KR20220071430A - Electroplating solution of tin-silver alloy for wafer bumps with improved distribution deviation of silver content in plating films - Google Patents

Abstract

Provided is a tin-silver alloy electroplating solution with improved mass productivity by maintaining a silver content variation in a plating film low even under a variety of plating condition changes. The tin-silver alloy electroplating solution is used for plating a wafer bump and comprises tin ions, silver ions, conductive salts, a combination of phenylurea and mercaptotetrazole compounds as silver complexing agents, and carboxylic acids as tissue micronizing agents.

Description

Electroplating solution of tin-silver alloy for wafer bumps with improved distribution deviation of silver content in plating films

The present invention relates to a tin-silver alloy electroplating solution for wafer bumps, and more particularly, to a tin-silver alloy electroplating solution for wafer bumps having improved distribution deviation of silver content in a plating film despite various plating conditions changes. .

A bump is a protrusion-shaped metal terminal for connecting a semiconductor integrated circuit to an external circuit board or an intermediate board circuit. For example, solder (an alloy of lead and tin), lead-free solder (eg, tin, tin alloy) is formed by As a manufacturing method of a bump, a vapor deposition method, electroplating, a paste printing method, a microball method, etc. are known, for example. In recent years, as the number of bumps for connection with external circuits increases along with the integration and high density of semiconductor device circuits, there is a strong demand for narrowing the bump pitch and reducing the size of the bumps. Among the above manufacturing methods, since the paste printing method and the microball method are difficult to apply to small-sized bumps, an electroplating method capable of manufacturing narrow-pitch or small-diameter bumps is attracting attention.

Conventionally, tin electroplating or tin-lead alloy electroplating has been the mainstream as an electroplating method for bumps. However, tin electroplating has a problem in that a whisker occurs, and the use of tin-lead alloy electroplating solution is limited due to environmental pollution caused by lead toxicity. Therefore, recently, a lot of research on tin-silver electroplating solution as a tin alloy material has been conducted.

On the other hand, important in bump electroplating are the uniform bump size and thickness variation, reflow performance, plating speed, and the like. In particular, the plating speed is a very important variable in the actual manufacturing process because it determines the yield of the entire manufacturing process. If the current density is increased to increase the plating speed, there is a problem in that the thickness variation increases due to burnt deposits or non-uniform particle size. Conventionally, to overcome this problem, tissue refiners such as ketones or aldehydes were used in the tin-silver alloy plating solution. Although small and uniform particles could be obtained despite the high plating speed (or current density), the bump shape was not round and distorted. There was a problem with losing. Furthermore, ketones and aldehydes tend to be consumed at a relatively high rate compared to other reactants at high current densities. In order to form a uniform plating film, the concentration of each reactant in the plating solution must be kept constant. However, when the consumption rate is fast, there is a difficulty in frequently analyzing and managing the components of the plating solution.

Also, conventionally, cyanide is mainly used as a silver complexing agent for the stability of silver ions in tin-silver alloy electroplating. However, cyanide compounds are harmful to the human body, and there is a problem that the working environment deteriorates.

As an alternative to these cyanide compounds, the use of phenylurea has been proposed. When phenylurea is used as the silver complexing agent, the effect of maintaining a constant silver ion in the plating solution can be obtained, but there is a lack of securing mass productivity. In general, in the process of mass-producing bump plating, plating conditions such as wafer size, current density, temperature, and flow rate are changed according to the product or necessity. When these plating conditions are changed, the silver content in the plating film tends to decrease or increase. Therefore, in order to secure mass productivity, it is important to keep the change range of the silver content in the plating film low even when the plating conditions change. In other words, the silver content should be maintained within a certain range over the entire area of the plating film. However, in the case of using only phenylurea as a silver complexing agent in tin-silver alloy electroplating, it was found that the silver content in the plating film had a large variation as the plating conditions such as wafer size, current density, temperature, and flow rate were changed, so that it did not reach the mass production level.

