Etching solution for copper or copper alloys

Abstract

The objective is to provide an etching solution that is less likely to cause etching pit defects when etching copper or copper alloys, as well as a method for manufacturing an electronic substrate using the etching solution and an etching method. An etching solution for copper or copper alloys, comprising hydrogen peroxide, sulfuric acid, and halide ions, wherein the concentration of halide ions is 1000 ppm or more and 5000 ppm or less. An etching method comprising contacting the surface of a seed layer of copper or copper alloy with the etching solution. A method for manufacturing an electronic substrate, comprising the step of etching a seed layer of copper or copper alloy using the etching solution. Preferably, the etching solution further comprises azoles, copper ions, and / or a hydrogen peroxide stabilizer.

Description

[Technical Field]

[0001] The present invention relates to an etching solution for copper or copper alloys. [Background Art]

[0002] Conventionally, when manufacturing electronic substrates such as semiconductors and printed circuit boards, an etching process is performed to form circuits by dissolving and removing unnecessary copper with chemicals. For example, when forming copper wiring by the semi-additive method, a copper layer called a seed layer is formed on an insulating substrate, a resist pattern is formed on non-circuit portions thereon, electrolytic copper plating is applied to the circuit portions, and then the seed layer remaining between the wirings of the copper plating layer is removed by etching. At this time, the surface of the copper plating layer is also etched, so the selection of the etching solution to be used is important.

[0003] Generally, hydrogen peroxide / sulfuric acid-based etching solutions are used for etching copper such as seed layers. Similar etching solutions are sometimes used for etching the copper plating layer itself. However, conventional hydrogen peroxide / sulfuric acid-based etching solutions may cause local pitting corrosion, for example, defects called etching pits, or defects such as roughening of the copper wiring surface, extreme reduction in wiring width, and undercut.

[0004] Such defects often lead to deterioration of the characteristics of electronic substrates. For example, roughening of the copper wiring surface may increase transmission loss, and undercut increases the risk of peeling of fine wiring. Etching pits can form holes several times deeper than the etched amount, which may even lead to disconnection of the wiring. Various etching solutions have been studied for a long time to improve these defects.

[0005] For example, Patent Document 1 discloses an etching solution for copper or copper alloys containing 2-aminoimidazole, hydrogen peroxide, and an inorganic acid. Patent Document 2 discloses a copper etching agent containing hydrogen peroxide, an acid, an amino acid with a molecular weight of 300 or less, and a nitrogen-containing heterocyclic compound. Patent Document 3 discloses an etching composition for etching a copper seed layer containing hydrogen peroxide, sulfuric acid, azoles or their salts, glycol ethers, halide ions, and water. Furthermore, Patent Document 4 discloses a method for etching a copper plated layer using an etching solution containing hydrogen peroxide and an acid in a specific concentration ratio. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-204679 [Patent Document 2] Japanese Patent Publication No. 2021-195572 [Patent Document 3] International Publication No. 2023 / 163003 [Patent Document 4] Japanese Patent Publication No. 2017-125237 [Overview of the project] [Problems that the invention aims to solve]

[0007] The conventional technologies described above make it difficult to comprehensively solve the problems in the etching process. For example, the technologies disclosed in Patent Documents 1 to 3 can suppress surface shape defects to some extent by making the surface of the plated layer uniform and maintaining its smoothness. However, even with these technologies, etching pits are difficult to reduce, and the risk of electrical connection failures such as wire breakage cannot be completely eliminated.

[0008] The present invention aims to solve the above-mentioned problems by providing an etching solution that is less prone to etching pit defects when etching copper or a copper alloy, as well as a method for manufacturing an electronic substrate using the etching solution and an etching method. [Means for solving the problem]

[0009] The inventors of the present invention discovered that adding a certain amount or more of halide ions to an etching solution containing hydrogen peroxide and sulfuric acid reduces etching pit defects, and thus completed the present invention.

