US20120205250A1

US20120205250A1 - Electrolytic copper plating solution composition

Info

Publication number: US20120205250A1
Application number: US13/083,262
Authority: US
Inventors: Hee Jin Lee; Dong Hyun Cho; Ji Eun Jeon
Original assignee: Samsung Electro Mechanics Co Ltd
Current assignee: Samsung Electro Mechanics Co Ltd
Priority date: 2011-02-14
Filing date: 2011-04-08
Publication date: 2012-08-16
Also published as: KR20120092975A; KR101255911B1

Abstract

Disclosed is an electrolytic copper plating solution composition, which includes a copper salt, an acidic solution, and a PEG-PPG-PEG copolymer, and in which the PEG-PPG-PEG copolymer which is a non-ionic surfactant is added, thus decreasing the surface tension of the electrolytic copper plating solution, thereby enhancing plating wettability.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2011-0012941, filed Feb. 14, 2011, entitled “Electrolytic copper plating solution composition,” which is hereby incorporated by reference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field
The present invention relates to an electrolytic copper plating solution composition.
2. Description of the Related Art
Electrolytic plating is a process for applying direct-current to a solution of a meal salt so that metal ions are electrodeposited onto the surface of a target to be plated. Electrolytic plating is performed in such a manner that a target to be plated is connected to a cathode (−) and a metal to be electrodeposited is connected to an anode (+) in a solution containing metal ions, and then voltage is applied thereto, whereby the metal ions of the solution receive electrons from the cathode and thus are reduced into a metal, thus plating the surface of the cathode with the metal. Such electrolytic plating is widely utilized in plating the via holes in printed circuit boards, etc.
Electrolytic plating, in particular electrolytic copper plating using copper as metal ions, is typically employed because less pollution is generated and the plating cost is low. The electrolytic copper plating solution includes a small amount of an organic additive such as a brightener for increasing a plating rate, a leveler for decreasing a plating rate, and a carrier for flattening the plating surface. Such an additive is an important factor that determines the quality of electrolytic plating.
In the electrolytic copper plating, wettability of an electrolytic copper plating solution is regarded as very important in order to prevent the bad plating of a substrate and to achieve optimal plating for fine patterning of a circuit layer. Conventionally, among additives, a carrier incidentally functions to increase wettability, but the effects thereof are limited. Thus, there is a need to develop an additive for exclusively enhancing wettability of an electrolytic copper plating solution that is to finely pattern a circuit.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made bearing in mind the problems encountered in the related art and the present invention is intended to provide an electrolytic copper plating solution composition, which includes a non-ionic surfactant composed of a PEG (polyethylene glycol)-PPG (polypropylene glycol)-PEG copolymer.
An aspect of the present invention provides an electrolytic copper plating solution composition, comprising a copper salt, an acidic solution, and a PEG-PPG-PEG copolymer.
In this aspect, the PEG-PPG-PEG copolymer may have an average molecular weight ranging from 1000 Da to 3000 Da.
In this aspect, the PEG-PPG-PEG copolymer may have a weight ratio of PEG:PPG ranging from 1:1 to 1:9.
In this aspect, the composition may comprise 5˜30 wt % of the copper salt, 65˜90 wt % of the acidic solution, and 0.1˜10 wt % of the PEG-PPG-PEG copolymer.
In this aspect, the copper salt may be copper sulfate, copper nitrate, cupric chloride, copper formate, or a mixture thereof.
In this aspect, the acidic solution may be a sulfuric acid solution, a hydrochloric acid solution, an acetic acid solution or a fluoroboric acid solution.
In this aspect, the composition may further comprise one or more additives selected from the group consisting of a brightener, a leveler and a carrier.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The features and advantages of the present invention will be more clearly understood from the following detailed description and embodiments. Furthermore, descriptions of known techniques, even if they are pertinent to the present invention, are considered unnecessary and may be omitted in so far as they would make the characteristics of the invention unclear.
Furthermore, the terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present invention based on the rule according to which an inventor can appropriately define the concept implied by the term to best describe the method he or she knows for carrying out the invention.
Hereinafter, embodiments of the present invention will be described in detail
According to the present invention, an electrolytic copper plating solution composition comprises a copper salt, an acidic solution, and a PEG-PPG-PEG copolymer. In the present invention, the PEG-PPG-PEG copolymer which is a non-ionic surfactant is used, thus increasing wettability of a plating solution, thereby preventing the bad plating of a substrate. Below, the components of the electrolytic copper plating solution composition according to the present invention are specified.
The copper salt is referred to as a neutral copper compound produced by neutralizing a copper-containing base with an acid, which also produces water. The copper contained in the copper salt is electrodeposited on the surface of a target that is to be plated using electrolysis. Copper is superior in terms of thermal conductivity and electrical conductivity and is easy to grind. Hence, copper is typically used as an electrolytic plating material.
