Patterned composite substrate, preparation method and epitaxial wafer for ultraviolet LED

Abstract

The present invention discloses a patterned composite substrate, preparation method, and epitaxial wafer for ultraviolet LEDs. The preparation method includes: depositing a silicon dioxide heterogeneous layer and a mask layer on the surface of a sapphire substrate; patterning the mask layer to form a mask pattern; based on the mask pattern, using a dry etching process, simultaneously patterning the silicon dioxide heterogeneous layer and a portion of the sapphire substrate to form a plurality of silicon dioxide heterogeneous raised structures and sapphire recessed structures on the surface of the sapphire substrate; using a wet etching process to modify the silicon dioxide heterogeneous raised structures to form target raised structures, and exposing the sapphire substrate surface between the target raised structures and the adjacent sapphire recessed structures. The above scheme is conducive to improving the growth quality of epitaxial materials; the presence of multiple patterned structures can change the transmission path of light incident on the sapphire substrate, increase light reflection, and improve the light extraction efficiency of the device.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor manufacturing technology, and in particular to a patterned composite substrate for ultraviolet LEDs, a preparation method, and an epitaxial wafer. Background Art

[0002] During the fabrication of UV LED semiconductor devices, if epitaxial material is grown directly on a flat sapphire wafer, lattice and thermal mismatches can lead to numerous dislocations and defects in the epitaxial structure, resulting in poor epitaxial crystal quality and prone to cracking in the film. Dislocations and defects can also extend into the quantum well region of the epitaxial structure, forming non-radiative recombination centers and reducing radiative recombination efficiency. To address these issues, the industry has developed patterned substrates on which epitaxial layers can be grown to improve epitaxial layer growth quality. However, due to total internal reflection of light from the quantum well layer at the interface with air, the refractive index difference between the substrate and epitaxial materials significantly affects light emission. Currently, the commonly used patterned substrates used for UV LED semiconductor epitaxial wafers have a single patterned structure. Growing epitaxial layers on a single patterned sapphire substrate results in suboptimal light extraction efficiency for UV LED epitaxial structures. Furthermore, existing patterned sapphire substrates offer limited improvement in the light extraction efficiency of epitaxial structures. In summary, the epitaxial structure formed based on the existing patterned substrate is difficult to achieve both high crystal quality and high light extraction efficiency, and still needs further optimization. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a patterned composite substrate, a preparation method, and an epitaxial wafer for ultraviolet LEDs to improve the performance of the patterned composite substrate, improve the growth quality of the epitaxial layer, and enhance the light extraction efficiency of the epitaxial structure.

[0004] In a first aspect, an embodiment of the present invention provides a method for preparing a patterned composite substrate for ultraviolet LEDs, comprising:

[0005] Provide sapphire substrates;

[0006] Depositing a silicon dioxide heterogeneous layer and a mask layer on a surface of a sapphire substrate; the surface of the sapphire substrate is a sapphire C-plane;

[0007] performing patterning on the mask layer to form a mask pattern;

[0008] Based on the mask pattern, a dry etching process is used to simultaneously pattern the silicon dioxide heterogeneous layer and a portion of the sapphire substrate to form a plurality of silicon dioxide heterogeneous protrusion structures and sapphire recessed structures on the surface of the sapphire substrate; wherein the bottoms of any adjacent silicon dioxide heterogeneous protrusion structures are connected by the sapphire recessed structures, and the side surfaces of the silicon dioxide heterogeneous protrusion structures are smoothly connected to the side surfaces of the sapphire recessed structures;

[0009] The silicon dioxide heterogeneous protrusion structure is modified by a wet etching process to form a target protrusion structure, and the surface of the sapphire substrate between the target protrusion structure and the adjacent sapphire recessed structure is exposed; wherein the exposed surface of the sapphire substrate has no etching marks.

[0010] In a second aspect, an embodiment of the present invention further provides a patterned composite substrate for ultraviolet LEDs, comprising a sapphire substrate and a plurality of target protruding structures and sapphire recessed structures located on the surface of the sapphire substrate; wherein the target protruding structure and the adjacent sapphire recessed structure are connected through the surface of the sapphire substrate, and there are no etching marks on the surface of the sapphire substrate between the target protruding structure and the adjacent sapphire recessed structure, and the surface of the sapphire substrate is a sapphire C-plane.

[0011] In a third aspect, an embodiment of the present invention further provides an epitaxial wafer, comprising the patterned composite substrate for ultraviolet LEDs as described in the second aspect of the present invention, and an epitaxial layer formed on the patterned composite substrate.

[0012] In the present application, a target protruding structure and a sapphire recessed structure are simultaneously provided on the surface of the sapphire substrate. Compared with a single graphic structure, the combination of the target protruding structure and the sapphire recessed structure can enhance the stress release effect inside the epitaxial structure and improve the growth quality of the epitaxial material. A combination of dry etching and wet etching is adopted so that the target protruding structure and the sapphire recessed structure are connected through a smooth sapphire C-surface, which provides a better opportunity for the growth of the epitaxial material, is beneficial to the nucleation growth of the epitaxial material on the patterned composite substrate, reduces the risk of cracks in the epitaxial film layer, and improves the subsequent LED process yield. In addition, the presence of the target protruding structure and the sapphire recessed structure in the subsequently prepared epitaxial structure can change the transmission path of light incident from the epitaxial quantum well layer to the sapphire substrate, increase light reflection, and further enhance the light extraction efficiency compared with a single substrate material or a single substrate graphic structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A flow chart of a method for preparing a patterned composite substrate provided by an embodiment of the present invention;

[0014] Figure 2 A schematic diagram of a method for preparing a patterned composite substrate provided by an embodiment of the present invention;

[0015] Figure 3 A top view of a patterned composite substrate provided by an embodiment of the present invention;

