Etching liquid, replenishing liquid, and copper wiring forming method

Abstract

This copper etching liquid comprises an acid, an oxidative metal ion source, a nitrogen atom-containing polymer, and water, wherein the concentration of the nitrogen atom-containing polymer is 1 g / L or more, and the content ratio of the nitrogen atom-containing polymer in components of the etching liquid excluding the acid, oxidative metal ion source, and water is 10% by mass or more. The copper etching liquid can form copper wiring having excellent linearity while having a sufficient wiring width on a substrate with an etching resist patterned on a copper layer having a thin film thickness.

Description

Etching Solution, Replenishing Solution, and Method for Forming Copper Wiring

[0001] The present invention relates to a copper etching solution, its replenishing solution, and a method for forming copper wiring.

[0002] In the production of printed wiring boards, when forming a copper wiring pattern on a substrate (etching object) with an etching resist patterned on a copper layer by the photolithography etching method, an etching solution containing an acid, an oxidizing metal ion, water, etc. is used (for example, Patent Documents 1 - 3).

[0003] Japanese Patent Application Laid-Open No. 2021 - 116449, Japanese Patent Application Laid-Open No. 2009 - 221596, Japanese Patent Application Laid-Open No. 2007 - 180172

[0004] On the other hand, in the production of a copper mesh film or antenna film of a touch sensor, rather than the above-mentioned printed wiring board, since the copper layer has a thin film thickness, it is possible to make the copper pattern thinner and reduce the visibility of the wiring. Therefore, a copper layer with a thin film thickness is required as an etching object. When forming a copper wiring pattern using the etching solution specifically disclosed in the above patent documents for such a copper layer with a thin film thickness, the etching rate is fast, and even if the concentration of the etching solution, mechanical conditions, etc. are adjusted, it is very difficult to control the finish of the copper wiring. Also, there is a problem that gouges, etc. occur on the side surface of the copper wiring, so-called linearity of the copper wiring decreases.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a copper etching solution, its replenishing solution, and a method for forming copper wiring that can form copper wiring having excellent linearity while having a sufficient wiring width with respect to a substrate having an etching resist patterned on a copper layer with a thin film thickness.

[0006] The present invention relates to a copper etching solution containing an acid, an oxidizing metal ion source, a nitrogen atom-containing polymer, and water, wherein in the etching solution, the concentration of the nitrogen atom-containing polymer is 1 g / L or more, and the content ratio of the nitrogen atom-containing polymer in the components excluding the acid, the oxidizing metal ion source, and the water is 10% by mass or more.

[0007] Furthermore, the present invention relates to a copper etching solution in which the nitrogen atom-containing polymer is preferably a linear polymer.

[0008] Furthermore, the present invention relates to a copper etching solution which is preferably used for copper layers having a thickness of 5 μm or less.

[0009] Furthermore, the present invention relates to a replenishment solution to be added to the etching solution when the copper etching solution is used continuously or repeatedly, the replenishment solution being an aqueous solution containing at least the nitrogen atom-containing polymer.

[0010] Furthermore, the present invention relates to a method for forming copper wiring by etching the portion of a copper layer that is not covered with an etching resist, and more particularly to a method for forming copper wiring by etching using the copper etching solution.

[0011] The copper etching solution of the present invention contains an acid, an oxidizing metal ion source, a specific amount of nitrogen atom-containing polymer, and water. The nitrogen atom-containing polymer inhibits the etching process, thereby reducing the etching rate. However, because the amount of nitrogen atom-containing polymer is specific, the etching rate does not decrease excessively. Furthermore, it is presumed that the polymer is mildly adsorbed to copper. Therefore, on a substrate with a thin copper layer on which an etching resist has been patterned, copper wiring with sufficient wiring width and excellent linearity can be formed.

[0012] <Copper Etching Solution> The copper etching solution of the present invention comprises an acid, an oxidizing metal ion source, a nitrogen atom-containing polymer, and water. In the etching solution, the concentration of the nitrogen atom-containing polymer is 1 g / L or more, and the content of the nitrogen atom-containing polymer in the components excluding the acid, the oxidizing metal ion source, and the water is 10% by mass or more. In the copper etching solution of the present invention, "copper" may be made of copper or a copper alloy.

