Etching liquid, replenishing liquid, and copper wire forming method

Abstract

To provide: an etching liquid with which it is easy to maintain the original function of the etching liquid such as side etching suppression; a replenishing liquid; and a copper wire forming method which makes it easy to maintain the function of the etching liquid.SOLUTION: Disclosed herein is a copper etching liquid including an acid, an oxidizing metal ion, a bromide ion, a compound having a piperazine skeleton and an imidazole compound, where the compound having the piperazine skeleton is represented by the general formula (1) in the figure. In the formula, R1 and R2 each independently represent a hydrogen atom, an amino group-containing substituent, or a C1-10 hydrocarbon-deriving group that is not an amino group-containing substituent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an etching solution, a replenisher thereof, and a method for forming copper wiring using the same. [Background technology]

[0002] In the manufacture of printed wiring boards, when forming copper wiring patterns using photoetching, etching solutions such as iron chloride-based etching solutions, copper chloride-based etching solutions, and alkaline etching solutions are used. The use of these etching solutions can result in a phenomenon known as side etching, where the copper beneath the etching resist dissolves from the sides of the wiring pattern. That is, the copper wiring portion, which is covered by the etching resist and should not be removed by etching, is removed by the etching solution, resulting in a phenomenon in which the width of the copper wiring narrows from the bottom to the top, or becomes much narrower than the desired width, making it impossible to obtain a desirable wiring shape. Particularly when the copper wiring pattern is fine, such side etching must be minimized.

[0003] Patent Documents 1 and 2 describe etching solutions that contain an azole compound, which is a heteroaromatic five-membered ring compound, and that suppress side etching. Patent Documents 3 and 4 describe etching solutions containing specific aliphatic heterocyclic compounds such as piperazine, and state that the action of this piperazine can suppress side etching without reducing the linearity of copper wiring.

[0004] However, with the etching solutions of Patent Documents 3 and 4, the specific aliphatic heterocyclic compound is decomposed and reduced with continued use, which may result in the etching solution being unable to fully exhibit its original functions, such as suppressing side etching and maintaining linearity, making it difficult to manage the etching solution. In order to address this problem, Patent Document 3 describes an attempt to suppress the decomposition of an aliphatic heterocyclic compound by adding a heteroaromatic compound having a five-membered heteroaromatic ring to an etching solution.

[0005] However, the literature does not describe at all a combination of an aliphatic heterocyclic compound and a heteroaromatic compound that can effectively inhibit the decomposition of the aliphatic heterocyclic compound, and there is a continuing demand for an etching solution that can continuously provide a sufficient side etching inhibition effect even when used continuously. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-330572 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-79284 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-224303 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-48409 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above-mentioned problems of the conventional art, and has as its object to provide an etching solution that can continuously provide a sufficient side-etching suppression effect even when used continuously, a replenisher thereof, and a method for forming copper wiring that can continuously provide a sufficient side-etching suppression effect. [Means for solving the problem]

[0008] The copper etching solution of the present invention contains an acid, an oxidizing metal ion, a bromide ion, a compound having a piperazine skeleton, and an imidazole compound; The compound having a piperazine skeleton is an etching solution represented by the following general formula (1).

[0009] [ka] In the formula, R1 and R2 each independently represent a hydrogen atom, an amino group-containing substituent, or a hydrocarbon-derived group having 1 to 10 carbon atoms excluding an amino group-containing substituent.

[0010] The imidazole compound may be one or more selected from the group consisting of imidazole, 2-ethyl-4-methylimidazole, 1-imidazoleacetic acid, 2-ethylimidazole, 2-aminobenzimidazole, 1-(3-aminopropyl)imidazole, and 2-aminoimidazole sulfate.

[0011] The imidazole compound may be an imidazole compound having no amino group.

[0012] The imidazole compound may be contained in an amount of 0.10 g / L or more and 20 g / L or less.

[0013] The compound having a piperazine skeleton may be contained in an amount of 0.01 g / L or more and 100 g / L or less.

[0014] The acid may be hydrochloric acid.

