Electroplating solution for gold-silver alloy and use thereof

Abstract

Embodiments of the present application provide an electroplating solution for a gold-silver alloy and a use thereof. The electroplating solution comprises a gold ion source, a silver ion source, a first complexing agent, and a second complexing agent, wherein the first complexing agent comprises a hydantoin-based substance, and the second complexing agent comprises an organic sulfonic acid or a salt thereof. By means of a synergistic effect of the two types of complexing agents, the electroplating solution exhibits relatively high stability and can specifically inhibit electrodeposition of silver without affecting deposition of gold, thereby reducing the influence of current density fluctuations on the gold content in an alloy coating. Thus, an alloy coating having a gold content stably maintained within a range of 30-50 wt% can be produced over a relatively wide current density range having an interval width of at least 0.3 ASD.

Description

Electroplating solution for electroplating gold-silver alloy and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202411078976.0, filed on August 6, 2024, and entitled "Electroplating solution for electroplating gold-silver alloy and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of electroplating gold-silver alloy, in particular to an electroplating solution for electroplating gold-silver alloy and application thereof. BACKGROUND

[0003] Gold is often used as an electrical connection material in the field of semiconductors and the like due to its excellent electrical conductivity, thermal conductivity and chemical stability. However, gold is relatively expensive. In order to reduce costs, gold-silver alloy can be used to replace pure gold in some scenarios.

[0004] Due to the greater difference in the redox equilibrium potential of gold ions and silver ions, as the current density increases, the content of gold elements in the alloy plating layer will increase sharply, resulting in that it is difficult to deposit a gold-silver alloy plating layer with stable gold element content in a wide current density range using the existing electroplating solution. SUMMARY

[0005] In view of this, the present application provides an electroplating solution for electroplating gold-silver alloy and application thereof with innovative components to solve the problem that it is difficult to deposit an alloy plating layer with stable gold element content in a wide current density range using the existing gold-silver alloy electroplating solution.

[0006] Specifically, the first aspect of the present application provides an electroplating solution for electroplating gold-silver alloy, the electroplating solution comprising a gold ion source, a silver ion source, a first complexing agent and a second complexing agent, wherein the first complexing agent comprises a hydantoin substance, and the second complexing agent comprises an organic sulfonic acid or a salt thereof.

[0007] In the above-mentioned electroplating solution for electroplating gold-silver alloy, the use of hydantoin as a complexing agent in combination with an organic sulfonic acid or a salt thereof can ensure that the stability of the electroplating solution is high, and can specifically inhibit the electrodeposition of silver without affecting the deposition of gold, thereby greatly reducing the problem of the sharp change in the content of gold elements in the alloy plating layer with the change in current density due to the large difference in the deposition potential of gold ions and silver ions. The electroplating solution can be a cyanide electroplating solution or a cyanide-free electroplating solution.

[0008] In the embodiments of the present application, the hydantoin substances include at least one of hydantoin, 1-methylhydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-bromohydantoin, 5-hydroxyhydantoin, 5-ureidohydantoin, 1-amino hydantoin or its salt, 5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, 1-hydroxymethyl-5,5-dimethylhydantoin, 5-methyl-5-ethylhydantoin, 1,3-dichloro-5-methyl-5-ethylhydantoin.

[0009] In the embodiments of the present application, the organic sulfonic acid includes at least one of methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, pyridine sulfonic acid, sulfamic acid, 3-aminopropane sulfonic acid, methyl sulfanilic acid.

[0010] In the embodiments of the present application, the concentration of the second complexing agent in terms of organic sulfonic acid in the electroplating solution is less than the concentration of the first complexing agent. In this way, the stability of the electroplating solution is better, and the components are less likely to be aggregated and decomposed.

[0011] In the embodiments of the present application, the concentration of the hydantoin substances in the electroplating solution is 10 g / L-150 g / L. In this way, the storage stability of the electroplating solution is better, and the appearance of the alloy plating layer obtained by electroplating is better.

[0012] In the embodiments of the present application, the concentration of the second complexing agent in terms of organic sulfonic acid in the electroplating solution is 1 g / L-50 g / L. In this case, the second complexing agent can cooperate with the first complexing agent to inhibit the deposition of silver with high activity, and the appearance of the alloy plating layer obtained by electroplating is not poor.

[0013] In some embodiments of the present application, the ratio of the concentration of the first complexing agent to the concentration of the second complexing agent in terms of organic sulfonic acid in the electroplating solution is 2-20. In this case, the synergistic effect of the two complexing agents is better, the current density interval corresponding to the gold-silver alloy plating layer with a stable gold element content of 30wt%-50wt% is wider, and the appearance of the plating layer is better.

[0014] In the embodiments of the present application, the gold ion source includes a sulfite salt of gold and / or a thiosulfate salt of gold; and the amount of the gold ion source is such that the concentration of gold ions in the electroplating solution is 1 g / L-20 g / L.

[0015] In the embodiments of the present application, the silver ion source includes at least one of silver nitrate, silver carbonate, silver chloride, silver acetate, and 5,5-dimethylhydantoin silver complex; and the amount of the silver ion source is such that the concentration of silver ions in the electroplating solution is 1 g / L-20 g / L.

[0016] In some embodiments of the present application, the electroplating solution further comprises a buffering agent. The presence of the buffering agent can improve the stability of the electroplating solution and ensure the long-term effectiveness of the electroplating solution.

[0017] In embodiments of the present application, the buffering agent comprises one or more of ethylenediaminetetraacetate, citrate, tartrate, phosphate, borate, and picolinate.

[0018] In embodiments of the present application, the concentration of the buffering agent in the electroplating solution is 10 g / L to 30 g / L. This can ensure that the buffering capacity of the electroplating solution is sufficient, the stability is good, and the appearance of the plated layer is uniform and not too rough.

[0019] In some embodiments of the present application, the electroplating solution further comprises a pH additive; and / or, the pH of the electroplating solution is 9.0 to 11.0. The pH of the electroplating solution is in a suitable strong alkaline range, which can ensure that the complexing ability of the first and second complexing agents is good, the stability of the electroplating solution is high, and the appearance of the alloy plated layer obtained by electroplating is good.

[0020] In some embodiments of the present application, the electroplating solution further comprises a brightener. The brightener can help improve the surface brightness and flatness of the gold-silver alloy plated layer formed using the electroplating solution.