[0013] <Acid> The acid can be appropriately selected from inorganic acids and organic acids. Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and hydrobromic acid. Examples of organic acids include formic acid, acetic acid, oxalic acid, maleic acid, benzoic acid, and glycolic acid. Among the acids, hydrochloric acid is preferred from the viewpoint of etching rate stability and copper dissolution stability. At least one acid may be used, and two or more may be used in combination.

[0014] The concentration of the acid is preferably 7 to 180 g / L, more preferably 12 to 110 g / L, and even more preferably 18 to 70 g / L. When the acid concentration is 7 g / L or higher, the etching rate increases, allowing copper to be etched quickly. When the acid concentration is 180 g / L or lower, the solubility stability of copper is maintained, and deterioration of the working environment can be suppressed.

[0015] <Oxidizing Metal Ion Source> The oxidizing metal ion source can be incorporated into a copper etching solution to include oxidizing metal ions in the etching solution. The oxidizing metal ion can be any metal ion capable of oxidizing metallic copper, such as cupric ions or ferric ions. For example, when using a cupric ion source as the oxidizing metal ion source, specific examples include copper chloride, copper sulfate, copper bromide, copper salts of organic acids, and copper hydroxide. For example, when using a ferric ion source as the oxidizing metal ion source, specific examples include iron chloride, iron bromide, iron iodide, iron sulfate, iron nitrate, and iron salts of organic acids. From the viewpoint of etching rate stability, it is preferable to use cupric ions as the oxidizing metal ions. Only one type of oxidizing metal ion source is required, and two or more types can be used in combination.

[0016] The concentration of the oxidizing metal ion source is preferably 8 to 330 g / L, more preferably 13 to 260 g / L, and even more preferably 142 to 190 g / L. When the concentration of the oxidizing metal ion source is 8 g / L or higher, the etching rate increases, allowing copper to be etched quickly. When the concentration of the oxidizing metal ion source is 330 g / L or lower, the solubility stability of copper is maintained.

[0017] <Nitrogen Atom-Containing Polymers> The nitrogen atom-containing polymers are not particularly limited and may be polymers containing nitrogen atoms in the main chain or polymers having nitrogen atoms in the side chain functional groups (pendant groups). Examples of structures include linear polymers and network polymers. Examples of these polymers include polyalkyleneimines; polymers containing N-vinyl-type monomer units such as N-vinylpyrrolidone, N-vinyllactam, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholindione, and N-vinyl chain amides; and polyallylamines such as allylamine, diallylamine, methyldiallylamine, diallyldimethylammonium chloride, N-methylallylamine, N-carbomethoxyallylamine, N-amidoallylamine, and N-vinyl-β-alanine. Furthermore, polymers containing nitrogen atom-containing structures having vinyl groups and / or (meth)acrylic groups as monomer units include 4-vinylpyridine, 2-isopropenyl-2-oxazoline, acrylamide, 2-(dimethylamino)ethyl methacrylate, 2-(methacryloyloxy)ethyltrimethylammonium chloride, and N-methacryloyloxyethyl N,N-dimethylammonium-α-N-methylcarboxybetaine. More specific polymers include polyvinylpyrrolidone, dimethylamine-ethylenediamine-epichlorohydrin copolymer, vinylpyrrolidone N,N-dimethylaminoethyl methacrylate copolymer diethyl sulfate, allylamine polymer, methyldiallylamine hydrochloride polymer, oxazoline group-containing polymer, amine-epichlorohydrin condensate, and poly(4-vinylpyridine). Among these, polymers having nitrogen atoms in a cyclic structure, such as polyalkyleneimines and polymers containing N-vinyl type monomer units, are preferred, and linear polymers are preferred structurally.

[0018] In the copper etching solution, the concentration of the nitrogen atom-containing polymer is 1 g / L or more. In the copper etching solution, the concentration of the nitrogen atom-containing polymer is preferably 1.2 g / L or more, more preferably 1.5 g / L or more, and even more preferably 2 g / L or more, from the viewpoint of reducing the etching rate, and from the viewpoint of preventing the etching rate from becoming too slow, it is preferably 50 g / L or less, more preferably 20 g / L or less, and even more preferably 10 g / L or less.

