Alkaline etching solution and preparation method thereof

Abstract

The present application relates to the field of semiconductor etching solutions and specifically provides an alkaline etching solution and a preparation method thereof. The alkaline etching solution comprises the following components by weight: 40-50% alkali, 3-5% aluminum salt, 1-3% chloride additive, 0.8-1.2% surfactant, and the balance being high-purity water; the chloride additive comprises a chloride salt, and the surfactant comprises a modified polysaccharide. The alkaline etching solution prepared by the present application has the advantages of fast etching speed and good surface quality.

Description

Technical Field

[0001] The present application belongs to the technical field of semiconductor etching solutions, and in particular relates to an alkaline etching solution and a preparation method thereof. Background Art

[0002] With the increasing improvement of industry standards in the field of electronic technology, semiconductor material science and semiconductor manufacturing have flourished in the past few decades. Therefore, it is widely used in the development of various industries to make diodes, integrated circuits, power electronic devices and optoelectronic devices, becoming an indispensable basic material.

[0003] Currently, the application of semiconductor materials is still dependent on device processing, especially for substrate materials, which place high demands on semiconductor quality. Because the substrate surface pattern for device fabrication must meet specific requirements, the requirements for substrate surface etching rate and depth vary across different device fabrication processes. Etching processes are primarily categorized into two types: anisotropic and isotropic, based on the varying etching rates in different directions on the substrate surface. Etching methods are further categorized into dry and wet etching.

[0004] Dry etching uses a plasma generated by glow discharge using etching gases such as CCl₄, Ar, Cl₂, and H₂. It can be categorized into three types: plasma etching, reactive ion etching, and ion beam etching. The main advantages of dry etching include good anisotropy, different material selectivity, process control, good repeatability, and the absence of chemical reagents. However, its disadvantages include expensive equipment, toxic etching gases, lattice damage, rough sidewalls, increased dark current on the device surface, and significant risk. Wet etching uses acidic or alkaline etching solutions composed of HNO₃, C₄H₂O₂, or NaOH to react with the substrate material to remove unwanted surfaces. The main advantages of wet etching include simple equipment, relatively low etching costs, high selectivity, and high repeatability. However, its disadvantages include poor controllability, poor anisotropy, severe substrate side corrosion, and low cleanliness.

[0005] In the fields of wafer manufacturing and microelectronics, especially for etching processes that require high precision and high selectivity, alkaline etching solutions have higher selectivity than acidic etching solutions, can etch materials more accurately, achieve higher etching accuracy, and the waste liquid generated is relatively simple to handle, with less impact on the environment.

[0006] For example, in the etching of InAs semiconductor materials, acidic etchants hinder surface oxidation when treating the InAs surface. Adding an oxidant significantly increases the surface etching rate, but reduces selectivity. The problem with alkaline etchants is their slower etching speed and mass transfer rate. Therefore, how to further improve the etching effect of alkaline etchants is an urgent issue to be addressed. Summary of the Invention

[0007] In view of the above problems, in order to further improve the etching effect of the alkaline etching solution, the present application provides an alkaline etching solution and a preparation method thereof.

[0008] The present application first provides an alkaline etching solution, comprising the following components in mass percentage: 40-50% alkali, 3-5% aluminum salt, 1-3% chloride additive, 0.8-1.2% surfactant, and the balance being high-purity water; the chloride additive comprises chloride salt, and the surfactant comprises modified polysaccharide.

[0009] Furthermore, the chloride additive consists of potassium chloride and hydrogen peroxide in a mass ratio of 1:1.

[0010] Furthermore, the base is composed of potassium hydroxide and quaternary ammonium hydroxide in a mass ratio of 1:0.15.

[0011] Furthermore, the aluminum salt is aluminum sulfate.

[0012] Furthermore, in the surfactant, the modified polysaccharide is prepared by the following preparation method:

[0013] 1) Deionized water and polysaccharide are mixed evenly, and then protease is added to perform a deproteinization reaction. The temperature is then raised to inactivate the protease. After cooling, the mixture is centrifuged to remove the precipitate to obtain a pre-solution.

