A deep ultraviolet LED device with an inverted structure and a method for preparing the same

Abstract

The present invention belongs to the technical field of deep ultraviolet LED devices, and specifically relates to a flip-chip deep ultraviolet LED device and a preparation method thereof, the preparation method comprising: preparing an AlN template layer; preparing an HfO2-MgF2 periodic structure layer; growing a GaN buffer layer; growing an LED epitaxial structure, and cleaning the surface of the LED epitaxial structure; preparing a MESA table; preparing an n-contact electrode and a p-contact electrode, and preparing a passivation layer on the n-contact electrode, the p-contact electrode, and the surface of the LED epitaxial structure; preparing a through hole on the passivation layer above the n-contact electrode and the p-contact electrode, and preparing a pad electrode on the through hole; and thinning a sapphire substrate using a chemical mechanical polishing process. The present invention forms a deep ultraviolet anti-reflection optical film by depositing multiple layers of dielectric materials with different refractive indices on the AlN template, thereby improving the efficiency of direct emission of photons generated by the quantum well, thereby improving the luminous efficiency of the epitaxial structure AlN template. The method of the present invention can not only improve the light extraction efficiency, but also reduce light loss, thereby improving the performance of the device.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep ultraviolet LED devices, and in particular relates to a deep ultraviolet LED device with an inverted structure and a preparation method thereof. Background Art

[0002] Deep UV LED chips, as an emerging semiconductor optoelectronic device, have a wide range of applications, covering a number of important fields, including sterilization and disinfection, biomedicine, and communications. The light extraction efficiency of deep UV LED chips is one of their key performance indicators, and its importance is self-evident, as it directly affects the chip's effectiveness in practical applications and its competitiveness in the market. However, deep UV LED chips have certain limitations in material properties and structural design, which often result in low light extraction efficiency. This problem has, to a certain extent, limited the application scope and development potential of deep UV LED chips.

[0003] Existing technologies primarily improve photon output efficiency by refining the quantum well structure and chip manufacturing processes. For example, by varying parameters such as the quantum well's shape, size, and material composition, its band structure can be tuned, thereby increasing photon generation efficiency. Furthermore, optimizing the chip's structural design, such as by adding anti-reflective coatings and improving heat dissipation, can enhance device stability and reliability.

[0004] However, existing technologies still face challenges in improving photon output efficiency and optimizing chip structure design. First, due to the propagation characteristics of light in various media, only a portion of photons can be directly emitted, which limits the luminous efficiency of quantum wells. Second, while existing manufacturing processes can improve chip stability and reliability, in practice, device performance is still affected by environmental factors such as temperature and humidity. Finally, existing manufacturing processes are complex and costly, making them unsuitable for large-scale production and application. Summary of the Invention

[0005] In response to the technical problem that the above-mentioned existing technology limits the quantum well luminous efficiency, the present invention provides a flip-chip structure deep ultraviolet LED device and a preparation method thereof. By introducing a deep ultraviolet anti-reflection optical film, the efficiency of direct emission of photons generated by the quantum well is improved, and the heat dissipation capacity of the deep ultraviolet LED chip is optimized.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for preparing a flip-chip deep ultraviolet LED device comprises the following steps:

[0008] S1, preparing an AlN template layer on a sapphire substrate by magnetron sputtering;

[0009] S2, preparing HfO2-MgF2 periodic structure layer;

[0010] S3, immersing the sapphire substrate with the HfO2-MgF2 periodic structure layer prepared in S2 in ACE solution for cleaning for 5 minutes, then immersing it in IPA solution, and then rinsing and drying;

[0011] S4, performing secondary epitaxial growth of a GaN buffer layer on the HfO2-MgF2 periodic structure layer;

[0012] S5. Continue growing the LED epitaxial structure on the GaN buffer layer, and clean the surface of the LED epitaxial structure;

[0013] S6. Prepare MESA countertop;

[0014] S7, preparing an n-contact electrode and a p-contact electrode, and preparing a passivation layer on the surface of the n-contact electrode, the p-contact electrode and the LED epitaxial structure;

[0015] S8, preparing a through hole on the passivation layer above the n-contact electrode and the p-contact electrode, and preparing a pad electrode on the through hole;

[0016] S9. Thinning the sapphire substrate using a chemical mechanical polishing process.

