Ruthenium plating solution or ruthenium alloy plating solution and plating method for ruthenium plating film or ruthenium alloy plating film

Abstract

A novel ruthenium plating solution is provided that can form a ruthenium plating film that is suppressed from cracking and has good abrasion resistance and corrosion resistance. [Solution] The present invention relates to a novel ruthenium plating solution containing a ruthenium complex salt and a conductive salt. In the ruthenium plating solution of the present invention, the ruthenium complex salt is a trivalent ruthenium complex salt whose anion component is a halogen. The ruthenium plating solution of the present invention contains an excess of halogen ions relative to the ruthenium complex salt. Specifically, the content of halogen ions, excluding the theoretical content of halogen ions derived from the ruthenium complex salt, is 4 to 200 times the molar content of the ruthenium complex salt.

Description

[Technical Field]

[0001] The present invention relates to a plating solution for forming a ruthenium plating film or a ruthenium alloy plating film by electroplating. More specifically, the present invention relates to a ruthenium plating solution containing a ruthenium complex salt that is easy to handle and can form a ruthenium plating film that is suppressed from generating cracks and has excellent corrosion resistance and abrasion resistance. The present invention also relates to a plating method for forming a ruthenium plating film using the plating solution. [Background technology]

[0002] Ruthenium (Ru) and ruthenium alloy plating films (hereinafter sometimes referred to simply as ruthenium plating films) are highly hard, have excellent wear resistance, good corrosion resistance, and low contact resistance, and are therefore used for the sliding contacts of electronic components such as reed switches, sliding switches, and connectors, as well as for decorative materials such as rings and necklaces. Ruthenium is a precious metal, along with platinum and palladium, but is relatively inexpensive. In particular, with the recent rise in prices of palladium and rhodium, there is growing interest in the use of ruthenium plating films as a replacement for plating films of these precious metals.

[0003] Several ruthenium plating solutions for forming ruthenium plating films are known that use various ruthenium complex salts as the metal source, but the most commonly used to date is a ruthenium plating solution that uses a ruthenium complex salt containing an Ru-N-Ru structure as the metal source (Patent Documents 1 and 2). The ruthenium complex salt in this ruthenium plating solution is synthesized by adding sulfamic acid or the like to a ruthenium compound (ruthenium chloride compound, ruthenium sulfate) as the raw material, and boiling and refluxing it to allow it to age. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-236489 [Patent Document 2] Japanese Patent Application Publication No. 4-165092 Summary of the Invention [Problem to be solved by the invention]

[0005] In the formation of ruthenium plating films, deposition efficiency (film formation rate) is an important characteristic. Ruthenium plating solutions using the above-mentioned ruthenium complex salts containing the Ru-N-Ru structure as the metal source are considered to be particularly useful because their deposition efficiency is better than that of other ruthenium plating solutions.

[0006] However, this conventional ruthenium plating solution is not without its problems. As mentioned above, the metal source of this ruthenium plating solution is a ruthenium complex salt containing a Ru-N-Ru structure, and its synthesis requires boiling reflux. Boiling reflux is an essential step for ensuring the deposition efficiency of the ruthenium plating solution, but the long time required for this process is not desirable from the viewpoint of production efficiency.

[0007] Furthermore, the complex structure of ruthenium complex salts, including those containing the Ru-N-Ru structure found in conventional ruthenium plating solutions, makes it difficult to maintain a stable state, which can hinder uniform ruthenium deposition. If stable ruthenium deposition is hindered, there is concern that cracks may develop in the ruthenium plating film. As mentioned above, ruthenium plating films are expected to serve as an alternative to plating films made with palladium, rhodium, and other metals, but to meet this demand, high-quality ruthenium plating films are required. While ensuring deposition efficiency is important, expanding the use of ruthenium plating films requires new plating solutions capable of forming crack-free plating films with excellent abrasion and corrosion resistance.