[0014] 2) Add phenylalanine, aldehyde compound, and potassium hydroxide to anhydrous ethanol, mix well, react at 55-65°C, and rotary evaporate to obtain an intermediate material;

[0015] 3) Add the intermediate material to the pre-liquid, mix well, then add the cyclodextrin derivative, stir at room temperature, and then dry at 40-50°C to obtain the modified polysaccharide.

[0016] Furthermore, in step 1), the polysaccharide is guar gum;

[0017] And / or, in step 1), the mass ratio of deionized water to polysaccharide is 1:0.15;

[0018] And / or, in step 1), the proteolytic enzyme is papain with an activity of 5,000,000 PU / g;

[0019] And / or, in step 1), the reaction temperature of the deproteinization reaction is 50-65°C;

[0020] And / or, in step 1), the inactivation temperature for inactivating the protease is 80-100°C.

[0021] Furthermore, in step 2), the aldehyde compound is citral;

[0022] And / or, in step 2), the molar ratio of phenylalanine to the aldehyde compound is 1:1.6.

[0023] Furthermore, in step 3), the mass ratio of the pre-pad to the intermediate material is 1:0.65;

[0024] And / or, in step 3), the amount of the cyclodextrin derivative added accounts for 10% of the mass of the intermediate material;

[0025] And / or, in step 3), the cyclodextrin derivative is aminocyclodextrin.

[0026] Furthermore, the surfactant is composed of modified polysaccharide and hexadecyltrimethylammonium chloride in a mass ratio of 1:0.1.

[0027] The present application also provides a method for preparing an alkaline etching solution, comprising the following steps: uniformly mixing alkali, aluminum salt, chloride additive, surfactant, and high-purity water to obtain the obtained solution.

[0028] Compared with the prior art, this application has the following beneficial effects:

[0029] The present application adopts alkali and aluminum salt to construct a basic etching system, which improves the etching speed of the system to a certain extent. In addition, the present application introduces a chloride additive and a surfactant into the basic etching system, wherein the chloride salt in the chloride additive can introduce a certain amount of chloride ions to increase the etching rate; the modified polysaccharide in the surfactant can effectively complex the oxide to generate a soluble substance that dissolves in the etching solution, thereby improving the etching effect. In addition, the modified polysaccharide can also inhibit the generation of surface defects during the etching process, reduce the content of oxygen atoms on the surface after etching, maintain the ratio of In atoms and As atoms on the surface of the substrate stable, so that the surface of the InAs substrate after etching is smooth, and there are no crystal defects such as etching damage and microcracks, which can effectively extend the service life and process parameters of the InAs device. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of etching rate test data of alkaline etching solution for Examples 1-2 and Control Groups 1-2 of the present application;

[0031] Figure 2 Schematic diagram of the SEM etching surface of the samples of Examples 1-2 and Control Groups 1-2 of the present application;

[0032] Figure 3 Schematic diagram of the AFM etching surface of the samples of Examples 1-2 and Control Group 1-2 of the present application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] After a lot of experimental research, this application optimizes the traditional alkaline etching solution and constructs a composite etching system, which improves the etching rate to a certain extent while maintaining a better surface etching effect.

[0035] The present application provides an alkaline etching solution comprising the following components in mass percentage: 40-50% alkali, 3-5% aluminum salt, 1-3% chloride additive, 0.8-1.2% surfactant, and the balance being high-purity water; the chloride additive comprises chloride salt, and the surfactant comprises modified polysaccharide.

[0036] Furthermore, in the chloride additive, the chloride salt is one or more of ammonium chloride, sodium chloride, and potassium chloride;

[0037] And / or, the chloride additive further includes one of hydrogen peroxide, sodium hypochlorite, and potassium permanganate.

[0038] Furthermore, the base is one or more of ammonia water, sodium hydroxide, potassium hydroxide, quaternary ammonium base, and quaternary phosphate base.

[0039] Furthermore, the aluminum salt is one or more of aluminum chloride, aluminum sulfate, aluminum nitrate, and aluminum acetate.

[0040] In some specific embodiments, the chloride salt in the chloride additive is ammonium chloride, sodium chloride, or potassium chloride. Generally, when the chloride salt is potassium chloride, better experimental results can be obtained.

