A patterned composite substrate, a method for preparing the same and an epitaxial wafer having the same
By depositing an F-doped SiO2 thin film on a sapphire substrate and forming an irregular nanopore structure, combined with dry etching, the problems of complex and costly SiO2-Al2O3 patterned composite substrate preparation process were solved, and the optical performance and light extraction efficiency of GaN-based LEDs were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DONGGUAN ZHONGTU SEMICON TECH CO LTD
- Filing Date
- 2025-09-05
- Publication Date
- 2026-07-21
AI Technical Summary
In the existing technology, the preparation process of SiO2-Al2O3 patterned composite substrates is complex and costly, making it difficult to prepare ultra-high aspect ratio patterns, which limits the crystal quality and light extraction efficiency of GaN-based LEDs.
Plasma-enhanced chemical vapor deposition was used to deposit an F-doped SiO2 thin film on a sapphire substrate. An irregular nanoporous network structure was formed by annealing, and a patterned composite substrate with an ultra-high aspect ratio was prepared by dry etching.
This technology enables the low-cost fabrication of patterned composite substrates with ultra-high aspect ratios, improving the optical performance and light extraction efficiency of GaN-based LEDs, reducing dislocation generation, and enhancing the internal quantum efficiency of epitaxial layers.
Smart Images
Figure CN121099796B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor fabrication technology, and relates to a composite substrate, its fabrication method, and an epitaxial wafer having the same, particularly a patterned composite substrate, its fabrication method, and an epitaxial wafer having the same. Background Technology
[0002] With the escalating energy crisis, low-energy consumption development models are receiving increasing attention. In the lighting field, LEDs, as a new generation of solid-state lighting sources, meet the requirements of energy conservation and emission reduction, but several challenges remain. Firstly, the sapphire substrate used for heteroepitaxial growth and the GaN epitaxial film exhibit significant lattice mismatch and thermal expansion differences, leading to numerous defects in the epitaxial layer, an increase in non-radiative recombination centers, and a decrease in the internal quantum efficiency of the LED. Secondly, the refractive index of the LED chip material is much higher than that of the external air, causing significant total internal reflection of light generated in the active region at the chip-air interface, resulting in a low probability of light passing through the chip surface and reduced light extraction efficiency. To address these challenges, the recently developed patterned sapphire substrate (PSS) technology has shown considerable advantages, but significant technological bottlenecks remain.
[0003] SiO2-Al2O3 patterned composite substrates can improve the crystal quality and light extraction efficiency of GaN-based LED devices. On one hand, in epitaxial growth, to ensure that dislocations in the GaN material grown at the patterned window bend along the sides of the pattern and then converge at the top, the key issue is to minimize the growth of GaN material on the sides of the periodic pattern on the substrate. PSS (Pattern-Side Substrate) makes it difficult to prevent GaN material from growing on the sides of its periodic pattern. However, SiO2-Al2O3 patterned composite substrates have a significant advantage in this regard. Since SiO2 material itself is not suitable for GaN growth, it is easy to prevent GaN material from growing on the sides of the pattern, thus promoting dislocation bending along the sides and convergence at the top, further improving the crystal quality of the GaN material. On the other hand, PSS forms a reflective grating to improve the light extraction efficiency of LED devices. The significant difference in refractive index between GaN and sapphire is an important factor affecting reflection formation. GaN has a refractive index of 2.5, while sapphire has a refractive index of 1.76. This large difference results in a larger total internal reflection angle, thereby improving the light extraction efficiency of the LED. In this respect, the SiO2 material in the SiO2-Al2O3 patterned composite substrate has a greater refractive index difference with GaN, with a refractive index of 1.46. The total internal reflection angle formed with the GaN material is larger, and the resulting reflective grating can reflect more light, thereby further improving the light extraction efficiency.
[0004] However, the traditional process for preparing SiO2-Al2O3 patterned composite substrates is complex. The process for preparing the etching mask involves a photolithography process of spin coating, exposure, and development. This process is costly and the height of the mask pillars is relatively limited, which also limits the final pattern height.
[0005] Therefore, in order to address the shortcomings of the existing technologies, it is necessary to develop a novel patterned composite substrate and its preparation method. Summary of the Invention
[0006] To overcome the shortcomings of existing technologies, this invention proposes a patterned composite substrate, its preparation method, and an epitaxial wafer with the same. The preparation cost is low, and it can produce a mesh-distributed composite substrate with an ultra-high aspect ratio. This can effectively improve the optical performance and light extraction efficiency of GaN-based LEDs, effectively reduce the generation of dislocations, and improve the internal quantum efficiency of the epitaxial layer.
[0007] To achieve the above objectives, the present invention provides the following technical solution:
[0008] A method for preparing a patterned composite substrate, characterized by comprising the following steps:
[0009] S1: A SiO2 thin film doped with F atoms was deposited on the surface of a sapphire substrate using plasma-enhanced chemical vapor deposition;
[0010] S2: The sapphire substrate on which the above-mentioned SiO2 thin film doped with F atoms is deposited is annealed to form a SiO2 thin film with an irregular nanoporous network structure.