Accordingly, the inventors of the present application have completed the present invention after long research and efforts on a tin-silver alloy electroplating solution of a new combination in order to solve these problems.

The problem to be solved by the present invention is that a uniform plating film and a stable bump shape can be obtained even at high current density in wafer bump plating, and silver ions are stably dissolved in the plating solution to keep the concentration of all reactants in the plating solution constant. It is an object of the present invention to provide a tin-silver alloy electroplating solution with improved mass productivity by maintaining the plating solution easily and maintaining a low variation in the silver content in the plating film despite changes in various plating conditions.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. will be.

A tin-silver alloy electroplating solution according to an embodiment of the present invention for achieving the above object is a tin-silver alloy electroplating solution for wafer bump, wherein the electroplating solution includes tin ions, silver ions, conductive salts, and silver complexing agents. Combinations of phenylurea and mercaptotetrazole compounds, and a carboxylic acid as a tissue refining agent may be included.

The weight ratio of the phenylurea and mercaptotetrazole compound constituting the silver complexing agent may be 2:1 to 10:1.

The mercaptotetrazole compound may be 1-(2-diethylaminoethyl)-5-mercapto-1,2,3,4-tetrazole.

In the electroplating solution, only carboxylic acid may be used as the tissue refiner, excluding ketones and aldehydes.

The electroplating solution is 40-120 g/L of tin ions, 0.1-1 g/L of silver ions, 100-300 g/L of conductive salt, 5-30 g/L of phenylurea, 0.5-10 g/L of mercaptotetrazole compound, and carboxylic acid 0.1-5 g/L, surfactant 0.5-6 g/L and antioxidant 0.1-2 g/L.

The variation in the silver content in the tin-silver alloy plating film formed with the electroplating solution may be 0.2 to 0.7%.

Specific details of other embodiments are included in the detailed description and drawings.

As described above, according to the tin-silver alloy electroplating solution for wafer bump plating according to the present invention, a combination of phenylurea and mercaptotetrazole compound is used instead of the conventional cyanide compound as a silver complexing agent, so that it is harmless to the human body and environmentally friendly. Subsequently, the working environment can be improved, secondly, the stability of silver ions in the electroplating solution can be obtained, and thirdly, the silver content deviation in the plating film can be maintained at a low level despite changes in the plating conditions such as wafer size, current density, temperature, and flow rate. Thus, mass productivity and reliability can be secured.

In addition, the present invention is characterized in that only a small amount of carboxylic acid is used as a tissue refining agent, excluding ketones and aldehydes, and polyoxyethylene laurylamine ether or polyoxyethylene stearylamine which is a nonionic surfactant with carboxylic acid A bump with a uniform shape can be obtained by the interaction of ether. It is preferable to use only carboxylic acid alone as the tissue refining agent of the present invention. It was confirmed that the plating properties were remarkably deteriorated when carboxylic acid was mixed with conventional ketones or aldehydes. In addition, unlike ketones or aldehydes, when carboxylic acid is used as a tissue refiner, there is little difference in the consumption ratio with other components, so it is possible to more easily manage the concentration of the plating solution to perform uniform electroplating and to improve productivity. .

According to the tin-silver alloy electroplating solution of the present invention combined in such a special configuration, a good quality plating film and bump can be obtained even at a high current density, for example, 5-15A/dm ² .

1 is a photograph of a bump electroplated according to Example 1 observed with a microscope (200 magnification).
FIG. 2 is a photograph observed with a Focused Ion Beam (FIB) after performing reflow of the bump electroplated according to Example 1. FIG.
3 is an X-ray photograph of a bump electroplated according to Example 1. FIG.
4 is a photograph of a bump electroplated according to Comparative Example 1 observed with a scanning electron microscope (SEM).
5 is a photograph of a cross-section of a bump electroplated according to Comparative Example 1 observed with a microscope (magnification of 200).
6 is a photograph of an X-ray observation of a bump electroplated according to Comparative Example 1. Referring to FIG.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

The tin-silver alloy electroplating solution of the present invention used for wafer bump plating contains a tin ion, a silver ion, a conductive salt, a silver complexing agent, and a texture refining agent. Furthermore, it may further include a nonionic surfactant and an antioxidant.

