Electroless ruthenium plating bath

Abstract

The objective is to provide an electroless ruthenium plating bath using hydrazines as a reducing agent that can improve bath stability, exhibit excellent ruthenium deposition properties, and suppress film shrinkage during annealing. [Solution] An electroless ruthenium plating bath containing at least a ruthenium compound, a reducing agent, and a stabilizer, wherein the reducing agent is a hydrazine, the stabilizer consists of a hydroxylamine compound and an organic compound having a hydroxyl group, the hydroxylamine compound is at least one of hydroxylamine sulfate and hydroxylamine chloride, and the organic compound having a hydroxyl group is at least one selected from the group consisting of gluconolactone, sorbitol, mannitol, and citric acid monohydrate.

Description

Technical Field

[0001] The present invention relates to an electroless ruthenium plating bath.

Background Art

[0002] Conventionally, copper has a high electrical conductivity, excellent physical properties such as connection properties by thermal compression bonding, and also excellent chemical properties such as oxidation resistance and chemical resistance. Therefore, in the field of the electronics industry, it is widely used in wiring in the circuits of printed boards, mounting parts and terminal parts of IC packages, etc.

[0003] Here, with the miniaturization of semiconductor circuits, copper wiring has also been miniaturized. However, when such miniaturization is carried out, the current density flowing through the copper wiring increases. Therefore, there is a problem that voids are generated due to electromigration (a phenomenon in which copper atoms move when a high-density current flows through the copper wiring), and disconnection occurs.

[0004] Therefore, in recent years, ruthenium has attracted attention as a next-generation wiring material to replace copper. This ruthenium is a material with a high allowable current density and high electromigration resistance compared to copper. Therefore, in addition to the wiring of the above semiconductor circuits, it is expected as a material for forming a thin film (cap metal) formed on the copper wiring and forming a liner layer for uniformly growing a copper seed film on a barrier metal when forming a copper wiring by electrolytic plating.

[0005] And in the process of forming the wiring of this semiconductor circuit, etc., if an electroless ruthenium plating process can be used, it becomes possible to selectively deposit ruthenium only by immersion treatment without the need for an external power source. Therefore, an electroless plating bath containing ruthenium has been proposed.

[0006] For example, an electroless ruthenium plating bath has been proposed that contains a ruthenium source, a polyaminopolycarboxylic acid as a complexing agent, sodium borohydride (NaBH4) as a reducing agent, and hydroxylamine sulfate as a stabilizer (see, for example, Patent Document 1).

[0007] Furthermore, an electroless ruthenium plating bath containing a ruthenium source and an amine borane compound such as dimethylamine borane (DMAB) as a reducing agent has been proposed (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2012-508819 [Patent Document 2] Japanese Unexamined Patent Publication No. 61-39235 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] In the plating bath described in Patent Document 1, ruthenium has multiple valencies, making it difficult to precipitate as a metal, resulting in poor precipitation. Furthermore, although sodium borohydride is used as a reducing agent, its high reactivity makes it prone to bath decomposition and precipitation in patterns other than the desired one, making it difficult to handle.

[0010] Furthermore, in the plating bath described in Patent Document 2 above, an amine borane compound, which is a common reducing agent, is used. However, amine borane compounds have somewhat poor reducing ability, and only films with a high content of impurity oxygen due to co-deposition of unreduced oxides (ruthenium oxide) can be obtained. As a result, there was a problem that the film would shrink due to oxygen degassing during the annealing process.

[0011] Therefore, in view of the above-mentioned problems, the present invention aims to provide an electroless ruthenium plating bath using hydrazines as a reducing agent that can improve bath stability, has excellent ruthenium deposition properties, and can suppress film shrinkage during annealing. [Means for solving the problem]

[0012] To achieve the above objective, the electroless ruthenium plating bath of the present invention is an electroless ruthenium plating bath containing at least a ruthenium compound, a reducing agent, and a stabilizer, wherein the reducing agent is a hydrazine, the stabilizer consists of a hydroxylamine compound and an organic compound having a hydroxyl group, the hydroxylamine compound is at least one of hydroxylamine sulfate and hydroxylamine chloride, and the organic compound having a hydroxyl group is at least one selected from the group consisting of gluconolactone, sorbitol, mannitol, and citric acid monohydrate. [Effects of the Invention]

[0013] According to the present invention, since hydrazines with high reducing ability are used as reducing agents, a ruthenium plating film with a low content of impurity oxygen can be obtained, and shrinkage of the film during annealing treatment can be suppressed.

