Electrolytic copper plating solution, method for producing the same, and electrolytic copper plating method

Abstract

The present invention provides: an electrolytic copper plating solution which contains (A) sulfate ions, (B) a compound represented by general formula (1) and (C) copper ions, wherein the content of the component (B) is from 0.3 to 50 parts by mass and the content of the component (C) is from 5 to 50 parts by mass, both relative to 100 parts by mass of the content of the component (A); a method for producing this electrolytic copper plating solution; and an electrolytic copper plating method which uses this electrolytic copper plating solution. (In the formula, each of R1 and R2 independently represents a hydrogen atom, a sodium atom, a potassium atom or an alkyl group having from 1 to 5 carbon atoms; and n represents 1 or 2.)

Description

Technical Field

[0001] The present invention relates to an electrolytic copper plating solution containing sulfuric acid and a compound having a specific structure, a method for producing the same, and an electrolytic copper plating method using the electrolytic copper plating solution.

Background Art

[0002] Conventionally, in the formation of fine wirings, through silicon vias (TSVs), and bumps in highly integrated electronic circuits, a method of embedding a metal in patterns such as grooves and holes has been used. Electrolytic copper plating is one of the typical methods for embedding a metal. Among them, electrolytic copper plating for embedding copper as a metal is widely used. In circuit formation by electrolytic copper plating, in order to obtain high connection reliability, it is required to form a copper layer with high purity and good surface flatness.

[0003] As a conventionally known electrolytic copper plating solution, for example, Patent Document 1 discloses a copper plating bath containing 0.8 M of copper sulfate and 0.5 M of isethionic acid. Further, Patent Document 2 discloses a copper plating bath containing copper oxide and isethionic acid, and Patent Document 3 discloses a copper plating bath containing copper sulfate pentahydrate, sulfuric acid, hydrochloric acid, and a trace amount of isethionic acid.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when performing electrolytic copper plating using the electrolytic copper plating solutions described in Patent Documents 1 to 3 above, there is a problem in that a copper layer excellent in surface flatness cannot be obtained, and furthermore, the purity of the obtained copper layer is low. Therefore, an object of the present invention is to provide an electrolytic copper plating solution capable of obtaining a copper layer having high purity and excellent surface flatness.

Means for Solving the Problems

[0006] As a result of repeated studies, the present inventors have found that the above object can be achieved by using an electrolytic copper plating solution containing sulfate ions, copper ions, and a compound having a specific structure in a certain mixing ratio, and have completed the present invention.

[0007] That is, according to the present invention, there is provided an electrolytic copper plating solution containing (A) sulfate ions, (B) a compound represented by the following general formula (1), and (C) copper ions, wherein the content of the component (B) is 0.3 to 50 parts by mass and the content of the component (C) is 5 to 50 parts by mass with respect to 100 parts by mass of the content of the component (A).

[0008]

Chemical formula

[0009] (In the formula, R 1 and R 2 each independently represent a hydrogen atom, a sodium atom, a potassium atom, or an alkyl group having 1 to 5 carbon atoms, and n represents 1 or 2.)

[0010] Further, according to the present invention, there is provided an electrolytic copper plating method using the above electrolytic copper plating solution.

Effects of the Invention

[0011] With the electrolytic copper plating solution of the present invention, a copper layer having high purity and excellent surface flatness can be obtained.

Brief Description of the Drawings

[0012]

Figure 1

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail.

[0014] <Electrolytic Copper Plating Solution> The electrolytic copper plating solution of the present invention is an electrolytic copper plating solution containing, as essential components, (A) sulfate ions (hereinafter also referred to as “component (A)”), (B) a compound represented by the above general formula (1) (hereinafter also referred to as “component (B)”), and (C) copper ions (hereinafter also referred to as “component (C)”).

[0015] The source of component (A) (sulfate ions) is not particularly limited. For example, sulfuric acid, copper sulfate, iron sulfate, lead sulfate, silver sulfate, calcium sulfate, potassium sulfate, sodium sulfate, barium sulfate, magnesium sulfate, aluminum sulfate, nickel sulfate, and mixtures thereof, and at least one selected from the group consisting of hydrates thereof can be used. One kind of the source of component (A) can be used alone or in combination of two or more kinds. Since a copper layer with higher purity and excellent surface flatness can be obtained, it is preferable to use at least one of sulfuric acid, copper sulfate or copper sulfate pentahydrate as the source of component (A), and it is more preferable to use a combination of sulfuric acid and copper sulfate or copper sulfate pentahydrate.