[0016] Figures 4 to 6 Schematic diagrams of three mask patterns provided by embodiments of the present invention;

[0017] Figure 7 A cross-sectional view of a patterned composite substrate provided by an embodiment of the present invention;

[0018] Figure 8 for Figure 7 Schematic diagram of the enlarged structure at Z;

[0019] Figure 9 for Figure 7 Schematic diagram of the enlarged structure at Y;

[0020] Figure 10 A schematic structural diagram of an epitaxial wafer provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0022] Based on the above-mentioned defects of the prior art, an embodiment of the present invention provides a method for preparing a patterned composite substrate for ultraviolet LEDs, so as to improve the performance of the patterned composite substrate. Figure 1 A flow chart of a method for preparing a patterned composite substrate provided by an embodiment of the present invention is provided. Figure 2 A schematic diagram of a method for preparing a patterned composite substrate provided by an embodiment of the present invention, with reference to Figure 1 and Figure 2 , the preparation method comprises:

[0023] S110. Provide a sapphire substrate.

[0024] Among them, reference Figure 2In Figure (a), the sapphire substrate 1 can be a flat sapphire substrate. The size of the sapphire substrate 1 can be selected as needed and is not limited here. The sapphire substrate 1 can be cleaned before use. Cleaning methods include conventional chemical cleaning and plasma cleaning. Conventional chemical cleaning uses chemical reagents to remove impurities and stains on the sapphire flat substrate. Plasma cleaning utilizes the properties of active components in plasma to treat the sample surface to improve the surface crystalline quality of the sapphire substrate 1.

[0025] S120, depositing a silicon dioxide heterogeneous layer and a mask layer on the surface of the sapphire substrate.

[0026] Further, refer to Figure 2 In Figures (a) and (b), a silicon dioxide heterogeneous layer 3 and a mask layer 4 are sequentially deposited on the surface 2 of the sapphire substrate, and the surface 2 of the sapphire substrate is the sapphire C-plane.

[0027] Optionally, the silicon dioxide heterogeneous layer 3 can be formed by any means in the prior art, such as vacuum evaporation or magnetron sputtering in physical vapor deposition, plasma-enhanced chemical vapor deposition in chemical vapor deposition, etc., which are not limited here. Vacuum evaporation refers to a process method in which a coating material is evaporated and vaporized by a certain heating evaporation method under vacuum conditions, and the particles fly to the surface of the substrate and condense into a film; magnetron sputtering refers to a process in which electrons bombard argon atoms under the action of an electric field, and the argon atoms ionize to produce cations that bombard the target material, causing neutral target atoms or molecules to be deposited on the substrate to form a thin film; chemical vapor deposition uses one or more gaseous compounds or single substances containing thin film elements to chemically react on the surface of the substrate to form a thin film. The thickness of the silicon dioxide heterogeneous layer 3 can be set according to actual needs and is not limited here. In an exemplary embodiment, the thickness of the silicon dioxide heterogeneous layer 3 can be in the range of 0.5 to 5 μm.

[0028] Optionally, the mask layer 4 is a photoresist layer, and the photoresist can be evenly coated on the silicon dioxide heterogeneous layer 3 by uniform coating. The choice of photoresist is not limited, and any one of the existing photoresists can be selected, which can be a positive photoresist or a negative photoresist. The thickness of the mask layer 4 can be set by technical personnel in this field according to actual needs, and there is no limitation here.

[0029] Taking GaN as the epitaxial material as an example, the refractive index of silicon dioxide is 1.45. Compared with the refractive index of sapphire of 1.76, the refractive index difference between silicon dioxide and GaN is greater. The total reflection angle formed at the interface between silicon dioxide and GaN is larger, allowing more light to be reflected, thereby improving light extraction efficiency. In addition, since GaN is not easy to grow on silicon dioxide materials, using silicon dioxide as the substrate material on the side of the pattern can promote the closing of GaN at the top of the pattern and improve the crystal quality of the GaN material.

[0030] S130 , patterning the mask layer to form a mask pattern.

[0031] refer to Figure 2 In the middle (c) figure, the mask layer 4 is patterned to form a mask pattern 5 on the surface of the silicon dioxide heterogeneous layer 3. Optionally, the method for patterning the mask layer 4, i.e., the photoresist layer, is any one of the prior art methods, which is not limited here, and can be, for example, photolithography exposure or nanoimprinting. Photolithography exposure refers to a photolithography technology that transfers the pattern on the mask to the substrate with the help of photoresist under the action of light, and then uses a developer to dissolve the photoresist in the exposed area of ​​the positive photoresist and the non-exposed area of ​​the negative photoresist, thereby forming a three-dimensional mask pattern on the photoresist. Nanoimprinting is a technology that uses photoresist to transfer the micro-nano structure on the template to the material to be processed by applying pressure, thereby forming a three-dimensional mask pattern on the photoresist.

[0032] Optionally, the mask pattern 5 may be arranged in a periodic square lattice arrangement, a periodic hexagonal close-packed arrangement, or the like, without limitation herein. Mask patterns 5 of different arrangements may be formed for reticles of different pattern arrangements. The arrangement period of the mask pattern 5 may be set by those skilled in the art according to actual needs, and is not limited in the present embodiment. For example, the arrangement period may be set to 0.5 to 6 μm, but is not limited thereto.

[0033] Exemplarily, the method for patterning the mask layer 4 using a photolithography exposure process can be briefly described as follows: The mask layer 4 formed in S120 is exposed using a selected mask (not shown). The exposure method can be a step-and-step method, where a single exposure field is sequentially exposed to the mask layer 4. After development, the desired photoresist pillars, i.e., the mask pattern 5, are formed on the silicon dioxide heterogeneous layer 3. It is understood that the parameters such as the size and arrangement of the pattern structure on the final patterned composite substrate are related to the thickness of the mask layer 4 and the arrangement of the mask pattern 4. In actual applications, the thickness of the mask layer 4 and the arrangement of the mask pattern 4 can be adjusted by those skilled in the art according to actual needs. In an exemplary embodiment, the thickness of the mask layer 4 can be 1 to 6 μm, and the height of the mask pattern 5 formed after exposure can also be 1 to 6 μm, but is not limited thereto. It should be noted that the mask pattern 5 described in this application refers to a single photoresist pillar, not an overall pattern composed of all photoresist pillars.

