Deep ultraviolet LED chip of P-GaN material embedded structure and preparation method of deep ultraviolet LED chip

Abstract

The invention belongs to the technical field of deep ultraviolet LED chips, and particularly relates to a deep ultraviolet LED chip of a P-GaN material embedded structure and a preparation method of the deep ultraviolet LED chip of the P-GaN material embedded structure. Etching the epitaxial layer through ICP; the P-AlGaN thin film is etched through ICP, and the area where the P-AlGaN thin film is etched is an area I; sputtering an AlN thin film; the AlN thin film is etched through ICP; a P-GaN thin film is deposited through MOCVD; the P-GaN thin film outside the second area is etched away; preparing N gold on the surface of the N-AlGaN thin film, preparing P gold on the surface of the P-GaN thin film in the second area, and finally preparing the independent deep ultraviolet LED chip through grinding, polishing and scratching. The laminated structure of the P-AlGaN thin film and the P-GaN thin film is designed into an embedded structure, so that the ohmic contact characteristic of P-GaN and a metal electrode is ensured, and the light absorption area of the P-GaN thin film is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of deep ultraviolet LED chips, and specifically relates to a deep ultraviolet LED chip with a P-GaN material embedded structure and a preparation method thereof. Background Art

[0002] In recent years, deep ultraviolet LED technology based on AlGaN materials has made continuous breakthroughs, gradually replacing mercury lamps and becoming a new generation of ultraviolet light sources. However, there are still technical bottlenecks in light extraction efficiency and electro-optical conversion efficiency, which have become key factors restricting the development of the deep ultraviolet LED (especially UVB and UVC) industry.

[0003] In the flip-chip deep ultraviolet LED chip structure, the factors that affect light extraction mainly include the following aspects: 1) The refractive index of AlN, n-AlGaN (n=2.16~2.6), sapphire (n is about 1.8), and air (n=1) in the epitaxial material. Due to the large difference in the refractive index of the media, total reflection is likely to occur at the epitaxial layer / sapphire / air interface, and most of the light is likely to be confined inside the epitaxial structure. However, since the sapphire substrate has the advantages of hexagonal symmetry, non-absorption of ultraviolet light, high temperature resistance, high crystal quality, and low cost, comprehensive consideration will make sapphire substrate the best choice for deep ultraviolet epitaxial materials in the short term. 2) The epitaxial material P-GaN absorbs deep ultraviolet light. The researchers used a positive chip structure to reduce the thickness of the p-GaN layer, which is transparent to 280nm ultraviolet light, and reduced the absorption rate of the p-type layer from 10 5 / cm is reduced to less than 1000 / cm, and the transmittance of the p-type layer is increased from 5% to 60%, greatly improving the light extraction efficiency. According to the intrinsic absorption long-wave limit formula, P-GaN can absorb ultraviolet light with a wavelength of less than 364.7nm, and the radiation recombination in the quantum well generates photons moving in all directions. Therefore, it can be judged that the P-GaN layer still has the problem of absorbing ultraviolet light in the deep ultraviolet LED flip-chip structure chip.

[0004] In addition, some researchers roughened or made holes on the surface of the P-GaN layer and the contact layer to improve the light extraction efficiency, but the results were minimal and it has not been commercially applied. Another group of researchers tried to reduce the thickness of P-GaN and reduce photon absorption. They adopted a flip-chip structure, with a 280nm deep ultraviolet TE mode light extraction efficiency of 4%-15% and a TE mode light extraction efficiency of 0.2%-1.1%. However, the above technical solution ignores a key problem: the P-GaN layer still exists on one side of the quantum well in a large area, and the photons generated by radiation recombination will still be absorbed, which fails to effectively solve the problem of large-area ultraviolet light absorption by the P-GaN layer. In addition, ignoring the thinning of the P-GaN thickness to 2 nm-3nm, since the current P-GaN epitaxial material generally has a roughness of 5 nm-10nm, there is a problem of discontinuity of the P-GaN film, which leads to a reduction in the effective light absorption area. Therefore, while ensuring that the quality of each layer of epitaxy remains unchanged, it is particularly important to reduce the P-GaN area and thus improve the light extraction efficiency. Summary of the invention