[0017] The method for preparing the HfO2-MgF2 periodic structure layer in S2 is: using ion beam evaporation or magnetron sputtering to prepare the HfO2-MgF2 periodic structure layer on the AlN template layer, depositing multiple layers of HfO2 material and MgF2 material on the AlN template, first depositing the HfO2 material and then depositing the MgF2 material, and finally terminating with the HfO2 material, for a total of 4-8 cycles, to form a deep ultraviolet anti-reflection optical film.

[0018] The preparation process of the MgF2 material is as follows: the chamber vacuum is below 1 E-2Pa, the temperature range is 20°C-25°C, and the plating rate range is 0.2 nm / S-0.3nm / S;

[0019] The preparation process of the HfO2 material is as follows: the chamber vacuum is below 1 E-2Pa, the temperature range is 20°C-25°C, and the plating rate range is 0.3 nm / S-0.4 nm / S.

[0020] The HfO2 material and the MgF2 material are cyclically prepared in the same chamber, the MgF2 target material uses 1mm-6mm crystal particles with a purity of 4N or above, and the HfO2 target material uses 1mm-4mm particles with a purity of 4N or above.

[0021] The method for growing the LED epitaxial structure in S5 is: sequentially growing an nAlGaN layer, an MQW layer, a pAlGaN layer, and a pGaN layer on the GaN buffer layer.

[0022] The method for preparing the MESA mesa in S6 is: on one side of the LED epitaxial structure, etching the LED epitaxial structure to the nAlGaN layer to form the MESA mesa.

[0023] The p-contact electrode is grown on the pGaN layer, and the n-contact electrode is grown on the MESA table. Both the n-contact electrode and the p-contact electrode are made of one or a combination of several metals selected from Cr, Ni, Al, Ag, Au, Ti, Sn, Rh and Pt materials. Both the n-contact electrode and the p-contact electrode are grown by electron beam evaporation, thermal resistance evaporation or sputtering evaporation.

[0024] The pad electrode is formed by stacking multiple metals such as Cr, Ni, Ti, Pt, Au, and Sn, and the top layer is made of Au and Sn metal for subsequent packaging eutectic use.

[0025] The chemical mechanical polishing process in S9 adopts grinding, polishing or etching, and the thinning range of the sapphire substrate is 10 um-100 um.

[0026] A flip-chip deep ultraviolet LED device includes a sapphire substrate, an AlN template layer, an HfO2-MgF2 periodic structure layer, a GaN buffer layer, an nAlGaN layer, an MQW layer, a pAlGaN layer, a pGaN layer, an n-contact electrode, a p-contact electrode, a pad electrode, and a passivation layer. The AlN template layer is grown on the sapphire substrate, the HfO2-MgF2 periodic structure layer is grown on the AlN template layer, the GaN buffer layer is grown on the HfO2-MgF2 periodic structure layer, and the nAlGaN layer is grown on the GaN buffer layer. The MQW layer is grown on the nAlGaN layer, the pAlGaN layer is grown on the MQW layer, the pGaN layer is grown on the pAlGaN layer, and one side of the pGaN layer is etched to the nAlGaN layer to form a MESA table. The n-contact electrode is grown on the MESA table, the p-contact electrode is grown on the pGaN layer, and the passivation layer is grown on the n-contact electrode and the p-contact electrode. A through hole is prepared on the passivation layer above the n-contact electrode and the p-contact electrode, and the pad electrode is connected to the n-contact electrode and the p-contact electrode through the through hole.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This method deposits multiple layers of dielectric materials with different refractive indices onto an AlN template to form a deep ultraviolet (UV) anti-reflection optical film. This increases the efficiency of direct emission of photons generated by the quantum well, thereby improving the luminous efficiency of the epitaxial AlN template. This method not only improves light extraction efficiency but also reduces light loss, thereby enhancing device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0030] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and to facilitate understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, without affecting the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0031] Figure 1 It is a structural schematic diagram of the present invention.