[0041] In some specific embodiments, the chloride additive may further include hydrogen peroxide, sodium hypochlorite, or potassium permanganate. More preferably, the chloride additive is composed of potassium chloride and hydrogen peroxide. More preferably, the chloride additive is composed of potassium chloride and hydrogen peroxide in a mass ratio of 1:(1-1.2). Generally, when the chloride additive is composed of potassium chloride and hydrogen peroxide in a mass ratio of 1:1, better experimental results can be obtained.

[0042] In some specific embodiments, under normal circumstances, the alkaline etching solution includes the following components in mass percentage: 45% alkali, 5% aluminum salt, 3% chloride additive, 1% surfactant, and the balance is high-purity water. In this case, better experimental results can be obtained.

[0043] In some specific embodiments, the alkali can be one or more of ammoniacal liquor, sodium hydroxide, potassium hydroxide, quaternary ammonium base, and quaternary phosphate base. More preferably, the alkali is composed of potassium hydroxide and quaternary ammonium base in a mass ratio of 1: (0.1-0.2). More preferably, under normal circumstances, when the alkali is composed of potassium hydroxide and quaternary ammonium base in a mass ratio of 1: 0.15, better experimental results can be obtained. More preferably, the quaternary ammonium base is one or more of tetramethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Under normal circumstances, the effect is better when the quaternary ammonium base is tetrabutylammonium hydroxide.

[0044] In some specific embodiments, generally, the experimental effect is better when the aluminum salt is aluminum sulfate.

[0045] Furthermore, in the surfactant, the modified polysaccharide is prepared by the following preparation method:

[0046] 1) Deionized water and polysaccharide are mixed evenly, and then protease is added to perform a deproteinization reaction. The temperature is then raised to inactivate the protease. After cooling, the mixture is centrifuged to remove the precipitate to obtain a pre-solution.

[0047] 2) Add phenylalanine, aldehyde compound, and potassium hydroxide to anhydrous ethanol, mix well, react at 55-65°C, and rotary evaporate to obtain an intermediate material;

[0048] 3) Add the intermediate material to the pre-liquid, mix well, then add the cyclodextrin derivative, stir at room temperature, and then dry at 40-50°C to obtain the modified polysaccharide.

[0049] Furthermore, in step 1), the polysaccharide is one or more of hyaluronic acid, chondroitin sulfate, flaxseed gum, and guar gum;

[0050] And / or, in step 1), the mass ratio of deionized water to polysaccharide is 1:(0.1-0.2);

[0051] And / or, in step 1), the protease is selected from proteolytic enzymes;

[0052] And / or, in step 1), the reaction temperature of the deproteinization reaction is 50-65°C;

[0053] And / or, in step 1), the inactivation temperature for inactivating the protease is 80-100°C.

[0054] In some specific embodiments, generally, in step 1), better experimental results can be obtained when the polysaccharide is guar gum.

[0055] In some specific embodiments, in step 1), the mass ratio of deionized water to polysaccharide can be 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, or 1:0.2. Generally, a mass ratio of deionized water to polysaccharide of 1:0.15 can achieve better experimental results.

[0056] In some embodiments, in step 1), the proteolytic enzyme is a plant protease. More preferably, the proteolytic enzyme is papain with an activity of 5,000,000 PU / g.

[0057] In some specific embodiments, in step 1), the reaction temperature of the deproteinization reaction can be 50° C., 55° C., 60° C., or 65° C. Generally, a deproteinization reaction temperature of 55° C. achieves better results.

[0058] In some embodiments, in step 1), the inactivation temperature for inactivating the protease may be 80° C., 85° C., 90° C., 95° C., or 100° C. Generally, an inactivation temperature of 95° C. is more effective.

[0059] Furthermore, in step 2), the aldehyde compound is one of citral, syringaldehyde, and cinnamaldehyde;

[0060] And / or, in step 2), the molar ratio of phenylalanine to the aldehyde compound is 1:(1.5-2).

[0061] Furthermore, in step 3), the mass ratio of the pre-pad to the intermediate material is 1:(0.5-0.75);

[0062] And / or, in step 3), the amount of the cyclodextrin derivative added is 5-10% of the mass of the intermediate material;

[0063] And / or, in step 3), the cyclodextrin derivative is one or more of hydroxypropyl cyclodextrin, sulfobutyl cyclodextrin, glucosyl cyclodextrin, and amino cyclodextrin.

