Method for producing plating solution

Abstract

To provide a technique capable of satisfactorily forming a ruthenium plating film even on a base metal or a material to be plated which is deteriorated under strong acidity.SOLUTION: A method for producing a plating solution according to one aspect of the present disclosure includes a preparation step of preparing a plating solution for ruthenium plating by adding raw materials to a solvent to be the plating solution. The preparation step also includes a step of adding a Ru (NH3) 6 3 + complex.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The disclosed embodiments relate to a method for producing a plating solution. [Background technology]

[0002] Ruthenium plating films have been expected to be put to practical use as an alternative to expensive noble metal plating films such as Au (gold) and Rh (rhodium) (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Kinase, "Platinum Group Ruthenium Plating," Surface Technology, Surface Finishing Association of Japan, October 2004, Vol. 55, pp. 635-639 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional technologies have issues such as the occurrence of cracks when thick films are formed, the plating solution being unstable and leaving internal residue, and the plating solution having a narrow usable pH range and being highly acidic, which limits their applications and has prevented them from becoming widespread.

[0005] For example, the plating solutions of the above-mentioned prior art are plating solutions produced using ruthenium sulfate or ruthenium chloride as raw materials, and are strongly acidic (for example, pH=1.2 to 1.7).

[0006] Therefore, in the above-mentioned conventional techniques, if the base metal or the material to be plated is a material that deteriorates under strong acidity, the base metal or the like deteriorates during the plating process, making it very difficult to form a high-quality ruthenium plating film.

[0007] The present disclosure has been made in view of the above, and provides a technique that can successfully form a ruthenium plating film even on a base metal or a plated material that is altered under strong acidity. [Means for solving the problem]

[0008] A method for producing a plating solution according to one embodiment of the present disclosure includes a preparation step of adding raw materials to a solvent to prepare a plating solution for ruthenium plating. 3+ The method includes the step of adding a complex. [Effects of the Invention]

[0009] According to the present disclosure, a ruthenium plating film can be successfully formed even on a base metal or a plated material that is altered under strong acidity. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flowchart showing an example of a procedure for manufacturing a plating solution according to an embodiment. [Figure 2] FIG. 2 is a flowchart illustrating an example of a procedure of the preparation process according to the embodiment. [Figure 3] FIG. 3 is a graph showing the relationship between the pH of the plating solution and the thickness of the ruthenium plating film. [Figure 4] FIG. 4 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a bright nickel plating film. [Figure 5] FIG. 5 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 0.5. [Figure 6] FIG. 6 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 1.5. [Figure 7] FIG. 7 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 2. [Figure 8]FIG. 8 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 3. [Figure 9] FIG. 9 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 4. [Figure 10] FIG. 10 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 5. [Figure 11] FIG. 11 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 9. [Figure 12] FIG. 12 is a diagram showing an SEM image (magnification: 100 times) of the surface of a bright nickel plating film. [Figure 13] FIG. 13 is a diagram showing an SEM image (magnification: 100 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 0.5. [Figure 14] FIG. 14 is a diagram showing an SEM image (magnification: 100 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 1.5. [Figure 15] FIG. 15 is a diagram showing an SEM image (magnification: 100 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 2. [Figure 16] FIG. 16 is a diagram showing an SEM image (magnification: 100 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 3. [Figure 17] FIG. 17 is a diagram showing an SEM image (magnification: 100 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 4. [Figure 18] FIG. 18 is a diagram showing an SEM image (magnification: 100 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 5. [Figure 19] FIG. 19 is a diagram showing an SEM image (magnification: 100 times) of the surface of a ruthenium plating film formed using a plating solution with a pH of 9. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the method for producing a plating solution disclosed herein will be described in detail with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments described below.

[0012] Details of the plating solution manufacturing process according to the embodiment will be described with reference to Figures 1 and 2. Figure 1 is a flowchart showing an example of the procedure of the plating solution manufacturing process according to the embodiment.

[0013] In the manufacturing process of the plating solution according to the embodiment, first, an operator or the like performs a preparation process in which various raw materials are added to a solvent (such as water) to prepare a plating solution for ruthenium plating (step S101).

[0014] 2 is a flowchart showing an example of the procedure of the preparation process according to the embodiment. In the preparation process according to the embodiment, first, an operator or the like adds Ru(NH3)6 to a solvent that will become a plating solution. 3+ A complex, namely, a hexaammineruthenium(III) complex, is added (step S201).