[0008] The present invention has been made in light of the above background, and provides a ruthenium plating solution that can suppress cracking and form a ruthenium plating film that has good wear resistance and corrosion resistance. The present invention also clarifies a plating method for producing a high-quality ruthenium plating film using the ruthenium plating solution. [Means for solving the problem]

[0009] To solve the above problems, the present inventors investigated the use of trivalent ruthenium complex salts containing halogens as anion components as the ruthenium complex salts, which are the metal source for ruthenium plating solutions. Because halogen compounds have a relatively simple structure, they can be synthesized efficiently, and the barriers to producing ruthenium plating solutions are low. Furthermore, because ruthenium halogen compounds have good stability due to their simple structure, they are thought to be able to suppress the occurrence of cracks in plating films. Furthermore, halogen compounds of metals other than ruthenium are well known, and it is thought that alloy plating films can be formed by mixing ruthenium halogen compounds with halogen compounds of these other metals. However, although ruthenium halogen compounds are expected to have some of the advantages described above, there are few concrete examples of their application in actual plating solutions.

[0010] Therefore, the present inventors have conducted extensive research into a plating solution that uses a ruthenium halide compound as a metal source, to find a composition (additive) that can improve the quality of ruthenium plating films while taking into consideration deposition efficiency, and as a result, have arrived at the present invention.

[0011] That is, the present invention relates to a ruthenium plating solution comprising a ruthenium complex salt and a conductive salt, wherein the ruthenium complex salt is a trivalent ruthenium complex salt whose anion component is a halogen, the ruthenium plating solution contains an excess of halogen ions relative to the ruthenium complex salt, and the content of the excess halogen ions is 4 to 200 times the molar content of the ruthenium complex salt. Hereinafter, the compositions of the ruthenium plating solution and ruthenium alloy plating solution according to the present invention will be described, along with methods for producing ruthenium plating films and ruthenium alloy plating films using the ruthenium plating solution and ruthenium alloy plating solution.

[0012] (A) Composition of the ruthenium plating solution and ruthenium alloy plating solution according to the present invention (A-1) Ruthenium plating solution The ruthenium plating solution according to the present invention contains, as essential components, a ruthenium complex salt as a metal source, halogen ions, and a conductive salt.

[0013] (i) Ruthenium complex salts As described above, the ruthenium complex salt used in the present invention for depositing ruthenium is a trivalent ruthenium complex salt whose anion component is a halogen. This trivalent ruthenium complex salt must be contained in the ruthenium plating solution at least during the plating treatment stage. Preferred examples of the trivalent ruthenium complex salt include hexachlororuthenic acid (III), hexabromorthenic acid (III), hexafluororuthenic acid (III), and salts thereof. In the case of salts, sodium salts are preferred. Particularly preferred is hexabromorthenic acid (III) salt (sodium hexabromorthenic acid (III)) whose anion component is bromine (Br).

[0014] The ruthenium concentration in the ruthenium plating solution is preferably 0.5 g / L or more and 20 g / L or less in terms of ruthenium metal. If the ruthenium concentration is below the lower limit, there is a problem that the formation of the ruthenium plating film does not proceed. On the other hand, if the ruthenium concentration exceeds the upper limit, it becomes difficult to suppress the occurrence of cracks when the plating film thickness is increased. Furthermore, an excessively high ruthenium concentration increases the cost of the plating solution. The ruthenium concentration is more preferably 2 g / L or more and 10 g / L or less.

[0015] (ii) Halogen ions The ruthenium plating solution according to the present invention must contain excess halogen ions relative to the ruthenium complex salt in the solution, and the content of the halogen ions relative to the content of the ruthenium complex salt must be within the range of 1:1. In the present invention, the term "excess halogen ions relative to the ruthenium complex salt" refers to the total amount of halogen ions in the ruthenium plating solution, excluding the theoretical amount of halogen ions derived from the ruthenium complex salt. By incorporating an excess halogen equivalent to or greater than the amount of the ruthenium complex salt, the ruthenium complex salt is stabilized and the appearance of the deposit becomes uniform. The content of the excess halogen ions is set to 4 to 200 times the molar amount of the ruthenium complex salt. Even with excess halogen ions, it is difficult to achieve a uniform appearance of the deposit if the content is less than 4 times the molar amount of the ruthenium complex salt. Furthermore, excess halogen ions exceeding 200 times the molar amount of the ruthenium complex salt provide no additional benefits, and there are concerns about increased specific gravity and viscosity of the plating solution, reduced deposition efficiency, and increased halogen gas generation at the anode. The content of excess halogen ions is more preferably 10 to 100 times the number of moles of the ruthenium complex salt.