[0064] Furthermore, the surfactant also includes one of polyethylene glycol, cetyltrimethylammonium chloride, and lauryl alcohol polyoxyethylene ether.

[0065] In some specific embodiments, in step 2), the effect is better when the aldehyde compound is citral.

[0066] In some specific embodiments, in step 2), the molar ratio of phenylalanine to the aldehyde compound can be 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2. Generally, a molar ratio of phenylalanine to the aldehyde compound of 1:1.6 is more effective.

[0067] In some specific embodiments, in step 3), the mass ratio of the prepad to the intermediate material can be 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, or 1:0.75. Generally, a mass ratio of the prepad to the intermediate material of 1:0.65 achieves better results.

[0068] In some specific embodiments, in step 3), the amount of the cyclodextrin derivative added can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% of the weight of the intermediate material. Generally, better experimental results can be achieved when the cyclodextrin derivative is added in an amount of 10% of the weight of the intermediate material.

[0069] In some specific embodiments, generally, better experimental results can be obtained when the cyclodextrin derivative is aminocyclodextrin.

[0070] In some specific embodiments, the surfactant further comprises cetyltrimethylammonium chloride. More preferably, the surfactant comprises the modified polysaccharide and cetyltrimethylammonium chloride in a mass ratio of 1:(0.05-0.1). More preferably, the surfactant comprises the modified polysaccharide and cetyltrimethylammonium chloride in a mass ratio of 1:0.1.

[0071] Example 1: The alkaline etching solution of this example comprises the following components in percentage by mass: 45% alkali, 5% aluminum salt, 3% chloride additive, 1% surfactant, and the balance being high-purity water.

[0072] The base is composed of potassium hydroxide and quaternary ammonium hydroxide in a mass ratio of 1:0.15. The aluminum salt is aluminum sulfate. The chloride additive is composed of potassium chloride and hydrogen peroxide in a mass ratio of 1:1. The surfactant is composed of carboxymethyl chitosan and hexadecyltrimethylammonium chloride in a mass ratio of 1:0.1.

[0073] The preparation method of the alkaline etching solution of this embodiment comprises the following steps:

[0074] Raw material purification: The liquid components of the alkaline etching solution are subjected to a purification membrane filtration operation to obtain the purified raw materials of each component after passing through the membrane.

[0075] Mixing preparation: The purified alkali solution, aluminum salt, chloride additive, surfactant and high-purity water are mixed in proportion to prepare an alkaline etching solution.

[0076] Testing and storage: Test the pH value of the alkaline etching solution to ensure that it meets the standards. Finally, fill the qualified etching solution into a corrosion-resistant container and store it in a sealed container.

[0077] Example 2: The alkaline etching solution of this example comprises the following components in percentage by mass: 45% alkali, 5% aluminum salt, 3% chloride additive, 1% surfactant, and the balance being high-purity water.

[0078] The base comprises potassium hydroxide and quaternary ammonium hydroxide in a mass ratio of 1:0.15. The aluminum salt is aluminum sulfate. The chloride additive comprises potassium chloride and hydrogen peroxide in a mass ratio of 1:1. The surfactant comprises modified polysaccharide and hexadecyltrimethylammonium chloride in a mass ratio of 1:0.1.

[0079] The modified polysaccharide of this embodiment was prepared by the following preparation method:

[0080] 1) Deionized water and guar gum were placed in a stirred tank at a mass ratio of 1:0.15 and mixed at 350 rpm. After vacuum degassing, papain (activity 5,000,000 PU / g) was added. Deproteinization was carried out at 55°C. The temperature was then raised to 95°C to inactivate the protease. After cooling, the mixture was centrifuged to remove the precipitate to obtain a pre-paste.

[0081] 2) Add phenylalanine, citral, and potassium hydroxide to anhydrous ethanol, controlling the molar ratio of phenylalanine, citral, and potassium hydroxide to be 1:1.6:1, mix well, react at 60°C, and rotary evaporate to obtain an intermediate material;

[0082] 3) Add the pre-liquid and the intermediate material into a reactor equipped with a stirrer and a thermometer, control the mass ratio of the pre-liquid to the intermediate material to be 1:0.65, mix well, add aminocyclodextrin accounting for 10% of the mass of the intermediate material, stir at room temperature, and then dry at 50°C to obtain a modified polysaccharide.

