A novel AlGaInP quaternary LED chip preparation method

Abstract

The present invention relates to a novel AlGaInP quaternary LED chip preparation method, which comprises: (1) vapor-depositing ITO on the surface of an epitaxial wafer; (2) preparing a photoresist pattern on the surface of the ITO; (3) performing ICP etching on the photoresist pattern until the photoresist on the ITO surface is completely consumed; the ITO area lacking photoresist protection is deeply etched to form an open area; the ITO area protected by the photoresist is shallowly etched to form a roughened area; (4) vapor-depositing ITO on the surface of the epitaxial wafer again; (5) preparing a P-side metal electrode pattern; (6) vapor-depositing the P-side metal electrode using an electron beam evaporation method; (7) grinding the substrate; (8) vapor-depositing the N-side metal electrode; and (9) cutting to obtain an independent chip. The preparation method adopts dry etching for roughening, does not use a roughening liquid, does not require a debonding operation, and has the characteristics of fast time, low cost, and environmental protection.

Description

Technical Field

[0001] The invention relates to a novel AlGaInP quaternary LED chip preparation method, belonging to the field of optoelectronic technology. Background Art

[0002] LEDs, the new lighting source of the 21st century, consume only 1 / 10 the power of ordinary incandescent lamps at the same brightness, yet their lifespan can be extended 100 times. LED devices are cold light sources with high luminous efficiency, low operating voltage, low power consumption, compact size, and flat packaging, making them easy to develop into lightweight products. They also have a robust structure and a very long lifespan. The light source itself does not contain harmful substances such as mercury and lead, and is free of infrared and ultraviolet radiation, generating no environmental pollution during production and use. Therefore, semiconductor lamps offer advantages such as energy saving, environmental protection, and long lifespan. Just as transistors replaced vacuum tubes, semiconductor lamps will inevitably replace traditional incandescent and fluorescent lamps. Whether from the perspectives of saving energy, reducing greenhouse gas emissions, or alleviating environmental pollution, LEDs, as a new lighting source, have great potential to replace traditional lighting sources.

[0003] The AlGaInP material system was originally used to manufacture visible light laser diodes and was first proposed by Japanese researchers in the mid-1980s. LED and LD devices of that period usually used GaAs substrates. 0.5 In 0.5 P is used as the active light-emitting region, with a light-emitting wavelength of 650nm, and is widely used in four-element laser pointers and DVD players. Later, researchers discovered that introducing Al components into GaInP can further shorten the light-emitting wavelength. However, if the Al content is too high, the luminous efficiency of the device will drop sharply. Because when the Al content in GaInP exceeds 0.53, AlGaInP will become an indirect bandgap semiconductor. Therefore, AlGaInP materials are generally only used to prepare LED devices with a light-emitting wavelength of more than 570nm. In 1997, the world's first AlGaInP-based LED with a multiple quantum well (MQW) composite Bragg reflector (DBR) structure was born. LED devices based on this structure design still occupy a large share of the low-end LED market.

[0004] Aluminum gallium indium phosphide (AlGaInP) materials are rapidly developing and being used to produce high-power, high-brightness red and yellow LEDs. While red LEDs made with AlGaInP materials are now commercially available, LEDs using quaternary alloy materials as the multi-quantum well active region exhibit extremely high internal quantum efficiency. However, due to the limitations of the material's refractive index, the external quantum efficiency of conventional AlGaInP-LEDs is extremely low. To improve this efficiency, the light-emitting surface is roughened to improve the light-emitting angle.

[0005] AlGaInP quaternary chip roughening is usually carried out by etching the surface GaP layer to form an uneven surface, which is equivalent to increasing the light-emitting area. Chinese patent document CN104078535 provides a method for roughening the sidewalls of reverse-polarity AlGaInP-based LEDs. The method first uses existing photolithography processes to expose and develop the mesa pattern epitaxial wafer of the reverse-polarity AlGaInP-based LED, forming a periodic edge pattern around the mesa pattern epitaxial wafer; then, the epitaxial wafer developed using deionized water containing saturated Br2 is corroded, and after the etching is completed, it is cleaned and debonded according to conventional processes to achieve the roughening of the LED sidewalls; however, the method provided by the invention requires debonding operations. Due to the influence of solution temperature, time, proportion, etc., there is a problem of non-repeatable roughening effect. The liquid recovery involved has strict environmental protection requirements, resulting in a time-consuming and labor-intensive overall operation with poor results.