[0015] For example, in embodiments, Ru(NH3)6 3+ The complex Ru(NH3)6Cl3, i.e., hexaammineruthenium(III) chloride, can be added to the solvent.

[0016] In this way, Ru(NH3)6 3+ By adding the complex, it is possible to prevent the formation of precipitates containing ruthenium in the plating solution, even if the plating solution is not strongly acidic.

[0017] Therefore, according to the embodiment, a ruthenium plating film can be formed satisfactorily even on a base metal or a plated material such as a nickel thin film that is altered under strong acidity.

[0018] The process of step S201 is not limited to adding Ru(NH3)6Cl3 to the solvent, and other ruthenium ammine complexes (such as Ru(NH3)6Cl2) may be added to the solvent.

[0019] Following the process of step S201, in the preparation process according to the embodiment, an operator or the like adds sulfamic acid to the solvent that will become the plating solution (step S202).

[0020] Thus, in embodiments, Ru(NH3)6 3+ By adding sulfamic acid in addition to the complex, it is possible to further suppress the formation of precipitates containing ruthenium in the plating solution, even if the plating solution is not strongly acidic.

[0021] Therefore, according to the embodiment, even if the underlying metal or material to be plated is a nickel thin film that is altered under strong acidity, a ruthenium plating film can be formed more satisfactorily.

[0022] Finally, the worker adds sulfuric acid to the solvent that will become the plating solution (step S203), completing the series of preparation processes. 3+ The solution to which the complex or the like has been added is adjusted to be strongly acidic.

[0023] In this manner, in the embodiment, the solution to be boiled and refluxed is adjusted to be strongly acidic before the boiling and refluxing treatment described later, thereby further suppressing the formation of precipitates containing ruthenium in the plating solution even if the plating solution is not strongly acidic.

[0024] Therefore, according to the embodiment, even if the underlying metal or material to be plated is a nickel thin film that is altered under strong acidity, a ruthenium plating film can be formed more satisfactorily.

[0025] In the process of step S203, an example in which sulfuric acid is added to the solvent that becomes the plating solution is shown, but the present disclosure is not limited to such an example, and an acid other than sulfuric acid may be added as long as it is a strong acid that is not easily volatilized even during boiling and refluxing treatment.

[0026] Furthermore, the example in Figure 2 shows an example in which steps S201 to S203 are performed sequentially in this order as the preparation process, but the present disclosure is not limited to such an example, and steps S201 to S203 may be performed in any order, or multiple processes may be performed simultaneously.

[0027] Returning to the explanation of Fig. 1, following the process of step S101 described above, in the manufacturing process of the plating solution according to the embodiment, a boiling and refluxing process is performed in which an operator or the like boils and refluxes the solution prepared in the preparation process (step S102).

[0028] In this way, by refluxing the solution prepared in the preparation process while boiling it, it is possible to further suppress the formation of precipitates containing ruthenium in the plating solution even if the plating solution is not strongly acidic.

[0029] Therefore, according to the embodiment, even if the underlying metal or material to be plated is a nickel thin film that is altered under strong acidity, a ruthenium plating film can be formed more satisfactorily.

[0030] Following the process of step S102, the operator or the like performs an addition process of adding an ammonium salt to the solution that has been subjected to the boiling and refluxing process (step S103).

[0031] For example, in an embodiment, ammonium sulfamate, a type of ammonium salt, may be added in this addition process, which can prevent the pH of the plating solution from actually changing even when various external factors cause the pH of the plating solution to change.

[0032] In an embodiment, ammonium sulfate, a type of ammonium salt, may be added in the addition process, which increases the conductivity of the plating solution and improves the efficiency of the electroplating process for forming the palladium plating film.

[0033] The ammonium salt added to the solution in the addition process according to the embodiment is not limited to ammonium sulfamate or ammonium sulfate. For example, ammonium formate or ammonium chloride may be added to the solution in the addition process according to the embodiment.

[0034] Following the process in step S103, the operator or the like performs a pH adjustment process to adjust the pH of the solution to a desired pH after the addition process (step S104), thereby completing the series of processes for producing the plating solution.