[0016] A preferred method for incorporating excess halogen ions relative to the ruthenium complex salt into the ruthenium plating solution is to add a halogen compound. Examples of halogen compounds include hydrochloric acid (HCl), hydrobromic acid (HBr), chlorides such as sodium chloride (NaCl), bromides such as sodium bromide (NaBr), and halogen compounds such as sodium iodide (NaI). In this case, bromine compounds are particularly preferred because they are less likely to corrode the underlying metal.

[0017] Furthermore, when a halogen compound is added to a ruthenium plating solution to contain the above-mentioned excess halogen ions, the halogen ions may be different from the halogen of the anion component of the above-mentioned ruthenium complex salt, but are preferably the same. In the present invention, to confirm that the ruthenium plating solution contains excess halogen ions and to measure their content, it is sufficient to compare the total halogen ion content in the plating solution with the theoretical halogen content calculated from the content of the ruthenium complex salt in the plating solution. The content of excess halogen ions can also be measured by measuring the amount of free halogen not coordinated to the ruthenium complex salt in the plating solution.

[0018] (iii) Conductive salt The inclusion of a conductive salt in a ruthenium plating solution can achieve uniform deposit appearance and crack suppression. This effect can be particularly achieved in plating processes at high current densities. The conductive salt is at least one of boric acid, borates, phosphoric acid, phosphates, saturated monocarboxylic acids with two or more carbon atoms, saturated monocarboxylic acid salts with two or more carbon atoms, saturated dicarboxylic acids with three or more carbon atoms, saturated dicarboxylic acid salts with three or more carbon atoms, saturated hydroxycarboxylic acids, saturated hydroxycarboxylic acid salts, aminocarboxylic acids, aminocarboxylic acid salts, aminosulfonic acids, and aminosulfonic acid salts. When the conductive salt is a salt, sodium salts, potassium salts, and ammonium salts are preferred, with sodium salts being particularly preferred. The conductive salt may contain at least one of the above-mentioned compounds, and may be used alone or in combination.

[0019] The conductive salt content is preferably 0.001 mol / L or more and 1.0 mol / L or less. If the conductive salt content is less than 0.001 mol / L, it is equivalent to not adding any conductive salt, and there is no effect of making the deposit appearance of the ruthenium plating film uniform or suppressing the occurrence of cracks. Furthermore, adding too much conductive salt increases the specific gravity and viscosity of the plating solution, reducing the deposition efficiency. Therefore, adding more than 1.0 mol / L of conductive salt is not preferred. A more preferred conductive salt content is 0.03 mol / L or more and 0.5 mol / L or less.

[0020] (iv) Oxidizing sacrificial agent (reducing agent component) The ruthenium plating solution according to the present invention preferably contains an optional oxidizing sacrificial agent comprising a reducing agent component. The oxidizing sacrificial agent reduces ruthenium with a valence of 3 or higher and halogen gas by oxidizing near the anode, thereby imparting stability to the plating solution over time. The function of this oxidizing sacrificial agent will now be described in detail.

[0021] Ruthenium is a metal that is prone to valence changes. One of the causes of valence changes in ruthenium is that ruthenium consumes electrons during electrolysis near the anode, resulting in trivalent ruthenium (Ru 3+ ) to tetravalent ruthenium (Ru 4+ ) and a change in valence. In the present invention, the anion component of the ruthenium complex salt is a halogen ion, which is oxidized at the anode to produce halogen gas. This halogen gas may oxidize trivalent ruthenium to tetravalent ruthenium, causing a change in valence. These changes in the valence of ruthenium may also occur simultaneously.