[0015] The oxidizing metal ion may be a cupric ion.

[0016] The concentration of the bromide ions may be 10 g / L or more and 150 g / L or less.

[0017] The present invention also relates to a replenishment liquid, which is added to each of the etching liquids when the etching liquids are used continuously or repeatedly, and which contains the compound having the piperazine skeleton and the imidazole compound.

[0018] The present invention also relates to a method for forming copper wiring, which is a method for forming copper wiring in which the portion of the copper layer that is not covered with the etching resist is etched using the etching solution described above. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide an etching solution that can continuously provide a sufficient side etching suppression effect even when used continuously, a replenisher thereof, and a method for forming copper wiring that can continuously provide a sufficient side etching suppression effect. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 shows a cross-sectional photograph of a copper wiring etched with the etching solution of this embodiment. [Figure 2] FIG. 2 shows a cross-sectional photograph of a copper wiring etched with the etching solution of this embodiment. [Figure 3] FIG. 3 shows a cross-sectional photograph of a copper wiring etched with the etching solution of the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the etching solution, the replenisher thereof, and the method for forming copper wiring according to the present invention will be described.

[0022] First, the etching solution of this embodiment will be described. The etching solution of this embodiment is an etching solution that is mainly used for forming copper wiring. That is, it is an etching solution used to form a predetermined shape of copper wiring or the like by covering the surface of a copper layer with an insulating layer such as an etching resist and bringing the etching solution into contact with the part not covered by the insulating layer. The method in which the etching solution of this embodiment is used will be described in detail in the copper wiring formation method described later. In this embodiment, "copper" may be made of copper or a copper alloy. Also, in this embodiment, "copper" refers to copper or a copper alloy.

[0023] The etching solution of this embodiment is a copper etching solution, and contains an acid, oxidizing metal ions, bromide ions, a compound having a specific piperazine skeleton, and an imidazole compound.

[0024] <Compounds with a piperazine skeleton> The etching solution of this embodiment contains the following compound having a piperazine skeleton (hereinafter also simply referred to as a piperazine compound) in order to suppress side etching without reducing the linearity of the copper wiring. The piperazine compound of this embodiment is a compound represented by the following general formula:

[0025] [ka] In the formula, R1 and R2 each independently represent a hydrogen atom, an amino group-containing substituent, or a hydrocarbon-derived group having 1 to 10 carbon atoms excluding an amino group-containing substituent.

[0026] R1 and R2 may be the same or different. The amino group refers to any one of -NH2, -NHR, and -NRR', where R and R' each independently represent a hydrocarbon-derived group having 1 to 6 carbon atoms. The amino group-containing substituent refers to any one of a substituent consisting of an amino group and a substituent in which some hydrogen atoms in a hydrocarbon-derived group having 1 to 6 carbon atoms have been replaced with amino groups. Examples include an aminoethyl group, an aminomethyl group, a diethylamino group, a dimethylamino group, a dimethylaminoethyl group, and a dimethylaminomethyl group. The hydrocarbon derivative group refers to a hydrocarbon group in which some carbon atoms or hydrogen atoms may be replaced by other atoms or substituents, and examples of the hydrocarbon derivative group include a methyl group, an ethyl group, a propyl group, a butyl group, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, an allyl group, an acetyl group, a hydroxyethoxymethyl group, a hydroxyethoxyethyl group, and a hydroxyethoxypropyl group.

[0027] Examples of the piperazine compound of the present embodiment include piperazine, 1-methylpiperazine, 1-allylpiperazine, 1-isobutylpiperazine, 1-hydroxyethoxyethylpiperazine, 1-(2-aminoethyl)piperazine, 1-amino-4-methylpiperazine, 1-ethylpiperazine, 1-piperazineethanol, 1-piperazine ethyl carboxylate, 1-formylpiperazine, 1-propylpiperazine, 1-acetylpiperazine, 1-isopropylpiperazine, Examples include 1-(2-methoxyethyl)piperazine, 1,4-dimethylpiperazine, 1-methyl-4'-(dimethylaminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, 1-(2-dimethylaminoethyl)-4-methylpiperazine, N-(2-aminoethyl)piperazine, 1-(2-hydroxyethyl)piperazine, N,N'-dimethylpiperazine, 1,4-bis(3-aminopropyl)piperazine, and 1,4-diformylpiperazine. The piperazine compounds can be used alone or in combination.