[0006] In addition, conventional dry etching roughening requires a separate mask and uses the mask to complete the roughening, and the existing dry etching only roughens the surface. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention provides a novel preparation method for AlGaInP quaternary LED chips, which is suitable for the preparation of positive polarity AlGaInP quaternary LED chips. The preparation method uses dry etching for roughening. This method does not use roughening liquid and does not require degumming operations. It has the characteristics of fast timeliness, low cost, and environmental protection.

[0008] Terminology Notes:

[0009] 1.ICP: Inductively Coupled Plasma.

[0010] The technical solution of the present invention is:

[0011] A novel AlGaInP quaternary LED chip preparation method, the preparation method comprising:

[0012] (1) vapor-depositing ITO on the surface of an epitaxial wafer, wherein the epitaxial wafer includes a GaAs substrate, a buffer layer, an N-type layer, a quantum well, and a P-type layer arranged in sequence from bottom to top;

[0013] (2) preparing a photoresist on the surface of ITO and preparing a photoresist pattern using a photolithography process;

[0014] (3) performing ICP etching on the photoresist pattern prepared in step (2) until the photoresist on the ITO surface is completely consumed; the ITO area lacking photoresist protection is deeply etched to form an open area; the ITO area protected by the photoresist is shallowly etched to form a roughened area;

[0015] Conventional dry etching roughening requires a separate mask, which is used to complete the roughening. In the present invention, the photoresist serves as a mask and plays two roles. First, the areas not covered by the mask will be completely etched, thereby achieving deep etching on the surface of the epitaxial wafer to open holes and form a current blocking layer. Second, the areas covered by the mask will first be etched away due to the difference in etching rate, and then the surface of the epitaxial wafer will be roughened. That is, using photoresist as a mask achieves two purposes at the same time.

[0016] (4) vapor-depositing ITO on the surface of the epitaxial wafer again;

[0017] (5) preparing photoresist and preparing P-side metal electrode pattern;

[0018] (6) using electron beam evaporation to deposit P-side metal electrodes;

[0019] (7) grinding the substrate;

[0020] (8) evaporating an N-side metal electrode on the surface of the ground substrate;

[0021] (9) Obtain independent chips by cutting.

[0022] Preferably, according to the present invention, in step (3), the etching depth of the deep etching is 0.2-0.3 μm, and the etching depth of the shallow etching is 0.05-0.1 μm.

[0023] According to the preferred embodiment of the present invention, in step (3), ICP etching is performed by regulating the ICP etching gas and the ICP etching power in different time periods according to the photoresist pattern prepared in step (2) to obtain different roughening structures. The roughening structure can be regulated by regulating in different steps.

[0024] According to the preferred embodiment of the present invention, in step (3), the ICP etching gas is a mixture of at least one of Ar, Cl2, BCl3, and HBr and O2. By adjusting the composition of the ICP etching gas, the etching rate is changed, thereby achieving the regulation of the roughened structure.

[0025] According to the preferred embodiment of the present invention, in step (3), the power of ICP etching is 100-800 W. By adjusting the power of ICP etching and changing the etching rate, the roughened structure can be regulated.

[0026] According to the preferred embodiment of the present invention, in step (1), the thickness of ITO is

[0027] Preferably according to the present invention, in step (2), the thickness of the photoresist is 0.2-1 μm.

[0028] According to the preferred embodiment of the present invention, in step (4), the thickness of the ITO evaporated again is 0.1-0.3 μm; further preferably, the thickness of the ITO evaporated again is 0.05-0.2 μm.

[0029] Preferably, according to the present invention, in step (6), the material of the P-side metal electrode is any one of Al, Au, AuCu, and TiAl.