[0010] In other words, the present invention provides the following (1) to (9). (1) Containing hydrogen peroxide, sulfuric acid, and halide ions, The concentration of the halide ions is 1000 ppm or more and 5000 ppm or less. Etching solution for copper or copper alloys. (2) The etching solution according to (1) above, wherein the concentration of the halide ions is 1200 ppm or more and 4800 ppm or less. (3) The etching solution according to (1) or (2) above, further comprising azoles. (4) Any of the etching solutions described in (1) to (3) above, wherein the halide ions are chloride ions. (5) An etching solution containing copper ions, one of the above (1) to (4). (6) An etching solution containing any of the above (1) to (5), further comprising a hydrogen peroxide stabilizer. (7) An etching solution from any of (1) to (6) above for removing a seed layer of copper or a copper alloy. (8) An etching method comprising bringing one of the etching solutions described in (1) to (7) above into contact with the surface of a seed layer of copper or a copper alloy. (9) A method for manufacturing an electronic substrate, comprising the step of etching a copper or copper alloy seed layer using any of the etching solutions described in (1) to (7) above. [Effects of the Invention]

[0011] According to the etching solution of the present invention, defects caused by etching pits when etching copper or a copper alloy can be reduced or prevented. Mode for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail based on embodiments, but the present invention is not limited to these embodiments.

[0013] <<1. Etching Solution>> The etching solution according to the present embodiment is an etching solution for copper or a copper alloy, containing hydrogen peroxide, sulfuric acid, and halide ions, wherein the concentration of the halide ions is 1000 ppm or more and 5000 ppm or less.

[0014] <Hydrogen Peroxide - Sulfuric Acid> Hydrogen peroxide (H2O2) and sulfuric acid act as an oxidizing agent and a dissolving agent for copper or a copper alloy in the etching solution. These are well-known chemical substances, and any commercially available variety can be used in the etching solution of the present embodiment.

[0015] Note that the hydrogen peroxide in the etching solution may be derived from other types of peroxides. For example, peroxide ion O2 2- a compound containing the above is mixed with a sulfuric acid-containing solution to allow hydrogen peroxide to be contained in the solution. Examples of peroxides include, but are not limited to, lithium peroxide, sodium peroxide, potassium peroxide, magnesium peroxide, calcium peroxide, strontium peroxide, barium peroxide, and further adduct-type percarbonates such as Na2CO3·H2O2·0.5H2O, Na2CO4·H2O2, and 2Na2CO3·3H2O2. The present embodiment also encompasses etching solutions containing peroxides other than hydrogen peroxide. However, from the viewpoint of easy preparation, it is preferable to use hydrogen peroxide, for example, a commercially available aqueous hydrogen peroxide solution.

[0016] There are no particular restrictions on the concentrations of hydrogen peroxide and sulfuric acid in the etching solution, and hydrogen peroxide water and sulfuric acid may be mixed at a desired ratio. Preferably, the concentration of hydrogen peroxide is about 0.4 to 17% by mass, particularly about 0.5 to 15% by mass, especially about 0.7 to 13% by mass, and the concentration of sulfuric acid is about 0.5 to 66% by mass, particularly about 1 to 60% by mass, especially about 1.5 to 35% by mass. If the concentrations of hydrogen peroxide and sulfuric acid fall within this range, copper and copper alloys are easily oxidized and dissolved, which makes it possible to remove a seed layer and the like more efficiently. Note that the etching solution of the present embodiment becomes acidic, often strongly acidic, due to such a composition. The pH of the etching solution is, for example, 4 or less, more preferably 3 or less, and particularly preferably 2 or less.

[0017] <Halide ion> The etching solution of the present embodiment contains a halide ion together with hydrogen peroxide and sulfuric acid as described above. Examples of the halide ion (halogen ion) include fluoride ion (fluorine ion: F - ), chloride ion (chlorine ion: Cl - ), bromide ion (bromine ion: Br - ), iodide ion (iodine ion: I - ), and the like, but are not limited thereto. The etching solution may contain a plurality of types of halide ions. From the viewpoint of more effectively reducing defects caused by etching pits, chloride ions and / or bromide ions are preferred, and chloride ions are particularly preferred.

[0018] These halide ions may be prepared by mixing a hydrohalic acid such as hydrochloric acid or bromic acid into the etching solution, or may be prepared by mixing a halide salt. Examples of the halide salt include, but are not limited to, alkali metal salts such as sodium salts and potassium salts, ammonium salts, and halides of transition metals including copper salts. In consideration of cost and other factors, halide ion sources such as hydrochloric acid, sodium chloride, and potassium chloride are preferred.