[0014] Furthermore, since hydroxylamine compounds and organic compounds having hydroxyl groups are used as stabilizers, the bath stability can be improved, and the precipitation of ruthenium can be enhanced. [Modes for carrying out the invention]

[0015] The electroless ruthenium plating bath of the present invention will be described below.

[0016] <Electroless ruthenium plating bath> The electroless ruthenium plating bath of the present invention is a plating bath containing at least a ruthenium compound, a reducing agent, and a stabilizer.

[0017] (Ruthenium compound) The ruthenium compound is a source of ruthenium ions for obtaining ruthenium plating. This ruthenium compound may be water-soluble, and examples include inorganic water-soluble ruthenium salts such as ruthenium chloride, ruthenium sulfate, and ruthenium nitrate. These ruthenium compounds may be used alone or in combination of two or more.

[0018] In addition, ruthenium has multiple valences, and the deposition amount of ruthenium in the plating bath varies depending on the valence of ruthenium. From the perspective of ensuring the stability of the plating bath, the valence of ruthenium is preferably trivalent or tetravalent.

[0019] Therefore, as the ruthenium compound, for example, ruthenium(III) chloride, ruthenium(III) nitrate composed of trivalent ruthenium, ruthenium(IV) chloride, ruthenium(IV) sulfate, etc. composed of tetravalent ruthenium are preferably used.

[0020] The concentration of the ruthenium compound (i.e., as ruthenium ions) in the electroless ruthenium plating bath is not particularly limited. However, if the ruthenium ion concentration is too low, the deposition rate of the plating film may be significantly reduced. Therefore, it is preferably 0.01 g / L or more, more preferably 0.1 g / L or more. Also, if the ruthenium ion concentration is too high, bath decomposition may occur due to an excessive reaction. Therefore, it is more preferably 10 g / L or less.

[0021] The ruthenium ion concentration can be measured by atomic absorption spectrometry (AAS) using an atomic absorption spectrophotometer.

[0022] (Reducing agent) The reducing agent is for reducing a ruthenium compound, which is a source of ruthenium ions, in an electroless ruthenium plating bath to deposit ruthenium. In the electroless ruthenium plating bath of the present invention, hydrazines are used as the reducing agent.

[0023] Examples of such hydrazines include hydrazine monohydrate, hydrazine dihydrochloride, and hydrazinium sulfate. From the viewpoint of high solubility and no need for neutralization or the like, it is preferable to use hydrazine monohydrate. These hydrazines may be used alone or in combination of two or more.

[0024] Also, the concentration of hydrazines in the plating bath is preferably 0.03 mol / L or more and 1.32 mol / L or less. More specifically, when using hydrazine monohydrate (80%), it is preferably 2 ml / L or more and 80 ml / L or less; when using hydrazine dihydrochloride, it is preferably 3 g / L or more and 138 g / L or less; when using hydrazinium sulfate, it is preferably 4 g / L or more and 171 g / L or less. This is because when it is less than 0.03 mol / L, deposition of ruthenium may be difficult. Generally, the plating rate increases in proportion to the concentration of the reducing agent. However, when it is greater than 1.32 mol / L, the plating rate does not improve much in proportion to the concentration, and thus the bath stability of the plating bath may decrease.

[0025] And in the electroless ruthenium plating bath of the present invention, since hydrazines with high reducing ability are used as the reducing agent, the residual amount of un-reduced oxide (ruthenium oxide) decreases, and a ruthenium plating film with a low content of impurity oxygen can be obtained. Therefore, due to the annealing treatment, the volume shrinkage rate caused by oxygen released from the ruthenium plating film becomes small, and it becomes possible to suppress the shrinkage of the ruthenium plating film during the annealing treatment.

[0026] Furthermore, in this invention, because the ruthenium plating film contains a small amount of impurity oxygen, the impurity oxygen can be easily removed from the ruthenium plating film by performing an annealing treatment, and a film equivalent to a pure ruthenium plating film can be obtained. As a result, the resistivity of the film after annealing treatment becomes 30 [μΩcm] or less, and low resistance of the ruthenium plating film can be achieved.

[0027] (Stabilizer) The stabilizer primarily acts as a complexing agent to stabilize the solubility of ruthenium in the electroless ruthenium plating bath. In the electroless ruthenium plating bath of the present invention, a hydroxylamine compound and an organic compound having a hydroxyl group are used in combination as this stabilizer.