[0028] The etching solution of the present embodiment contains the piperazine compound, which allows for faster vertical etching during copper etching and facilitates the formation of a more uniform protective film, thereby providing an etching solution that is more likely to suppress excessive etching (side etching) of the side surfaces of copper wiring and the like. Furthermore, by allowing the piperazine compound to coexist in the etching solution together with an imidazole compound described below, the piperazine compound is less likely to be decomposed, and the side etching suppression function can be maintained even when the etching solution is used continuously for a long period of time.

[0029] In the etching solution of the present embodiment, the content of the piperazine compound is, for example, 0.01 g / L or more and 100 g / L or less, or 0.02 g / L or more and 80 g / L or less, or 0.05 g / L or more and 30 g / L or less. Such a content makes it possible to form an etching solution that rapidly progresses copper etching in the vertical direction and that also easily forms a uniform protective film.

[0030] <Imidazole compounds> The imidazole compound of this embodiment, when present in the etching solution together with the piperazine compound, has the function of suppressing decomposition of the piperazine compound. The imidazole compound refers to a compound having an imidazole skeleton, and examples thereof include imidazole, 2-ethyl-4-methylimidazole, 1-imidazoleacetic acid, 2-ethylimidazole, 2-aminobenzimidazole, 1-(3-aminopropyl)imidazole, 2-aminoimidazole sulfate, 2-methylimidazole, 2-undecyl-4-methylimidazole, 2-phenylimidazole, benzimidazole, 2-methylbenzimidazole, 2-undecylbenzimidazole, 2-phenylbenzimidazole, etc. When 2-aminoimidazole is converted into a sulfate, the effect of inhibiting the decomposition of the piperazine compound tends to be slightly reduced. The imidazole compounds can be used alone or in combination.

[0031] Since the etching solution of this embodiment contains the imidazole compound, it acts on the compound having the piperazine skeleton and can effectively suppress its decomposition. In particular, as will be described later, even when the etching solution is used in a state in which the compound having the piperazine skeleton is easily decomposed, such as when an oxidizing agent such as hydrogen peroxide is added to regenerate oxidizing metal ions during etching, the decomposition of the piperazine compound can be effectively suppressed. Therefore, the side etching suppression function can be sufficiently maintained. Furthermore, the imidazole compound effectively suppresses the decomposition of the piperazine compound, and at the same time does not impair other performances of the etching solution, such as adjustment of the etching rate, uniform formation of a protective film, etc. Therefore, the side etching suppression effect of the etching solution can be maintained without impairing the original etching performance.

[0032] The imidazole compound may be an imidazole compound having no amino group. When the imidazole compound has no amino group, it can particularly effectively suppress decomposition of the piperazine compound and sufficiently maintain the side etching suppression function. Examples of imidazole compounds not having an amino group include imidazole, 2-ethyl-4-methylimidazole, 1-imidazoleacetic acid, 2-ethylimidazole, 2-methylimidazole, 2-undecyl-4-methylimidazole, 2-phenylimidazole, benzimidazole, 2-methylbenzimidazole, 2-undecylbenzimidazole, and 2-phenylbenzimidazole.

[0033] In the etching solution of the present embodiment, the content of the imidazole compound is, for example, 0.10 g / L or more and 20 g / L or less, or 0.25 g / L or more and 20 g / L or less, or 0.5 g / L or more and 10 g / L or less, or 0.5 g / L or more and 5 g / L or less, or 0.6 g / L or more and 4 g / L or less. Such a content makes it easier to suppress decomposition of the piperazine compound, and in particular, even when an oxidizing agent or the like is added, an etching solution can be formed that can sufficiently suppress decomposition of the piperazine compound.

