High-brightness-ratio chip coarsening etching solution as well as preparation method and application thereof

Abstract

The invention relates to a high-brightness-ratio chip coarsening etching solution and a preparation method and application thereof, and the high-brightness-ratio chip coarsening etching solution comprises the following components by weight: 20-50 parts of quaternary ammonium hydroxide; 20-50 parts of ammonium salt; 1-15 parts of a buffer agent; 0.1 to 1 part of a surfactant; and 30-50 parts of ultrapure water. The addition of the buffer agent can inhibit the generation of precipitates, balance the pH and Factivity, control the etching rate, form a uniform and fine pyramid structure on the surface of the epitaxial layer, and avoid the problem of over-etching caused by too fast local micro-chemical reaction; and meanwhile, the buffer agent can also enable the quaternary ammonium hydroxide to be uniformly adsorbed on the LED chip, so that further lateral erosion is avoided.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing processes, and particularly relates to a high brightness ratio chip roughening etching solution, its preparation method, and its application. Background Technology

[0002] Light-emitting diodes (LEDs), as highly efficient and energy-saving light sources, are widely used in traffic lights, outdoor displays, and LCD backlighting. They offer significant advantages over LCDs in terms of brightness, resolution, contrast ratio, energy consumption, lifespan, response speed, and stability, and are considered a next-generation display technology. LEDs can be produced in various colors, from red to green, by changing the proportions of elements in the alloy semiconductor. However, according to Snell's law, the light extraction efficiency of planar LEDs is related to the refractive index of the material. For planar LEDs, only about 2.3% of the photons emitted from the quantum well can escape, which greatly limits the light extraction efficiency (LEE) of LEDs.

[0003] As the chip size of next-generation display technology Micro-LED decreases and the surface-to-volume ratio of the device increases, its luminous efficiency decreases sharply with the reduction in device size. Therefore, many methods have emerged to improve the light extraction efficiency of LEDs, including surface roughening, surface patterning using laser, electron beam or ion beam etching, patterned substrates, and plasmonic nanostructures.

[0004] Among these, surface roughening technology, primarily based on wet etching, is a mature, reliable, simple, and low-cost technique with excellent application prospects and large-scale industrialization capabilities globally. Surface roughening technology reduces total internal reflection and improves light extraction efficiency by altering the LED surface morphology (such as nanopillars, nanopores, and hexagonal pyramids). For example, a hexagonal pyramid + nanorod composite structure, depositing Ag nanorods (50-140nm in diameter) on the surface of a photochemically etched hexagonal pyramid, reduces Fresnel reflection through gradient refractive index, increasing light output power by 14%. A team at Xiamen University in China designed a fluoropolymer encapsulation structure combined with a ceramic substrate for the reflective sidewalls, increasing forward light extraction efficiency from <50% to 94%. The Institute of Semiconductors, Chinese Academy of Sciences, optimized the hexagonal pyramid sidewall roughening parameters through numerical simulation, improving light extraction efficiency by 20%-25%. A US team fabricated nanopillar arrays on sapphire substrates, improving light extraction efficiency by 30%; Japan developed a tilted sidewall structure, improving light extraction efficiency by 25%. However, most of these methods involve complex chemical processes or require expensive equipment, thus limiting their widespread application in actual LED manufacturing.

[0005] The types of etching solutions commonly used in LED manufacturing may include inorganic acids (such as hydrochloric acid and sulfuric acid), organic acids (such as citric acid and oxalic acid), alkaline solutions (such as potassium hydroxide and tetramethylammonium hydroxide), and mixed acid systems.

[0006] Patent CN116333745A discloses an inorganic acid etching solution containing inorganic acids such as hydrochloric acid, phosphoric acid, phosphorous acid, hypophosphoric acid, nitric acid, or sulfuric acid. This type of inorganic acid etching solution has poor etching uniformity and is prone to over-etching, which can damage the device structure.

[0007] Japanese Patent Application Publication No. 2001-267307 uses a mixed acid system of acetic acid-sulfuric acid-hydrochloric acid-hydrogen peroxide. This type of system has complex interactions between the components, unstable etching rate, difficulty in controlling the etched surface morphology, drastic changes in etching rate, and a narrow process window.