[0028] Hydroxylamine compounds contribute to the stability of electroless ruthenium plating baths by forming metal complexes with ruthenium ions. Examples of these hydroxylamine compounds include hydroxylamine sulfate and hydroxylamine chloride. These hydroxylamine compounds may be used individually or in combination.

[0029] In electroless ruthenium plating baths, the content of hydroxylamine compounds is preferably 1 g / L or more, and more preferably 2 g / L or more, because if the concentration of hydroxylamine compounds is too low, the bath stability may decrease and bath decomposition may occur. On the other hand, if the concentration of hydroxylamine compounds is too high, the bath stability may become excessive and the precipitation of ruthenium may decrease, so it is preferably 10 g / L or less, and more preferably 8 g / L or less.

[0030] Furthermore, organic compounds having a hydroxyl group, when used in combination with the hydroxylamine compounds mentioned above in an electroless ruthenium plating bath, function as a second complexing agent and contribute to bath stability by forming a metal complex with ruthenium ions.

[0031] Examples of organic compounds having a hydroxyl group include gluconolactone, sorbitol, mannitol, and citric acid monohydrate. These organic compounds having a hydroxyl group may be used individually or in combination of two or more.

[0032] In electroless ruthenium plating baths, the content of organic compounds having hydroxyl groups is preferably 1 g / L or higher, because if the concentration of organic compounds having hydroxyl groups is too low, the bath stability may decrease. Conversely, if the concentration of organic compounds having hydroxyl groups is too high, the bath stability may become excessive and the precipitation of ruthenium may decrease. Therefore, a concentration of 20 g / L or less is preferred, and 10 g / L or less is more preferred.

[0033] Here, because hydroxylamine compounds contribute more to bath stability than organic compounds containing hydroxyl groups, using only hydroxylamine compounds as stabilizers can lead to excessive bath stability, narrowing the range in which ruthenium can precipitate relative to the amount added, and thus potentially reducing the precipitation properties of ruthenium.

[0034] Therefore, in the electroless ruthenium plating bath of the present invention, by using a hydroxylamine compound and an organic compound having a hydroxyl group that contributes less to bath stability compared to the hydroxylamine compound as stabilizers, it becomes possible to obtain an electroless ruthenium plating bath with improved bath stability (i.e., preventing excessive bath stability) and excellent deposition properties, in an electroless ruthenium plating bath using hydrazines as reducing agents to suppress the shrinkage of the ruthenium film mentioned above.

[0035] Furthermore, it becomes possible to obtain an electroless ruthenium plating bath with excellent deposition properties, especially in fine areas where plating reactions are difficult to occur (for example, areas to be plated with a plating area of ​​several tens of nanometers).

[0036] (Precipitation rate modifier) Precipitation rate modifiers are added to facilitate the removal of underlying oxides and other materials, and have the effect of improving the precipitation rate of ruthenium.

[0037] Various chelating agents can be used as precipitation rate modifiers, including nitrogen-containing phosphorus compounds such as EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), DTPA (diethylenetriaminepentaacetic acid), DTPA-OH (1,3-diamino-2-hydroxypropanetetraacetic acid), HEDTA (hydroxyethylethylenediaminetriacetic acid), TTHA (triethylenetetraminehexaacetic acid), CyDTA (trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid), and EDTMP (ethylenediaminetetramethylenephosphonic acid), as well as citric acid, malic acid, gluconic acid, lactic acid, malonic acid, fumaric acid, maleic acid, tartaric acid, acetic acid, succinic acid, oxalic acid, glycolic acid, and formic acid. Other examples include amino acid compounds such as glycine, alanine, aspartic acid, glutamic acid, iminodiacetic acid, leucine, isoleucine, lysine, tryptophan, valine, histidine, arginine, serine, and tyrosine. These precipitation rate modifiers may be used individually or in combination of two or more.

[0038] In electroless ruthenium plating baths, the content of the deposition rate regulator is preferably 1 g / L or more, and more preferably 2 g / L or more, because if the concentration of the deposition rate regulator is too low, the deposition rate of ruthenium will decrease, and the plating process may take longer. On the other hand, if the concentration of the deposition rate regulator is too high, it will increase costs due to excessive addition, so it is preferably 60 g / L or less, and more preferably 20 g / L or less.

[0039] (Other ingredients) In the electroless ruthenium plating bath of the present invention, in order to further promote the deposition of ruthenium, an amine borane compound may be included as a second reducing agent in addition to the hydrazines mentioned above.