[0034] S140. Based on the mask pattern, a dry etching process is used to simultaneously pattern the silicon dioxide heterogeneous layer and a portion of the sapphire substrate to form a plurality of silicon dioxide heterogeneous protruding structures and sapphire recessed structures on the surface of the sapphire substrate.

[0035] Further, refer to Figure 2In Figure (d), based on the mask pattern 5 obtained in the above steps, the silicon dioxide heterogeneous layer 3 and the partial area of ​​the sapphire substrate 1 are patterned using dry etching technology. The partial area of ​​the sapphire substrate 1 refers to the sapphire substrate surface 2 and the area within a certain thickness range close to the sapphire substrate surface 2. The purpose of dry etching is to form a plurality of silicon dioxide heterogeneous protrusion structures 6 and sapphire recessed structures 7 between adjacent silicon dioxide heterogeneous protrusion structures 6 on the sapphire substrate surface 2. Among them, the bottoms of any adjacent silicon dioxide heterogeneous protrusion structures 6 are connected by the sapphire recessed structure 7, and the side surfaces of the silicon dioxide heterogeneous protrusion structures 6 are smoothly connected to the side surfaces of the sapphire recessed structure 7.

[0036] The dry etching process is to etch the silicon dioxide heterogeneous layer 3 and the sapphire substrate 1 using plasma, for example, an inductively coupled plasma (ICP) dry etching method may be used.

[0037] Specifically, refer to Figure 2 In the middle figure (d), based on the mask pattern 5, a dry etching process such as an ICP dry etching process can be used to simultaneously etch the silicon dioxide heterogeneous layer 3 and a portion of the sapphire substrate 1 to obtain multiple silicon dioxide heterogeneous protruding structures 8 and sapphire recessed structures 7 between any adjacent silicon dioxide heterogeneous protruding structures 8.

[0038] It should be noted that etching the silicon dioxide heterogeneous layer 3 and a portion of the sapphire substrate 1 simultaneously can also be understood as, during the dry etching process, the etching depth reaches the interior of the sapphire substrate 1, that is, in the same area (e.g., within the dotted circle in the figure), using dry etching, the entire thickness of the silicon dioxide heterogeneous layer 3 is etched away, and at the same time, a certain thickness of the sapphire substrate 1 is etched away, leaving a certain thickness of the sapphire substrate 1. Specifically, a raised structure 9 is obtained by dry etching, and the raised structure 9 includes a silicon dioxide heterogeneous layer protrusion 91 and a sapphire protrusion 92, and the side of the silicon dioxide heterogeneous layer protrusion 91 is smoothly connected to the side of the sapphire protrusion 92. The interface between the bottom of the silicon dioxide heterogeneous layer protrusion 91 and the top of the sapphire protrusion 92 is the sapphire substrate surface 2. The silicon dioxide heterogeneous layer protrusion 91 is the silicon dioxide heterogeneous protrusion structure 8 on the sapphire substrate surface 2. In addition, it should be noted that after dry etching, the sapphire substrate surface 2 (i.e., sapphire C-surface) is not exposed, and the bottoms of any two adjacent sapphire protrusions 92 are connected to each other, forming a sapphire recessed structure 7 between the two adjacent sapphire protrusions 92. The side surfaces of the sapphire protrusions 92 are the side surfaces of the sapphire recessed structure 7, and the side surfaces of the sapphire recessed structure 7 are smoothly connected to the side surfaces of the silicon dioxide heterogeneous protrusion structure 8. It should be noted that in order to clearly illustrate the structure of the patterned composite substrate, Figure 2In the middle (d) figure, the sapphire protrusion 92 is represented by a dot-shaped filling pattern. In fact, the sapphire protrusion 92 and the sapphire substrate 1 should be an integral structure. In addition, Figure 2 In the middle figure (d), in order to illustrate the difference between the silicon dioxide heterogeneous protruding structure 8 and the target protruding structure 6, the silicon dioxide heterogeneous protruding structure 8 is filled with a pattern different from the filling pattern of the target protruding structure 6 and the silicon dioxide heterogeneous layer 3. In fact, all three are made of silicon dioxide material.

[0039] The maximum diameter of the bottom pattern of the sapphire protrusion 92 may be 0.5-7 μm, but is not limited thereto.

[0040] S150, modifying the silicon dioxide heterogeneous protruding structure by using a wet etching process to form a target protruding structure, and exposing the sapphire substrate surface between the target protruding structure and the adjacent sapphire recessed structure.

[0041] Further, refer to Figure 2 In Figure (e), the composite substrate obtained in S140 is further processed using a wet etching process to further modify the silicon dioxide heterogeneous protrusion structure 8 into a target protrusion structure 6. The wet etching process is to corrode the composite substrate using a wet etching solution. It can be understood that the size of the target protrusion structure 6 obtained by the wet etching process should be smaller than the silicon dioxide heterogeneous protrusion structure 8, that is, the target protrusion structure 6 is the silicon dioxide heterogeneous protrusion structure 8 with a reduced size; because the silicon dioxide heterogeneous protrusion structure 8 obtained by dry etching is smoothly connected to the side of the sapphire recessed structure 7, in this step, after the wet etching process, the portion of the sapphire substrate surface 2 between the target protrusion structure 6 and the sapphire recessed structure 7 can be exposed, that is, the top surface of the portion of the sapphire protrusion 92 is exposed.

