Preparation method of N electrode of quaternary reversed-polarity red light tube core

Abstract

The invention provides a preparation method of a quaternary reversed polarity red light tube core N electrode, and relates to the technical field of photoelectrons. According to the method, a substrate and a barrier layer of a bonded quaternary reversed-polarity red light LED epitaxial wafer are all corroded and removed, and then a thin NiGeAu film is evaporated on the surface to serve as an N-type ohmic contact electrode. The method comprises the following steps: firstly, preparing a thin NiGeAu film and a thin GaAs layer, then fully fusing the thin NiGeAu film and the thin GaAs layer through high-temperature annealing and permeating the thin NiGeAu film and the thin GaAs layer to an N-type AlGaInP layer by utilizing the characteristics of the NiGeAu film, then corroding the thin NiGeAu film and the thin GaAs layer through normal-temperature Au corrosive liquid, coating negative photoresist to form an N electrode pattern under the condition that the positive photoresist is not removed, then sequentially evaporating a thick NiGeAu film and a thick Au film, and removing the redundant Au film outside an N-surface electrode through a blue film. The four-element reversed polarity red light tube core N electrode is obtained, the problem that the four-element reversed polarity red light tube core N electrode is unstable in pattern is avoided, and the quality of a chip is improved.

Description

Technical Field

[0001] The invention relates to the field of optoelectronic technology, in particular to a method for preparing a quaternary reverse polarity red light tube core N electrode. Background Art

[0002] The development of quaternary red LED chips can be traced back to 1962, when Nick Holonyak of General Electric successfully developed the first red diode. This innovative achievement earned Holonyak the title of "Father of LED" and was permanently recorded in the history of science and technology. Red diodes were initially used in indicator lights, display screens, and signal lights, and then gradually evolved into the earliest branch of LED technology to be applied.

[0003] At present, the flip-chip AlGaInP quaternary red LED chip has been widely used in the field of high-power outdoor LED display screens. The so-called flip-chip refers to the replacement of the substrate on the basis of the traditional quaternary red LED chip, replacing the GaAs substrate with a higher absorption rate with a single crystal conductive Si substrate or a sapphire substrate. After the substrate replacement is completed, the GaAs substrate is etched away, and the corrosion barrier layer is etched away to expose the heavily doped layer. Subsequently, an Au film is evaporated on the heavily doped layer to form an ohmic contact, and then the N-side ohmic contact layer pattern is prepared by photolithography technology, and the N electrode is prepared. At present, the chemical etching method is mainly used to prepare the ohmic contact pattern, but the electrode prepared by this method has poor stability. In view of the high brightness of the quaternary reverse polarity red light tube core, the stability requirements of the N-side ohmic contact pattern are more stringent. Therefore, how to reduce this part of the impact and ensure the stability of the quaternary reverse polarity red light tube core has become the main topic of current research. Summary of the invention

[0004] In response to the above problems, the present application provides a method for preparing a quaternary reverse polarity red light tube core N electrode, which has a simple manufacturing process and can effectively improve the light output efficiency and the stability of the electrode.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] A method for preparing a quaternary reverse polarity red light tube core N electrode comprises the following steps:

[0007] S1, sequentially preparing a P-type ohmic contact layer and a current blocking layer on the P-type AlGaInP layer of the reverse polarity AlGaInP quaternary LED epitaxial wafer, and then bonding them to a new substrate layer to obtain a flip-chip AlGaInP quaternary red LED epitaxial wafer;

[0008] S2, etching away the GaAs substrate and the barrier layer GaInP of the inverted AlGaInP quaternary red LED epitaxial wafer obtained in step S1, thereby exposing the heavily doped GaAs layer;

[0009] S3, evaporating a thin NiAuGeAu film on the exposed thin GaAs layer;

[0010] S4, high temperature annealing, so that the thin NiAuGeAu film is fully integrated with the heavily doped GaAs layer and penetrates into the N-type AlGaInP layer;

[0011] S5, coating a photoresist on the surface of the thin NiAuGeAu film, and performing a photolithography to obtain a photolithography pattern;

[0012] S6, etching away the thin NiAuGeAu film in the etching area of ​​the primary lithography pattern, the heavily doped GaAs layer and the NiAuGeAu that penetrates into the N-type AlGaInP layer, and forming a rough surface on the N-type AlGaInP layer;

[0013] S7, coating the rough surface with photoresist for a second time and performing secondary photolithography;

[0014] S8, sequentially evaporating a thick NiAuGeAu film and a thick Au film, and removing excess thick NiAuGeAu film and thick Au film.