As the source of tin ions, tin sulfate or tin methanesulfonate may be used. Since tin sulfate is mainly used for low-speed plating, tin methanesulfonate may be preferably used. The concentration of tin ions in the plating solution may be 40-120 g/L. When the concentration of tin ions is less than 40 g/L, the structure of the plating film or the shape of the bumps is not uniform. can occur

Silver methanesulfonate may be used as a source of silver ions. The concentration of silver ions in the plating solution is preferably maintained at 0.1-1 g/L. When the concentration of silver ions is less than 0.1 g/L, whiskers are likely to occur. It is preferable that the silver content in the plating film be maintained within 5%. However, when the concentration of silver ions is greater than 1 g/L, the silver content in the plating film becomes excessively high and the melting temperature increases.

As a conductive salt or electrolyte, methanesulfonic acid may be used in the same manner as metal ions. The concentration of conducting salt may be 100-300 g/L. If the conductive salt concentration is less than 100 g/L, the uniformity of the bump plating film is deteriorated, and if it is greater than 300 g/L, the plating speed decreases.

As the silver complexing agent, a combination of phenylurea and mercaptotetrazole compounds may be used.

Here, the concentration of phenylurea may be 5-30 g/L. When the concentration of phenylurea is less than 5 g/L, it is difficult for silver ions to be stabilized in the plating solution, and when the concentration of phenylurea is greater than 30 g/L, the plating speed is slowed or the plating of the tin-silver alloy cannot be formed. A concentration of the mercaptotetrazole compound may be used in the range of 0.5-10 g/L. When the concentration of the mercaptotetrazole compound is less than 0.5 g/L, it does not affect the distribution of the silver content in the plating film, and when it is greater than 10 g/L, a phenomenon occurs in which the variation in the silver content in the plating film becomes large. Examples of the mercaptotetrazole compound include 1-(2-diethylaminoethyl)-5-mercapto-1,2,3,4-tetrazole, 1-(3-ureidophenyl)-5-mercaptotetra Sol, 1-((3-N-ethyl oxalamido)phenyl)-5-mercaptotetrazole, 1-(4-acetamidophenyl)-5-mercapto-tetrazole, 1-(4-carboxy phenyl)-5-mercaptotetrazole. Preferably, 1-(2-diethylaminoethyl)-5-mercapto-1,2,3,4-tetrazole and the like may be used as the mercaptotetrazole compound.

The combination of phenylurea and mercaptotetrazole compound is harmless to the human body and environment-friendly unlike cyanide compound, so it can improve the working environment, obtain the stability of silver ions in the electroplating solution, and obtain a certain silver content in the plating film. Furthermore, it is possible to uniformly control the silver content over the entire area of the plated film by maintaining the dispersion of the silver content in the plated film at a low level. The weight ratio of phenylurea to mercaptotetrazole compound in the plating solution may be 2:1 to 10:1, preferably 2.5:1 to 7.5:1.

As the tissue refiner, it is preferable to use carboxylic acids except for ketones or aldehydes. Since plating properties deteriorate when ketones or aldehydes and carboxylic acid are mixed and used, more preferably only carboxylic acid can be used as a tissue refiner. At least one selected from the group consisting of acrylic acid, cinnamic acid, methacrylic acid and sorbic acid may be used as the carboxylic acid. Preferably, acrylic acid or methacrylic acid, which is easily soluble among them, may be used. The concentration of the carboxylic acid may be 0.1-5 g/L. When the concentration of the carboxylic acid is smaller than 0.1 g/L or larger than 5 g/L, a phenomenon occurs in which the uniformity of the plating film is deteriorated.