[0022] In the present invention, it is trivalent ruthenium that is deposited on the surface of the substrate (cathode) as a ruthenium plating film. Therefore, the decrease in trivalent ruthenium due to the above-mentioned change in valence can affect the deposition efficiency. Furthermore, halogen gas generated by the oxidation of halogen ions can become dissolved in the plating solution. This dissolved halogen gas may be reduced at the cathode, reducing the deposition efficiency of ruthenium. This decrease in deposition efficiency due to the change in valence of trivalent ruthenium and halogen ions tends to occur over time during the plating process.

[0023] When an oxidizing sacrificial agent comprising a reducing agent component is added to the ruthenium plating solution of the present invention, the oxidizing sacrificial agent sacrificially oxidizes prior to trivalent ruthenium near the anode, thereby suppressing the above-mentioned change in valence. The action of such a sacrificial oxidizing agent suppresses a decrease in the deposition efficiency of ruthenium, allowing the plating process to continue.

[0024] In the present invention, the reducing agent component serving as the oxidizing sacrificial agent is preferably any one of formic acid or formate, oxalic acid or oxalate, sugar, and sugar alcohol. Suitable sugars include glucose, fructose, maltose, and trehalose, and suitable sugar alcohols include sorbitol, mannitol, xylitol, and lactitol. The content of the oxidizing sacrificial agent is preferably 0.01 mol / L or more and 0.5 mol / L or less. A content of less than 0.01 mol / L fails to sufficiently suppress the aforementioned valence changes of ruthenium and halogen ions. Addition in excess of 0.5 mol / L not only fails to provide any further improvement, but also increases the specific gravity and viscosity of the plating solution, resulting in a decrease in the deposition rate, which is undesirable. A more preferred content of the oxidizing sacrificial agent is 0.05 mol / L or more and 0.20 mol / L or less.

[0025] (v) Other configurations The ruthenium plating solution according to the present invention may contain, in addition to the above-described ruthenium complex salt, conductive salt, oxidizing sacrificial agent (reducing agent), and halogen compound, known additives used in electroplating solutions, such as a pH buffer, a stabilizer, and a brightener.

[0026] Furthermore, when measuring the concentrations of the components described above in ruthenium plating solutions, the plating solution can be analyzed and measured using inductively coupled plasma atomic emission spectroscopy (ICP) or ion chromatography (IC). Other analytical instruments, such as high-performance liquid chromatography (HPLC), high-performance liquid chromatography mass spectrometry (LC-MS, LC-MS / MS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR), can also be selected and used appropriately. Furthermore, in addition to the analytical methods mentioned above, halogen concentrations can also be measured using the DPD (diethyl-p-phenylenediamine) method (colorimetric or absorptiometric), iodine method, and amperometric method (polarographic method), which are known methods for measuring residual halogen concentrations in solutions. Measurements can also be made using testers, instruments, and measurement kits used for these methods.

[0027] The ruthenium plating solution according to the present invention can be produced by mixing the components of a trivalent ruthenium complex salt, a halogen compound for adjusting the halogen ion content, a conductive salt, and, optionally, an oxidation sacrificial agent. At this time, boiling and refluxing may be carried out at a temperature of 60°C to 100°C for 2 hours to 24 hours, but boiling and refluxing is not essential. Alternatively, the above components may be dissolved in high concentrations in advance to prepare a stock solution, which can then be diluted appropriately and used to prepare a ruthenium plating solution.

[0028] Furthermore, as described above, the ruthenium plating solution according to the present invention is sufficient as long as it contains a trivalent ruthenium complex salt at the plating treatment stage. Therefore, it is preferable to mix a trivalent ruthenium complex salt even at the production stage of the plating solution, but a ruthenium complex salt with a higher valence (four or more valences) may also be added. This is because even a plating solution containing a ruthenium complex salt with a higher valence can be converted to a trivalent ruthenium complex salt by reduction in the plating solution. In this case, methods for reducing the ruthenium complex salt with a higher valence include adding a reducing agent and electrolytic reduction using dummy electrolysis before the plating treatment.