[0008] Chinese patent CN106206874A uses alkaline etching solution to roughen the GaN epitaxial wafer in the clearance area exposed outside the metal protective layer. Alkaline etching solution such as KOH is highly dangerous and can easily produce "honeycomb" or "groove" defects on the device surface, increasing the surface state density and affecting the luminous efficiency and lifespan of the LED.

[0009] To address the aforementioned issues, this invention proposes for the first time an alkaline LED chip roughening solution with quaternary ammonium hydroxide as the main component. Quaternary ammonium hydroxide, as an organic alkaline solution, exhibits stable corrosion performance and can corrode GaN crystal planes other than the c-plane, without introducing metal ions during the process. Simultaneously, the introduction of metal halide compounds as buffers effectively reduces "honeycomb" or "groove" defects on the LED chip surface, improving surface morphology uniformity. It also effectively suppresses lateral etching, resulting in more vertical etched sidewalls, which can effectively increase the external quantum efficiency of Mini / Micro-LEDs and significantly improve the brightness ratio. Summary of the Invention

[0010] The technical problem solved by this invention is the low luminous efficiency caused by the excessive refractive index of the LED surface after etching with a roughening etching solution.

[0011] In view of the technical problems existing in the prior art, this invention designs an LED chip roughening etching solution with the characteristics of fine and dense roughening particles and uniform roughening of the LED surface, solving the problem of low luminous efficiency caused by excessive refractive index. Simultaneously, this solution can effectively repair sidewall damage caused by etching in Mini / Micro-LEDs, thereby further increasing luminous intensity and uniformity. The LED roughening etching solution of this invention inhibits the formation of HF and hydroxide precipitates in an alkaline environment, ensuring etching uniformity. It also inhibits lateral etching, obtaining more vertical etched sidewalls, forming a uniform and dense pyramid structure on the epitaxial layer surface, and reducing "honeycomb" or "groove" defects on the LED chip surface.

[0012] It should be noted that, in this invention, unless otherwise specified, the specific meaning of "comprising" in relation to composition definition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," etc., and similar meanings.

[0013] To solve the aforementioned technical problems, the present invention adopts the following solution:

[0014] [The first technical solution]

[0015] A high-brightness-ratio chip roughening etching solution, characterized in that it comprises the following components by weight:

[0016] 20-50 parts of quaternary ammonium hydroxide;

[0017] 20-50 parts of ammonium salt;

[0018] 1-15 parts buffer;

[0019] Surfactant 0.1-1 part;

[0020] 30-50 parts ultrapure water;

[0021] The buffer is a metal halide compound.

[0022] Furthermore, the metal in the buffer is selected from alkali metals or Group IIB metals.

[0023] Furthermore, the metal in the buffer is rubidium or cadmium, and the halogen is one or more of bromine, iodine, chlorine, and fluorine.

[0024] Furthermore, the buffer is one or more of rubidium iodide, rubidium bromide, cadmium bromate, rubidium iodate, and rubidium dichloroiodate.

[0025] Furthermore, the quaternary ammonium hydroxide is one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetramethylammonium hydroxide.

[0026] Furthermore, the ammonium salt is one or more of ammonium fluoride, ammonium bifluoride, ammonium chloride, ammonium sulfate, ammonium bisulfate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

[0027] Furthermore, the surfactant is one or more of tetradecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, dodecyltriethylammonium bromide, decadecyltrimethylammonium bromide, n-octyltrimethylammonium bromide, sodium dodecyl sulfonate, sodium decadecyl sulfonate, and sodium octadecyl sulfonate.

[0028] Furthermore, the ultrapure water is deionized water with a resistance of at least 18 MΩ.

[0029] In this invention, in order to further optimize the performance of the high brightness ratio chip roughening etching solution, the components can be optimized as follows: 20-40 parts of quaternary ammonium hydroxide; 20-40 parts of ammonium salt; 5-10 parts of buffer; 0.1-0.8 parts of surfactant; and 35-50 parts of ultrapure water.

[0030] In this invention, the buffer is preferably rubidium dichloroiodate.

[0031] In this invention, the quaternary ammonium hydroxide is preferably tetramethylammonium hydroxide.

[0032] In this invention, the ammonium salt is preferably ammonium fluoride.

[0033] In this invention, the surfactant is preferably sodium dodecyl sulfonate.