[0005] In view of the technical problem that the P-GaN layer still absorbs ultraviolet light in the above-mentioned deep ultraviolet LED flip-chip structure chip, the present invention provides a deep ultraviolet LED chip with a P-GaN material embedded structure and a preparation method thereof.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure comprises the following steps: S1, preparing a sapphire substrate, an AlN buffer layer, an N-AlGaN film, an MQW film and a P-AlGaN film in sequence from bottom to top, thereby preparing an epitaxial layer; S2, etching the epitaxial layer by ICP, from the P-AlGaN film to the AlN buffer layer, and performing degumming cleaning, H2SO4:H2O2 cleaning and organic cleaning in sequence after etching; S3, etching the P-AlGaN film by ICP, wherein the region where the P-AlGaN film is etched is region 1; S4, after etching the P-AlGaN film, the epitaxial layer is sequentially subjected to degumming cleaning, H2SO4:H2O2 cleaning and organic cleaning; S5, sputtering AlN film on the epitaxial layer using magnetron sputtering equipment; S6, etching the AlN film by ICP, and the area where the AlN film is etched is area 2; S7, after etching the AlN film, the epitaxial layer is sequentially subjected to degumming cleaning, H2SO4:H2O2 cleaning and organic cleaning; S8, depositing P-GaN thin film by MOCVD; S9, etching the P-GaN film outside the second region in S6 by ICP, and retaining the P-GaN film in the second region; S10, first prepare N gold on the surface of the N-AlGaN film, then prepare P gold on the surface of the P-GaN film in region 2, and finally prepare an independent deep ultraviolet LED chip through grinding, polishing and scratching.

[0007] The Al content of the P-AlGaN film is not higher than 65%, and the Mg doping concentration is E18cm -3 The thickness of the P-AlGaN film is 50 nm.

[0008] The S2 is etched from the P-AlGaN film to 1 / 3 of the thickness of the AlN buffer layer.

[0009] The area of ​​region 1 in S3 is less than 20% of the area of ​​the P-AlGaN film, and the depth of region 1 is 1 / 10 to 1 / 2 of the thickness of the P-AlGaN film.

[0010] The thickness of the sputtered AlN film in S5 is 10 nm to 50 nm.

[0011] The area of ​​the second region in S6 is smaller than the area of ​​the etched P-AlGaN film; the depth of the second region is greater than the thickness of the sputtered AlN film and less than 1 / 2 of the thickness of the P-AlGaN film.

[0012] The thickness of the P-GaN film deposited in S8 is 5nm~50nm.

[0013] A deep ultraviolet LED chip with a P-GaN material embedded structure comprises an epitaxial layer, an AlN film and a P-GaN film, wherein the epitaxial layer comprises a sapphire substrate, an AlN buffer layer, an N-AlGaN film, an MQW film and a P-AlGaN film, wherein the AlN buffer layer is grown on the sapphire substrate, the N-AlGaN film is grown on the AlN buffer layer, the MQW film is grown on the N-AlGaN film, and the P-AlGaN film is grown on the MQW film, the epitaxial layer is etched from the P-AlGaN film to the AlN buffer layer, a region one is etched on the P-AlGaN film, an AlN film is sputtered on the surface of the epitaxial layer, a region two is etched on the AlN film, and a P-GaN film is deposited in the region two.

[0014] N gold is prepared on the surface of the N-AlGaN film, and P gold is prepared on the surface of the P-GaN film in the second region.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention designs the P-AlGaN film and the P-GaN film stacking structure as an embedded structure, which not only ensures the ohmic contact characteristics of P-GaN and the metal electrode, but also reduces the light absorption area of ​​the P-GaN film. In addition, the present invention introduces AlN material with a hexagonal symmetric structure similar to the two film materials into the embedded structure of the P-GaN film and the P-AlGaN film, which effectively ensures the generation of defects at the interface of the three materials on the one hand, and on the other hand, the AlN material has excellent thermal conductivity, which can timely transfer the accumulated heat at the interface of the P-GaN film and the metal electrode to reduce thermal resistance. In addition, AlN is transparent to ultraviolet light and does not have the problem of light absorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0017] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0018] Figure 1 It is a schematic diagram of the structure of the epitaxial layer of the present invention; Figure 2 It is a schematic diagram of the structure of the epitaxial layer after photolithography of the present invention; Figure 3 It is a schematic diagram of the structure of the P-AlGaN film after etching of the present invention; Figure 4 It is a schematic diagram of the structure of the sputtered AlN film of the present invention; Figure 5 It is a schematic diagram of the structure of etching AlN film in the present invention; Figure 6 It is a schematic diagram of the structure of depositing P-GaN film in the present invention.

