Copper etching solution for semiconductor packaging and method for preparing the same

Abstract

The application discloses a copper etching solution for semiconductor packaging and a preparation method thereof, and relates to the technical field of electronic chemicals.The etching solution comprises the following components in percentage by mass: an oxidizing agent 3-5 wt%, an inorganic acid 10-15 wt%, an organic acid 8-15 wt%, a complexing agent 0.5-3 wt%, a corrosion inhibitor 0.05-0.5 wt%, a surfactant 0.1-0.5 wt%, a stabilizer 0.01-1%, a functional component 0.3-1.2 wt%, a synergistic component 0.05-0.3 wt%, and deionized water as the balance.The copper etching solution has the advantages of small side etching amount, smooth copper surface, high selectivity, slow performance attenuation, and the like, is suitable for high-density ultra-fine copper circuit etching processes of semiconductor packaging, and has excellent circuit forming precision and packaging reliability.

Description

Technical Field

[0001] This invention relates to the field of electronic chemicals technology, and in particular to a copper etching solution for semiconductor packaging and its preparation method. Background Technology

[0002] In the semiconductor packaging industry, etching is a core step in achieving copper wiring patterning. Its purpose is to selectively remove the copper layer on the substrate surface that is not protected by the resist layer, leaving the predetermined circuit pattern, which directly determines the interconnect density, electrical performance, and structural stability of semiconductor devices. With the rapid development of semiconductor packaging technology towards miniaturization and high density, advanced packaging technologies such as wafer-level packaging (WLP) and system-in-package (SiP) are widely used. The linewidth and spacing of redistribution layers are constantly shrinking, and the thickness of copper seed layers and the size of metal bumps are also constantly decreasing. This places extremely high demands on the etching precision, controllability of etching rate, selectivity, and stability of copper etching solutions.

[0003] Existing copper etching solutions are mainly divided into two categories: alkaline etching solutions and acidic etching solutions. While alkaline etching solutions offer faster etching rates, they are prone to lateral etching in fine circuit fabrication, leading to significant loss of line width and making it difficult to meet the requirements for fine pitch. Acidic etching solutions are primarily based on hydrogen peroxide-sulfuric acid or hydrogen peroxide-phosphoric acid systems. These solutions are lower in cost, but generally suffer from difficulty in controlling the etching rate. Especially when etching the copper seed layer, excessively fast etching rates can easily lead to lateral loss of redistribution layers and metal bumps, disrupting the regularity of the circuit morphology. Furthermore, commercially available copper etching solutions for semiconductor packaging also exhibit varying degrees of instability during use, affecting etching consistency; they are also prone to precipitation or crystallization in the solution, clogging nozzles or contaminating the wafer surface, limiting their application in long-term continuous industrial production.

[0004] To address the aforementioned issues, invention patent document CN115786915B discloses a copper etching solution for semiconductor packaging. By mass percentage, its main components are: 1%–8% oxidant, 21%–40% inorganic acid, 6%–30% organic carboxylic acid, 0.001%–15% chelating agent, 0–3% corrosion inhibitor, and the balance being deionized water. The organic carboxylic acid is composed of a first carboxylic acid and a second carboxylic acid, wherein the first carboxylic acid is selected from at least one monocarboxylic acid and a dicarboxylic acid, and the second carboxylic acid is at least one tricarboxylic acid or higher. This invention's copper etching solution for semiconductor packaging, by optimizing the organic carboxylic acid and adjusting the content of the etching solution components, reduces the etching rate and improves the etching precision. While completely etching away the copper seed layer, it also reduces lateral losses of the copper etching solution to other copper layers in the redistribution layer and metal bumps, resulting in a more regular morphology and improved structural stability of the redistribution layer and metal bumps. However, its etching selectivity, effectiveness, and service life still have considerable room for improvement. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a copper etching solution for semiconductor packaging and its preparation method. This copper etching solution exhibits high etching precision, stable etching rate, good selectivity, and strong versatility.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a copper etching solution for semiconductor packaging, comprising functional components with the following structure: .

[0007] Preferably, the copper etching solution for semiconductor packaging comprises, by mass percentage: 3-5 wt% oxidant, 10-15 wt% inorganic acid, 8-15 wt% organic acid, 0.5-3 wt% complexing agent, 0.05-0.5 wt% corrosion inhibitor, 0.1-0.5 wt% surfactant, 0.01-1% stabilizer, 0.3-1.2 wt% functional component, 0.05-0.3 wt% synergistic component, with the balance being deionized water.