The copper salt may be copper sulfate, copper nitrate, cupric chloride, copper formate or a mixture thereof. As such, particularly useful as the copper salt is copper sulfate. The copper sulfate causes less pollution and exhibits superior flatness, and is also inexpensive.
According to the present invention, the electrolytic copper plating solution composition includes 5˜30 wt % of the copper salt. Particularly, the copper salt is used in an amount of 7˜25 wt %. If the amount of copper salt is less than 5 wt %, the plating thickness becomes thin. In contrast, if the amount thereof exceeds 30 wt %, the amount of the electrolyte is comparatively decreased, and thus plating is not efficiently performed when voltage is applied.
The acidic solution which is an acidic aqueous solution having a pH of 5 or less functions as an electrolyte in the electrolytic plating. The acidic solution increases the electrical conductivity of the electrolytic plating solution and facilitates the dissolution of the cathode and the anode. The acidic solution may be a sulfuric acid solution, a hydrochloric acid solution, an acetic acid solution, or a fluoroboric acid solution. As such, the acid concentration of the acidic solution may range from 0.2 m to 0.8 m in terms of plating efficiency, but the present invention is not limited thereto.
According to the present invention, the electrolytic copper plating solution composition includes 65˜90 wt % of the acidic solution. In particular, the acidic solution is used in an amount of 75˜85 wt %. If the amount of acidic solution is less than 65 wt %, a coarse plating layer having weak adhesion is formed. In contrast, if the amount thereof exceeds 90 wt %, an insoluble film may be formed.
The PEG-PPG-PEG copolymer is a non-ionic surfactant comprising the polar region of PEG and the non-polar region of PPG as represented by Formula I below. Various kinds of PEG-PPG-PEG products depending on the average molecular weight and the ratio of PEG/PPG are currently available. Specific examples thereof include PluronicR L-31, PluronicR L-35, PluronicR L-64 and so on, available from BASF. In the present invention, the PEG-PPG-PEG copolymer may be added to decrease the surface tension of the electrolytic copper plating solution to thus enhance the wettability of the plating solution. In the case where the wettability of the plating solution is enhanced, when the via holes of a substrate are plated, the generation of voids is prevented and good plating is possible.
As such, the average molecular weight of the PEG-PPG-PEG copolymer ranges from 1000 Da to 3000 Da. In the case of a PEG-PPG-PEG copolymer having a molecular weight exceeding 3000 Da, there may be increased concern about breaking the polymer chain when voltage is applied, undesirably decreasing the effect of enhancing wettability. Also, a large amount of bubbles are generated and air gaps may thus be included in the plating layer.
Furthermore, in the PEG-PPG-PEG copolymer, the weight ratio of PEG:PPG falls in the range from 1:1 to 1:9. The plating solution composition is an aqueous solution. Hence, if the weight ratio of PEG:PPG exceeds 1:9, the amount of polar PEG is low, making it difficult to dissolve it in the plating solution composition.
According to the present invention, the electrolytic copper plating solution composition includes 0.1˜10 wt % of the PEG-PPG-PEG copolymer. In particular, the PEG-PPG-PEG copolymer is used in an amount of 0.2˜8 wt %. If the amount of PEG-PPG-PEG copolymer is less than 0.1 wt %, the effect of enhancing wettability becomes insignificant. In contrast, if the amount thereof exceeds 10 wt %, the wettability effect is not enhanced by the addition of the PEG-PPG-PEG copolymer.
According to the present invention, the electrolytic copper plating solution composition may further comprise one or more additives selected from the group consisting of a brightener, a leveler, and a carrier.
The brightener is a sulfur-based organic compound having a molecular weight of 500 g/mole or less and functions as a catalyst that facilitates the transfer of charges in the Cu²⁺→Cu⁺ reduction procedure of plating. The brightener contains one or more sulfur atoms, without typically including a nitrogen atom, and has a molecular weight of about 500 g/mole or less. Examples of such a brightener may include n,n-dimethyl-dithiocarbamic acid-(3-sulfopropyl)ester, 3-mercapto-propylsulfonic acid-(3-sulfopropyl)ester, 3-mercapto-propylsulfonic acid (sodium salt), bis-sulfopropyl disulfide, 3-(benzthiazolyl-s-thio)propyl sulfonic acid (sodium salt), pyridinium propyl sulfobetaine, 1-sodium-3-mercaptopropane-1-sulfonate, a sulfoalkyl sulfide compound, a peroxide oxidation product of dialkyl amino-thioxomethyl-thioalkanesulfonic acid, and mixtures thereof.
The leveler is a nitrogen-based saturated organic compound having a molecular weight of 1000 g/mole or more and is typically adsorbed to the surface of a metal to thus hinder the reduction of metal ions. This shortens the diffusion length of plating ions, and ultimately, the diffusion length is made uniform along the contour of the surface to be plated. Examples of such a leveler may include 1-(2-hydroxyethyl)-2-imidazolidinethione, 4-mercaptopyridine, 2-mercapto thiazoline, ethylene thiourea, thiourea, alkylated polyalkyleneimine, a phenazonium compound, N-heteroaromatic ring containing polymers, polymer amine, polyvinyl carbamate, pyrrolidone, and imidazole.
The carrier is added to flatten the plating surface, and an example thereof typically includes a PEG-based polymer.
A better understanding of the present invention may be obtained via the following examples which are set forth to illustrate, but are not to be construed as limiting the present invention.