[0019] In the copper etching solution, the nitrogen atom-containing polymer is present in the components excluding the acid, the oxidizing metal ion source, and the water at a rate of 10% by mass or more. In the copper etching solution, the nitrogen atom-containing polymer is present in the components excluding the acid, the oxidizing metal ion source, and the water at a rate of 15% by mass or more, and more preferably 20% by mass or more, from the viewpoint of sufficiently reducing the etching rate.

[0020] The copper etching solution of the present invention may use additives used in conventional etching solutions. Examples of such additives include heteroaromatic compounds having a nitrogen atom as a heteroatom constituting the ring, such as imidazole compounds, pyrazole compounds, triazole compounds, and tetrazole compounds; aliphatic heterocyclic compounds having a nitrogen atom as a heteroatom constituting the ring, such as pyrrolidine compounds, piperidine compounds, piperazine compounds, homopiperazine compounds, and hexahydro-1,3,5-triazine compounds; (non-heterocyclic) aromatic compounds such as phenols and aromatic amines; aliphatic acyclic compounds such as amine compounds and ether compounds; cationic surfactants, anionic surfactants, amphoteric surfactants, etc. When using such additives, their concentration is usually about 0.001 to 10 g / L.

[0021] The copper etching solution can be easily prepared by dissolving each of the above components in water. Preferably, the water used is water from which ionic substances and impurities have been removed; for example, deionized water, pure water, or ultrapure water are preferred.

[0022] The copper etching solution may be prepared by mixing each component to a predetermined concentration at the time of use, or a concentrated solution may be prepared and diluted immediately before use. The method of using the copper etching solution is not particularly limited, but to obtain a stable finish, it is preferable to etch using a spray as described later. Furthermore, there are no particular restrictions on the temperature of the etching solution during use, but it is preferable to use it at 20 to 55°C in order to process at an appropriate etching rate.

[0023] The replenishment solution of the present invention is a replenishment solution added to the copper etching solution when the copper etching solution is used continuously or repeatedly, and is an aqueous solution containing at least the nitrogen atom-containing polymer. By adding the replenishment solution, the component ratios of the copper etching solution are properly maintained, and the effects of the copper etching solution of the present invention described above can be stably maintained.

[0024] Furthermore, the replenishment solution may contain an acid such as hydrochloric acid. The replenishment solution may also contain an oxidizing metal ion source such as cupric chloride. In addition, the replenishment solution may contain other components to be added to the etching solution. Note that these components that may be included in the replenishment solution can also be added directly to the copper etching solution of the present invention when using the copper etching solution of the present invention continuously or repeatedly, without being included in the replenishment solution.

[0025] The present invention relates to a method for forming copper wiring, characterized in that the etching is performed using the copper etching solution of the present invention, in which the portion of the copper layer not covered with an etching resist is etched. Furthermore, in a copper wiring formation step employing the copper wiring formation method of the present invention, when the copper etching solution of the present invention is used continuously or repeatedly, it is preferable to etch while adding the replenishment solution.

[0026] In the copper wiring formation method of the present invention, it is preferable to spray the copper etching solution onto the portion of the copper layer that is not covered with etching resist. This is because a stable finish can be obtained. When spraying, the nozzle is not particularly limited, and a fan-shaped nozzle, a full-cone nozzle, a two-fluid nozzle, etc., can be used.

[0027] When etching by spray, the spray pressure is preferably 0.04 MPa or higher, and more preferably 0.08 MPa or higher. A spray pressure of 0.04 MPa or higher ensures a stable finish. However, from the viewpoint of preventing damage to the etching resist, the spray pressure is preferably 0.40 MPa or lower.

[0028] The copper etching solution of the present invention is suitable for applications such as copper mesh films and antenna films for touch sensors because it exhibits excellent linearity while maintaining sufficient wiring width on a substrate on which an etching resist has been patterned on a thin copper layer. When applied to such applications, the thickness of the copper layer is preferably 5 μm or less, and more preferably 2 μm or less.

[0029] Next, embodiments of the present invention will be described together with comparative examples. It should be noted that the present invention is not limited to the embodiments described below.