[0008] Preferably, the oxidant is at least one selected from hydrogen peroxide, potassium persulfate, and sodium persulfate.

[0009] Preferably, the inorganic acid is at least one of sulfuric acid and phosphoric acid.

[0010] Preferably, the organic acid is a compound of lactobionic acid, citric acid and 2-methyl-3-hydroxypropionic acid in a mass ratio of 1:(3-5):(0.8-1.2).

[0011] Preferably, the complexing agent is a compound of disodium ethylenediaminetetraacetate and aminotrimethylenephosphonic acid in a mass ratio of 1:(3-5).

[0012] Preferably, the corrosion inhibitor is a compound of hydroxybenzotriazole and polyvinylpyrrolidone (PVP) K15 in a mass ratio of 2:(0.8-1.2).

[0013] Preferably, the surfactant is a fatty alcohol polyoxyethylene ether.

[0014] Preferably, the stabilizer is at least one of acetone oxime and aminosulfonic acid.

[0015] Preferably, the synergistic component is at least one of 2-hydroxyphosphonoacetic acid and N-acetyl-L-cysteine.

[0016] Another object of the present invention is to provide a method for preparing the copper etching solution for semiconductor packaging, comprising the following steps: mixing the components uniformly according to the mass percentage to obtain the copper etching solution.

[0017] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The copper etching solution for semiconductor packaging disclosed in this invention achieves multi-dimensional synergistic improvement in etching accuracy, uniformity, process stability and product reliability through precise compounding of specific functional components and synergistic components, overcoming the defects of existing etching solutions in high-density fine line copper etching, such as side etching, line width deviation, excessive surface roughness and short etching solution life. The dual quaternary ammonium salt functional component containing a 1,3,4-oxadiazole core is the core for achieving precise control of etching behavior: the oxadiazole core can form strong coordination adsorption with the copper surface through nitrogen and oxygen atoms, preferentially constructing a dense protective barrier at highly active sites such as copper grain boundaries and crystal plane steps, and inhibiting excessive etching of highly active sites through steric hindrance effect, fundamentally reducing the side etching factor; at the same time, the conjugated system of the oxadiazole core can stabilize the positive charge of the intramolecular quaternary ammonium salt, and with the electrostatic directional adsorption of the dual quaternary ammonium salt structure and the hydrogen bond-assisted film formation of the dihydroxyethyl, a triple stable adsorption film of "coordination bond + electrostatic adsorption + hydrogen bond assistance" is formed on the copper surface, which can achieve fine control of the reaction rate difference of different copper crystal planes, significantly improve etching uniformity, and avoid defects such as line gaps and linewidth deviations.

[0018] (2) The copper etching solution for semiconductor packaging disclosed in this invention forms a multi-dimensional synergistic system with synergistic and functional components: 2-hydroxyphosphonoacetic acid and N-acetyl-L-cysteine ​​can form hydrogen bonds with the nitrogen atoms of the phosphonate group, thiol group and oxadiazole core for synergistic adsorption, further enhancing the protective effect on the copper surface, and at the same time can complex the Cu produced during the etching process. 2+ To avoid Cu 2+ The catalytic decomposition of oxidants such as hydrogen peroxide and hydrogen persulfate significantly extends the service life of the etching solution; the chemical stability of the oxadiazole core also prevents the functional components from decomposing in strongly acidic and strongly oxidizing etching systems, ensuring the performance consistency of the etching solution during long-term use.

[0019] (3) The copper etching solution for semiconductor packaging disclosed in this invention has a component system that forms a synergistic relationship with other functional components such as organic acids, complexing agents, and corrosion inhibitors: the organic acid system composed of lactobionic acid, citric acid and 2-methyl-3-hydroxypropionic acid can provide a stable acidic environment and help regulate the etching rate. Combined with the complexing agent composed of disodium ethylenediaminetetraacetate and aminotrimethylenephosphonic acid, it can synergistically complex metal ions in the etching process and avoid side reactions caused by metal ions. The corrosion inhibitor composed of hydroxybenzotriazole and PVP K15 can form complementary protection with the functional components, further improving the protection effect on the copper surface without increasing organic residues, reducing the amount of corrosion inhibitor used, and reducing the pollution risk of subsequent processes.

