A patterned composite substrate, preparation method and LED epitaxial wafer

Abstract

The embodiment of the present invention discloses a patterned composite substrate, a preparation method and an LED epitaxial wafer. The patterned composite substrate comprises: a patterned substrate; a patterned epitaxial buffer layer, the patterned epitaxial buffer layer covers the patterned substrate, a plurality of first microstructures are formed on the side of the patterned epitaxial buffer layer away from the patterned substrate, the first microstructure comprises a first heterogeneous material structure, and the first heterogeneous material structure is at least located on the top of the first microstructure. The embodiment of the present invention solves the problem that when a patterned sapphire substrate grows a gallium nitride epitaxial layer, there is still lattice mismatch, low external quantum efficiency and low luminous brightness, and achieves the effect of enhancing light extraction efficiency and improving epitaxial growth quality, which helps to improve the external quantum efficiency of LEDs.

Description

Technical Field

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

[0002] As market application demands continue to increase and develop in a diversified manner, the performance of GaN-based LED products also needs to further improve the photoelectric conversion efficiency to meet the needs. Figure 1 is a schematic diagram of the structure of a patterned sapphire substrate in the prior art, such as Figure 1 As shown, the patterned sapphire substrate includes a sapphire substrate 1 and a second microstructure 2 formed on the sapphire substrate 1. The current patterned sapphire substrate can alleviate the stress during the epitaxial growth of GaN to a certain extent, reduce the dislocation density, and improve the external quantum efficiency. At the same time, it can also appropriately increase the light extraction efficiency of the LED device through the pattern array, effectively improving the light extraction rate. Therefore, the patterned sapphire substrate has successfully replaced the sapphire flat substrate as the GaN epitaxial growth substrate.

[0003] However, with the widespread use of LEDs, the performance requirements for LED products are getting higher and higher, especially in special high-tech fields, which require LED products with smaller area and higher brightness. However, the pattern array provided by the current patterned sapphire substrate has limited ability to relieve the stress of epitaxial layer growth, and the patterned sapphire substrate and gallium nitride still have large lattice adaptation problems, which limits the further improvement of LED external quantum efficiency; at the same time, the pattern array is also limited in improving the light extraction efficiency, and the light extraction efficiency needs to be further improved. Summary of the invention

[0004] The present invention provides a patterned composite substrate, a preparation method and an LED epitaxial wafer to solve the problems of large lattice adaptation, low external quantum efficiency and low luminous brightness between a patterned sapphire substrate and gallium nitride.

[0005] In a first aspect, an embodiment of the present invention provides a patterned composite substrate, the patterned composite substrate comprising:

[0006] Graphic substrate;

[0007] A patterned epitaxial buffer layer, wherein the patterned epitaxial buffer layer covers the patterned substrate, and a plurality of first microstructures are formed on a side of the patterned epitaxial buffer layer away from the patterned substrate, wherein the first microstructure includes a first heterogeneous material structure, and the first heterogeneous material structure is at least located on the top of the first microstructure.

[0008] Optionally, the first microstructure further includes an epitaxial material structure located at the bottom.

[0009] Optionally, a direction from the patterned substrate toward the patterned epitaxial buffer layer is taken as a first direction;

[0010] The length ratio of the epitaxial material to the first microstructure in the first direction is R, wherein 0%<R≤95%.

[0011] Optionally, a plurality of second microstructures and / or a plurality of pits are formed on the surface of the patterned substrate, and the patterned epitaxial buffer layer covers the second microstructures and / or the pits.

[0012] Optionally, the second microstructure includes a second heterogeneous material structure, and the second heterogeneous material structure is at least located on the top of the second microstructure.

[0013] Optionally, the shapes of the first microstructure and the second microstructure are at least one of a truncated cone, a cone, a pyramid, a prism and a spherical cap.

[0014] Optionally, the plurality of second microstructures and the plurality of first microstructures are arranged in an array;

[0015] The arrangement period of the second microstructure is in the range of 100 nm-10 μm, and the arrangement period of the first microstructure is in the range of 100 nm-10 μm.

[0016] Optionally, the bottom diameter of the second microstructure is in the range of 500nm-20μm; the height of the second microstructure is in the range of 10nm-10μm;

[0017] The bottom diameter of the first microstructure is in the range of 500 nm-20 μm; the height of the first microstructure is in the range of 10 nm-10 μm.

[0018] Optionally, the first heterogeneous material structure is a silicon dioxide structure, a titanium dioxide structure or a zinc oxide structure; the patterned epitaxial buffer layer is a patterned gallium nitride layer; and the patterned substrate is a sapphire patterned substrate.

