LED chip roughening liquid, and preparation method and application thereof

Abstract

The application discloses an LED chip roughening liquid and a preparation method and application thereof, and belongs to the field of surface roughening of semiconductor material multi-element metal compounds. The roughening liquid comprises inorganic acid, organic acid, polyamine compound, oxidizing agent, wetting agent and the like; by adding a perfluorinated surfactant with high stability and low surface tension, the roughening interface tension is effectively reduced, the roughening product and bubbles are quickly separated from the reaction interface, the roughening interface is promoted to be in a uniform state, the problem of uneven roughening surface depth is effectively solved, the roughening surface quality is improved, the light output rate is effectively increased, and the LED light emitting intensity is improved. The roughening liquid can perform surface micro patterning on the LED chip under normal temperature conditions to form a concave-convex rough surface. The roughening agent is easy to operate and low in cost, the reaction condition is normal temperature and easy to control, and can be applied to industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to a roughening solution, a preparation method and a use method, and belongs to the field of roughening of surfaces of multi-element metal compounds of semiconductor materials. More particularly, it relates to a roughening solution for micro patterning of a multi-element metal semiconductor light-emitting layer used in a light extraction surface of a light-emitting diode (LED) and a roughening method using the same. BACKGROUND

[0002] LEDs require high light-emitting efficiency. Moreover, the light-emitting efficiency of an LED is determined by the internal quantum efficiency of a light-emitting layer and the light extraction rate, and the quantum efficiency of a light-emitting material is difficult to improve technically because the material composition structure is fixed, so in order to improve the light-emitting efficiency of an LED, the light extraction efficiency must be improved.

[0003] Micro patterning of the surface of a light-emitting layer of an LED increases the light refraction efficiency and reduces light loss, which is an effective technology for improving the light extraction rate. Red LEDs are a widely used optoelectronic product on the market, and the internal quantum efficiency of a red LED can reach more than 95%, but the light-emitting efficiency of a common AlGaInP-based red LED is less than 10%. This is because a portion of the light is absorbed by lattice defects, a portion of the light is absorbed by an opaque substrate, and a portion of the light is lost due to total reflection during the light emission process.

[0004] Therefore, it is of practical significance to study how to improve the light extraction efficiency of LED. So far, domestic and foreign scholars have made certain progress in improving the light extraction efficiency of LED chips through methods such as growing Bragg reflection layer, growing current expansion layer, growing current blocking layer, surface roughening, flip-chip soldering and designing die geometry. Among them, the surface roughening method is generally considered to be an effective method to improve the light extraction efficiency of LED chips. However, it is more difficult to roughen red and yellow light, and it is difficult to control the uniformity of roughening. For example, Chinese Patent Publication No. CN103456855A discloses a LED surface roughening chip and a manufacturing method, which mentions a LED chip surface roughening method with complicated process, high operation temperature and difficult process. Chinese Patent Publication No. CN102185040A discloses a wet chemical etching LED surface roughening process. The chemical etching liquid used in the roughening process is a mixture of aqua regia and deionized water. After chemical wet etching of the LED surface, small pits with a diameter of 6 μm are formed on the light emitting surface. However, after roughening, the surface topography is not uniform, the pyramid structure is not fine and dense, the improvement of light extraction efficiency is limited, and the production safety hazard exists. Japanese Patent Publication No. 5-326485 discloses a method of roughening the chip with sulfuric acid. In actual production, the concentrated sulfuric acid is prone to over-etching, and the surface roughening is seriously uneven. At the same time, the roughening conditions are harsh, and the production line is difficult to implement. Japanese Patent Publication No. 2001-267307 discloses a roughening liquid and a roughening method using glacial acetic acid-sulfuric acid-hydrochloric acid-hydrogen peroxide. In actual operation, the roughening liquid is unstable, the surface roughening particle size is not uniform, and it does not meet the batch operation requirements.