[0032] Wherein: 101 is a sapphire substrate, 102 is an AlN template layer, 103 is a HfO2-MgF2 periodic structure layer, 104 is a GaN buffer layer, 105 is an nAlGaN layer, 106 is an MQW layer, 107 is a pAlGaN layer, 108 is a pGaN layer, 201 is an n-contact electrode, 202 is a p-contact electrode, 203 is a pad electrode, and 301 is a passivation layer. DETAILED DESCRIPTION

[0033] 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 this application, not 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 this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0034] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0035] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0036] A method for preparing a flip-chip deep ultraviolet LED device comprises the following steps:

[0037] Step 1: Prepare an AlN template layer 102 on a sapphire substrate 101 by magnetron sputtering.

[0038] Step 2: Use ion beam evaporation or magnetron sputtering to prepare the HfO2-MgF2 periodic structure layer 103 on the AlN template layer 102. Deposit multiple layers of HfO2 material and MgF2 material on the AlN template, first depositing the HfO2 material and then the MgF2 material, and finally terminating with the HfO2 material, for a total of 4-8 cycles to form a deep ultraviolet anti-reflection optical film. By depositing multiple layers of dielectric materials with different refractive indices on the AlN template layer 102 to form a deep ultraviolet anti-reflection optical film, the efficiency of direct emission of photons generated by the quantum well is improved, thereby improving the external quantum efficiency of the epitaxial structure AlN template layer 102. This method can not only improve the light extraction efficiency, but also reduce light loss, thereby improving the performance of the device.

[0039] The MgF2 material preparation process is as follows: chamber vacuum below 1 E-2Pa, temperature range of 20°C-25°C, and plating rate range of 0.2 nm / s-0.3 nm / s. The HfO2 material preparation process is as follows: chamber vacuum below 1 E-2Pa, temperature range of 20°C-25°C, and plating rate range of 0.3 nm / s-0.4 nm / s.

[0040] HfO2 material and MgF2 material are cyclically prepared in the same chamber. The MgF2 target material uses 1mm-6mm crystal particles with a purity of 4N or above, and the HfO2 target material uses 1mm-4mm particles with a purity of 4N or above.

[0041] Step 3: Immerse the sapphire substrate 101 with the HfO2-MgF2 periodic structure layer 103 in an ACE solution for cleaning for 5 minutes, then immerse it in an IPA solution, and then rinse and dry it.

[0042] Step 4: Perform secondary epitaxial growth of a GaN buffer layer 104 on the HfO 2 —MgF 2 periodic structure layer 103 .

[0043] Step 5: Continue growing the LED epitaxial structure on the GaN buffer layer 104 , sequentially growing the nAlGaN layer 105 , the MQW layer 106 , the pAlGaN layer 107 and the pGaN layer 108 , and clean the surface of the LED epitaxial structure.

[0044] Step 6: On one side of the LED epitaxial structure, the LED epitaxial structure is etched to the nAlGaN layer 105 to form a MESA mesa.

[0045] Step 7: The p-contact electrode 202 is grown on the pGaN layer 108 , and the n-contact electrode 201 is grown on the MESA table. A passivation layer 301 is prepared on the surface of the n-contact electrode 201 , the p-contact electrode 202 and the LED epitaxial structure.

[0046] Furthermore, preferably, the n-contact electrode 201 and the p-contact electrode 202 are both made of one or a combination of several metals selected from Cr, Ni, Al, Ag, Au, Ti, Sn, Rh and Pt materials, and the n-contact electrode 201 and the p-contact electrode 202 are both grown by electron beam evaporation, thermal resistance evaporation or sputtering evaporation.