[0035] For example, in an embodiment, ammonia water is added to the strongly acidic solution that has been subjected to the additive treatment, thereby adjusting the pH of the solution to a pH (for example, a pH between 1 and 9) that is suitable for the base metal and the material to be plated. This allows a good ruthenium plating film to be formed even on base metals or materials to be plated that are made of various materials.

[0036] Furthermore, in the pH adjustment step according to the embodiment, the pH of the solution may be adjusted to a value between 3 and 9. This allows a ruthenium plating film to be formed more satisfactorily even on an underlying metal or a plated material such as a nickel thin film that is altered under strong acidity.

[0037] In the example of FIG. 1, steps S103 and S104 are sequentially performed in this order as a plating solution manufacturing process, but the present disclosure is not limited to this example, and steps S103 and S104 may be performed in any order, or these steps may be performed simultaneously. [Example]

[0038] The present disclosure will be described in more detail below with reference to various examples, but the present disclosure is not limited to the following examples.

[0039] [Preparation of the sample to be plated] First, a sample to be plated on which a ruthenium plating film was to be formed was prepared. Specifically, a 0.3 mm thick oxygen-free copper plate was first washed with a 0.1 M sulfuric acid solution. Then, the copper plate was rinsed with water.

[0040] Next, a bright nickel plating film was formed on the surface of the water-washed copper sheet by electroplating. The plating solution (hereinafter also referred to as plating bath) for this electroplating process was prepared by adding 120 g of nickel sulfate hexahydrate, 22.5 g of nickel chloride hexahydrate, 17.5 g of boric acid, 0.1 g of 2-butyne-1,4-diol, 1.0 g of sodium saccharinate, and 0.0025 g of SDS (sodium lauryl sulfate, also known as sodium dodecyl sulfate) to a 500 mL water-based bath.

[0041] The conditions for the electrolytic plating treatment were: bath temperature: 50°C, current density: 2A / dm 2 A bright nickel plating film was formed to a thickness of 1.3 μm. The time required for forming the bright nickel plating film was 5 minutes.

[0042] Finally, the sample on which the bright nickel plating film was formed was washed with water to obtain a plating sample on which a ruthenium plating film was to be formed.

[0043] [Example 1] A ruthenium plating film was formed on the surface of the above-mentioned plating sample by electroplating. The plating bath for this electroplating was prepared by adding 1.5 g of Ru(NH3)6Cl3, 10 g of sulfamic acid, and 5.0 mL of concentrated sulfuric acid to a water-based solvent to prepare a 100 mL solution.

[0044] Next, 100 mL of this solution was subjected to boiling and refluxing treatment at 100°C for 3 hours, and 4.0 g of ammonium sulfamate and 12 g of ammonium sulfate were added to the boiling and refluxing solution.

[0045] Next, aqueous ammonia was added so that the pH of the solution to which the ammonium salt had been added was 3. Finally, the solution was evaporated at 60°C or water was added to make up 100 mL, to prepare a plating bath for ruthenium plating treatment.

[0046] The conditions for the electrolytic plating treatment were: bath temperature: 60°C, current density: 2A / dm 2 The ruthenium plating film was formed on the surface of the sample for 90 minutes.

[0047] Finally, the sample on which the ruthenium plating film was formed was washed with water and dried, and the sample of Example 1 was obtained.

[0048] [Examples 2 to 7] Samples of Examples 2 to 7, each having a ruthenium plating film formed on its surface, were obtained using the same method as in Example 1. In Examples 2 to 7, the production conditions of the plating solution for forming the ruthenium plating film were appropriately adjusted so that the pH of the plating solution was 0.5, 1.5, 2, 4, 5, and 9, respectively.

[0049] [Evaluation of plating solution] Next, the state of the plating solutions in Examples 1 to 7 was visually confirmed. The plating solutions in Examples 1 to 4, i.e., the plating solutions adjusted to pH = 0.5 to 3, were pale yellow. The plating solution in Example 5, i.e., the plating solution adjusted to pH = 4, was orange.

[0050] The plating solutions in Examples 6 and 7, i.e., the plating solutions adjusted to pH = 5 and 9, were deep purple. Furthermore, in all of the plating solutions in Examples 1 to 7, no precipitation occurred either before or after the plating treatment.