As the surfactant, copolymers of polyoxyethylene and propylene or polyoxyethyleneamines can be used. Preferably, at least one selected from the group consisting of polyoxyethylene laurylamine ether and polyoxyethylene stearylamine ether may be used. The concentration of surfactant may be 0.5-6 g/L.

The antioxidant serves to prevent oxidation of tin to tetravalent, and may be at least one selected from the group consisting of catechol, hydroquinones, and resorcinol. Preferably, hydrothunones may be used. The concentration of antioxidant may be 0.1-2 g/L.

In forming wafer bumps using a tin-silver alloy electroplating solution, after preparing the tin-silver electroplating solution, stir the plating solution, put the object to be plated into the electroplating solution, and then apply a current at a current density of 5-15 A/dm ² It includes the step of applying and plating. Since the electroplating solution of the present invention is configured to obtain an excellent plating film even at high current density, it is preferable that the current density is greater than 5 A/dm ² , and when the current density is less than 5 A/dm ² , the plating particles become large There is a phenomenon in which the bump shape becomes non-uniform, and when the current density is greater than 15 A/dm ² , the plating structure becomes rough and the plating efficiency is deteriorated.

The temperature of the plating solution may be 20-35 °C, preferably 25-30 °C.

Agitation of the plating solution may be maintained at a constant level, for example, a flow rate of 1-4 L/min regardless of the method.

Hereinafter, the configuration of the present invention and its effects will be described in detail through Examples and Comparative Examples. This embodiment is intended to explain the present invention in more detail, and the scope of the present invention is not limited by the present embodiment.

<Example>

Table 1 below shows the components and contents of the tin-silver alloy electroplating solution according to embodiments of the present invention, and plating conditions (current density, temperature, flow rate) applied during electroplating.

Example 1 Example 2 Example 3 Example 4 tin ions 60 g/L 60 g/L 60 g/L 60 g/L silver ion 0.3 g/L 0.3 g/L 0.3 g/L 0.3 g/L conductionitis Methanesulfonic acid 150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L antioxidant Hydroquinone 1 g/L hydroquinone
1 g/L hydroquinone
1 g/L hydroquinone
1 g/L Surfactants polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene lauryl amine ether
5 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L complexing agent Phenylurea
10 g/L Phenylurea
15 g/L Phenylurea
20 g/L Phenylurea
10 g/L diethylaminoethylmercaptotetrazole
2 g/L diethylaminoethylmercaptotetrazole
2 g/L diethylaminoethylmercaptotetrazole
4 g/L diethylaminoethylmercaptotetrazole
4 g/L tissue refiner methacrylic acid
1.5 g/L acrylic acid
0.2 g/L methacrylic acid
2 g/L methacrylic acid
2 g/L current density 11 A/dm ² 14 A/dm ² 12 A/dm ² 15 A/dm ² temperature 25℃ 25℃ 25℃ 25℃ flow rate 2 L/min 2 L/min 2 L/min 2 L/min

The bumps prepared by the usual plating process (degreasing, pickling, plating, neutralization, and drying) were observed using the tin-silver alloy electroplating solution of Examples 1 to 4. 1 is a photograph of a bump electroplated according to Example 1 observed with a microscope (200 magnification), and it was confirmed that the size of the plated particles or the shape of the bump was uniform and there was little variation. 2 is a photograph observed with a FIB (Focused Ion Beam) after performing reflow of the bump electroplated according to Example 1, and FIG. 3 is an X-ray observation of the bump electroplated according to Example 1 It's a photo. As shown in Figs. 2 and 3, there were no voids in the bumps. The bumps according to Examples 2 to 4 also showed substantially the same results.

Table 2 below is for observing variations in the distribution of silver content in the plating film according to changes in current density or temperature for the same electroplating solution. Components and contents of the tin-silver alloy electroplating solution according to embodiments of the present invention, and plating These are examples of conditions. Specifically, in Examples 5 and 6, the current density was changed for the same plating solution while other conditions were maintained the same. Examples 7 to 9 are examples in which the plating solution temperature is changed with respect to the same plating solution while other conditions remain the same.

