Novel deep ultraviolet LED and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor manufacturing, in particular to a novel deep ultraviolet LED and a preparation method thereof.The preparation method comprises the steps that the surface of an epitaxial wafer is plated with a mask layer, a stripping sacrificial layer is arranged on the mask layer, and an imprinting layer is arranged on the stripping sacrificial layer; on the basis of a nanoimprinting method, the nanopillar array pattern is transferred to the imprinting layer to form a nanopore array pattern; after demolding treatment is conducted, the imprinting layer serves as a mask, the mask layer is etched, and the nanopore array pattern is transferred to the mask layer; removing and stripping the sacrificial layer and the imprinting layer, etching the p-type semiconductor layer of the epitaxial wafer, transferring the nanopore array pattern to the p-type semiconductor layer and forming an array micro-nano structure, and then removing the residual mask layer; periodic electrodes in a square array are arranged on an epitaxial wafer with an array micro-nano structure, and the periodic electrodes cover part of the micro-nano structure. The LED prepared by the method can effectively break through the critical angle of total reflection of an interface, and the front light extraction and emission performance of deep ultraviolet is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a novel deep ultraviolet LED and a preparation method thereof. Background Art

[0002] In recent years, deep ultraviolet light-emitting diodes (DUV-LEDs) have demonstrated significant application value in areas such as surface disinfection, water purification, UV communications, and high-density lithography. However, existing fabrication technologies still face significant bottlenecks, hindering further breakthroughs in device performance and their industrial application.

[0003] Improvements in deep-UV LED crystal growth processes have significantly increased the internal quantum efficiency of deep-UV LEDs. However, due to the large refractive index difference between the GaN material and the air interface, as well as the inherent optical anisotropy of the active region, the vast majority of deep-UV photons are confined within the device, resulting in limited light extraction efficiency. In particular, very few photons escape from the front of the device. Therefore, improving light extraction from deep-UV LEDs has become a pressing technical challenge in this field.

[0004] It should be noted that the information disclosed in this background technology section is only intended to increase understanding of the overall background of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art. Summary of the Invention

[0005] In order to solve the difficulties of the prior art, the present invention aims to provide a preparation method for improving the performance of deep ultraviolet LEDs by nanoimprinting, so as to overcome the defects in the prior art. The present invention uses nanoimprinting technology to accurately prepare micro-nano structures with small size and high aspect ratio, effectively improving the light extraction efficiency of deep ultraviolet LEDs. Nanoimprinting technology can achieve the advantage of nanoscale resolution and prepare micro-nano structures with characteristic sizes between 50-200nm, greatly improving the propagation path of light inside the chip, breaking the total reflection limitation, and enabling more light to be effectively emitted. At the same time, compared with traditional photolithography technology, the process steps of nanoimprinting technology are simpler and the equipment cost is relatively low, which can significantly reduce the preparation cost of deep ultraviolet LEDs and promote their wide application in various fields.

[0006] The present invention provides a method for preparing a novel deep ultraviolet LED, which comprises the following steps: coating a mask layer on the surface of an epitaxial wafer, arranging a stripping sacrificial layer on the mask layer, and arranging an imprinting layer on the stripping sacrificial layer; transferring a nanocolumn array pattern to the imprinting layer based on a nanoimprinting method to form a nanohole array pattern; performing a demoulding process, etching the mask layer using the imprinting layer as a mask, and transferring the nanohole array pattern to the mask layer; removing the stripping sacrificial layer and the imprinting layer, etching a p-type semiconductor layer of the epitaxial wafer using the mask layer as a mask, transferring the nanohole array pattern to the p-type semiconductor layer and forming an array micro-nano structure, and then removing the remaining mask layer; and arranging periodic electrodes in a square array on the epitaxial wafer having the array micro-nano structure, wherein the periodic electrodes cover a portion of the micro-nano structure.

[0007] Furthermore, the material of the mask layer includes silicon oxide, aluminum oxide or polyimide.

[0008] Furthermore, the thickness of the mask layer is 200-250 nm.

[0009] Furthermore, the material for stripping the sacrificial layer includes PMGI glue.

[0010] Furthermore, the material of the embossing layer includes embossing glue.

[0011] Furthermore, the absorption coefficient of the periodic electrode is in the range of 10 4 ~10 5 cm -1 .

[0012] Furthermore, after completing the step of removing the remaining mask layer, the following steps are also included: placing the epitaxial wafer in a coater and spin-coating a thickening liquid and a photoresist in sequence; baking the spin-coated epitaxial wafer, setting the temperature to 80~120℃ and the time to 2~7 minutes; photolithography of the epitaxial wafer; placing the exposed pattern in a developer for dissolution for 1~3 minutes; cleaning the dissolved epitaxial wafer to obtain the desired photolithography pattern; and performing ICP etching on the epitaxial wafer with the photolithography pattern to form a mesa structure.

