A metal electroplating composition and methods of use thereof

Abstract

This invention provides a metal electroplating composition comprising: a sulfur-containing compound, a tin salt, a silver salt, an acidic electrolyte, a surfactant, a brightener, an antioxidant, a pH adjuster, and water. The sulfur-containing compound is a compound of formula (I): wherein R1 is selected from primary, secondary, and tertiary amino groups; R2 is selected from straight-chain alkyl and branched-chain alkyl groups; R3 is selected from straight-chain alkyl and branched-chain alkyl groups; and R4 is selected from hydrogen and alkyl groups. Using the above technical solution, electroplating under high current density conditions can achieve the following technical effects: no pores or defects, low impurities in the plating layer, excellent plating uniformity, dense structure, and low surface roughness. The metal electroplating composition has good plating solution stability and plating uniformity, and can obtain consistently good appearance and film thickness uniformity of the plating film. It has good industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials technology, specifically relating to a tin-silver alloy plating solution for forming a tin-silver alloy coating by electroplating. More specifically, it relates to a tin-silver alloy plating solution suitable for forming solder bumps for semiconductor wafers and printed circuit boards. Background Technology

[0002] With the rapid development of mobile communications, internet e-commerce wireless access systems, Bluetooth systems, and Global Positioning System (GPS) technologies, the demand for lower cost, smaller form factor, higher speed device performance, longer battery life, better heat dissipation, "green" processes, and higher device reliability necessitates the replacement of traditional wire bonding technology with flip-chip bump interconnect technology. At the 130nm technology standard, approximately 30% of logic chips require bump technology, while at the 90nm technology standard, this figure jumps to 60%.

[0003] Solderable plating layers for bumps mainly include Sn, SnAg, and SnPb. Pure tin plating is limited in its widespread use in bumping processes due to tin whisker issues. SnPb alloy plating solutions, containing substances like Pb and F that are harmful to the environment and human health, are attracting increasing attention. Therefore, SnAg plating layers dominate the bumping market. Sn-Ag alloy plating layers possess excellent solderability and corrosion resistance, and also perform well in suppressing tin whiskering. Tin-silver plating additives are primarily developed to complement the bumping process. Currently, the mainstream tin-silver plating solutions used in the market are those from Ishihara and Dow Chemical, with current densities around 3-10 ASD.

[0004] Therefore, in view of the above-mentioned technical problems, it is necessary to provide a tin-silver alloy electroplating solution that can be electroplated under high current density conditions, is free of pores and defects, has low impurities in the plating layer, good plating uniformity, dense structure, small surface roughness, good plating solution stability and plating uniformity, and can obtain a consistently good appearance and uniform thickness of the plating film. Summary of the Invention

[0005] The purpose of this invention is to provide a tin-silver alloy plating solution with high current density and excellent plating solution stability, free from pores and defects, low plating impurities, good plating uniformity, dense structure, small surface roughness, and good appearance and thickness uniformity of the plating film.

[0006] The inventors conducted in-depth research and discovered that if the tin-silver alloy plating solution contains specific sulfur compounds, it can not only be electroplated under high current density conditions, but also has no pores or defects, low impurities in the plating layer, good uniformity, dense structure, small surface roughness, good plating solution stability and uniform plating ability, and can obtain consistently good appearance and uniform thickness of the plating film.

[0007] Specifically, one aspect of the present invention provides a metal electroplating composition comprising: a sulfur-containing compound, a tin salt, a silver salt, an acidic electrolyte, a surfactant, a brightener, an antioxidant, a pH adjuster, and water. The sulfur-containing compound has the structure of formula (I):

[0008]

[0009] R1 is selected from primary amino, secondary amino, and tertiary amino groups;

[0010] R2 is selected from straight-chain alkyl and branched-chain alkyl;

[0011] R3 is selected from straight-chain alkyl and branched-chain alkyl;

[0012] R4 is selected from hydrogen and alkyl groups;

[0013] Preferably, R1 is selected from the following groups:

[0014]

[0015] Preferably, R2 is selected from the following groups:

[0016]

[0017] Preferably, R3 is selected from the following groups:

[0018]

[0019] Preferably, R4 is selected from the following groups:

[0020]

[0021] Preferably, the sulfur-containing compound is

[0022] or

[0023] Preferably, the concentration of the sulfur-containing compound is 0.1 to 12 g / L.