[0016] Component (B) is a compound represented by the following general formula (1).

[0017]

Chemical formula

[0018] (In the formula, R 1 and R 2 each independently represent a hydrogen atom, a sodium atom, a potassium atom or an alkyl group having 1 to 5 carbon atoms, and n represents 1 or 2.)

[0019] In the above general formula (1), R 1 and R 2 each independently represent a hydrogen atom, a sodium atom, a potassium atom, or an alkyl group having 1 to 5 carbon atoms. The alkyl group having 1 to 5 carbon atoms represented by R 1 and R 2 can include, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a neopentyl group, and the like. Since a copper layer having better surface flatness can be obtained, R 1 is preferably a hydrogen atom or a sodium atom, and more preferably a hydrogen atom. R 2 is preferably a hydrogen atom.

[0020] In the above general formula (1), n represents 1 or 2. Since a copper layer having better surface flatness can be obtained, n is preferably 2.

[0021] Preferred specific examples of the compound represented by the above general formula (1) include, for example, the following Compounds No. 1 to No. 12. In the following compounds, "Me" represents a methyl group, "Et" represents an ethyl group, and "iPr" represents an isopropyl group.

[0022]

Chemical formula

[0023] Among the above compounds, Compounds No. 2, 7, and 8 are preferred, and Compound No. 7 is more preferred.

[0024] (C) component (copper ion) sources are not particularly limited. For example, at least one selected from the group consisting of copper sulfate, copper chloride, copper bromide, copper hydroxide, and mixtures thereof, and hydrates thereof can be used. One kind of the source of component (C) can be used alone or in combination of two or more kinds. Since a copper layer with higher purity and excellent surface flatness can be obtained, it is preferable to use copper sulfate or copper sulfate pentahydrate as the source of component (C).

[0025] In the electrolytic copper plating solution, the content of component (B) is 0.3 to 50 parts by mass with respect to 100 parts by mass of the content of component (A). Since a copper layer with more excellent surface flatness can be obtained, the content of component (B) is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass with respect to 100 parts by mass of the content of component (A).

[0026] In the electrolytic copper plating solution, the content of component (C) is 5 to 50 parts by mass with respect to 100 parts by mass of the content of component (A). Since a copper layer with higher purity and excellent surface flatness can be obtained, the content of component (C) is preferably 10 to 40 parts by mass, more preferably 20 to 30 parts by mass with respect to 100 parts by mass of the content of component (A). Since a copper layer with higher purity and excellent surface flatness can be obtained, the content of component (B) is preferably 1 to 200 parts by mass, more preferably 5 to 100 parts by mass, most preferably 10 to 70 parts by mass with respect to 100 parts by mass of the content of component (C).

[0027] (A) component (sulfate ion) concentration in the electrolytic copper plating solution is not particularly limited, but is usually 10 g / L to 500 g / L, preferably 50 g / L to 350 g / L, more preferably 100 g / L to 250 g / L, and still more preferably 110 g / L to 200 g / L.

[0028] The concentration of the component (B) in the electrolytic copper plating solution is not particularly limited, but is usually 0.3 g / L to 80 g / L, preferably 1 g / L to 60 g / L, more preferably 5 g / L to 40 g / L, and still more preferably 5 g / L to 35 g / L.

[0029] The concentration of the component (C) in the electrolytic copper plating solution is not particularly limited, but is usually 5 g / L to 250 g / L, preferably 10 g / L to 150 g / L, more preferably 20 g / L to 80 g / L, and still more preferably 25 g / L to 70 g / L.

[0030] The electrolytic copper plating solution of the present invention may contain, as components other than the above components (A) to (C), a chloride ion source, a plating accelerator, a plating inhibitor, and the like.

[0031] The chloride ion source is not particularly limited, and examples thereof include hydrogen chloride and sodium chloride. The concentration of the chloride ion source is preferably 5 mg / L to 200 mg / L, and more preferably 20 mg / L to 150 mg / L in the electrolytic copper plating solution.

[0032] The plating accelerator is not particularly limited, and examples thereof include compounds represented by the following general formulas (2) to (4).