[0021] The second aspect of the embodiments of the present application provides the use of the electroplating solution of the first aspect of the embodiments of the present application in electroplating a gold-silver alloy. The gold-silver alloy plated layer formed by electroplating using the electroplating solution in a wide current density range has a stable and uniform gold content, which can better meet the requirements of practical applications.

[0022] The third aspect of the embodiments of the present application provides an electroplating device, comprising:

[0023] an electroplating tank, wherein the electroplating tank is filled with the electroplating solution of the first aspect of the embodiments of the present application;

[0024] a cathode and an anode arranged in the electroplating tank, wherein the cathode comprises a substrate to be plated, and the substrate to be plated is at least partially immersed in the electroplating solution;

[0025] an electroplating power source, wherein the negative electrode of the electroplating power source is electrically connected to the cathode, and the positive electrode of the electroplating power source is electrically connected to the anode, so as to apply a current to the substrate to be plated when the electroplating power source is turned on.

[0026] When the electroplating device filled with the electroplating solution of the embodiments of the present application is used to electroplate a gold-silver alloy, a gold-silver alloy plated layer with a gold content of 30 wt% to 50 wt% can be formed in a current density range of 0.3 ASD.

[0027] The fourth aspect of the embodiment of the present application provides a method for electroplating a gold-silver alloy, comprising:

[0028] The plating substrate is contacted with the electroplating solution in the first aspect of the embodiment of the present application, and electroplating is performed to form a gold-silver alloy plating layer on the plating substrate.

[0029] In the embodiment of the present application, the temperature of the electroplating is 30-60℃, and the current density of the electroplating is 0.1-2.0 ASD. The electroplating conditions are conducive to ensuring that the stability of the electroplating solution is good during electroplating, and the appearance of the alloy plating layer formed is excellent.

[0030] In the embodiment of the present application, the gold-silver alloy plating layer with a mass percentage of gold element of 30wt%-50wt% can be formed within the current density range of the interval width ≥0.3 ASD during electroplating. Thanks to the electroplating solution containing the specific components described above, the fluctuation of the current density has little effect on the content of gold element in the alloy plating layer formed by electroplating, and the alloy plating layer with stable and uniform content of gold element can be obtained within a wide range of current density.

[0031] The fifth aspect of the embodiment of the present application provides an electroplated part, comprising a substrate and a gold-silver alloy plating layer arranged on the substrate, wherein the gold-silver alloy plating layer is formed by electroplating using the electroplating solution in the first aspect of the embodiment of the present application, or is formed by the method for electroplating a gold-silver alloy in the fourth aspect of the embodiment of the present application.

[0032] The gold-silver alloy plating layer on the electroplated part has stable and uniform content of gold element, and has an excellent appearance, which has a good application prospect, and is particularly suitable for etching silver therein to obtain porous gold. The gold-silver alloy plating layer and the porous gold can both be used as metal bonding materials.

[0033] The sixth aspect of the embodiment of the present application provides a porous gold obtained by etching silver from a gold-silver alloy plating layer, wherein the gold-silver alloy plating layer is formed by electroplating using the electroplating solution in the first aspect of the embodiment of the present application, or is formed by the method for electroplating a gold-silver alloy in the fourth aspect of the embodiment of the present application.

[0034] Since the mass percentage of gold element in the gold-silver alloy plating layer described above is stably within the range of 30wt%-50wt%, the silver therein is relatively easy to remove by etching, and the porous gold obtained after removing the silver has high structural stability, which has a wide application prospect and high quality reliability.

[0035] The embodiment of the present application also provides an electronic device, which comprises the electroplated part in the fifth aspect of the embodiment of the present application, or comprises the porous gold in the sixth aspect of the embodiment of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 shows two chips to be bonded and a structure diagram of the chips after bonding.

[0037] Figure 2 is a structure diagram of an electroplating device according to an embodiment of the present application.

[0038] Figure 3 shows a linear fitting diagram of gold content in alloy plating layer and current density at different current densities on a brass test piece using the electroplating solution of Example 1.

[0039] Figure 4 provides a photograph of a silicon wafer after electroplating at an average current density of 1.0 ASD on a 4-inch silicon wafer using the electroplating solution of Example 1 and gold content at each position of the wafer.

[0040] Figure 5 provides a top view of a gold-silver alloy bump and element analysis results of the bump after electroplating at an average current density of 1.0 ASD on a 6-inch patterned silicon wafer using the electroplating solution of Example 1. DETAILED DESCRIPTION

[0041] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0042] Figure 1 shows two chips to be bonded and a structure diagram of the chips after bonding. Referring to Figure 1, a chip 10a to be bonded includes a substrate 11a and a metal bonding layer 12a disposed on the substrate 11a, and another chip 10b to be bonded includes a substrate 11b and a metal bonding layer 12b disposed on the substrate 11b. Through a hot-pressing process, the metal bonding layer 12a and the metal bonding layer 12b are fused and bonded, and then the chip 10a and the chip 10b are combined. In some embodiments, the metal bonding layer 12a and the metal bonding layer 12b can be specifically a gold-silver alloy plating layer or a porous gold layer, which is relatively inexpensive. The porous gold layer can be formed by removing silver from the gold-silver alloy plating layer.

[0043] Currently, the electroplating solution used for electroplating gold-silver alloy includes cyanide electroplating solution and non-cyanide electroplating solution. Since silver is more active than gold, the redox equilibrium potential difference between gold ions and silver ions is large. When electroplating gold-silver alloy, with the increase of current density, the content of gold element in the alloy plating layer will increase sharply. This phenomenon is particularly serious in non-cyanide electroplating solution than in cyanide electroplating solution, which makes it extremely difficult to deposit gold-silver alloy plating layer with stable gold element content in a wide current density range using non-cyanide electroplating solution or cyanide electroplating solution. The instability of the gold element content in the gold-silver alloy plating layer will lead to large deviation of the performance of the alloy plating layer, affecting the bonding yield, etc. In addition, in the electroplating process in the semiconductor manufacturing process, due to the influence of electric field distribution, the current density at different positions of the substrate to be plated is also different, for example, the current density at the center and edge regions of the wafer, the current density at different opening areas of the photoresist, or the current density at the hole bottom and hole opening of the hole pattern, etc. are quite different, which further leads to large difference in the content of gold element in the gold-silver alloy plating layer formed at different positions of the same substrate. The content of gold element in some areas cannot meet the application requirements (for example, when the content of gold element in the alloy plating layer for forming porous gold is too high, it will be extremely difficult to remove silver). In view of this, the present application starts from the components of the gold-silver alloy electroplating solution, and solves the problem of the sharp change of the content of gold element in the alloy plating layer with the change of current density during electroplating of gold-silver alloy by improving the components of the electroplating solution.