[0030] According to a preferred embodiment of the present invention, in step (7), the substrate is ground to a thickness of 120-180 μm.

[0031] According to the preferred embodiment of the present invention, in step (8), the material of the N-side metal is any one of Ni\Ge\Au alloy, Ni\Ge alloy, Ge\Au alloy, and Ni\Au alloy.

[0032] The beneficial effects of the present invention are:

[0033] 1. In this invention, the photoresist serves two purposes as a mask. First, the areas uncovered by the mask are completely etched, creating a deep hole in the epitaxial wafer surface and forming a current-blocking layer. Second, due to the difference in etching rates, the mask is etched away first in the areas covered by the mask, subsequently roughening the epitaxial wafer surface. In other words, using photoresist as a mask achieves two goals simultaneously. Using dry etching, the center hole is dug, spreading the current, while other areas are roughened, improving light extraction efficiency.

[0034] 2. The present invention improves the process flow of AlGaInP quaternary LED chip fabrication, eliminating the need for separate photoresist removal, reducing costs and simplifying the process. Unlike conventional fabrication methods, which require sequential steps such as photolithography, hole formation, secondary photolithography, roughening, and resist removal, the present invention utilizes ICP etching after photolithographically preparing a photoresist pattern to simultaneously create holes and roughen the epitaxial wafer surface.

[0035] 3. The present invention improves the AlGaInP quaternary LED chip preparation method, which is different from the wet roughening method, saves costs, and is beneficial to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a conventional process flow chart for preparing quaternary LED chips;

[0037] Figure 2 This is a process flow chart of a method for preparing an AlGaInP quaternary LED chip provided by the present invention;

[0038] Figure 3 is a schematic diagram of the structure prepared in step (1);

[0039] Figure 4 is a schematic diagram of the top view of the structure prepared in step (2);

[0040] Figure 5 is a schematic diagram of the cross-sectional structure prepared in step (2);

[0041] Figure 6 is a schematic diagram of the structure obtained after ICP etching in step (3);

[0042] Figure 7 It is a schematic diagram of the structure after step (4) of re-evaporating ITO;

[0043] Figure 8 is a schematic diagram of the structure after preparing the P-side metal electrode pattern in step (5);

[0044] Figure 9 This is a schematic diagram of the structure after step (6) evaporation of the P-side metal electrode;

[0045] Figure 10 It is a schematic diagram of the structure after step (8) evaporation of the N-side metal electrode;

[0046] 1. Epitaxial wafer, 2. ITO, 3. Photoresist, 4. Roughened area, 5. Opening area, 6. Re-evaporated ITO, 7. Negative photoresist, 8. P-side metal electrode, 9. N-side metal electrode, 10. Photoresist pattern. DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to the embodiments and the accompanying drawings, but is not limited thereto.

[0048] Example 1

[0049] A method for preparing an AlGaInP quaternary LED chip, such as Figure 2 Shown, including:

[0050] (1) Figure 3 As shown, ITO2 is evaporated on the surface of the epitaxial wafer 1, which includes a GaAs substrate, a buffer layer, an N-type layer, a quantum well layer and a P-type layer arranged in sequence from bottom to top; the thickness of ITO2 is

[0051] (2) preparing a photoresist 3 on the surface of ITO 2, and using a photolithography process to prepare a photoresist pattern 10; Figure 4 and Figure 5 As shown, the center of the photoresist pattern 10 is circular, and the central circular area is removed by photolithography to form an opening. The thickness of the photoresist 3 is 0.2-1 μm.

[0052] (3) Figure 6As shown, the photoresist pattern 10 prepared according to step (2) is subjected to ICP etching until the photoresist 3 on the surface of ITO2 is completely consumed; the ITO2 area lacking the protection of the photoresist 3 is deeply etched to form an opening area 5; the ITO2 area protected by the photoresist 3 is shallowly etched to form a roughened area 4;

[0053] Conventional dry etching roughening requires a separate mask, which is used to complete the roughening. In this patent, the photoresist 3 serves as a mask and plays two roles. First, the area not covered by the mask will be completely etched to achieve deep etching on the surface of the epitaxial wafer 1 to open holes and form a current blocking layer; second, the area covered by the mask will first be etched away due to the difference in etching rate, and then the surface of the epitaxial wafer 1 will be roughened; that is, using the photoresist 3 as a mask achieves two purposes at the same time.