[0005] Therefore, it is urgent to study a surface roughening method which is simple in process, easy to operate and can effectively improve the light extraction efficiency, especially for the surface roughening method of semiconductor light emitting diode (LED) chip. SUMMARY

[0006] In view of the problems of high cost, complex process and poor effect of the existing surface roughening technology of multi-element compound light emitting layer of LED chip, the present application provides a roughening liquid, a preparation method and a use method. The roughening liquid is simple to prepare, stable to use, safe and effective to use, and can significantly improve the light extraction efficiency of LED chip after being applied to the surface roughening of LED chip.

[0007] The technical scheme of the present application is: a roughening liquid, which comprises the following components and their mass percentages:

[0008] Inorganic acid 5-30%, preferably 10-20%,

[0009] Organic acid 5-10%,

[0010] Polyamine compound 5-20%,

[0011] oxidizing agent 0.1-5%,

[0012] wetting agent 0.01-1%,

[0013] the rest is deionized water.

[0014] The inorganic acid is one or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, and hydrofluoric acid. Preferably, it is nitric acid and / or hydrofluoric acid.

[0015] Further, the mass fraction of hydrochloric acid is 37%, the mass fraction of phosphoric acid is 85%, the mass fraction of sulfuric acid is 98%, the mass fraction of hydrofluoric acid is 40%, and the mass fraction of nitric acid is 40%.

[0016] The organic acid is one or more of formic acid, acetic acid, butyric acid, oxalic acid, tartaric acid, succinic acid, citric acid, gluconic acid, aminocaproic acid, methylsulfonic acid, methylbenzenesulfonic acid, p-hydroxybenzenesulfonic acid, and sulfamic acid. Preferably, it is tartaric acid, succinic acid, or citric acid. The organic acid functions to maintain the pH of the roughening solution constant, ensure the hydrogen ion concentration constant during the roughening process, and prevent the reaction rate from being unstable.

[0017] The polyamine is one or more of ethylenediamine, hexamethylenediamine, hexamethylenetetramine, triethanolamine, ammonium chloride, glycine, aspartic acid, ammonium phosphate, and ammonium carbonate. Preferably, it is ethylenediamine or ammonium chloride. The polyamine compound functions to complex with metal ions in the roughening solution, control the metal ion concentration balance, and prevent the roughening solution from causing excessive etching due to the excessively fast reaction rate of AlGaInP materials.

[0018] The oxidizing agent is one or more of hydrogen peroxide, potassium dichromate, potassium periodate, cerium ammonium nitrate, ammonium iron sulfate, iron nitrate, iron chloride, potassium chlorate, potassium perchlorate, potassium ferricyanide, sodium hypochlorite, and potassium permanganate. Preferably, it is potassium periodate or potassium perchlorate. The small amount of oxidizing agent used can cooperate with the acid to realize the rapid roughening of the metal material through the form of redox reaction.

[0019] The wetting agent is one or more of perfluoroalkyl betaine resistant to strong acids and strong oxidizing agents, preferably perfluorododecyl dimethyl sulfopropyl betaine, perfluorododecyl dimethyl betaine, perfluorododecyl dimethyl sulfopropyl betaine, perfluorododecyl dimethyl hydroxypropyl phosphoric acid ester betaine, perfluorododecyl dimethyl carboxylic acid ester betaine, and perfluorohexadecyl dimethyl hydroxypropyl carboxylic acid ester betaine.

[0020] A preparation method of a roughening solution, which comprises the following specific steps:

[0021] (1) According to the composition of the roughening solution, solvent water is added into the stirring kettle, the stirring is turned on, and the temperature of the stirring kettle is controlled at 20-30℃.

