Composite patterned substrate adaptive to high-quality GaN-based epitaxial layer and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductors, and relates to a composite patterned substrate adaptive to a high-quality GaN-based epitaxial layer and a preparation method thereof, and the preparation method comprises the following steps: S1, carrying out the etching of a heterogeneous layer of a conical structure on the substrate through a patterned transfer technology, so as to form a concave-convex microstructure on the side wall of the heterogeneous layer; and S2, depositing a buffer layer on the heterogeneous layer with the concave-convex microstructure on the side wall. A concave-convex microstructure is arranged on the side wall of a heterogeneous layer, and the coverage rate of a buffer layer is regulated and controlled through the concave-convex microstructure and a deposition process, so that the phenomenon of high coverage rate of the top of the buffer layer caused by a graphical conical structure is inhibited, the side wall nucleation rate in subsequent epitaxial GaN nucleation is reduced, GaN crystals are guided to laterally epitaxy, and the GaN quality in epitaxy is improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology and relates to a composite patterned substrate and its preparation method, particularly a composite patterned substrate adapted to high-quality GaN-based epitaxial layers and its preparation method. Background Technology

[0002] With the explosive growth of Mini / Micro LED, high-end displays (VR / automotive screens / ultra-high-definition TVs) account for more than 60%, and high-end display devices place more stringent requirements on the light pattern and axial light intensity of Mini-LEDs.

[0003] Patterned sapphire substrate (PSS) technology alters the light propagation path through its micro / nano structures, reducing the incident angle to below the critical angle and breaking the photon trapping effect. Specifically, the conical / pyramidal patterned structure effectively alters light scattering and extends the optical path, achieving an external quantum efficiency (EQE) of 50-75% for the epitaxial layer. However, the EQE of traditional patterned sapphire substrates (PSS) (50-75%) is insufficient to meet the demands of high-end displays for light patterns and axial light intensity, and it also lacks cost advantages in miniaturization.

[0004] Composite patterned substrates (MMS) introduce low-refractive-index heterolayers (such as SiO2) to improve the critical total internal reflection angle, and the external quantum efficiency of GaN-based epitaxial layers based on this substrate can reach 82–88%. However, as... Figure 1 As shown, since the heterolayer 2 on the substrate 1 has a conical structure, when the buffer layer 5 is deposited on it, the buffer layer 5 will have a high coverage on the top of the heterolayer 2. Moreover, the surface of the buffer layer 5 is relatively smooth, which leads to a high sidewall nucleation rate in the subsequent epitaxial GaN nucleation and reduces the GaN quality in the epitaxy.

[0005] Therefore, in order to overcome the above-mentioned technical defects in the existing technology, there is an urgent need for a new type of composite patterned substrate adapted to high-quality GaN-based epitaxial layers and its preparation method. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a composite patterned substrate adapted for high-quality GaN-based epitaxial layers and its preparation method. This allows the sidewalls of the heterolayer to have concave-convex microstructures, and the coverage of the buffer layer can be controlled by the concave-convex microstructures and deposition process. This suppresses the high coverage phenomenon at the top of the buffer layer caused by the patterned conical structure, thereby reducing the sidewall nucleation rate in subsequent GaN epitaxial nucleation, guiding the GaN crystal to lateral epitaxy, and improving the quality of GaN in epitaxy.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for fabricating a composite patterned substrate adapted to high-quality GaN-based epitaxial layers, characterized by comprising the following steps: S1. The heterostructure of the cone-shaped structure on the substrate is etched by a patterned transfer process to form a concave-convex microstructure on the sidewall of the heterostructure. S2. Deposit a buffer layer on a heterogeneous layer with uneven microstructures on the sidewalls to regulate the coverage of the buffer layer on top of the heterogeneous layer.