[0029] (A-2) Ruthenium alloy plating solution The ruthenium plating solution according to the present invention described above can be a ruthenium alloy plating solution for forming a ruthenium alloy plating film containing ruthenium and the other metal by containing a halide of a metal other than ruthenium.

[0030] As the other metal that forms an alloy with ruthenium, a metal belonging to the so-called transition metals is applied. In consideration of useful applications of ruthenium alloys, platinum group metals such as palladium, platinum, iridium, ruthenium, rhodium, and osmium are suitable as the other metal. The ruthenium alloy plating solution according to the present invention contains each of the components of the ruthenium plating solution described above and a metal halide of a platinum group metal, thereby making it possible to form a ruthenium alloy plating film of ruthenium and another platinum group metal.

[0031] The ruthenium alloy plating solution of the present invention has the same composition as the ruthenium plating solution described above, and contains a trivalent ruthenium halide, a conductive salt, halogen ions, an optional oxidizing sacrificial agent (reducing agent component), and other components. The contents of these components can be the same as those of the ruthenium plating solution. In this case, the amount of excess halogen ions is preferably 4 to 200 times the total molar amount of the ruthenium complex salt and the complex salt of the other metal.

[0032] The ruthenium alloy plating solution of the present invention contains, in addition to the above components, other metal halide compounds, and the preferred halogens are the same as those described above. Furthermore, the halogen of the other metal halide compounds is preferably the same as the excess halogen in the ruthenium plating solution. However, the valence of the other metal in the halogen compound of the other metal is not particularly specified. The content of the other metal halide compounds can be appropriately adjusted depending on the composition of the ruthenium alloy to be deposited.

[0033] (B) Ruthenium film plating method using the ruthenium plating solution according to the present invention Next, a plating method using the ruthenium plating solution or ruthenium alloy plating solution according to the present invention will be described. While the plating method using the ruthenium plating solution will be described below, the contents and preferred conditions thereof also apply to a plating method using a ruthenium alloy plating solution.

[0034] In plating treatment using the ruthenium plating solution according to the present invention, it is preferable to maintain the plating solution in an acidic range. Specifically, the pH is preferably 0.1 or higher and 4.0 or lower. If the pH exceeds 4.0, precipitation of ruthenium compounds is likely to occur in the ruthenium plating solution, making it difficult to maintain the ruthenium concentration in the plating solution. The pH is more preferably 0.5 or higher and 2.0 or lower. The temperature of the plating solution is preferably 25°C or higher and 95°C or lower. Since the solution temperature is related to the deposition efficiency, deposition efficiency is poor at temperatures below 25°C. On the other hand, operation at temperatures higher than 95°C can cause problems such as volatilization loss of the plating solution and deterioration of the jigs. The solution temperature is more preferably 50°C or higher and 80°C or lower.

[0035] The current density in the plating process can be adjusted taking into consideration the concentration of ruthenium complex salts in the ruthenium plating solution and the type of conductive salt, thereby producing a ruthenium plating film with a desirable appearance. The current density range is 0.1 A / dm 2 More than 30A / dm 2 Less than 0.1A / dm is preferable. 2 Below 30A / dm it is inefficient to form a ruthenium plating film of the required thickness. 2 If the current density exceeds 2A / dm, it becomes difficult to prevent the occurrence of defects in the appearance of the plating film. 2 More than 12A / dm 2 It is more preferable that: [Effects of the Invention]

[0036] As explained above, the ruthenium plating solution and ruthenium alloy plating solution according to the present invention use a ruthenium complex salt whose anion component is a halogen. The ruthenium complex salt used in the present invention has a relatively simple complex structure, which allows for efficient production and preparation of the plating solution. Furthermore, the present invention allows for the production of a high-quality ruthenium plating film with reduced cracking by optimizing the concentration of halogen ions in the plating solution, selecting a conductive salt, and using an optional reducing agent, etc. DETAILED DESCRIPTION OF THE INVENTION

[0037] First embodiment Hereinafter, an embodiment of the present invention will be described. In this embodiment, a ruthenium plating solution was prepared by using sodium hexachlororuthenate (III) or sodium hexabromorthenate (III) as a ruthenium complex salt and adding a halogen compound to the ruthenium complex salt so that the ruthenium complex salt contains excess halogen ions. Then, a ruthenium plating film was formed using the prepared ruthenium plating solution.

