JP4472673B2 - Manufacturing method of copper wiring and electrolytic solution for copper plating - Google Patents

Description

  The present invention relates to a method of manufacturing copper wiring by embedding copper in a wiring connection hole (via hole or contact hole) or wiring groove (trench) by electroplating, and an electrolytic solution for copper plating used therefor.

In a semiconductor device, a large number of wiring grooves (trench) for connecting elements and wiring connection holes (via holes or contact holes) for electrically connecting multilayer wirings are formed.
Conventionally, aluminum has been used as a conductive material embedded in these wiring grooves and wiring connection holes. However, as semiconductor devices are highly integrated and miniaturized, their electrical resistivity is low instead of conventional aluminum. Copper (also referred to as low resistance), which has excellent electromigration resistance, has attracted attention and is being put to practical use.

Copper wiring, unlike aluminum wiring, is difficult to form a fine wiring pattern by dry etching. Therefore, a trench or a wiring pattern is to be formed in an insulating film formed on a substrate made of a silicon wafer or the like. A hole is formed, a barrier metal (diffusion prevention film) and a Cu film (underlying conductive film for obtaining conduction) are sequentially formed thereon, and then the surface is filled with copper in the grooves and holes by electroplating. A so-called damascene method is employed in which a copper layer is formed on the surface, and then the excess copper layer is polished by chemical mechanical polishing (CMP) or the like to expose the copper wiring to form a copper wiring.
Copper wiring formed by such electroplating (also referred to as electroplating) has a low impurity concentration in the film and a low electrical resistance, which is advantageous for increasing the speed of semiconductor devices.

  Conventionally, as an electrolytic solution for copper plating used in the formation of such copper wiring, three types of organic additives in a copper sulfate solution, that is, a carrier such as polyethylene glycol (PEG), bis (3-sulfopropyl) disulfide 2 An electrolytic solution in which three types of organic additives called brighteners such as sodium (SPS) and levelers such as Janus green B (JGB) and chloride ions have been added has been used.

However, the electrolytic solution containing three kinds of organic additives and chloride ions as described above needs to strictly control the concentration of each additive, and has a problem that the concentration management is very difficult. It was. In particular, organic additives react easily on the electrode and decompose easily, and the concentration tends to decrease. Therefore, concentration control is extremely difficult, and the decomposition product of the organic additive makes it difficult to fill the micropores. And problems such as deterioration of film thickness uniformity. Further, it has been pointed out that carbon (C) contained in the organic additive is incorporated as an impurity in the plating film, so that the purity of the copper film is lowered and the electromigration resistance is deteriorated.
Therefore, recently, in view of such problems, development of an electrolytic solution for copper plating having a composition as simple as possible without using organic additives and additives such as chloride ions as much as possible has been promoted.

  For example, Patent Document 1 discloses a technique for embedding copper into a micropore with only a single organic compound. However, since this electrolyte is an alkaline pyrophosphate, cyan, or sulfamine system, a pH adjuster (such as phosphoric acid or potassium hydroxide) is added. In practice, several types of additives are required.

  Patent Document 2 discloses a method of realizing good embedding characteristics in micropores by adding an appropriate amount of hydrochloric acid to a copper sulfate aqueous solution. However, even in this method, if the chlorine concentration is low, embedding cannot be achieved, and if the hydrochloric acid concentration is too high, copper is easily dissolved and the film formability is lowered. However, there is a problem that chloride ions are exhausted and management of chloride ions is difficult.

  Furthermore, Patent Document 3 discloses a method in which a dense plating film is uniformly formed in a wiring groove or a wiring hole by appropriately controlling a duty ratio in a pulse current using a plating solution containing no additive. Is disclosed. However, this method has a problem that not only the equipment cost is high, but also current control is very difficult. Furthermore, since the diffusion layer is thinned using a pulse current, uniform precipitation in the micropores can be expected, but there is a possibility that voids and seams for uniform deposition may occur.

Special table 2003-533867 gazette JP 2002-332589 A JP-A-11-97391

  In view of such a problem, the present invention has an extremely fine pore or groove (for example, a diameter of 0.15 μm to 0.2 μm and a depth of 0.1 mm without adding an organic additive or a halogen additive such as chloride ion). In addition to providing copper plating electrolytes with a new composition that can embed copper without generating voids or seams within 7 μm), and providing new copper wiring manufacturing methods using such copper plating electrolytes It is something to be done.