[0040] Examples of amine borane compounds include dimethylamine borane (DMAB), trimethylamine borane (TMAB), morpholine borane, picoline borane, pyridine borane, diethylaniline borane, and ammonia borane. Dimethylamine borane, trimethylamine borane, and morpholine borane are preferred from the viewpoint of being widely available and easy to obtain. Furthermore, ammonia borane is preferred from the viewpoint of having relatively high reaction activity. These amine borane compounds may be used individually or as a mixture of two or more.

[0041] Furthermore, in the electroless ruthenium plating bath of the present invention, when an amine borane compound is used as a reducing agent in addition to the hydrazines mentioned above, the concentration of the amine borane compound in the plating bath is preferably 0.1 g / L or more and 5 g / L or less. This is because if the concentration is less than 0.1 g / L, the effect of promoting ruthenium deposition may not be sufficiently obtained, and if it is greater than 5 g / L, bath decomposition due to excessive reaction may occur.

[0042] (pH) The pH of the electroless ruthenium plating bath of the present invention is preferably 11 to 14, and more preferably 12 to 14. This is because if the pH is less than 11, the deposition of ruthenium may be insufficient.

[0043] The pH of the plating bath can be adjusted using pH adjusters such as sodium hydroxide, potassium hydroxide, aqueous ammonia, tetramethylammonium hydroxide, sulfuric acid, hydrochloric acid, citric acid, boric acid, phosphoric acid, monocarboxylic acid, and dicarboxylic acid. These pH adjusters may be used individually or in combination of two or more.

[0044] (Temperature of the plating bath) The temperature of the plating bath is not particularly limited, but is preferably 45 to 85°C, and more preferably 50 to 75°C. This is because if the temperature of the plating solution is below 45°C, the plating solution may become inactive, resulting in insufficient ruthenium deposition, and if the temperature exceeds 85°C, the bath may become excessively activated, leading to bath decomposition.

[0045] (Plated object) There are no particular limitations on the type of object to be plated using the electroless ruthenium plating bath of the present invention, and conventional ruthenium plating objects (for example, wiring in printed circuit boards, mounting parts and terminal parts of IC packages, etc.) can be used as objects to be plated.

[0046] Furthermore, the electroless ruthenium plating bath of the present invention is particularly suitable for use in applications such as wiring portions of semiconductor circuits, thin films (cap metals) formed on copper wiring, or when forming a liner layer with ruthenium on a barrier metal to uniformly grow a copper seed film when forming a copper wiring film by electroplating.

[0047] (Electroless ruthenium plating treatment) By bringing the above-mentioned object to be plated into contact with the electroless ruthenium plating bath of the present invention and performing electroless ruthenium plating on the object to be plated, it is possible to form a ruthenium plated film that constitutes, for example, the wiring portion, thin film (cap metal), or liner layer. The temperature during the electroless ruthenium plating process is controlled to the temperature of the electroless ruthenium plating bath described above.

[0048] Furthermore, the processing time for electroless ruthenium plating is not particularly limited and can be set appropriately to achieve the desired film thickness. More specifically, it can be set to, for example, 30 seconds to 15 hours.

[0049] The thickness of the ruthenium plating film can be set appropriately according to the required characteristics, and is usually around 0.001 to 1.0 μm. [Examples]

[0050] The invention of this application will be described in more detail below based on examples and comparative examples, but the present invention is not limited in any way to the following examples.

[0051] (Examples 1-37, Comparative Examples 1-6) (Preparation of the plating bath) To 200 ml of deionized water, a ruthenium compound (ruthenium salt), a hydroxylamine compound and an organic compound having a hydroxyl group as stabilizers, a reducing agent, a deposition rate regulator, a pH adjuster, and a second reducing agent were added and mixed to the concentrations shown in Tables 2 to 6, and the mixture was stirred to prepare the plating baths for Examples 1 to 37 and Comparative Examples 1 to 6.

[0052] Furthermore, an appropriate amount [mL] of tetramethylammonium hydroxide solution (25%), which is a pH adjusting agent, was added to each example and comparative example until the pH reached the predetermined value (i.e., the value shown in Tables 2-6).

[0053] Furthermore, as shown in Tables 2-6, the temperature of each plating bath (plating temperature) was set to 45-85°C, and the pH to 11.0-13.3.

[0054] (Pre-processing) Before performing electroless plating, the substrate was subjected to pretreatment steps 1 and 2 shown in Table 1 in sequence. Washing with deionized water was performed between each step.