[0030] Etching solutions with the compositions shown in Table 1 were prepared, etching was performed under the conditions described later, and each item was evaluated using the evaluation method described later. In each etching solution with the compositions shown in Table 1, the acid is hydrochloric acid, the oxidizing metal ion source is cupric chloride dihydrate, and the remainder is deionized water. The concentrations of hydrochloric acid shown in Table 1 are the concentrations as hydrogen chloride, and the concentrations of the oxidizing metal ion source are the concentrations as cupric chloride dihydrate. When the concentration of cupric chloride dihydrate is 439.4 g / L, the concentration of copper ions is 158.9 g / L.

[0031] (Test substrate used) A copper / polyimide laminated film (manufactured by Oike Kogyo Co., Ltd.) with a copper layer thickness of 0.4 μm was prepared, and an etching resist pattern was formed on this copper layer by photolithography (resist agent: manufactured by Asahi Kasei Co., Ltd.). The etching resist pattern was fabricated to have a grid-like pattern region with a thickness of approximately 7 μm and a line / space ratio of 15 μm / 500 μm.

[0032] (Etching conditions) Etching was performed using a full-cone nozzle (Ikeuchi Co., Ltd., product name "INVV020") under the following conditions: spray pressure 0.12 MPa, processing temperature 30°C, oscillation width 120 mm, oscillation speed 6 sec / cycle, nozzle-substrate distance 50 mm, and processing time 12 seconds. After etching, the substrate was washed with water and dried, and the following evaluation was performed.

[0033] (Evaluation) Each etched test substrate was immersed in acetone for 20 seconds (or in a 3% by mass sodium hydroxide aqueous solution for 60 seconds) to remove the etching resist. The copper pattern was then observed according to the following evaluation.

[0034] <Evaluation of Wiring Formation> Wiring formation was evaluated by observing the material at a magnification of 2000x using a metallurgical microscope (VHX-7000 manufactured by KEYENCE). A pass rating ("○") was given if a grid-like copper wiring pattern was formed, and a fail rating ("×") was given if the copper wiring was missing.

[0035] <Evaluation of Wiring Width> The wiring width was evaluated by observing it at a magnification of 2000x using a metal microscope (KEYENCE VHX-7000). The wiring width was measured at 10 arbitrary locations, and if the average was 7.0um or more, it was judged as a pass ("○") because it had an etching rate reduction effect. Anything less was judged as a fail ("×").

[0036] <Evaluation of Linearity> Linearity was evaluated by observing the wires at a magnification of 2000x using a metallurgical microscope (KEYENCE VHX-7000). The width of 10 arbitrary wiring points was measured, and the standard deviation was calculated. A standard deviation of 0.80 or less was considered a pass ("○"), and anything exceeding that was considered a fail ("×").

[0037]

[0038] In Table 1, the nitrogen atom-containing polymers are as follows:

[0039] As a result of the above, it can be seen that the copper etching solutions of each example exhibit excellent linearity while maintaining sufficient wiring width on a substrate in which an etching resist pattern has been formed on a thin copper layer. The copper etching solution of Comparative Example 3 corresponds to the copper etching solution of Example 2 of Patent Document 1, the copper etching solution of Comparative Example 4 corresponds to the copper etching solution of Example 7 of Patent Document 2, and the copper etching solution of Comparative Example 5 corresponds to the copper etching solution of Example 9 of Patent Document 3.

Claims

1. A copper etching solution comprising an acid, an oxidizing metal ion source, a nitrogen atom-containing polymer, and water, wherein the concentration of the nitrogen atom-containing polymer in the etching solution is 1 g / L or more, and the content ratio of the nitrogen atom-containing polymer in the components excluding the acid, the oxidizing metal ion source, and the water is 10% by mass or more.

2. The copper etching solution according to claim 1, characterized in that the nitrogen atom-containing polymer is a linear polymer.

3. The copper etching solution according to claim 1, characterized in that it is used on a copper layer having a thickness of 5 μm or less.

4. A replenishment solution to be added to the etching solution when the copper etching solution described in claim 1 or 2 is used continuously or repeatedly, characterized in that it is an aqueous solution containing at least the nitrogen atom-containing polymer.

5. A method for forming copper wiring, comprising etching a portion of a copper layer that is not covered with an etching resist, characterized in that the etching is performed using the copper etching solution described in claim 1 or 2.

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