[0015] Furthermore, the new substrate layer is a single crystal conductive Si substrate or a sapphire substrate.

[0016] Furthermore, the thickness of the thin NiAuGeAu film is 0.0005-0.0010 μm.

[0017] Furthermore, the temperature of the high temperature annealing in step S4 is 520-550° C., and the annealing time is 10-15 minutes.

[0018] Furthermore, in step S6, Au etching solution is used for etching, and the Au etching solution is a mixed solution of iodine, potassium iodide and pure water, and the mass ratio thereof is iodine: potassium iodide: pure water = 2:4:20.

[0019] Furthermore, in step S6, the etching time is 3-4 minutes, and during the etching, the temperature of the Au etching solution is 40-50°C.

[0020] Furthermore, the primary photoresist coating thickness is 1-1.3 μm.

[0021] Furthermore, the coating thickness of the secondary photoresist is 4-4.5 μm.

[0022] Furthermore, the thickness of the thick NiAuGeAu film is 0.5-0.8 μm.

[0023] Furthermore, the thickness of the thick Au film is 1.5-1.9 μm.

[0024] The beneficial effects of the present invention are:

[0025] The present application embodiment provides a method for preparing a quaternary reverse polarity red light tube core N electrode, by first corroding and removing the substrate and barrier layer of the bonded quaternary reverse polarity red light LED epitaxial wafer, and then evaporating a thin NiGeAu film on the surface as an N-type ohmic contact electrode. Then, by utilizing the characteristics of the NiGeAu film, the thin NiGeAu film and the thin GaAs layer are fully fused and infiltrated into the N-type AlGaInP layer by high temperature annealing, and then the thin NiGeAu film and the thin GaAs layer are etched away by a room temperature Au etching solution, and a negative photoresist is applied without removing the positive photoresist to form an N electrode pattern, and then a thick NiGeAu film and a thick Au film are evaporated in sequence, and the redundant Au film outside the N-side electrode is removed by a blue film to obtain a quaternary reverse polarity red light tube core N electrode, thereby avoiding the problem of instability of the quaternary reverse polarity red light tube core N electrode pattern and improving the quality of the chip. This method can obtain a more stable N electrode pattern by conventional means, is easy to operate, and can obtain a more stable roughened surface, which is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the reverse polarity AlGaInP quaternary LED epitaxial wafer;

[0027] Figure 2 The schematic diagram of the structure of the inverted AlGaInP quaternary red LED epitaxial wafer obtained in step S1;

[0028] Figure 3 This is a schematic diagram of the structure of the flip-chip AlGaInP quaternary red LED epitaxial wafer after removing the GaAs substrate and the barrier layer GaInP;

[0029] Figure 4 This is a schematic diagram of the structure after the thin NiAuGeAu film is evaporated in step S3;

[0030] Figure 5 It is a schematic diagram of the structure after one photolithography process;

[0031] Figure 6 It is a schematic diagram of the structure after etching away the thin NiAuGeAu film in the etching area of ​​the primary lithography pattern, the heavily doped GaAs layer and the NiAuGeAu that penetrates into the N-type AlGaInP layer;

[0032] Figure 7 It is a schematic diagram of the structure after the rough surface is coated with photoresist for the second time;

[0033] Figure 8 Schematic diagram of the structure after secondary photolithography;

[0034] Fig. 9 This is a schematic diagram of the structure of the N electrode of the quaternary reverse polarity red light tube core obtained in step S8.

[0035] In the figure: 11, GaAs substrate; 12, barrier layer GaInP; 13, heavily doped GaAs layer; 14, N-type AlGaInP layer; 141, rough surface; 15, quantum well layer; 16, P-type AlGaInP layer;

[0036] 21. P-type ohmic contact layer; 22. current blocking layer; 23. new substrate layer;

[0037] 31. Thin NiAuGeAu film; 32. Thick NiAuGeAu film; 33. Thick Au film;

[0038] 41. First application of photoresist; 42. Second application of photoresist. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described in detail below in conjunction with the drawings in the embodiments of the present application, and the described embodiments are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by those skilled in the art without creative work on the basis of the embodiments of the present application shall belong to the protection scope of the present application.

[0040] Embodiment 1

[0041] A method for preparing a quaternary reverse polarity red light tube core N electrode comprises the following steps:

[0042] S1, sequentially preparing a P-type ohmic contact layer 21 and a current blocking layer 22 on the P-type AlGaInP layer 16 of the reverse polarity AlGaInP quaternary LED epitaxial wafer, and the P-type ohmic contact layer 21 and the current blocking layer 22 are arranged at intervals, and then bonded to a new substrate layer 23, to obtain Figure 2 The inverted AlGaInP quaternary red LED epitaxial wafer shown. The new substrate layer 23 is a single crystal conductive Si substrate or a sapphire substrate.