[0019] In a second aspect, an embodiment of the present invention further provides an LED epitaxial wafer, comprising the patterned composite substrate as described in the first aspect above, and also comprising an epitaxial layer located on the patterned composite substrate;

[0020] The patterned composite substrate includes a patterned epitaxial buffer layer, and the epitaxial layer is made of the same material as the patterned epitaxial buffer layer.

[0021] In a third aspect, an embodiment of the present invention further provides a method for preparing a patterned composite substrate, the method for preparing a patterned composite substrate comprising:

[0022] Providing a flat substrate;

[0023] patterning the flat substrate to form a patterned substrate;

[0024] forming an epitaxial buffer layer on the surface of the patterned substrate, wherein the epitaxial buffer layer covers the patterned substrate;

[0025] The epitaxial buffer layer is patterned to form a patterned epitaxial buffer layer; wherein the patterned epitaxial buffer layer covers the patterned substrate, and a plurality of first microstructures are formed on the side of the patterned epitaxial buffer layer away from the patterned substrate, wherein the first microstructure includes a first heterogeneous material structure, and the first heterogeneous material structure is at least located on the top of the first microstructure.

[0026] Optionally, patterning the flat substrate to form a patterned substrate comprises:

[0027] forming a first photoresist layer on the flat substrate;

[0028] Exposing and developing the first photoresist layer with a first preset pattern mask to form a first photoresist mask;

[0029] Etching the flat substrate with the first photoresist mask to form the plurality of second microstructures and / or a plurality of pits;

[0030] The first photoresist mask is removed to form the patterned substrate.

[0031] Optionally, before patterning the flat substrate to form a patterned substrate, the method further comprises:

[0032] forming a heterogeneous material layer on the surface of the flat substrate;

[0033] Patterning the flat substrate to form a patterned substrate comprises:

[0034] forming a first photoresist layer on the heterogeneous material layer;

[0035] Exposing and developing the first photoresist layer with a first preset pattern mask to form a first photoresist mask;

[0036] Etching the heterogeneous material layer and the flat substrate with the first photoresist mask to form the plurality of second microstructures and / or a plurality of pits;

[0037] The first photoresist mask is removed to form the patterned substrate.

[0038] Optionally, forming an epitaxial buffer layer on the surface of the patterned substrate comprises:

[0039] forming an epitaxial material layer on the surface of the patterned substrate, wherein the epitaxial material layer covers the second microstructure;

[0040] A heterogeneous material layer is formed on a surface of the epitaxial material layer that is away from the patterned substrate.

[0041] Optionally, patterning the epitaxial buffer layer to form a patterned epitaxial buffer layer includes:

[0042] forming a second photoresist layer on a surface of the heterogeneous material layer facing away from the epitaxial material layer;

[0043] exposing and developing the second photoresist layer with a second preset pattern mask to form a second photoresist mask;

[0044] Etching the heterogeneous material layer with the second photoresist mask to form the plurality of first microstructures; wherein the first microstructure includes a first heterogeneous material structure, and the first heterogeneous material structure is at least located on the top of the first microstructure;

[0045] The second photoresist mask is removed to form the patterned epitaxial buffer layer.

[0046] Optionally, etching the heterogeneous material layer with the second photoresist mask to form the plurality of first microstructures comprises:

[0047] The heterogeneous material layer is over-etched with the second photoresist mask to form the plurality of first microstructures; wherein the first microstructures include a first heterogeneous material structure located at the top and an epitaxial material structure located at the bottom.

[0048] Optionally, a direction from the patterned substrate toward the patterned epitaxial buffer layer is taken as a first direction, and a length ratio of the epitaxial material to the first microstructure in the first direction is R, wherein 0%<R≤95%.

[0049] A patterned composite substrate, a preparation method and an LED epitaxial wafer provided by an embodiment of the present invention are provided. A patterned epitaxial buffer layer is provided on a patterned substrate, a first microstructure is formed in the patterned epitaxial buffer layer, and a first heterogeneous material structure is formed at least at the top of the first microstructure. On the one hand, the growth process of the epitaxial layer material on the patterned epitaxial buffer layer is homogeneous growth, so as to avoid lattice defects of the epitaxial material and improve the growth quality of the epitaxial material on the C-plane between the first microstructures. On the other hand, since there is a refractive index difference between the patterned epitaxial buffer layer and the patterned substrate, and the first microstructure is provided on the patterned epitaxial buffer layer, the probability of full emission of light at the exit interface can be reduced, which helps to improve the extraction efficiency of LED light and improve the external quantum efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1Schematic diagram of the structure of a patterned sapphire substrate in the prior art.

[0051] Figure 2 A schematic structural diagram of a patterned composite substrate provided in an embodiment of the present invention.

[0052] Figure 3 A schematic structural diagram of another patterned composite substrate provided in an embodiment of the present invention.

[0053] Figure 4 This is a local electron microscope image of a patterned composite substrate provided by an embodiment of the present invention.

