Deep ultraviolet LED device with inverted structure and preparation method of deep ultraviolet LED device

Abstract

The invention belongs to the technical field of deep ultraviolet LED devices, and particularly relates to a deep ultraviolet LED device with an inverted structure and a preparation method thereof, and the preparation method comprises the steps: 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 an MESA table board; preparing an n contact electrode and a p contact electrode, and preparing passivation layers on the surfaces of the n contact electrode, the p contact electrode and the LED epitaxial structure; preparing a through hole in the passivation layer above the n contact electrode and the p contact electrode, and preparing a pad electrode on the through hole; and thinning the sapphire substrate by using a chemical mechanical polishing process. According to the invention, multiple layers of dielectric materials with different refractive indexes are deposited on the AlN template to form a deep ultraviolet anti-reflection optical film, so that the efficiency of direct emission of photons generated by a quantum well is improved, and the luminous efficiency of the AlN template with an epitaxial structure is improved. The method provided by the invention not only can improve the light extraction efficiency, but also can reduce the light loss, thereby improving the performance of the device.

Description

Technical Field

[0001] The 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] As an emerging semiconductor optoelectronic device, deep ultraviolet LED chips have a wide range of applications, covering many important fields such as sterilization, biomedicine, and communications. Among them, the light output efficiency of deep ultraviolet LED chips is one of its key performance indicators. The importance of this is self-evident because it is directly related to the effect of the chip in practical applications and its competitiveness in the market. However, deep ultraviolet LED chips have certain limitations in material properties and structural design, which makes their light output efficiency often low. This problem, to a certain extent, limits the application scope of deep ultraviolet LED chips and their development potential.

[0003] The existing technology mainly improves the output efficiency of photons by improving the structural design of quantum wells and the manufacturing process of chips. For example, by changing the parameters such as the shape, size and material composition of quantum wells, its energy band structure can be adjusted to improve the efficiency of photon generation. At the same time, by optimizing the structural design of chips, such as adding anti-reflective coatings and improving heat dissipation conditions, the stability and reliability of devices can be improved.

[0004] However, existing technologies still have some problems 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, although the existing manufacturing process can improve the stability and reliability of the chip, in actual applications, the performance of the device is still affected by environmental factors such as temperature and humidity. Finally, the existing manufacturing process is complex and costly, which is not conducive to large-scale production and application. Summary of the invention

[0005] In view of the technical problem that the above-mentioned prior art limits the quantum well luminescence 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: A method for preparing a deep ultraviolet LED device with an inverted structure comprises the following steps: S1, preparing an AlN template layer on a sapphire substrate by magnetron sputtering; S2, preparing HfO2-MgF2 periodic structure layer; S3, immersing the sapphire substrate with the HfO2-MgF2 periodic structure layer prepared in S2 in an ACE solution for cleaning for 5 minutes, then immersing it in an IPA solution, and then flushing and drying; S4, performing secondary epitaxial growth of a GaN buffer layer on the HfO2-MgF2 periodic structure layer; S5, continuing to grow the LED epitaxial structure on the GaN buffer layer, and cleaning the surface of the LED epitaxial structure; S6. Prepare a MESA table; 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; 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; S9. Thinning the sapphire substrate using a chemical mechanical polishing process.

[0007] 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, a total of 4-8 cycles, to form a deep ultraviolet anti-reflection optical film.

[0008] 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-0.4nm / S.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] A deep ultraviolet LED device with an inverted structure, comprising a sapphire substrate, an AlN template layer, a 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, wherein 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, 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, 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.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention deposits multiple layers of dielectric materials with different refractive indices on the AlN template to form a deep ultraviolet anti-reflection optical film, 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 the light loss, thereby improving the performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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.

[0018] 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.

[0019] Figure 1 It is a schematic diagram of the structure of the present invention.

[0020] 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

[0021] 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.

[0022] 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.

[0023] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0024] A method for preparing a deep ultraviolet LED device with an inverted structure comprises the following steps: Step 1: Prepare an AlN template layer 102 on a sapphire substrate 101 by magnetron sputtering.