[0013] Furthermore, the material of the periodic electrodes includes nickel and gold.

[0014] Furthermore, the square array includes a rectangular pattern with a period of 75 μm, a rectangular pattern with a period of 30 μm, a rectangle with a period of 75 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line, a rectangle with a period of 50 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line, or a rectangle with a period of 30 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line.

[0015] The present invention also provides a novel deep ultraviolet LED, which is prepared by using the preparation method of a novel deep ultraviolet LED as described in any of the above items.

[0016] This invention provides a novel deep ultraviolet LED and its fabrication method, employing nanoimprinting technology to precisely fabricate micro-nanostructures with high aspect ratios of 50-200nm, breaking through the resolution limitations of traditional photolithography. By regulating the light field propagation path through surface micro-nanostructures, the critical angle for total internal reflection at the interface is effectively exceeded, significantly improving the frontal light extraction and emission performance of deep ultraviolet light. Simultaneously, the nanoimprinted micro-nanostructures are combined with periodic electrodes to form a light-transmitting conductive network in the electrode region. This design not only improves electrode conductivity but also compensates for light absorption losses through the scattering effect of the micro-nanostructures, achieving simultaneous optimization of light extraction efficiency and electrical performance.

[0017] Other features and beneficial effects of the present invention will be described in the following description, and some of the technical features and beneficial effects can be obviously derived from the description or understood by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, some of the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 This is a schematic flow chart of a novel deep ultraviolet LED manufacturing method provided by one embodiment of the present invention; Figure 2 It is a local SEM image of the micro-nanostructure and periodic electrodes; Figure 3 Schematic diagram of multiple control experiments provided by the present invention; Figure 4 It is a schematic diagram of multiple groups of square arrays provided by the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "center", "lateral", "up", "down", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In addition, the term "including" and any variations thereof all mean "at least including".

[0022] See also Figures 1 to 3 , Figure 1 This is a flow chart of a novel deep ultraviolet LED manufacturing method provided by one embodiment of the present invention. Figure 2 This is a local SEM image of the micro-nano structure and periodic electrodes. Figure 3 Schematic diagram of multiple control experiments provided by the present invention. As shown in the figure, a novel method for preparing deep ultraviolet LEDs provided by one embodiment of the present invention includes the following steps: S100: A mask layer is deposited on the surface of the epitaxial wafer, a lift-off sacrificial layer is disposed on the mask layer, and an imprint layer is disposed on the lift-off sacrificial layer. Specifically, a 200nm thick SiO2 mask layer can be deposited on the epitaxial wafer surface via a PECVD process, followed by spin-coating of PMGI glue as the lift-off sacrificial layer; and then spin-coating of TU2-170 glue as the imprint layer. Optionally, the mask layer can be made of silicon oxide, aluminum oxide, or polyimide. The mask layer has a thickness of 200nm. The lift-off sacrificial layer can be made of PMGI glue (polymethyl glutarimide). The imprint layer can be made of an imprint glue, such as TU2-170 glue. In some embodiments, the mask layer can be 200-250nm thick. The thickness of the mask layer can be equal to (2k + 1)λ / 4n, which is used to calculate the optimal passivation thickness, where λ and n are the incident light wavelength and refractive index of the dielectric material, respectively.

[0023] Before performing step S100, the epitaxial wafer may be cleaned as follows: first, the epitaxial wafer is placed in an acetone solution for ultrasonic treatment for 5 minutes, with an ultrasonic power of 240 W and a temperature of 25-40°C; after taking out the epitaxial wafer, the epitaxial wafer is placed in anhydrous ethanol and deionized water for ultrasonic treatment in turn, for the same time of 5 minutes, with an ultrasonic power of 240 W and a temperature of 25-40°C; the cleaned epitaxial wafer is blown dry with nitrogen.

[0024] S200: Using a nanoimprint method, the nanopillar array pattern is transferred to the imprint layer to form a nanopore array pattern. Specifically, a nanoimprint system (such as the Obducat Eitre 6 Nanoimprint System) can be used to transfer the nanopillar array pattern on the IPS soft template to the imprint layer using UV hot embossing mode to form a nanopore array pattern.

[0025] S300: After demolding, the mask layer is etched using the imprint layer as a mask to transfer the nanopore array pattern to the mask layer. Specifically, demolding can be performed after imprinting is completed. After demolding, CHF3 is used in an ICP system to etch the SiO2 mask layer using the imprint layer as a mask to transfer the nanopore array pattern to the mask layer.