[0019] Among them: 1 is a sapphire substrate, 2 is an AlN buffer layer, 3 is an N-AlGaN film, 4 is an MQW film, 5 is a P-AlGaN film, 6 is an AlN film, 7 is a P-GaN film, 8 is region one, and 9 is region two. 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. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. These descriptions are only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0021] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0022] A deep ultraviolet LED chip with a P-GaN material embedded structure comprises an epitaxial layer, an AlN film 6 and a P-GaN film 7, wherein the epitaxial layer comprises a sapphire substrate 1, an AlN buffer layer 2, an N-AlGaN film 3, an MQW film 4 and a P-AlGaN film 5, wherein the AlN buffer layer 2 is grown on the sapphire substrate 1, the N-AlGaN film 3 is grown on the AlN buffer layer 2, the MQW film 4 is grown on the N-AlGaN film 3, and the P-AlGaN film 5 is grown on the MQW film 4, the epitaxial layer is etched from the P-AlGaN film 5 to the AlN buffer layer 2, a region 1 8 is etched on the P-AlGaN film 5, an AlN film 6 is sputtered on the surface of the epitaxial layer, a region 2 9 is etched on the AlN film 6, a P-GaN film 7 is deposited in the region 2 9, N-gold is prepared on the surface of the N-AlGaN film 3, and P-gold is prepared on the surface of the P-GaN film 7 in the region 2 9.

[0023] A method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure comprises the following steps: Step 1: Epitaxial layer growth: Figure 1 As shown, a 2-inch sapphire substrate 1 is used as a substrate, and an AlN buffer layer 2 is prepared by a magnetron sputtering process. An MOCVD device is used to sequentially deposit an N-AlGaN film 3, an MQW film 4, and a P-AlGaN film 5 on the surface of the AlN buffer layer 2. The Al component in the P-AlGaN film 5 is not higher than 65%, the Mg doping concentration is on the order of E18 cm-3, and the thickness of the P-AlGaN film 5 is 50 nm.

[0024] Step 2: ISO lithography, prepare 20×20mil chip, ICP etch the epitaxial layer, such as Figure 2 As shown, etching is performed to 1 / 3 of the thickness of the AlN buffer layer 2, and after etching, degumming cleaning, H2SO4:H2O2 cleaning, and organic cleaning are performed in sequence.

[0025] Step 3: Photolithography of the P-AlGaN film 5 and ICP etching of the P-AlGaN film 5. Figure 3 As shown, the region 8 is a square with a side length of 100 μm, accounting for 3.88% of the area of ​​the P-AlGaN film 5 , and the depth of the region 8 is 20 nm, accounting for 2 / 5 of the thickness of the P-AlGaN film 5 .

[0026] Step 4: After etching the P-AlGaN film 5, the epitaxial layer is sequentially subjected to resist removal cleaning, H2SO4:H2O2 cleaning and organic cleaning.

[0027] Step 5: Figure 4 As shown, a magnetron sputtering device is used to sputter an AlN film 6 on the epitaxial layer, and the thickness of the sputtered AlN film 6 is 20 nm.

[0028] Step 6: AlN film 6 photolithography, such as Figure 5 As shown, the ICP etches the AlN film 6, and the etching area is region 2 9, which is a concentric square with region 1 8. The side length of region 2 9 is 80 nm, and the etching depth is 25 nm.

[0029] Step 7: After etching the AlN film 6, the epitaxial layer is sequentially subjected to degumming cleaning, H2SO4:H2O2 cleaning and organic cleaning; Step 8: MOCVD deposits a P-GaN film 7 with a thickness of 25 nm; Step 9: Photolithography of P-GaN film 7, such as Figure 6 As shown, the P-GaN film 7 is etched by ICP with an etching depth of 27 nm, the P-GaN film 7 outside the region 2 9 in step 6 is removed, and the P-GaN film 7 in the region 2 9 is retained.

[0030] Step 10: Prepare N-gold on the surface of the N-AlGaN film 3 and P-gold on the surface of the P-GaN in the second region 9, and prepare independent deep ultraviolet LED chips by grinding, polishing and scratching.

[0031] First, step 1 is performed to prepare an epitaxial layer, and 1 / 2 of the epitaxial layer of the comparative example is taken to perform step 8. In this embodiment, the remaining 1 / 2 of the material in the comparative example is taken to perform steps 2 to 9 to prepare an epitaxial material. Step 10 is performed under the same conditions as the materials obtained in the comparative example and the present embodiment. The IV curves, VF3, PO1 and WPE results of the comparative example and the present embodiment are shown in Table 1.