[0019] (Halide ion concentration) The etching solution of this embodiment contains the above-mentioned halide ions at a concentration of 1000 ppm to 5000 ppm. If the halide ion concentration of the etching solution is within this range, the occurrence of etching pits can be reduced or prevented. From the viewpoint of stabilizing the etching solution, it is preferable that the halide ion concentration be, for example, 1100 ppm to 4900 ppm, more preferably 1200 ppm to 4800 ppm, more preferably 1300 ppm to 4700 ppm, and more preferably 1400 ppm to 4600 ppm, and especially preferably 1500 ppm to 4500 ppm. In the prior art, it has been considered that a lower halide ion concentration is better from the viewpoint of stabilizing the etching rate, and it is common to set it to around 0.01 to 3 ppm (for example, Patent Document 3).

[0020] Although this embodiment is not limited by any particular theory, it is thought that the etching solution is effective because the halide ions suppress uneven oxidation of the copper plating surface. The copper plating layer contains areas that are easily oxidized due to the presence of copper grain boundaries, etc., which can cause defects such as etching pits. Such uneven oxidation can be prevented, for example, by reducing the sulfuric acid concentration of the etching solution, but in that case, it may lead to a decrease in etching efficiency or fluctuations in the etching rate. When the etching solution contains a certain amount of halide ions, these act as inhibitors, and local oxidation of the copper plating layer can be suppressed. As a result, it is thought that etching pits can be reduced even with a solution composition that does not reduce etching efficiency.

[0021] <Solvent> In the etching solution of this embodiment, the solvent containing hydrogen peroxide, sulfuric acid, and halide ions is preferably water. In particular, aqueous solvents that minimize ionic impurities, such as deionized water, distilled water, pure water, and ultrapure water, are preferred. Optionally, the solution may also contain organic solvents such as alcohols (methanol, ethanol, etc.), ethers (tetrahydrofuran (THF), dioxane, various glimes, etc.), carbonate esters (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc.), nitrogen-containing solvents (acetonitrile, dimethylformamide (DMF), pyrrolidone, etc.), and sulfur-containing solvents (dimethyl sulfoxide (DMSO), etc.).

[0022] <Other ingredients> In addition to the components described above, the etching solution of this embodiment may optionally contain other components depending on the desired etching characteristics. Examples of optional components include, but are not limited to, nitrogen-containing heterocyclic compounds such as azoles, metal ions such as copper, iron, and nickel, bath stabilizers such as hydrogen peroxide stabilizers, pH adjusters, pH buffers, hydrogen generation inhibitors, dispersants, dispersion aids, emulsifiers, surfactants, brighteners, antioxidants, viscosity modifiers, wetting agents, conductivity imparters, dyes, and oxidizing agents other than hydrogen peroxide. For example, an etching solution containing azoles can make the copper plating surface smoother after etching. The presence of copper ions makes it easier to suppress fluctuations in the solution's performance during etching. The presence of hydrogen peroxide stabilizers improves the storage stability of the etching solution and reduces variations between etching processes. Some of these components will be described below.

[0023] (Nitrogen-containing heterocyclic compound) There are no particular restrictions on the nitrogen-containing heterocyclic compounds that can be added to the etching solution. Examples include, but are not limited to, azoles such as triazoles, tetrazoles, imidazoles, pyrazoles, and pentazoles, aromatic six-membered ring compounds such as diazines, triazines, and tetrazines, as well as aromatic compounds with seven or more members, and nitrogen-containing aliphatic compounds. It is also possible to use multiple types of nitrogen-containing heterocyclic compounds in combination. Etching solutions containing nitrogen-containing heterocyclic compounds can not only reduce etching pits but also, in some cases, make the surface of the workpiece smoother.

[0024] Among the above compounds, aromatic nitrogen-containing heterocyclic compounds, such as azoles and triazines, are preferred, with azoles being particularly preferred. This embodiment includes an etching solution further containing azoles. Among azoles, triazoles and tetrazoles are particularly preferred.

