Etching solution for metal, method for producing etching solution for metal, and raw material set of etching solution for metal

Abstract

Provided is an etching solution for metal containing: polyiodide ions obtained by reacting solid iodine and hydriodic acid; and an aqueous solvent.

Description

Metal etching solution, method for manufacturing a metal etching solution, and raw material set for a metal etching solution. 【0001】 The present invention relates to an etching solution for metals, a method for producing an etching solution for metals, and a set of raw materials for an etching solution for metals. 【0002】 Various developments have been made regarding fluorine-based etching solutions. As an example of this type of technology, the technology described in Patent Document 1 is known. The examples in Patent Document 1 describe an iodine-based etching solution for etching a material in which palladium and gold coexist, which is made by mixing iodine, potassium iodide, a water-soluble polymer compound such as polyvinylpyrrolidinone, and an organic solvent such as N-methyl-2-pyrrolidinone. 【0003】 Japanese Patent Publication No. 2014-082480 【0004】 However, as a result of our investigation, we found that there is room for improvement in the etching performance of metals in etching solutions containing iodine and potassium iodide, such as those described in Patent Document 1. 【0005】 The inventors of the present invention have further investigated and found that I ２ By reacting iodine with HI, the reaction-promoting effect of HI allows for the stable generation of water-soluble polyiodide ions from poorly water-soluble solid iodine. We discovered that these ions can act as an etching agent for metals, thus completing the present invention. 【0006】 According to one aspect of the present invention, the following metal etching solution, a method for manufacturing a metal etching solution, and a set of raw materials for a metal etching solution are provided. 【0007】 1. A metal etching solution containing polyiodide ions and an aqueous solvent, obtained by reacting solid iodine with hydroiodic acid. 2. A solution containing polyiodide ions and an aqueous solvent, measured by thiosulfuric acid titration. ２1. A metal etching solution having a concentration of 0.1 mol / L or more and 10 mol / L or less, and an HI concentration of 1 mol / L or more and 8 mol / L or less as measured by neutralization titration. 3. A metal etching solution according to 1. or 2., wherein the saturated solubility of copper iodide at room temperature of 25°C is 1 g / L or more. 4. A metal etching solution according to any one of 1. to 3., used for etching a metal containing one or more selected from the group consisting of copper, nickel, and aluminum. 5. A method for producing a metal etching solution, comprising a reaction step of reacting solid iodine with hydroiodic acid. 6. A method for producing a metal etching solution according to 5., wherein in the metal etching solution after the reaction step, the HI concentration measured by thiosulfate titration is ２ A method for producing a metal etching solution, wherein the HI concentration measured by neutralization titration is 1 mol / L to 8 mol / L, with a concentration of 0.1 mol / L or more and 10 mol / L or less. 7. A raw material set for a metal etching solution, comprising a first agent containing solid iodine and a second agent containing hydroiodic acid. 【0008】 According to the present invention, a metal etching solution with excellent etching performance for metals, a method for manufacturing a metal etching solution, and a set of raw materials for a metal etching solution are provided. 【0009】 The outline of the metal etching solution of this embodiment will be described. 【0010】 The metal etching solution of the first embodiment contains polyiodide ions and an aqueous solvent obtained by reacting solid iodine with hydroiodic acid. 【0011】 The etching solution for metals in the second embodiment contains polyiodide ions and an aqueous solvent, and is measured by thiosulfate titration. ２ The concentration must be between 0.1 mol / L and 10 mol / L, and the HI concentration measured by neutralization titration must be between 1 mol / L and 8 mol / L. 【0012】According to the findings of the present inventors, it has been found that water-soluble polyiodide ions act as one of the etching agents that react with metals. Further, by using water-soluble polyiodide ions that dissolve in a water solvent rather than poorly water-soluble solid iodine, the concentration of the etching agent in the water solvent can be increased. 【0013】 The metal etching solution can be applied to wet etching of metal materials in semiconductor manufacturing processes, substrate manufacturing processes, etc. The metal etching solution can be used to etch one or more metals selected from the group consisting of copper, nickel, and aluminum. Further, the metal etching solution may have high etching selectivity for the above metals with respect to the resin used for the substrate material and the resist material in the printed circuit board. 【0014】 Hereinafter, the manufacturing method of the metal etching solution of the present embodiment will be described in detail. 【0015】 An example of the manufacturing method of the metal etching solution includes a reaction step of reacting solid iodine and hydroiodic acid. 