[0024] Preferably, the tin salt is selected from one or more of stannous methanesulfonate, stannous halide, stannous acetate, and stannous sulfate, with stannous methanesulfonate being the most preferred; the mass concentration of tin in the tin salt is 30-110 g / L.

[0025] Preferably, the silver salt is selected from silver methanesulfonate, silver acetate, etc. Silver methanesulfonate is preferred; the mass concentration of silver in the silver salt is 0.1-1.8 g / L.

[0026] Preferably, the acidic electrolyte is one or more of hydrogen chloride, hydrogen sulfide, sulfuric acid, alkyl sulfonic acid, aryl sulfonic acid, or alkanol sulfonic acid. Specific examples of alkyl sulfonic acids include methanesulfonic acid or ethyl sulfonic acid. Specific examples of aryl sulfonic acids include benzenesulfonic acid, phenolsulfonic acid, cresolsulfonic acid, or toluenesulfonic acid. Specific examples of alkanol sulfonic acids include hydroxyethyl sulfonic acid. The acidic electrolyte is preferably methanesulfonic acid. The mass concentration of the acidic electrolyte is 30-200 g / L.

[0027] Preferably, the surfactant is anionic surfactant, cationic surfactant, nonionic surfactant, amphoteric surfactant, or other types of surfactant.

[0028] Anionic surfactants are selected from alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, etc. Cationic surfactants are selected from single trialkylamine salts, dimethyl dialkylamine salts, trimethyl alkylammonium salts, etc. Nonionic surfactants are selected from alkanols, phenols, naphthols, bisphenols, alkylphenols, arylalkylphenols, alkylnaphthols, alkoxyphosphates (salts), sorbitol esters, polyalkylene glycols, aliphatic amides with 1-22 carbon atoms, etc., containing 2-300 moles of ethylene oxide (EO) and / or propylene oxide (PO) condensed together. Amphoteric surfactants are selected from carboxybetaine, imidazoline betaine, aminocarboxylic acids, etc.

[0029] Surfactants can be used alone or in combination of two or more. In this embodiment, the amount of surfactant added to the tin-silver alloy plating solution is generally in the range of 0.01 g / L or more and 25 g / L or less, preferably in the range of 0.1 g / L or more and 18 g / L or less.

[0030] Preferably, the brightening agent is a carbonyl compound such as methacrylic acid or 3-chloroacrylic acid. One or more brightening agents may be selected, with methacrylic acid being preferred. The mass concentration of the brightening agent is 0.003-1.3 g / L.

[0031] Preferably, the antioxidant is ascorbic acid or its salt, pyrogallol, hydroquinone, resorcinol, trihydroxybenzene, catechol, methanesulfonic acid or its salt, catechol sulfonic acid or its salt, hydroquinone sulfonic acid or its salt, etc. One antioxidant can be used alone, or two or more can be used in combination; resorcinol is preferred. In this embodiment, the amount of antioxidant added to the tin-silver alloy plating solution is generally in the range of 0.01 g / L or more and 10 g / L or less, preferably in the range of 0.5 g / L or more and 5 g / L or less.

[0032] Preferably, the pH adjuster is various acids such as hydrochloric acid and sulfuric acid, ammonia, potassium hydroxide, sodium hydroxide, sodium bicarbonate, etc. Furthermore, monocarboxylic acids such as acetic acid and propionic acid, boric acid, phosphoric acid, dicarboxylic acids such as oxalic acid and succinic acid, and hydroxycarboxylic acids such as lactic acid and tartaric acid are also effective as pH adjusters.

[0033] Another aspect of the present invention provides a method of using the metal electroplating composition described above for electroplating printed circuit boards, wafer-level packaging, and integrated circuit wafers or chips, comprising:

[0034] The metal electroplating composition is brought into contact with the substrate to be electroplated, which may be a printed circuit board, a wafer-level package, or an integrated circuit wafer or chip; an electric current is applied to perform electroplating.