Example 5 Example 6 Example 7 Example 8 Example 9 tin ions 60 g/L 60 g/L 60 g/L 60 g/L 60 g/L silver ion 0.3 g/L 0.3 g/L 0.3 g/L 0.3 g/L 0.3 g/L conductionitis Methanesulfonic acid 150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L antioxidant Hydroquinone 1 g/L hydroquinone
1 g/L hydroquinone
1 g/L hydroquinone
1 g/L hydroquinone
1 g/L Surfactants polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L complexing agent Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
10 g/L diethylaminoethylmercaptotetrazole
4 g/L diethylaminoethylmercaptotetrazole
4 g/L diethylaminoethylmercaptotetrazole
4 g/L diethylaminoethylmercaptotetrazole
4 g/L diethylaminoethylmercaptotetrazole
4 g/L tissue refiner methacrylic acid
1 g/L methacrylic acid
1 g/L methacrylic acid
1 g/L methacrylic acid
1 g/L methacrylic acid
1 g/L current density 8 A/dm ² 12 A/dm ² 8 A/dm ² 8 A/dm ² 8 A/dm ² temperature 25℃ 25℃ 22℃ 27℃ 32℃ flow rate 2 L/min 2 L/min 2 L/min 2 L/min 2 L/min

Table 3 below is for observing the variation in the distribution of silver content in the plating film according to the change in flow rate for the same electroplating solution. will be. Specifically, Examples 10 to 12 are examples of changing the flow rate by stirring the plating solution while maintaining the same other conditions for the same plating solution.

Example 10 Example 11 Example 12 tin ions 60 g/L 60 g/L 60 g/L silver ion 0.3 g/L 0.3 g/L 0.3 g/L conductionitis Methanesulfonic acid 150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L antioxidant Hydroquinone 1 g/L hydroquinone
1 g/L hydroquinone
1 g/L Surfactants polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L silver complexing agent Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
10 g/L diethylaminoethylmercaptotetrazole
4 g/L diethylaminoethylmercaptotetrazole
4 g/L diethylaminoethylmercaptotetrazole
4 g/L tissue refiner methacrylic acid
1 g/L methacrylic acid
1 g/L methacrylic acid
1 g/L current density 8 A/dm ² 8 A/dm ² 8 A/dm ² temperature 25℃ 25℃ 25℃ flow rate 1 L/min 3 L/min 4 L/min

Table 4 below shows the results of observing the plating film prepared by performing the usual plating process (degreasing, pickling, plating, neutralization, and drying) according to predefined plating conditions using the electroplating solutions of Examples 5 to 12. Here, <Average silver content> represents the average value of the silver content measured by X-rays at five points (5 points) in the plating film, and <Silver content deviation> is the maximum value of the silver content measured at five points in the plating film and It represents the minimum difference.

silver content average Silver content deviation Example 5 2.32% 0.51% Example 6 2.20% 0.44% Example 7 2.01% 0.35% Example 8 2.23% 0.40% Example 9 2.35% 0.52% Example 10 2.11% 0.38% Example 11 2.26% 0.42% Example 12 2.32% 0.50%

As shown in Table 4, in the case of the tin-silver alloy plating solution according to the embodiment of the present invention, the deviation of the silver content in the plating film is maintained at a low level even when the plating conditions (current density, temperature, flow rate) are changed according to the working environment. became Specifically, the average silver content was found to be 2.01-2.35%, and the silver content distribution deviation was confirmed to be 0.38-0.52%. When the tin-silver alloy plating solution according to the embodiment of the present invention is used, the silver content deviation or the silver content distribution deviation in the plating film may be maintained at 0.2 to 0.7%, preferably 0.3 to 0.6%. . When the silver content deviation is kept low within this range, mass productivity of wafer bump plating can be secured.