[0044] Specifically, the present application provides an electroplating solution for electroplating gold-silver alloy, which comprises a gold ion source, a silver ion source, a first complexing agent and a second complexing agent, wherein the first complexing agent comprises a hydantoin substance, and the second complexing agent comprises an organic sulfonic acid or a salt thereof.

[0045] In the above-mentioned electroplating solution, by using the combination of the hydantoin substance and the organic sulfonic acid or the salt thereof, the gold ion source and the silver ion source in the electroplating solution can be complexed without deposition, the specific inhibition effect on the electrodeposition of silver with high activity can be achieved without affecting the deposition of gold, the polarization phenomena of the two ions in the electroplating process tend to be consistent, thereby the problems of the sharp change of the content of gold element in the alloy plating layer with the change of current density due to the large difference between the deposition potentials of gold ions and silver ions, and the large difference in the content of gold element in the alloy plating layer in different regions due to the large difference in current density at different positions of the substrate to be plated can be greatly reduced, so that the gold-silver alloy plating layer with stable gold element content can be prepared by electroplating using the electroplating solution.

[0046] In some embodiments of the present application, the above-mentioned electroplating solution can not contain cyanide ions (CN -). That is, the electroplating solution described above is a cyanide-free electroplating solution. When the existing cyanide-free electroplating solution is used to electroplate gold-silver alloy, the content of gold element in the alloy plating layer increases with the increase of current density, which is particularly serious. However, by simultaneously introducing the first complexing agent and the second complexing agent into the cyanide-free electroplating solution for electroplating gold-silver alloy, the gold-silver alloy plating layer with stable gold element content can be deposited within a wide range of current density, and the cyanide-free electroplating solution has high environmental protection. In some other embodiments of the present application, the electroplating solution contains cyanide ions (CN - ). That is, the electroplating solution is a cyanide electroplating solution. By using the cyanide electroplating solution containing the first complexing agent and the second complexing agent to electroplate gold-silver alloy, the problem of large change in the content of gold element in the alloy plating layer with the change of current density can also be solved, and the gold-silver alloy plating layer with stable gold element content can also be deposited within a wide range of current density.

[0047] The hydantoin-based substance can be at least one of substituted or unsubstituted hydantoin or a salt thereof, but is not limited thereto. In embodiments of the present application, the hydantoin-based substance can include at least one of hydantoin, 1-methylhydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-bromohydantoin, 5-hydroxyhydantoin, 5-ureidohydantoin, 1-amino hydantoin or a salt thereof, 5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, 1-hydroxymethyl-5,5-dimethylhydantoin, 5-methyl-5-ethylhydantoin, 1,3-dichloro-5-methyl-5-ethylhydantoin, etc., but is not limited thereto.

[0048] The structural formula of hydantoin is as follows: The structural formula of 1-methylhydantoin is as follows: The structural formula of 5-methylhydantoin is as follows: The structural formula of 5-ethylhydantoin is as follows: The structural formula of 5-bromohydantoin is as follows: The structural formula of 5-hydroxyhydantoin is as follows: The structural formula of 5-ureidohydantoin is as follows: The structural formula of 1-amino hydantoin is as follows: The structural formula of 5,5-dimethylhydantoin is as follows: The structural formula of 1,3-dibromo-5,5-dimethylhydantoin is as follows: The structural formula of 1-hydroxymethyl-5,5-dimethylhydantoin is as follows: The structural formula of 5-methyl-5-ethylhydantoin is as follows: The structural formula of 1,3-dichloro-5-methyl-5-ethylhydantoin is as follows:

[0049] In the embodiments of the present application, the organic sulfonic acid can include at least one of methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, pyridine sulfonic acid, amino sulfonic acid, 3-aminopropane sulfonic acid, methyl sulfonamide acid, etc., but is not limited thereto. Generally, when the pH of the above plating solution is 8 or more, these organic sulfonic acids exist in the system in the form of organic sulfonic acid salts.

[0050] wherein the structural formula of methane sulfonic acid is The chemical formula of ethane sulfonic acid is CH3CH2-S(=O)2OH. The chemical formula of propane sulfonic acid can be CH3CH2CH2-S(=O)2OH. The pyridine sulfonic acid can specifically include 3-pyridine sulfonic acid and / or pyridine-4-sulfonic acid The structural formula of amino sulfonic acid is The structural formula of 3-aminopropane sulfonic acid is The structural formula of methyl sulfonamide acid is

[0051] In the embodiments of the present application, in the above plating solution, the concentration of the second complexing agent in terms of organic sulfonic acid is less than the concentration of the hydantoin substance. Both of the concentrations are in g / L. In this way, the hydantoin substance is used as the main complexing agent, and the above second complexing agent is used as the auxiliary complexing agent, so that the stability of the above plating solution can be ensured to be good.

[0052] In the embodiments of the present application, the concentration of the hydantoin substance in the plating solution can be 10 g / L-150 g / L. The hydantoin substance has a suitable concentration in the plating solution, which can not only ensure that the stability of the plating solution containing the gold ion source and the silver ion source is good and decomposition / sedimentation of the substance is less likely to occur, but also help to ensure that the complexing ability of the hydantoin substance is not too strong to cause poor appearance (such as blackening) of the plated layer, etc. Specifically, the concentration of the hydantoin substance in the plating solution can be, for example, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, or 150 g / L, etc. In some embodiments, the concentration of the hydantoin substance in the plating solution is 50 g / L-150 g / L, further 60 g / L-150 g / L, 50 g / L-100 g / L, or 60 g / L-100 g / L, etc.

[0053] In this embodiment of the application, the concentration of the second complexing agent in the electroplating solution, calculated as organic sulfonic acid, is 1 g / L-50 g / L. That is, when the second complexing agent is organic sulfonic acid, the concentration of organic sulfonic acid is 1 g / L-50 g / L; when the second complexing agent is organic sulfonate, the concentration of the corresponding organic sulfonic acid is 1 g / L-50 g / L. The second complexing agent has a suitable concentration in the electroplating solution, so that it will not be too low or too high, thus failing to cooperate well with the first complexing agent to inhibit the deposition of highly reactive silver. In addition, the second complexing agent can be adsorbed onto the substrate to be plated in an appropriate amount, and its concentration will not be too high, resulting in poor appearance of the plating layer (such as roughness, blackening, etc.). Specifically, the concentration of the second complexing agent, calculated as an organic sulfonic acid, can be, for example, 2 g / L, 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, 22 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, or 50 g / L. In some embodiments, the concentration of the second complexing agent, calculated as an organic sulfonic acid, is 5 g / L-50 g / L, more specifically 5 g / L-40 g / L, or 10 g / L-25 g / L.

