove impurities from the substrate surface. Then, the substrate was nitrided at 950–980 °C with a mixture of H2 and NH3 for 30–300 s, using an NH3 flow rate of 1000–5000 sccm. Next, the temperature was lowered to approximately 500–560 °C, and GaN nucleation growth was performed at an NH3 / TMGa molar ratio (V / III ratio) of approximately 500–5000 and a working pressure of approximately 550–750 mbar (low temperature, high pressure). Finally, the temperature was raised to 1020–1100 °C for annealing for approximately 2–10 min. Finally, 2D growth was carried out under conditions of lowering the temperature to 1000~1080 ℃, setting the NH3 / TMGa flow ratio (V / III ratio) to 500~1000, and the working pressure to 50~200 mbar (high temperature, low pressure). This employs a two-step MOCVD growth method—nucleation followed by 2D self-growth—to obtain micro / nano GaN pillar array structures. Figure 3 As shown in (F), the diameter of the self-grown micro / nano GaN array structure in this embodiment of the invention is basically corresponding to the size of the cavity array structure, but the height is arbitrarily adjustable.

[0030] like Figure 2 As shown, the self-grown micro / nano GaN pillar array structure prepared according to the above preparation method includes, from bottom to top, a substrate 101, an AlN film 102, and a monolayer PS (polystyrene) colloidal sphere array structure 103; on the monolayer PS (polystyrene) colloidal sphere array structure 103, from left to right, a SiNx layer 104, a cavity array structure 105, and a self-grown micro / nano GaN pillar array structure 106 on the SiNx layer 104 and the cavity array structure 105.

[0031] This invention employs a process combining self-assembly and MOCVD (metal-organic chemical vapor deposition) techniques to fabricate ordered, geometrically tunable micro / nano GaN pillar array structures. Compared to structures prepared using existing techniques such as nanoimprinting, photolithography, and electron beam lithography, the structures prepared according to this invention exhibit advantages such as low dislocation density, high light extraction efficiency, and high internal quantum efficiency. Furthermore, this invention offers low fabrication costs and flexible process timing, thus demonstrating broad application prospects in fields such as Micro-LED displays, solid-state lighting, photodetectors, and bioimaging.

[0032] Example 2:

[0033] Based on Example 1, this invention proposes a method for fabricating a self-grown micro / nano GaN pillar array structure, comprising the following steps:

[0034] The sapphire substrate 101 is placed in a plasma cleaner, and Ar gas is introduced to bombard the surface of the substrate, making the surface of the sapphire substrate 101 hydrophilic.

[0035] Next, an AlN thin film 102 was deposited on the sapphire substrate 101 using physical vapor deposition (PVD). The specific deposition conditions were: operating power of 10 W, Ar gas flow rate of 50 sccm, operating pressure of 0.6 Pa, and AlN film thickness controlled at 20 nm.

[0036] A self-assembled PS sphere array structure 103 is formed on an AlN thin film 102. The specific process steps are as follows: A PS colloidal sphere solution is mixed uniformly with ethanol, and the mixture is then pipetted onto a 2-inch diameter silicon wafer. After the mixture spreads, the silicon wafer covered with the PS colloidal sphere mixture is slowly immersed at an angle of approximately 20° into a glass container filled with ultrapure water. The PS colloidal sphere mixture diffuses on the water surface and forms a continuous monolayer film. The monolayer PS colloidal sphere array film is then retrieved from the water surface using a hydrophilic substrate composed of the AlN film 102 and a sapphire substrate 101. Excess water is absorbed from the edges using absorbent paper, forming a monolayer ordered PS colloidal sphere array 103 on the composite substrate. Finally, the PS colloidal sphere array 103 is etched using a reactive ion etching (RIE) system. Figure 3 As shown in (C) in the figure. The RIE etching conditions are: operating power of 50 W, O2 gas flow rate of 50 sccm, and operating pressure of 20 Pa. Under these conditions, the etching rate of PS colloidal spheres is approximately 1 nm / s. The geometry and spacing of the PS colloidal spheres can be flexibly adjusted by changing the etching conditions as needed.

[0037] SiNx layer 104 was deposited on PS colloidal sphere array 103 using the ICP-VD method, as follows: Figure 3 As shown in (D) in the figure. The deposition conditions for SiNx layer 104 are as follows: N2 / Ar as dilution carrier gas, SiH4:NH3 flow rate ratio of 1:4, SiH4 flow rate of 40 sccm, and NH3 flow rate of 160 sccm to achieve the required SiNx film thickness. The growth thickness of SiNx layer 104 is controlled to be smaller than the radius of the etched PS colloidal spheres, as shown in (D). Figure 3 As shown in (D), the purpose is to prevent GaN pillars from nucleating on the SiNx layer.