[0033] XO3S-R-SH (2) XO3-Ar-S-S-Ar-SO3X (3)

[0034] (In the above general formulas (2) and (3), R is a substituted or unsubstituted alkyl group, preferably an alkyl group having 1 to 6 carbon atoms, still more preferably an alkyl group having 1 to 4 carbon atoms, Ar is a substituted or unsubstituted aryl group, for example, a substituted or unsubstituted phenyl group or naphthyl group, and X is a counter ion, for example, sodium or potassium.)

[0035]

Chemical formula

[0036] (In the above general formula (4), R 21 and R 22 are a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 9 carbon atoms which may have a substituent having 1 to 3 carbon atoms, or an aryl group which may have a substituent having 1 to 3 carbon atoms, M represents an alkali metal, ammonium or a monovalent organic ammonium, and n represents a number from 1 to 7.)

[0037] Among the above, from the viewpoint of having a high effect of promoting the formation of the copper layer, as the plating accelerator, sodium 3,3'-dithiobis(1-propanesulfonic acid) (hereinafter sometimes abbreviated as SPS) is preferable.

[0038] The concentration of these plating accelerators is preferably 0.1 mg / L to 100 mg / L, more preferably 0.5 mg / L to 50 mg / L, and most preferably 1 mg / L to 30 mg / L in the electrolytic copper plating solution.

[0039] As the plating inhibitor, for example, an oxygen atom-containing polymer organic compound can be used. Specifically, polyethylene glycol, polypropylene glycol, polyoxyethylene-polyoxypropylene random copolymer, polyoxyethylene-polyoxypropylene block copolymer, etc. can be mentioned. Among these, polyethylene glycol is preferable. From the viewpoint of further improving the effect of the present invention, the molecular weight of these oxygen atom-containing polymer organic compounds is preferably 500 to 100,000, and more preferably 1,000 to 10,000. In particular, polyethylene glycol having a molecular weight of 1,000 to 10,000 is most preferable. From the same viewpoint, the concentration of the oxygen atom-containing polymer organic compound is preferably 50 mg / L to 5,000 mg / L, and more preferably 100 mg / L to 3,000 mg / L in the electrolytic copper plating solution.

[0040] In the present invention, a well-known solvent can be used as the solvent of the electrolytic copper plating solution. Examples of the solvent include water; alcohols such as methanol, ethanol, isopropyl alcohol, and n-butanol; acetate esters such as ethyl acetate, butyl acetate, and methoxyethyl acetate; ethers such as tetrahydrofuran, tetrahydropyran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, dibutyl ether, and dioxane; ketones such as methyl butyl ketone, methyl isobutyl ketone, ethyl butyl ketone, dipropyl ketone, diisobutyl ketone, methyl amyl ketone, cyclohexanone, and methyl cyclohexanone; and hydrocarbons such as hexane, cyclohexane, methyl cyclohexane, dimethyl cyclohexane, ethyl cyclohexane, heptane, octane, toluene, and xylene. These solvents may be used alone or in combination of two or more. Among the above solvents, water and alcohols are preferred, and water is more preferred.

[0041] In the electrolytic copper plating solution of the present invention, other additives known to be capable of being added to the plating solution can be arbitrarily used within a range that does not inhibit the effects of the present invention.

[0042] Examples of other additives include anthraquinone derivatives, cationic surfactants, nonionic surfactants, anionic surfactants, amphoteric surfactants, alkane sulfonic acids, alkane sulfonates, alkane sulfonic acid esters, hydroxyalkane sulfonic acid esters, and hydroxyalkane sulfonic acid organic acid esters (excluding compounds corresponding to component (B) of the present invention). The concentration of these other additives is preferably 0.1 mg / L to 500 mg / L, and more preferably 0.5 mg / L to 100 mg / L in the electrolytic copper plating solution.

[0043] The pH of the electrolytic copper plating solution is not particularly limited, but is usually under acidic conditions of 4 or less, preferably under acidic conditions of 3 or less, and more preferably under strongly acidic conditions of 2 or less. For the measurement of pH, a pH meter LAQUA F-70 manufactured by HORIBA, etc. can be used. The temperature at the time of measuring pH may be about room temperature.

[0044] <Electrolytic Copper Plating Method> Next, the electrolytic copper plating method using the electrolytic copper plating solution of the present invention will be described. The electrolytic copper plating method of the present invention can be carried out in the same manner as the conventional electrolytic copper plating method except that the electrolytic copper plating solution of the present invention is used as the electrolytic copper plating solution. Here, an electrolytic copper plating method for forming a copper layer on a substrate to be plated will be described.