[0008] Preferably, step S1 specifically includes: S11. A plasma gas source is formed by the first main etching gas and the auxiliary etching gas to perform the first etching on the heterostructure of the cone structure. During the first etching, the flow rate of the first main etching gas is 60-120 sccm, the flow rate of the auxiliary etching gas is 10-20 sccm, the etching time is 200-300 s, and the lower radio frequency power is 700-900 W. S12. Remove the auxiliary etching gas and perform a second etching on the heterolayer, wherein the etching time for the second etching is 400-600 seconds. S13. Reduce the lower radio frequency power and perform a third etching on the heterolayer. During the third etching, the lower radio frequency power is 350-600W and the etching time is 150-300S. S14. Increase the lower radio frequency power and perform a fourth etching on the heterolayer. During the fourth etching, the lower radio frequency power is 700-900W and the etching time is 10-50S. S15. Introduce a second main etching gas, reduce the flow rate of the first main etching gas and reduce the lower radio frequency power to perform a fifth etching on the heterolayer. During the fifth etching, the flow rate of the second main etching gas is 5-40 sccm, the flow rate of the first main etching gas is reduced by 40%, the lower radio frequency power is 350-600W, and the etching time is 10-50S. S16. Increase the flow rate of the second main etching gas, withdraw the first main etching gas and reduce the lower radio frequency power to perform a sixth etching on the heterolayer. During the sixth etching, the flow rate of the second main etching gas is increased by 200-400%, the lower radio frequency power is 150-300W, and the etching time is 100-250S.

[0009] Preferably, in steps S11-S16, the upper radio frequency power is maintained at 1000-1500W. Preferably, the first primary etching gas is BCl3 or a mixture of Cl2 and BCl3; the secondary etching gas is N2 or O2; and the second primary etching gas is SF6 or CHF3.

[0010] Preferably, in step S2, physical vapor deposition is used when depositing the buffer layer.

[0011] Preferably, during physical vapor deposition, the chamber background pressure is 1×10⁻⁶.-5 ~1×10 -8 Torr, magnetron rotation speed 80-100 r / min, RF power supply 800-1200W, N2 flow rate 150-170 sccm, Ar flow rate 50-100 sccm, carrier plate temperature 400-500℃, target spacing 2.7-3.5 cm, sputtering time 60-85 s.

[0012] Preferably, in step S1, after etching, the etched substrate is acid-washed using a sulfuric acid-hydrogen peroxide solution. During acid washing, the temperature is 100-120°C, the time is 500-650 seconds, and the ratio of sulfuric acid to hydrogen peroxide is 6:1. After acid washing, the substrate is rinsed with water for 400-550 seconds, and then spun dry for 600-720 seconds.

[0013] Preferably, in step S2, before deposition, the substrate surface is cleaned with ionized Ar gas, and when cleaning the substrate surface with ionized Ar gas, 1000-1200W pulsed radio frequency power is used to ionize the Ar gas, and the cleaning time is 10-40S.

[0014] Furthermore, the present invention also provides a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer, characterized in that it is prepared by the method described above for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer.

[0015] Preferably, the sidewalls of the conical heterogeneous layer are formed with concave and convex microstructures to regulate the coverage of the buffer layer on the top of the heterogeneous layer.

[0016] Compared with the prior art, the composite patterned substrate adapted to high-quality GaN-based epitaxial layers and its preparation method of the present invention have one or more of the following beneficial technical effects: 1. The present invention first forms an uneven microstructure on the sidewall of a heterostructure with a conical structure by etching. Then, the coverage of the buffer layer is controlled by adjusting the buffer layer deposition process to suppress the high coverage phenomenon at the top of the buffer layer caused by the patterned conical heterostructure, thereby reducing the sidewall nucleation rate in the subsequent epitaxial GaN nucleation, guiding the GaN crystal to be epitaxial laterally, and improving the quality of GaN in the epitaxy.

[0017] 2. The concave-convex microstructures on the sidewalls of the heterostructure of the conical structure of the present invention form a microscopic shielding layer to hinder the deposition of the buffer layer in the recessed region, thereby achieving partitioned control of the buffer layer. In particular, the buffer layer coverage in the region with high aspect ratio concave-convex microstructures is poor, and the buffer layer is difficult to form a quasi-single crystal, resulting in a low epitaxial nucleation rate of GaN on the sidewalls of the pattern. This is beneficial to the lateral epitaxy of GaN and improves the quality of epitaxial nucleation. At the same time, the concave-convex microstructures on the surface of the heterostructure can further improve the external quantum efficiency of the GaN epitaxial layer. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the existing process of depositing a buffer layer on a heterogeneous layer.

[0019] Figure 2 This is a flowchart of the method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to the present invention.