  The present invention relates to an electrolytic solution for copper plating used for embedding copper in a wiring connection hole or a wiring groove by electroplating, and contains 1 vol% or more of acetonitrile and 1 vol% or more of water. A method for manufacturing a copper wiring, which proposes an electrolytic solution and forms a copper wiring by electroplating copper in a wiring connection hole or a wiring groove using the electrolytic solution for copper plating. Propose.

  By using an electrolytic solution for copper plating using a mixed solvent of water and acetonitrile, even an electrolytic solution with a simple composition that does not contain organic additives and halogen additives such as chloride ions is extremely fine. Copper can be embedded in holes and grooves (for example, a diameter of 0.15 μm to 0.2 μm and a depth of 0.7 μm) without generating defects such as voids and seams. Therefore, extremely fine copper wiring can be formed without strictly controlling the concentration of the electrolyte component.

In addition, the copper film formed by electroplating using an electrolytic solution containing an organic additive or the like decreases the purity of the copper film by incorporating carbon (C) contained in the organic additive into the plating film as an impurity. According to the electrolytic solution for copper plating of the present invention, it is possible to make the composition free from organic additives and halogen additives, and acetonitrile is used. Since it does not remain in the copper film, it can be expected that the impurity concentration of the copper wiring is particularly low and the electric resistance is further reduced. Furthermore, the orientation of the copper wiring embedded using the electrolytic solution for copper plating of the present invention can be expected to be a wiring excellent in electromigration resistance because the (111) plane is preferentially oriented.
Therefore, the copper wiring formed according to the present invention can be particularly suitably used in an integrated circuit or an electronic circuit board such as a printed board.

In the present invention, “electroplating” includes all methods in which an electrolytic solution containing an ionized metal is energized to deposit the plated metal on the surface of the cathode.
In addition, in the present invention, when “X to Y” (X and Y are arbitrary numbers) is described, it means “X or more and Y or less” unless otherwise specified. It includes the meaning of “small”.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, although the manufacturing method of a copper wiring is demonstrated as a preferable example of embodiment of this invention, this invention is not limited to embodiment described below.

Here, as an example of an embodiment of the present invention, copper in the wiring connection hole or wiring groove is obtained by electroplating using 1 vol% or more of acetonitrile, 1 vol% or more of water, and an electrolytic solution containing copper ions. A method of manufacturing a copper wiring in which copper wiring is formed by embedding copper will be described.
More specifically, as shown in FIG. 1, an insulating film 1B such as an oxide film made of an insulating material is formed on a substrate 1A made of a silicon wafer or the like, and a wiring pattern in the insulating film 1B is to be formed. Grooves or holes 2 are provided (see (A) in the figure), and then a barrier metal film (diffusion prevention film) 3 made of Ti, Ta, W, or a nitride thereof, and a Cu base conductive film (conducting) (Underlying conductive film for obtaining) 4 (see (B) in the figure), and then electroplating using the above-mentioned electrolytic solution, while copper is embedded in the groove or hole 2 A copper layer 5 is formed on the surface of the substrate 1 (see (C) in the figure), and then the extra copper layer 5 is removed by, for example, chemical mechanical polishing (CMP) to expose the copper wiring 6 to form the copper wiring. It is a manufacturing method of forming (see (D) in the figure). Furthermore, in order to improve migration resistance, a metal, an oxide, or an organic substance may be stacked on the exposed copper wiring 6.

The size of the wiring connection hole (via) or the wiring groove (trench) is not particularly limited, but the manufacturing method of the present invention has a hole diameter or groove width of 0.15 μm to 0.2 μm and a depth of 0.7 μm, for example. Even such extremely fine holes or grooves can be sufficiently embedded. Therefore, it can be sufficiently embedded in a hole or groove having a diameter that is at least larger than that or a shallow depth. For example, for holes or grooves for through-electrodes such as SoC (system on chip), SiP (system in package), MEMS (mems, mechano-electric microsystem), etc., whose hole diameter or groove width is 100 μm and depth is 200 μm Can also be embedded sufficiently. Further, for example, it can be sufficiently embedded in a hole or groove of via filling plating of a printed wiring board having a hole diameter or groove width of 200 μm and a depth of 50 μm. On the contrary, the limitation of the present invention does not mean that the hole diameter or the groove width is 0.15 μm to 0.2 μm and the depth is 0.7 μm.
The shape of the wiring connection hole (via) or wiring groove (trench) is not particularly limited. Incidentally, since it is difficult to provide a hole or groove having the same diameter from the opening to the back when the hole diameter or groove width is extremely fine with a hole diameter or groove width of 0.15 μm to 0.2 μm, normally, FIG. As shown in FIG. 4, the cross-sectional shape is narrowed from the opening toward the bottom.