[0054] Figure 5 A schematic structural diagram of an LED epitaxial wafer provided in an embodiment of the present invention.

[0055] Figure 6 A schematic flow chart of a method for preparing a patterned composite substrate provided in an embodiment of the present invention.

[0056] Figure 7 A structural flow chart of a method for preparing a patterned composite substrate provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0058] Figure 2 A schematic diagram of the structure of a patterned composite substrate provided by an embodiment of the present invention is shown in FIG. Figure 2 As shown, a patterned composite substrate includes: a patterned substrate 1; a patterned epitaxial buffer layer 3, the patterned epitaxial buffer layer 3 covers the patterned substrate 1, and a plurality of first microstructures 4 are formed on the side of the patterned epitaxial buffer layer 3 facing away from the patterned substrate 1, the first microstructure 4 includes a first heterogeneous material structure 41, and the first heterogeneous material structure 41 is at least located on the top of the first microstructure 4.

[0059] Among them, the patterned substrate 1 is a conventional patterned substrate, such as a patterned sapphire substrate. The patterned epitaxial buffer layer 3 is mainly made of the same material as the epitaxial material, so that the epitaxial material grows homogeneously when growing on the patterned epitaxial buffer layer 3, thereby reducing the lattice defects during the growth of the epitaxial layer. The first heterogeneous material structure 41 in the first microstructure 4 is a part of the microstructure prepared by a heterogeneous material. The heterogeneous material refers to a material different from the epitaxial material, such as silicon dioxide, silicon carbide material, etc., which has a certain refractive index difference with the epitaxial material. The first microstructure 4 on the patterned epitaxial buffer layer 3 is obtained by patterning on a flat substrate and a flat epitaxial buffer layer by etching and the like. There is a certain gap between each first microstructure 4, so that the epitaxial buffer layer and the epitaxial layer grow on the flat C surface between the microstructures.

[0060] The multiple first microstructures 4 arranged on the patterned epitaxial buffer layer 3 can reduce the C-surface area on the epitaxial buffer layer 3, avoid stress concentration and defects during the growth of the epitaxial material, and thus reduce the dislocation density of the epitaxial layer; at the same time, the top of the first microstructure 4 is a first heterogeneous material structure 41, and the heterogeneous material inhibits the growth of the epitaxial material, which can release the stress of the epitaxial material on the top of the first microstructure 4, further avoiding dislocation during epitaxial growth; and, the main material of the patterned epitaxial buffer layer is the epitaxial material, and the epitaxial layer will have a better growth quality due to homogeneous growth during growth. In addition, the multiple first microstructures 4 arranged on the patterned epitaxial buffer layer 3 can reduce the total reflectivity of the light incident from the epitaxial layer at the interface, and at the same time, through the patterned substrate 1, the light passing through the patterned epitaxial buffer layer 3 is further transmitted at the interface, thereby, through the patterned substrate 1 and the first microstructure 4, more light from the epitaxial layer can be emitted, thereby increasing the light extraction efficiency, which helps to improve the external quantum efficiency of the LED chip. Based on this, the patterned composite substrate provided in the embodiment of the present invention can form an epitaxial layer with good quality on the patterned epitaxial buffer layer, thereby ensuring the quality of the epitaxial wafer, while achieving higher light extraction efficiency and improving external quantum efficiency.

[0061] When making epitaxial wafers in subsequent steps, it is necessary to form an epitaxial layer on the patterned composite substrate. In order to make the epitaxial layer and the bottom material of the first microstructure 4 the same, to achieve the effect of homogeneous growth and reduce the lattice mismatch existing when the epitaxial layer grows, it is necessary to ensure that the gaps between the first microstructures 4 expose heterogeneous materials in the actual process design or preparation process. Therefore, optionally, the first microstructure 4 also includes an epitaxial material structure 42 located at the bottom.

[0062] Furthermore, the direction from the patterned substrate 1 toward the patterned epitaxial buffer layer 3 is taken as the first direction; the length ratio of the epitaxial material structure 42 to the first microstructure 4 in the first direction can be set to R, wherein 0%<R≤95%.

[0063] Taking the direction from the patterned substrate 1 toward the patterned epitaxial buffer layer 3 as the first direction, the epitaxial material structure 42 and the first heterogeneous material structure 41 are used to form the first microstructure 4, wherein in the first direction, the length ratio of the epitaxial material structure 42 to the first microstructure 4 is in the range of 0% to 95%, that is, the first microstructure 4 can be formed by only the first heterogeneous material structure 41, or the epitaxial material structure 42 can be selected to form the first microstructure 4 with the first heterogeneous material structure 41 in a certain proportion. Exemplarily, the length ratio of the epitaxial material structure 42 to the first microstructure 4 is in the range of 77%, so that the first microstructure 4 has another 23% of the first heterogeneous material structure 41, which not only effectively suppresses the dislocation phenomenon of the epitaxial material structure 42 during the growth process, but also makes the plane of the gap between the first microstructures 4 the epitaxial material plane, so that when the epitaxial layer is formed later, the effect of homogeneous growth is achieved.

