Multi-structured patterned substrate and method of making the same

Abstract

The application relates to the technical field of semiconductors, and discloses a multi-structure patterned substrate and a preparation method thereof. The preparation method comprises the following steps: depositing a silicon oxide layer on an Al2O3 substrate; coating a stamping adhesive layer on the silicon oxide layer; placing the substrate into a stamping machine to transfer a pattern on a soft film plate to obtain a first preset pattern; performing ICP etching on the first preset pattern to obtain a second preset pattern; performing photoresist coating on the second preset pattern, and performing exposure and development to obtain an adhesive column covering the second preset pattern; baking the substrate with the adhesive column to deform the top of the adhesive column, so that a substrate with a third preset pattern is obtained; depositing an amorphous Al2O3 layer on the substrate with the third preset pattern; and finally, annealing the substrate with the deposited amorphous Al2O3 layer. The pattern structure provided by the application can reduce more total reflection of light, increase the scattering path of light, make more photons find an escape path, and thus improve the light extraction efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a multi-structure patterned substrate and its fabrication method. Background Technology

[0002] Patterned Sapphire Substrates (PSS) is a widely used method to improve the luminous efficiency of GaN-based LED devices. It involves fabricating micro / nano-sized microstructure patterned arrays on sapphire substrates. This method effectively reduces the dislocation density of the GaN epitaxial material, thereby reducing nonradiative recombination in the active region, decreasing reverse leakage current, and improving LED lifetime. Light emitted from the active region is scattered multiple times at the GaN-sapphire substrate interface, altering the exit angle of total internal reflection and increasing the probability of light exiting from both the front (orthogonal) and back (flip) sides, thus improving light extraction efficiency. Simultaneously, the reduced reverse leakage current extends the LED's lifetime.

[0003] The mainstream PSS fabrication process in the market involves using photolithography to create a cylindrical PR mask on a sapphire substrate, followed by dry etching to form a conical PSS. However, existing microstructure patterned arrays have relatively simple structures, mostly consisting of a single Al2O3 structure, which cannot effectively increase the light scattering path, resulting in limited light extraction efficiency after chip fabrication. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a multi-structure patterned substrate and its preparation method, which reduces total internal reflection of light, increases the light scattering path, and improves light extraction efficiency.

[0005] To address the aforementioned technical problems, this invention provides a method for fabricating a multi-structure patterned substrate, comprising the following steps:

[0006] (1) Deposit a silicon oxide layer on the substrate;

[0007] (2) Coat the silicon oxide layer with an imprinting adhesive layer, then bake and cool to room temperature;

[0008] (3) Prepare a soft film plate with an imprinted pattern, and put the soft film plate with the imprinted pattern into an imprinting machine, and introduce nitrogen gas into the top of the soft film plate;

[0009] (4) Place the substrate in the imprinting machine, move the substrate until it comes into contact with the soft film plate, and irradiate it with an ultraviolet lamp to obtain a substrate with a first preset pattern by photocuring.

[0010] (5) Etch the substrate with the first preset pattern to obtain a substrate with the second preset pattern;

[0011] (6) Apply photoresist to form a photoresist layer on the second preset pattern, and then expose and develop to obtain a photoresist pillar covering the second preset pattern;

[0012] (7) The substrate with the adhesive pillars formed is baked, and the top of the adhesive pillars is deformed to obtain a substrate with a third preset pattern;

[0013] (8) An amorphous Al2O3 layer is deposited on a substrate having a third preset pattern, wherein the amorphous Al2O3 layer grows conformally to the third preset pattern;

[0014] (9) Anneal the substrate with the deposited amorphous Al2O3 layer to obtain a multi-structure patterned substrate.

[0015] In some embodiments, the thickness of the silicon oxide layer is 1.5 μm-3 μm;

[0016] The thickness of the imprinting adhesive layer is 0.5μm-2μm;

[0017] The thickness of the photoresist layer is 2μm-3μm;

[0018] The thickness of the amorphous Al2O3 layer is 60nm-100nm.

[0019] In some embodiments, the preparation of the flexible film plate with the embossed pattern includes:

[0020] AB glue is dripped onto a master template, which has a cylindrical shape with a height of 1.5μm-3μm and a width of 1μm-2.5μm.

[0021] The AB adhesive is subjected to vacuuming and then heated and cured at 100℃-150℃. After cooling, a soft film is obtained.

[0022] In some embodiments, placing the substrate in an imprinting machine, moving the substrate until it contacts the flexible film plate, and irradiating it with an ultraviolet lamp to obtain a substrate with a first preset pattern by photocuring includes:

[0023] The substrate is placed on the stage of the imprinting machine, the temperature of the stage is 50℃-120℃, the substrate is moved until it comes into contact with the soft film plate, and it is irradiated with ultraviolet light for 30s-80s. The substrate with the first preset pattern is obtained by photocuring.