(Electrolyte)
As an electrolytic solution for copper plating (hereinafter referred to as “the present electrolytic solution”) used in this embodiment, copper ions to be electrodeposited are added to an acetonitrile aqueous solution that is a mixed solvent of 1 vol% or more of acetonitrile and 1 vol% or more of water. It is preferable to use an electrolytic solution containing sulfate ions and copper ions in water and acetonitrile as a solvent, and substantially free of halogen ions and organic additives.

  In this case, “substantially does not contain” means that it is not actively added, and means that it is inevitably included. In terms of specific concentration, it is preferably 1 ppm or less.

Acetonitrile (CH ₃ CN) is a water-soluble organic cyanide compound called ethanenitrile or methyl cyanide.
In addition, even if another water-soluble organic substance is used as a main component instead of acetonitrile, the same effect as that of acetonitrile can be expected. Examples of the “water-soluble organic solvent” in this case, that is, an organic solvent that is mutually soluble in water include alcohols such as methanol, ethanol, n-propanol, isopropanol, isobutanol, ethylene glycol, dipropylene glycol, and propylene glycol, for example Examples thereof include ketones such as acetone and ethyl methyl ketone, and other cyan organic solvents such as diethylene glycol, tetrahydrofuran, dioxane, and acetonitrile. Acetonitrile is proposed.

  It is important that the concentration of acetonitrile in the electrolytic solution is 1 vol% or more as described above, and the mixing ratio of acetonitrile with respect to the total amount of acetonitrile and water is preferably 1 to 40 vol%, particularly 1 to 26 vol%. It is preferable to adjust or control so that

Moreover, as a copper compound which provides a copper ion, water-soluble copper salts, such as alkaline copper cyanide, copper pyrophosphate, acidic copper borofluoride, copper sulfate, are preferable, and especially copper sulfate containing copper sulfate and sulfuric acid. An aqueous solution is preferred.
These can be premixed with acetonitrile.

  As a preferred specific example of the electrolytic solution, an electrolytic solution obtained by diluting an electrolytic solution containing an aqueous copper sulfate solution and acetonitrile with pure water to have a desired composition concentration suitable for the purpose can be given.

By using a mixed solvent of water and acetonitrile as described above as an electrolytic solution for copper plating, even an electrolytic solution having a simple composition that does not contain halogen additives such as organic additives and chloride ions is extremely fine. It becomes possible to embed copper in the hole or groove.
However, it is optional to add organic additives, halogen additives, and other additives in an appropriate combination. For example, additives such as brighteners, complexing agents, buffering agents, conductive agents, organic compounds (such as glue, gelatin, phenolsulfonic acid, molasses), polyhydric alcohols, and titanium can be added to the electrolyte.

(cathode)
The material of the cathode used in the present embodiment, that is, the substrate to be plated is not particularly limited. Since the substrate material of a semiconductor device has a structure in which an insulating film such as an oxide film is usually formed on a substrate made of a silicon wafer or the like, continuity cannot be obtained by itself and electroplating cannot be performed. Therefore, it is general to form a base conductive film by laminating a conductive material such as copper on the insulating film by sputtering or other means.

(anode)
The material as the anode, that is, the counter electrode used in the present embodiment is not particularly limited. For example, in addition to copper, insoluble electrodes such as platinum and platinum-plated titanium, and other electrode plates can be exemplified, but copper is particularly preferable.

(Electrolysis conditions, etc.)
The electrolysis conditions and the like in this embodiment will be described.