[0020] (4) The copper etching solution for semiconductor packaging disclosed in this invention can achieve excellent etching control effect with a low amount of corrosion inhibitor and surfactant. The flatness and corrosion resistance of the copper surface after etching are significantly improved, avoiding the problem of insufficient bonding force in subsequent electroplating and bonding processes. At the same time, the stable etching rate and uniformity control greatly reduce the defect rate in high-density fine line packaging process, improve production efficiency and product yield, and provide a high-efficiency, stable and highly adaptable technical solution for copper etching for semiconductor packaging. Detailed Implementation

[0021] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0022] Example 1

[0023] This embodiment provides a method for preparing a functional component, comprising the following steps: using N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid and 2,5-dichloromethyl-1,3,4-oxadiazole as raw materials, and anhydrous sodium carbonate as an acid-binding agent in anhydrous DMF, the mixture is stirred at 80°C under nitrogen protection for 20 hours. After the reaction, insoluble matter is removed by filtration, the solvent is removed by rotary evaporation of the filtrate, and then recrystallized from ethanol-ethyl acetate to obtain the functional component; the molar ratio of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, 2,5-dichloromethyl-1,3,4-oxadiazole, anhydrous DMF, and anhydrous sodium carbonate is 1:2.1:2.2:30; the NMR characterization of the product is as follows: 1 ¹H NMR (400 MHz, DMSO-d6) δ: 4.8 (4H, s, active hydrogen of hydroxyethyl-OH), 4.3 (4H, s, oxadiazole ring-CH₂N) + Methylene), 4.0 (8H, m, quaternary ammonium nitrogen-linked -CH2CH2OH near the hydroxyl end methylene), 3.8 (4H, t, quaternary ammonium nitrogen-linked -CH2CH2SO3) - (near the sulfonic acid terminal methylene group), 3.6 (8H, m, quaternary ammonium nitrogen-linked -CH2CH2OH near the nitrogen-terminal methylene group), 3.3 (4H, t, quaternary ammonium nitrogen-linked -CH2CH2SO3) - (near the nitrogen-terminal methylene group).

[0024] Example 2

[0025] A copper etching solution for semiconductor packaging includes functional components with the following structure: .

[0026] The copper etching solution for semiconductor packaging comprises, by mass percentage: 3 wt% oxidant, 10 wt% inorganic acid, 8 wt% organic acid, 0.5 wt% complexing agent, 0.05 wt% corrosion inhibitor, 0.1 wt% surfactant, 0.01% stabilizer, 0.3 wt% functional component, 0.05 wt% synergistic component, with the balance being deionized water; the oxidant is hydrogen peroxide; the inorganic acid is sulfuric acid; the organic acid is lactobionic acid, citric acid, and 2-methyl-3-hydroxypropionic acid compounded in a mass ratio of 1:3:0.8; the complexing agent is disodium ethylenediaminetetraacetate and aminotrimethylenephosphonic acid compounded in a mass ratio of 1:3; the corrosion inhibitor is hydroxybenzotriazole and polyvinylpyrrolidone (PVP K15) compounded in a mass ratio of 2:0.8; the surfactant is fatty alcohol polyoxyethylene ether; the stabilizer is acetone oxime; and the synergistic component is 2-hydroxyphosphonoacetic acid.

[0027] A method for preparing a copper etching solution for semiconductor packaging includes the following steps: mixing the components evenly according to their mass percentages to obtain the copper etching solution.

[0028] Example 3

[0029] A copper etching solution for semiconductor packaging includes functional components with the following structure: .

[0030] The copper etching solution for semiconductor packaging comprises, by mass percentage: 3.5 wt% oxidant, 11 wt% inorganic acid, 9 wt% organic acid, 1 wt% complexing agent, 0.1 wt% corrosion inhibitor, 0.2 wt% surfactant, 0.2 wt% stabilizer, 0.5 wt% functional component, 0.1 wt% synergistic component, with the balance being deionized water; the oxidant is potassium persulfate; the inorganic acid is phosphoric acid; the organic acid is a mixture of lactobionic acid, citric acid, and 2-methyl-3-hydroxypropionic acid in a mass ratio of 1:3.5:0.9; the complexing agent is a mixture of disodium ethylenediaminetetraacetate and aminotrimethylenephosphonic acid in a mass ratio of 1:3.5; the corrosion inhibitor is a mixture of hydroxybenzotriazole and polyvinylpyrrolidone (PVP K15) in a mass ratio of 2:0.9; the surfactant is fatty alcohol polyoxyethylene ether; the stabilizer is aminosulfonic acid; and the synergistic component is N-acetyl-L-cysteine.