[0034] <Acid> The acid used in the etching solution of this embodiment can be appropriately selected from inorganic acids and organic acids. Examples of the inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and hydrobromic acid. Examples of the organic acids include formic acid, acetic acid, oxalic acid, maleic acid, benzoic acid, and glycolic acid. Among these acids, hydrochloric acid is preferred from the viewpoints of etching rate stability and copper dissolution stability. The concentration of the acid can be, for example, from 5 g / L to 350 g / L, or from 5 g / L to 330 g / L, or from 10 g / L to 350 g / L, or from 20 g / L to 330 g / L, or from 5 g / L to 180 g / L, or from 7 g / L to 150 g / L, etc. When the acid concentration is within the above range, the etching rate can be easily adjusted appropriately, copper can be etched at an appropriate rate, the dissolution stability of copper can be maintained, and deterioration of the working environment can be suppressed. The above acids can be used alone or in combination.

[0035] <Oxidizing metal ions> The oxidizing metal ion used in the etching solution of the present invention may be any metal ion capable of oxidizing metallic copper, such as cupric ion, ferric ion, etc. From the viewpoints of suppressing side etching and stabilizing the etching rate, it is preferable to use cupric ion as the oxidizing metal ion.

[0036] The oxidizing metal ions can be contained in the etching solution by blending an oxidizing metal ion source. For example, when a cupric ion source is used as the oxidizing metal ion source, examples of the oxidizing metal ion source include copper chloride, copper sulfate, copper bromide, copper salts of organic acids, and copper hydroxide. For example, when a ferric ion source is used as the oxidizing metal ion source, specific examples of the oxidizing metal ion source include iron chloride, iron bromide, iron iodide, iron sulfate, iron nitrate, and iron salts of organic acids. The oxidizing metal ions may be used alone or in combination as needed.

[0037] The concentration of the oxidizing metal ions is, for example, 10 g / L to 300 g / L, or 10 g / L to 250 g / L, or 15 g / L to 220 g / L, or 30 g / L to 200 g / L. When the concentration of the oxidizing metal ions is within the above range, the etching rate can be easily adjusted appropriately, copper can be etched at an appropriate rate, and the dissolution stability of copper is maintained.

[0038] <Bromide ion> The bromide ions used in the etching solution of this embodiment can be contained in the etching solution by blending a bromide ion source. Examples include hydrobromic acid, sodium bromide, potassium bromide, lithium bromide, magnesium bromide, calcium bromide, barium bromide, copper bromide, zinc bromide, ammonium bromide, silver bromide, and bromine. Hydrobromic acid, sodium bromide, and potassium bromide are preferred from the viewpoints of further suppressing the deterioration of the linearity of the copper wiring and side etching, and further suppressing the variation in the wiring width (W1) of the bottom of the copper wiring after etching. The bromide ion sources may be used alone or in combination as needed.

[0039] The concentration of the bromide ions is, for example, 10 g / L to 150 g / L, or 20 g / L to 120 g / L, or 30 g / L to 110 g / L. When the concentration of bromide ions is within the above range, side etching can be effectively suppressed, and at the same time, variations in the wiring width (W1) of the bottom of the copper wiring after etching can be effectively suppressed.

[0040] In addition to the components described above, other components may be added to the etching solution of this embodiment to the extent that the effects of the present invention are not impaired. For example, surfactants, component stabilizers, antifoaming agents, etc. may be added. When such other components are added, the concentration thereof is approximately 0.001 g / L or more and 5 g / L or less.

[0041] The etching solution can be easily prepared by dissolving the above components in water. The water is preferably water from which ionic substances and impurities have been removed, such as ion-exchanged water, pure water, or ultrapure water. The etching solution may be prepared by blending 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 etching solution is not particularly limited, but to effectively suppress side etching, it is preferable to perform etching using a spray, as described below. The temperature of the etching solution during use is not particularly limited, but to effectively suppress side etching while maintaining high productivity, it is preferable to use the etching solution at a temperature of 20°C or higher and 60°C or lower.