[0042] In addition, it should be noted that in this step, when wet etching is performed, it is necessary to ensure that there are no etching marks on the sapphire substrate surface 2 between the exposed target protruding structure 6 and the sapphire recessed structure 7, that is, the exposed sapphire substrate surface 2 is a smooth surface. Those skilled in the art will understand that the sapphire substrate surface 2 (sapphire C-plane) is the preferred growth surface for epitaxial layer materials (such as GaN), and epitaxial materials are more likely to grow on the sapphire substrate surface 2. In this application, the target protruding structure 6 and the sapphire recessed structure 7 are connected by a smooth sapphire substrate surface 2, which provides better conditions for the growth of epitaxial materials and is conducive to the nucleation and growth of epitaxial materials on the patterned composite substrate.

[0043] In addition, a target protruding structure 6 and a sapphire recessed structure 7 are simultaneously provided on the surface 2 of the sapphire substrate. Compared with a single graphic structure, the combination of the target protruding structure 6 and the sapphire recessed structure 7 can enhance the stress release effect of the internal film layer of the epitaxial structure, improve the quality of epitaxial crystal growth, reduce the risk of cracks in the epitaxial film layer, and enhance the subsequent ultraviolet LED process yield. In addition, in the subsequently prepared epitaxial structure, the presence of the target protruding structure 6 and the sapphire recessed structure 7 can increase light reflection and change the transmission path of light incident from the epitaxial quantum well layer to the sapphire substrate 1, further enhancing the light extraction efficiency of the ultraviolet LED device compared with a single substrate material or a single substrate graphic structure.

[0044] The method for preparing a patterned composite substrate provided by an embodiment of the present invention first provides a sapphire substrate; deposits a silicon dioxide heterogeneous layer and a mask layer on the surface of the sapphire substrate; then patterns the mask layer to form a mask pattern; and then, based on the mask pattern, utilizes a dry etching process to simultaneously pattern the silicon dioxide heterogeneous layer and a portion of the sapphire substrate to form a plurality of silicon dioxide heterogeneous protrusion structures and sapphire recessed structures on the surface of the sapphire substrate; wherein the bottoms of any adjacent silicon dioxide heterogeneous protrusion structures are connected by the sapphire recessed structure, and the side surfaces of the silicon dioxide heterogeneous protrusion structures are smoothly connected to the side surfaces of the sapphire recessed structure; finally, utilizes a wet etching process to modify the silicon dioxide heterogeneous protrusion structure to form a target protrusion structure, and exposes the sapphire substrate surface between the target protrusion structure and the adjacent sapphire recessed structure, wherein the exposed sapphire substrate surface has no etching marks. In the present application, a target protruding structure and a sapphire recessed structure are simultaneously provided on the surface of the sapphire substrate. Compared with a single graphic structure, the combination of the target protruding structure and the sapphire recessed structure can enhance the stress release effect inside the epitaxial structure and improve the growth quality of the epitaxial material. A combination of dry etching and wet etching is adopted so that the target protruding structure and the sapphire recessed structure are connected through a smooth sapphire C-surface, which provides a better opportunity for the growth of the epitaxial material, is beneficial to the nucleation growth of the epitaxial material on the patterned composite substrate, reduces the risk of cracks in the epitaxial film layer, and improves the subsequent ultraviolet LED process yield. In addition, the presence of the target protruding structure and the sapphire recessed structure in the subsequently prepared epitaxial structure can change the transmission path of light incident from the epitaxial quantum well layer to the sapphire substrate, increase light reflection, and further enhance the light extraction efficiency of the device compared with a single substrate material or a single substrate graphic structure.

[0045] Optionally, in a possible embodiment of the present invention, the specific process of the wet etching process can be refined. Exemplarily, the silicon dioxide heterogeneous protruding structure is modified by a wet etching process to form a target protruding structure and expose the sapphire substrate surface between the target protruding structure and the adjacent sapphire recessed structure. Before that, it also includes: preparing a wet etching solution, the wet etching solution chemically reacts with the silicon dioxide material and has no chemical reaction with the sapphire material; modifying the silicon dioxide heterogeneous protruding structure by a wet etching process to form a target protruding structure and expose the sapphire substrate surface between the target protruding structure and the adjacent sapphire recessed structure, including: placing a patterned composite substrate with a silicon dioxide heterogeneous protruding structure and a sapphire recessed structure in a wet etching solution so that the silicon dioxide heterogeneous protruding structure is corroded by the wet etching solution to form a target protruding structure and expose the sapphire substrate surface between the target protruding structure and the adjacent sapphire recessed structure.

[0046] Specifically, in this embodiment, a wet etching solution can be prepared first; then the composite substrate with the silicon dioxide heterogeneous protrusion structure and the sapphire recessed structure obtained after the above S140 is placed in the wet etching solution. Since the wet etching solution only reacts with the silicon dioxide material, during the wet etching process, the wet etching solution reacts with the silicon dioxide heterogeneous protrusion structure 8, causing the size of the silicon dioxide heterogeneous protrusion structure 8 to be reduced; when the size of the silicon dioxide heterogeneous protrusion structure 8 is reduced, a portion of the sapphire substrate surface 2 connecting the silicon dioxide heterogeneous protrusion structure 8 and the sapphire recessed structure 7 adjacent to the silicon dioxide heterogeneous protrusion structure 8 will be exposed (in the dotted box area in the figure). The silicon dioxide heterogeneous protrusion structure 8 with a reduced size after wet etching is the final desired target protrusion structure 6, and the exposed sapphire substrate surface 2 is the preferred growth area for the subsequent epitaxial material.

[0047] The wet etching solution may be a buffered oxide etchant, which is a mixture of hydrofluoric acid (HF) and water and / or ammonium fluoride (NH4F) and water. The buffered oxide etchant only reacts with silicon dioxide and does not react with sapphire.