【0016】 In the above reaction step, solid iodine (I ２ ) and hydroiodic acid (HI) may be reacted in a water solvent. In the above reaction step, the order of adding solid iodine, hydroiodic acid, and, if necessary, the water solvent into the container is not particularly limited. As an example, after adding hydroiodic acid to the water solvent, solid iodine may be added. If necessary, stirring and / or heating may be performed. Further, each component may be added in divided portions in multiple times instead of being added all at once. 【0017】 In the above reaction step, by reacting I ２ and HI, water-soluble polyiodide ions can be generated from poorly water-soluble solid iodine due to the reaction promoting action of HI. That is, HI supplies I - during the reaction, and the reaction with solid iodine I ２ can promote the reaction to generate polyiodide ions (for example, I ３ - etc.). 【0018】According to the inventors' findings, hydroiodic acid has been found to have superior reaction-accelerating ability compared to sodium iodide and potassium iodide. Therefore, using an aqueous solution obtained by reacting solid iodine with hydroiodic acid (the etching solution of this embodiment) can improve etching performance compared to an aqueous solution obtained by reacting solid iodine with sodium iodide or potassium iodide. 【0019】 In this specification, polyiodide ions are defined as having the general formula [I ｎ ] ｍ－ It can be represented as follows (where n is an integer of 3 or more, between 3 and 29, and m is an integer from 1 to 3 depending on the value of n). These can be included individually or in any combination of two or more. A specific polyiodide ion is, for example, the triiodide ion (I ３ － ), pentaiodide ion (I ５ － ), and heptaiodide ions (I ７ － It includes one or more selected from the group consisting of ). 【0020】 The etching solution is an aqueous solution containing polyiodide ions, and any aqueous solution containing one or more of the above-mentioned polyiodide ions is acceptable, preferably triiodide ions (I ３ － It is an aqueous solution containing (I) in a triiodide ion aqueous solution. ３ － The content ratio of triiodide ions (I) is not particularly limited, but ３ － ) may be the main component, for example, 50% by mass or more. 【0021】 The solid iodine used in the above reaction process may be any solid at room temperature, and may be granulated into spherical shapes. ２ It is a solid at room temperature and pressure. 【0022】 The above hydroiodic acid contains HI and H ２It is a solution containing O. The HI concentration in hydroiodic acid used in the above reaction step is not particularly limited, but from the viewpoint of reaction acceleration efficiency, a relatively high concentration is preferable. For example, it may be 55% by mass to 60% by mass. In this specification, "~" represents including the upper limit value and the lower limit value unless otherwise specified. 【0023】 The above water solvent ２ may be a solvent containing H ２ O, and other solvents may be contained as long as the above reaction is not inhibited. The content of H 【0024】 O contained in the water solvent used in the above reaction step is, for example, 50 to 100% by mass, preferably 80 to 100% by mass, more preferably 90 to 100% by mass, still more preferably 95 to 100% by mass in 100% by mass of the water solvent. ２ (solid) may remain. Even if polyiodide ions are consumed by the use of the etching solution, new polyiodide ions can be generated as an etching agent during use by the remaining HI and I ２ . Thereby, the etching performance can be further improved. Also, it is possible to maintain the performance of the etching solution by adding HI and / or I ２ . 【0025】 Hereinafter, each component of the metal etching solution of this embodiment will be described in detail. 【0026】 The etching solution may contain polyiodide ions and a water solvent. 【0027】 The etching solution containing polyiodide ions may have at least one of a first absorption peak at a position of 350 nm ± 10 and a second absorption peak at a position of 290 nm ± 10 in an absorption spectrum using an ultraviolet-visible spectrophotometer. 【0028】In etching solutions, I is measured by titration of thiosulfate. ２ In terms of concentration, from the viewpoint of etching performance, the lower limit is, for example, 0.1 mol / L or more, preferably 0.35 mol / L or more, and more preferably 0.5 mol / L, and from the viewpoint of economic efficiency, the upper limit is, for example, 10 mol / L or less, preferably 5 mol / L or less, and more preferably 2 mol / L or less. Furthermore, the HI concentration measured by neutralization titration in the etching solution is, for example, 1 mol / L or more and 8 mol / L or less, preferably 5 mol / L or more, and more preferably 7 mol / L or more. By setting the concentration above the above lower limit, etching performance can be further improved. 【0029】 The etching solution for metal after the above reaction step is also the I mentioned above. ２ It may have a concentration and an HI concentration. Depending on the amount of solid iodine and hydroiodic acid used as raw materials in the above reaction step, the above I ２ The concentration and HI concentration can be controlled. 