[0047] Step eight: prepare a through hole on the passivation layer 301 above the n-contact electrode 201 and the p-contact electrode 202 , and prepare a pad electrode 203 on the through hole.

[0048] Furthermore, preferably, the pad electrode 203 is formed by stacking multiple metals such as Cr, Ni, Ti, Pt, Au, and Sn, and the top layer is made of Au and Sn metal for subsequent packaging eutectic use.

[0049] Step 9: Thin the sapphire substrate 101 using a chemical mechanical polishing process. The chemical mechanical polishing process involves grinding, polishing, or etching. The sapphire substrate 101 is thinned to a thickness of 10 to 100 μm. Thinning the sapphire substrate to a certain thickness or removing it reduces its absorption of photons and improves its transmission. This method not only improves light utilization but also enhances the heat dissipation capacity of the deep ultraviolet LED chip, reducing the weight and cost of the device.

[0050] A deep ultraviolet LED device with an inverted structure, such as Figure 1As shown, it includes a sapphire substrate 101, an AlN template layer 102, a HfO2-MgF2 periodic structure layer 103, a GaN buffer layer 104, a nAlGaN layer 105, an MQW layer 106, a pAlGaN layer 107, a pGaN layer 108, an n-contact electrode 201, a p-contact electrode 202, a pad electrode 203 and a passivation layer 301, wherein the AlN template layer 102 is prepared on the sapphire substrate 101, the HfO2-MgF2 periodic structure layer 103 is prepared on the AlN template layer 102, the GaN buffer layer 104 is prepared on the HfO2-MgF2 periodic structure layer 103, the nAlGaN layer 105 is prepared on the GaN buffer layer 104, and the M The QW layer 106 is prepared on the nAlGaN layer 105, the pAlGaN layer 107 is prepared on the MQW layer 106, and the pGaN layer 108 is prepared on the pAlGaN layer 107. One side of the pGaN layer 108 is etched to the nAlGaN layer 105 to form a MESA mesa. The n-contact electrode 201 is prepared on the MESA mesa, and the p-contact electrode 202 is prepared on the pGaN layer 108. The passivation layer 301 is prepared on the n-contact electrode 201 and the p-contact electrode 202. A through hole is prepared on the passivation layer 301 above the n-contact electrode 201 and the p-contact electrode 202, and the pad electrode 203 is connected to the n-contact electrode 201 and the p-contact electrode 202 through the through hole.

[0051] The above only describes in detail the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention, and various changes should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a flip-chip structure deep ultraviolet LED device, characterized in that: The following steps are involved: S1, preparing an AlN template layer (102) on a sapphire substrate (101) by magnetron sputtering; S2, preparing a HfO2-MgF2 periodic structure layer (103); S3, immersing the sapphire substrate (101) having the HfO2-MgF2 periodic structure layer (103) prepared in S2 in an ACE solution for cleaning for 5 minutes, then immersing it in an IPA solution, and then rinsing and drying; S4, performing secondary epitaxial growth of a GaN buffer layer (104) on the HfO2-MgF2 periodic structure layer (103); S5, continuing to grow the LED epitaxial structure on the GaN buffer layer (104), and cleaning the surface of the LED epitaxial structure; S6. Prepare MESA countertop; S7, preparing an n-contact electrode (201) and a p-contact electrode (202), and preparing a passivation layer (301) on the surface of the n-contact electrode (201), the p-contact electrode (202), and the LED epitaxial structure; S8, preparing a through hole on the passivation layer (301) above the n-contact electrode (201) and the p-contact electrode (202), and preparing a pad electrode (203) on the through hole; S9. Thinning the sapphire substrate (101) using a chemical mechanical polishing process.

2. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 1, characterized in that: The method for preparing the HfO2-MgF2 periodic structure layer (103) in S2 is as follows: ion beam evaporation or magnetron sputtering is used to prepare the HfO2-MgF2 periodic structure layer (103) on the AlN template layer (102), and multiple layers of HfO2 material and MgF2 material are deposited on the AlN template, first depositing the HfO2 material and then depositing the MgF2 material, and finally terminating with the HfO2 material, for a total of 4-8 cycles, to form a deep ultraviolet anti-reflection optical film.

3. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 2, wherein: The preparation process of the MgF2 material is as follows: the chamber vacuum is below 1 E-2Pa, the temperature range is 20°C-25°C, and the plating rate range is 0.2 nm / S-0.3nm / S; The preparation process of the HfO2 material is as follows: the chamber vacuum is below 1 E-2Pa, the temperature range is 20°C-25°C, and the plating rate range is 0.3 nm / S-0.4 nm / S.

4. The method for preparing a flip-chip deep ultraviolet LED device according to claim 2, wherein: The HfO2 material and MgF2 material are cyclically prepared in the same chamber. The MgF2 target material uses crystal particles with a purity of 4N or above, and the particle size range is 1mm-6mm; the HfO2 target material uses particles with a purity of 4N or above, and the particle size range is 1mm-4mm.

5. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 1, wherein: The method for growing the LED epitaxial structure in S5 is: sequentially growing an nAlGaN layer (105), an MQW layer (106), a pAlGaN layer (107), and a pGaN layer (108) on a GaN buffer layer (104).

6. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 5, characterized in that: The method for preparing the MESA mesa in S6 is: etching the LED epitaxial structure to the nAlGaN layer (105) on one side of the LED epitaxial structure to form the MESA mesa.

7. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 5, wherein: The p-contact electrode (202) is grown on the pGaN layer (108), and the n-contact electrode (201) is grown on the MESA table. The n-contact electrode (201) and the p-contact electrode (202) are both made of one or a combination of several metals selected from Cr, Ni, Al, Ag, Au, Ti, Sn, Rh and Pt materials. The n-contact electrode (201) and the p-contact electrode (202) are both grown by electron beam evaporation, thermal resistance evaporation or sputtering evaporation.

8. The method for preparing a flip-chip deep ultraviolet LED device according to claim 1, wherein: The pad electrode (203) is formed by stacking multiple metals such as Cr, Ni, Ti, Pt, Au, and Sn, with the top layer made of Au and Sn metals for subsequent packaging eutectic use.

9. The method for preparing a flip-chip deep ultraviolet LED device according to claim 1, wherein: The thinning range of the sapphire substrate (101) in S9 is 10 um-100 um.

10. A deep ultraviolet LED device with a flip-chip structure, characterized in that: The invention comprises a sapphire substrate (101), an AlN template layer (102), a HfO2-MgF2 periodic structure layer (103), a GaN buffer layer (104), an nAlGaN layer (105), an MQW layer (106), a pAlGaN layer (107), a pGaN layer (108), an n-contact electrode (201), a p-contact electrode (202), a pad electrode (203) and a passivation layer (301), wherein the AlN template layer (102) is grown on the sapphire substrate (101), the HfO2-MgF2 periodic structure layer (103) is grown on the AlN template layer (102), the GaN buffer layer (104) is grown on the HfO2-MgF2 periodic structure layer (103), the nAlGaN layer (105) is grown on the GaN buffer layer (104), and the MQW layer ( The invention relates to a method for manufacturing a MQW layer (106) and a pAlGaN layer (107) grown on the nAlGaN layer (105), wherein the pAlGaN layer (108) is grown on the pAlGaN layer (107), and the pGaN layer (108) is etched to the nAlGaN layer (105) on one side of the pGaN layer (108) to form a MESA table. The n-contact electrode (201) is grown on the MESA table. The p-contact electrode (202) is grown on the pGaN layer (108), and the passivation layer (301) is grown on the n-contact electrode (201) and the p-contact electrode (202). A through hole is prepared on the passivation layer (301) above the n-contact electrode (201) and the p-contact electrode (202), and the pad electrode (203) is connected to the n-contact electrode (201) and the p-contact electrode (202) through the through hole.

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