[0064] Figure 3 A schematic diagram of the structure of another patterned composite substrate provided by an embodiment of the present invention is shown in FIG. Figure 3 As shown, optionally, a plurality of second microstructures and / or a plurality of pits 2 are formed on the surface of the patterned substrate 1 , and the patterned epitaxial buffer layer 3 covers the second microstructures and / or the pits 2 .

[0065] The patterned substrate 1 includes a plurality of second microstructures and / or pits 2, which are arranged in a nano / micron pattern array. By setting the second microstructures and / or pits 2, the C-surface area on the epitaxial buffer layer 3 is further reduced, avoiding stress concentration during the growth of the epitaxial material and causing defects, thereby reducing the dislocation density of the epitaxial layer.

[0066] Optionally, the second microstructure 2 includes a second heterogeneous material structure 21 , and the second heterogeneous material structure 21 is at least located on the top of the second microstructure 2 .

[0067] By arranging the second heterogeneous material structure 21 on the top of the second microstructure 2 , the dislocation phenomenon during the growth of the epitaxial material structure 42 on the patterned substrate 1 is effectively suppressed.

[0068] Optionally, the second microstructure 2 and the first microstructure 4 are respectively shaped like at least one of a truncated cone, a cone, a pyramid, a prism and a spherical cap.

[0069] Generally, the shapes of the second microstructure 2 and the first microstructure 4 can be conical. By setting the shapes of the second microstructure 2 and the first microstructure 4 to be conical, the conical microstructures are evenly arranged or arranged in an array, which reduces the total reflection of light at the substrate and the epitaxial interface, ensures the emission of light, helps to improve the light extraction efficiency, and enhances the luminous brightness.

[0070] Optionally, the plurality of second microstructures 2 and the plurality of first microstructures 4 are arranged in an array; the arrangement period of the second microstructures 2 is in the range of 100 nm-10 μm, and the arrangement period of the first microstructures 4 is in the range of 100 nm-10 μm.

[0071] For example, continue to refer to Figure 2 , the arrangement period T2 of the first microstructure 4 is twice the arrangement period T1 of the second microstructure 2. If the arrangement period of the second microstructure 2 and the first microstructure 4 is less than 100nm, the light will be refracted too much due to the too tight arrangement, and the required luminous brightness cannot be achieved. If the arrangement period of the second microstructure 2 and the first microstructure 4 is greater than 10μm, some light cannot be refracted due to the too sparse arrangement. It should be noted that the arrangement period of the second microstructure 2 and the first microstructure 4 is 1:2 only for example. In the actual design and preparation process, the arrangement period of the second microstructure 2 and the first microstructure 4 can be the same, the second microstructure 2 and the first microstructure 4 can correspond to each other one by one or be staggered in sequence, or can be arranged according to other arrangement period ratios to improve the light emission effect through the upper and lower layers of microstructures. Those skilled in the art can further design and experiment, and there is no limitation here.

[0072] Optionally, the bottom diameter D1 of the second microstructure 2 ranges from 500nm to 20μm; the height H1 of the second microstructure 2 ranges from 10nm to 10μm; the bottom diameter D2 of the first microstructure 4 ranges from 500nm to 20μm; the height H2 of the first microstructure 4 ranges from 10nm to 10μm.

[0073] When the bottom diameter D1 of the second microstructure 2 and the bottom diameter D2 of the first microstructure 4 are less than 500nm, and the height H1 of the second microstructure 2 and the height H2 of the first microstructure 4 are less than 10nm, the size of the second microstructure 2 and the first microstructure 4 are too small to produce a refraction effect on the light. When the bottom diameter D1 of the second microstructure 2 and the bottom diameter D2 of the first microstructure 4 are greater than 20μm, and the height H1 of the second microstructure 2 and the height H2 of the first microstructure 4 are greater than 10μm, the size of the second microstructure 2 and the first microstructure 4 are too large, and the refraction effect produced is difficult to meet the requirements. For example, the bottom diameter D1 of the second microstructure 2 is 2.8μm, the height H1 of the second microstructure 2 is 1.8μm, the bottom diameter D2 of the first microstructure 4 is 1.6μm, and the height H2 of the first microstructure 4 is 1μm.

[0074] Optionally, the first heterogeneous material structure 41 is a silicon dioxide structure, a titanium dioxide structure or a zinc oxide structure; the patterned epitaxial buffer layer 3 is a patterned gallium nitride layer; and the patterned substrate 1 is a sapphire patterned substrate.

