Metal etching liquid auxiliary agent and preparation method and application thereof

Abstract

The invention discloses a metal etching liquid auxiliary agent and a preparation method and application thereof, and relates to the technical field of metal surface treatment.The metal etching liquid auxiliary agent comprises, by mass, 0%-90% of salt, 0%-90% of solvent, 0%-30% of solvent and the balance water. 0% to 90% of organic matter; 0% to 90% of a complexing agent; and the balance of water. Wherein the total mass ratio of the salt, the organic matter and the complexing agent is greater than 10%. Compared with the prior art, the additive disclosed by the invention has the beneficial effects that the additive disclosed by the invention realizes cross-metal high aspect ratio etching through a salt-organic matter-complexing agent ternary synergistic mechanism, and the same additive is adaptive to three metal systems of titanium, steel and aluminum, so that the complexity of a customer supply chain is reduced; the high ion strength is maintained through the salt, the etching agent is promoted to diffuse to a reaction interface, the etching rate is improved, meanwhile, the complexing agent is chelated with Ti < 4 + > / Fe < 3 + > / Al < 3 + > in real time, generation of a passivation layer is prevented, organic matter adsorption is prevented, a molecular barrier is formed, lateral corrosion is inhibited, and the etching process is optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal surface treatment, in particular to a metal etching liquid additive, a preparation method and application thereof. BACKGROUND

[0002] Metal etching technology is a key process in the fields of microelectronics, aerospace, medical devices, etc. The current mainstream etching liquid has the core defect of low aspect ratio, which seriously restricts the manufacturing of high-precision devices. For example, when etching titanium with the commonly used nitric acid / hydrofluoric acid system (HNO3 / HF), the byproduct TiF4 accumulates to form a passivation layer, resulting in attenuation of the longitudinal etching rate. At the same time, the strong isotropic corrosion of HF causes lateral drilling, limiting the aspect ratio to below 0.5. The semiconductor industry requires a titanium micro-channel structure with an aspect ratio of ≥0.6, which cannot be met by existing technologies. SUMMARY

[0003] The present application aims to provide a metal etching liquid additive, a preparation method and application thereof, which can solve the technical problems of low aspect ratio (≤0.5), poor etching uniformity, and serious intergranular corrosion in existing metal etching processes.

[0004] To solve the above technical problems, the present application adopts the following technical solutions: A metal etching liquid additive, comprising the following components in mass percentage: Salt: 0% to 90%; Organic matter: 0% to 90%; Complexing agent: 0% to 90%; Water: balance; Wherein the total mass percentage of the salt, organic matter and complexing agent is greater than 10%.

[0005] Preferably, the salt is an inorganic electrolyte, selected from at least one of sodium nitrate, potassium sulfate, lithium chloride, iron sulfate, potassium chloride, aluminum chloride, magnesium sulfate, ferric chloride, magnesium chloride, ammonium chloride, copper sulfate, potassium aluminum sulfate, ammonium fluoride, etc. The organic matter is a surfactant, selected from at least one of pyridine derivatives, quaternary ammonium salts, and polyethylene glycol compounds. The complexing agent is a polydentate ligand, selected from at least one of citric acid, ethylenediaminetetraacetic acid (EDTA), tartaric acid, and oxalic acid.

[0006] Preferably, the mass percentage of each component is: Salt: 20%-70%; Organic matter: 10%-60%; Complexing agent: 5%-40%; Water: 10%-50%.

[0007] Preferably, the salt is a mixture of sodium nitrate and ammonium fluoride, with a mass ratio of 1:1 to 3:1. The organic matter is dodecylpyridine bromide. The complexing agent is a mixture of citric acid and disodium EDTA, with a mass ratio of 2:1 to 4:1.

[0008] Preferably, a preparation method of a metal etching liquid additive includes the following steps: S1. Grinding the salt component to a particle size of ≤50 μm and dissolving it in warm water at 30-40°C; S2. Adding the complexing agent to the solution obtained in step S1 and stirring until complete dissolution; S3. Slowly adding the organic matter component to the solution obtained in step S2, controlling the addition rate to ≤5 g / min; S4. Stirring the mixture at a speed of 300-800 rpm for 30-60 minutes; S5. Filtering out the undissolved impurities and adjusting the pH of the filtrate to 2.0-6.0.

[0009] Preferably, sulfuric acid or sodium hydroxide is used to adjust the pH in step S5, with a temperature control of 25±5°C.