<Comparative example>

Table 5 below shows the components and contents of the tin-silver alloy electroplating solution used as a comparative example, and plating conditions (current density) applied during electroplating.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 tin ions 60 g/L 60 g/L 60 g/L 60 g/L 60 g/L silver ion 0.2 g/L 0.2 g/L 0.2 g/L 0.2 g/L 0.2 g/L conductionitis Methanesulfonic acid 150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L antioxidant Hydroquinone 1 g/L hydroquinone
1 g/L hydroquinone
1 g/L hydroquinone
1 g/L hydroquinone
1 g/L Surfactants Polyoxyethylene stearylamine ether 3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene lauryl amine ether
5 g/L polyoxyethylene stearylamine ether
3 g/L complexing agent Phenylurea 10 g/L Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
15 g/L Phenylurea
20 g/L tissue refiner benzalacetone
0.2 g/L benzalacetone
0.1 g/L benzalacetone
0.1 g/L Glutaaldehyde 0.05 g/L Glutaaldehyde 0.05 g/L Glutaaldehyde 0.05 g/L methacrylic acid
1 g/L methacrylic acid
2 g/L current density 11 A/dm ² 11 A/dm ² 11 A/dm ² 14 A/dm ² 12 A/dm ²

In Comparative Examples 1 to 5, ketones and/or aldehydes were used as tissue refiners, and in the case of ketones, benzalacetone was used, and in the case of aldehydes, glutaraldehyde was used.

Using the electroplating solutions of Comparative Examples 1 to 5, normal plating processes (degreasing, pickling, plating, neutralization, and drying) were performed to observe the manufactured bumps. 4 is a photograph of the bump electroplated according to Comparative Example 1 observed with a scanning electron microscope (SEM), and the bump shape was oval and showed the result of overgrowth in one direction. 5 is a photograph of a cross-section of the bump electroplated according to Comparative Example 1 observed with a microscope (200 magnification), and FIG. 6 is a photograph of the bump electroplated according to Comparative Example 1 observed with X-rays. As shown in FIGS. 5 and 6 , voids were observed inside the bump. The bumps according to Comparative Examples 2 to 5 also showed substantially the same results.

As in Comparative Examples 1, 2 and 4, when ketones and/or aldehydes were used as tissue refiners, the size of the plating particles was small and the plating surface was uniform. did

In Comparative Examples 3 and 5, a mixture of carboxylic acid and ketones or aldehydes was used as a tissue refiner. It can be seen that even if carboxylic acid is partially added, bump characteristics are deteriorated by the ketones or aldehydes. That is, although the size of the plated particles was small and a uniform plated surface was shown, voids were observed inside the bumps and the shape of the bumps was also observed to be non-uniform.

Table 6 below is to observe the effect of the combination of phenylurea and mercaptotetrazole as a silver complexing agent on the dispersion of silver content in the plating film. Components and contents of the tin-silver alloy electroplating solution used as a comparative example , and the plating conditions. Specifically, Comparative Examples 6 and 7 are examples in which the current density is changed for the same plating solution while other conditions are maintained the same. Comparative Examples 8 to 10 are examples in which the plating solution temperature is changed with respect to the same plating solution while other conditions are maintained the same.

Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 tin ions 60 g/L 60 g/L 60 g/L 60 g/L 60 g/L silver ion 0.3 g/L 0.3 g/L 0.3 g/L 0.3 g/L 0.3 g/L conductionitis Methanesulfonic acid 150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L antioxidant Hydroquinone 1 g/L hydroquinone
1 g/L hydroquinone
1 g/L hydroquinone
1 g/L hydroquinone
1 g/L Surfactants polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L complexing agent Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
10 g/L tissue refiner 1 g/L methacrylic acid methacrylic acid
1 g/L methacrylic acid
1 g/L methacrylic acid
1 g/L methacrylic acid
1 g/L current density 8 A/dm ² 12 A/dm ² 8 A/dm ² 8 A/dm ² 8 A/dm ² temperature 25℃ 25℃ 22℃ 27℃ 32℃ flow rate 2 L/min 2 L/min 2 L/min 2 L/min 2 L/min

Table 7 below is to observe the effect of the combination of phenylurea and mercaptotetrazole as a silver complexing agent on the dispersion of silver content in the plating film, and the components and contents of the tin-silver alloy electroplating solution used as a comparative example , and the plating conditions. Specifically, Comparative Examples 11 to 13 are examples of changing the flow rate by stirring the plating solution while maintaining the same other conditions for the same plating solution.