[0075] Exemplarily, the patterned substrate 1 adopts a sapphire patterned substrate, the patterned epitaxial buffer layer 3 adopts a patterned gallium nitride layer, and the first heterogeneous material structure 41 adopts a silicon dioxide structure. By adopting the silicon dioxide structure as the first heterogeneous material structure 41, the chemical properties of the first heterogeneous material structure 41 are guaranteed to be stable, and the growth of gallium nitride around the first heterogeneous material structure 41 is effectively suppressed.

[0076] The embodiment of the present invention prepares the patterned composite substrate provided by the above embodiment and obtains a test sample. Figure 4 is a local electron microscope image of a patterned composite substrate provided by an embodiment of the present invention, referring to Figure 4 As can be seen from the cross section, the patterned composite substrate includes a patterned substrate 1 and a patterned epitaxial buffer layer 3, wherein the patterned substrate 1 is a patterned sapphire substrate, and the patterned epitaxial buffer layer 3 is made of gallium nitride epitaxial material. A plurality of second microstructures 2 are formed on the surface of the patterned substrate 1, and the patterned epitaxial buffer layer 3 covers the second microstructures 2. As can be seen from the three-dimensional structure, a plurality of first microstructures 4 are formed on the side of the patterned epitaxial buffer layer 3 away from the patterned substrate 1, and the plurality of first microstructures 4 are arranged in an array, and the first microstructure 4 is composed of a first heterogeneous material structure 41, and the heterogeneous material is a silicon dioxide material.

[0077] Figure 5 A schematic diagram of the structure of an LED epitaxial wafer provided by an embodiment of the present invention is shown in FIG. Figure 5 As shown, the LED epitaxial wafer 10 includes the patterned composite substrate 11 described in any one of the above items, and also includes an epitaxial layer 12 located on the patterned composite substrate 11; the patterned composite substrate 11 includes a patterned epitaxial buffer layer 111, and the epitaxial layer 12 is made of the same material as the patterned epitaxial buffer layer 111.

[0078] The LED epitaxial wafer 10 is formed by forming an epitaxial layer 12 on a patterned composite substrate 11, wherein the patterned epitaxial buffer layer 111 and the epitaxial layer 12 in the patterned composite substrate 11 are made of the same material, so that the epitaxial layer 12 has the characteristic of homogeneous growth, weakens the influence of abnormal morphology at the bottom of the pattern, and improves the crystal quality. Exemplarily, the patterned epitaxial buffer layer 111 and the epitaxial layer 12 are both made of gallium nitride material, which has a wurtzite crystal structure, a wide band gap of 3.4 eV, a high breakdown voltage, stable working performance, and low sensitivity to ionizing radiation, reducing the influence of ionizing radiation, and has a high thermal conductivity, and can work in a high temperature environment.

[0079] Figure 6 A schematic diagram of a method for preparing a patterned composite substrate provided by an embodiment of the present invention, Figure 7 A structural flow chart of a method for preparing a patterned composite substrate provided by an embodiment of the present invention, such as Figure 6and Figure 7 As shown, the method for preparing the patterned composite substrate includes:

[0080] S101, providing a flat substrate 1;

[0081] The flat sheet substrate 1 is usually formed by a grinding process and has a flat surface.

[0082] S102, patterning the flat substrate 1 to form a patterned substrate;

[0083] The flat substrate 1 is patterned to form a patterned flat substrate. Exemplarily, the patterned flat substrate is made of sapphire.

[0084] S103, forming an epitaxial buffer layer 3 on the surface of the patterned substrate, wherein the epitaxial buffer layer 3 covers the patterned substrate;

[0085] By metal-organic chemical vapor deposition (MOCVD), an epitaxial buffer layer 3 higher than the patterned substrate is deposited. By setting the epitaxial buffer layer 3, the epitaxial layer formed later is isolated from the patterned flat substrate, thereby alleviating the stress of the epitaxial layer growth. Exemplarily, the epitaxial buffer layer 3 includes gallium nitride material and silicon dioxide material. The gallium nitride material has a high breakdown voltage and stable working performance, which helps to improve the stability of the epitaxial buffer layer. The gallium nitride layer is grown using an MOCVD process, specifically using trimethyl gallium as a Ga source, ammonia as an N source, and nitrogen as a carrier. The temperature is controlled at above 1000°C, the deposition rate is about 1μm / h, and different deposition times are set according to the actual thickness. Exemplarily, the height of the gallium nitride epitaxial buffer layer can be set to 4μm. The silicon dioxide layer is grown by PECVD (plasma enhanced chemical deposition) method, with silane as Si source, N2O as O source, nitrogen as carrier, temperature controlled at 250-300°C, deposition rate 3.6μm / h, and different deposition times set according to actual thickness requirements. For example, the SiO2 thickness can be set to 1.2μm.