[0054] The pattern obtained in step 2 is subjected to ICP etching. The ICP etching gas is a mixture of Cl2, BCl3 and O2. The etching is performed until the surface photoresist 3 is completely consumed.

[0055] (4) Evaporating ITO again on the surface of epitaxial wafer 1, the re-evaporated ITO6 is used as a current spreading layer; the thickness of the re-evaporated ITO6 is 0.05-0.2 μm, such as Figure 7 shown.

[0056] (5) Perform photolithography, use negative photoresist 7, and lift-off process to prepare the P-side metal electrode 8 pattern, such as Figure 8 shown.

[0057] (6) Electron beam evaporation is used to deposit electrodes. The P-side metal electrode 8 is any one of Al, Au, AuCu, and TiAl. Figure 9 shown.

[0058] (7) Grind the wafer from step 6 to a final thickness of 120-180 μm.

[0059] (8) An N-side metal electrode 9 is deposited on the surface of the ground substrate. The N-side metal electrode 9 is an alloy of Ni\Ge\Au or several alloys thereof, such as Figure 10 shown.

[0060] (9) Cutting with a grinding wheel knife to obtain independent chips.

[0061] Example 2

[0062] The method for preparing an AlGaInP quaternary LED chip provided in Example 1 has the following differences:

[0063] In step (3), ICP etching is performed by regulating the ICP etching gas and the ICP etching power in 10 time periods according to the photoresist pattern prepared in step (2) to obtain different roughened structures.

[0064] The etching gas is a mixture of Ar, Cl2, BCl3, and HBr. The initial etching time is 2-3 minutes, and the etching power is 200W.

[0065] Etch again with a mixed gas of Ar, Cl2, BCl3, HBr and O2 for 2-3 minutes and an etching power of 200W to completely consume the surface photoresist 3.

[0066] Example 3

[0067] The method for preparing an AlGaInP quaternary LED chip provided in Example 1 has the following differences:

[0068] In step (1), the thickness of ITO2 evaporated on the surface of epitaxial wafer 1 is

[0069] In step (3), ICP etching is performed by regulating the ICP etching gas and the ICP etching power in 10 time periods according to the photoresist pattern prepared in step (2) to obtain different roughened structures.

[0070] The etching gas is a mixture of Ar, Cl2, BCl3, and HBr. The initial etching time is 2-3 minutes and the etching power is 200W.

[0071] Etch again with a mixed gas of Ar, Cl2, BCl3, HBr and O2 for 2-3 minutes and an etching power of 200W to completely consume the surface photoresist 3.

[0072] The surface of the epitaxial wafer 1 is roughened by the preparation method provided in this embodiment.

[0073] Comparative Example 1

[0074] The conventional AlGaInP quaternary LED chip preparation method is as follows Figure 1 Shown, including:

[0075] (1) preparing a photoresist on the surface of the epitaxial wafer and preparing a photoresist pattern using a photolithography process; the epitaxial wafer includes a GaAs substrate, a buffer layer, an N-type layer, a quantum well layer, and a P-type layer arranged in sequence from bottom to top;

[0076] (2) Holes are made on the surface of the epitaxial wafer; usually by wet etching.

[0077] (3) Performing a second photolithography step, using photoresist to protect the non-roughened area and expose the roughened area;

[0078] (4) Wet etching is then performed using the etching solution, and the anisotropy of the wet etching is used to form an uneven surface to achieve a roughening effect.

[0079] (5) After the roughening is completed, the degumming operation is carried out, that is, the roughening process is completed.

[0080] (6) ITO is evaporated again on the surface of the epitaxial wafer; the thickness of the evaporated ITO is 0.05-0.2 μm.