[0025] Known triazoles include 1,2,4-triazoles, 1,2,3-triazoles, 1,3,4-triazoles, and benzotriazoles, and any of these triazoles may be added to the etching solution. Multiple types can also be used in combination.

[0026] Specific examples of 1,2,4-triazoles include, in addition to 1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 3-amino-5-mercapto-1,2,4-triazole, 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, 1,2,4-triazole-3(5)-thione, 5-amino-1,2,4-triazole, and 1-methyl-1,2,4-thione. Examples include, but are not limited to, riazole, 1-ethyl-1,2,4-triazole, 3-bromo-1,2,4-triazole, 1-(4-chlorophenyl)-1,2,4-triazole, 4-formyl-1,2,4-triazole, 1-benzyl-1,2,4-triazole, 4,5-diphenyl-1,2,4-triazole, 4-(methylthio)-3,5-diamino-1,2,4-triazole, 4-(methylsulfonyl)-1,2,4-triazole, and 3,5-dichloro-1,2,4-triazole.

[0027] Specific examples of 1,2,3-triazoles include, but are not limited to, 1,2,3-triazole, 2-methyl-1,2,3-triazole, and 4-methyl-1,2,3-triazole.

[0028] Specific examples of 1,3,4-triazoles include, but are not limited to, 1,3,4-triazole, 1,3,4-triazole-2-thione, 2,4-diamino-1,3,4-triazole, and 1,3,4-triazole-5-carboxylic acid.

[0029] Specific examples of benzotriazoles include, but are not limited to, benzotriazole, 1-(hydroxymethyl)benzotriazole, 1-aminobenzotriazole, carboxybenzotriazole, 4-nitrobenzotriazole, 5-nitrobenzotriazole, 5-methylbenzotriazole, 4,5-dimethylbenzotriazole, 4-chlorobenzotriazole, 4,5-dichlorobenzotriazole, 5,6-dichlorobenzotriazole, 6-nitrobenzotriazole, 1-phenylbenzotriazole, 1-benzylbenzotriazole, 1-trifluoromethylbenzotriazole, 1-acetylbenzotriazole, etc.

[0030] Specific examples of tetrazoles include, but are not limited to, 5-amino-1H-tetrazole, 1H-tetrazole, 1-methyltetrazole, 5-methyltetrazole, 1,5-dimethyltetrazole, 1,5-diethyltetrazole, 1-phenyltetrazole, 5-phenyltetrazole, 1-phenyl-5-mercapto-1H-tetrazole, 5(3-aminophenyl)-1H-tetrazole, 5,5'-bi-1H-tetrazole, 5-carboxytetrazole, 5-nitrotetrazole, 5-hydroxymethyltetrazole, 5-ethyltetrazole, 5-benzyltetrazole, 1-propyltetrazole, 1-(2-chlorophenyl)tetrazole, and 2-phenyltetrazole.

[0031] Specific examples of imidazoles include, but are not limited to, imidazole, 2-aminoimidazole, 2-phenylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, 2-chloroimidazole, 2-methylimidazole, 2-butylimidazole, 1-benzylimidazole, 2-phenyl-4,5-dimethylimidazole, 1-acetylimidazole, 4,5-dihydroxyimidazole, and others.

[0032] Specific examples of triazines include, but are not limited to, 2,4-amino-6-methyltriazine, 2,4,6-trihydroxy-1,3,5-triazine, 2,4-diamino-6-phenyl-1,3,5-triazine, 2,4-dichloro-6-amino-1,3,5-triazine, 2-methyl-4,6-diphenyl-1,3,5-triazine, 2,4,6-trimethoxy-1,3,5-triazine, 3,5-diphenyl-1,2,4-triazine, and 5-amino-1,2,3-triazine.

[0033] Among these, 1,2,4-triazole, 1,2,3-triazole, benzotriazole, 3,5-diamino-1,2,4-triazole, 3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 1H-tetrazole, and 5-amino-1H-tetrazole are particularly preferred. These azoles, when combined with halide ions, can exhibit not only a significant reduction in etching pits but also a remarkable smoothing effect, making them suitable as additives for etching solutions.