[0010] Preferably, the application of a metal etching liquid additive in improving the aspect ratio of titanium etching: The additive is added to a fluorine-containing base etching liquid at a volume ratio of 1:20 to 1:5, and the base etching liquid is a mixture of hydrofluoric acid and nitric acid, with an HF concentration of 3-10 wt% and an HNO3 concentration of 15-40 wt%.

[0011] Preferably, the etching process parameters include: Etching temperature: 20-50°C; Etching time: 5-30 minutes; Stirring condition: ultrasonic oscillation or mechanical stirring.

[0012] Preferably, the additive improves the aspect ratio of titanium etching to 0.6-0.9.

[0013] Preferably, the application of a metal etching liquid additive in improving the aspect ratio of steel or aluminum etching: For steel etching: the additive is added to a base etching liquid containing ferric chloride at a volume ratio of 1:15 to 1:8, with an FeCl3 concentration of 20-40 wt%, an etching temperature of 30-60°C, and an etching aspect ratio of 0.65-0.85; For aluminum etching: the additive is added to a base etching liquid containing phosphoric acid at a volume ratio of 1:25 to 1:10, with an H3PO4 concentration of 35-70 wt%, an etching temperature of 40-80°C, and an etching aspect ratio of 0.70-0.90.

[0014] Compared with the prior art, the application has the beneficial effects that: The auxiliary agent of the application realizes high aspect ratio etching across metals through a ternary synergistic mechanism of salt-organic-complexing agent, and is suitable for three metal systems of titanium, steel and aluminum, thereby reducing the complexity of customer supply chain. The salt maintains high ionic strength, promotes diffusion of the etchant to the reaction interface, and improves the etching rate, while the complexing agent chelates Ti 4+ / Fe 3+ / Al 3+ in real time to prevent the formation of a passivation layer, and the organic matter adsorbs to form a molecular barrier to inhibit lateral corrosion and optimize the etching process. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 The process flow chart of the preparation method of the metal etching liquid auxiliary agent of the application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the application will be described clearly and completely in the following with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only some embodiments of the application, not all embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0018] The application provides a metal etching liquid auxiliary agent, which comprises four types of components: salt, organic matter, complexing agent and water. The total content of the salt, organic matter and complexing agent must be greater than 10%, which is the minimum threshold to ensure the activity of the auxiliary agent. If the total content of the three is less than 10% (for example, salt 5% + organic matter 3% + complexing agent 1% + water 91%), the aspect ratio cannot be effectively improved.

[0019] In the implementation, a single component can be zero, for example: Scheme A: salt 85% + water 15%, complexing agent and organic matter are zero, suitable for etching systems with high ionic strength requirements; Scheme B: organic matter 70% + complexing agent 20% + water 10%, salt is zero, suitable for scenarios where lateral etching is dominant.

[0020] Further, the salt component must be selected from water-soluble inorganic electrolytes. The organic component preferably uses surfactants containing polar groups, such as pyridine derivatives (e.g., dodecylpyridine bromide, which adsorbs on the metal surface through the pyridine ring to form a molecular barrier); quaternary ammonium salts (e.g., cetyltrimethylammonium chloride, which reduces surface tension); polyethylene glycols (e.g., PEG-400, which regulates solution viscosity); and the like. The complexing agent component needs to select polydentate ligands, ethylenediaminetetraacetic acid (EDTA) has the strongest chelating ability for titanium ions; citric acid has both chelating and pH buffering functions; tartaric acid is suitable for acidic etching systems.

[0021] Further, the salt component must be selected from water-soluble inorganic electrolytes. The organic component preferably uses surfactants containing polar groups, such as pyridine derivatives (e.g., dodecylpyridine bromide, which adsorbs on the metal surface through the pyridine ring to form a molecular barrier); quaternary ammonium salts (e.g., cetyltrimethylammonium chloride, which reduces surface tension); polyethylene glycols (e.g., PEG-400, which regulates solution viscosity); and the like. The complexing agent component needs to select polydentate ligands, ethylenediaminetetraacetic acid (EDTA) has the strongest chelating ability for titanium ions; citric acid has both chelating and pH buffering functions; tartaric acid is suitable for acidic etching systems.

[0022] The preferred auxiliary formulation is as follows: Salt component: sodium nitrate and ammonium fluoride are compounded in a mass ratio of 2:1, with sodium nitrate accounting for 30% and ammonium fluoride accounting for 15%. Sodium nitrate provides a uniform conductive environment, and the fluorine ions produced by the dissociation of ammonium fluoride enhance the activity of the etchant.