[0054] In some embodiments of this application, the concentration ratio of the first complexing agent to the second complexing agent (calculated as organic sulfonic acid) in the electroplating solution is 2-20, specifically 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20. In this case, the synergistic effect of the first and second complexing agents is better, ensuring a wider current density range corresponding to the formation of a gold-silver alloy plating layer with a stable gold content of 30wt%-50wt%, and also ensuring a better appearance of the plating layer (no blackening and excessive roughness). In some embodiments, the above concentration ratio is 2-15, further 2.5-12.

[0055] In this application, the gold ion source can be a gold ion source. In embodiments of this application, the gold ion source may include gold sulfite and / or gold thiosulfate. In some embodiments, the gold ion source is a gold sulfite, for example, at least one selected from sodium gold sulfite, potassium gold sulfite, and ammonium gold sulfite.

[0056] In the embodiments of the present application, the gold ion source is used in an amount such that the concentration of gold ions in the electroplating solution is 1 g / L to 20 g / L. That is, the concentration of the gold ion source, in terms of gold ions, is 1 g / L to 20 g / L. When the concentration of gold ions in the electroplating solution is within this range, it is possible to ensure that there are sufficient gold ions in the electroplating solution, so that the efficiency of gold deposition on the cathode to be plated is not excessively low, and it is also possible to prevent the concentration of gold ions in the electroplating solution from being excessively high, so that the gold source is not wasted due to the carrying out of the plating solution after the electroplating is completed, and the production cost is not increased, etc. Specifically, the concentration of gold ions in the electroplating solution can be 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, or 20 g / L, etc. In some embodiments, the concentration of gold ions in the plating solution is 5 g / L to 15 g / L.

[0057] In the embodiments of the present application, the silver ion source can include at least one of silver nitrate, silver carbonate, silver chloride, silver acetate, and 5,5-dimethylhydantoin silver complex. In the presence of the above-mentioned first complexing agent and second complexing agent, these silver ion sources can stably exist in the water-based electroplating solution without settling. Among them, the 5,5-dimethylhydantoin silver complex has higher stability in the above-mentioned electroplating solution.

[0058] In the embodiments of the present application, the silver ion source is used in an amount such that the concentration of silver ions in the electroplating solution is 1 g / L to 20 g / L. When the concentration of silver ions in the electroplating solution is within this range, it is possible to ensure that there are sufficient silver ions in the electroplating solution to electrodeposit silver, and it is also possible to prevent the waste of the silver ion source, etc. Specifically, the concentration of silver ions in the electroplating solution can be 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, or 20 g / L, etc. In some embodiments, the concentration of gold ions in the plating solution is 5 g / L to 15 g / L.

[0059] In some embodiments of the present application, the above-mentioned electroplating solution further contains a buffering agent. The buffering agent can be used to improve the buffering capacity of the above-mentioned electroplating solution, improve the stability of the gold ion source and the silver ion source in the electroplating solution, and ensure the long-term use effectiveness of the electroplating solution.

[0060] In some embodiments of the present application, the buffering agent can include one or more of ethylenediaminetetraacetate, citrate, tartrate, phosphate, borate, picolinate, etc. The ethylenediaminetetraacetate can be selected from one or more of disodium ethylenediaminetetraacetate, dipotassium ethylenediaminetetraacetate, disodium magnesium ethylenediaminetetraacetate, etc. The citrate can be selected from one or more of sodium citrate, potassium citrate, ammonium citrate, etc. The tartrate can be selected from one or more of sodium tartrate, potassium sodium tartrate, etc. The phosphate can be selected from one or more of monopotassium phosphate (also known as monopotassium phosphate), disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, etc. The borate can be selected from one or more of sodium borate, potassium borate, ammonium borate, etc. The picolinate can be selected from one or more of sodium picolinate, potassium picolinate, etc.

[0061] In some embodiments of the present application, the concentration of the buffering agent in the electroplating solution described above can be 10 g / L to 30 g / L. A suitable concentration of the buffering agent can ensure that the electroplating solution has sufficient buffering capacity, good stability, and avoid the formation of a plated layer that is uneven in appearance, too rough, etc. Specifically, the concentration of the buffering agent can be 10 g / L, 12 g / L, 13 g / L, 15 g / L, 18 g / L, 20 g / L, 22 g / L, 25 g / L, 28 g / L, or 29 g / L, etc.

[0062] In some embodiments of the present application, the electroplating solution described above can further include a pH additive. The pH additive can be a base and / or an acid. Exemplarily, the base can be selected from at least one of potassium hydroxide, sodium hydroxide, ammonia, etc. The acid can be selected from one or more of sulfurous acid, sulfuric acid, hydrochloric acid, etc. In some embodiments, the pH additive is at least one of potassium hydroxide, sodium hydroxide, ammonia, etc.

[0063] To ensure that the first complexing agent and the second complexing agent have good complexing ability and that the electroplating solution has long-term stability, the pH of the electroplating solution described above is alkaline. In some embodiments of the present application, the pH of the electroplating solution described above can be 9.0 to 11.0. If the pH of the electroplating solution described above is not more than 11.0, the complexing ability of the two complexing agents in the electroplating solution described above can be avoided from being too strong, which can result in a poor appearance of the plated layer (e.g., blackening, roughness, etc.). Specifically, the pH of the electroplating solution described above can be, for example, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.10, 10.9, or 11.0, etc.

[0064] In some embodiments of the present application, the electroplating solution further comprises a brightener. The brightener helps to improve the surface brightness and flatness of the gold-silver alloy plating layer formed by using the electroplating solution, thereby avoiding poor bonding (e.g., voids, resulting in a large contact resistance) of the alloy plating layer formed by using the electroplating solution. The brightener can be at least one selected from polyethylene polyamine, polyethylene imine and derivatives thereof, bipyridine and derivatives thereof, o-phenanthroline, and the like.

[0065] In the present application, the electroplating solution is an aqueous solution. It can be understood that the plating solution further contains water as a solvent.