(Amount of acetonitrile)
It is important to control the acetonitrile concentration in the electrolytic solution to 1 vol% or more, preferably 5 vol% or more, and particularly preferably 10 vol% or more. Although an upper limit is not specifically limited, It is thought that it is about 40 vol%.
The acetonitrile concentration in the electrolytic solution affects the uniform electrodeposition, that is, the property that the electrodeposition does not change even if the distance between the counter electrode and the plating surface changes. In other words, since the current density changes if the distance between the counter electrode and the plating surface changes, this affects the property that the electrodeposition does not change even if the current density changes. Considering the electrodeposition in the hole or groove, the distance from the counter electrode and the current density are different between the vicinity of the opening and the depth of the hole or groove. A plating film can be formed and can be embedded more suitably. From this viewpoint, the acetonitrile concentration in the electrolytic solution is preferably 5 vol% or more, and more preferably 10 vol% or more.

(H ₂ SO ₄ concentration)
The H ₂ SO ₄ concentration can be adjusted as appropriate, but is usually 0.01 mol / L or more, preferably 0.1 mol / L to 2 mol / L.

(Concentration of +1 valent metal (copper) in the electrolyte)
It is important to control the concentration of +1 valent metal (copper) in the electrolyte, that is, the concentration of the lowest valent metal in the electrolyte having a valence of 2 or more to 0 to 0.05 mol / L. In particular, it is particularly preferable to control it to be lower than 0.02 mol / L.
Adjustment of the concentration of +1 valent metal (copper) in the electrolyte is, for example, adjustment of the amount of electrolyte circulation (electrolyte not containing +1 valent metal (copper)), adjustment of electrolysis time, insoluble anode Can be adjusted by the use of. However, it is not limited to these methods.

(Concentration of + divalent metal (copper) in the electrolyte)
+ Concentration of divalent metal (copper) in the electrolyte solution, that is, in the metal having two or more valences, the concentration of the metal other than the lowest valent metal in the electrolyte solution is 0.01 mol although it depends on the current density. / L to 0.2 mol / L is preferable.
This electrolyte has a property of corroding the Cu underlying conductive film formed on the surface of the wiring connection hole or the wiring groove. When the corrosion rate is increased, the Cu underlying conductive film is corroded to provide sufficient conduction during electroplating. There is a possibility that it may not be obtained, resulting in poor embedding. As a result of the inventor's research, the concentration of +2 metal (copper) in the electrolyte affects the corrosion rate, and as the concentration of +2 metal (copper) in the electrolyte increases, the corrosion rate tends to increase. Therefore, from this point of view, the concentration of +2 metal (copper) in the electrolyte is more preferably controlled in the range of 0.01 to 0.15 mol / L, and more preferably in the range of 0.05 to 0.10 mol / L. It is particularly preferable to do this.

(Electrolysis temperature)
The electrolysis temperature, that is, the temperature of the electrolytic solution is not particularly limited, and may be 25 ° C. or higher. Especially, it is preferable to control so that it may become 25-45 degreeC in order to reduce manufacturing cost and evaporation of an organic component.

(Current density)
The current density is not particularly limited, but is preferably controlled to 0.005 A / cm ² or more. Although the upper limit is not particularly limited, it is considered that about 0.5 A / cm ² is a realistic upper limit. More preferably, the current density is preferably controlled according to the electrolysis temperature. Specifically, when the electrolysis temperature is 25 ° C. or higher and lower than 35 ° C., 0.005 to 0.02 A / cm ² , and the electrolysis temperature is 35 When the temperature is higher than or equal to ° C., it is preferably controlled to 0.02 A / cm ² or higher.

(Electrolysis time)
The electrolysis time (energization time) is not particularly limited. It is preferable to adjust appropriately according to the size and shape of the holes and grooves.

(Preferable electrolysis conditions)
Taking the above points together, as an example of preferable electrolysis conditions, the acetonitrile concentration in the electrolytic solution is 8 to 12 vol%, the +1 valent copper concentration in the electrolytic solution is 0 to 0.02 mol / L, and The + 2-valent copper concentration in the electrolytic solution is 0.05 to 0.15 mol / L, the electrolysis temperature is 25 to 45 ° C., and the current density is 0.005 A / cm ^{2 to} 0.035 A / cm ^2. Can be mentioned.

(apparatus)
The configuration of the electroplating apparatus can be appropriately designed and is not particularly limited. For example, a plating tank containing an electrolytic solution is provided. The plating tank includes an electrolytic solution drain part and an electrolytic solution supply part. In the plating tank, a substrate holder for holding a substrate (for example, a semiconductor wafer), an anode of a power source An electroplating apparatus in which an anode electrode to which is connected is disposed.