[0034] The etching solution of this embodiment contains the above-mentioned nitrogen-containing heterocyclic compound in an amount preferably of about 2% by mass or less, for example, 0.008 to 1.7% by mass, more preferably 0.012 to 1.5% by mass, and even more preferably about 0.02 to 1.3% by mass. If the concentration of the nitrogen-containing heterocyclic compound is within this range, it is possible to achieve a better balance between suppressing the generation of etching pits in the copper plating layer after etching and improving surface smoothness. Furthermore, it becomes possible to further improve seed removal and wiring cross-sectional shape.

[0035] (copper ions) The etching solution of this embodiment may further contain metal ions such as copper ions. As etching progresses, the seed layer and / or plating layer dissolve, causing the copper concentration in the solution to gradually increase. However, by including a certain concentration or higher of copper ions in advance, minor changes in the solution's performance as the process progresses can be suppressed. This embodiment further includes an etching solution containing copper ions. Examples of copper ion sources include, but are not limited to, copper sulfate, copper chloride, copper acetate, copper oxide, and copper hydroxide. The copper dissolved in the solution during etching can also be used as a copper ion source. Among the above, copper sulfate, copper chloride, and copper oxide are preferred as external copper ion sources, with copper sulfate being particularly preferred.

[0036] The copper ion concentration in the etching solution is preferably 15% by mass or less, for example, within the range of 0.4 to 10% by mass, and particularly preferably within the range of 0.8 to 8% by mass.

[0037] (Hydrogen peroxide stabilizer) This embodiment also further includes an etching solution containing a hydrogen peroxide stabilizer. There are no particular limitations on the hydrogen peroxide stabilizer. Examples include, but are not limited to, compounds having sulfonic acid groups, compounds having hydroxyl groups such as alcohols and phenols, compounds having amino groups, carboxylic acids, and derivatives thereof. The functional group may have multiple types of functional groups such as sulfonic acid groups and hydroxyl groups, and the functional group may form a salt with a metal ion or an ammonium ion. Compounds having sulfonic acid groups and alcohols are particularly preferred.

[0038] Specific examples of compounds having a sulfonic acid group include, but are not limited to, benzenesulfonic acid or its salts (sodium benzenesulfonate, potassium benzenesulfonate, ammonium benzenesulfonate), phenolsulfonic acid or its salts (sodium phenolsulfonate, potassium phenolsulfonate, ammonium phenolsulfonate), cresolsulfonic acid or its salts (sodium cresolsulfonate, etc.), ligninsulfonic acid or its salts (sodium ligninsulfonate, calcium ligninsulfonate, ammonium ligninsulfonate, magnesium ligninsulfonate, etc.).

[0039] Specific examples of alcohols include methanol, ethanol, n-propanol, isopropanol, butanol, t-butanol, isobutanol, phenoxyethanol, 2-methyl-2-propanol, pentanol, isoamyl alcohol, hexanol, 2-ethyl-1-hexanol, benzyl alcohol, lauryl alcohol, and polyhydric alcohols such as glycerin (glycerol), diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, and 2,3-butanediol, but are not limited to these.

[0040] Specific examples of phenols include, but are not limited to, 2,4,6-tris(dimethylaminomethyl)phenol and phenol derivatives such as the aforementioned phenoxyethanol.

[0041] Specific examples of compounds containing an amino group include, but are not limited to, naphthalenediamine, aniline, naphthylamine, toluidine, anisidine, chloroaniline, nitroaniline, phenylenediamine, diphenylamine, and 2,4-diaminotoluene.

[0042] Specific examples of carboxylic acids and their derivatives include, but are not limited to, 2-hydroxybenzoic acid (salicylic acid), 5-sulfosalicylic acid, acetylsalicylic acid, methyl-p-aminobenzoic acid, p-hydroxybenzoic acid, and their salts, as well as derivatives such as phenyl salicylate, methyl salicylate, ethyl salicylate, propyl salicylate, isoamyl salicylate, salicylamide, and salicylaldehyde.

[0043] Among the hydrogen peroxide stabilizers mentioned above, phenolsulfonic acid, benzenesulfonic acid, and their salts, such as sodium phenolsulfonate, sodium benzenesulfonate, n-propanol, t-butanol, and phenoxyethanol, are particularly preferred.