[0032] Table 1 Chip test results of this embodiment and comparative example Chip test project Comparative Example This embodiment IV Curve Linear Linear VF3 5.4V 5.1V PO1 25mw 35mw WPE 4.63% 6.86% As can be seen from Table 1, the IV curve of this embodiment remains linear, which indicates that when the voltage changes, the change in current is uniform, thereby ensuring the stability and reliability of the device at different operating points. Compared with the comparative example, the VF3 voltage of this embodiment is reduced from 5.4V to 5.1V, which means that under the same conditions, the energy consumption of this embodiment is lower. The PO1 power is increased from 25mw to 35mw, which indicates that this embodiment can provide higher power output at the same voltage. WPE is increased from 4.63% to 6.86%, which indicates that the electro-optical conversion efficiency of this embodiment is higher. This embodiment organically integrates MOCVD technology with chip lithography technology to fully realize structural optimization and achieve ultraviolet LED chip performance output.

[0033] Only the preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention, and various changes should be included in the protection scope of the present invention.

Claims

1. A method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure, characterized in that: The following steps are involved: S1, preparing a sapphire substrate (1), an AlN buffer layer (2), an N-AlGaN film (3), an MQW film (4), and a P-AlGaN film (5) in sequence from bottom to top, thereby preparing an epitaxial layer; S2, etching the epitaxial layer by ICP, from the P-AlGaN film (5) to the AlN buffer layer (2), and performing degumming cleaning, H2SO4:H2O2 cleaning and organic cleaning in sequence after etching; S3, etching the P-AlGaN film (5) by ICP, wherein the area of ​​the P-AlGaN film (5) etched is area 1 (8); S4, after etching the P-AlGaN film (5), the epitaxial layer is sequentially subjected to degumming cleaning, H2SO4:H2O2 cleaning and organic cleaning; S5, sputtering an AlN film (6) on the epitaxial layer using a magnetron sputtering device; S6, etching the AlN film (6) by ICP, wherein the area of ​​the AlN film (6) etched is area 2 (9); S7, after etching the AlN film (6), the epitaxial layer is sequentially subjected to degumming cleaning, H2SO4:H2O2 cleaning and organic cleaning; S8, depositing a P-GaN thin film (7) by MOCVD; S9, etching the P-GaN film (7) outside the second region (9) in S6 by ICP, and retaining the P-GaN film (7) in the second region (9); S10, first prepare N gold on the surface of the N-AlGaN film (3), then prepare P gold on the surface of the P-GaN film (7) in the second region (9), and finally prepare an independent deep ultraviolet LED chip through grinding, polishing and scratching.

2. The method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure according to claim 1, characterized in that: The Al content of the P-AlGaN film (5) is not higher than 65%, and the Mg doping concentration is E18cm -3 The thickness of the P-AlGaN film (5) is 50 nm.

3. The method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure according to claim 1, characterized in that: The P-AlGaN film (5) in S2 is etched to 1 / 3 of the thickness of the AlN buffer layer (2).

4. The method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure according to claim 1, characterized in that: The area of ​​region one (8) in S3 is less than 20% of the area of ​​the P-AlGaN film (5), and the depth of region one (8) is 1 / 10 to 1 / 2 of the thickness of the P-AlGaN film (5).

5. The method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure according to claim 1, characterized in that: The thickness of the sputtered AlN film (6) in S5 is 10 nm to 50 nm.

6. The method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure according to claim 1, characterized in that: The area of ​​the second region (9) in S6 is smaller than the area of ​​the etched P-AlGaN film (5); the depth of the second region (9) is greater than the thickness of the sputtered AlN film (6) and less than 1 / 2 of the thickness of the P-AlGaN film (5).

7. The method for preparing a deep ultraviolet LED chip with a P-GaN material embedded structure according to claim 1, characterized in that: The thickness of the P-GaN film (7) deposited in S8 is 5 nm to 50 nm.

8. A deep ultraviolet LED chip with a P-GaN material embedded structure, characterized in that: The invention comprises an epitaxial layer, an AlN film (6) and a P-GaN film (7), wherein the epitaxial layer comprises a sapphire substrate (1), an AlN buffer layer (2), an N-AlGaN film (3), an MQW film (4) and a P-AlGaN film (5), wherein the AlN buffer layer (2) is grown on the sapphire substrate (1), the N-AlGaN film (3) is grown on the AlN buffer layer (2), the MQW film (4) is grown on the N-AlGaN film (3), and the P-AlGaN film (5) is grown on the MQW film (4); the epitaxial layer is etched from the P-AlGaN film (5) to the AlN buffer layer (2), a region one (8) is etched on the P-AlGaN film (5), an AlN film (6) is sputtered on the surface of the epitaxial layer, a region two (9) is etched on the AlN film (6), and a P-GaN film (7) is deposited in the region two (9).

9. The deep ultraviolet LED chip with a P-GaN material embedded structure according to claim 8, characterized in that: The surface of the N-AlGaN film (3) is prepared with N gold, and the surface of the P-GaN film (7) in the second region (9) is prepared with P gold.

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