[0042] Next, the replenishment liquid of this embodiment will be described. The replenishment liquid of the present embodiment is a replenishment liquid to be added to the etching liquid of the present embodiment when the etching liquid is used continuously or repeatedly, and contains the compound having the piperazine skeleton and the imidazole compound. The components in the replenisher liquid are the same as those that can be blended into the etching solution of the present embodiment described above. By adding the replenisher liquid, the ratio of the components in the etching solution is maintained appropriately, so that the effects of the etching solution of the present embodiment described above can be stably maintained.

[0043] The replenisher liquid of the present invention may contain the acid contained in the above-mentioned etching solution in a concentration not exceeding 360 g / L. The replenisher liquid may contain each of the oxidizing metal ions contained in the above-mentioned etching solution in a concentration not exceeding 14 g / L. The replenisher liquid may contain the bromide ion source contained in the above-mentioned etching solution in a bromide ion concentration not exceeding 800 g / L. The replenisher liquid may contain components to be added to the etching solution in addition to the above-mentioned components. These components that may be contained in the replenisher liquid may be added directly to the etching solution when the etching solution is used continuously or repeatedly, without being contained in the replenisher liquid.

[0044] The concentrations of the components in the replenisher solution are appropriately set depending on the concentrations of the components in the etching solution, but from the viewpoint of stably maintaining the effects of the etching solution of the present embodiment described above, the concentration of the compound having a piperazine skeleton is preferably 0.01 g / L or more and 800 g / L or less, and similarly, the concentration of the imidazole compound is preferably 0.1 g / L or more and 400 g / L or less.

[0045] Next, a method for forming copper wiring according to this embodiment will be described. The method for forming copper wiring of this embodiment (hereinafter also simply referred to as the method) is a method for forming copper wiring in which the portions of the copper layer that are not covered with the etching resist are etched using the etching solution of this embodiment described above.

[0046] The copper wiring in this embodiment mainly refers to copper wiring formed by photoetching in the manufacture of printed wiring boards. Examples of methods for forming such copper wiring include forming an etching resist on a copper layer such as copper foil on an insulating substrate, electroless copper plating film, electrolytic copper plating film, or copper sputtering film, and then etching the copper in the areas not covered by the etching resist to form a wiring pattern. Examples of printed wiring boards having copper wiring include rigid boards, flexible boards, metal core boards, and ceramic boards.

[0047] The etching resist is not particularly limited, and examples thereof include those made of insulating resin such as dry film or liquid resist, and those made of one or more layers of metal such as nickel or nickel / gold.

[0048] The copper wiring forming method of this embodiment is suitable for forming copper wiring having a fine wiring pattern. When the pattern is fine, side etching must be minimized as much as possible. However, the method for forming copper wiring using the etching solution of the present embodiment has the advantage that the occurrence of side etching can be effectively suppressed even when continuous etching is performed.

[0049] In the method of this embodiment, it is preferable to perform etching by spraying the etching solution onto the copper layer. This is because side etching can be effectively suppressed. The spray nozzle is not particularly limited, and any nozzle such as a fan nozzle, a full-cone nozzle, or a two-fluid nozzle can be used. Furthermore, when etching by spray, the spray pressure can be, for example, 0.04 MPa or more, 0.08 MPa or more, or 0.1 MPa or more. When the spray pressure is above this pressure, a protective film can be formed on the side of the copper wiring with an appropriate thickness. This can effectively prevent side etching. Note that the spray pressure can be 0.30 MPa or less to prevent damage to the etching resist.

[0050] The etching solution of this embodiment used in the method for forming copper wiring of this embodiment can maintain the effect of suppressing side etching. The mechanism by which side etching is suppressed is thought to be as follows: When copper wiring is formed using an etching solution containing an oxidizing metal ion source such as copper chloride, as in the etching solution of this embodiment, cuprous ions and their salts are generated as etching progresses. Because the exchange of solution between wirings is slow, the influence of cuprous ions and their salts gradually slows down vertical etching, particularly in fine wiring, resulting in increased side etching. The etching solution of this embodiment contains a compound having a piperazine skeleton and bromide ions, and therefore the compound having a piperazine skeleton can capture cuprous ions and their salts that are generated as etching progresses. As a result, vertical etching progresses quickly, and at the same time, a protective film composed of cuprous ions and their salts, the compound having a piperazine skeleton, and bromide ions is formed on the side surfaces of the copper wiring that are less likely to be directly impacted by the spray, and it is believed that this protective film can suppress side etching.