[0035] Preferably, the current density is 0.5-25 ASD and the electroplating temperature is 10-50℃.

[0036] Preferably, the current density is 1-18 ASD and the electroplating temperature is 25-40℃.

[0037] Compared with existing technologies, the above technical solution has the following advantages:

[0038] 1. It can achieve technical effects such as high current density electroplating, no pores and defects, low impurities in the plating layer, good plating uniformity, dense structure, and small surface roughness;

[0039] 2. The metal electroplating composition described herein possesses excellent plating solution stability and uniform plating ability, resulting in consistently good film appearance and thickness uniformity. It has significant industrial application value. Detailed Implementation

[0040] The advantages of the present invention will be further illustrated below with reference to specific embodiments.

[0041] The metal plating compositions of Examples 1-16 and Comparative Examples 1-7 were prepared according to the components and contents described in Table 1. All components were mixed uniformly, and the volume of the uniformly mixed plating composition was 1L (diluted to 1L with water), with water as the balance, not shown in the table.

[0042] Among them, compound A1 is

[0043]

[0044] Compound A2 is:

[0045]

[0046] Compound B1 is:

[0047]

[0048] Table 1. Components and their contents in Examples 1-16 and Comparative Examples 1-7

[0049]

[0050]

[0051]

[0052] To further test the properties of the above-mentioned metal electroplating composition, patterned wafer material with a PVD seed layer was electroplated under the corresponding electroplating conditions. The fill rate, porosity, structural compactness and surface roughness of the electroplated wafer slices were observed by SEM. The results are shown in Table 2.

[0053] Table 2 Electroplating conditions and test results for Examples 1-16 and Comparative Examples 1-7

[0054]

[0055]

[0056] Meanwhile, increasing the current density and electroplating temperature can improve electroplating efficiency. If the temperature is too high, the electroplating solution is prone to evaporation and the additive concentration will change. If the temperature is too low, the electroplating efficiency will be reduced.

[0057] Therefore, the metal electroplating composition of the present invention, by selecting sulfur-containing compounds with specific structures, can provide superior electroplating effects: the surface of the electroplated material is smooth, the filler is pore-free and has a dense structure; and the operable window is large, which can meet the actual production needs and has good application prospects.

[0058] In this invention, A = ampere; A / dm 2 = Amperes per square decimeter = ASD; °C = degrees Celsius; ppm = parts per million. Unless otherwise specified, all quantities are percentages by mass.

[0059] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A metal electroplating composition, characterized in that, The electroplating composition includes: a sulfur-containing compound, a tin salt, a silver salt, an acidic electrolyte, a surfactant, a brightener, an antioxidant, a pH adjuster, and water.

2. The metal electroplating composition according to claim 1, characterized in that, The sulfur-containing compound is a compound of formula (I): Wherein, R1 is selected from primary amino, secondary amino, and tertiary amino groups; R2 is selected from straight-chain alkyl and branched alkyl groups; R3 is selected from straight-chain alkyl and branched alkyl groups; and R4 is selected from hydrogen and alkyl groups.

3. The metal electroplating composition according to claim 2, characterized in that, R1 is selected from the following groups:

4. The metal electroplating composition according to claim 2, characterized in that, R2 is selected from the following groups:

5. The metal electroplating composition according to claim 2, characterized in that, R3 is selected from the following groups:

6. The metal electroplating composition according to claim 2, characterized in that, R4 is selected from the following groups:

7. The metal electroplating composition according to claim 2, characterized in that, The sulfur-containing compound is or 8. The metal electroplating composition according to claim 1, characterized in that, The concentration of the sulfur-containing compound is 0.1–12 g / L.

9. The metal electroplating composition according to claim 1, characterized in that, The tin salt is selected from one or more of stannous methanesulfonate, stannous halide, stannous acetate, and stannous sulfate.

10. The metal electroplating composition according to claim 9, characterized in that, The tin salt has a tin concentration of 30-110 g / L.

11. The metal electroplating composition according to claim 1, characterized in that, The silver salt is selected from silver methanesulfonate and silver acetate.