(Features of the obtained copper wiring)
According to this electrolytic solution, even though it is substantially free of organic additives and halogen additives such as chloride ions, extremely fine pores or grooves (for example, a diameter of 0.15 μm to 0.2 μm and a depth of 0.1 μm). 7 μm), copper can be buried without generating defects such as voids and seams, and extremely fine copper wiring can be formed.
In addition, the copper wiring obtained in the present embodiment has a feature that the purity is high, and even if acetonitrile is added to the electrolytic solution, no acetonitrile remains in the obtained copper wiring. One. Therefore, a copper thin film having a low impurity concentration and a sufficiently low specific resistance can be obtained.
Furthermore, the orientation of the copper wiring obtained in this embodiment can be expected to be a wiring excellent in electromigration resistance because the (111) plane is preferentially oriented.
Therefore, the copper wiring formed according to the present invention can be effectively used for manufacturing an electronic material, for example, an integrated circuit such as an IC, LSI, or CPU, or a circuit board on which the integrated circuit is mounted.

  Hereinafter, although this invention is demonstrated based on a test result (equivalent to an Example), the scope of the present invention is not limited to the following test result.

(Test 1)
Using the following apparatuses, electroplating was performed on the following samples (substances to be plated) while variously changing the electrolysis conditions as shown in Table 1, and the embeddability in the wiring grooves was compared for each sample.

As shown in FIG. 2, a micro cell Model I type manufactured by Yamamoto Kakin Tester Co., Ltd. was used for the plating cell, and phosphorous copper was used for the anode.
As shown in FIG. 3, on the cathode, 185 wiring grooves having a groove width of 190 nm and a depth of 700 nm are formed at intervals of 190 nm on a silicon wafer plate (11 mm × 15 mm × 0.8 mm) whose surface is subjected to an oxide film treatment. Then, TaN and Cu were sequentially sputtered on the surface to form a Ta barrier layer and a Cu seed layer.
For current control, a potentiostat (HA-151) manufactured by Hokuto Denko Co., Ltd. was used, and electroplating was performed under the conditions shown in Table 1 while the cathode was swung at about 0.8 Hz.
Moreover, after mixing copper sulfate aqueous solution and acetonitrile, the electrolyte solution was prepared with the composition shown in Table 1 by diluting with pure water or adding an additive.

The embedding property of the sample after plating was observed by a cross-section using a focused ion beam processing observation apparatus / scanning ion microscope manufactured by SII Nano Technology, Inc., and evaluated according to the following criteria.
A: Copper filling rate in the groove is almost 100%
○: Copper filling rate in the groove is 80% or more and less than 100% Δ: Copper filling rate in the groove is 50% or more and less than 80% ×: Copper filling rate in the groove is less than 50%

For samples whose embeddability was evaluated to be less than Δ, the cause was examined.
Samples 1 and 2 have a low Cu (II) concentration and are partly accompanied by hydrogen generation.
Since sample 4 is not mixed with acetonitrile, it is considered that the throwing power is poor and the embedding property is lowered.
Since sample 5 has a low acetonitrile concentration, it is considered that the throwing power is poor and the embedding property is lowered.
Since Sample 8 has a high current density and partly generates hydrogen, it is considered that the embedding property is slightly lowered.
Sample 9 is considered to have reduced embeddability because the current density is too high and hydrogen is generated.
Sample 14 is Cu
The electrolytic solution (I) is considered to have reduced embeddability due to a decrease in throwing power.
Sample 15 is Cu
It is considered that (I) decreased the throwing power and the embedding property slightly decreased.
It is considered that the sample 17 has a high Cu (II) concentration, so that the corrosivity is increased and the embedding property is lowered.
In Sample 18, it is considered that Cl ⁻ impeded the effect of acetonitrile and the embedding property was lowered.
In Sample 22, it is considered that MPS (3-mercapto-1-propanesulfonate) inhibits the effect of acetonitrile and the embedding property is slightly reduced.