[0022] (2) Along the inner wall of the stirring kettle, strong acid is slowly poured and mixed uniformly until clear;

[0023] (3) Along the inner wall of the stirring kettle, organic acid is slowly added and mixed uniformly until clear;

[0024] (4) Along the inner wall of the stirring kettle, polyamine compound is slowly added and mixed uniformly until clear;

[0025] (5) Along the inner wall of the stirring kettle, oxidizing agent is slowly added and mixed uniformly until clear;

[0026] (6) Along the inner wall of the stirring kettle, wetting agent is slowly added and mixed uniformly until clear;

[0027] In the above preparation steps, the next material can be added only after the uniform mixing until clear.

[0028] The roughening solution of the present application can be used for surface roughening treatment of III-V semiconductor epitaxial layers such as AlGaInP layer, ALGaAs layer, GaAsP layer, GaP layer, GaN layer, etc., to pattern the surface microstructure. Using the roughening solution of the present application can efficiently and high-quality roughen the surface of the semiconductor epitaxial layer at room temperature, accurately control the reaction rate, particle size, etching depth and other micro variables, thereby forming a uniform and fine pyramid structure on the surface of the epitaxial layer to achieve the desired roughening state. A method for using the roughening solution, comprising the following steps:

[0029] (a) Making a mask plate;

[0030] (b) Using the mask plate made in step (a) to perform photolithography on the LED chip to be roughened, and using photoresist to protect the area that does not need to be roughened;

[0031] (c) Performing wet etching on the LED chip treated in step (b); immersing the LED chip to be roughened in the roughening solution of the present application, soaking at room temperature for 100-180s, preferably for 120s-140s, then taking it out and rinsing with deionized water, and blowing dry.

[0032] (d) Removing the photoresist of the LED chip obtained in step (c) and cleaning.

[0033] Compared with the prior art, the application has the beneficial effects that: by compounding inorganic strong acid and organic acid buffer system, the hydrogen ion concentration of the roughening solution is maintained in dynamic balance during the roughening process, so that the reaction rate is stable; further preferably, the strong acid is easily activated with an oxidizing agent, which effectively improves the oxidation of the multi-metal compound, promotes the formation of metal oxide of aluminum gallium indium phosphorus, reduces the reaction activation energy, and enables the roughening reaction to be carried out at room temperature; by adding a plurality of polyamines, the reaction activity factor can be maintained in dynamic balance, avoiding the problem of over-etching caused by local rapid micro-chemical reaction, and avoiding the problem of leakage voltage. At the same time, by adding a perfluorinated surfactant with high stability and low surface tension, the roughening interfacial tension is effectively reduced, the roughening product and bubbles quickly leave the reaction interface, the roughening interface is in a uniform state, the problem of uneven roughening surface is effectively solved, the roughening surface quality is improved, the light output is effectively increased, and the LED light intensity is improved.

[0034] By using the roughening solution of the application, the LED chip can be micro-patterned on the surface at room temperature to form a concave-convex rough surface. Before roughening, the surface of the LED chip presents a regular planar morphology with high light reflectivity; after roughening, the surface presents a uniform fine pyramid morphology, forming a uniform and fine rough surface, which can increase the light absorbance and increase the brightness by more than 40%. The wet etching is easy to operate, has low cost, and the reaction conditions are easy to control at room temperature, which can be applied to industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is an image of the LED chip surface morphology before etching, enlarged 400 times.

[0036] Figure 2 is an image of the LED chip surface morphology after etching using Example 1 of the application, enlarged 400 times.

[0037] Figure 3 is an image of the LED chip surface morphology after etching using Comparative Example 1, enlarged 400 times. DETAILED DESCRIPTION

[0038] The application will be further described below by examples

[0039] Example 1

[0040] A roughening solution, the mass percentage of each component is:

[0041] 10% nitric acid,

[0042] 10% hydrofluoric acid

[0043] 10% citric acid,

[0044] 16% ethylenediamine,

[0045] hydrogen peroxide 4%

[0046] potassium dichromate 5%,

[0047] perfluorododecyl dimethyl sulfonium ethyl sulfonate 0.1%

[0048] the balance being deionized water.