[0034] [Second Technical Solution]

[0035] A method for preparing the above-mentioned high brightness ratio chip roughening etching solution includes the following steps:

[0036] Step 1: Weigh out the respective amounts of each component;

[0037] Step 2: Add quaternary ammonium hydroxide, ammonium salt, buffer, and surfactant to ultrapure water, and then stabilize the temperature at 20-40℃ with stirring until all materials are completely dissolved to prepare the high brightness ratio chip roughening etching solution.

[0038] [The third technical solution]

[0039] A method for using the above-mentioned high brightness ratio chip roughening etchant includes the following steps:

[0040] Step 1: Immerse the chip in a 20-30℃ hydrofluoric acid solution to clean surface contaminants, then rinse the chip in ultrapure water and blow dry;

[0041] Step 2: Immerse the chip obtained in Step 1 in a high brightness ratio chip roughening etching solution for a certain period of time to obtain the immersed LED chip;

[0042] Step 3: Rinse the soaked LED chip obtained in Step 2 in ultrapure water and dry it;

[0043] Step 4: Repeat steps 2 and 3, observing the surface condition of the LED chip after each step, until a uniform and dense pyramid structure is formed on the surface of the epitaxial layer after the surface roughening etching morphology.

[0044] Furthermore, the LED chip etching depth obtained in step 4 is ≤1.5μm, preferably 0.7-1.5μm.

[0045] Furthermore, the hydrofluoric acid solution mentioned in step 1 is a mixture of hydrofluoric acid and deionized water in a mass ratio of 3:97; the soaking time is 10-30 seconds.

[0046] Furthermore, in step 2, soaking is performed at 40-70℃ for 2-10 minutes.

[0047] [Fourth technical solution]

[0048] The above-mentioned high brightness ratio chip roughening etchant is used in the field of LED chip, especially LED epitaxial layer surface roughening.

[0049] Furthermore, the roughening etching solution of the present invention can be used for surface roughening treatment of Mini / Micro-LED epitaxial layers such as AlGaInP layers, ALGaAs layers, and GaN layers, forming a uniform and dense pyramid structure on the surface of the epitaxial layer, and achieving the required roughening state by micro-patterning the surface, thereby significantly improving the LED brightness ratio.

[0050] This invention provides a high-brightness-ratio chip roughening etching solution, its preparation method, and its application, which have the following beneficial effects:

[0051] 1. The addition of the buffer in this invention can suppress precipitation formation, control the etching rate, and form a uniform and dense pyramid structure on the surface of the epitaxial layer, avoiding excessively rapid local microchemical reactions that could cause over-etching. At the same time, the buffer can also allow quaternary ammonium hydroxide to be uniformly adsorbed on the LED chip, preventing further lateral etching.

[0052] 2. The surfactant of the present invention can not only reduce surface tension, but also allow the gas generated by etching to leave the chip surface in time, reduce the "honeycomb" or "groove" defects on the LED chip surface, and improve the uniformity of surface morphology. At the same time, the addition of surfactant can also compensate for the high ionic strength of quaternary ammonium hydroxide and reduce lateral etching.

[0053] 3. The roughening etching solution of the present invention can be used for surface roughening treatment of III-V semiconductor epitaxial layers such as AlGaInP, AlGaAs, and GaN layers. It can effectively increase the external quantum efficiency of Mini / Micro-LEDs, improve the brightness ratio, and solve the problem of low luminous efficiency caused by excessive refractive index. At the same time, the solution can effectively repair sidewall damage caused by etching in Mini / Micro-LEDs, thereby further increasing luminous intensity and luminous uniformity.

[0054] After the LED roughening etching solution of this invention has been used, the LED chip can be cleaned simply by rinsing with pure water, making it convenient to use. It has excellent application prospects and great potential for large-scale industrial application in the field of LED chip etching. Attached Figure Description

[0055] Figure 1 : A 1000x magnified microscope image of an LED chip after roughening it with the roughening etching solution of Comparative Example 1;

[0056] Figure 2 : This is a 1000x magnified microscope image of an LED chip after roughening it with the roughening etching solution from Example 1. Detailed Implementation

[0057] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0058] In this invention, Examples 1-9 and Comparative Examples 1-5 disclose various roughening etching solutions, the components and mass ratios of which are shown in Tables 1 and 2.