[0051] As a comparative example, when a plating solution for ruthenium plating film described in the prior art was adjusted to pH 8 with ammonia water or sodium hydroxide, precipitation of ruthenium compounds occurred in the plating solution. From this result, it is estimated that it is very difficult to adjust the pH of a plating solution to a value other than strongly acidic in the prior art.

[0052] [Evaluation of plating thickness] Next, the thickness of the plating films in Examples 1 to 7 was evaluated. Specifically, a commercially available X-ray fluorescence analyzer (S8 TIGER manufactured by Bruker AXS (now Bruker Japan)) was used to calculate the thickness of the underlying nickel film and the thickness of the ruthenium plating film from the amount of fluorescent X-rays. Measurements were performed in a vacuum chamber, with a measurement diameter of φ18 mm, and the average film thickness was obtained.

[0053] Fig. 3 is a diagram showing the relationship between the pH of the plating solution and the thickness of the ruthenium plating film. As shown in Fig. 3, when the pH of the plating solution was 3, the thickness of the ruthenium plating film was approximately 1.2 µm.

[0054] 3, even when the pH of the plating solution was 4 to 9, a ruthenium plating film was formed with a significant thickness, although the thickness was thinner than when the pH was 3. Thus, the plating solution of the embodiment functioned as a plating solution for forming a ruthenium plating film that can be used in a range from weakly acidic to alkaline conditions.

[0055] [Evaluation of surface condition] Next, the surface state of the bright nickel plating film formed on the plated sample and the surface state of the ruthenium plating film of Examples 1 to 7 were evaluated. First, the surface state of the samples of Examples 1 to 7 was visually confirmed. As a result, the ruthenium plating films of Examples 1 to 7 were all silver-gray in color and all had a mirror gloss.

[0056] Next, secondary electron images were taken of the surfaces of the plated samples and the samples of Examples 1 to 7 using a commercially available field emission scanning electron microscope (FE-SEM) (JEOL JSM-7001F) at an acceleration voltage of 15 kV, and the surface morphology of each was evaluated.

[0057] Fig. 4 is a diagram showing an SEM image (magnification: 50,000 times) of the surface of a bright nickel plating film. Figs. 5 to 11 are diagrams showing SEM images (magnification: 50,000 times) of the surface of ruthenium plating films formed using plating solutions with pH values ​​of 0.5, 1.5, 2, 3, 4, 5, and 9, respectively. As Figs. 4 to 11 show the surface condition of each sample at a microscopic level, due to the 50,000 times magnification.

[0058] As shown in Figures 6 and 7, cracks were observed in some areas of the ruthenium plating films formed using strongly acidic plating solutions with pH values ​​of 1.5 and 2. On the other hand, the ruthenium plating films formed using plating solutions with pH values ​​of 1.5 and 2 were generally in good condition.

[0059] Furthermore, as shown in Figure 5 and Figures 8 to 11, the ruthenium plating films formed using plating solutions with pH values ​​of 0.5 and 3 to 9 were good ruthenium plating films with no cracks observed. Note that, since the ruthenium plating film formed using a plating solution with a pH of 0.5 was thin as shown in Figure 3, it is presumed that no cracks occurred even in a strongly acidic plating solution.

[0060] Fig. 12 is a diagram showing an SEM image (magnification 100x) of the surface of a bright nickel plating film. Figs. 13 to 19 are diagrams showing SEM images (magnification 100x) of the surface of ruthenium plating films formed using plating solutions with pH values ​​of 0.5, 1.5, 2, 3, 4, 5, and 9, respectively. As Figs. 12 to 19 are shown at 100x magnification, they show the surface condition of each sample at a level visible to the naked eye.

[0061] As shown in FIGS. 13 to 19, the ruthenium plating films formed using plating solutions with pH values ​​of 0.5 to 9 were excellent ruthenium plating films, with no visible cracks visible to the naked eye.

[0062] As shown in Figures 14 and 15, pit marks were observed in some areas of the ruthenium plating films formed using strongly acidic plating solutions with pH values ​​of 1.5 and 2. However, it is believed that these pit marks can be reduced by using a cathode rocker or similar device during the plating process.

[0063] The method for producing a plating solution according to the embodiment includes a preparation step (step S101) of adding raw materials to a solvent to prepare a plating solution for ruthenium plating. 3+ The method includes a step of adding a complex (Step S201), which allows a good ruthenium plating film to be formed even on a base metal or a material to be plated, such as a nickel thin film, which is altered under strong acidity.