[0024] In some embodiments, etching the substrate with the first preset pattern to obtain a substrate with the second preset pattern includes:

[0025] A substrate with a first preset pattern is placed in an ICP dry etching apparatus for etching, wherein BCl3 and CHF3 gases are introduced into the ICP dry etching apparatus.

[0026] After etching, a substrate with a second preset pattern is obtained. The height of the second preset pattern is 0.5μm-2.5μm and the bottom width is 1μm-2.5μm.

[0027] In some embodiments, the gas flow rate of BCl3 is in the range of 80 sccm-200 sccm, the gas flow rate of CHF3 is in the range of 0 sccm-20 sccm, and the gas flow rate ratio of CHF3 / BCl3 is 0-30%.

[0028] The upper electrode power of the ICP dry etching equipment is 500W-2000W, the lower electrode power is 150W-800W, and the pressure is 2.5mT-4mT.

[0029] In some embodiments, the substrate with the adhesive pillars formed is baked at a temperature of 150°C-180°C for 3-10 minutes. After baking, the top of the adhesive pillars deforms to form an arc-shaped surface.

[0030] In some embodiments, the first preset shape is cylindrical; the second preset shape is conical or frustum-shaped.

[0031] The adhesive column covering the second preset pattern is cylindrical;

[0032] The third preset shape is a partial sphere.

[0033] In some embodiments, annealing the substrate with the deposited amorphous Al2O3 layer includes:

[0034] The substrate with the deposited amorphous Al2O3 layer is placed in an annealing furnace and heat-treated at 1050℃-1150℃ for 1-3 hours, and the amorphous Al2O3 layer crystallizes into a single crystal α-Al2O3 layer.

[0035] Accordingly, the present invention provides a multi-structure patterned substrate, the multi-structure patterned substrate including a substrate, on which a plurality of microstructures are formed, the microstructures including a base layer, a silicon oxide layer disposed on the base layer, a single crystal α-Al2O3 layer covering the silicon oxide layer, and an air layer formed between the silicon oxide layer and the single crystal α-Al2O3 layer.

[0036] Implementing this invention has the following beneficial effects:

[0037] The present invention provides a multi-structure patterned substrate and its fabrication method, comprising a substrate on which a plurality of microstructures are formed. Each microstructure includes a base layer, a silicon oxide layer disposed on the base layer, and a single-crystal α-Al₂O₃ layer covering the silicon oxide layer. An air layer is formed between the silicon oxide layer and the single-crystal α-Al₂O₃ layer. Its patterned structure improves upon the traditional single Al₂O₃ layer into a composite multi-structure pattern of Al₂O₃ base layer-silicon oxide layer-air layer-single-crystal α-Al₂O₃ layer, which can reduce total internal reflection of light, increase light scattering paths, and allow more photons to find escape paths, thereby improving light extraction efficiency. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure after step (1) of the embodiment of the present invention is completed;

[0039] Figure 2 This is a schematic diagram of the structure after step (2) of the embodiment of the present invention is completed;

[0040] Figure 3 This is a schematic diagram of the structure after step (4) of the embodiment of the present invention is completed;

[0041] Figure 4 This is a schematic diagram of the structure after step (5) of the present invention is completed;

[0042] Figure 5 This is a schematic diagram of the structure after step (6) of the embodiment of the present invention is completed;

[0043] Figure 6 This is a schematic diagram of the structure after step (7) of the embodiment of the present invention is completed;

[0044] Figure 7 This is a schematic diagram of the structure after step (8) of the present invention is completed;

[0045] Figure 8 This is a schematic diagram of the structure after step (9) of the embodiment of the present invention is completed. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0048] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0049] This invention provides a method for fabricating a multi-structure patterned substrate, comprising the following steps:

[0050] (1) A silicon oxide layer 2 is deposited on the substrate 10;

[0051] (2) Coat the silicon oxide layer 2 with the imprinting adhesive layer 3, then bake and cool to room temperature;

[0052] (3) Prepare a soft film plate with an imprinted pattern, and put the soft film plate with the imprinted pattern into an imprinting machine, and introduce nitrogen gas into the top of the soft film plate;

[0053] (4) Place the substrate 10 into the imprinting machine, move the substrate 10 until it contacts the soft film plate, and irradiate it with an ultraviolet lamp to obtain a substrate with the first preset pattern 4 by photocuring.

[0054] (5) Etch the substrate with the first preset pattern 4 to obtain a substrate with the second preset pattern 5;

[0055] (6) Apply photoresist to form a photoresist layer on the second preset pattern 5, and then expose and develop to obtain a photoresist pillar 6 covering the second preset pattern 5;

[0056] (7) The substrate with the adhesive pillars 6 formed is baked, and the top of the adhesive pillars 6 is deformed to obtain a substrate with a third preset pattern 7;

[0057] (8) An amorphous Al2O3 layer 8 is deposited on a substrate having a third preset pattern 7, wherein the amorphous Al2O3 layer 8 grows conformally to the third preset pattern 7;

[0058] (9) Anneal the substrate with the deposited amorphous Al2O3 layer 8 to obtain a multi-structure patterned substrate.