[0086] S104, patterning the epitaxial buffer layer 3 to form a patterned epitaxial buffer layer; wherein the patterned epitaxial buffer layer covers the patterned substrate, and a plurality of first microstructures 4 are formed on the side of the patterned epitaxial buffer layer away from the patterned substrate, and the first microstructure 4 includes a first heterogeneous material structure 41, and the first heterogeneous material structure 41 is at least located on the top of the first microstructure 4.

[0087] The epitaxial buffer layer 3 is patterned so that the epitaxial buffer layer 3 forms a plurality of first microstructures 4, wherein the first microstructure 4 may only include the first heterogeneous material structure 41, or may include a portion of the epitaxial buffer layer, so that the top of the first microstructure 4 contains the first heterogeneous material structure 41. Exemplarily, the first microstructure 4 is conical, with a height of 1 μm and a bottom diameter of 1.6 μm. The first heterogeneous material structure 41 effectively suppresses the dislocation phenomenon during the growth of the epitaxial material structure 42, thereby improving the light extraction rate.

[0088] Optionally, step S120, patterning the flat substrate to form a patterned substrate, includes:

[0089] forming a first photoresist layer on a planar substrate;

[0090] Exposing and developing the first photoresist layer with a first preset pattern mask to form a first photoresist mask;

[0091] Etching the flat substrate with a first photoresist mask to form a plurality of second microstructures;

[0092] The first photoresist mask is removed to form the patterned substrate.

[0093] Exemplarily, a layer of photoresist is spin-coated on a flat substrate using photolithography technology combined with inductively coupled plasma (ICP) dry etching technology. The thickness of the photoresist is controlled at 0.8 μm-3 μm according to the required pattern height. A stepper photolithography machine is used for exposure and development to obtain the required mask pattern. The mask pattern is placed on an ICP device for dry etching, so that the flat substrate forms a plurality of second microstructures, and the second microstructure is set to be conical, with a bottom diameter of 2.8 μm and a height of 1.8 μm. Finally, an SPM solution and deionized water are used to remove excess photoresist and the product formed by etching. The SPM solution is a mixture of concentrated sulfuric acid and hydrogen peroxide. The flat substrate is patterned as a growth substrate for epitaxial material, which relieves the stress in the epitaxial growth of epitaxial material, reduces dislocation density, and improves external quantum efficiency.

[0094] Optionally, before patterning the flat substrate to form a patterned substrate, the method further comprises:

[0095] forming a layer of heterogeneous material on a surface of a flat substrate;

[0096] Patterning a flat substrate to form a patterned substrate includes:

[0097] forming a first photoresist layer on the heterogeneous material layer;

[0098] Exposing and developing the first photoresist layer with a first preset pattern mask to form a first photoresist mask;

[0099] Etching the heterogeneous material layer and the flat substrate with a first photoresist mask to form a plurality of second microstructures and / or a plurality of pits;

[0100] The first photoresist mask is removed to form the patterned substrate.

[0101] Optionally, step S103, forming an epitaxial buffer layer on the surface of the patterned substrate, includes:

[0102] forming an epitaxial material layer on the surface of the patterned substrate, wherein the epitaxial material layer covers the patterned substrate;

[0103] A heterogeneous material layer is formed on a surface of the epitaxial material layer that is away from the patterned substrate.

[0104] Exemplarily, a metal organic chemical vapor deposition (MOCVD) technique is used to form an epitaxial material layer on the surface of a patterned substrate, so that the epitaxial material layer completely covers the patterned substrate, and the height of the deposited epitaxial material layer is set to 4 μm. A heterogeneous material layer is formed on the side of the epitaxial material layer away from the patterned substrate by plasma enhanced chemical deposition (PECVD) technology. Preferably, the heterogeneous material layer is made of silicon dioxide material, and the height of the deposited heterogeneous material layer is set to 1.2 μm. A heterogeneous material layer is formed on the epitaxial material layer, and the light extraction efficiency is further improved through the difference in refractive index. At the same time, the subsequent epitaxial growth is made homogeneous, and the abnormal morphology at the bottom of the pattern is weakened to improve the crystal quality.

[0105] Optionally, step S104, patterning the epitaxial buffer layer to form a patterned epitaxial buffer layer, includes:

[0106] Forming a second photoresist layer on a surface of the heterogeneous material layer facing away from the epitaxial material layer;

[0107] exposing and developing the second photoresist layer with a second preset pattern mask to form a second photoresist mask;

[0108] Etching the heterogeneous material layer with a second photoresist mask to form the plurality of first microstructures; wherein the first microstructure includes a first heterogeneous material structure, and the first heterogeneous material structure is at least located on the top of the first microstructure;

[0109] The second photoresist mask is removed to form a patterned epitaxial buffer layer.