[0051] On the other hand, compounds having a piperazine skeleton may be decomposed by continuous use of the etching solution. For example, in the copper wiring forming method of this embodiment, an oxidizing agent such as hydrogen peroxide or chlorate may be added to the etching solution. The addition of such an oxidizing agent enables the regeneration of the etching solution. That is, as described above, the number of cuprous ions increases, resulting in a decrease in etching performance. However, the addition of an oxidizing agent regenerates the cuprous ions into cupric ions, thereby preventing the decrease in etching performance. In this case, the added oxidizing agent also decomposes the compound having the piperazine skeleton, which may result in a decrease in the side-etching suppression function.

[0052] However, since the etching solution of the present embodiment contains an imidazole compound in addition to the compound having a piperazine skeleton, the concentration of the compound having a piperazine skeleton can be maintained within a predetermined range even when etching is performed continuously or when an oxidizing agent is added to regenerate the solution. Therefore, even if etching is performed successively, the function of suppressing side etching can be stably maintained.

[0053] In the copper wiring forming method of this embodiment, when etching is performed continuously, the above-described replenishment solution of this embodiment may be replenished at appropriate times to maintain a predetermined etching performance. In this case, the timing for replenishing the replenishment liquid can be set appropriately, for example, by monitoring the concentration of any component in the etching liquid and replenishing the replenishment liquid when the concentration exceeds a predetermined range, or by replenishing the replenishment liquid in response to a change in the shape of the formed wiring.

[0054] In the method for forming copper wiring of this embodiment, steps such as cleaning the copper to be etched before and after etching, pretreatment before providing an etching resist on the copper surface, and stripping of the etching resist can be appropriately performed.

[0055] The etching solution, replenishment solution, and copper wiring forming method according to the present embodiment are as described above, but the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims. [Example]

[0056] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to these examples.

[0057] [Test 1: Component Remaining Test] (etchant) The etching solutions used in this example were prepared. Each etching solution was prepared using the following materials: 440 g / L cupric chloride dihydrate (copper ion concentration: 161 g / L), 130 g / L 47% hydrobromic acid (bromide ion concentration: 60 g / L), 263 g / L 35% hydrochloric acid (acid concentration: 92 g / L), 2 g / L of a compound with a piperazine skeleton, 1 g / L of an imidazole or tetrazole compound (or no imidazole or tetrazole compound added), and the remaining ion-exchanged water. The concentrations of some of the imidazole compounds were changed, and the concentrations are listed in the table.

[0058] material Cupric chloride dihydrate: Nippon Chemical Industry Co., Ltd. 47% hydrobromic acid: Tosoh Corporation 35% hydrochloric acid: Toagosei Compounds with a piperazine skeleton 1-Methyl-4'-(dimethylaminoethyl)piperazine: manufactured by Tokyo Chemical Industry Co., Ltd. N-(2-aminoethyl)piperazine: manufactured by Tokyo Chemical Industry Co., Ltd. 1-(2-hydroxyethyl)piperazine: manufactured by Tokyo Chemical Industry Co., Ltd. N,N'-Dimethylpiperazine: manufactured by Tokyo Chemical Industry Co., Ltd. Imidazole compounds 2-Ethyl-4-methylimidazole: manufactured by Tokyo Chemical Industry Co., Ltd. Imidazole: manufactured by Tokyo Chemical Industry Co., Ltd. 1-Imidazoleacetic acid: Tokyo Chemical Industry Co., Ltd. 2-Ethylimidazole: Tokyo Chemical Industry Co., Ltd. 2-Aminobenzimidazole: Tokyo Chemical Industry Co., Ltd. 1-(3-aminopropyl)imidazole: manufactured by Tokyo Chemical Industry Co., Ltd. 2-Aminoimidazole sulfate: Tokyo Chemical Industry Co., Ltd. Tetrazole compounds 1H-Tetrazole: Tokyo Chemical Industry Co., Ltd. 5-aminotetrazole: manufactured by Tokyo Chemical Industry Co., Ltd. 35% hydrogen peroxide: ADEKA