[0049] A preparation method of a roughening solution, comprising the following steps:

[0050] (1) adding deionized water into a stirred tank, and controlling the temperature of the stirred tank at 20-30℃.

[0051] (2) slowly pouring nitric acid and hydrofluoric acid along the inner wall of the stirred tank in sequence, and mixing uniformly until clear;

[0052] (3) slowly adding citric acid along the inner wall of the stirred tank, and mixing uniformly until clear;

[0053] (4) slowly adding ethylenediamine along the inner wall of the stirred tank, and mixing uniformly until clear;

[0054] (5) slowly adding hydrogen peroxide and potassium dichromate along the inner wall of the stirred tank in sequence, and mixing uniformly until clear;

[0055] (6) slowly adding perfluorododecyl dimethyl sulfonium ethyl sulfonate along the inner wall of the stirred tank, and mixing uniformly until clear;

[0056] The use method of the roughening solution of the embodiment is as follows:

[0057] (a) making a mask plate;

[0058] (b) using the mask plate made in step (a) to perform photolithography on the LED chip, and protecting the area without etching with photoresist;

[0059] (c) performing wet roughening on the LED chip treated in step (b): immersing the LED chip to be roughened in the roughening solution, soaking at room temperature for 120s, and then taking it out and rinsing with deionized water, and blowing dry;

[0060] (d) removing photoresist and cleaning, and removing photoresist and cleaning the LED chip obtained in step (c).

[0061] The deionized water in the following table is the balance.

[0062]

[0063]

[0064] Comparative Example 1:

[0065] An LED chip roughening solution, the mass percentage of each component is:

[0066] Nitric acid 20%,

[0067] Hydrogen peroxide 20%

[0068] The balance is deionized water.

[0069] Comparative Example 2:

[0070] A chip roughening solution, the mass percentage of each component is:

[0071] Sulfuric acid 10%,

[0072] Hydrofluoric acid 10%

[0073] Potassium perchlorate 5%,

[0074] The balance is deionized water.

[0075] Table 1 below is the surface flatness of each LED chip after roughening in each example, and the roughening depth, pyramid particle size, whether the photoresist is damaged and the subsequent brightness improvement rate of the LED chip are detected.

[0076] Sample No. Surface flatness Roughening depth / μm Grain size / μm Photoresist damage Brightness improvement rate Example 1 Uniform fine grain 0.9 0.01-0.02 None 48％ Example 2 Uniform fine grain 1.0 0.03-0.06 None 46％ Example 3 Uniform fine grain 0.8 0.03-0.06 None 43％ Example 4 Uniform fine grain 0.8 0.02-0.06 None 45％ Example 5 Uniform fine grain 1.2 0.05-0.08 None 47％ Example 6 Uniform fine grain 1.1 0.05-0.09 None 47％ Comparative Example 1 Severe roughening unevenness 5.2 0.5-5 Yes 0 Comparative Example 2 Severe roughening unevenness 4.0 0.5-4 None 5％

[0077] The roughening in the example is the 5 μm thick AlGaInP film layer deposited on the gallium arsenide substrate.

[0078] In addition, the chip surface flatness in Table 1 is observed under a microscope, as shown in the accompanying drawings, the chip surface roughening is uniform and fine, the absorbance increases, the reflected light decreases, and the microscope photograph shows uniform blackening.

[0079] In addition, the roughening depth in Table 1 is measured by using a scanning electron microscope to measure the difference between the thickness of the AlGaInP film before and after roughening.

[0080] In addition, the particle size in Table 1 is measured by a scanning electron microscope on the surface layer area after roughening, and the size refers to the average distance between the tips of the pyramids.

[0081] In addition, the damage to the photoresist layer is to observe the photoresist film on the chip electrode surface, whether it is damaged by soaking in the roughening solution, and whether the metal electrode is corroded and damaged.