[0011] S3: Using the SiO2 thin film with the irregular nanoporous network structure, a patterned composite substrate with holes is prepared by etching.
[0012] Preferably, in step S1, the thickness of the SiO2 film doped with F atoms is 5-10 μm, and during plasma-enhanced chemical vapor deposition, the on-frequency power is 500-5000 W, the SiH4 flow rate is 200-500 sccm, the N2O flow rate is 6000-15000 sccm, the N2 flow rate is 3000-10000 sccm, the C2F6 flow rate is 5000-10000 sccm, the chamber temperature is 100-200℃, and the SiH4:N2O:C2F6 flow rate ratio is controlled at 1:25:20-1:30:25.
[0013] Preferably, in step S2, the annealing process adopts a gradient heating method with a heating rate of 2℃ / min, and after reaching 500-600℃, it is held at that temperature for 30min, and then the temperature is returned to room temperature in a gradient cooling method with a cooling rate of 5℃ / min.
[0014] Preferably, in step S2, the diameter of the nanopores in the SiO2 thin film with the irregular nanopore network structure is 1-500 nm.
[0015] Preferably, in step S3, the depth of the hole is 3-6 μm.
[0016] Preferably, in step S3, a patterned composite substrate with a porous structure is prepared by dry etching.
[0017] Preferably, before step S1, the method further includes:
[0018] S0: Clean the sapphire substrate.
[0019] Preferably, S0 specifically involves cleaning the sapphire substrate with acetone, isopropanol, and deionized water for 5 minutes with each solution.
[0020] Furthermore, the present invention also provides a patterned composite substrate, characterized in that it is prepared by the preparation method described above.
[0021] Finally, the present invention also provides an epitaxial wafer, characterized in that it has a patterned composite substrate as described above and a gallium nitride epitaxial structure is grown on the patterned composite substrate.
[0022] Compared with the prior art, the patterned composite substrate and its preparation method of the present invention, and the epitaxial wafer having the same, have one or more of the following beneficial technical effects:
[0023] 1. The process of this invention is less expensive than that of traditional SiO2-Al2O3 patterned composite substrates, and can produce ultra-high aspect ratio mesh-distributed composite substrates.
[0024] 2. In this invention, the SiO2 composite structure and ultra-high aspect ratio pattern can effectively improve the optical performance and light extraction efficiency of GaN-based LEDs.
[0025] 3. In this invention, the mesh-like partitioning of GaN epitaxial layers can effectively reduce the generation of dislocations and improve the internal quantum efficiency of the epitaxial layer. Attached Figure Description
[0026] Figure 1 This is a flowchart of the method for preparing the patterned composite substrate of the present invention.
[0027] Figure 2 This is a schematic diagram of the patterned composite substrate prepared according to the present invention. Detailed Implementation
[0028] Before detailing any embodiment of the invention, it should be understood that the invention, in its application, is not limited to the details of the construction and arrangement of the components set forth in the following description or illustrated in the following figures. The invention can have other embodiments and can be practiced or carried out in various ways. Furthermore, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered limiting. The use of “comprising” or “having” and variations thereof is intended to cover the items set forth below and their equivalents, as well as any additional items. Unless otherwise specified or limited, the terms “installation,” “connection,” “support,” and “linkage,” and variations thereof are used broadly and cover both direct and indirect installation, connection, support, and linking. Moreover, “connection” and “linkage” are not limited to physical or mechanical connections or links.
[0029] Furthermore, firstly, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention. Secondly, the term "a" should be understood as "at least one" or "one or more," that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple. The term "a" should not be construed as a limitation on the quantity.
[0030] Existing methods for fabricating patterned composite substrates involve a photolithography process of spin coating, exposure, and development to prepare the etching mask. This process is costly and limits the height of the photoresist pillars in the prepared mask, thus restricting the final pattern height. Therefore, this invention provides a novel method for fabricating patterned composite substrates that is cost-effective and can produce ultra-high aspect ratio mesh-distributed composite substrates. This method can effectively improve the optical performance and light extraction efficiency of GaN-based LEDs, effectively reduce dislocation generation, and improve the internal quantum efficiency of the epitaxial layer.
[0031] Figure 1 A flowchart illustrating the method for fabricating the patterned composite substrate of the present invention is shown. For example... Figure 1 As shown, the method for preparing the patterned composite substrate of the present invention includes the following steps:
[0032] S0: Cleaning.
[0033] In this invention, the sapphire substrate can first be cleaned.
[0034] Preferably, during cleaning, the sapphire substrate can be cleaned using acetone, isopropanol, and deionized water, with each solution cleaning for 5 minutes.