[0059] The concentration of each compound having a piperazine skeleton in each of the prepared solutions was measured using an HPLC (high performance liquid chromatography) apparatus (Waters, e2695). Then, 2 ml of 35% hydrogen peroxide was added to 1 L of each etching solution, mixed, and left at room temperature for 24 hours. The concentration of each compound having a piperazine skeleton was measured again using an HPLC system under the same conditions. The concentration of the compound having a piperazine skeleton after adding hydrogen peroxide relative to the concentration before adding hydrogen peroxide is shown in Table 1 as the residual rate (%).

[0060] [Table 1]

[0061] [Test 2: Pattern shape observation] (substrate) A copper-clad laminate was prepared by laminating a 12 μm-thick electrolytic copper foil (Mitsui Mining & Smelting Co., Ltd., product name: 3EC-III). The copper foil was treated with a palladium catalyst-containing treatment solution (Okuno Pharmaceutical Co., Ltd., product name: Adcopper Series), and then an electroless copper plating film was formed using an electroless copper plating solution (Okuno Pharmaceutical Co., Ltd., product name: Adcopper Series). Next, a 10 μm-thick electrolytic copper plating film was formed on the electroless copper plating film using an electrolytic copper plating solution (Okuno Pharmaceutical Co., Ltd., product name: Top Lucina SF), resulting in a total copper layer thickness of 22.5 μm. The surface of the resulting electrolytic copper plating film was coated with a 25 μm-thick dry film resist. The resist was then exposed using a glass mask with a line / space (L / S) of 36 μm / 24 μm, and the unexposed areas were removed by development to create an etching resist pattern with a line / space (L / S) of 36 μm / 24 μm.

[0062] The etching solution prepared in Test 1 above, which contained 1-methyl-4'-(dimethylaminoethyl)piperazine as the piperazine skeleton compound and the compounds listed in Table 2 as the imidazole or tetrazole compounds, was used to etch the substrate. After adding and mixing 35% hydrogen peroxide, the solution was left at room temperature for 24 hours. The etching was performed using a fan-shaped nozzle (manufactured by Ikeuchi Co., Ltd., product name: ISVV9020) at a spray pressure of 0.20 MPa and a solution temperature of 45°C for 138 seconds. The 138-second treatment time was set to the target time at which the wiring width at the bottom of the copper wiring after etching reaches 30 μm when the etching solution contains imidazole as the imidazole compound and has a 100.0% residual rate of the piperazine skeleton compound. Thereafter, the substrate was washed with water, the dry film resist was removed (immersed in acetone for 30 seconds), and dried to produce a copper patterned substrate.

[0063] Each substrate was then cut, embedded in polyester cold embedding resin, and polished. The cross section was observed using a metallurgical microscope (KEYENCE VHX-7000) with an objective lens of 1000x. Five points were measured at the top and bottom of the copper wiring, and the averages were taken as the top width (T) and bottom width (B). The results are shown in Table 2.

[0064] [Table 2]

[0065] [Test 3: Changes in pattern shape due to changes in imidazole compound concentration] Of the etching solutions prepared in Test 1 above, two types of etching solutions were prepared: one containing a compound having a piperazine skeleton and an imidazole compound, 1-methyl-4'-(dimethylaminoethyl) and imidazole, and the other containing N-(2-aminoethyl)piperazine and 2-ethyl-4-methylimidazole. The concentrations of the imidazole compounds were adjusted to the concentrations listed in Table 3. For each solution, patterns were formed in the same manner as in Test 2 above (except that 35% hydrogen peroxide was not added), with the treatment time being the number of seconds listed in Table 3. The bottom width (B) of the pattern was measured in the same manner as in Test 2. The results are shown in Table 3.