[0026] S400: Remove the sacrificial and imprinted layers, and using the mask layer as a mask, etch the p-type semiconductor layer of the epitaxial wafer, transferring the nanohole array pattern to the p-type semiconductor layer and forming an array micro-nanostructure. The remaining mask layer is then removed. Specifically, acetone can be used to remove the sacrificial and imprinted layers. Then, in an ICP system, using the SiO2 mask layer as a mask, use Cl2 / BCl3 gas to etch the p-type semiconductor layer of the epitaxial wafer to a depth of 250-500nm, transferring the nanohole array pattern to the p-type semiconductor layer. Next, dilute hydrofluoric acid is used to remove the remaining mask layer, completing the preparation of the surface array micro-nanostructure.

[0027] Furthermore, after the step of removing the remaining mask layer is completed, the following steps may be further included: Place the epitaxial wafer in a spin coater and spin-coat the thickening solution and photoresist. Specifically, after drying the epitaxial wafer, place the intact structure in the spin coater and spin-coat the thickening solution and photoresist. Set the spin coater speed to a low speed of 500-1500 rpm for 2-5 seconds, or a high speed of 2000-3500 rpm for 20-40 seconds.

[0028] Bake the spin-coated epitaxial wafer at a temperature of 80-120°C for 2-7 minutes.

[0029] The epitaxial wafer is photolithographically etched to form the required square mesa shape.

[0030] The exposed pattern is placed in a developer for dissolution for 1 to 3 minutes.

[0031] After the dissolved epitaxial wafer is cleaned, the desired photolithographic pattern is obtained.

[0032] The epitaxial wafer with the photolithography pattern is subjected to ICP etching to form a mesa structure.

[0033] After cleaning the etched epitaxial wafer, the epitaxial wafer is photoetched and developed using a laser direct writing lithography system to obtain an electrode photolithography pattern, and then plated with titanium aluminum titanium metal.

[0034] S500: A periodic electrode in a square array is arranged on an epitaxial wafer having an array of micro-nano structures, with the periodic electrode covering part of the micro-nano structure. Specifically, a laser direct write lithography system can be used to perform photolithography on the epitaxial wafer, with a lithography line width of 3-5 μm. The intersections between the lines are composed of small circles with a diameter of 10-20 μm, and a composite periodic structure is formed by combining dots and lines: the exposed pattern is placed in a developer and dissolved for 1-3 minutes; the dissolved epitaxial wafer is rinsed with pure water and then blown dry with nitrogen to obtain the desired photolithographic pattern; the epitaxial wafer with the photolithographic pattern is subjected to ICP etching and then plated with nickel and gold to obtain the periodic electrode. In this embodiment, the photolithographic pattern is located in the middle of the hole injection layer of the P-type semiconductor layer. It is distributed at equal intervals and consists of 36 rectangular grids (6 horizontally and 6 vertically). The rectangular grid is a square structure composed of four rectangular sides, and its side length is 50 μm. The width of the rectangular side line is 4 μm, and the intersection of the ends of the rectangular sides is connected by dots with a diameter of 15 μm, and the dots and lines are combined to form a composite periodic structure.

[0035] refer to Figure 2 As shown, Figure 2 The holes in the nanostructure are micro-nano structures. Figure 2The transparent structure covering the holes in the middle right half is a periodic electrode. The present invention uses nanoimprinting technology to achieve the precise preparation of 50-200nm-level high aspect ratio micro-nanostructures, breaking through the resolution limitations of traditional photolithography. By regulating the light field propagation path through the surface micro-nanostructure, the critical angle of total reflection at the interface is effectively broken, greatly improving the front light extraction and emission performance of deep ultraviolet light; at the same time, the micro-nanostructure formed by nanoimprinting is combined with the periodic electrode to form a light-transmitting conductive network in the electrode area. This design not only improves the conductivity of the electrode, but also compensates for the light absorption loss through the scattering effect of the micro-nanostructure, which can achieve the simultaneous optimization of light extraction efficiency and electrical performance.

[0036] When using photolithography to fabricate micro- and nanostructures, its resolution is limited by the diffraction limit. When fabricating the high-precision nanostructures required for deep ultraviolet wavelengths, photolithography struggles to precisely control the size and spatial arrangement of the structures, significantly reducing the ability to manipulate the light field and impairing light extraction.

[0037] In some embodiments, the absorption coefficient of the periodic electrodes is in the range of 10 4 ~10 5 cm -1 For example, 1cm -1 This means that the light intensity decays to 1 / e of its original value after penetrating 1 cm of thickness. The periodic electrodes are made of nickel and gold.

[0038] See Figure 3 As shown in the figure, the IV characteristic curves of multiple composite periodic electrodes of different sizes and traditional disk electrodes are shown. It can be seen from the figure that compared with the traditional disk electrode (C0), the composite periodic electrode exhibits better performance and can achieve simultaneous optimization of light extraction efficiency and electrical performance.