[0059] Table 1. Components and proportions of high-brightness-ratio chip roughening etching solutions for Examples 1-9

[0060] Table 2. Components and proportions of the roughening etching solutions in Comparative Examples 1-5

[0061] The preparation method of the high brightness ratio chip roughening etching solution of the present invention is as follows:

[0062] Step 1: Weigh out the respective amounts of each component;

[0063] Step 2: First, add ultrapure water to the container, then add quaternary ammonium hydroxide, ammonium salt, buffer and surfactant. Stir and stabilize the temperature of the container at 20-40℃ until all materials are completely dissolved to prepare the high brightness ratio chip roughening etching solution.

[0064] The method of using the high brightness ratio chip roughening etching solution of the present invention is as follows:

[0065] Step 1: Immerse the LED chip in a 20-30℃ 3% hydrofluoric acid solution (a mixture of hydrofluoric acid and deionized water in a mass ratio of 3:97) to clean the surface contaminants. After immersing for 10-30 seconds, rinse the LED chip twice in ultrapure water and then blow dry.

[0066] Step 2: Place the LED chip obtained in Step 1 into a high brightness ratio chip roughening etching solution and immerse it at 40-70℃ for 2-10 minutes to obtain the immersed LED chip.

[0067] Step 3: Rinse the soaked LED chip obtained in Step 2 twice in ultrapure water and then blow dry;

[0068] Step 4: Repeat steps 2 and 3, observing the surface condition of the LED chip after each step, until a uniform and dense pyramid structure is formed on the surface of the epitaxial layer with a roughened etching morphology and an etching depth ≤1.5μm.

[0069] Regarding performance testing and explanation:

[0070] The test method for performance 1, coarsening effect, is as follows:

[0071] Step 1: Immerse the LED chip in a 3% hydrofluoric acid solution at 20-30℃ for 10 seconds, then rinse the chip twice in ultrapure water and blow it dry.

[0072] Step 2: Place the LED chip obtained in Step 1 into the roughening etching solution and immerse it at 65°C for 5 minutes to obtain the immersed LED chip;

[0073] Step 3: Rinse the soaked LED chip obtained in Step 2 twice in ultrapure water and then blow dry;

[0074] Repeat steps 2 and 3 twice, and observe the particle size on the surface of the roughened LED chip using an optical microscope.

[0075] The ultrapure water used in steps 1, 2, and 3 is deionized water with a resistivity ≥18MΩ. Performance 2: The test method for the brightness improvement ratio of the roughened LED chip is as follows:

[0076] The brightness of an LED chip before and after coarsening is measured using an LED chip brightness meter. The ratio of the brightness after coarsening to the brightness before coarsening is the brightness enhancement ratio of the LED.

[0077] Performance 3: The etching depth test method after roughening is as follows:

[0078] The etching depth of the roughened LED chip was measured using a scanning electron microscope.

[0079] The performance test results of the roughening etching solutions obtained in Examples 1-9 and Comparative Examples 1-5 are shown in Table 3.

[0080] Table 3 Test Data

[0081] Analysis and explanation of the test results:

[0082] As can be seen from the test data in Table 3, the roughening effect and the brightness improvement ratio after roughening in the embodiment are both better than those in the comparative example, and the roughening depth in the embodiment is also better than that in the comparative example. In particular, in comparative example 4, the addition of potassium hydroxide led to excessive etching depth, resulting in uneven particles after etching and a reduced brightness improvement ratio. Comparative example 5 does not contain quaternary ammonium hydroxide, therefore the etching rate of comparative example 5 is low and the roughening effect is not obvious, with both the brightness improvement ratio and the roughening depth being relatively low.

[0083] Comparative Example 1, due to the lack of buffer, is prone to secondary reactions on the surface of the LED chip, resulting in sidewall corrosion and hole defects, which in turn causes uneven etching rate and runaway.

[0084] Comparative Example 2: The lack of surfactant led to differences in liquid surface tension, resulting in poor local spreadability and uneven roughening.

[0085] Comparative Example 3 used potassium iodide as a buffer. However, potassium iodide has limited buffering capacity and is susceptible to acidic byproducts (such as Al) in alkaline systems. 3+ Ga 3+ H produced by hydrolysis + The pH value fluctuates drastically during the etching process due to the influence of pH.