[0038] Ruthenium plating solution was prepared by adding sodium hexachlororuthenate (III) or sodium hexabromorthenate (III) (Na3(RuBr6)) to pure water, and then adding a conductive salt. Sodium chloride or sodium bromide was added to this solution to change the halogen ion concentration relative to the ruthenium complex salt.

[0039] Then, a ruthenium plating film was formed using the prepared ruthenium plating solution. The plating conditions were as follows. In the following, the current density range was 2.0 A / dm when the ruthenium concentration in the plating solution was 2 g / L. 2 ~12.0A / dm 2 When the ruthenium concentration is 4 g / L or more, the 2 ~24.0A / dm 2 It was decided. Substrate (cathode): Cu panel (2cm x 2cm) with 5μm Ni plating and 0.2μm Au plating Anode: Pt-plated Ti mesh anode Plating solution temperature: 65℃ Plating solution pH: 1.0 ·Current density: 2.0A / dm 2 , 4.0A / dm 2 , 8.0A / dm 2 , 12.0A / dm 2 , 24.0A / dm 2 ·Amount of current: 3.2A min

[0040] After plating, the substrate was removed, the average film thickness was measured, and then the appearance was observed to evaluate the presence or absence of cracks. For appearance evaluation, the surface of the ruthenium plating film was observed under a microscope (magnification 50x), and those without cracks were judged as passing (◯), and those with cracks or abnormal appearance were judged as failing (×). Furthermore, the deposition rate was calculated based on the difference in mass of the substrate sample before and after plating. These evaluation results are shown in Table 1.

[0041] [Table 1]

[0042] From Table 1, in the ruthenium plating solution (Comparative Example 1) in which the molar amount of excess halogen ions was less than four times the molar amount of the ruthenium complex salt, the plating temperature was low (2.0 A / dm 2 and 4.0A / dm 2 In the ruthenium plating solution of Comparative Example 1, a ruthenium plating film could be formed, but the appearance was uneven. 2 At 12.0A / dm, black powder precipitates appear. 2 In other words, with the ruthenium plating solution of Comparative Example 1, a plating film with a good appearance could not be obtained even when the current density was adjusted.

[0043] In contrast, it was confirmed that in a ruthenium plating solution containing an excess of halogen ions of 4 times or more molar ratio relative to ruthenium, by appropriately setting the current density range, it is possible to form a suitable ruthenium plating film with no uneven appearance. In a ruthenium plating solution with a relatively low concentration of ruthenium complex salts, a current density of 4.0 A / dm 2 At the following current densities, a suitable ruthenium plating film with no uneven appearance could be formed (Examples 1 to 8). Furthermore, with reference to Examples 2 to 8, even when the ruthenium complex salt concentration was low, by increasing the excess halogen ion content, it was possible to form a ruthenium plating film with a current density of 8 A / dm 2 , 12.0A / dm 2 The appearance of the plating film was also good. By increasing the concentration of ruthenium complex salt and adjusting the halogen ion concentration accordingly, 2 and 24.0A / dm 2 Even in the above high current density range, good ruthenium plating films were formed (Examples 9 to 11). Furthermore, the ruthenium plating solutions of the Examples, which were operated under the same conditions as the Comparative Examples, showed improvements in deposition rate. These findings confirm the effectiveness of ruthenium plating solutions containing halogen ions in excess of 4 times the molar amount of ruthenium complex salt.

[0044] Second embodiment In this embodiment, the influence of changing the type and amount of conductive salt added when producing a ruthenium plating solution was examined.