[0023] Organic component: dodecylpyridine bromide accounts for 18%. Its pyridine ring adsorbs on the titanium surface, and the alkyl chain forms a hydrophobic barrier to inhibit lateral drilling.

[0024] Complexing agent component: citric acid and disodium EDTA are compounded in a mass ratio of 3:1, with citric acid accounting for 9% and disodium EDTA accounting for 3%. Citric acid rapidly chelates the initially generated metal ions, and EDTA provides long-term stable chelating ability.

[0025] Water: the balance of 25% is used to dissolve the components and adjust the viscosity.

[0026] The combination achieves a depth-to-width ratio of 0.86 in titanium etching, and the solution stability is up to 6 months without precipitation.

[0027] As shown in Figure 1 A method for preparing a metal etching solution auxiliary agent, comprising the following steps: S1. Raw material pretreatment: The salt component needs to be ground to a particle size of ≤50 μm in advance. A ball mill is used, with zirconia balls, a rotation speed of 200 rpm, and processing for 30 minutes, and a 400-mesh sieve. If the particle size is >50 μm, the dissolution time is extended to more than 2 hours, and the probability of clogging the filter membrane increases by 80%.

[0028] S2. Dissolution and mixing: Add the pretreated salts into 40°C warm water, stir until completely dissolved, 800 rpm for 10 minutes. Then add the complexing agent components, keep stirring until the solution is clear. If the complexing agent is solid, it needs to be dissolved in a small amount of warm water in advance. The organic components need to be added slowly at a rate of ≤5 g / min. Too fast addition will cause the quaternary ammonium salts to flocculate locally, forming irreversible floc.

[0029] S3. Homogenization: Transfer the mixed solution to a high-speed disperser and stir at 500 rpm for 45 minutes. The stirring paddle is a double-layer inclined-blade turbine type, ensuring that the vortex depth reaches 2 / 3 of the container height. After stirring, the solution should be a uniform transparent liquid with no visible particles.

[0030] S4. Post-treatment: First, filter out impurities through a 0.45 μm microporous filter membrane, then adjust the pH to 3.5 ± 0.5 using sulfuric acid and sodium hydroxide.

[0031] Example One: Application of metal etching liquid additives in titanium etching Base solution: hydrofluoric acid (HF) concentration 5 ± 0.5 wt%, nitric acid (HNO3) concentration 25 ± 2 wt%.

[0032] Additive formula: sodium nitrate 30%, ammonium fluoride 15%, dodecylpyridine bromide 18%, citric acid 9%, EDTA disodium salt 3%, water 25%.

[0033] Additive preparation: grind the salts to 40 μm, dissolve in 40°C water; add citric acid and EDTA; add the organic components at a rate of 4 g / min; stir at 500 rpm for 45 minutes; adjust the pH to 3.5 after filtration.

[0034] Application: add to the 5% HF + 25% HNO3 etching liquid at a volume ratio of 1:10, ultrasonic treatment at 35°C for 15 minutes. The titanium etching temperature is controlled at 35 ± 2°C, less than 30°C, the rate decreases by 40%; greater than 40°C, accelerates HF volatilization and pollutes the environment; time 10-20 minutes, monitor the depth every 5 minutes to avoid over-etching.

[0035] The results show that the aspect ratio is 0.86 ± 0.03 (cross-section test and Keen test).

[0036] Example Two: Application of metal etching liquid additives in steel etching Base solution: ferric chloride (FeCl3) solution concentration 30 ± 3 wt%. Concentration <20% etching rate is too slow; >40% causes high viscosity and poor leveling.

[0037] Additive: same as example one.

[0038] Application: Additive and base solution in 1:10 volume ratio. Steel etching temperature control at 45±5℃, stainless steel passivation layer breaking needs higher activation energy, but >60℃ aggravates intergranular corrosion, mixed in the form of air bubbles, mixing time 2h.

[0039] The results show that the aspect ratio reaches 0.81.

[0040] Example three: application of metal etching solution additive in aluminum etching Base solution: phosphoric acid (H3PO4) concentration 50±5wt%, add 5% acetic acid to enhance the leveling property. Phosphoric acid concentration <35% the oxide layer (Al2O3) is not fully dissolved; >70% leads to high viscosity.

[0041] Additive formula adjustment: sodium nitrate 20%, PEG-400 25%, tartaric acid 15%, water 40%, suitable for non-stirring environment.

[0042] Application: Additive and base solution in 1:18 volume ratio. Solute and heat exchange need to be carried out in the form of air bubbles or tank solution circulation, temperature 65±5℃, aspect ratio still reaches 0.85, surface without residue, etching uniformity deviation ≤3%, this feature greatly simplifies the equipment requirements.