[0048] The present application does not limit the concentration of the buffered oxide etchant, ie, the mass fraction, and those skilled in the art may set it according to actual needs. In an exemplary embodiment, the mass fraction of the buffered oxide etchant may be 0.5 w% to 10 w%, but is not limited thereto.

[0049] Furthermore, the wet etching time, i.e., the time it takes to etch the composite substrate using the wet etching solution, is not limited in the present embodiment and can be determined by those skilled in the art through multiple experimental tests. For example, when wet etching using the aforementioned buffered oxide etchant, the wet etching time can be controlled within a range of 5 to 200 seconds to ensure that the sapphire substrate surface is exposed without over-etching the silicon dioxide heterogeneous protrusion structure.

[0050] After the first dry etching step, no sapphire substrate surface 2 is exposed. Wet etching is then performed to erode the silicon dioxide heterogeneous raised structures 8, exposing the sapphire substrate surface 2 between the adjacent target raised structures 6 and the sapphire recessed structures 7. Because the wet etching solution does not react with sapphire at all, the exposed sapphire substrate surface 2 is very smooth. This prevents plasma damage to the sapphire substrate surface 2 during the dry etching process alone to form the target raised structures 6 and the sapphire recessed structures 7. This improves the growth quality of epitaxial materials such as GaN on the exposed sapphire substrate surface 2 and reduces the defect density in the epitaxial structure.

[0051] It is understood that when the solution of this embodiment is used, the parameters of the wet etching process (such as the concentration of the wet etching solution and / or the wet etching time, etc.) are related to the size of the target protruding structure 6 and the size of the exposed sapphire substrate surface 2 between the target protruding structure 6 and the sapphire recessed structure 7. The embodiment of the present invention does not limit the specific area of ​​the exposed sapphire substrate surface 2. In actual production, those skilled in the art can adjust the parameters of the wet etching process according to actual needs to adjust the size of the target protruding structure 6 and the area of ​​the exposed sapphire substrate surface 2.

[0052] For example, in one possible embodiment, the width d of the exposed sapphire substrate surface 2 between the target protruding structure 6 and the adjacent sapphire recessed structure 7 is 0.3 to 2 μm. The width d of the exposed sapphire substrate surface 2 refers to the shortest distance between the edge of the target protruding structure 6 connected to the exposed sapphire substrate surface 2 and the edge of the sapphire recessed structure 7 connected to the exposed sapphire substrate surface 2. Experimental optimization has shown that controlling the width of the exposed sapphire substrate surface 2 between adjacent target protruding structures 6 and sapphire recessed structures 7 within this numerical range allows for both high-quality epitaxial material growth and high light extraction efficiency from the epitaxial structure.

[0053] Optional, Figure 3 A top view of a patterned composite substrate provided by an embodiment of the present invention, Figures 4 to 6 Schematic diagram of three mask patterns provided by an embodiment of the present invention, Figures 4 to 6 The top view of the mask pattern 5 is shown. Figures 3 to 6In a possible embodiment, the mask pattern 5 can be any one of an equilateral triangle, a parallelogram and a regular hexagon, and the mask pattern 5 is periodically arranged on the silicon dioxide heterogeneous layer 3; the sapphire recessed structure 7 is distributed in a network pattern on the sapphire substrate surface 2 and defines a plurality of convex structure setting areas A, and the target convex structure 6 is located in the convex structure setting area A.

[0054] Specifically, refer to Figures 3 to 6 , the mask pattern 5 obtained after patterning the mask layer 4 can be any one of an equilateral triangle, a parallelogram and a regular hexagon, and the mask pattern 5 is periodically arranged on the silicon dioxide heterogeneous layer 3. The above-mentioned equilateral triangle, parallelogram and regular hexagon are all graphics that can be closely packed. Close packing means that multiple identical graphics can be laid out without gaps and overlap. When the above-mentioned mask pattern 5 is periodically arranged on the silicon dioxide heterogeneous layer 3, the distance between any adjacent mask patterns 5 is the same. At this time, after dry etching based on the mask pattern 5, the sapphire recessed structures 7 between any adjacent silicon dioxide heterogeneous protrusion structures 8 are interconnected, the sapphire recessed structures 7 are an integrated connected structure, and the sapphire recessed structures 7 are distributed in a mesh on the sapphire substrate surface 2. The meshed sapphire recessed structures 7 divide a plurality of grid openings, which are the protrusion structure setting areas A. The silicon dioxide heterogeneous protrusion structures 8 are formed in the protrusion structure setting area A. After wet etching, the target protrusion structures 6 are also located in the protrusion structure arrangement area A. Simply put, along the plane extending along the sapphire substrate, after dry etching, each silicon dioxide heterogeneous protrusion structure 8 is surrounded by a sapphire recessed structure 7, and the area where the silicon dioxide heterogeneous protrusion structures 8 are located is the protrusion structure arrangement area A. After wet etching, the target protrusion structures 6 are still arranged one-to-one in the protrusion structure arrangement area A, and each target protrusion structure 6 is surrounded by a sapphire recessed structure 7.

[0055] In order to clearly show the relative relationship between the target protruding structure 6 and the sapphire concave structure 7 on the sapphire substrate surface 2, Figure 3 The grid-shaped filled graphics represent the sapphire concave structure 7, and the white filled graphics represent the sapphire substrate surface 2. In fact, the sapphire substrate surface 2 and the sapphire concave structure 7 are made of the same material. Figure 3 Only the target protruding structures 6 and the sapphire recessed structures 7 in a partial area on the sapphire substrate surface 2 are shown. In other areas not shown, the target protruding structures 6 and the sapphire recessed structures 7 are also arranged in the same manner.

