Etching solution, replenishment solution, and method for forming copper wiring

Abstract

To provide a copper etching solution and its replenishment solution, as well as a method for forming copper wiring, that can form copper wiring with sufficient wiring width and excellent linearity on a substrate on which an etching resist pattern has been formed on a thin copper layer. [Solution] 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.

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, in the production of a copper mesh film or an antenna film of a touch sensor, instead of the above-mentioned printed wiring board, since the thin copper layer enables the thinning of the copper pattern and the visibility of the wiring can be reduced, a thin copper layer 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 thin copper layer, 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, and there is a problem that burrs, etc. occur on the side surface of the copper wiring, so-called, the linearity of the copper wiring deteriorates.

[0005] This invention has been made in view of the above circumstances, and aims to provide a copper etching solution and its replenishment solution, as well as a method for forming copper wiring, that can form copper wiring with sufficient wiring width and excellent linearity on a substrate on which an etching resist has been patterned on a thin copper layer. [Means for solving the problem]

[0006] The present invention relates to 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.

[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. [Effects of the Invention]

[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. [Modes for carrying out the invention]

[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 for rapid etching of copper. 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] <Source of oxidizing metal ions> 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. Furthermore, 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 polymer> The nitrogen atom-containing polymer is not particularly limited and may be either a polymer containing nitrogen atoms in the main chain or a polymer 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 methacrylic acid 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, from the viewpoint of reducing the etching rate, the concentration of the nitrogen atom-containing polymer is preferably 1.2 g / L or more, more preferably 1.5 g / L or more, still more preferably 2 g / L or more, 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 still more preferably 10 g / L or less.

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

[0020] Additives used in conventional etching solutions may be used in the copper etching solution of the present invention. Examples of the additives include heteroaromatic compounds having a nitrogen atom as a heteroatom constituting a ring, such as imidazole compounds, pyrazole compounds, triazole compounds, and tetrazole compounds; aliphatic heterocyclic compounds having a nitrogen atom as a heteroatom constituting a ring, such as pyrrolidine compounds, piperidine compounds, piperazine compounds, homopiperazine compounds, and hexahydro-1,3,5-triazine compounds; aromatic compounds (not heterocyclic) such as phenols and aromatic amines; aliphatic acyclic compounds such as amine compounds and ether compounds; cationic surfactants, anionic surfactants, and amphoteric surfactants. When the additives are used, the concentration is usually about 0.001 to 10 g / L.

[0021] The copper etching solution can be easily prepared by dissolving the above components in water. As the water, water from which ionic substances and impurities have been removed is preferred, and for example, ion-exchanged water, pure water, ultrapure water, etc. are preferred.

[0022] The copper etching solution may be formulated so that each component has a predetermined concentration during 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 in order to obtain a stable finish, it is preferable to perform etching using a spray as described below. Also, the temperature of the etching solution during use is not particularly limited, but it is preferably used at 20 to 55°C in order to perform treatment at an appropriate etching rate.

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

[0024] Further, the replenisher may contain an acid such as hydrochloric acid. Further, the replenisher may contain an oxidizing metal ion source such as cupric chloride. Further, in addition to the above components, other components to be added to the etching solution may be blended in the replenisher. Note that the components that may be contained in these replenishers may be directly added to the copper etching solution of the present invention when the copper etching solution of the present invention is used continuously or repeatedly, instead of being contained in the replenisher.

[0025] The method for forming a copper wiring of the present invention is a method for forming a copper wiring for etching a portion not covered with an etching resist of a copper layer, and is characterized by etching using the copper etching solution of the present invention described above. Also, in the copper wiring forming step employing the method for forming a copper wiring of the present invention, when the copper etching solution of the present invention is used continuously or repeatedly, it is preferable to perform etching while adding the replenisher.

[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. [Examples]

[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 board 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 produced had a thickness of approximately 7 μm and a grid-like pattern region with 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 rinsed 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 using the following evaluation method.

[0034] <Evaluation of wiring formability> Wiring formation was evaluated by observing the material at 2000x magnification using a metallurgical microscope (KEYENCE VHX-7000). 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 2000x magnification using a metallurgical microscope (KEYENCE VHX-7000). The wiring width was measured at 10 arbitrary locations, and if the average was 7.0um or more, it was considered a pass ("○") because it had an etching rate reduction effect. Anything less was considered a fail ("×").

[0036] <Evaluation of linearity> Linearity was evaluated by observing the wires at 2000x magnification 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 ("○"), while anything exceeding that was considered a fail ("×").

[0037] [Table 1]

[0038] In Table 1, the nitrogen atom-containing polymers are as follows: [Table 2]

[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 in Patent Document 1, the copper etching solution of Comparative Example 4 corresponds to the copper etching solution of Example 7 in Patent Document 2, and the copper etching solution of Comparative Example 5 corresponds to the copper etching solution of Example 9 in Patent Document 3.

Claims

1. A copper etching solution, It contains an acid, an oxidizing metal ion source, a nitrogen atom-containing polymer, and water. The etching solution for copper is characterized in that 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.

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

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