[0039] In some embodiments, reference Figure 4 As shown, the square array includes a rectangular pattern A1 with a period of 75 μm, a rectangular pattern A2 with a period of 50 μm, a rectangular pattern A3 with a period of 30 μm, a rectangular pattern B1 with a period of 75 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line, a rectangular pattern B2 with a period of 50 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line, or a rectangular pattern B3 with a period of 30 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line. Figure 3 A1~B3 in Figure 4 The corresponding square array.

[0040] The present invention also provides a novel deep ultraviolet LED, which is prepared by using the preparation method of a novel deep ultraviolet LED as described in any of the above items.

[0041] In summary, the present invention provides a novel deep ultraviolet LED and its preparation method, which uses nanoimprinting technology to achieve the precise preparation of 50-200nm-level high-aspect ratio micro-nanostructures, breaking through the resolution limitations of traditional photolithography. By regulating the light field propagation path through surface micro-nanostructures, the critical angle of total internal reflection at the interface is effectively broken, significantly improving the front light extraction and emission performance of deep ultraviolet. At the same time, the micro-nanostructure formed by nanoimprinting is combined with periodic electrodes to form a light-transmitting conductive network in the electrode area. This design not only improves the conductivity of the electrode, but also compensates for light absorption loss through the scattering effect of the micro-nanostructure, achieving the simultaneous optimization of light extraction efficiency and electrical performance.

[0042] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention may be improved in only one or several aspects, without having to simultaneously solve all the technical problems listed in the prior art or background art. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as limiting the claim.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a novel deep ultraviolet LED, characterized by: The preparation method of the novel deep ultraviolet LED comprises the following steps: Plating a mask layer on the surface of the epitaxial wafer, arranging a stripping sacrificial layer on the mask layer, and arranging an imprinting layer on the stripping sacrificial layer; Based on the nanoimprint method, the nanopillar array pattern is transferred to the imprint layer to form a nanohole array pattern; After demolding, the mask layer is etched using the imprint layer as a mask to transfer the nanopore array pattern onto the mask layer; removing the stripping sacrificial layer and the imprinting layer, etching the p-type semiconductor layer of the epitaxial wafer using the mask layer as a mask, transferring the nanohole array pattern onto the p-type semiconductor layer to form an array micro-nano structure, and then removing the remaining mask layer; Periodic electrodes in a square array are arranged on the epitaxial wafer having the array micro-nano structure, and the periodic electrodes cover a portion of the micro-nano structure.

2. The method for preparing a novel deep ultraviolet LED according to claim 1, wherein: The material of the mask layer includes silicon oxide, aluminum oxide or polyimide.

3. The method for preparing a novel deep ultraviolet LED according to claim 1, wherein: The thickness of the mask layer is 200-250 nm.

4. The method for preparing a novel deep ultraviolet LED according to claim 1, wherein: The material for peeling off the sacrificial layer includes PMGI glue.

5. The method for preparing a novel deep ultraviolet LED according to claim 1, wherein: The material of the embossing layer includes embossing glue.

6. The method for preparing a novel deep ultraviolet LED according to claim 1, wherein: The absorption coefficient of the periodic electrode is in the range of 10 4 ~10 5 cm -1 .

7. The method for preparing a novel deep ultraviolet LED according to claim 1, wherein: After completing the step of removing the remaining mask layer, the method further includes the following steps: Placing the epitaxial wafer in a spin coater and sequentially spin coating the viscosity enhancing liquid and the photoresist; Bake the spin-coated epitaxial wafer at 80-120°C for 2-7 minutes. performing photolithography on the epitaxial wafer; The exposed pattern is placed in a developer for 1 to 3 minutes to dissolve; After cleaning the dissolved epitaxial wafer, the desired photolithographic pattern is obtained; The epitaxial wafer with the photolithography pattern is subjected to ICP etching to form a mesa structure.

8. The method for preparing a novel deep ultraviolet LED according to claim 1, wherein: The material of the periodic electrodes includes nickel and gold.

9. The method for preparing a novel deep ultraviolet LED according to claim 1, wherein: The square array includes a rectangular pattern with a period of 75 μm, a rectangular pattern with a period of 30 μm, a rectangle with a period of 75 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line, a rectangle with a period of 50 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line, or a rectangle with a period of 30 μm and a dot-line combination pattern in which the center of the rectangle is connected to the edge line.

10. A novel deep ultraviolet LED, characterized by: The novel deep ultraviolet LED is prepared by using a preparation method of a novel deep ultraviolet LED as described in any one of claims 1-9.

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