[0055] Step 1: Using MCL-12 (manufactured by Uemura Kogyo Co., Ltd., product name: Epitas® MCL-12), a degreasing and cleaning treatment was performed on the substrate (a Si wafer on which a ruthenium thin film (thickness: 10 nm) had been applied as a base layer by sputtering).

[0056] Step 2: Next, the substrate surface was activated using MRU-30 (manufactured by Uemura Kogyo Co., Ltd., product name: Epitas® MRU-30).

[0057] [Table 1]

[0058] (Electroless ruthenium plating treatment) Next, the substrates that had undergone the above-described pretreatment were immersed for 7 minutes in each of the plating baths shown in Tables 2-6 for Examples 1-37 and Comparative Examples 1-6 to form a ruthenium plating film on the surface of the substrate (on the ruthenium thin film).

[0059] (Measurement of ruthenium plating film thickness before annealing) Using an integrated ion beam system (Hitachi High-Tech, product name: MI-4050), cross-sectional processing and observation were performed, and the film thickness [nm] of the ruthenium plating film formed on the surface of the substrate was measured.

[0060] More specifically, the total thickness [nm] of the entire film, including the aforementioned underlayer (a ruthenium thin film with a thickness of 10 nm) (i.e., the total thickness of the underlayer and the ruthenium plating film formed on top of it), was measured by cross-sectional observation, and the measured value was defined as the "thickness of the ruthenium plating film before annealing." The results are shown in Tables 2 to 6.

[0061] (Measurement of oxygen content in ruthenium plating film) Next, depth profiling was performed on the ruthenium plating film formed on the substrate surface using an Auger electron spectrometer (JEOL, product name: JAMP-9500F). The oxygen content in the ruthenium plating film formed on the substrate surface was measured from the ratio of ruthenium to oxygen [at.%] at 57.6 nm etching (in SiO2 equivalent). An oxygen content of 14 at.% or less was considered to be low and good. The results are shown in Tables 2-6.

[0062] (Evaluation of plating bath stability) The stability of the ruthenium plating bath was evaluated by visual inspection to check for the deposition of ruthenium particles after electroless ruthenium plating treatment, according to the following criteria. The results are shown in Tables 2 to 6.

[0063] No ruthenium particle deposition was observed even after 3 hours following the plating process: ◎ Three hours after the plating process, a very small amount of ruthenium particles were generated: ○ Three hours after the plating process, a small amount of ruthenium particles were generated: △ Three hours after the plating process, a large amount of ruthenium particles were generated: ×

[0064] (Measurement of ruthenium plating film thickness after annealing) The substrates that had undergone the electroless ruthenium plating treatment described above were annealed for 40 minutes at 400°C under a formic acid atmosphere using a reduction reflow apparatus (Unitemp, product name: VSS-300-EP).

[0065] Next, cross-sectional processing and observation were performed on the ruthenium plating film after annealing using an integrated ion beam apparatus (Hitachi High-Tech, product name: MI-4050), and the film thickness [nm] of the ruthenium plating film formed on the substrate surface was calculated.

[0066] More specifically, the total thickness [nm] of the entire film including the aforementioned underlayer (ruthenium thin film) (i.e., the total thickness of the underlayer after annealing and the annealed ruthenium plating film formed on the underlayer) was measured by cross-sectional observation, and the measured value was defined as the "thickness of the ruthenium plating film after annealing." The results are shown in Tables 2 to 6.

[0067] (Calculation of resistivity of ruthenium plated film after annealing) Next, the sheet resistance of the annealed ruthenium film was measured using a four-probe measuring instrument (manufactured by Napson Corporation, product name: Napson RT-70V). Based on this sheet resistance value and the film thickness of the annealed ruthenium plating film (i.e., the total thickness of the substrate after annealing and the annealed ruthenium plating film formed on the substrate) [nm], the resistivity [μΩcm] of the annealed ruthenium plating film was calculated using the following formula (1). The results are shown in Tables 2 to 6.

[0068] [Mathematics 1] Resistivity of ruthenium plating film [μΩcm] = (Sheet resistance [Ω / □] × Film thickness of ruthenium plating film after annealing [nm]) / 10 (1)

[0069] Furthermore, since the resistivity of a pure ruthenium plating film is approximately 7.6 [μΩcm], if the resistivity of the film after annealing is 30 [μΩcm] or less, it is considered that most of the impurity oxygen has been removed from the ruthenium plating film formed on the surface of the substrate by annealing. Therefore, it is considered that a film equivalent to a pure ruthenium plating film has been obtained, and it can be said that low resistance equivalent to that of a pure ruthenium plating film has been achieved.