[0056] Under this setting, the silicon dioxide protrusion structure and the sapphire recessed structure in the patterned composite substrate can occupy a larger area of ​​the entire sapphire substrate surface, thereby increasing the light reflection path and further improving the light extraction efficiency of the subsequently prepared ultraviolet LED device.

[0057] The specific morphology and size parameters of the target protruding structure 6 and the sapphire recessed structure 7 are not limited in the embodiment of the present invention, and those skilled in the art can set them according to actual needs. Figure 2 The target protrusion structure 6 shown in the figure is a conical protrusion with no curvature on its side. The sapphire concave structure 7 is a V-shaped concave structure with no curvature on its side. The side angle θ1 of the V-shaped concave structure can range from 40° to 80°, but is not limited thereto.

[0058] Alternatively, in a possible embodiment, the distance h1 from the bottom of the sapphire recessed structure 7 to the top of the target protrusive structure 6 may be 0.5 to 5 μm. In other words, the sum of the height of the target protrusive structure 6 and the depth of the sapphire recessed structure 7 is within a range of 0.5 to 5 μm, but is not limited thereto. Furthermore, the ratio between the height of the target protrusive structure 6 and the depth of the sapphire recessed structure 7 may be set within a range of 1:1 to 20:1. According to actual testing, when the height of the target protrusive structure 6 and the depth of the sapphire recessed structure 7 are within this range, the light extraction efficiency of the patterned composite substrate is higher.

[0059] Optionally, in a possible embodiment, the preparation method may further include: adjusting the etching parameters of the dry etching process so that the side of the silicon dioxide heterogeneous protrusion structure 8 and / or the side of the sapphire recessed structure 7 have a curvature; the etching parameters include at least etching time and / or etching gas flow rate.

[0060] Specifically, in this embodiment, the side surfaces of the silicon dioxide heterogeneous protrusion structure 8 and the sapphire recessed structure 7 can be adjusted to a certain curvature by adjusting various etching parameters during the dry etching process. It is understood that the wet etching process has little effect on the shape of the silicon dioxide heterogeneous protrusion structure 8. When the side surfaces of the silicon dioxide heterogeneous protrusion structure 8 have a certain curvature, the side surfaces of the target protrusion structure in the final patterned composite substrate also have a certain curvature. Etching parameters include at least etching time and / or etching gas flow rate, but are not limited thereto. In actual production processes, those skilled in the art can adjust the etching parameters based on actual conditions.

[0061] The side of the target protrusion structure 6 has a certain curvature. The target protrusion structure 6 with a curvature on the side can better utilize the scattering effect to scatter the outgoing light from the active area of ​​the ultraviolet LED device, break the total reflection limitation of the light-emitting interface, improve the effective scattering area of ​​the target protrusion structure 6 for light, and improve the light extraction efficiency of the ultraviolet LED device; similarly, the smooth arc shape of the interior of the sapphire recessed structure 7 is also beneficial to improving the light extraction efficiency of the ultraviolet LED device.

[0062] The range of the side curvature can also be controlled by adjusting various etching parameters during the etching process. For example, when dry etching is used to form the silicon dioxide heterogeneous protrusion structure 8 and the sapphire recessed structure 7, the side morphology can be controlled by changing the flow volume ratio of the mixed gas and the mixed gas flow rate.

[0063] Figure 7 A cross-sectional view of a patterned composite substrate provided by an embodiment of the present invention, referring to Figure 7 As shown in FIG, the target protrusion structure 6 is a conical protrusion, and the side surface of the target protrusion structure 6 has an arc that bulges outward of the target protrusion structure 6; the vertical projection of the side surface of the sapphire concave structure 7 on the plane perpendicular to the sapphire substrate 1 is an arc curve, which can also be understood as the inner wall of the sapphire concave structure 7 is a smooth curve. The plane perpendicular to the sapphire substrate 1 is defined as the first plane. Figure 2 and Figure 7 The cross-sectional view shown in is a cross-sectional view of the patterned composite substrate at the first plane.

[0064] In addition, optionally, the embodiment of the present invention does not limit the range of the side curvature of the target protruding structure 6, and those skilled in the art can set it according to actual application requirements. Figure 8 for Figure 7 Schematic diagram of the enlarged structure at Z, refer to Figure 8 In a possible embodiment, the height h2 of the side curvature protrusion of the target protrusion structure 6 may range from 60 to 180 nm, but is not limited thereto.

[0065] Similarly, the embodiment of the present invention does not limit the range of the arc curve of the inner wall of the sapphire recessed structure 7, and those skilled in the art can set it according to actual application requirements. Figure 9 for Figure 7 Schematic diagram of the enlarged structure at Y, refer to Figure 9 The arc angle θ2 of the arc curve may range from 60° to 120°, but is not limited thereto.

[0066] In one specific embodiment, a method for preparing a patterned composite substrate for ultraviolet LEDs can be described as follows:

[0067] After cleaning a sapphire flat substrate with a thickness of 650 to 660 mm, a 2 μm thick silicon dioxide heterogeneous layer was deposited using a plasma-enhanced chemical vapor deposition process. In the plasma-enhanced chemical vapor deposition process, the RF power on the equipment ranged from 500 to 5000 W, the SiH4 flow rate ranged from 200 to 300 sccm, the N2O flow rate ranged from 5000 to 10000 sccm, the N2 flow rate ranged from 2000 to 5000 sccm, and the chamber temperature ranged from 200 to 350°C.

[0068] On the silicon dioxide heterogeneous layer, hexagonal photoresist columns with a hexagonal periodic arrangement were prepared through the photoresist exposure and development process. The photoresist film thickness was 3μm and the photoresist period was 2.5μm.