[0031] A method for preparing a copper etching solution for semiconductor packaging includes the following steps: mixing the components evenly according to their mass percentages to obtain the copper etching solution.

[0032] Example 4

[0033] A copper etching solution for semiconductor packaging includes functional components with the following structure: .

[0034] Preferably, the copper etching solution for semiconductor packaging comprises, by mass percentage: 4 wt% oxidant, 13 wt% inorganic acid, 12 wt% organic acid, 2 wt% complexing agent, 0.3 wt% corrosion inhibitor, 0.35 wt% surfactant, 0.6% stabilizer, 0.8 wt% functional component, 0.2 wt% synergistic component, and the balance being deionized water; the oxidant is a mixture of hydrogen peroxide, potassium persulfate, and sodium persulfate in a mass ratio of 1:1:1; the inorganic acid is a mixture of sulfuric acid and phosphoric acid in a mass ratio of 1:2; the organic acid is a mixture of lactobionic acid, citric acid, and 2-methyl-3-hydroxypropionic acid in a mass ratio of 1:4:1; the complexing agent is a mixture of disodium ethylenediaminetetraacetate and aminotrimethylenephosphonic acid in a mass ratio of 1:4; and the corrosion inhibitor is hydroxybenzotriazole and polyvinylpyrrolidone (PVP). K15 is compounded in a mass ratio of 2:1; the surfactant is fatty alcohol polyoxyethylene ether; the stabilizer is compounded in a mass ratio of acetone oxime and aminosulfonic acid in a mass ratio of 1:1; the synergistic component is compounded in a mass ratio of 2-hydroxyphosphonoacetic acid and N-acetyl-L-cysteine ​​in a mass ratio of 3:5.

[0035] A method for preparing a copper etching solution for semiconductor packaging includes the following steps: mixing the components evenly according to their mass percentages to obtain the copper etching solution.

[0036] Example 5

[0037] A copper etching solution for semiconductor packaging includes functional components with the following structure: .

[0038] Preferably, the copper etching solution for semiconductor packaging comprises, by mass percentage: 5 wt% oxidant, 15 wt% inorganic acid, 15 wt% organic acid, 3 wt% complexing agent, 0.5 wt% corrosion inhibitor, 0.5 wt% surfactant, 1% stabilizer, 1.2 wt% functional component, 0.3 wt% synergistic component, and the balance being deionized water; the oxidant is hydrogen peroxide; the inorganic acid is phosphoric acid; the organic acid is lactobionic acid, citric acid, and 2-methyl-3-hydroxypropionic acid compounded in a mass ratio of 1:5:1.2; the complexing agent is disodium ethylenediaminetetraacetate and aminotrimethylenephosphonic acid compounded in a mass ratio of 1:5; the corrosion inhibitor is hydroxybenzotriazole and polyvinylpyrrolidone (PVP K15) compounded in a mass ratio of 2:1.2; the surfactant is fatty alcohol polyoxyethylene ether; the stabilizer is acetone oxime; and the synergistic component is N-acetyl-L-cysteine.

[0039] A method for preparing a copper etching solution for semiconductor packaging includes the following steps: mixing the components evenly according to their mass percentages to obtain the copper etching solution.

[0040] Comparative Example 1 A copper etching solution for semiconductor packaging is basically the same as that in Example 5, except that an equal amount of functional components are used instead of synergistic components.

[0041] Comparative Example 2 A copper etching solution for semiconductor packaging is basically the same as that in Example 5, except that an equal amount of synergistic components are used instead of functional components.

[0042] Comparative Example 3 A copper etching solution for semiconductor packaging is basically the same as that in Example 5, except that an equal amount of pyridinium hydroxypropanesulfonate is used instead of the functional component.

[0043] To further illustrate the unexpected positive technical effects achieved by the present invention, the relevant performance of the copper etching solutions in Example 5 and Comparative Examples 1-3 was tested. The test results are shown in Table 1, and the test methods are as follows: (1) Etching selectivity test: Select a copper substrate with titanium adhesion layer and use the etching solution of each experimental group for etching (etching temperature 30℃, etching time 60s); after etching, use an ICP-OES inductively coupled plasma emission spectrometer to detect the concentration of titanium ions in the etching solution and calculate the corrosion rate of the titanium adhesion layer; Etching selectivity = copper etching rate / titanium corrosion rate. Each group of experiments was repeated 3 times and the average value was taken.