[0059] In this invention, the multi-structure patterned substrate obtained by the above preparation method, such as Figure 8As shown, the invention includes a substrate 10 on which a plurality of microstructures 20 are formed. Each microstructure 20 includes a base layer 1, a silicon oxide layer 2 disposed on the base layer 1, and a single-crystal α-Al₂O₃ layer 9 covering the silicon oxide layer 2. An air layer 11 is formed between the silicon oxide layer 2 and the single-crystal α-Al₂O₃ layer 9. The base layer 1 is preferably an Al₂O₃ base layer. This invention improves the traditional single Al₂O₃ layer pattern into a composite multi-structure pattern of Al₂O₃ base layer-silicon oxide layer-air layer-single-crystal α-Al₂O₃ layer. This reduces total internal reflection, increases light scattering paths, and allows more photons to find escape paths, thereby improving light extraction efficiency.

[0060] Each step will be explained in detail below.

[0061] Regarding step (1), depositing a silicon oxide layer 2 on the substrate 10;

[0062] Optionally, the substrate 10 is a planar substrate, including but not limited to a sapphire substrate, which is an LED chip substrate material with Al2O3 as the main component.

[0063] In this step, such as Figure 1 As shown, the deposition thickness of the silicon oxide layer 2 is 1.5 μm-3 μm. The deposition process of the silicon oxide layer 2 includes, but is not limited to, atomic layer deposition, plasma-enhanced chemical vapor deposition, and low-pressure chemical vapor deposition. Preferably, the silicon oxide is deposited using an EPEE i800D plasma-enhanced chemical vapor deposition system, which employs a high-density plasma source to achieve rapid deposition. This ensures the uniformity and density of the silicon oxide layer, as well as good interfacial bonding and stress matching with the underlying Al2O3 substrate, and guarantees the consistency of the deposited layer.

[0064] Regarding step (2), an imprinting adhesive layer 3 is coated on the silicon oxide layer 2, then baked and cooled to room temperature;

[0065] like Figure 2 As shown, the thickness of the imprint adhesive layer 3 is 0.5μm-2μm. In this step, through the coating process, specifically, an imprint adhesive layer is spin-coated on the substrate after deposition in step (1), then placed on a hot plate for baking to remove the solvent, and then placed on a cold plate to cool to room temperature. This can uniformly coat the surface of the silicon oxide layer 2 with an imprint adhesive layer 3 that has controllable thickness, good fluidity, and good adhesion to the substrate, which can lay the foundation for the subsequent preparation of high-quality multi-structure patterned substrates.

[0066] Regarding step (3), prepare a soft film plate with an imprinted pattern, place the soft film plate with the imprinted pattern into an imprinting machine, and introduce nitrogen gas into the top of the soft film plate;

[0067] The flexible film plate is placed in a fixed position, and N2 can be introduced above the flexible film plate to give it a certain deformation capability. The deformation of the flexible film plate can be dynamically adjusted to adapt to the slight unevenness on the surface of the silicon oxide layer 2 and improve the uniformity of imprinting. At the same time, the gap between the flexible film plate and the substrate 10 is compensated by deformation, reducing the risk of pattern loss or deformation caused by poor contact.

[0068] In this step, the preparation of the flexible film plate with the imprinted pattern specifically includes the following steps:

[0069] (31) Drop AB glue onto the master template, the master template having a cylindrical shape, the height of the cylindrical shape being 1.5μm-3μm and the width of the cylindrical shape being 1μm-2.5μm;

[0070] (32) The AB glue is vacuumed and heated and cured at 100℃-150℃, and then cooled to obtain a soft film.

[0071] It should be noted that during the curing process of the AB adhesive, a free radical polymerization reaction mainly occurs. Oxygen inhibits the polymerization reaction, leading to incomplete curing or a sticky surface. Therefore, curing under vacuum conditions ensures that the AB adhesive is fully cured, forming a clear pattern, and also avoids defects such as air bubbles that could cause pattern damage or incompleteness. In some embodiments, the AB adhesive may be made of acrylate or epoxy acrylate, but is not limited to these.

[0072] Regarding step (4), the substrate 10 is placed in the imprinting machine, the substrate 10 is moved until it contacts the soft film plate, and it is irradiated with ultraviolet light to obtain a substrate with the first preset pattern 4 by photocuring.

[0073] In some embodiments, the substrate 10 is placed on the stage of the imprinting machine, the stage temperature is 50°C-120°C, the substrate 10 is moved until it comes into contact with the soft film plate, and it is irradiated with an ultraviolet lamp for an exposure time of 30s-80s, and a substrate with a first preset pattern 4 is obtained by photocuring.