[0045] The ruthenium plating solution of this embodiment was prepared by adding sodium hexabromorthenate (III) to pure water to give a ruthenium concentration of 2 g / L, and further adding a halogen compound and various conductive salts. In this embodiment, a number of ruthenium plating solutions were produced by varying the type and amount of conductive salt added.

[0046] Then, a ruthenium plating film was formed using the produced ruthenium plating solution. The plating conditions were the same as those in the first embodiment. After the plating process, the average film thickness was measured and the appearance was observed to evaluate the presence or absence of cracks, and the deposition rate was calculated, as in the first embodiment. These evaluation results are shown in Table 2.

[0047] [Table 2]

[0048] From Table 2, the ruthenium plating solution of Comparative Example 2, which does not contain conductive salt, has a current of 4.0 A / dm 2 Plating at the above current densities resulted in the formation of black powder-like deposits and powdery shedding, making it impossible to observe the ruthenium plating film. It was confirmed that the addition of a conductive salt is necessary to ensure the quality of the ruthenium plating film and improve the plating operation range in the ruthenium plating solution according to the present invention. The selection of the conductive salt should be determined based on the relationship between current density and deposition rate. Sodium acetate, used in Examples 14 and 15, is effective in increasing the deposition rate at relatively low current densities. Furthermore, in Examples 22 and 23, multiple conductive salts were added, and although the presence or absence of sulfamic acid caused differences in the appearance of the plating film at high current densities, it was found to be effective in increasing the deposition rate at low current densities.

[0049] Third embodiment In this embodiment, various oxidation sacrificial agents were added to the ruthenium plating solution, and the effects of the type and amount of each agent on the deposition rate and deposition appearance were confirmed.

[0050] Ruthenium plating solutions were prepared by adding sodium hexabromorthenate (III) to pure water to achieve a ruthenium concentration of 2 g / L, followed by the addition of a halide compound and a conductive salt. Various types and amounts of oxidizing sacrificial agents were added to the solution. The compositions of the ruthenium plating solutions prepared in this embodiment are shown in Table 3.

[0051] [Table 3]

[0052] Then, a ruthenium plating film was formed using the produced ruthenium plating solution. In this embodiment, (a) the plating solution immediately after production was subjected to plating under the same plating conditions as in the first embodiment, and (b) the plating solution was then subjected to electrolysis (192 A min / L: equivalent to passing a current of 1 A for 192 minutes through 1 L of plating solution) while being replenished with ruthenium complex salt equivalent to the precipitated ruthenium, and then plating was performed under the same plating conditions as in the first embodiment. Then, for the plating processes performed in (a) and (b), the average film thickness was measured and the appearance was observed to evaluate the presence or absence of cracks, and the deposition rate was calculated. These evaluation results are shown in Table 4.

[0053] [Table 4]

[0054] From Table 4, in the plating treatment using the ruthenium plating solution (a) immediately after production, the deposition rate and the quality of the ruthenium plating film were good regardless of whether or not an oxidation sacrificial agent was added. On the other hand, looking at the results for the ruthenium plating solution (b) in a running state, the ruthenium plating solution without the addition of an oxidation sacrificial agent was able to form a ruthenium plating film at a low current density, but at a current density of 8.0 A / dm 2 The plating film became uneven at 12.0A / dm 2From these results, it was confirmed that the addition of an oxidation sacrificial agent is effective in ensuring the quality of the ruthenium plating film, improving the plating operation range, and suppressing the deterioration of the plating bath over time.

[0055] Fourth embodiment In this embodiment, a ruthenium alloy plating solution was prepared by adding a halogen compound of another metal (platinum group metal) to a ruthenium plating bath, and plating of a ruthenium alloy plating film was carried out using the solution.

[0056] The ruthenium alloy plating solution was produced by adding various ruthenium halide compounds (III) and halogen compounds of other platinum group metals (platinum, iridium, palladium) to pure water, and further adding halogen compounds and conductive salts for adding halogen ions. Furthermore, an oxidation sacrificial agent was added to some of the plating solutions. The composition of the ruthenium alloy plating solution produced in this embodiment is shown in Table 5.