[0020] Figure 3 This is a schematic diagram of the fabrication process of the composite patterned substrate adapted to high-quality GaN-based epitaxial layers according to the present invention.

[0021] Figure 4 This is a schematic diagram of the present invention after depositing a buffer layer on a heterogeneous layer. Detailed Implementation

[0022] 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. 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.

[0023] Figure 2 A flowchart illustrating the method for fabricating a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to the present invention is shown. Figure 2As shown, the method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to the present invention includes the following steps: S1, heterogeneous layer etching.

[0024] A patterned transfer process is used to etch a heterostructure with a tapered shape on a substrate to form a concave-convex microstructure on the sidewalls of the heterostructure.

[0025] It should be noted that, as Figure 3 As shown, before step S1, similar to existing technologies, a heterogeneous layer 2 needs to be deposited on the substrate 1 using chemical vapor deposition. Then, photoresist 3 is coated onto the heterogeneous layer 2, and photolithography is performed on the heterogeneous layer 2 to form a cone-shaped heterogeneous layer 2. These are all existing technologies, and for simplicity, they will not be described in detail in this invention. Step S1 of this invention involves etching the cone-shaped heterogeneous layer 2.

[0026] In this invention, step S1 specifically includes: S11. A plasma gas source is formed by the first main etching gas and the auxiliary etching gas to perform the first etching on the heterolayer. During the first etching, the flow rate of the first main etching gas is 60-120 sccm, the flow rate of the auxiliary etching gas is 10-20 sccm, the etching time is 200-300 s, the lower RF power is 700-900 W, and the upper RF power is 1000-1500 W.

[0027] In the first etching stage, by introducing the auxiliary etching gas, the ionization of the first main etching gas can be promoted, the longitudinal etching rate can be increased, and the product forms a non-volatile gas. The non-volatile gas forms a deposition layer on the sidewall of the heterostructure 2 of the cone structure, protecting the sidewall of the heterostructure 2 of the cone structure and improving the lateral expansion rate.

[0028] In this invention, the selection of the first primary etching gas and the secondary etching gas is related to the materials of the heterolayer and the substrate. For commonly used materials of the heterolayer and substrate, the secondary etching gas can be N2, O2, etc., and the first primary etching gas can be BCl3 or a mixture of Cl2 and BCl3, etc.

[0029] S12. Withdraw the auxiliary etching gas and perform a second etching on the heterolayer. The etching time for the second etching is 400-600 seconds.

[0030] After the first etching is completed, the auxiliary etching gas is removed, and the heterolayer is etched a second time under the same conditions.

[0031] In the second etching stage, by removing the auxiliary etching gas, the lateral expansion rate of the pattern bottom width can be slowed down, byproducts between heterogeneous layer patterns can be removed, and the secondary masking effect at the bottom of byproducts can be reduced.

[0032] S13. Reduce the lower radio frequency power and perform a third etching on the heterolayer. During the third etching, the lower radio frequency power is 350-600W and the etching time is 150-300S.

[0033] After the second etching is completed, the lower radio frequency power is reduced from 700-900W to 350-600W, while other conditions remain unchanged, and the heterolayer is etched for the third time.

[0034] In the third etching stage, by reducing the lower radio frequency power, the speed of longitudinal mask etching can be slowed down, the selectivity can be improved, and a conical pattern profile can be formed.

[0035] S14. Increase the lower radio frequency power and perform a fourth etching on the heterolayer. During the fourth etching, the lower radio frequency power is 700-900W and the etching time is 10-50S.

[0036] After the third etching is completed, the lower radio frequency power is increased from 350-600W to 700-900W, while other conditions remain unchanged, and the heterolayer is etched for the fourth time.

[0037] In the fourth etching stage, by increasing the lower radio frequency power, the sidewalls of the heterolayer can be modified, the curvature can be reduced, and the substrate step and the total height of the pattern can be controlled.

[0038] S15. Introduce a second main etching gas, reduce the flow rate of the first main etching gas, and reduce the lower radio frequency power to perform a fifth etching on the heterolayer. During the fifth etching, the flow rate of the second main etching gas is 5-40 sccm, the flow rate of the first main etching gas is reduced by 40%, the lower radio frequency power is 350-600W, and the etching time is 10-50 seconds.