[0074] In this step, such as Figure 3 As shown, preferably, the first preset pattern 4 is cylindrical and periodically arranged on the silicon oxide layer 2. By precisely aligning the patterned area of ​​the flexible film with the substrate and applying uniform pressure, the imprinting adhesive fills each cylindrical cavity of the flexible film, ensuring uniform and consistent patterns. Ultraviolet light initiates the polymerization and curing of the imprinting adhesive. The entire process is energy-efficient, fast-curing, and involves one-step patterning. It eliminates the need for complex optical systems, masks, and multiple exposures; a single imprint can form a pattern on the entire substrate, resulting in high production efficiency and low cost.

[0075] It should be noted that the first preset shape 4 can also be other shapes, such as a square column, a truncated cone, etc., and its implementation is not limited to the embodiments described in this invention.

[0076] Regarding step (5), the substrate with the first preset pattern 4 is etched to obtain a substrate with the second preset pattern 5;

[0077] In this step, etching the substrate with the first preset pattern 4 to obtain a substrate with the second preset pattern 5 includes:

[0078] (51) The substrate with the first preset pattern 4 is placed in an ICP dry etching apparatus for etching, wherein BCl3 and CHF3 gases are introduced into the ICP dry etching apparatus;

[0079] (52) After etching, a substrate with a second preset pattern 5 is obtained. The height of the second preset pattern 5 is 0.5μm-2.5μm and the bottom width is 1μm-2.5μm.

[0080] like Figure 4 As shown, preferably, the second preset pattern 5 is conical or frustum-shaped, including a base layer 1 and a silicon oxide layer 2, which are periodically arranged on the substrate. When a sapphire substrate is selected as the substrate, the sapphire substrate is an LED chip substrate material with Al2O3 as the main component, and in this case, the base layer 1 is an Al2O3 base layer.

[0081] It should be noted that the gas flow rate of BCl3 ranges from 80 sccm to 200 sccm, and the gas flow rate of CHF3 ranges from 0 sccm to 20 sccm, with a CHF3 / BCl3 gas flow rate ratio of 0-30%. By adjusting the flow rate and ratio of BCl3 and CHF3, combined with high and low power control, highly selective and anisotropic etching of specific materials can be achieved. BCl3, as the main etching gas, can strongly reduce and volatilize the alumina that is difficult to etch from the material surface. The Cl free radicals generated by its decomposition are the main etching substances, reacting with Al to generate volatile AlCl3. Furthermore, BCl3 can remove residual oxygen and water, improving process stability and repeatability. Setting the BCl3 gas flow rate range to 80 sccm-200 sccm provides sufficient Cl source and cleaning ability, ensuring a high and stable etching rate. CHF3, as the auxiliary gas, decomposes to generate CF... x The polymer deposits on the sidewalls of the etched pattern, forming a protective layer that prevents lateral etching, thus achieving high anisotropy. By setting the CHF3 / BCl3 gas flow rate ratio to 0-30%, a flexible balance can be struck between high etching rate, high anisotropy, and high selectivity, ensuring that the etched pattern is uniform and consistent.

[0082] On the other hand, the upper electrode power of the ICP dry etching equipment is 500W-2000W, the lower electrode power is 150W-800W, and the pressure is 2.5mT-4mT. The high power of the upper electrode generates high-density, highly active free radicals and ions, ensuring a high etching rate. Within the above range, it can meet different needs from rapid coarse etching to fine etching. The lower electrode power independently controls the ion bombardment energy, and within the above range, it can control the thickness of the deposited layer, prevent over-deposition, and keep the bottom of the pattern clean. The low operating pressure helps ensure etching uniformity, improve anisotropy, and reduce polymer deposition.

[0083] Regarding step (6), a photoresist layer is formed on the second preset pattern 5 by applying photoresist, and then exposure and development are performed to obtain a photoresist pillar 6 covering the second preset pattern 5.

[0084] In this step, such as Figure 5 As shown, the photoresist pillar 6 covering the second preset pattern 5 is cylindrical, and the thickness of the photoresist layer is 2μm-3μm. Exposure is the core step in photolithography. First, the photoresist layer must be precisely aligned with the second preset pattern 5 to ensure that the photoresist pillar accurately covers the second preset pattern 5. Furthermore, by optimizing the exposure dosage, insufficient chemical reactions within the photoresist pillar can be avoided, which could lead to tilted sidewalls or residue at the bottom of the pillar after development.

[0085] Regarding step (7), the substrate with the adhesive pillars 6 formed is baked, and the top of the adhesive pillars 6 is deformed to obtain a substrate with a third preset pattern 7.

[0086] In this step, such as Figure 6 The substrate with the photoresist pillars is baked at a temperature of 150℃-180℃ for 3-10 minutes. After baking, the top of the photoresist pillars deforms, forming an arc-shaped surface. The baking temperature is higher than the glass transition temperature (Tg) of the photoresist but lower than its thermal decomposition temperature. If the baking temperature is too low, the photoresist pillars will not flow, and the deformation will be insignificant. If the baking temperature is too high, the photoresist will carbonize and decompose, leading to pattern damage or contamination from impurities. Furthermore, controlling the baking time to 3-10 minutes controls the degree of deformation of the photoresist pillars. If the time is too short, the deformation will be incomplete, and the top of the pillar may only be slightly rounded; if the time is too long, the pillar may collapse entirely.