[0066] In the present application, the electroplating solution can be prepared by completely dissolving the above-mentioned raw materials in water. The raw materials can be added in solid form or in the form of a corresponding aqueous solution. Generally, the gold ion source can be added in the form of an aqueous solution, but the actual amount is calculated based on the gold element; the silver ion source can be added in the form of an aqueous solution, but the actual amount is calculated based on the silver element. The second complexing agent raw material (e.g., organic sulfonic acid) exists in the form of an organic sulfonate salt in the electroplating solution after the pH of the plating solution system is adjusted to be alkaline. The buffer raw material can be the buffer itself or its corresponding acid. Taking the borate as an example, it can be added in the form of boric acid, and exists in the form of a borate salt in the electroplating solution after the pH of the plating solution system is adjusted to be alkaline.

[0067] In addition, the order of adding the raw materials in the preparation of the electroplating solution is not limited. In some embodiments of the present application, the preparation method of the electroplating solution comprises: mixing the gold ion source, the silver ion source, the first complexing agent raw material, the second complexing agent raw material, and the optional buffer raw material and the brightener (if any) in water, adjusting the pH of the mixed solution to a predetermined pH using a pH adjuster, adjusting the volume of the mixed solution to a predetermined volume, obtaining the electroplating solution, and meeting the requirements for the concentrations of the components. When the pH of the obtained plating solution is 9.0-11.0, the second complexing agent raw material added exists in the form of an organic sulfonate salt in the electroplating solution.

[0068] The present application also provides the use of the above-mentioned electroplating solution of the present application in electroplating gold-silver alloy. The electroplated gold-silver alloy can be used for filling of holes and trenches on a substrate, fabrication of rewiring layers, and the like. Specifically, the electroplated gold-silver alloy can be used to prepare an electroplated part with a gold-silver alloy plating layer, and is particularly suitable for use in the manufacturing process of semiconductor devices.

[0069] In some embodiments, the gold-silver alloy plating can replace the gold bumps in existing semiconductor electroplated parts with gold bumps to reduce the cost of bonding materials and the interconnection cost between the semiconductor electroplated parts to be bonded (such as interconnection between chips, interconnection between chips and substrates, etc.). In other embodiments, the gold-silver alloy plating can serve as relay contacts, ensuring electrical contact and enhancing wear resistance. Furthermore, the aforementioned gold-silver alloy plating can be transformed into porous gold after a dealloying process (specifically, removing the silver), which can also be used as a metal bonding / interconnection material. This porous gold maintains a bump-like structure, but its interior is a loose, porous structure.

[0070] Electroplating with the electroplating solution provided in the embodiments of this application can form a gold-silver alloy coating with stable and uniform gold content, without the need for special modifications to the specific electroplating process (such as pulse electroplating with periodic switching of different current densities).

[0071] This application also provides a method for electroplating gold and silver alloys, including:

[0072] The substrate to be plated is brought into contact with the electroplating solution described in the embodiments of this application, and electroplating is performed to form a gold-silver alloy coating on the substrate to be plated.

[0073] Specifically, "bringing the substrate to be plated into contact with the electroplating solution" can mean immersing part or all of the substrate in the plating solution to bring it into contact with the electroplating solution. The substrate to be plated can be a semiconductor substrate as described below in this application, such as a silicon wafer, a germanium substrate, a compound semiconductor substrate, etc.; the substrate may or may not have a complex pattern structure.

[0074] Specifically, during electroplating, the substrate to be plated is typically used as the cathode, which can be partially or entirely placed in an electroplating tank containing the aforementioned electroplating solution. An anode can be placed in this electroplating tank. The anode can be, for example, a platinum-titanium plate. The cathode and anode can be electrically connected to the electroplating power source via wiring. Using the aforementioned electroplating solution as the electrolyte, the cathode and anode together form a conductive circuit (see Figure 2), thereby achieving the deposition of a gold-silver alloy on the substrate.

[0075] To better understand the electroplating process described above, this application also provides an electroplating apparatus. Referring to Figure 2, the electroplating apparatus 200 includes:

[0076] Electroplating tank 20, which contains the electroplating solution 21 described in the embodiments of this application;

[0077] A cathode 22 and an anode 23 are disposed in an electroplating tank 20. The cathode 22 includes a substrate to be plated that is at least partially immersed in the electroplating solution 21.

[0078] The electroplating power supply 24 has its negative pole electrically connected to the cathode 22 and its positive pole electrically connected to the anode 23, so as to apply current to the substrate to be plated when the electroplating power supply 24 is turned on.

[0079] The cathode 22 and the anode 23 are generally oppositely arranged and are generally separated from each other, for example, by the diaphragm 25. In addition, although the cathode 22 and the anode 23 are vertically arranged in the electroplating tank 20 in FIG. 2, it can be understood that the cathode 22 and the anode 23 can also be horizontally arranged in the electroplating tank 20 according to specific needs.

[0080] During electroplating, the cathode 22 is generally applied with an electric potential, so that current is also applied to the substrate to be plated when the electroplating power supply 24 is turned on. During electroplating, gold ions and silver ions in the electroplating solution are reduced at the cathode 22, so as to form a gold-silver alloy on the substrate to be plated. After a gold-silver alloy plating layer with a predetermined gold-silver deposition amount is obtained, the electroplating is ended.

[0081] The current applied during electroplating can be direct current, pulse current or other suitable current. In some embodiments of the present application, the applied current is direct current. Compared with pulse current, the adsorption of additives (such as complexing agents, brighteners, etc.) contained in the electroplating solution for regulating the properties of the plating layer on the electrochemical interface changes little when direct current is used for electroplating, and it is easier to obtain a plating layer with easily controllable hardness and roughness.

[0082] In embodiments of the present application, the temperature of the electroplating is 30-60°C, for example, specifically 30°C, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, 50°C, 55°C, 58°C or 60°C, etc. A suitable electroplating temperature can ensure a high plating solution precipitation efficiency, avoid uneven appearance of the plating layer, and also ensure high stability of the overall plating solution, so that the plating solution management is not difficult due to too fast volatilization of the plating solution.

[0083] In embodiments of the present application, the current density of the electroplating is in the range of 0.1-2.0 ASD (i.e. A / dm 2 ). When the current density exceeds the above range, decomposition of the components of the plating solution or abnormal appearance of the plating layer may occur.