[0110] Exemplarily, a layer of photoresist with a height of 1.2 μm is spin-coated on the surface of the side of the heterogeneous material layer away from the epitaxial material layer to form a second photoresist layer. The second photoresist layer is exposed using a stepper lithography machine through a second preset pattern mask and then developed to obtain a second photoresist mask. 100 sccm BCl3 gas is introduced into the ICP device using the second photoresist mask, the chamber pressure is set to 3 mTorr, the upper electrode ionization power is 1400 W, and the lower electrode etching power is 500 W. After 12 minutes of etching time, the heterogeneous material layer is etched to form multiple first microstructures. The first microstructure may include a first heterogeneous material structure and an epitaxial material structure, wherein the first microstructure has a bottom diameter of 1.6 μm, a height of 1 μm, a gallium nitride layer height of 0.2 μm, and a silicon dioxide layer height of 0.8 μm. It may also include only the first heterogeneous material structure, remove excess second photoresist mask, and obtain a patterned epitaxial buffer layer. Alternatively, a second photoresist layer is exposed using a stepper lithography machine through a second preset pattern mask, and then developed to obtain a second photoresist mask, and 100 sccm BCl3 gas is introduced into the ICP device using the second photoresist mask, the chamber pressure is set to 3 mTorr, the upper electrode ionization power is 1400 W, and the lower electrode etching power is 500 W. After 10 minutes of etching time, the heterogeneous material layer is etched to form a plurality of first microstructures, the first microstructures including the first heterogeneous material structure and the epitaxial material structure, wherein the bottom diameter of the first microstructure is 0.8 μm, the height is 0.6 μm, the gallium nitride layer height is 0.2 μm, and the silicon dioxide layer height is 0.4 μm. The lattice mismatch between the patterned substrate and gallium nitride is reduced by patterning the composite substrate, which is conducive to suppressing dislocations during the growth of gallium nitride, and can further improve the external quantum efficiency.

[0111] Optionally, etching the heterogeneous material layer with a second photoresist mask to form the plurality of first microstructures includes:

[0112] The heterogeneous material layer is over-etched with a second photoresist mask to form the plurality of first microstructures; wherein the first microstructure includes a first heterogeneous material structure located at the top and an epitaxial material structure located at the bottom.

[0113] forming a first photoresist layer on the heterogeneous material layer;

[0114] Exposing and developing the first photoresist layer with a first preset pattern mask to form a first photoresist mask;

[0115] Etching the heterogeneous material layer and the flat substrate with a first photoresist mask to form a plurality of second microstructures and / or a plurality of pits;

[0116] The first photoresist mask is removed to form the patterned substrate.

[0117] Preferably, 1.2 μm photoresist or 0.3 μm imprint glue is spin-coated on the heterogeneous material layer, and the photoresist layer is exposed, developed or imprinted with a preset pattern mask to form a photoresist mask, and the photoresist mask is etched with the required glue column mask pattern using ICP etching technology, and finally the photoresist mask is removed to form a plurality of first microstructures, wherein the bottom diameter of the plurality of first microstructures is set to 1.6 μm and the height is set to 1 μm, and in the first microstructures, the bottom epitaxial material structure height is 0.2 μm and the top first heterogeneous material structure height is 0.8 μm.

[0118] Optionally, the direction from the patterned substrate toward the patterned epitaxial buffer layer is taken as the first direction, and the length ratio of the epitaxial material to the first microstructure in the first direction is R, wherein 0%<R≤95%.

[0119] The first microstructure can be composed of only the first heterogeneous material structure, or a certain proportion of the epitaxial material structure can be selected to form the first microstructure together with the first heterogeneous material structure, wherein the first heterogeneous material structure is located on the top of the first microstructure. The first heterogeneous material structure effectively suppresses the dislocation phenomenon in the growth process of the epitaxial material structure, and achieves the effect of homogeneous growth when the epitaxial layer is formed subsequently.

[0120] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by 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 more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A patterned composite substrate, characterized in that: include: Graphic substrate; A patterned epitaxial buffer layer, the patterned epitaxial buffer layer covers the patterned substrate, a plurality of first microstructures are formed on a side of the patterned epitaxial buffer layer away from the patterned substrate, the first microstructure includes a first heterogeneous material structure, the first heterogeneous material structure is at least located on the top of the first microstructure; the first microstructure also includes an epitaxial material structure located at the bottom; the direction from the patterned substrate toward the patterned epitaxial buffer layer is the first direction; the length ratio of the epitaxial material to the first microstructure in the first direction is R, wherein 0%<R≤95%; A plurality of second microstructures and / or a plurality of pits are formed on the surface of the patterned substrate, and the patterned epitaxial buffer layer covers the second microstructures and / or the pits.