[0038] A polyimide adhesive tape is used to bond the PS colloidal sphere array 103. The adhesive properties of the tape are then used to remove the PS colloidal sphere array 103, forming a cavity array structure 105. Figure 3As shown in (E) in the diagram. During the bonding process using non-residue adhesive tape, it is crucial to ensure that no air bubbles are generated. Since the SiNx layer thickness is less than the radius of the PS colloidal spheres, the contact surface of the tape bonding is the upper surface of the PS colloidal sphere array, and the SiNx layer 104 deposited in the gaps between the PS colloidal spheres remains unaffected. Therefore, the PS colloidal sphere array 103 can be removed by peeling off the tape, leaving an AlN film on the surface of the cavity region 105, with an array structure of SiNx layers between the cavities.

[0039] The prepared sapphire substrate 101 with cavity array structure 105 was placed in the MOCVD reaction chamber to grow the GaN micro / nanopillar array structure 106. Figure 3 As shown in (F) in the diagram. First, the sapphire substrate 101 was heated to 1080 °C in an H2 atmosphere and purged with H2 for 1 min to remove impurities from the substrate surface. Then, the temperature was lowered to 980 °C, and a mixture of H2 and NH3 was introduced to nitrid the substrate for 1 min, with an NH3 flow rate of 1600 sccm. The temperature was further lowered to 550 °C, and GaN nucleation growth was performed at an NH3 / TMGa molar ratio (V / III ratio) of 3000 and an operating pressure of 650 mbar for 70 s. Then, the temperature was increased to 1070 °C for annealing for 7 min. Afterward, the temperature was lowered to 1050 °C, and 2D growth was performed at an NH3 / TMGa flow rate ratio (V / III ratio) of 1000 and an operating pressure of 200 mbar. Since GaN can only nucleate and grow longitudinally in the cavity region (AlN film), and cannot nucleate in the SiNx layer between cavities, GaN will not grow in this region, thus a self-grown micro / nano GaN pillar array structure is finally obtained.

Claims

1. A method for fabricating a self-grown micro / nano GaN pillar array structure, characterized in that: include: An AlN film was physically vapor-deposited on a substrate, and the surface was bombarded with a plasma cleaner to obtain a hydrophilic composite substrate. After the polystyrene colloidal sphere solution is mixed evenly with ethanol, the mixture is dropped onto a silicon wafer to cover it. The silicon wafer is then immersed in a glass container filled with ultrapure water. The polystyrene colloidal sphere mixture diffuses on the surface of the ultrapure water and forms a continuous monolayer array of polystyrene colloidal spheres. By using the aforementioned hydrophilic composite substrate to retrieve a single-layer polystyrene colloidal sphere array from the surface of ultrapure water, and then etching the single-layer polystyrene colloidal sphere array as needed, a single-layer polystyrene colloidal sphere array structure with a certain spacing is formed on the hydrophilic composite substrate. A SiNx layer is deposited on a surface hydrophilic composite substrate on which the monolayer polystyrene colloidal sphere array structure is formed; Adhesive tape is applied to the surface of a hydrophilic composite substrate on which a SiNx layer has been deposited, and the tape is in contact with the upper surface of a monolayer polystyrene colloidal sphere array structure. The monolayer polystyrene colloidal sphere array structure is removed by peeling off the tape to form a cavity array structure. GaN nucleation and growth were first performed on a hydrophilic composite substrate with a cavity array structure on its surface, followed by 2D growth. Micro / nano GaN pillar array structures were obtained by longitudinal growth in the cavity array structure region.

2. The method for fabricating a self-grown micro / nano GaN pillar array structure according to claim 1, characterized in that: The substrate is any one of sapphire, silicon carbide, silicon, gallium nitride, or aluminum nitride that is flat and has any crystal orientation.

3. The method for fabricating a self-grown micro / nano GaN pillar array structure according to claim 1, characterized in that: An AlN film of a certain thickness is deposited on a substrate using physical vapor deposition (PVD), and then the surface is bombarded with a plasma cleaner to make the surface hydrophilic.

4. The method for fabricating a self-grown micro / nano GaN pillar array structure according to claim 1, characterized in that: The geometric dimensions and spacing of the polystyrene spheres in the monolayer polystyrene colloidal sphere array are controlled by changing the etching conditions.

5. The method for fabricating a self-grown micro / nano GaN pillar array structure according to claim 1, characterized in that: The growth thickness of the SiNx layer is smaller than the radius of the etched polystyrene colloidal sphere.

6. A self-grown micro / nano GaN pillar array structure, characterized in that: The micro / nano GaN pillar array structure was prepared using the method described in any one of claims 1 to 4.

7. The self-grown micro / nano GaN pillar array structure according to claim 5, characterized in that: It includes a surface hydrophilic composite substrate, and a SiNx layer and a self-grown micro / nano GaN pillar array structure on the surface hydrophilic composite substrate, which are arranged from left to right.

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