[0043] As a specific implementation, the reverse polarity AlGaInP quaternary LED epitaxial wafer described in this embodiment includes, from bottom to top, a GaAs substrate 11, a barrier layer GaInP 12, a heavily doped GaAs layer 13, an N-type AlGaInP layer 14, a quantum well layer 15 and a P-type AlGaInP layer 16.

[0044] S2, such as Figure 3 As shown, the GaAs substrate 11 and the barrier layer GaInP 12 of the inverted AlGaInP quaternary red LED epitaxial wafer obtained in step S1 are etched away by a conventional etching method, thereby exposing the epitaxially grown heavily doped GaAs layer 13.

[0045] S3, such as Figure 4 As shown, a thin NiAuGeAu film 31 is deposited on the exposed thin GaAs layer by electron beam evaporation.

[0046] Preferably, the thickness of the thin NiAuGeAu film 31 is 0.0005-0.0010 μm.

[0047] S4 , high temperature annealing, so that the thin NiAuGeAu film 31 is fully integrated with the heavily doped GaAs layer 13 and penetrates into the N-type AlGaInP layer 14 .

[0048] Preferably, the temperature of high temperature annealing in step S4 is 520-550° C., and the annealing time is 10-15 minutes.

[0049] S5, coating the surface of the thin NiAuGeAu film 31 with a photoresist 41, and performing a photolithography process to obtain a Figure 5 The primary lithography pattern shown.

[0050] As a specific implementation, the one-time photolithography pattern described in this embodiment includes a reserved area in the middle with a rectangular structure, and two opposite sides of the reserved area are respectively aligned with the edges of the thin NiAuGeAu film 31, and both sides of the reserved area are corrosion areas.

[0051] S6, such as Figure 6 As shown, Au etching solution is used to etch away the thin NiAuGeAu film 31 in the etching area of ​​the primary lithography pattern. Since the thin NiAuGeAu film 31 and the heavily doped GaAs layer 13 have been fully fused, the heavily doped GaAs layer 13 will be etched away together, and the NiAuGeAu that penetrates into the N-type AlGaInP layer 14 in the etching area of ​​the primary lithography pattern will also be etched away, thereby forming a rough surface 141.

[0052] As a specific implementation, the Au etching solution described in this embodiment is a mixed solution of iodine, potassium iodide and pure water, and the mass ratio is iodine: potassium iodide: pure water = 2:4:20. In step S6, the etching time is 3-4 minutes, and the temperature of the Au etching solution is 40-50°C during the etching.

[0053] S7, such as Figure 7 As shown, the rough surface 141 obtained in step S6 is coated with a secondary photoresist 42, and a secondary photolithography is performed to obtain a Figure 8 The secondary photolithography pattern shown, and the projections of the secondary photolithography pattern and the primary photolithography pattern in the horizontal plane do not completely overlap.

[0054] As a specific implementation, the primary photoresist 41 applied in step S5 of this embodiment is a positive photoresist, and the secondary photoresist applied in step S7 is a negative photoresist. When performing photolithography, the side of the negative photoresist close to the thin NiAuGeAu film 31 is shielded, and the positive photoresist on the upper side of the middle thin NiAuGeAu film 31 and the part of the negative photoresist close to the thin NiAuGeAu film 31 are removed by taking advantage of the fact that the unexposed area of ​​the negative photoresist is removed, while the exposed area of ​​the positive photoresist is removed, and only the part of the negative photoresist away from the thin NiAuGeAu film 31 is retained, thereby obtaining the following: Figure 8 The secondary photolithography pattern shown is prepared for the subsequent evaporation of the thick NiAuGeAu film 32 and the thick Au film 33.

[0055] As a specific implementation, in this embodiment, the coating thickness of the primary photoresist 41 is 1-1.3 μm, and the coating thickness of the secondary photoresist is 4-4.5 μm.

[0056] S8, sequentially evaporating a thick NiAuGeAu film 32 and a thick Au film 33, and using a blue film to remove the thick NiAuGeAu film 32 and the thick Au film 33 evaporated on the residual secondary photoresist, thereby obtaining Fig. 9 The N electrode of the quaternary reverse polarity red light tube core is shown.