2. The patterned composite substrate according to claim 1, characterized in that: The second microstructure includes a second heterogeneous material structure, and the second heterogeneous material structure is at least located on the top of the second microstructure.

3. The patterned composite substrate according to claim 1, characterized in that: The shapes of the first microstructure and the second microstructure are at least one of a truncated cone, a cone, a pyramid, a prism and a spherical cap.

4. The patterned composite substrate according to claim 3, characterized in that: The plurality of second microstructures and the plurality of first microstructures are arranged in an array; The arrangement period of the second microstructure is in the range of 100 nm-10 μm, and the arrangement period of the first microstructure is in the range of 100 nm-10 μm.

5. The patterned composite substrate according to claim 3, characterized in that: The bottom diameter of the second microstructure is in the range of 500nm-20μm; the height of the second microstructure is in the range of 10nm-10μm; The bottom diameter of the first microstructure is in the range of 500 nm-20 μm; the height of the first microstructure is in the range of 10 nm-10 μm.

6. The patterned composite substrate according to claim 1, characterized in that: The first heterogeneous material structure is a silicon dioxide structure, a titanium dioxide structure or a zinc oxide structure; the patterned epitaxial buffer layer is a patterned gallium nitride layer; and the patterned substrate is a sapphire patterned substrate.

7. An LED epitaxial wafer, characterized in that: A patterned composite substrate according to any one of claims 1 to 6, further comprising an epitaxial layer located on the patterned composite substrate; The patterned composite substrate includes a patterned epitaxial buffer layer, and the epitaxial layer is made of the same material as the patterned epitaxial buffer layer.

8. A method for preparing a patterned composite substrate, for preparing the patterned composite substrate as claimed in any one of claims 1 to 6, characterized in that: include: Providing a flat substrate; patterning the flat substrate to form a patterned substrate; forming an epitaxial buffer layer on the surface of the patterned substrate, wherein the epitaxial buffer layer covers the patterned substrate; The epitaxial buffer layer is patterned to form a patterned epitaxial buffer layer; wherein the patterned epitaxial buffer layer covers the patterned substrate, and a plurality of first microstructures are formed on the side of the patterned epitaxial buffer layer away from the patterned substrate, wherein the first microstructure includes a first heterogeneous material structure, and the first heterogeneous material structure is at least located on the top of the first microstructure.

9. The method for preparing a patterned composite substrate according to claim 8, characterized in that: Patterning the flat substrate to form a patterned substrate comprises: forming a first photoresist layer on the flat substrate; Exposing and developing the first photoresist layer with a first preset pattern mask to form a first photoresist mask; Etching the flat substrate with the first photoresist mask to form a plurality of second microstructures and / or a plurality of pits; The first photoresist mask is removed to form the patterned substrate.

10. The method for preparing a patterned composite substrate according to claim 9, characterized in that: Before patterning the flat substrate to form a patterned substrate, the method further comprises: forming a heterogeneous material layer on the surface of the flat substrate; Patterning the flat substrate to form a patterned substrate comprises: forming a first photoresist layer on the heterogeneous material layer; Exposing and developing the first photoresist layer with a first preset pattern mask to form a first photoresist mask; Etching the heterogeneous material layer and the flat substrate with the first photoresist mask to form the plurality of second microstructures and / or a plurality of pits; The first photoresist mask is removed to form the patterned substrate.

11. The method for preparing a patterned composite substrate according to claim 8, characterized in that: Forming an epitaxial buffer layer on the surface of the patterned substrate comprises: forming an epitaxial material layer on the surface of the patterned substrate, wherein the epitaxial material layer covers the patterned substrate; A heterogeneous material layer is formed on a surface of the epitaxial material layer that is away from the patterned substrate.

12. The method for preparing a patterned composite substrate according to claim 11, characterized in that: Patterning the epitaxial buffer layer to form a patterned epitaxial buffer layer, comprising: forming a second photoresist layer on a surface of the heterogeneous material layer facing away from the epitaxial material layer; exposing and developing the second photoresist layer with a second preset pattern mask to form a second photoresist mask; Etching the heterogeneous material layer with the second photoresist mask to form the plurality of first microstructures; wherein the first microstructure includes a first heterogeneous material structure, and the first heterogeneous material structure is at least located on the top of the first microstructure; The second photoresist mask is removed to form the patterned epitaxial buffer layer.

13. The method for preparing a patterned composite substrate according to claim 12, characterized in that: The heterogeneous material layer is etched using the second photoresist mask to form the plurality of first microstructures, comprising: The heterogeneous material layer is over-etched with the second photoresist mask to form the plurality of first microstructures; wherein the first microstructures include a first heterogeneous material structure located at the top and an epitaxial material structure located at the bottom.

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