[0045] As the electrolytic copper plating apparatus, for example, a paddle stirring type plating apparatus may be used. The plating tank of the electrolytic copper plating apparatus is filled with the electrolytic copper plating solution of the present invention, and the substrate to be plated is immersed in the electrolytic copper plating solution. As the substrate to be plated, for example, one having a resist pattern formed using a photoresist on a Si substrate with a copper seed layer can be used.

[0046] At this time, for example, the temperature of the electrolytic copper plating solution is 10°C to 70°C, preferably 20°C to 60°C, and the current density is 1 A / dm 2 ~70 A / dm 2 、preferably 5 A / dm 2 ~50 A / dm 2 、more preferably 15 A / dm 2 ~35 A / dm 2 within the range. Also, as the stirring method of the electrolytic copper plating solution, air stirring, rapid liquid flow stirring, mechanical stirring by a stirring blade, etc. can be used.

[0047] Under the conditions as described above, by embedding copper in the opening of the resist pattern, a copper layer with high purity and excellent surface flatness can be formed on the substrate to be plated.

[0048] The plated products manufactured using the electrolytic copper plating method of the present invention are not particularly limited. For example, automotive industry materials (heat sinks, carburetor parts, fuel injectors, cylinders, various valves, inside engines, etc.), electronic industry materials (contacts, circuits, semiconductor packages, printed circuit boards, thin film resistors, capacitors, hard disks, magnetic materials, lead frames, nuts, magnets, resistors, stems, computer parts, electronic parts, laser oscillation elements, optical memory elements, optical fibers, filters, thermistors, heating elements, heating elements for high temperatures, varistors, magnetic heads, various sensors (gas, temperature, humidity, light, speed, etc.), MEMS, etc.), precision instruments (copier parts, optical instrument parts, watch parts, etc.), aerospace and marine materials (hydraulic equipment, screws, engines, turbines, etc.), chemical industry materials (balls, gates, plugs, checks, etc.), various molds, machine tool parts, vacuum equipment parts, etc. can be mentioned. The electrolytic copper plating method of the present invention is preferably used for electronic industry materials that particularly require fine patterns. Among them, it is more preferably used in the manufacture of semiconductor packages and printed circuit boards typified by TSV formation, bump formation, etc., and most preferably used in semiconductor packages.

Examples

[0049] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited in any way by the following Examples and the like.

[0050] [Examples 1 to 9] Sulfuric acid, component (B), copper sulfate pentahydrate, hydrochloric acid, SPS, PEG4000 and water were mixed so as to have the compositions shown in Table 1 to obtain Example Copper Plating Solutions 1 to 9. In addition, the remainder in the composition of the copper plating solutions shown in Table 1 is water, and the concentration of each component was adjusted with water. Further, the SPS (manufactured by Tokyo Chemical Industry Co., Ltd.) used in the examples is 3,3'-dithiobis(1-propanesulfonic acid sodium), and PEG4000 (manufactured by ADEKA Corporation) is polyethylene glycol having a weight average molecular weight of 3,600 to 4,400. Note that the pH values of the plating baths in the Examples and Comparative Examples described in Tables 1 and 2 below were all in the range of 0 to 1.

[0051] [Table 1]

[0052] [Comparative Examples 1 - 8] Sulfuric acid, component (B) or other components, copper sulfate pentahydrate, hydrochloric acid, SPS, PEG4000, and water were mixed to obtain Comparative Copper Plating Solutions 1 - 8 so as to have the compositions shown in Table 2. Note that the remainder in the composition of the copper plating solutions shown in Table 2 was water, and the concentrations of each component were adjusted with water. Also, the SPS used in the Comparative Examples was 3,3'-dithiobis(sodium 1-propanesulfonate), and PEG4000 was polyethylene glycol having a weight average molecular weight of 3,600 - 4,400. The Comparative Compounds 1 - 5 used as other components are the compounds shown below.