Comparative Example 11 Comparative Example 12 Comparative Example 13 tin ions 60 g/L 60 g/L 60 g/L silver ion 0.3 g/L 0.3 g/L 0.3 g/L conductionitis Methanesulfonic acid 150 g/L methanesulfonic acid
150 g/L methanesulfonic acid
150 g/L antioxidant Hydroquinone 1 g/L hydroquinone
1 g/L hydroquinone
1 g/L Surfactants polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene stearylamine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L polyoxyethylene lauryl amine ether
3 g/L complexing agent Phenylurea
10 g/L Phenylurea
10 g/L Phenylurea
10 g/L tissue refiner 1 g/L methacrylic acid methacrylic acid
1 g/L methacrylic acid
1 g/L current density 8 A/dm ² 8 A/dm ² 8 A/dm ² temperature 25℃ 25℃ 25℃ flow rate 1 L/min 3 L/min 4 L/min

Table 8 below shows the results of observing the plating film prepared by performing the usual plating process (degreasing, pickling, plating, neutralization, and drying) according to predefined plating conditions using the electroplating solutions of Comparative Examples 6 to 13. Here, <Average silver content> represents the average value of the silver content measured by X-rays at five points (5 points) in the plating film, and <Silver content deviation> is the maximum value of the silver content measured at five points in the plating film and It represents the minimum difference.

silver content average Silver content deviation Comparative Example 6 2.48% 1.25% Comparative Example 7 2.27% 0.89% Comparative Example 8 2.22% 0.84% Comparative Example 9 2.45% 1.23% Comparative Example 10 2.53% 1.33% Comparative Example 11 2.19% 0.85% Comparative Example 12 2.48% 1.19% Comparative Example 13 2.61% 1.42%

As shown in Table 8, in the case of Comparative Example, only phenylurea was used without the mercaptotetrazole compound as the silver complexing agent, but when the plating conditions (current density, temperature, flow rate) were changed, the silver content deviation in the plating film was high. Specifically, the average silver content was confirmed to be 2.19-2.53%, and the silver content distribution deviation was confirmed to be 0.84-1.42%. In the case of the comparative example, since the silver content deviation is too large, it is difficult to apply to mass production of wafer bump plating.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can realize that the present invention can be embodied in other specific forms without changing its technical spirit or essential features. you will be able to understand Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (5)

A tin-silver alloy electroplating solution for wafer bumps, the electroplating solution comprising a tin ion, a silver ion, a conductive salt, a combination of a phenylurea and mercaptotetrazole compound as a silver complexing agent, and a carboxylic acid as a texture refining agent Tin-silver alloy electroplating solution. According to claim 1,
The tin-silver alloy electroplating solution, characterized in that the weight ratio of the phenylurea and mercaptotetrazole compound constituting the silver complexing agent is 2:1 to 10:1. According to claim 1,
The mercaptotetrazole compound is 1-(2-diethylaminoethyl)-5-mercapto-1,2,3,4-tetrazole, characterized in that the tin-silver alloy electroplating solution. According to claim 1,
The electroplating solution is a tin-silver alloy electroplating solution using only carboxylic acids excluding ketones and aldehydes as the tissue refiner. According to claim 1,
The electroplating solution is 40-120 g/L of tin ions, 0.1-1 g/L of silver ions, 100-300 g/L of conductive salt, 5-30 g/L of phenylurea, 0.5-10 g/L of mercaptotetrazole compound, and carboxylic acid A tin-silver alloy electroplating solution comprising 0.1-5 g/L, a surfactant 0.5-6 g/L, and an antioxidant 0.1-2 g/L.

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