[0069] The composite substrate with hexagonal photoresist columns was subjected to ICP dry etching to prepare the desired patterned composite substrate. The patterned composite substrate includes a silicon dioxide heterogeneous raised structure and a sapphire recessed structure. No sapphire flat substrate surface is exposed between the silicon dioxide heterogeneous raised structure and the sapphire recessed structure. The silicon dioxide heterogeneous raised structure and the sapphire recessed structure are arranged alternately on the substrate surface. The side of the silicon dioxide heterogeneous raised structure is curved, and the sapphire recessed structure has a "V"-shaped recessed structure. In the ICP dry etching process, the etching chamber pressure is 3mTorr, the upper RF electrode power range is 1500W, the lower RF electrode power range is 600W, the boron trichloride gas flow rate is 90sccm, the trifluoromethane flow rate is 20sccm, the back helium pressure is 7Torr, and the cooler temperature is 20°C.

[0070] After cleaning, the composite substrate with the silicon dioxide heterogeneous raised structures and sapphire recessed structures was immersed in a dilute buffered oxide etchant for 30 seconds. The silicon dioxide heterogeneous raised structures reacted with the etchant and shrank, forming the target raised structures. This exposed a portion of the sapphire flat substrate surface, which became the sapphire C-plane. The mass fraction of the dilute buffered oxide etchant was 5% by weight.

[0071] In another specific embodiment, a method for preparing a patterned composite substrate for ultraviolet LEDs can be described as follows:

[0072] After cleaning a sapphire flat substrate with a thickness ranging from 800 to 810 mm, a 2.5 μm thick silicon dioxide heterogeneous layer was deposited using a magnetron sputtering process.

[0073] On the silicon dioxide heterogeneous layer, hexagonal photoresist columns with hexagonal periodic arrangement were prepared through uniform coating and nanoimprinting process. The uniform coating film thickness was 1μm, the nanoimprint silicon template pattern height was 2.8μm, and the photoresist period was 3μm.

[0074] The composite substrate with hexagonal photoresist columns is subjected to ICP dry etching to prepare the desired patterned composite substrate. The patterned composite substrate includes a silicon dioxide heterogeneous raised structure and a sapphire recessed structure. No sapphire flat substrate surface is exposed between the silicon dioxide heterogeneous raised structure and the sapphire recessed structure. The silicon dioxide heterogeneous raised structure and the sapphire recessed structure are arranged alternately on the substrate surface. The sides of the silicon dioxide heterogeneous raised structure are curved, and the sides of the sapphire recessed structure are curved. In the ICP dry etching process, the etching chamber pressure is 3mTorr, the upper RF electrode power range is 1500W, the lower RF electrode power range is 700W, the boron trichloride gas flow rate is 100sccm, the trifluoromethane flow rate is 18sccm, the back helium pressure is 6Torr, and the cooler temperature is 30°C.

[0075] After cleaning, the composite substrate with the silicon dioxide heterogeneous protrusions and sapphire recessed structures is immersed in a dilute buffered oxide etchant for 100 seconds. The silicon dioxide heterogeneous protrusions react with the etchant and shrink to form the target protrusions, exposing a portion of the sapphire flat substrate surface, which is the sapphire C-plane. In this embodiment, the mass fraction of the dilute buffered oxide etchant can be 2 w%.

[0076] Based on the same concept, the embodiment of the present invention also provides a patterned composite substrate for ultraviolet LEDs, which can still be referred to Figure 3 and Figure 7 The patterned composite substrate provided by an embodiment of the present invention includes a sapphire substrate 1 and a plurality of target protruding structures 6 and sapphire recessed structures 7 located on a surface 2 of the sapphire substrate; wherein, the target protruding structure 6 is connected to the adjacent sapphire recessed structure 7 through the sapphire substrate surface 2, and there are no etching marks on the sapphire substrate surface 2 between the target protruding structure 6 and the adjacent sapphire recessed structure 7, and the sapphire substrate surface 2 is a sapphire C-plane.

[0077] It should be noted that Figure 3 and Figure 7 The structural dimensions shown are only examples and do not represent actual conditions.

[0078] The patterned composite substrate for ultraviolet LEDs provided by an embodiment of the present invention has a target protruding structure and a sapphire recessed structure simultaneously arranged on the surface of the sapphire substrate. Compared with a single graphic structure, the combination of the target protruding structure and the sapphire recessed structure can enhance the stress release effect inside the epitaxial structure and improve the growth quality of the epitaxial material. The target protruding structure and the sapphire recessed structure are connected by a smooth sapphire C-surface, which provides a better opportunity for the growth of the epitaxial material, is beneficial to the nucleation and growth of the epitaxial material on the patterned composite substrate, reduces the risk of cracks in the epitaxial film layer, and improves the subsequent ultraviolet LED process yield. In addition, the presence of the target protruding structure and the sapphire recessed structure in the subsequently prepared epitaxial structure can change the transmission path of light incident from the epitaxial quantum well layer to the sapphire substrate, increase light reflection, and further improve the light extraction efficiency of the device compared with a single substrate material or a single substrate graphic structure.

[0079] Optional, you can continue to refer to Figure 3 and Figure 7 In a possible embodiment, the sapphire recessed structures 7 are distributed in a network pattern on the sapphire substrate surface 2 and define a plurality of convex structure setting areas A, and the target convex structure 6 is located in the convex structure setting area A.

[0080] Optional, refer to Figure 8 In a possible embodiment, the side surface of the target protruding structure 6 has a curvature that bulges toward the outside of the target protruding structure 6 , and the height h2 of the curvature bulge ranges from 60 to 180 nm.

[0081] Optional, refer to Figure 2 In a possible embodiment, the sapphire recessed structure 7 includes a “V”-shaped recessed structure, and the side angle θ1 of the “V”-shaped recessed structure ranges from 40° to 80°.

[0082] Optional, refer to Figure 9 In a possible embodiment, the vertical projection of the side surface of the sapphire recessed structure 7 on the first plane is an arc curve, and the arc angle θ2 of the arc curve ranges from 60° to 120°; the first plane is perpendicular to the plane where the sapphire substrate 1 is located.