[0083] The preparation method of the alkaline etching solution of this embodiment comprises the following steps:

[0084] Raw material purification: The liquid components of the alkaline etching solution are subjected to a purification membrane filtration operation to obtain the purified raw materials of each component after passing through the membrane.

[0085] Mixing preparation: The purified alkali solution, aluminum salt, chloride additive, surfactant and high-purity water are mixed in proportion to prepare an alkaline etching solution.

[0086] Testing and storage: Test the pH value of the alkaline etching solution to ensure that it meets the standards. Finally, fill the qualified etching solution into a corrosion-resistant container and store it in a sealed container.

[0087] Control group 1: The alkaline etching solution of this control group and this embodiment includes the following components in percentage by mass: 45% alkali, 5% aluminum salt, 1.5% hydrogen peroxide, 1% surfactant, and the balance is high-purity water.

[0088] The base is composed of potassium hydroxide and quaternary ammonium hydroxide in a mass ratio of 1:0.15. The aluminum salt is aluminum sulfate. The surfactant is composed of modified polysaccharide and hexadecyltrimethylammonium chloride in a mass ratio of 1:0.1.

[0089] The modified polysaccharide in this control group was prepared by the following preparation method:

[0090] 1) Deionized water and guar gum were placed in a stirred tank at a mass ratio of 1:0.15 and mixed at 350 rpm. After vacuum degassing, papain (activity 5,000,000 PU / g) was added. Deproteinization was carried out at 55°C. The temperature was then raised to 95°C to inactivate the protease. After cooling, the mixture was centrifuged to remove the precipitate to obtain a pre-paste.

[0091] 2) Add phenylalanine, citral, and potassium hydroxide to anhydrous ethanol, controlling the molar ratio of phenylalanine, citral, and potassium hydroxide to be 1:1.6:1, mix well, react at 60°C, and rotary evaporate to obtain an intermediate material;

[0092] 3) Add the pre-liquid and the intermediate material into a reactor equipped with a stirrer and a thermometer, control the mass ratio of the pre-liquid to the intermediate material to be 1:0.65, mix well, add aminocyclodextrin accounting for 10% of the mass of the intermediate material, stir at room temperature, and then dry at 50°C to obtain a modified polysaccharide.

[0093] The preparation method of the alkaline etching solution of this control group comprises the following steps:

[0094] Raw material purification: The liquid components of the alkaline etching solution are subjected to a purification membrane filtration operation to obtain the purified raw materials of each component after passing through the membrane.

[0095] Mixing preparation: Purified alkali solution, aluminum salt, hydrogen peroxide, surfactant and high-purity water are mixed in proportion to prepare an alkaline etching solution.

[0096] Testing and storage: Test the pH value of the alkaline etching solution to ensure that it meets the standards. Finally, fill the qualified etching solution into a corrosion-resistant container and store it in a sealed container.

[0097] Control group 2: The alkaline etching solution of this control group includes the following components in mass percentage: 45% alkali, 5% aluminum salt, 2% hydrogen peroxide, and the balance is high-purity water.

[0098] The base is composed of potassium hydroxide and quaternary ammonium hydroxide in a mass ratio of 1:0.15, and the aluminum salt is aluminum sulfate.

[0099] The preparation method of the alkaline etching solution of this control group comprises the following steps:

[0100] Raw material purification: The liquid components of the alkaline etching solution are subjected to a purification membrane filtration operation to obtain the purified raw materials of each component after passing through the membrane.

[0101] Mixing preparation: Purified alkali solution, aluminum salt, hydrogen peroxide and high-purity water are mixed in proportion to prepare an alkaline etching solution.

[0102] Testing and storage: Test the pH value of the alkaline etching solution to ensure that it meets the standards. Finally, fill the qualified etching solution into a corrosion-resistant container and store it in a sealed container.