[0044] The concentration of the hydrogen peroxide stabilizer in the etching solution is preferably 2% by mass or less, for example, 0.008 to 1.7% by mass, more preferably 0.012 to 1.5% by mass, and even more preferably about 0.02 to 1.3% by mass.

[0045] (Oxidizing agent) The etching solution of this embodiment may contain oxidizing agents other than hydrogen peroxide and peroxides. Examples include, but are not limited to, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; metal ions or compounds that act as oxidizing agents such as iron chloride, iron sulfate, iron nitrate, chromate ions, and manganate ions; and inorganic oxidizing agents such as periodic acid and its salts.

[0046] [Preparation of etching solution] The etching solution of this embodiment can be prepared using conventional methods from the above-mentioned components, and the details can be appropriately determined by considering the composition and amount of each component. For example, a concentrated solution containing hydrogen peroxide, sulfuric acid, halide ions, and other additives may be prepared in advance and diluted immediately before use. Since the etching solution of this embodiment can be adjusted to the desired composition and concentration using such general methods, it can be flexibly operated to meet the needs of the manufacturing process and the site of use.

[0047] [Applications of etching solutions] The etching solution of this embodiment is less likely to cause defects such as etching pits during the etching process. Therefore, it is useful for etching seed layers of copper or copper alloys, and even for etching plating layers, such as copper plating layers. In particular, it is suitable for removing seed layers in the semi-additive method. It can also be used for half-etching, which partially removes a portion of the seed layer or plating layer by a predetermined thickness, as well as for forming fine patterns on electronic substrates, removing unwanted copper on multilayer substrates, or fine-tuning the plating layer when forming via holes. In addition to these, it can be applied to a variety of other uses, such as surface roughening before plating or bonding processes, and pattern correction in rewiring processes, and the scope of application is not limited to those mentioned above. This embodiment includes the etching solution described above for removing seed layers of copper or copper alloys.

[0048] The etching solution of this embodiment can reduce defects such as etching pits in the etching of any copper and copper alloy. Furthermore, various types of copper and copper alloy layers, such as copper sulfate plating layers, electroless copper plating layers, micro-thin plating layers, and even rolled copper foil layers, can be etched with almost the same efficiency. Therefore, the etching solution of this embodiment can be used to etch any copper or copper alloy layer.

[0049] In this embodiment, the etching target is a seed layer containing copper or a copper alloy, but the material can be any metallic material containing copper. Furthermore, the target can also be an object that has other types of metal members along with the copper layer, etc. For example, the etching solution of this embodiment may be applied to an object that has a layer containing copper or a copper alloy along with a metallic member such as a titanium layer.

[0050] The etching solution of this embodiment is also superior in terms of etching stability. In conventional etching solutions, the halide ion concentration can fluctuate significantly due to the elution of halides from the material to be etched or the contamination of halides from the ambient atmosphere, resulting in fluctuations in the etching rate. On the other hand, the etching solution of this embodiment, which contains 1000 to 5000 ppm of halide ions, is less prone to changes in halide ion concentration, and as a result, fluctuations in etching efficiency are suppressed. The etching solution of this embodiment may also contain nitrogen-containing heterocyclic compounds such as azoles, if desired, or may not contain them, to make the surface of the plated layer of copper or copper alloy smoother. Furthermore, the presence of hydrogen peroxide stabilizers, etc., can simplify the control of the solution concentration during the etching process. The following describes a process using the etching solution of this embodiment, particularly the etching of the seed layer.

[0051] ≪2. Etching Process≫ This embodiment is an etching method in which the above-described etching solution is brought into contact with the surface of a seed layer made of copper or a copper alloy. It is also a method for manufacturing an electronic substrate, which includes the step of etching the seed layer made of copper or a copper alloy using the above-described etching solution.

[0052] There are no particular restrictions on the methods and conditions of the etching process; a general etching process can be performed under conventional conditions, depending on the type of electronic substrate to be etched and the material of the seed layer (or plating layer) to be etched.