[0044] (2) Etching accuracy and side etching amount test: The copper substrate was photolithographically and developed to form a resist pattern with a line width of 10μm and a line spacing of 10μm; etching was performed using the etching solution of each experimental group (etching temperature 30℃, etching time 60s); after etching, the morphology of the circuit was observed with a metallographic microscope, and the actual line width and side etching amount were measured (side etching amount = (initial line width - actual line width) / 2). Ten points were tested in each experimental group, and the average value was taken.

[0045] (3) Etching uniformity test: The roughness of the etched surface of the copper substrate was observed using a metallographic microscope. Five points were tested in each group of experiments, and the average value was taken.

[0046] (4) Stability test: The etching solution of each experimental group was placed in a constant temperature and humidity chamber, and the temperature was controlled at 25℃ and the humidity at 60%, and it was sealed and stored. After 30 days of storage, the etching rate of the etching solution was detected and the etching rate change rate (%) was calculated.

[0047] Table 1 As can be seen from the test results in Table 1, Example 5 exhibits superior overall etching performance compared to Comparative Examples 1-3. Its lateral etching depth is only 0.25 μm, and its surface roughness Ra is as low as 16.2 nm, which is much smaller than that of the comparative examples. The etched lines have regular sidewalls and a smooth and uniform surface. The etching selectivity is as high as 47.5, which is significantly higher than that of the comparative examples. It can efficiently etch the copper layer while effectively protecting the titanium adhesion layer from corrosion. The rate of change after 30 days of storage is only 1.5%, which is much lower than that of Comparative Example 1 (8.7%), Comparative Example 2 (4.6%), and Comparative Example 3 (7.2%). This indicates that the etching precision, surface uniformity, interlayer selective protection, and storage stability of the compound system of this invention are significantly better than those of single additive ratios and conventional additive substitution systems.

[0048] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A copper etching solution for semiconductor packaging, characterized in that, Functional components including the following structures: 。 2. The copper etching solution for semiconductor packaging according to claim 1, characterized in that, The copper etching solution for semiconductor packaging comprises, by mass percentage: 3-5 wt% oxidant, 10-15 wt% inorganic acid, 8-15 wt% organic acid, 0.5-3 wt% complexing agent, 0.05-0.5 wt% corrosion inhibitor, 0.1-0.5 wt% surfactant, 0.01-1% stabilizer, 0.3-1.2 wt% functional component, 0.05-0.3 wt% synergistic component, with the balance being deionized water.

3. The copper etching solution for semiconductor packaging according to claim 2, characterized in that, The oxidant is at least one of hydrogen peroxide, potassium persulfate, and sodium persulfate.

4. The copper etching solution for semiconductor packaging according to claim 2, characterized in that, The inorganic acid is at least one of sulfuric acid and phosphoric acid.

5. The copper etching solution for semiconductor packaging according to claim 2, characterized in that, The organic acid is a compound of lactobionic acid, citric acid, and 2-methyl-3-hydroxypropionic acid in a mass ratio of 1:(3-5):(0.8-1.2).

6. The copper etching solution for semiconductor packaging according to claim 2, characterized in that, The complexing agent is a compound of disodium ethylenediaminetetraacetate and aminotrimethylenephosphonic acid in a mass ratio of 1:(3-5).

7. The copper etching solution for semiconductor packaging according to claim 2, characterized in that, The corrosion inhibitor is a compound of hydroxybenzotriazole and polyvinylpyrrolidone (PVP) K15 in a mass ratio of 2:(0.8-1.2).

8. The copper etching solution for semiconductor packaging according to claim 2, characterized in that, The surfactant is a fatty alcohol polyoxyethylene ether; the stabilizer is at least one of acetone oxime and aminosulfonic acid.

9. The copper etching solution for semiconductor packaging according to claim 2, characterized in that, The synergistic component is at least one of 2-hydroxyphosphonoacetic acid and N-acetyl-L-cysteine.

10. A method for preparing a copper etching solution for semiconductor packaging according to any one of claims 2-9, characterized in that, The process includes the following steps: After mixing the components evenly according to their mass percentages, a copper etching solution is obtained.

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