[0087] Preferably, the third preset shape 7 is a partial sphere. More preferably, the third preset shape 7 is a hemisphere.

[0088] Regarding step (8), an amorphous Al2O3 layer 8 is deposited on a substrate having a third preset pattern 7, wherein the amorphous Al2O3 layer 8 grows conformally to the third preset pattern 7;

[0089] In this step, such as Figure 7 As shown, the thickness of the amorphous Al2O3 layer 8 is 60nm-100nm. In particular, the deposition process is performed on an ALD atomic layer deposition equipment, using H2O and trimethylaluminum (TMA) as oxygen and aluminum sources, respectively. These materials have high reactivity and can quickly form an Al-O bond network at a relatively low temperature of 110°C. On the other hand, at a relatively low temperature, the deposited atoms do not have enough surface migration energy to arrange themselves into an ordered lattice structure. Therefore, the substrate of the third preset pattern 7 is deposited with a long-range disordered amorphous Al2O3 layer 8. Moreover, the atomic layer deposition cycle is 1000 times, with each cycle increasing the thickness by only about 0.1nm. The layer grows two-dimensionally layer by layer, which suppresses the formation and growth of three-dimensional island-like crystal nuclei.

[0090] Regarding step (9), the substrate with the deposited amorphous Al2O3 layer 8 is annealed to obtain a multi-structure patterned substrate.

[0091] In this step, the substrate with the deposited amorphous Al2O3 layer 8 is placed in an annealing furnace and heat-treated at 1050℃-1150℃ for 1-3 hours. Within the above temperature range, the amorphous Al2O3 layer 8 is completely crystallized and achieves excellent crystal quality. Specifically, the amorphous Al2O3 layer 8 crystallizes into a single-crystal α-Al2O3 layer 9. If the temperature is too low, crystallization may be incomplete, and if the temperature is too high, the crystal layer may be excessively rough or undergo side reactions with the substrate. On the other hand, within the above heat treatment time range, it is sufficient for the grains to grow to a certain size and complete structural relaxation. If the time is too long, the grains may be too large or the interface layer may be too thick.

[0092] In addition, such as Figure 8 As shown, an air layer 11 is formed between the silicon oxide layer 2 and the single crystal α-Al2O3 layer 9. As is well known, the refractive index difference between silicon oxide (refractive index n≈1.45) and single crystal α-Al2O3 (refractive index n≈1.76) is limited. However, after inserting an air layer (refractive index n=1), the refractive index difference between the air layer and the upper and lower layers can be increased sharply. Light can be confined within the silicon oxide layer or the single crystal α-Al2O3 layer, which greatly reduces light leakage loss and improves the light extraction efficiency of the LED.

[0093] Accordingly, the present invention provides a multi-structure patterned substrate, the multi-structure patterned substrate including a substrate 10, on which a plurality of microstructures 20 are formed, the microstructures 20 including a base layer 1, a silicon oxide layer 2 disposed on the base layer 1, a single crystal α-Al2O3 layer 9 covering the silicon oxide layer 2, and an air layer 11 formed between the silicon oxide layer 2 and the single crystal α-Al2O3 layer 9.

[0094] In some preferred embodiments, the substrate 10 is an Al2O3 substrate, and a plurality of microstructures 20 are formed on the Al2O3 substrate. The microstructures 20 include a base layer 1, a silicon oxide layer 2 disposed on the base layer 1, and a single crystal α-Al2O3 layer 9 covering the silicon oxide layer 2. An air layer 11 is formed between the silicon oxide layer 2 and the single crystal α-Al2O3 layer 9. The base layer 1 is an Al2O3 base layer.

[0095] Its patterned structure improves upon the traditional single Al2O3 layer into a composite multi-structure pattern of Al2O3 base layer - silicon oxide layer - air layer - single-crystal α-Al2O3 layer. This reduces total internal reflection, increases light scattering paths, and allows more photons to find escape routes, thereby improving light extraction efficiency. Importantly, the microstructure enables lateral epitaxial growth of the semiconductor layer, reducing dislocation density and stress generated during relaxation growth. Furthermore, the microstructure reduces internal total internal reflection caused by material refractive index differences through reflection and diffraction of light generated in the active layer, thus improving LED light extraction efficiency through multiple mechanisms.

[0096] Preferably, the height of the microstructure 20 is 1μm-3.5μm and the width is 1.5μm-3.5μm;

[0097] The thickness of base layer 1 is 0.2μm-0.5μm;

[0098] The thickness of silicon oxide layer 2 is 0.5μm-2.5μm;

[0099] The thickness of the single-crystal α-Al2O3 layer 9 is 50nm-100nm.