[0025] Step 2: Prepare the HfO2-MgF2 periodic structure layer 103 on the AlN template layer 102 by ion beam evaporation or magnetron sputtering, deposit multiple layers of HfO2 material and MgF2 material on the AlN template, first deposit the HfO2 material and then deposit the MgF2 material, and finally terminate 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, so as to improve 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 the light loss, thereby improving the performance of the device. The preparation process of MgF2 material is: the chamber vacuum is below 1 E-2Pa, the temperature range is 20℃-25℃, and the plating rate range is 0.2 nm / S -0.3nm / S. The preparation process of HfO2 material is: the chamber vacuum is below 1 E-2Pa, the temperature range is 20℃-25℃, and the plating rate range is 0.3 nm / S -0.4nm / S.

[0026] 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.

[0027] Step 3: Immerse the sapphire substrate 101 prepared 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.

[0028] Step 4: Perform secondary epitaxial growth of a GaN buffer layer 104 on the HfO 2 —MgF 2 periodic structure layer 103 .

[0029] Step 5: Continue to grow the LED epitaxial structure on the GaN buffer layer 104, sequentially grow 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.

[0030] 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 table.

[0031] Step 7: The p-contact electrode 202 is grown on the pGaN layer 108 , the n-contact electrode 201 is grown on the MESA table, and 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.

[0032] 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 the group consisting of 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.

[0033] 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.

[0034] 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 metals for subsequent packaging eutectic use.

[0035] Step 9: Use chemical mechanical polishing to thin the sapphire substrate 101. The chemical mechanical polishing process uses grinding, polishing or etching. The thinning range of the sapphire substrate 101 is 10 um-100 um. Thin the sapphire substrate to a certain thickness or remove it to reduce the absorption of photons by the sapphire substrate 101 and improve its transmission effect. This method can not only improve the utilization rate of light, but also improve the heat dissipation capacity of the deep ultraviolet LED chip and reduce the weight and cost of the device.

[0036] 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, 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, the pGaN layer 108 is prepared on the pAlGaN layer 107, and one side of the pGaN layer 108 is etched to the nAlGaN layer 105 to form a MESA table. The n-contact electrode 201 is prepared on the MESA table, the p-contact electrode 202 is prepared on the pGaN layer 108, and the passivation layer 301 is prepared on the n-contact electrode 201 and the p-contact electrode 202. Through holes are prepared on the passivation layer 301 above the n-contact electrode 201 and the p-contact electrode 202, and the pad electrode 203 passes through the through holes to connect with the n-contact electrode 201 and the p-contact electrode 202.

[0037] 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 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 a MESA table; 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: using ion beam evaporation or magnetron sputtering to prepare the HfO2-MgF2 periodic structure layer (103) on the AlN template layer (102), 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, 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, characterized in that: 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-0.4nm / S.

4. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 2, characterized in that: 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.

5. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 1, characterized in that: 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: on one side of the LED epitaxial structure, etching the LED epitaxial structure to the nAlGaN layer (105) to form the MESA mesa.

7. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 5, characterized in that: 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 the group consisting of Cr, Ni, Al, Ag, Au, Ti, Sn, Rh and Pt. The n-contact electrode (201) and the p-contact electrode (202) are grown by electron beam evaporation, thermal resistance evaporation or sputtering evaporation.

8. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 1, characterized in that: 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.

9. The method for preparing a flip-chip structure deep ultraviolet LED device according to claim 1, characterized in that: The chemical mechanical grinding process in S9 adopts grinding, polishing or etching, and the thinning range of the sapphire substrate (101) is 10um-100um.

10. A deep ultraviolet LED device with an inverted 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 (106) is grown on the pAlGaN layer (107). The MQW layer (106) is grown on the nAlGaN layer (105), the pAlGaN layer (107) is grown on the MQW layer (106), the pGaN layer (108) is grown on the pAlGaN layer (107), one side of the pGaN layer (108) is etched to the nAlGaN layer (105) 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), 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.

Images