[0039] After the fourth etching is completed, a second main etching gas is introduced, the flow rate of the first main etching gas is reduced by 40%, and the lower radio frequency power is reduced from 700-900W to 350-600W. Other conditions remain unchanged, and the heterolayer is then etched for the fifth time.

[0040] In the fifth etching stage, a second main etching gas is introduced. The plasma ionized by the second main etching gas reacts chemically with the heterolayer to form a volatile gas. Furthermore, by reducing the flow rate of the first main etching gas and reducing the lower radio frequency power, physical etching modification can be assisted.

[0041] The choice of the second primary etching gas is also related to the material of the heterolayer; it can be a fluorine-based gas, such as SF6 or CHF3.

[0042] S16. Increase the flow rate of the second main etching gas, withdraw the first main etching gas, and reduce the lower radio frequency power to perform a sixth etching on the heterolayer. During the sixth etching, the flow rate of the second main etching gas is increased by 200-400%, the lower radio frequency power is 150-300W, and the etching time is 100-250S.

[0043] After the fifth etching is completed, the flow rate of the second main etching gas is increased by 200-400%, the first main etching gas is withdrawn, and the lower radio frequency power is reduced from 350-600W to 150-300W. Other conditions remain unchanged, and the heterolayer is then etched for the sixth time.

[0044] In the sixth etching stage, by significantly increasing the amount of the second main etching gas, the chemical reaction during the etching process can be increased, the physical etching modification can be reduced, thereby controlling the concave structure of the heterolayer and delaying the overall decrease in pattern height.

[0045] In this invention, the up-frequency power is maintained at 1000-1500W throughout the entire etching process.

[0046] Thus, through the etching of the first to sixth stages described above, the present invention is able to form a concave-convex microstructure 4 on the sidewall of the heterostructure 2 of the conical structure.

[0047] like Figure 2 As shown, after etching, the etched substrate needs to be acid-washed. In this invention, an SMP (H2SO4:H2O2=6:1) solution is used to clean the surface of the etched substrate, removing impurity particles and byproducts from the etching process. The acid washing temperature is set at 100-120℃, and the time is 500-650 seconds. After acid washing, the substrate is rinsed with water to remove residual acid, and the rinsing time is 400-550 seconds. After rinsing, the substrate is spun dry to remove moisture, and the spun dry time is 600-720 seconds.

[0048] S2, Buffer layer deposition.

[0049] A buffer layer is deposited on a heterogeneous layer with an uneven microstructure on the sidewall.

[0050] In this invention, a buffer layer is deposited on the heterogeneous layer using physical vapor deposition. For example, Figure 2 As shown, before deposition, the substrate surface was cleaned using ionized Ar gas. When cleaning the substrate surface using ionized Ar gas, 1000-1200W pulsed RF power was used to ionize the Ar gas, and the cleaning time was 10-40 seconds.

[0051] Specifically, during physical vapor deposition, the chamber background pressure is 1×10⁻⁶. -5 ~1×10 -8 The parameters are: Torr, magnetron rotation speed 80-100 r / min, RF power supply 800-1200 W, N2 flow rate 150-170 sccm, Ar flow rate 50-100 sccm, carrier substrate temperature 400-500℃, target spacing 2.7-3.5 cm, and sputtering time 60-85 s. These parameters ensure that the sputtered Al and N atoms from the target possess excellent migration capabilities, allowing for uniform and sufficient diffusion on the surface of heterolayer 2, resulting in uniform growth of the three-dimensional islands during the initial growth phase.

[0052] This results in a chamber background pressure of 1×10⁻⁶. -5 ~1×10 -8 Torr and magnetron speed are 80-100 r / min. By controlling the background pressure, impurities can be avoided from affecting the deposition of the deposit layer. By controlling the magnetron speed, the uniformity of the electron confinement track after gas ionization can be ensured.

[0053] refer to Figure 4 ,and Figure 1 Compared with the prior art, the present invention forms an uneven microstructure 4 on the sidewall of the heterostructure 2 of the conical structure, and controls the coverage of the buffer layer 5 by adjusting the buffer layer deposition process, thereby suppressing the high coverage phenomenon of the top of the buffer layer 5 caused by the heterostructure 2 of the patterned conical structure, thereby reducing the sidewall nucleation rate in the subsequent epitaxial GaN nucleation, guiding the GaN crystal to be epitaxial laterally, and improving the quality of GaN in the epitaxy.