[0100] Therefore, due to the differences in refractive index between different materials, the multi-structure pattern on the substrate has a refractive index of about 1.45, an air layer of about 1, and a single-crystal α-Al2O3 layer of about 1.76. Furthermore, the refractive index difference between adjacent layers is relatively large. This can reduce total internal reflection of light compared to a single-structure pattern, increase the light scattering path, and allow more photons to find an escape path, thereby improving the light extraction efficiency. The light can be confined within the silicon oxide layer or the single-crystal α-Al2O3 layer, significantly reducing light leakage loss and improving the light extraction efficiency of the LED.

[0101] The present invention will be further described below with reference to specific embodiments:

[0102] Example 1

[0103] This embodiment provides a method for fabricating a multi-structure patterned substrate, including the following steps:

[0104] (1) A silicon oxide layer is deposited on the substrate, and the thickness of the silicon oxide layer is 1.5 μm;

[0105] (2) A printing adhesive layer is coated on the silicon oxide layer, the thickness of the printing adhesive layer is 1 μm, and then baked and cooled to room temperature;

[0106] (3) Drop AB glue onto the master template, which has a columnar pattern with a height of 1.5 μm and a width of 1 μm. Then, vacuum the AB glue and heat it at 100°C to cure it. After cooling, a soft film is obtained. Finally, the soft film with the imprint pattern is placed in an imprinting machine, and nitrogen gas is introduced into the top of the soft film.

[0107] (4) Place the substrate on the stage of the imprinting machine. The temperature of the stage is 50°C. Move the substrate until it comes into contact with the soft film plate and irradiate it with an ultraviolet lamp for 30 seconds. Obtain a substrate with a first preset pattern by photocuring. The first preset pattern is cylindrical with a height of 1.5 μm and a width of 1 μm, and is periodically arranged on the silicon oxide layer.

[0108] (5) The substrate with the first preset pattern is placed in an ICP dry etching apparatus for etching. The ICP dry etching apparatus is purged with BCl3 and CHF3 gases. The gas flow rate of BCl3 is 80 sccm, the gas flow rate of CHF3 is 20 sccm, the gas flow rate ratio of CHF3 / BCl3 is 25%, the upper electrode power of the ICP dry etching apparatus is 500W, the lower electrode power is 150W, and the pressure is 2.5mT. After etching, a substrate with a second preset pattern is obtained. The second preset pattern is conical with a height of 0.5μm and a bottom width of 1μm.

[0109] (6) Apply photoresist to form a photoresist layer on the second preset pattern, and then expose and develop to obtain a photoresist pillar covering the second preset pattern. The photoresist pillar is cylindrical and the thickness of the photoresist layer is 2μm.

[0110] (7) The substrate with the adhesive pillars formed is baked at 150°C for 3 minutes. After baking, the top of the adhesive pillars deforms and forms a partial sphere, thus obtaining a substrate with a third preset pattern.

[0111] (8) An amorphous Al2O3 layer with a thickness of 60 nm is deposited on a substrate with a third preset pattern, wherein the amorphous Al2O3 layer 8 and the third preset pattern 7 are grown conformally.

[0112] (9) The substrate with the deposited amorphous Al2O3 layer is placed in an annealing furnace and heat-treated at 1050°C for 1 hour to obtain a multi-structure patterned substrate with Al2O3 base layer-silicon oxide layer-air layer-single crystal α-Al2O3 layer.

[0113] Example 2

[0114] This embodiment provides a method for fabricating a multi-structure patterned substrate, which is basically the same as that in Embodiment 1, except that:

[0115] In step (1), the deposition thickness of the silicon oxide layer is 3 μm;

[0116] In step (2), the thickness of the imprinting adhesive layer is 2 μm;

[0117] In step (3), the height of the cylindrical graphic is 3μm and the width of the cylindrical graphic is 2.5μm;

[0118] In step (4), the height of the first preset graphic is 3μm and the width is 2.5μm;

[0119] In step (5), the gas flow rate of BCl3 is 150 sccm, the gas flow rate of CHF3 is 5 sccm, the gas flow rate ratio of CHF3 / BCl3 is 30%, the upper electrode power of the ICP dry etching equipment is 2000W, the lower electrode power is 800W, and the pressure is 4mT; the second preset pattern obtained after etching is a truncated cone shape with a height of 2μm and a bottom width of 2.5μm.

[0120] In step (6), the thickness of the photoresist layer is 3 μm;

[0121] In step (7), the baking temperature is 180°C and the baking time is 10 minutes;

[0122] In step (8), the thickness of the amorphous Al2O3 layer 8 is 100 nm;

[0123] In step (9), the heat treatment temperature is 1150°C and the heat treatment time is 3 hours.