【0030】 From the viewpoint of etching performance, the lower limit of the etching solution temperature is, for example, 0°C or higher, preferably 10°C or higher, and more preferably 20°C or higher. From the viewpoint of operability, the upper limit is, for example, 80°C or lower, preferably 60°C or lower, and more preferably 50°C or lower. 【0031】 From the viewpoint of etching performance, the pH of the etching solution is, for example, 6 or less, preferably 3 or less, and more preferably 1 or less. 【0032】 The etching solution may have the property of dissolving copper iodide. In this case, the etching solution has a saturation solubility of copper iodide at room temperature of 25°C, for example, 1 g / L to 450 g / L, preferably 50 g / L to 450 g / L, and more preferably 200 g / L to 450 g / L. 【0033】According to the inventors' findings, it has been found that the etching solution can dissolve copper iodide, which is poorly water-soluble. Although the detailed mechanism is not clear, it is presumed that the copper iodide dissolves in the hydroiodic acid in the etching solution, thereby suppressing the precipitation of copper iodide in the aqueous solvent in the etching solution. In other words, copper iodide undergoes CuI ↔ Cu in the presence of HI. ＋ +I － Due to the properties of the etching solution that dissolves copper iodide, which allows it to maintain a dissolved state in equilibrium with polyiodide ions in order to form equilibrium, it is possible to keep the copper iodide, which is formed by the reaction of metallic copper and polyiodide ions during etching of metallic copper, dissolved without deposition. Therefore, the deposition of copper iodide in the etching solution used after the etching process can be suppressed, eliminating the need for copper iodide removal. Furthermore, because the etching solution has a tolerance (saturation solubility) for dissolving copper iodide, the etching performance during copper etching can be further enhanced. 【0034】 The raw material set for the metal etching solution of this embodiment may include a first agent containing solid iodine and a second agent containing hydroiodic acid. The first and second agents may each be contained in separate containers. 【0035】 An example of a substrate manufacturing method using the metal etching solution of this embodiment may include a preparation step of preparing a substrate including a metal structure, and an etching step of etching the metal structure using the metal etching solution described above. 【0036】Furthermore, the substrate manufacturing method may include a recycling step in which the metal etching solution used in the etching process is reused in the etching process. The substrate manufacturing method may include a condition evaluation step before the recycling step in which the saturation solubility of copper iodide in the metal etching solution used in the etching process is measured. In the condition evaluation step, if the saturation solubility is below a predetermined value, at least one of solid iodine and hydroiodic acid may be added before using the solution in the recycling step. Furthermore, if metal iodide precipitates in the solution after the etching process, the substrate manufacturing method may include a step of separating at least a portion of the precipitated metal iodide. The recycling step may be carried out using the etching solution after this separation step. 【0037】 Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. 【0038】 The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples. 【0039】 <Production of Etching Solution> [Examples 1-8] Solid iodine, hydroiodic acid with an HI concentration of 57% by mass (57% HI), and pure water are mixed to produce the mixture shown in Table 1. ２ Solutions (etching solutions) of varying concentrations and HI concentrations were prepared. 【0040】 [Comparative Example 1] Hydroiodic acid (57% HI) was used as the etching solution in Comparative Example 1. 【0041】 [Comparative Example 2] Solid iodine, sodium iodide (NaI), and pure water are mixed, ２ Solutions (etching solutions) with concentrations of 0.2 mol / L and 1.8 mol / L of NaI were prepared. 【0042】 The above etching solution is the subject of I ２ The concentration was measured by thiosulfate titration, and the HI concentration was measured by neutralization titration. 【0043】 (Detection of Polyiodide Ions) The absorbance of the etching solutions of Examples 1 to 8 was measured in the wavelength range of 200 nm to 700 nm using a UV-Vis spectrophotometer with a cell length of 1 cm and a room temperature of 25°C. In the obtained absorption spectra, it was confirmed that each example had a first absorption peak at approximately 350 nm and a second absorption peak at approximately 290 nm. Both the first and second absorption peaks are presumed to originate from polyiodide ions. The first absorption peak is known as a peak for quantifying triiodide ions. However, a portion of the second peak is I － There is a possibility that it overlaps with the absorption peak at approximately 260 nm from which it originated. 【0044】 【0045】 The following items were evaluated for the obtained etching solution. 【0046】 (Evaluation of Etching Properties) A ​​test specimen was prepared by forming a 35 μm thick square copper foil on both sides of a 10 cm x 10 cm square epoxy resin substrate (FR-4). At room temperature, the prepared test specimen was immersed in the etching solution obtained above up to a height of 1 cm on one side of the square copper foil, and the etching time (minutes) was measured when the copper foil on both sides of the immersed portion was completely dissolved (when the substrate was completely exposed). The results are shown in Table 1. Note that in Table 1, the etching time for Comparative Example 1 exceeded 120 minutes. 