[0084] In the embodiments of the present application, the gold-silver alloy plating layer with gold element content of 30wt%-50wt% can be formed by electroplating in a current density range with a range width of ≥0.3ASD. Even if direct current is used for electroplating, as described above, the current density at different positions of the substrate to be plated is different due to the influence of electric field distribution. For example, if the wafer is electroplated under the condition of an average current density of 1.0ASD, the difference in current density between the center and the edge of the wafer is generally greater than or equal to 0.3ASD. When the above electroplating solution of the present application is used for electroplating, a current density range with a range width of ≥0.3ASD can be found, and the gold-silver alloy plating layer with gold element content in the range of 30wt%-50wt% can be formed by electroplating in such a current density range. In this way, the problem of being difficult to obtain a gold-silver alloy plating layer with stable gold element content in a relatively wide current density operating range is solved. The gold element content in the gold-silver alloy plating layer is in the range of 30wt%-50wt%, which can ensure that the silver in the alloy plating layer is easily etched and removed, and the porous gold formed after etching the silver can maintain good structural stability.

[0085] In the embodiments of the present application, the gold element mass percentage content in any region of the formed gold-silver alloy plating layer is in the range of 30wt%-50wt%. The gold element content in any region of the alloy plating layer is not affected by the distribution position and is in the range of 30wt%-50wt%, which can ensure the consistency of the structural properties and performance of the overall plating layer (such as high consistency of density, wear resistance, hardness, etc.). In addition, it can also avoid the problem that when the gold element content in the alloy plating layer is too high, the silver is more severely wrapped, which leads to the difficulty in completely removing the silver during subsequent alloy removal treatment to obtain a porous gold structure with good stability; if the gold element content in the alloy plating layer is too low, it will lead to poor structural stability of the alloy plating layer after alloy removal treatment.

[0086] In some embodiments of the present application, after the electroplating, the gold-silver alloy plating layer formed can be subjected to annealing treatment to improve the hardness of the gold-silver alloy plating layer and the uniformity of atomic mixing in the gold-silver alloy plating layer.

[0087] The embodiments of the present application also provide an electroplated part, which comprises a substrate and a gold-silver alloy plating layer arranged on the substrate, and the gold-silver alloy plating layer is formed by electroplating using the above-mentioned electroplating solution of the embodiments of the present application or by using the above-mentioned method for electroplating gold-silver alloy of the embodiments of the present application.

[0088] The substrate can include, but is not limited to, a semiconductor substrate, a printed circuit board, etc. In some embodiments, the substrate can be a semiconductor substrate, such as a silicon wafer, a germanium substrate, a compound semiconductor substrate, etc. The semiconductor substrate can or can not have a complex device pattern structure. The semiconductor plating piece including the semiconductor substrate and the gold-silver alloy plating layer can be a liquid crystal display, an image sensor, a memory, a microprocessor, or a microwave radio frequency chip, etc. In some embodiments of the present application, the substrate is a silicon wafer.

[0089] As described above, the mass percentage of gold in any region of the gold-silver alloy plating layer on the plating piece is in the range of 30wt%-50wt%. Due to the plating solution containing the specific components, the fluctuation of current density has little effect on the content of gold in the plating layer, and a gold-silver alloy plating layer with stable and uniform gold content can be obtained in a wide range of current density.

[0090] In some embodiments of the present application, the difference between the mass percentage of gold in any two regions of the gold-silver alloy plating layer is less than or equal to 20%. In this case, the equivalent area of the surface of the substrate provided with the gold-silver alloy plating layer is preferably the area of a circle with a diameter of less than or equal to 12 inches. The substrate can be circular or of other shapes. The use of the above-mentioned plating solution provided by the embodiments of the present application can significantly reduce the difference in the content of gold in the gold-silver alloy plating layer in different regions of the substrate. For example, the difference between the mass percentage of gold in the gold-silver alloy plating layer on the center and the edge of a silicon wafer with a diameter of less than or equal to 12 inches is less than or equal to 20% in the equivalent surface area. It should be noted that if the substrate is not circular, etc., the surface area thereof can be equivalent to the area of a circle (the diameter of the circle is less than or equal to 12 inches), and the difference between the mass percentage of gold in any two regions of the gold-silver alloy plating layer formed on such a substrate is still less than or equal to 20%.

[0091] In the present application, the thickness, hardness, surface roughness, etc. of the gold-silver alloy plating layer formed are not limited.

[0092] The embodiments of the present application also provide a porous gold obtained by etching the silver from the gold-silver alloy plating layer prepared by the above-mentioned method.

[0093] In some embodiments of the present application, nitric acid can be used to soak the gold-silver alloy plating layer to etch away the silver in the alloy plating layer. The obtained porous gold can have a loose porous structure, and the porous gold can also be referred to as porous gold sponge, which has a nanoscale pore size.

[0094] The porous gold can also be used as a metal bonding material, and has good compressibility in addition to good electrical conductivity. The gold content in the gold-silver alloy coating formed as described above is stable and uniform, and the gold content is in the range of 30wt%-50wt%. The silver is easily etched and removed, and the structure of the porous gold obtained after the silver is removed has high stability and is not prone to structural collapse during hot pressing. In addition to being used as a metal bonding material, the porous gold can also be used as a filter material, a catalytic material, a sensing material, or a biological agent, etc.

[0095] The application also provides an electronic device comprising the above-mentioned electroplated part or the above-mentioned porous gold.

[0096] In the application, the electronic device can be a mobile phone, a tablet computer, a notebook computer, a wearable device (such as a smart watch or a smart bracelet), a television, a camera, a video recorder, a camcorder, a household smart device, a vehicle-mounted device, or the like. The electronic device can also be various wired or wireless communication devices such as an antenna, a radar, a router, a gateway, a walkie-talkie, a switch, a lightning arrester, or the like. The electronic device can also be a communication base station. The above-mentioned electroplated part or the above-mentioned porous gold can be connected to the circuit board of the terminal product, the communication device, or the communication base station.

[0097] The application will be further described in the following embodiments.

[0098] Embodiment 1

[0099] An electroplating solution for electroplating a gold-silver alloy includes: adding a gold source in the form of sodium sulfite, a silver source in the form of a 5,5-dimethylhydantoin silver complex, a first complexing agent raw material (specifically, 5,5-dimethylhydantoin), a second complexing agent raw material (specifically, sulfamic acid), and a buffer raw material (specifically, boric acid) into a 2L beaker containing deionized water, adjusting the pH of the obtained mixed solution to 10 using sodium hydroxide, stirring to fully dissolve the raw materials, and adjusting the volume of the mixed solution to a predetermined volume to obtain the required electroplating solution. In the electroplating solution, the concentration of gold ions is 8g / L, the concentration of silver ions is 8g / L, the concentration of 5,5-dimethylhydantoin is 80g / L, the concentration of sulfamate (calculated as sulfamic acid) is 15g / L, and the concentration of borate is 15g / L.