[0053] [Chemical Formula]

[0054] [Table 2]

[0055] [Evaluation Examples 1 - 9, Comparative Evaluation Examples 1 - 8] As an electrolytic copper plating apparatus, a paddle stirring type plating apparatus was used, and the plating baths of the paddle stirring type plating apparatus were filled with the electrolytic copper plating solutions of Examples 1 - 9 and Comparative Examples 1 - 8, respectively. The substrate to be plated was immersed in each of the electrolytic copper plating solutions. As the substrate to be plated, a substrate in which a resist pattern (shape: having an opening with a circular cross-section, opening diameter: 75 μm) was formed using a photoresist on a Si substrate with a copper seed layer was used. Next, copper was embedded in the resist opening by the electrolytic copper plating method under the following plating conditions, and a copper layer was formed on the substrate to be plated.

[0056] (Plating Conditions) (1) Hole diameter: 75 μm (2) Current density: 18 A / dm 2 (3) Bath temperature: 35 °C (4) Plating time: The time until the minimum height (L Min ) of the copper layer reaches 40 μm

[0057] As shown in Fig. 1, by observing the cross-section of the copper layer 1 formed on the surface of the substrate to be plated 2 with a laser microscope (manufactured by Keyence Corporation, model number: VK-9700) according to Evaluation Examples 1 to 9 and Comparative Evaluation Examples 1 to 8, the minimum height 3 (L Min ) and the maximum height 4 (L Max ) of the copper layer 1 were measured, and ΔL was calculated by the following formula. In addition, the content of organic residues in the obtained copper layer was measured by secondary ion mass spectrometry. ΔL = L Max - L Min

[0058]

Table 3

[0059] In Table 3, the smaller the value of ΔL, the better the surface flatness of the formed copper layer. Also, the smaller the value of organic residues, the higher the purity of the formed copper layer. From the results in Table 3, it was found that in Evaluation Examples 1 to 9, compared with Comparative Evaluation Examples 1 to 7, the content of organic residues was less, and a copper layer with excellent surface flatness could be formed. In particular, in Evaluation Examples 1 and 2, it was found that a copper layer with particularly excellent surface flatness could be formed. In Comparative Evaluation Example 8, although no organic residues were detected, the value of ΔL was large, and a copper layer with excellent surface flatness could not be formed.

[0060] From the above, it was found that when a copper layer is formed on a substrate to be plated by an electrolytic copper plating method using the electrolytic copper plating solution of the present invention, a copper layer with high purity and excellent surface flatness can be formed.

Explanation of Reference Signs

[0061] 1 Copper layer, 2 Substrate to be plated, 3 Minimum height (L Min ), 4 Maximum height (L Max ), 5 ΔL.

Claims

1. (A) Sulfate ion (B) A compound represented by the following general formula (1) (C) Copper ion An electrolytic copper plating solution containing chloride ion, sodium 3,3'-dithiobis(1-propanesulfonate), and polyethylene glycol, wherein the content of the component (B) is 0.3 to 30 parts by mass and the content of the component (C) is 5 to 50 parts by mass with respect to 100 parts by mass of the content of the component (A). 【Chemical 1】 (wherein, R １ represents a hydrogen atom or a sodium atom, R 2 represents a hydrogen atom, and n represents 1 or 2.)

2. Said R １ and R2 are hydrogen atoms, and n is 2, the electrolytic copper plating solution according to claim 1.

3. The electrolytic copper plating solution according to Claim 1 or 2, wherein the component (A) is contained in an amount of 10 g to 500 g per 1 L of the electrolytic copper plating solution.

4. An electrolytic copper plating method comprising using the electrolytic copper plating solution according to any one of Claims 1 to 3.

5. A method for producing an electrolytic copper plating solution, comprising mixing a sulfate ion source, a compound represented by the following general formula (1), a copper ion source, a chloride ion, sodium 3,3'-dithiobis(1-propanesulfonate), polyethylene glycol, and a solvent, wherein in the electrolytic copper plating solution, the content of the compound represented by the general formula (1) is 0.3 to 30 parts by mass and the content of copper ion is 5 to 50 parts by mass with respect to 100 parts by mass of the content of sulfate ion. 【Chemical 2】 (wherein, R １ represents a hydrogen atom or a sodium atom, R2 represents a hydrogen atom, and n represents 1 or 2.)

6. Said R １ The method for producing an electrolytic copper plating solution according to claim 5, wherein R and R2 are hydrogen atoms and n is 2.

7. The method for producing an electrolytic copper plating solution according to Claim 5 or 6, wherein the component (A) is contained in an amount of 10 g to 500 g per 1 L of the electrolytic copper plating solution.

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