[0053] Specifically, the etching temperature can be, for example, 10 to 60°C, more particularly 15 to 50°C, and especially 20 to 40°C. Alternatively, the etching process may be carried out by contacting the seed layer with the etching solution using methods such as immersion, spraying, or spin coating. When etching by immersion, the processing time should be, for example, 20 to 1500 seconds. When etching by spraying, the spray pressure should be, for example, 0.05 to 0.20 MPa, and the processing time should be 15 to 1500 seconds.

[0054] Electronic circuit boards manufactured using this etching process have reduced etching pit defects, and the surface smoothness of the copper or copper alloy plating layer is often improved. As a result, wiring breakage and transmission loss are less likely to occur.

[0055] <Evaluation Method> Furthermore, defects in electronic circuit boards can be evaluated using a confocal microscope or similar equipment. For example, the frequency of etching pits can be evaluated by measuring the number of etching pits on the confocal microscope's observation screen and calculating the number of etching pits per unit area. In addition, the smoothness of the surface can be evaluated based on the arithmetic mean roughness (Ra) or root mean square roughness (Rq) in accordance with JIS B0601:2013, or the interface area ratio (Sdr) measured according to ISO 25178.

[0056] <Manufacturing of electronic circuit boards> If the method of this embodiment described above is incorporated into a method for manufacturing an electronic substrate, for example, which includes etching a copper (or copper alloy) plating layer, it is possible to manufacture an electronic substrate, such as a printed circuit board, that is free from electrical connection failures due to pitting corrosion or excessive corrosion. This method for manufacturing an electronic substrate can be applied not only to the semi-additive method but also to other methods such as the build-up method. [Examples]

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to these descriptions.

[0058] Examples 1-4 and Comparative Examples 1-4 Etching solutions of various compositions were prepared, and copper-plated substrates prepared separately were etched using these solutions. The degree of defects such as etching pits was then evaluated. The copper-plated substrates were made by applying electrolytic copper plating to a target thickness of 20 μm on a copper-clad laminate (CCL) board with a thickness of 0.4 mm and dimensions of 510 x 405 mm, and then cutting them into pieces of approximately 50 x 50 mm. The copper plating was performed using an electrolytic copper plating solution manufactured by JCU at a current density of 1.5 A / dm². 2 The procedure was performed at room temperature for 45 minutes.

[0059] (Evaluation method) Each evaluation was conducted as follows: • Frequency of etching pit occurrence (pit occurrence rate): The number of etching pits was measured by observing the substrate after etching with a confocal microscope (Keyence VK-X250) (magnification 50x). This was divided by the observation area to obtain the number of etching pits per unit area (pits / cm²). 2 The following values ​​were calculated and evaluated based on the criteria shown in Table 1 below. • Roughness (smoothness): The arithmetic mean roughness (Ra: in μm) was determined from images taken with a confocal microscope (magnification 50x) in accordance with JIS B0601:2013 and evaluated based on the criteria shown in Table 2.

[0060] [Table 1]

[0061] [Table 2]

[0062] (Preparation of etching solution) The etching solutions with the compositions shown in Table 3 below were prepared using hydrogen peroxide, sulfuric acid, hydrochloric acid, etc. Each etching solution was prepared by adding its respective component to purified water and stirring at room temperature. The following products were used as raw material reagents for the etching solutions shown in Table 3 and beyond.

[0063] (Materials and reagents used) • Hydrogen peroxide: Manufactured by ADEKA Corporation • Sulfuric acid: Manufactured by Nissan Chemical Corporation ·Copper sulfate (copper ion source): Manufactured by JX Metals • Hydrochloric acid (halide ion source): Manufactured by Toagosei Co., Ltd. 3,5-diamino-1,2,4-triazole, 5-amino-1H-tetrazol, 1H-tetrazol, 3-amino-1,2,4-triazole, 1,2,3-triazole, 1,2,4-triazole, benzotriazole, 2-aminoimidazole (sulfate), 3-mercapto-1,2,4-triazole, phenoxyethanol: Manufactured by Tokyo Chemical Industry Co., Ltd. • Sodium phenolsulfonate (dihydrate), sodium benzenesulfonate (monohydrate), n-propanol, t-butanol, sodium bromide (bromide ion source): Manufactured by Fujifilm Wako Pure Chemical Industries.