[0103] Performance testing

[0104] 1. A 500±25μm thick, 5mm×5mm size n-type InAs (100) polished semiconductor wafer was used as the test material. The InAs sample was ultra-clearly cleaned with acetone and anhydrous ethanol, dried under nitrogen atmosphere, and one side of the sample was masked with paraffin. Then, it was immersed in the alkaline etching solution of Example 1-2 and Control Group 1-2, and after etching for a certain period of time, it was taken out and washed with acetone and deionized water in turn, dried under nitrogen, and the etching speed was tested with a high-precision vernier caliper. The etching speed = InAs sample removal thickness / etching time. The results are as follows. Figure 1 As shown, it can be seen that the alkaline etching solution of the present application has a certain degree of improvement in etching speed, and the increase in etching speed has no significant impact on the etching quality.

[0105] 2. Use scanning electron microscopy to analyze the surface morphology of the InAs sample after etching to observe whether there are etching pits, microcracks, etc. The results are as follows: Figure 2 The surface roughness was tested by atomic force microscopy, and the results were as follows. Figure 3 As shown, it can be seen that the surface etching state of the alkaline etching solution sample of the present application is good, the surface is uniform and flat, and the quality is good.

[0106] Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present invention.

Claims

1. An alkaline etching solution, characterized in that: The invention comprises the following components in percentage by mass: 40-50% alkali, 3-5% aluminum salt, 1-3% chloride additive, 0.8-1.2% surfactant, and the balance is high-purity water; the alkali is one or more of ammonia water, sodium hydroxide, potassium hydroxide, quaternary ammonium base, and quaternary phosphate base; the chloride additive includes chloride salt, and the surfactant includes modified polysaccharide; the modified polysaccharide is prepared by the following preparation method: 1) Deionized water and polysaccharide are mixed evenly, and then protease is added to perform a deproteinization reaction. The temperature is then raised to inactivate the protease. After cooling, the solution is centrifuged to remove the precipitate to obtain a pre-fluid. The mass ratio of deionized water to polysaccharide is 1:(0.1-0.2). Protease is a protein hydrolytic enzyme. 2) Add phenylalanine, aldehyde compound, and potassium hydroxide to anhydrous ethanol, mix well, react at 55-65°C, and rotary evaporate to obtain an intermediate material; the molar ratio of phenylalanine to aldehyde compound is 1:(1.5-2); 3) Add the intermediate material to the pre-liquid, mix well, then add the cyclodextrin derivative, stir at room temperature, and then dry at 40-50°C to obtain a modified polysaccharide; the mass ratio of the pre-liquid to the intermediate material is 1:(0.5-0.75); the amount of the cyclodextrin derivative added accounts for 5-10% of the mass of the intermediate material.

2. The alkaline etching solution according to claim 1, wherein: The chloride additive consists of potassium chloride and hydrogen peroxide in a mass ratio of 1:

1.

3. The alkaline etching solution according to claim 1, wherein: The alkali is composed of potassium hydroxide and quaternary ammonium hydroxide in a mass ratio of 1:0.

15.

4. The alkaline etching solution according to claim 1, wherein: The aluminum salt is aluminum sulfate.

5. The alkaline etching solution according to claim 1, wherein: In the step 1), the polysaccharide is guar gum; And / or, in step 1), the mass ratio of deionized water to polysaccharide is 1:0.15; And / or, in step 1), the proteolytic enzyme is papain with an activity of 5,000,000 PU / g; And / or, in step 1), the reaction temperature of the deproteinization reaction is 50-65°C; And / or, in step 1), the inactivation temperature for inactivating the protease is 80-100°C.

6. The alkaline etching solution according to claim 1, wherein: In the step 2), the aldehyde compound is citral; And / or, in step 2), the molar ratio of phenylalanine to the aldehyde compound is 1:1.

6.

7. The alkaline etching solution according to claim 1, wherein: In step 3), the mass ratio of the pre-pad liquid to the intermediate material is 1:0.65; And / or, in step 3), the amount of the cyclodextrin derivative added accounts for 10% of the mass of the intermediate material; And / or, in step 3), the cyclodextrin derivative is aminocyclodextrin.

8. The alkaline etching solution according to claim 1, wherein: The surfactant consists of modified polysaccharide and hexadecyltrimethylammonium chloride in a mass ratio of 1:0.

1.

9. A method for preparing the alkaline etching solution as claimed in claim 1, characterized in that: The method comprises the following steps: uniformly mixing alkali, aluminum salt, chloride additive, surfactant and high-purity water.

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