Example 1

9.8 wt % of copper sulfate as a copper salt, 90 wt % of a sulfuric acid solution (sulfuric acid concentration: 0.2 M) as an acidic solution, and 0.2 wt % of a non-ionic surfactant comprising a PEG-PPG-PEG copolymer (PluronicR L-31 available from BASF, molecular weight 1100 Da, PEG:PPG weight ratio 1:9, surface tension 47 mN/m) were stirred at 60 l, thus preparing an electrolytic copper plating solution composition.
Using the electrolytic copper plating solution composition, 300 via holes formed in a to substrate were subjected to electrolytic plating under conditions of a reducing current density of 1 A/cm²and a plating time of 70 min in a 1.5 L plating bath. The substrate in which the diameter of the via holes was 100 μm and the depth thereof was 80 μm was used.

Example 2

The present example was carried out in the same manner as in Example 1, with the exception that 9.5 wt % of copper sulfate, 90 wt % of a sulfuric acid solution (sulfuric acid concentration: 0.2 M), and 0.5 wt % of a non-ionic surfactant comprising a PEG-PPG-PEG copolymer were added, thus preparing an electrolytic copper plating solution composition.

Example 3

The present example was carried out in the same manner as in Example 1, with the exception that 8 wt % of copper sulfate, 90 wt % of a sulfuric acid solution (sulfuric acid concentration: 0.2 M), and 2 wt % of a non-ionic surfactant comprising a PEG-PPG-PEG copolymer were added, thus preparing an electrolytic copper plating solution composition.

Comparative Example 1

The present example was carried out in the same manner as in Example 1, with the exception that 10 wt % of copper sulfate and 90 wt % of a sulfuric acid solution (sulfuric acid concentration: 0.2 M) were added without the use of the surfactant, thus preparing an electrolytic copper plating solution composition.