[0100] An electroplating experiment was performed using the above-mentioned electroplating solution: the above-mentioned electroplating solution of embodiment 1 was heated to 40°C and placed in an electroplating tank, the temperature of the electroplating solution in the electroplating tank was controlled to remain at 40°C, a titanium plate was used as an anode, the surface area of the titanium plate was 9cm 2A rectangular brass coupon is used as cathode, four suitable current density values are selected in the range of 0.4-1.2 ASD current density to conduct electroplating experiments, 0.6 ASD, 0.8 ASD, 1.0 ASD and 1.2 ASD are selected in this embodiment. Assuming the plating efficiency is 100%, the plating time required to form an alloy coating with a thickness of 10 μm under different current densities is calculated and electroplating is conducted for the time. After electroplating, the mass percentage of gold and silver in each alloy coating is measured by X-ray fluorescence spectrometer. The gold content in the alloy coating under different current densities is linearly fitted with the current density, and the slope is calculated as a parameter for evaluating the plating effect. If a coating with a gold content of 30-50 wt% needs to be prepared in a current density range of at least 0.3 ASD, the slope value of gold content vs. current density in the alloy coating should be less than 66 according to 20 wt% / 0.3 ASD.

[0101] Figure 3 shows a linear fitting graph of the gold content in the alloy coating formed on the brass coupon at different current densities using the electroplating solution of Example 1. From the fitting relationship in Figure 3, it can be known that the slope of the gold content vs. current density in the alloy coating in Example 1 is 58, which satisfies less than 66. From the fitting relationship in Figure 3, it can be calculated that the electroplating solution of this embodiment 1 can be used to prepare an alloy coating with a gold content of 30-50 wt% in a current density range of 0.81-1.16 ASD, and the current density range is 0.35 ASD, which is greater than 0.3 ASD.

[0102] Example 2

[0103] An electroplating solution differs from Example 1 in that the second complexing agent raw material is replaced by 3-pyridine sulfonic acid, and the second complexing agent in the final electroplating solution is 3-pyridine sulfonate with a concentration of 10 g / L calculated as 3-pyridine sulfonic acid.

[0104] According to the method described in Example 1, the electroplating solution of Example 2 is used to conduct electroplating experiments at several different current density values, and the gold content in the alloy coating formed under different current densities (see Table 1 below) is linearly fitted with the current density, and the slope is calculated as 54.

[0105] Example 3

[0106] An electroplating solution differs from Example 1 in that the second complexing agent raw material is replaced by methane sulfonic acid, and the second complexing agent in the final electroplating solution is methane sulfonate with a concentration of 15 g / L calculated as methane sulfonic acid.

[0107] According to the method described in Example 1, the electroplating solution of Example 3 was used to carry out electroplating experiments at several different current density values, and the gold content in the alloy plating layer formed at different current densities (see Table 1 below) was linearly fitted with the current density, and the slope was calculated to be 62.

[0108] Example 4

[0109] An electroplating solution, which differs from Example 1 in that the second complexing agent raw material is replaced by 3-aminopropane sulfonic acid, and the second complexing agent in the final electroplating solution is 3-aminopropane sulfonate with a concentration of 10 g / L in terms of 3-aminopropane sulfonic acid.

[0110] According to the method described in Example 1, the electroplating solution of Example 4 was used to carry out electroplating experiments at several different current density values, and the gold content in the alloy plating layer formed at different current densities (see Table 1 below) was linearly fitted with the current density, and the slope was calculated to be 61.

[0111] Example 5

[0112] An electroplating solution, which differs from Example 1 only in that the amount of aminosulfonic acid used is changed when preparing the electroplating solution, so that the concentration of aminosulfonate in the final electroplating solution is 25 g / L in terms of aminosulfonic acid.

[0113] According to the method described in Example 1, the electroplating solution of Example 5 was used to carry out electroplating experiments at several different current density values, and the gold content in the alloy plating layer formed at different current densities (see Table 1 below) was linearly fitted with the current density, and the slope was calculated to be 35.

[0114] Example 6

[0115] An electroplating solution, which differs from Example 5 only in that the concentration of the first complexing agent (5,5-dimethylhydantoin) in the electroplating solution is 60 g / L, and the concentration of the second complexing agent (aminosulfonate) is 5 g / L in terms of the corresponding organic sulfonic acid, and the concentration ratio of the two is 12.

[0116] Example 7

[0117] An electroplating solution, which differs from Example 5 only in that the concentration of the first complexing agent (5,5-dimethylhydantoin) in the electroplating solution is 140 g / L, and the concentration of the second complexing agent (aminosulfonate) is 40 g / L in terms of the corresponding organic sulfonic acid, and the concentration ratio of the two is 3.5.

[0118] Example 8

[0119] A plating solution, which is different from that of Example 5 only in that the concentration of the first complexing agent (5,5-dimethylhydantoin) in the plating solution is 100 g / L, and the concentration of the second complexing agent (aminosulfonate) is 40 g / L in terms of the corresponding organic sulfonic acid, and the concentration ratio of the two is 2.5.

[0120] Example 9

[0121] A plating solution, which is different from that of Example 5 only in that the concentration of the second complexing agent (aminosulfonate) is 50 g / L in terms of the corresponding organic sulfonic acid, and the concentration ratio of the two is 1.6.

[0122] Example 10

[0123] A plating solution, which is different from that of Example 5 only in that the concentration of the first complexing agent (5,5-dimethylhydantoin) is 140 g / L, and the concentration of the second complexing agent (aminosulfonate) is 5 g / L in terms of the corresponding organic sulfonic acid, and the concentration ratio of the two is 28.

[0124] Example 11

[0125] A plating solution, which is different from that of Example 5 only in that the first complexing agent is changed to hydantoin, and the concentration of hydantoin in the plating solution is 80 g / L. The concentration of aminosulfonate is still 25 g / L in terms of aminosulfonic acid.

[0126] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0127] Comparative Example 1

[0128] A plating solution, which is different from that of Example 1 only in that no second complexing agent raw material is added when preparing the plating solution, and the plating solution of Comparative Example 1 does not contain the second complexing agent accordingly, and the concentrations of other components are the same as those of Example 1.

[0129] According to the method described in Example 1, the plating solution of Comparative Example 1 is subjected to plating experiments at several different current density values, respectively, and the gold element content (see Table 1 below) in the alloy plating layer formed at different current densities is linearly fitted with the current density, and the slope is calculated to be 86.