[0086] Comparative Example 4 uses KOH instead of tetramethylammonium hydroxide. Because KOH has high selective corrosion of Al components, the Al-rich areas on the LED chip surface are preferentially etched, forming rough etching pits. This makes it difficult to control the etching rate and easily leads to over-etching, which is reflected on the sample surface as large coarsened particles.

[0087] Comparative Example 5 uses tert-butanol instead of tetramethylammonium hydroxide. Since the alkalinity of tert-butanol is much weaker than that of tetramethylammonium hydroxide, it cannot effectively promote the dissolution of oxides on the surface of LED chips, resulting in a significant decrease in the roughening rate and only a slight reaction on the surface. The roughening depth is too low to form a pyramid-shaped structure, resulting in a low brightness ratio.

[0088] Further comparison can be made using the accompanying diagrams in the instruction manual:

[0089] Figure 1 A 1000x magnified microscope image of an LED chip after roughening it with the roughening etching solution of Comparative Example 1; Figure 2This is a 1000x magnified microscope image of an LED chip after roughening it with the roughening etching solution from Example 1.

[0090] from Figure 1 and 2 As can be seen, compared with the LED chip roughened using Comparative Example 1, the surface particles of the LED chip roughened using Example 1 are finer, smaller and more closely arranged, while the surface particles of the LED chip roughened using Comparative Example 1 are larger and more dispersed, resulting in a poorer roughening effect.

[0091] The present invention has been described above by way of example with reference to the embodiments and accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A high-brightness-ratio chip roughening etching solution, characterized in that, Based on parts by weight, it includes the following components: 20-50 parts of quaternary ammonium hydroxide; 20-50 parts of ammonium salt; 1-15 parts buffer; Surfactant 0.1-1 part; 30-50 parts ultrapure water; The buffer is a metal halide compound.

2. The high brightness ratio chip roughening etching solution according to claim 1, characterized in that: The metal in the buffer is rubidium or cadmium, and the halogen is one or more of bromine, iodine, chlorine, and fluorine.

3. The high brightness ratio chip roughening etching solution according to claim 1 or 2, characterized in that: The buffer is one or more of rubidium iodide, rubidium bromide, cadmium bromate, rubidium iodate, and rubidium dichloroiodate.

4. The high brightness ratio chip roughening etching solution according to claim 1, characterized in that: The quaternary ammonium hydroxide is one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetramethylammonium hydroxide.

5. The high brightness ratio chip roughening etching solution according to claim 1, characterized in that: The ammonium salt is one or more of the following: ammonium fluoride, ammonium hydrogen fluoride, ammonium chloride, ammonium sulfate, ammonium hydrogen sulfate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

6. The high brightness ratio chip roughening etching solution according to claim 1, characterized in that: The surfactant is one or more of tetradecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, dodecyltriethylammonium bromide, decadecyltrimethylammonium bromide, n-octyltrimethylammonium bromide, sodium dodecyl sulfonate, sodium decadecyl sulfonate, and sodium octadecyl sulfonate.

7. A method for preparing a high-brightness-ratio chip roughening etching solution according to any one of claims 1-6, characterized in that... Includes the following steps: Step 1: Weigh out the respective amounts of each component; Step 2: Add quaternary ammonium hydroxide, ammonium salt, buffer, and surfactant to ultrapure water, and then stabilize the temperature at 20-40℃ with stirring until all materials are completely dissolved to prepare the high brightness ratio chip roughening etching solution.

8. A method of using the high brightness ratio chip roughening etching solution according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Immerse the chip in hydrofluoric acid solution to clean surface contaminants, then rinse the chip in ultrapure water and dry it. Step 2: Immerse the chip obtained in Step 1 in a high brightness ratio chip roughening etching solution for a certain period of time to obtain the immersed LED chip; Step 3: Rinse the soaked LED chip obtained in Step 2 in ultrapure water and dry it; Step 4: Repeat steps 2 and 3, observing the surface condition of the LED chip after each step, until a uniform and dense pyramid structure is formed on the surface of the LED chip.

9. The method according to claim 8, characterized in that: The etching depth of the LED chip obtained in step 4 is ≤1.5μm.

10. The use of the high brightness ratio chip roughening etchant according to any one of claims 1-6 in the field of LED chip surface roughening.

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