Comparative Example 2

The present example was carried out in the same manner as in Example 1, with the exception that 9.8 wt % of copper sulfate, 90 wt % of a sulfuric acid solution (sulfuric acid concentration: 0.2 M), and 0.2 wt % of a PEG (polyethylene glycol) surfactant were added, thus preparing an electrolytic copper plating solution composition.

Comparative Example 3

The present example was carried out in the same manner as in Example 1, with the exception that 9.5 wt % of copper sulfate, 90 wt % of a sulfuric acid solution (sulfuric acid concentration: 0.2 M), and 0.5 wt % of a PEG surfactant were added, thus preparing an electrolytic copper plating solution composition.

Comparative Example 4

The present example was carried out in the same manner as in Example 1, with the exception that 8 wt % of copper sulfate, 90 wt % of a sulfuric acid solution (sulfuric acid concentration: 0.2 M), and 2 wt % of a PEG surfactant were added, thus preparing an electrolytic copper plating solution composition.

Test Example

The plating state of the via holes plated in the above examples and comparative examples was observed with the naked eye using an optical microscope. Among 300 via holes plated in the examples and comparative examples, the number of via holes having voids that were not plated with copper and a percentage (%) thereof relative to the total number of via holes are given in Table 1 below.

	TABLE 1

	Number of Via Holes having Voids	Percentage (%)

Ex. 1	63	21
Ex. 2	67	22.3
Ex. 3	100	33.3
C. Ex. 1	228	76
C. Ex. 2	98	32.7
C. Ex. 3	113	37.7
C. Ex. 4	145	48.3

As is apparent from Table 1, in the case where the non-ionic surfactant comprising the PEG-PPG-PEG copolymer was added to the electrolytic copper plating solution, the number of via holes having voids was decreased. Thus, the electrolytic copper plating solution composition according to the present invention can prevent the bad plating of a substrate and can be applied to the plating of fine patterns.
As described hereinbefore, the present invention provides an electrolytic copper plating solution composition. According to the present invention, a PEG-PPG-PEG copolymer is added, thereby decreasing the surface tension of the electrolytic copper plating solution, resulting in superior plating wettability.
Also, according to the present invention, the PEG-PPG-PEG copolymer has an average molecular weight ranging from 1000 Da to 3000 Da, and thus the PEG-PPG-PEG copolymer breaks less when voltage is applied to conduct electrolytic plating, and few bubbles are generated in the electrolytic copper plating solution.
Also, according to the present invention, the PEG-PPG-PEG copolymer has a weight ratio of PEG:PPG ranging from 1:1 to 1:9, resulting in high solubility in water.
Although the embodiments of the present invention regarding the electrolytic copper plating solution composition have been disclosed for illustrative purposes, those skilled in the art will appreciate that a variety of different modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, such modifications, additions and substitutions should also be understood as falling within the scope of the present invention.

Claims

1. An electrolytic copper plating solution composition, comprising a copper salt, an acidic solution, and a PEG (polyethylene glycol)-PPG (polypropylene glycol)-PEG copolymer.

2. The composition of claim 1, wherein the PEG-PPG-PEG copolymer has an average molecular weight ranging from 1000 Da to 3000 Da.

3. The composition of claim 1, wherein the PEG-PPG-PEG copolymer has a weight ratio of PEG:PPG ranging from 1:1 to 1:9.

4. The composition of claim 1, comprising 5˜30 wt % of the copper salt, 65˜90 wt % of the acidic solution, and 0.1˜10 wt % of the PEG-PPG-PEG copolymer.

5. The composition of claim 1, wherein the copper salt is copper sulfate, copper nitrate, cupric chloride, copper formate, or a mixture thereof.

6. The composition of claim 1, wherein the acidic solution is a sulfuric acid solution, a hydrochloric acid solution, an acetic acid solution or a fluoroboric acid solution.

7. The composition of claim 1, further comprising one or more additives selected from the group consisting of a brightener, a leveler and a carrier.