[0043] The additive of the present application realizes high aspect ratio etching across metals through the ternary synergistic mechanism of salt-organic matter-complexing agent, and the same additive is suitable for titanium, steel and aluminum three metal systems, reducing the complexity of customer supply chain; Through salt to maintain high ionic strength, promote the diffusion of etchant to the reaction interface, improve the etching rate, while the complexing agent chelates Ti 4+ / Fe 3+ / Al 3+ in real time, prevent the formation of passivation layer, organic matter adsorption forms a molecular barrier to inhibit lateral corrosion, optimize the etching process.

[0044] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A metal etching solution additive, characterized in that: It contains the following components by mass percentage: Salt content: 0% to 90%; Organic matter: 0% to 90%; Complexing agents: 0% to 90%; Water: Balance; The total mass percentage of the salts, organic matter, and complexing agents is greater than 10%.

2. The metal etching solution additive as described in claim 1, characterized in that: The salts are inorganic electrolytes selected from at least one of sodium nitrate, potassium sulfate, lithium chloride, ferric sulfate, potassium chloride, aluminum chloride, magnesium sulfate, ferric chloride, magnesium chloride, ammonium chloride, copper sulfate, potassium aluminum sulfate, and ammonium fluoride. The organic compound is a surfactant, selected from at least one of pyridine derivatives, quaternary ammonium salts, and polyethylene glycol compounds; The complexing agent is a multidentate ligand selected from at least one of citric acid, ethylenediaminetetraacetic acid (EDTA), tartaric acid, and oxalic acid.

3. The metal etching solution additive as described in claim 2, characterized in that: The mass percentage of each component is as follows: Salt content: 20%-70%; Organic matter: 10%-60%; Complexing agents: 5%-40%; Water: 10%-50%.

4. The metal etching solution additive as described in claim 3, characterized in that: The salt is a mixture of sodium nitrate and ammonium fluoride in a mass ratio of 1:1 to 3:1; The organic compound is dodecylpyridine bromide; The complexing agent is a mixture of citric acid and disodium EDTA in a mass ratio of 2:1 to 4:

1.

5. A method for preparing a metal etching solution additive as described in any one of claims 1-4, characterized in that: Includes the following steps: S1. Grind the salt components to a particle size ≤50μm and dissolve them in warm water at 30-40℃; S2. Add the complexing agent to the solution obtained in step S1 and stir until completely dissolved; S3. Slowly add the organic components to the solution obtained in step S2, controlling the addition rate to ≤5g / min; S4. Stir the mixture at 300-800 rpm for 30-60 minutes; S5. Filter to remove undissolved impurities and adjust the pH of the filtrate to 2.0-6.

0.

6. The method for preparing the metal etching solution additive as described in claim 5, characterized in that: Step S5 involves adjusting the pH using sulfuric acid or sodium hydroxide and controlling the temperature at 25±5℃.

7. The application of the metal etching solution additive as described in any one of claims 1-4 in improving the aspect ratio of titanium etching, characterized in that: The additive is added to the fluorine-containing base etching solution at a volume ratio of 1:20 to 1:

5. The base etching solution is a mixture of hydrofluoric acid and nitric acid, wherein the HF concentration is 3-10wt% and the HNO3 concentration is 15-40wt%.

8. The application of the metal etching solution additive as described in claim 7 in improving the aspect ratio of titanium etching, characterized in that: Etching process parameters include: Etching temperature: 20-50℃; Etching time: 5-30 minutes; Stirring conditions: ultrasonic oscillation or mechanical stirring.

9. The application of the metal etching solution additive as described in claim 7 in improving the aspect ratio of titanium etching, characterized in that: The additives improve the aspect ratio of titanium etching to 0.6-0.

9.

10. The application of the metal etching solution additive as described in any one of claims 1-4 in improving the aspect ratio of steel or aluminum etching, characterized in that: For steel etching: the additive is added to the base etching solution containing ferric chloride at a volume ratio of 1:15 to 1:8, wherein the FeCl3 concentration is 20-40wt%, the etching temperature is 30-60℃, and an etching aspect ratio of 0.65-0.85 is achieved. For aluminum etching: the additive is added to the phosphoric acid-containing base etching solution at a volume ratio of 1:25 to 1:10, wherein the H3PO4 concentration is 35-70wt%, the etching temperature is 40-80℃, and the etching aspect ratio is 0.70-0.90.

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