From the results in Table 1, for example, the following points were found.
It is important to control the acetonitrile concentration in the electrolytic solution to 1.0 vol% or more, and chloride ions and MPS in the electrolytic solution inhibit the effect of acetonitrile. I understood. On the contrary, it was found that the embedding property is not inhibited even when an organic additive such as polyethylene glycol is added.
It is important to control the concentration of the +1 valent metal (copper) in the electrolyte solution to be lower than 0.1 mol / L, preferably it is important to control to 0 to 0.05 mol / L, It turned out that it is preferable to control so that it may become below 0.02 mol / L especially.
It is understood that the concentration of +2 metal (copper) in the electrolyte is preferably controlled to be lower than 0.24 mol / L, and preferably in the range of 0.05 to 0.1 mol / L. It was.
It has been found that it is important to set the current density lower than 40 mA / cm ² , and it is preferable to set it to 30 mA / cm ² or less.

(Test 2: Acetonitrile concentration dependence in the Hull cell test)
Copper obtained by applying a current of 1 A for 10 minutes while changing the acetonitrile concentration of the electrolyte using a Hull Cell water tank manufactured by Yamamoto Gold Tester Co., Ltd., using a copper plate as the cathode and an oxygen-free copper plate as the anode. The appearance of the plating film was photographed with a digital camera.

  As a result, it was found that the acetonitrile concentration in the electrolytic solution was preferably 5 vol% or more, and more preferably 10 vol% or more.

(Test 3: Cu (II) concentration dependence on corrosion rate)
A tough pitch copper plate covered with a masking tape so that the exposed area was 7.5 cm ² was used as a sample for measuring the corrosion rate.
This corrosion measurement sample was added to electrolytes (21 ° C.) having different H ₂ SO ₄ concentrations of 0.1 mol / L, acetonitrile concentrations of 11 vol%, +1 valent copper ion concentrations of 0 mol / L, and different +2 valent copper ion concentrations. Soaked for hours. The corrosion rate was calculated from the weight difference before and after immersion of the sample taken out of the electrolyte solution after 12 hours.

  As a result, the Cu (II) concentration, that is, the concentration of + 2-valent copper ions in the electrolytic solution affects the corrosion rate, and the corrosion rate increases as the concentration of + 2-valent copper ions in the electrolytic solution increases. From this point of view, the Cu (II) concentration, that is, the concentration of +2 valent copper ions in the electrolytic solution is controlled in the range of 0.01 to 0.15 mol / L, particularly 0.05 to 0.10 mol / L. It has been found preferable.

(A)-(D) are sectional drawings explaining the manufacturing method of copper wiring in order of a process. It is the figure explaining the structure of the cell used by the Example and the comparative example. It is the figure explaining the structure of the cathode used by the Example and the comparative example. It is the figure which showed the color change of the cathode according to the distance from an anode as a result of the test 2 for every density | concentration of acetonitrile. 4 is a graph showing the relationship between Cu (II) concentration and corrosion rate as a result of Test 3.

Explanation of symbols

1A Substrate 1B Insulating film 2 Groove or hole 3 Barrier metal film 4 Underlying conductive film 5 Copper layer 6 Copper wiring

Claims (7)

And 1 vol% or more of acetonitrile, and 1 vol% or more of water, and sulfuric acid, and copper ions with including copper plating electrolyte by electroplating copper wiring connection hole or the wiring groove, a copper wire Forming a copper wiring. Method for producing a copper wiring of claim 1, wherein the Cu (I) concentration in the electrolytic solution is electroplating controlled to be 0~0.05mol / L. Water, acetonitrile, containing sulfuric acid and copper ions, and copper according to claim 1 or 2, wherein the electroplating using the copper plating electrolyte containing no halogen ions and organic additives substantially Wiring manufacturing method. The method for producing a copper wiring according to claim 2, wherein the sulfuric acid concentration is 0.05 mol / L to 2 mol / L. The method for producing a copper wiring according to any one of claims 1 to 3, wherein electroplating is performed by controlling the mixing ratio of acetonitrile to the total amount of acetonitrile and water to be 1 to 40 vol%. Electronic circuit boards and integrated circuits having a copper wiring is formed configured to the substrate by the manufacturing method of copper wire according to any one of claims 1 to 5. An electrolytic solution for copper plating used when copper is embedded in a wiring connection hole or a wiring groove by electroplating, and includes 1 vol% or more of acetonitrile, 1 vol% or more of water, sulfuric acid, and copper ions. Electrolytic solution for copper plating.

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