[0035] The cleaning process removes impurities from the sapphire substrate, which facilitates the subsequent deposition of SiO2 thin films.
[0036] S1: Thin film deposition.
[0037] In this invention, a SiO2 thin film doped with F atoms is deposited on the surface of a sapphire substrate using plasma-enhanced chemical vapor deposition (PECVD).
[0038] Specifically, the thickness of the deposited F-doped SiO2 film is 5-10 μm. During plasma-enhanced chemical vapor deposition, the on-frequency power is 500-5000 W, the SiH4 flow rate is 200-500 sccm, the N2O flow rate is 6000-15000 sccm, the N2 flow rate is 3000-10000 sccm, the C2F6 flow rate is 5000-10000 sccm, the chamber temperature is 100-200 °C, and the SiH4:N2O:C2F6 flow rate ratio is controlled at 1:25:20-1:30:25. Therefore, the F-doping ratio in the deposited F-doped SiO2 film can be controlled at 15-30%.
[0039] S2: Annealing process.
[0040] After the thin film deposition, the sapphire substrate on which the SiO2 thin film doped with F atoms was deposited was annealed to form a SiO2 thin film with an irregular nanoporous network structure.
[0041] Specifically, during the annealing process, a gradient heating method is used, with a heating rate of 2℃ / min. After reaching 500-600℃, the temperature is held for 30 minutes, and then the temperature is gradually reduced back to room temperature at a cooling rate of 5℃ / min.
[0042] Because the chemical bonds between Si and O atoms in the F-doped SiO2 film are not stable, the high temperature conditions during annealing cause partial decomposition and partial retention of the SiO2 film. Thus, through the aforementioned annealing process, the decomposed portion of the F-doped SiO2 film forms a network structure with irregular nanopores. The diameter of these irregular nanopores is 1-500 nm.
[0043] S3: Etching.
[0044] After forming a SiO2 thin film with an irregular nanoporous network structure, the irregular nanopores can be etched using existing dry etching methods to prepare materials such as... Figure 2The patterned composite substrate with holes is shown.
[0045] In this invention, the depth of the hole is 3-6 μm.
[0046] Therefore, compared with the traditional photolithography process of spin coating, exposure, and development, this invention does not require coating and etching, resulting in lower fabrication costs. Furthermore, the fabricated holes have greater depths, leading to a higher final pattern height.
[0047] After the patterned composite substrate is prepared, GaN LED epitaxial structures can be grown on the patterned composite substrate using metal-organic chemical vapor deposition (MOCVD) to form an epitaxial wafer.
[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention based on the concept of the present invention, without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for preparing a patterned composite substrate, characterized in that, Includes the following steps: S1: A SiO2 thin film doped with F atoms is deposited on the surface of a sapphire substrate using plasma-enhanced chemical vapor deposition; wherein the thickness of the SiO2 thin film doped with F atoms is 5-10 μm, and during plasma-enhanced chemical vapor deposition, the on-frequency power is 500-5000 W, the SiH4 flow rate is 200-500 sccm, the N2O flow rate is 6000-15000 sccm, the N2 flow rate is 3000-10000 sccm, the C2F6 flow rate is 5000-10000 sccm, the chamber temperature is 100-200℃, and the flow ratio of SiH4:N2O:C2F6 is controlled at 1:25:20-1:30:25; S2: The sapphire substrate with the above-mentioned SiO2 thin film doped with F atoms is annealed to form a SiO2 thin film with an irregular nanoporous network structure. The annealing process adopts a gradient heating method with a heating rate of 2℃ / min, and after reaching 500-600℃, it is held for 30min, and then the temperature is reduced back to room temperature with a gradient cooling method at a cooling rate of 5℃ / min. S3: Using the SiO2 thin film with the irregular nanoporous network structure, a patterned composite substrate with holes is prepared by etching.
2. The method for preparing a patterned composite substrate according to claim 1, characterized in that, In step S2, the diameter of the nanopores in the SiO2 thin film with the irregular nanopore network structure is 1-500 nm.
3. The method for preparing a patterned composite substrate according to claim 2, characterized in that, In step S3, the depth of the hole is 3-6 μm.
4. The method for preparing a patterned composite substrate according to claim 3, characterized in that, In step S3, a patterned composite substrate with a porous structure is prepared by dry etching.
5. The method for preparing a patterned composite substrate according to any one of claims 1-4, characterized in that, Before step S1, the following is also included: S0: Clean the sapphire substrate.
6. The method for preparing a patterned composite substrate according to claim 5, characterized in that, Specifically, S0 involves cleaning the sapphire substrate with acetone, isopropanol, and deionized water for 5 minutes with each solution.
7. A patterned composite substrate, characterized in that, It is prepared by any one of the preparation methods according to claims 1-6.
8. An epitaxial wafer, characterized in that, It has the patterned composite substrate as described in claim 7, and a gallium nitride epitaxial structure is grown on the patterned composite substrate.