[0081] (7) Perform photolithography operations, using negative photoresist and a lift-off process to prepare P-side metal electrode patterns.

[0082] (8) Grind the wafer from step 6 to a final thickness of 120-180 μm.

[0083] (9) An N-side metal electrode is evaporated on the surface of the ground substrate. The N-side metal electrode is an alloy of Ni\Ge\Au or several alloys thereof.

[0084] (10) Cutting with a grinding wheel knife to obtain independent chips.

[0085] In the preparation method provided by the comparison, the entire process involves a yellow light chamber and a chemical station. Since wet roughening is affected by the solution temperature, time, proportion, etc., there is a problem of non-repeatable roughening effect. The liquid recovery involves strict environmental protection requirements, resulting in the overall operation being time-consuming, labor-intensive and ineffective.

[0086] As can be seen from the above, the AlGaInP quaternary LED chip fabrication method provided by the present invention, after photolithographically preparing a photoresist pattern, uses ICP etching to create pores on the epitaxial wafer surface and simultaneously roughen the surface of the epitaxial wafer. This method, which eliminates the need for roughening liquid and resist stripping, is characterized by rapid processing, low cost, and environmental friendliness. Furthermore, the roughening effect can be controlled, achieving unexpected technical benefits.

Claims

1. A novel AlGaInP quaternary LED chip preparation method, characterized in that: The preparation method comprises: (1) vapor-depositing ITO on the surface of an epitaxial wafer, wherein the epitaxial wafer includes a GaAs substrate, a buffer layer, an N-type layer, a quantum well, and a P-type layer arranged in sequence from bottom to top; (2) preparing a photoresist on the surface of ITO and preparing a photoresist pattern using a photolithography process; (3) performing ICP etching on the photoresist pattern prepared in step (2) until the photoresist on the ITO surface is completely consumed; The ITO area without photoresist protection is deeply etched to form an open area; The ITO area protected by the photoresist is shallowly etched to form a roughened area; According to the photoresist pattern prepared in step (2), ICP etching is performed by regulating the ICP etching gas and the ICP etching power in different time periods to obtain different roughening structures; (4) vapor-depositing ITO on the surface of the epitaxial wafer again; (5) preparing photoresist and preparing P-side metal electrode pattern; (6) using electron beam evaporation to deposit P-side metal electrodes; (7) grinding the substrate; (8) evaporating an N-side metal electrode on the surface of the ground substrate; (9) Obtain independent chips by cutting.

2. A novel AlGaInP quaternary LED chip preparation method according to claim 1, characterized in that: In step (3), the etching depth of deep etching is 0.2-0.3 μm, and the etching depth of shallow etching is 0.05-0.1 μm.

3. The method for preparing a novel AlGaInP quaternary LED chip according to claim 1, characterized in that: In step (3), the ICP etching gas is a mixed gas of at least one of Ar, Cl2, BCl3, HBr and O2.

4. The method for preparing a novel AlGaInP quaternary LED chip according to claim 1, characterized in that: In step (3), the power of ICP etching is 100-800W.

5. The method for preparing a novel AlGaInP quaternary LED chip according to claim 1, characterized in that: In step (1), the thickness of ITO is 50-300Å.

6. The method for preparing a novel AlGaInP quaternary LED chip according to claim 1, characterized in that: In step (2), the thickness of the photoresist is 0.2-1 μm.

7. The method for preparing a novel AlGaInP quaternary LED chip according to claim 1, characterized in that: In step (4), the thickness of the ITO evaporated again is 0.1-0.3 μm.

8. The method for preparing a novel AlGaInP quaternary LED chip according to claim 7, characterized in that: In step (4), the thickness of ITO evaporated again is 0.05-0.2 μm.

9. The method for preparing a novel AlGaInP quaternary LED chip according to claim 1, characterized in that: In step (6), the material of the P-side metal electrode is any one of Al, Au, AuCu, and TiAl.

10. The method for preparing a novel AlGaInP quaternary LED chip according to claim 1, characterized in that: In step (7), the substrate is ground to a thickness of 120-180 μm.

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