【0047】 After immersion tests using the etching solutions of Examples 1 to 8, no solid copper iodide was visually observed in any of the solutions. Compared to Comparative Examples 1 and 2, the etching solutions of Examples 1 to 8 showed shorter etching times and superior etching performance for metals such as copper. 【0048】In the immersion tests described above, no dissolution of the underlying epoxy resin substrate was observed with the etching solutions of Examples 1 to 8. Furthermore, a test specimen was prepared by applying a resist to the entire surface of one side of an epoxy resin substrate (FR-4), and similarly, it was immersed in the etching solution. In this case, no dissolution of the resist was observed with the etching solutions of Examples 1 to 8. These results indicate that the etching solutions of Examples 1 to 8 exhibit high metal etching selectivity for resins. 【0049】 (Evaluation of copper iodide solubility) Solid iodine, hydroiodic acid with an HI concentration of 57% by mass (57% HI), and pure water were mixed to produce the solution shown in Table 2. ２ Solutions of varying concentrations and HI concentrations were prepared. Solid copper iodide (99% purity) was continuously added to the solutions obtained for Experimental Examples 1-4 while stirring. After saturation, when undissolved copper iodide was present in the solution, the supernatant was collected and filtered to remove the solid components. 1 mL of the filtered supernatant, 20 mL of pure water, and 5 mL of nitric acid were divided into 200 mL beakers and nitric acid decomposition was performed. After cooling, the solution was transferred to a 100 mL volumetric flask and pure water was added to the mark (100-fold dilution). Furthermore, the copper ion concentration of the 1000-fold diluted solution was measured using emission spectroscopy. Using the obtained copper ion concentration before dilution, the mass of copper iodide was determined from the atomic ratio of 190 (CuI) / 63.5 (Cu), and this was divided by the volume of the supernatant (1 mL) to calculate the solubility (g / L) of copper iodide in each experimental example solution. The results are shown in Table 2. 【0050】 Table 2 shows that the solubility of copper iodide in the solutions of Experimental Examples 1 to 4 increased proportionally with increasing HI concentration. From these results, it was confirmed that the etching solutions of Examples 1 to 8 have copper iodide solubility, meaning they can dissolve the copper iodide generated by etching copper foil. 【0051】 【0052】 (Evaluation of etching properties of etching solution containing copper iodide) Solid iodine, hydroiodic acid with an HI concentration of 57% by mass (57% HI), and pure water are mixed, ２Solutions with a concentration of 0.7 mol / L and an HI concentration of 7.3 mol / L were obtained. Solid copper iodide (99% purity) was added to the obtained solutions to prepare etching solutions with the copper iodide concentrations (g / L) shown in Table 3. The etching tests described above (evaluation of etching properties) were performed using the etching solutions obtained in Examples 9 to 12, and the etching time was measured. The results are shown in Table 3. 【0053】 Table 3 shows that for the etching solutions in Examples 9 to 12, the lower the copper iodide concentration (the greater the allowable amount of copper iodide to dissolve before saturation), the shorter the etching time. 【0054】 【0055】 This application claims priority based on Japanese Patent Application No. 2024-214458, filed on 9 December 2024, and incorporates all of its disclosures herein.

Claims

1. A metal etching solution containing polyiodide ions and an aqueous solvent, obtained by reacting solid iodine with hydroiodic acid.

2. A solution containing polyiodide ions and an aqueous solvent, measured by thiosulfate titration. ２ A metal etching solution having a concentration of 0.1 mol / L or more and 10 mol / L or less, and an HI concentration of 1 mol / L or more and 8 mol / L or less as measured by neutralization titration.

3. A metal etching solution according to claim 1 or 2, wherein the saturation solubility of copper iodide at room temperature of 25°C is 1 g / L or more.

4. A metal etching solution according to claim 1 or 2, which is used to etch a metal containing one or more selected from the group consisting of copper, nickel, and aluminum.

5. A method for producing a metal etching solution, comprising a reaction step of reacting solid iodine with hydroiodic acid.

6. A method for producing a metal etching solution according to claim 5, wherein in the metal etching solution after the reaction step, I is measured by thiosulfate titration. ２ A method for producing a metal etching solution, wherein the concentration is 0.1 mol / L or more and 10 mol / L or less, and the HI concentration measured by neutralization titration is 1 mol / L or more and 8 mol / L or less.

7. A raw material set for a metal etching solution, comprising a first agent containing solid iodine and a second agent containing hydroiodic acid.

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