[0124] Example 3

[0125] This embodiment provides a method for fabricating a multi-structure patterned substrate, which is basically the same as that in Embodiment 1, except that:

[0126] In step (1), the deposition thickness of the silicon oxide layer is 2 μm;

[0127] In step (2), the thickness of the imprinting adhesive layer is 0.5 μm;

[0128] In step (3), the height of the cylindrical graphic is 2.5 μm and the width of the cylindrical graphic is 2 μm;

[0129] In step (4), the height of the first preset graphic is 2.5 μm and the width is 2 μm;

[0130] In step (5), the gas flow rate of BCl3 is 80 sccm, the gas flow rate of CHF3 is 15 sccm, the gas flow rate ratio of CHF3 / BCl3 is 18.75%, the upper electrode power of the ICP dry etching equipment is 1500W, the lower electrode power is 500W, and the pressure is 3mT; the second preset pattern obtained after etching is a truncated cone shape with a height of 1μm and a bottom width of 1.5μm.

[0131] In step (6), the thickness of the photoresist layer is 2.5 μm;

[0132] In step (7), the baking temperature is 160°C and the baking time is 5 minutes;

[0133] In step (8), the thickness of the amorphous Al2O3 layer 8 is 80 nm;

[0134] In step (9), the heat treatment temperature is 1100℃ and the heat treatment time is 2 hours.

[0135] Comparative Example 1

[0136] A multi-structure patterned substrate, the preparation method of which differs from that of Example 1, omits steps (6) to (9).

[0137] Comparative Example 1 of the present invention provides a multi-structure patterned substrate, which has a single crystal α-AL2O3 layer without a covering silicon oxide layer and an air layer between them, and the substrate structure is an Al2O3 base layer-silicon oxide layer.

[0138] Comparative Example 2

[0139] A multi-structure patterned substrate, the preparation method of which differs from that of Example 1, wherein in step (9), the annealing temperature is 1300℃ and the time is 3.5h.

[0140] Comparative Example 3

[0141] A multi-structure patterned substrate, the preparation method of which differs from that of Example 1, wherein in step (9), the annealing temperature is 800°C and the time is 4h.

[0142] The performance tests of Examples 1-3 and Comparative Examples 1-3 were compared, and the results are as follows:

[0143] (1) Test method:

[0144] Epitaxial layers were deposited on the composite patterned substrates obtained in the examples and comparative examples using the same process, and 10mil×24mil chips were fabricated using the same chip process conditions. 300 LED chips were extracted from each substrate, and the emission angle and luminance were tested at a current of 120mA. The specific test results are shown in Table 1.

[0145] (2) Test results:

[0146] Table 1 Performance test results of the examples and comparative examples

[0147]

[0148] As can be seen from the above, the embodiment of the present invention is a composite multi-structure pattern of Al2O3 base layer-silicon oxide layer-air layer-single crystal α-Al2O3 layer. Due to the difference in refractive index between different materials, more total internal reflection of light can be reduced, the light scattering path can be increased, and more photons can find an escape path, which can further improve the luminous efficiency and luminous brightness of the chip, thereby improving the light extraction efficiency.

[0149] The Al2O3 base layer-silicon oxide layer patterned substrate provided in Comparative Example 1 of this invention has no single-crystal α-AL2O3 layer covering the silicon oxide layer and no air layer between them. A large amount of light will leak out in the form of total internal reflection, resulting in high light loss, poor luminous efficiency and brightness, and low light extraction efficiency of LEDs.

[0150] Comparative Example 2 of this invention provides a multi-structure patterned substrate. The substrate structure consists of an Al2O3 base layer, a silicon oxide layer, an air layer, and a polycrystalline Al2O3 layer. Due to excessively high annealing temperature and time, the amorphous Al2O3 layer rapidly forms a polycrystalline structure with coarse grains and numerous defects, making it almost impossible to obtain a single crystal. Although fully crystallized, it does not achieve excellent crystal quality, and the crystalline layer is excessively rough. Due to its polycrystalline structure, most of the light is scattered and its path is altered, preventing it from exiting at an effective angle, which has a significant negative impact on the light extraction efficiency of the LED.

[0151] The present invention provides a multi-structure patterned substrate in Comparative Example 3. The substrate structure is Al2O3 base layer-silicon oxide layer-air layer-dense amorphous Al2O3 layer. Due to the low temperature, the crystallization is incomplete. The annealing temperature is insufficient to overcome the energy barrier required for atoms to migrate from the amorphous state to the crystalline state. The atoms can only undergo local structural relaxation, making the amorphous network more stable and dense. However, a long-range ordered lattice cannot be formed. In the end, the outermost layer is a dense amorphous state. However, the refractive index of the amorphous state is not fixed. Although an air layer is inserted, the light extraction efficiency is worse than that of Example 1.

[0152] The above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Therefore, those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered within the scope of protection.