[0057] As a specific implementation, in this embodiment, the thickness M of the thick NiAuGeAu film 32 is 0.5-0.8 μm, and the thickness of the thick Au film 33 is 1.5-1.9 μm.

[0058] Embodiment 2

[0059] The difference between this embodiment and the first embodiment is that:

[0060] The primary photoresist 41 applied in step S5 and the secondary photoresist applied in step S7 are both positive photoresists. During photolithography, the side of the negative photoresist away from the thin NiAuGeAu film 31 is shielded, thereby removing the primary photoresist 41 on the upper side of the thin NiAuGeAu film 31 in the middle and part of the secondary photoresist on both sides of the thin NiAuGeAu film 31.

[0061] Embodiment 3

[0062] The difference between this embodiment and the first embodiment is that:

[0063] The primary photoresist 41 applied in step S5 and the secondary photoresist applied in step S7 are both negative photoresists. During photolithography, the upper side of the thin NiAuGeAu film 31 and the two sides of the thin NiAuGeAu film 31 are partially shielded, thereby removing the primary photoresist 41 on the upper side of the thin NiAuGeAu film 31 in the middle and the secondary photoresist located on the two sides of the thin NiAuGeAu film 31.

[0064] Other embodiments obtained by those skilled in the art by combining, splitting, reorganizing, etc. the embodiments of the present application on the basis of the embodiments provided in the present application do not exceed the protection scope of the present application.

[0065] The above specific implementation methods have detailed the purpose, technical solutions and beneficial effects of the embodiments of the present application. The above are only specific implementation methods of the embodiments of the present application and are not used to limit the protection scope of the embodiments of the present application. That is, any modifications, equivalent substitutions, improvements, etc. made on the basis of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.

Claims

1. A method for preparing a quaternary reverse polarity red light tube core N electrode, characterized in that: The following steps are included: S1, sequentially preparing a P-type ohmic contact layer (21) and a current blocking layer (22) on a P-type AlGaInP layer (16) of a reverse polarity AlGaInP quaternary LED epitaxial wafer, and then bonding them to a new substrate layer (23) to obtain a flip-chip AlGaInP quaternary red LED epitaxial wafer; S2, etching away the GaAs substrate (11) and the barrier layer GaInP (12) of the inverted AlGaInP quaternary red LED epitaxial wafer obtained in step S1, thereby exposing the heavily doped GaAs layer (13); S3, evaporating a thin NiAuGeAu film (31) on the exposed thin GaAs layer; S4, high temperature annealing, so that the thin NiAuGeAu film (31) is fully integrated with the heavily doped GaAs layer (13) and penetrates into the N-type AlGaInP layer (14); S5, coating a photoresist (41) on the surface of the thin NiAuGeAu film (31), and performing a photolithography to obtain a photolithography pattern; S6, etching away the thin NiAuGeAu film (31), the heavily doped GaAs layer (13) and the NiAuGeAu that penetrates into the N-type AlGaInP layer (14) in the etching area of ​​the primary lithography pattern, and forming a rough surface (141) on the N-type AlGaInP layer (14); S7, coating the rough surface (141) with a photoresist (42) for a second time, and performing secondary photolithography; S8, sequentially evaporating a thick NiAuGeAu film (32) and a thick Au film (33), and removing excess thick NiAuGeAu film (32) and thick Au film (33).

2. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 1, characterized in that: The new substrate layer (23) is a single crystal conductive Si substrate or a sapphire substrate.

3. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 1, characterized in that: The thickness of the thin NiAuGeAu film (31) is 0.0005-0.0010 μm.

4. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 1, characterized in that: The temperature of high temperature annealing in step S4 is 520-550° C., and the annealing time is 10-15 minutes.

5. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 1, characterized in that: In step S6, Au etching solution is used for etching. The Au etching solution is a mixed solution of iodine, potassium iodide and pure water, and the mass ratio of the mixed solution is iodine: potassium iodide: pure water = 2:4:

20.

6. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 5, characterized in that: In step S6, the etching time is 3-4 minutes, and during the etching, the temperature of the Au etching solution is 40-50°C.

7. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 1, characterized in that: The coating thickness of the primary photoresist (41) is 1-1.3 μm.

8. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 1, characterized in that: The coating thickness of the secondary photoresist is 4-4.5 μm.

9. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 1, characterized in that: The thickness of the thick NiAuGeAu film (32) is 0.5-0.8 μm.

10. The method for preparing a quaternary reverse polarity red light tube core N electrode according to claim 1, characterized in that: The thick Au film (33) has a thickness of 1.5-1.9 μm.

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