[0057] [Table 5]

[0058] Then, a ruthenium alloy plating film was formed using the produced ruthenium alloy plating solution. The plating conditions were the same as in the first embodiment. After the plating process, the average film thickness was measured and the appearance was observed to evaluate the presence or absence of cracks, and the deposition rate was calculated, as in the first embodiment. Furthermore, the alloy ratio of the formed ruthenium alloy plating film was measured using a fluorescent X-ray film thickness meter. These evaluation results are shown in Table 6.

[0059] [Table 6]

[0060] From Table 6, it was confirmed that it is possible to form plating films of ruthenium-platinum group metal alloys (Ru-Pt alloy, Ru-Ir alloy, Ru-Pd alloy, Ru-Pd-Pt alloy) having various alloy ratios using the various ruthenium alloy plating solutions produced in this embodiment. [Industrial Applicability]

[0061] The ruthenium plating solution of the present invention employs a highly stable and easily synthesized ruthenium complex salt whose anion component is a halogen, and the halogen ion content in the plating solution is in an excess amount equal to or greater than the ruthenium complex salt. According to the present invention, high-quality ruthenium plating films and ruthenium alloy plating films with reduced cracking can be produced. The ruthenium plating solution and ruthenium alloy plating solution of the present invention are useful for protective plating of connectors and terminals of electronic components and the like, and for electrodes and wiring of electronic and semiconductor devices. The present invention is also useful for forming plating films on jewelry and the like.

Claims

1. A ruthenium plating solution containing a ruthenium complex salt and a conductive salt, The ruthenium complex salt is a trivalent ruthenium complex salt whose anion component is a halogen, the ruthenium plating solution contains excess halogen ions relative to the ruthenium complex salt; A ruthenium plating solution characterized in that the content of the excess halogen ions is 4 to 200 times by mole the content of the ruthenium complex salt.

2. 2. The ruthenium plating solution according to claim 1, wherein the conductive salt comprises one or more compounds selected from the group consisting of boric acid, borates, phosphoric acid, phosphates, saturated monocarboxylic acids, saturated monocarboxylic acid salts, saturated dicarboxylic acids, saturated dicarboxylic acid salts, saturated hydroxycarboxylic acids, saturated hydroxycarboxylic acid salts, aminocarboxylic acids, aminocarboxylic acid salts, aminosulfonic acids, and aminosulfonic acid salts.

3. 3. The ruthenium plating solution according to claim 1, wherein the concentration of metallic ruthenium is 0.5 g / L or more and 20 g / L or less.

4. 3. The ruthenium plating solution according to claim 1, wherein the ruthenium complex salt is hexabromorthenic acid or a hexabromorthenic acid salt.

5. 3. The ruthenium plating solution according to claim 1, further comprising an oxidation sacrificial agent comprising a reducing agent component.

6. 6. The ruthenium plating solution according to claim 5, wherein the oxidizing sacrificial agent is any one of formic acid or a formate, oxalic acid or an oxalate, or a sugar or a sugar alcohol.

7. A ruthenium alloy plating solution obtained by adding a metal halide other than ruthenium to the ruthenium plating solution according to claim 1 or 2.

8. 8. The ruthenium alloy plating solution according to claim 7, wherein the metal halide other than ruthenium is a metal halide of a platinum group metal.

9. A ruthenium plating method using the ruthenium plating solution according to claim 1 or 2, comprising: The pH of the ruthenium plating solution is set to 0.1 or more and 4.0 or less, The bath temperature is set to 25°C or higher and 95°C or lower. Current density: 0.1 A / dm ２ 30A / dm or more ２ A ruthenium plating method in which the plating process is carried out as follows:

10. A method for plating a ruthenium alloy using the ruthenium alloy plating solution according to claim 7 or 8, comprising: The pH of the ruthenium alloy plating solution is set to 0.1 or more and 4.0 or less, The bath temperature is set to 25°C or higher and 95°C or lower. Current density: 0.1 A / dm ２ 30A / dm or more ２ A ruthenium alloy plating method comprising the steps of:

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