[0054] 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 fabricating a composite patterned substrate adapted to high-quality GaN-based epitaxial layers, characterized in that, Includes the following steps: S1. The heterostructure of the cone-shaped structure on the substrate is etched by a patterned transfer process to form a concave-convex microstructure on the sidewall of the heterostructure. S2. Deposit a buffer layer on a heterogeneous layer with uneven microstructures on the sidewalls to regulate the coverage of the buffer layer on top of the heterogeneous layer.

2. The method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to claim 1, characterized in that, Step S1 specifically includes: S11. A plasma gas source is formed by the first main etching gas and the auxiliary etching gas to perform the first etching on the heterostructure of the cone structure. During the first etching, the flow rate of the first main etching gas is 60-120 sccm, the flow rate of the auxiliary etching gas is 10-20 sccm, the etching time is 200-300 s, and the lower radio frequency power is 700-900 W. S12. Remove the auxiliary etching gas and perform a second etching on the heterolayer, wherein the etching time for the second etching is 400-600 seconds. S13. Reduce the lower radio frequency power and perform a third etching on the heterolayer. During the third etching, the lower radio frequency power is 350-600W and the etching time is 150-300S. S14. Increase the lower radio frequency power and perform a fourth etching on the heterolayer. During the fourth etching, the lower radio frequency power is 700-900W and the etching time is 10-50S. S15. Introduce a second main etching gas, reduce the flow rate of the first main etching gas and reduce the lower radio frequency power to perform a fifth etching on the heterolayer. During the fifth etching, the flow rate of the second main etching gas is 5-40 sccm, the flow rate of the first main etching gas is reduced by 40%, the lower radio frequency power is 350-600W, and the etching time is 10-50S. S16. Increase the flow rate of the second main etching gas, withdraw the first main etching gas and reduce the lower radio frequency power to perform a sixth etching on the heterolayer. During the sixth etching, the flow rate of the second main etching gas is increased by 200-400%, the lower radio frequency power is 150-300W, and the etching time is 100-250S.

3. The method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to claim 2, characterized in that, In steps S11-S16, the upper radio frequency power is maintained at 1000-1500W.

4. The method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to claim 3, characterized in that, The first primary etching gas is BCl3 or a mixture of Cl2 and BCl3; the secondary etching gas is N2 or O2; and the second primary etching gas is SF6 or CHF3.

5. The method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to claim 1, characterized in that, In step S2, physical vapor deposition is used when depositing the buffer layer.

6. The method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to claim 5, characterized in that, During physical vapor deposition, the chamber background pressure is 1×10⁻⁶. -5 ~1×10 -8 Torr, magnetron rotation speed 80-100 r / min, RF power supply 800-1200W, N2 flow rate 150-170 sccm, Ar flow rate 50-100 sccm, carrier plate temperature 400-500℃, target spacing 2.7-3.5 cm, sputtering time 60-85 s.

7. The method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to any one of claims 1-6, characterized in that, Step S1: After etching, the etched substrate is acid-washed using a sulfuric acid and hydrogen peroxide solution. During acid washing, the temperature is 100-120℃, the time is 500-650s, and the ratio of sulfuric acid to hydrogen peroxide is 6:

1. After acid washing, the substrate is rinsed with water for 400-550s and then spun dry for 600-720s.

8. The method for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer according to claim 7, characterized in that, In step S2, before deposition, the substrate surface is cleaned with ionized Ar gas. When cleaning the substrate surface with ionized Ar gas, 1000-1200W pulsed radio frequency power is used to ionize the Ar gas, and the cleaning time is 10-40 seconds.

9. A composite patterned substrate adapted to high-quality GaN-based epitaxial layers, characterized in that, It is prepared using the method described in any one of claims 1-8 for preparing a composite patterned substrate adapted to a high-quality GaN-based epitaxial layer.

10. The composite patterned substrate adapted for high-quality GaN-based epitaxial layers according to claim 9, characterized in that, The conical structure of the heterogeneous layer has concave and convex microstructures formed on its sidewalls to regulate the coverage of the buffer layer on the top of the heterogeneous layer.

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