[0064] In the method for producing a plating solution according to the embodiment, Ru(NH3)6 3+ In the step of adding the complex (step S201), Ru(NH3)6Cl3 is added to the solvent, which allows a good ruthenium plating film to be formed even on the base metal or plated material, such as a nickel thin film, which deteriorates in strong acidic conditions.

[0065] In the method for producing a plating solution according to the embodiment, the preparation step (step S101) further includes a step of adding sulfamic acid to the solvent (step S202), which allows for the formation of a better ruthenium plating film even on an underlying metal or a plated material such as a nickel thin film that is altered under strong acidic conditions.

[0066] In the method for producing a plating solution according to the embodiment, the preparation step (step S101) further includes a step of adding sulfuric acid to the solvent (step S203), which allows for the formation of a better ruthenium plating film even on an underlying metal or a plated material such as a nickel thin film that is altered under strong acidic conditions.

[0067] The method for producing a plating solution according to the embodiment further includes a boiling and refluxing step (step S102) in which the solution prepared in the preparation step (step S101) is boiled and refluxed, thereby enabling a better formation of a ruthenium plating film even on an underlying metal or a plated material such as a nickel thin film that is altered under strong acidic conditions.

[0068] The method for producing a plating solution according to the embodiment further includes an addition step (step S103) of adding an ammonium salt to the solution boiled and refluxed in the boiling and refluxing step (step S102). This prevents the pH of the plating solution from actually fluctuating even when various external factors cause the pH of the plating solution to fluctuate. Furthermore, the efficiency of the electroplating process can be improved.

[0069] In the plating solution manufacturing method according to the embodiment, the ammonium salt includes at least one of ammonium sulfamate, ammonium sulfate, ammonium formate, and ammonium chloride. This prevents the pH of the plating solution from actually changing even when various external factors cause the pH of the plating solution to change. This also improves the efficiency of the electroplating process.

[0070] Moreover, the method for producing a plating solution according to the embodiment further includes a pH adjustment step (step S104) of adjusting the pH of the solution boiled and refluxed in the boiling and refluxing step (step S102) to a value between 1 and 9. This allows a good ruthenium plating film to be formed on various types of base metals or substrates.

[0071] Furthermore, in the method for producing a plating solution according to the embodiment, the pH adjustment step (step S104) adjusts the pH of the solution to a value between 3 and 9. This allows a ruthenium plating film to be formed more satisfactorily even on a base metal or a material to be plated, such as a nickel thin film, which is altered under strong acidity.

[0072] In the method for producing a plating solution according to the embodiment, the pH adjustment step (step S104) involves adding aqueous ammonia to the solution, thereby allowing the pH of the plating solution to be easily adjusted.

[0073] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0074] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

Claims

1. A preparation step of adding raw materials to a solvent to prepare a plating solution for ruthenium plating, The preparation step comprises: ３ ) ６ ３＋ adding a complex A method for producing a plating solution.

2. The Ru(NH ３ ) ６ ３＋ The step of adding the complex comprises adding Ru(NH ３ ) ６ Cl ３ Add The method for producing the plating solution according to claim 1 .

3. The preparing step further comprises adding sulfamic acid to the solvent. The method for producing the plating solution according to claim 2 .

4. The preparation step further includes adding sulfuric acid to the solvent. The method for producing the plating solution according to claim 3 .

5. The method further includes a boiling reflux step of boiling and refluxing the solution prepared in the preparation step. The method for producing the plating solution according to any one of claims 1 to 4.

6. The method further includes adding an ammonium salt to the solution boiled and refluxed in the boiling and refluxing step. The method for producing the plating solution according to claim 5 .

7. The ammonium salt includes at least one of ammonium sulfamate, ammonium sulfate, ammonium formate, and ammonium chloride. The method for producing the plating solution according to claim 6 .

8. The method further includes a pH adjusting step of adjusting the pH of the solution boiled and refluxed in the boiling and refluxing step to a value between 1 and 9. The method for producing the plating solution according to claim 5 .

9. The pH adjustment step adjusts the pH of the solution to between 3 and 9. The method for producing a plating solution according to claim 8 .

10. The pH adjustment step involves adding aqueous ammonia to the solution. The method for producing a plating solution according to claim 8 .

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