[0082] In addition, the brightness improvement rate refers to the improvement rate of the luminous intensity of the roughened chip relative to the untreated chip under the same conditions, i.e. 20 mA current intensity.

[0083] Comparative conclusion:

[0084] The roughening liquid of the patent application has good surface micro-structuring effect on the AlGaInP epitaxial layer in the LED chip, can form uniform micro-pyramid structure, has moderate roughening depth, does not corrode photoresist, can effectively improve light efficiency, and photoelectric parameters meet the demand, and the preparation of the roughening liquid is simple, and the operation is simple, and has industrial practicability.

[0085] The above is only a few embodiments of the application, and does not limit the application in any form. Although the preferred embodiments are disclosed above, they are not intended to limit the application. Any skilled person in the art can make some changes or modifications to the disclosed technical content without departing from the scope of the technical solution of the application, which are equivalent to equivalent embodiments, and belong to the scope of the technical solution.

Claims

1. An LED chip roughening liquid, characterized by, It comprises the following components and their mass percentages: Inorganic acid 10-20%, Organic acid 5-10%, Polyamine compound 5-20%, Oxidizing agent 0.1-5%, Wetting agent 0.01-1%, The balance is deionized water; The inorganic acid is one or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, and hydrofluoric acid; The organic acid is a pH stabilizer selected from tartaric acid, succinic acid, or citric acid; The polyamine compound is a metal ion complexing agent selected from ethylenediamine or ammonium chloride; The oxidizing agent is hydrogen peroxide with potassium dichromate, potassium periodate with potassium chlorate, potassium periodate with potassium dichromate; The wetting agent is a perfluoroalkyl betaine resistant to strong acids and strong oxidizing agents.

2. The LED chip roughening solution of claim 1, wherein: The inorganic acid is nitric acid and / or hydrofluoric acid.

3. The roughening solution for LED chips according to claim 1, wherein: The mass fraction of hydrochloric acid is 37%, the mass fraction of phosphoric acid is 85%, the mass fraction of sulfuric acid is 98%, the mass fraction of hydrofluoric acid is 40%, and the mass fraction of nitric acid is 30%.

4. The roughening solution for LED chips according to claim 1, wherein: The perfluoroalkyl betaine is one or more of perfluorododecyl dimethyl sulfonethyl betaine, perfluorododecyl dimethyl betaine, perfluorododecyl dimethyl sulfopropyl betaine, perfluorododecyl dimethyl hydroxypropyl phospholipid betaine, perfluorododecyl dimethyl carboxylate betaine, perfluorohexadecyl dimethyl hydroxypropyl carboxylate betaine.

5. The method of claim 1, wherein the roughening solution is prepared by mixing 0.1 to 0.5 wt% of the abrasive particles in 99.5 to 99.9 wt% of the solvent. The specific steps are as follows: (1) According to the composition of the roughening solution, add solvent water into the stirred tank, turn on the stirring, and always control the temperature of the stirred tank at 20-30℃; (2) Pour the inorganic acid along the inner wall of the stirred tank according to the proportion, mix uniformly until clear; (3) Pour the organic acid along the inner wall of the stirred tank according to the proportion, mix uniformly until clear; (4) Pour the polyamine compound along the inner wall of the stirred tank according to the proportion, mix uniformly until clear; (5) Pour the oxidizing agent along the inner wall of the stirred tank according to the proportion, mix uniformly until clear; (6) Pour the wetting agent along the inner wall of the stirred tank according to the proportion, mix uniformly until clear; After the above preparation steps are mixed uniformly until clear, the next material can be added.

6. The use of a roughening solution for an LED chip according to claim 1, wherein: The roughening solution is used for surface roughening treatment of AlGaInP layer, AlGaAs layer, GaAsP layer, GaP layer, GaN layer III-V semiconductor epitaxial layer, and surface micro patterning.

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