[0064] (Etching test) The copper-plated substrate described above was immersed in 10% dilute sulfuric acid at room temperature for 10 seconds. Next, the copper-plated substrate was immersed in the etching solution prepared above at 30°C, and the etching time was adjusted to etch the substrate to a depth of 5 μm. After etching, it was rinsed with water and dried. The frequency of etching pits and surface smoothness of the dried copper-plated substrate were evaluated based on the above indicators. The evaluation results, along with the composition of the etching solution, are shown in Table 3 below.

[0065] [Table 3]

[0066] The results shown in Table 3 clearly demonstrate that an etching solution containing 1000 ppm or more of chloride ions, along with hydrogen peroxide and sulfuric acid, can significantly reduce and prevent etching pits in the copper plating layer. On the other hand, when the chloride ion concentration was less than 1000 ppm, etching pitting problems occurred frequently, highlighting the importance of a halide ion concentration of 1000 ppm or more. Furthermore, while etching solutions containing copper ions can suppress changes in solution performance as the process progresses, as described above, it was also found that they achieve almost the same effect in suppressing etching pits as those without copper ions. In addition, no particular difficulties occurred during the etching operation in Examples 1 to 4.

[0067] Examples 5-9 and Comparative Examples 5-10 Etching solutions were prepared with compositions further containing azoles and / or hydrogen peroxide stabilizers (stabilizers) as optional components, and the same procedure as in Example 1 was performed. The evaluation results, along with the etching solution composition and data from Examples 3 and 4, are shown in Table 4 below.

[0068] [Table 4]

[0069] The results shown in Table 4 clearly demonstrate that the significant reduction and prevention of etching pits by increasing the chloride ion concentration to 1000 ppm or higher is also observed when additives such as azoles are included. Furthermore, it was shown that etching solutions containing azoles along with chloride ions at a concentration of 1000 ppm or higher not only reduce etching pits but also improve surface roughness, resulting in a smoother copper plating layer surface. Even with etching solutions that did not contain azoles, no significant roughening of the copper plating layer surface occurred in Examples 9 and above, where the chloride ion concentration was 2000 ppm or higher. Additionally, the results from Examples 8-9 and 3-4 indicate that smoothness can be improved by adding a hydrogen peroxide stabilizer to the etching solution.

[0070] Examples 10-31, Comparative Examples 11-21 The same procedure as in Example 1 was performed by changing the composition of the etching solution. The evaluation results, along with the composition of the etching solution, are shown in Tables 5 to 7 below.

[0071] [Table 5]

[0072] [Table 6]

[0073] [Table 7]

[0074] The data shown in Tables 5-7 demonstrates that even when the type of azoles or hydrogen peroxide stabilizer is changed, or when the halide ions in the etching solution are replaced from chloride ions to bromide ions, maintaining a halide ion concentration of 1000 ppm or higher significantly reduces etching pits. Furthermore, it became clear that by incorporating an appropriate amount of azoles, a better balance can be achieved between reducing etching pits and improving surface smoothness.

[0075] As described above, the present invention provides an etching solution that is less likely to cause etching pit defects when etching copper or copper alloys, and furthermore, can provide a copper plating layer surface with excellent smoothness and good etching operability.

Claims

1. It contains hydrogen peroxide, sulfuric acid, and halide ions. The halide ion is a chloride ion and / or a bromide ion. The concentration of the halide ions is 1100 ppm or more and 5000 ppm or less. Etching solution for copper or copper alloys.

2. The etching solution according to claim 1, wherein the concentration of the halide ions is 1200 ppm or more and 4800 ppm or less.

3. The etching solution according to claim 1, further comprising azoles.

4. The etching solution according to claim 1, wherein the halide ion is a chloride ion.

5. The etching solution according to claim 1, further containing copper ions.

6. The etching solution according to claim 1, further comprising a hydrogen peroxide stabilizer.

7. An etching solution according to any one of claims 1 to 6 for removing a seed layer of copper or a copper alloy.

8. An etching method comprising contacting the etching solution described in any one of claims 1 to 6 with the surface of a seed layer of copper or a copper alloy.

9. A method for manufacturing an electronic substrate, comprising the step of etching a copper or copper alloy seed layer using an etching solution described in any one of claims 1 to 6.

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