[0070] (Calculation of film shrinkage rate after annealing) Next, the film shrinkage rate (%) after annealing was calculated using the following formula (2). A film shrinkage rate of 20% or less was considered to indicate low film shrinkage and a good result. The results are shown in Tables 2-6.

[0071] [Math 2] {1-[(Thickness of the ruthenium plating film after the annealing treatment described above)[nm] / Thickness of the ruthenium plating film before the annealing treatment described above[nm])]}×100 (2)

[0072] Furthermore, in Comparative Examples 1, 3, 4, and 6, ruthenium did not precipitate on the surface of the substrate, making it impossible to measure the thickness of the ruthenium plating film before annealing, measure the oxygen content of the ruthenium plating film, calculate the resistivity of the ruthenium film after annealing, measure the thickness of the ruthenium plating film after annealing, and calculate the film shrinkage rate after annealing.

[0073] [Table 2]

[0074] [Table 3]

[0075] [Table 4]

[0076] [Table 5]

[0077] [Table 6]

[0078] As shown in Tables 2-5, in the electroless ruthenium plating baths of Examples 1-37, which use hydrazines as reducing agents, it is possible to obtain a ruthenium plating film with a low content of impurity oxygen, and to suppress film shrinkage during annealing. Furthermore, in the electroless ruthenium plating baths of Examples 1-37, which use a hydroxylamine compound (at least one of hydroxylamine sulfate and hydroxylamine chloride) and an organic compound having a hydroxyl group (at least one selected from the group consisting of gluconolactone, sorbitol, mannitol, and citric acid monohydrate) in combination as stabilizers, bath stability can be improved, and the precipitation of ruthenium can be improved.

[0079] On the other hand, as shown in Table 6, the electroless ruthenium plating baths of Comparative Examples 1, 2, and 4 do not use hydroxylamine compounds and organic compounds containing hydroxyl groups as stabilizers, resulting in poor bath stability.

[0080] Furthermore, in Comparative Example 3, the hydroxylamine compound is diethylhydroxylamine, and since hydroxylamine sulfate and hydroxylamine chloride are not used, it can be seen that the bath stability is poor.

[0081] Furthermore, in the electroless ruthenium plating bath of Comparative Example 5, dimethylamine borane is used as the reducing agent instead of hydrazines, resulting in a higher oxygen content in the ruthenium plating film and a higher film shrinkage rate during annealing.

[0082] Furthermore, in the electroless ruthenium plating bath of Comparative Example 6, sodium borohydride is used as the reducing agent instead of hydrazines, so even when a hydroxylamine compound and an organic compound having a hydroxyl group are used in combination as stabilizers, the bath stability is poor. [Industrial applicability]

[0083] The electroless ruthenium plating bath of the present invention can be suitably used, in particular, as a plating bath for forming a ruthenium plating film that forms on a barrier metal when forming a copper wiring portion of a semiconductor circuit, a thin film (cap metal) formed on copper wiring, or a liner layer that forms on a barrier metal to uniformly grow a copper seed film when copper wiring is formed by electroplating.

Claims

1. An electroless ruthenium plating bath containing at least a ruthenium compound, a reducing agent, and a stabilizer, The reducing agent is a hydrazine, The aforementioned stabilizer consists of a hydroxylamine compound and an organic compound having a hydroxyl group. The hydroxylamine compound is at least one of hydroxylamine sulfate and hydroxylamine chloride. An electroless ruthenium plating bath characterized in that the organic compound having a hydroxyl group is at least one selected from the group consisting of gluconolactone, sorbitol, mannitol, and citric acid monohydrate.

2. The electroless ruthenium plating bath according to claim 1, characterized in that the ruthenium compound is at least one selected from the group consisting of ruthenium chloride, ruthenium sulfate, and ruthenium nitrate.

3. The electroless ruthenium plating bath according to claim 1 or 2, characterized in that the concentration of the hydroxylamine compound is 1 g / L or more and 10 g / L or less, and the concentration of the organic compound having a hydroxyl group is 1 g / L or more and 20 g / L or less.

4. The electroless ruthenium plating bath according to claim 1 or 2, characterized in that the concentration of the ruthenium compound is 0.01 g / L or more and 10 g / L or less, and the concentration of the reducing agent is 0.03 mol / L or more and 1.32 mol / L or less.

5. An electroless ruthenium plating bath according to claim 1 or 2, characterized by containing a deposition rate regulator.

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