Claims

1. A method for fabricating a multi-structure patterned substrate, characterized in that, Includes the following steps: (1) Deposit a silicon oxide layer on the substrate; (2) Coat the silicon oxide layer with an imprinting adhesive layer, then bake and cool to room temperature; (3) Prepare a soft film plate with an imprinted pattern, and put the soft film plate with the imprinted pattern into an imprinting machine, and introduce nitrogen gas into the top of the soft film plate; (4) Place the substrate in the imprinting machine, move the substrate until it comes into contact with the soft film plate, and irradiate it with an ultraviolet lamp to obtain a substrate with a first preset pattern by photocuring. (5) Etch the substrate with the first preset pattern to obtain a substrate with the second preset pattern; (6) Apply photoresist to form a photoresist layer on the second preset pattern, and then expose and develop to obtain a photoresist pillar covering the second preset pattern; (7) The substrate with the adhesive pillars formed is baked, and the top of the adhesive pillars is deformed to obtain a substrate with a third preset pattern; (8) An amorphous Al2O3 layer is deposited on a substrate having a third preset pattern, wherein the amorphous Al2O3 layer grows conformally to the third preset pattern; (9) Anneal the substrate with the deposited amorphous Al2O3 layer, and the amorphous Al2O3 layer crystallizes into a single crystal α-Al2O3 layer to obtain a multi-structure patterned substrate. The multi-structure patterned substrate includes a substrate on which several microstructures are formed. Each microstructure includes a base layer, a silicon oxide layer disposed on the base layer, and a single-crystal α-Al2O3 layer covering the silicon oxide layer. An air layer is formed between the silicon oxide layer and the single-crystal α-Al2O3 layer.

2. The method for fabricating a multi-structure patterned substrate as described in claim 1, characterized in that, The thickness of the silicon oxide layer is 1.5 μm-3 μm; The thickness of the imprinting adhesive layer is 0.5μm-2μm; The thickness of the photoresist layer is 2μm-3μm; The thickness of the amorphous Al2O3 layer is 60nm-100nm.

3. The method for fabricating a multi-structure patterned substrate as described in claim 1, characterized in that, The preparation of the flexible film plate with the embossed pattern includes: AB glue is dripped onto a master template, which has a cylindrical shape with a height of 1.5μm-3μm and a width of 1μm-2.5μm. The AB adhesive is subjected to vacuuming and then heated and cured at 100℃-150℃. After cooling, a soft film is obtained.

4. The method for fabricating a multi-structure patterned substrate as described in claim 1, characterized in that, The step of placing the substrate in an imprinting machine, moving the substrate until it contacts the flexible film plate, and irradiating it with an ultraviolet lamp to obtain a substrate with a first preset pattern by photocuring includes: The substrate is placed on the stage of the imprinting machine, the temperature of the stage is 50℃-120℃, the substrate is moved until it comes into contact with the soft film plate, and it is irradiated with ultraviolet light for 30s-80s. The substrate with the first preset pattern is obtained by photocuring.

5. The method for fabricating a multi-structure patterned substrate as described in claim 1, characterized in that, The etching of a substrate with a first preset pattern to obtain a substrate with a second preset pattern includes: A substrate with a first preset pattern is placed in an ICP dry etching apparatus for etching, wherein BCl3 and CHF3 gases are introduced into the ICP dry etching apparatus. After etching, a substrate with a second preset pattern is obtained. The height of the second preset pattern is 0.5μm-2.5μm and the bottom width is 1μm-2.5μm.

6. The method for fabricating a multi-structure patterned substrate as described in claim 5, characterized in that, The gas flow rate of BCl3 is in the range of 80 sccm-200 sccm, the gas flow rate of CHF3 is in the range of 0 sccm-20 sccm, and the gas flow rate ratio of CHF3 / BCl3 is 0-30%. The upper electrode power of the ICP dry etching equipment is 500W-2000W, the lower electrode power is 150W-800W, and the pressure is 2.5mT-4mT.

7. The method for fabricating a multi-structure patterned substrate as described in claim 1, characterized in that, The substrate with the adhesive pillars is baked at a temperature of 150℃-180℃ for 3-10 minutes. After baking, the top of the adhesive pillars deforms to form an arc-shaped surface.

8. The method for fabricating a multi-structure patterned substrate as described in claim 1, characterized in that, The first preset shape is cylindrical; the second preset shape is conical or frustum-shaped. The adhesive column covering the second preset pattern is cylindrical; The third preset shape is a partial sphere.

9. The method for fabricating a multi-structure patterned substrate as described in claim 1, characterized in that, The annealing of the substrate with the deposited amorphous Al2O3 layer includes: The substrate with the deposited amorphous Al2O3 layer is placed in an annealing furnace and heat-treated at 1050℃-1150℃ for 1-3 hours, and the amorphous Al2O3 layer crystallizes into a single crystal α-Al2O3 layer.

10. A multi-structure patterned substrate prepared by the preparation method according to any one of claims 1-9, characterized in that, The multi-structure patterned substrate includes a substrate on which several microstructures are formed. Each microstructure includes a base layer, a silicon oxide layer disposed on the base layer, and a single-crystal α-Al₂O₃ layer covering the silicon oxide layer. An air layer is formed between the silicon oxide layer and the single-crystal α-Al₂O₃ layer.

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