12. The metal electroplating composition according to claim 11, characterized in that, The silver concentration in the silver salt is 0.1-1.8 g / L.

13. The metal electroplating composition according to claim 1, characterized in that, The acidic electrolyte is one or more of hydrogen chloride, hydrogen sulfide, sulfuric acid, alkyl sulfonic acid, aryl sulfonic acid, or alkanol sulfonic acid.

14. The metal plating composition as described in claim 13, characterized in that, The alkyl sulfonic acid is selected from methane sulfonic acid or ethyl sulfonic acid; The aryl sulfonic acid is selected from benzenesulfonic acid, phenolsulfonic acid, cresolsulfonic acid, or toluenesulfonic acid; The alkanol sulfonic acid is selected from hydroxyethyl sulfonic acid.

15. The metal plating composition as described in claim 13, characterized in that, The concentration of the acidic electrolyte is 30-200 g / L.

16. The metal electroplating composition according to claim 1, characterized in that, The surfactant is selected from one or more of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants.

17. The metal plating composition as claimed in claim 16, characterized in that, The anionic surfactant is selected from alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, alkylbenzene sulfonates, and alkylnaphthalene sulfonates; The cationic surfactant is selected from single trialkylamine salts, dimethyl dialkylamine salts, and trimethylalkylammonium salts; the nonionic surfactant is selected from alkanols, phenols, naphthols, and bisphenols with 1 to 20 carbon atoms; alkylphenols and arylalkylphenols with 1 to 25 carbon atoms; alkylnaphthols with 1 to 25 carbon atoms; alkoxyphosphates (salts), sorbitol esters, and polyalkylene glycols with 1 to 25 carbon atoms; and aliphatic amides with 1 to 22 carbon atoms containing condensed 2 to 300 moles of ethylene oxide (EO) and / or propylene oxide (PO). The amphoteric surfactant is selected from carboxybetaine, imidazoline betaine, and aminocarboxylic acid.

18. The metal plating composition as claimed in claim 17, characterized in that, The concentration range of the surfactant is 0.01 g / L to 25 g / L.

19. The metal electroplating composition as claimed in claim 18, characterized in that, The concentration range of the surfactant is 0.1 g / L to 18 g / L.

20. The metal electroplating composition according to claim 1, characterized in that, The brightening agent is selected from one or more carbonyl compounds.

21. The metal electroplating composition according to claim 20, characterized in that, The brightening agent is methacrylic acid or 3-chloroacrylic acid.

22. The metal electroplating composition according to claim 1, characterized in that, The mass concentration of the brightening agent is 0.003-1.3 g / L.

23. The metal electroplating composition according to claim 1, characterized in that, The antioxidant is one or more of ascorbic acid or its salt, pyrogallol, hydroquinone, resorcinol, trihydroxybenzene, catechol, methanesulfonic acid or its salt, catechol sulfonic acid or its salt, and hydroquinone sulfonic acid or its salt.

24. The metal electroplating composition according to claim 1, characterized in that, The concentration range of the antioxidant is 0.01 g / L to 10 g / L.

25. The metal plating composition as claimed in claim 24, characterized in that, The concentration range of the antioxidant is 0.5 g / L to 5 g / L.

26. The metal electroplating composition according to claim 1, characterized in that, The pH adjuster is selected from hydrochloric acid, sulfuric acid, ammonia, potassium hydroxide, sodium hydroxide, sodium bicarbonate, acetic acid, propionic acid, boric acid, phosphoric acid, oxalic acid, succinic acid, lactic acid, and tartaric acid.

27. A method of using the metal plating composition as described in any one of claims 1-26 for plating wafers or chips of printed circuit boards, wafer-level packages, and integrated circuits, characterized in that, include: The metal electroplating composition is brought into contact with the substrate to be electroplated, wherein the substrate may be a printed circuit board, a wafer-level package, or an integrated circuit wafer or chip; Electroplating is performed by applying an electric current.

28. The method of use as described in claim 27, characterized in that, The current density is 0.5-25 ASD, and the electroplating temperature is 10-50℃.

29. The method of use as described in claim 28, characterized in that, The current density is 1-18 ASD, and the electroplating process temperature is 25-40℃.

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