[0083] The patterned composite substrate for ultraviolet LEDs provided in the embodiments of the present invention includes all the technical features and corresponding beneficial effects of the method for preparing the patterned composite substrate for ultraviolet LEDs provided in any embodiment of the present invention, which will not be repeated here.

[0084] Based on the same concept, an embodiment of the present invention further provides an epitaxial wafer, Figure 10This is a schematic structural diagram of an epitaxial wafer provided in an embodiment of the present invention. The epitaxial wafer includes any patterned composite substrate 10 for ultraviolet LEDs provided in an embodiment of the present invention and an epitaxial layer 11 formed on the patterned composite substrate 10.

[0085] Different substrate materials require different UV LED epitaxial wafer growth technologies, chip processing technologies, and device packaging technologies. For the patterned composite substrate provided in the embodiment of the present invention, the epitaxial layer on the corresponding epitaxial wafer can be GaN, AIGaN epitaxial layer, etc.

[0086] The epitaxial wafer provided in the embodiment of the present invention includes all the technical features and corresponding beneficial effects of the patterned composite substrate for ultraviolet LEDs provided in any embodiment of the present invention, which will not be repeated here.

[0087] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will appreciate that the present invention is not limited to the specific embodiments herein, and that various obvious changes, readjustments, combinations, and substitutions are possible for those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the scope of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a patterned composite substrate for ultraviolet LEDs, characterized in that: include: Provide sapphire substrates; depositing a silicon dioxide heterogeneous layer and a mask layer on the surface of a sapphire substrate; The surface of the sapphire substrate is a sapphire C-plane; performing patterning on the mask layer to form a mask pattern; Based on the mask pattern, a dry etching process is used to simultaneously pattern the silicon dioxide heterogeneous layer and a portion of the sapphire substrate to form a plurality of silicon dioxide heterogeneous protrusion structures and sapphire recessed structures on the surface of the sapphire substrate; wherein the bottoms of any adjacent silicon dioxide heterogeneous protrusion structures are connected by the sapphire recessed structures, and the side surfaces of the silicon dioxide heterogeneous protrusion structures are smoothly connected to the side surfaces of the sapphire recessed structures; Modifying the silicon dioxide heterogeneous protrusion structure by a wet etching process to form a target protrusion structure, and exposing the surface of the sapphire substrate between the target protrusion structure and the adjacent sapphire recessed structure; wherein the exposed surface of the sapphire substrate has no etching marks; The mask pattern is any one of an equilateral triangle, a parallelogram and a regular hexagon, and the mask pattern is periodically arranged on the silicon dioxide heterogeneous layer; the sapphire recessed structure is distributed in a reticular manner on the surface of the sapphire substrate and defines a plurality of raised structure setting areas, and the target raised structure is located in the raised structure setting area; the sapphire recessed structure is V-shaped.

2. The preparation method according to claim 1, characterized in that Before modifying the silicon dioxide heterogeneous protruding structure by a wet etching process to form a target protruding structure and exposing the sapphire substrate surface between the target protruding structure and the adjacent sapphire recessed structure, the method further includes: preparing the wet etching solution, wherein the wet etching solution chemically reacts with the silicon dioxide material and does not chemically react with the sapphire material; The method of modifying the silicon dioxide heterogeneous protrusion structure by a wet etching process to form a target protrusion structure and exposing the sapphire substrate surface between the target protrusion structure and the adjacent sapphire recessed structure includes: The patterned composite substrate with the silicon dioxide heterogeneous protruding structure and the sapphire recessed structure is placed in the wet etching solution so that the silicon dioxide heterogeneous protruding structure is corroded by the wet etching solution to form a target protruding structure, and the sapphire substrate surface between the target protruding structure and the adjacent sapphire recessed structure is exposed.

3. The preparation method according to claim 1, characterized in that Also includes: Adjusting etching parameters of the dry etching process so that the side surfaces of the silicon dioxide heterogeneous protrusion structure and / or the side surfaces of the sapphire recessed structure have curvature; The etching parameters at least include etching time and / or etching gas flow rate.

4. A patterned composite substrate for ultraviolet LEDs, obtained by the preparation method according to any one of claims 1 to 3, characterized in that: The invention comprises a sapphire substrate and a plurality of target protruding structures and sapphire recessed structures located on the surface of the sapphire substrate; wherein the target protruding structures are connected to adjacent sapphire recessed structures via the surface of the sapphire substrate, and the surface of the sapphire substrate between the target protruding structures and the adjacent sapphire recessed structures has no etching marks, and the surface of the sapphire substrate is a sapphire C-plane; The sapphire recessed structure is distributed in a network pattern on the surface of the sapphire substrate, and defines a plurality of raised structure setting areas, wherein the target raised structure is located in the raised structure setting area; the raised structure setting area is any one of an equilateral triangle, a parallelogram and a regular hexagon, and is periodically arranged on the sapphire substrate; the sapphire recessed structure is V-shaped.

5. The patterned composite substrate according to claim 4, wherein: The side surface of the target protruding structure has an arc that bulges outward from the target protruding structure, and the height of the arc bulge ranges from 60 to 180 nm.

6. The patterned composite substrate according to claim 4, wherein: The sapphire recessed structure includes a "V"-shaped recessed structure, and the side angle range of the "V"-shaped recessed structure is 40°~80°.

7. The patterned composite substrate according to claim 4, wherein: The vertical projection of the side surface of the sapphire recessed structure on the first plane is an arc curve, and the arc angle range of the arc curve is 60°~120°; the first plane is perpendicular to the plane where the sapphire substrate is located.

8. An epitaxial wafer, characterized in that: It comprises a patterned composite substrate for ultraviolet LEDs as claimed in any one of claims 4 to 7, and an epitaxial layer formed on the patterned composite substrate.

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