[0066] [Table 3]

[0067] [Test 4: Test for residual components due to changes in piperazine compound concentration] The etching solutions were the same as those used in Test 1, but with varying concentrations of the compound having a piperazine skeleton. The concentrations of the compound having a piperazine skeleton and the imidazole compound after adding hydrogen peroxide were measured in the same manner as in Test 1. N-(2-aminoethyl)piperazine was used as the compound having a piperazine skeleton, and imidazole was used as the imidazole compound. The results are shown in Table 4.

[0068] [Table 4]

[0069] [Consideration] In Test 1, it was clear that each etching solution containing an imidazole compound had a higher residual rate of the compound having a piperazine skeleton than the etching solution containing a tetrazole compound and the etching solution containing no imidazole compound or no tetrazole compound. In Test 2, when the residual rate of the compound having a piperazine skeleton was low, the pattern shape after etching became narrower in both the top width (T) and bottom width (B). That is, it was clear that the effect of the compound having a piperazine skeleton in suppressing excessive etching of the side surface of the wiring was easily maintained by adding an imidazole compound. In Test 3, when the imidazole compound concentration was 1 g / L or 4 g / L, the bottom width of the pattern narrowed as the treatment time increased for both etching solutions. This means that it was easy to set an appropriate treatment time to obtain the desired pattern width. When the imidazole compound concentration was 30 g / L, there was no correlation between the treatment time and the bottom width, and therefore it became somewhat difficult to set an appropriate treatment time to obtain the desired pattern width. In Test 4, regardless of the concentration of the compound having a piperazine skeleton between 0.1 and 20 g / L, the residual rate of the compound having a piperazine skeleton was very high even after adding hydrogen peroxide when the imidazole compound was contained at 1 g / L. In other words, it was revealed that when the compound having a piperazine skeleton is contained within the above concentration range, the effect of suppressing excessive etching of the side surface of the wiring can be maintained at an imidazole compound concentration of 1 g / L.

Claims

1. A copper etchant comprising: the etching solution contains an acid, an oxidizing metal ion, a bromide ion, a compound having a piperazine skeleton, and an imidazole compound; The compound having a piperazine skeleton is an etching solution represented by the following general formula (1): 【Chemical 1】 In the formula, R1 and R2 each independently represent a hydrogen atom, an amino group-containing substituent, or a hydrocarbon-derived group having 1 to 10 carbon atoms excluding an amino group-containing substituent.

2. 2. The etching solution according to claim 1, wherein the imidazole compound is one or more selected from the group consisting of imidazole, 2-ethyl-4-methylimidazole, 1-imidazoleacetic acid, 2-ethylimidazole, 2-aminobenzimidazole, 1-(3-aminopropyl)imidazole, and 2-aminoimidazole sulfate.

3. The etching solution according to claim 1 , wherein the imidazole compound is an imidazole compound having no amino group.

4. The etching solution according to claim 2 , wherein the imidazole compound is an imidazole compound having no amino group.

5. 5. The etching solution according to claim 1, wherein the imidazole compound is contained in an amount of 0.10 g / L or more and 20 g / L or less.

6. 5. The etching solution according to claim 1, wherein the compound having a piperazine skeleton is contained in an amount of 0.01 g / L or more and 100 g / L or less.

7. The etching solution according to any one of claims 1 to 4, wherein the acid is hydrochloric acid.

8. 5. The etching solution according to claim 1, wherein the oxidizing metal ion is a cupric ion.

9. 5. The etching solution according to claim 1, wherein the concentration of the bromide ions is 10 g / L or more and 150 g / L or less.

10. A replenisher liquid to be added to the etching solution when the etching solution according to any one of claims 1 to 4 is used continuously or repeatedly, comprising: A replenishment solution comprising the compound having the piperazine skeleton and the imidazole compound.

11. A method for forming copper wiring, which comprises etching a portion of a copper layer that is not covered with an etching resist, using the etching solution according to any one of claims 1 to 4.

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