[0130] Comparative Example 2

[0131] A plating solution, which is different from that of Example 1 only in that the second complexing agent raw material is replaced by hydroxyethylidene diphosphonic acid, which exists in the plating solution in the form of hydroxyethylidene diphosphonate, and the concentration of the hydroxyethylidene diphosphonate is 10 g / L in terms of hydroxyethylidene diphosphonic acid.

[0132] The plating solution of Comparative Example 2 was plated at several different current density values according to the method described in Example 1, and the gold content in the alloy plating layer formed at different current densities (see Table 1 below) was linearly fitted with the current density, and the slope was calculated to be 82.

[0133] Comparative Example 3

[0134] A plating solution, which differs from Example 1 only in that the second complexing agent raw material is replaced by disodium ethylenediaminetetraacetate, which has a concentration of 30 g / L in the electrolyte.

[0135] The plating solution of Comparative Example 3 was plated at several different current density values according to the method described in Example 1, and the gold content in the alloy plating layer formed at different current densities (see Table 1 below) was linearly fitted with the current density, and the slope was calculated to be 116.

[0136] Comparative Example 4

[0137] A plating solution, which differs from Example 1 only in that the second complexing agent raw material is replaced by thymine, which has a concentration of 10 g / L in the plating solution.

[0138] The plating solution of Comparative Example 4 was plated at several different current density values according to the method described in Example 1, and the gold content in the alloy plating layer formed at different current densities (see Table 1 below) was linearly fitted with the current density, and the slope was calculated to be 107.

[0139] Comparative Example 5

[0140] A plating solution, which differs from Example 1 only in that the plating solution of Comparative Example 5 does not contain a hydantoin complexing agent, and the concentrations of the other components are the same as in Example 1.

[0141] The plating solution of Comparative Example 5 became turbid after 1 hour of preparation, and could not be used to continue the plating experiment according to the method of Example 1.

[0142] The test results of the plating of gold-silver alloy on brass test pieces using the plating solutions of the examples or comparative examples, and the slope of the straight line fitting the gold content in the alloy plating layer with the current density used for plating, are summarized in Table 1 below.

[0143] Table 1

[0144] From the comparison between Comparative Example 5 and Example 1, it can be seen that when the plating solution does not contain a hydantoin substance as a complexing agent, the stability of the plating solution is poor, and the plating solution will quickly decompose due to the photosensitivity of silver ions, resulting in turbidity of the plating solution.

[0145] From the comparison of Example 1 and Comparative Example 1 in Table 1, it can be seen that when the electroplating solution contains a hydantoin complexing agent, the introduction of an organic sulfonate as a complexing agent can effectively maintain the stability of the gold content in the alloy plating layer formed by electroplating, a wider current density range with a width of more than 0.3 ASD can be found, and an alloy plating layer with a gold content in the range of 30-50 wt% can be prepared in the wider current density range. From the comparison of Example 1 and Comparative Examples 2-4, it can be seen that the use of common electroplating complexing agents (hydroxyethylidene diphosphonic acid or disodium ethylenediaminetetraacetate) or thymine which has a certain complexing effect on silver instead of the organic sulfonic acid used in the present application cannot achieve the preparation of an alloy plating layer with a gold content stably in the range of 30-50 wt% in a wider current density range.

[0146] Examples 2-4 compared with Example 1 mainly change the type of the second complexing agent, and similar results as in Example 1 can still be obtained: an alloy plating layer with a gold content stably in the range of 30-50 wt% can be prepared in a wider current density range.

[0147] In addition, the comparison of Example 1 and Example 5 can show that when the types of the second complexing agents in the electroplating solutions are the same (both are organic sulfonates) but the contents are different, the electroplating solution of Example 5 exhibits better electroplating effect, the slope of the plating layer gold content vs. current density is 35, and according to the slope, the interval width of the current density range corresponding to the alloy plating layer with an Au content of 30-50 wt% can be calculated as 0.57 ASD, which is sufficient to cope with the influence of current density non-uniformity caused by electric field distribution during wafer electroplating.

[0148] In addition, from the comparison between Examples 9, 10 and Examples 5, 6, 7, 8, it can be seen that when the mass concentration of the first complexing agent in the electroplating solution and the concentration ratio of the second complexing agent in terms of organic sulfonic acid are greater than 2 and less than 28 (for example, in the range of 2-20), the slope of the gold content in the alloy plating layer formed by the electroplating solution at different current densities is smaller, and accordingly, the interval width of the electroplating current density range corresponding to the alloy plating layer with an Au content in the range of 30-50 wt% is also wider, which is more convenient for increasing the electroplating process window.

[0149] To prove that the electroplating solution provided in the examples of the present application can achieve good electroplating effect on the actual substrate to be plated, Figure 4 also provides a wafer photo after electroplating on a 4-inch diameter silicon wafer at an average current density of 1.0 ASD and the gold content at each position of the wafer.

[0150] As can be seen from the left drawing of Fig. 4, the surface plating layer of the wafer after electroplating is bright and no blackening phenomenon occurs. The numbers 1-24 in the left drawing represent the test points of the plating layer. The right drawing of Fig. 4 shows the mass percentage content of Au at the test points of the plating layer measured by the X-ray fluorescence spectrometer. As can be seen from the right drawing of Fig. 4, the Au content in the plating layer at different positions on the wafer can be in the range of 31-49wt%. Since there is a certain difference (generally about 0.3ASD) between the actual current density values at the center area and the edge area on the wafer during electroplating, the results of Fig. 4 show that the electroplating solution of the embodiment of the present application can reduce the influence of the fluctuation of the current density value during electroplating on the gold content in the obtained alloy plating layer, so that an alloy plating layer with stable gold content can be obtained.

[0151] Fig. 5 also provides a top view of a gold-silver alloy bump and its element analysis results obtained after electroplating on a 6-inch diameter patterned silicon wafer using the electroplating solution of Example 1 at an average current density of 1.0 ASD. The element analysis results of the right drawing of Fig. 5 are obtained by testing the gold-silver alloy bump using an Energy Dispersive X-Ray Spectroscopy (EDX). As can be seen from the right drawing, the gold content in the gold-silver alloy bump is 38.9wt%, which is basically consistent with the gold content in the gold-silver alloy plating layer obtained on the brass test piece using the electroplating solution of Example 1 at the same current density as described above in Table 1.

[0152] The above description is only an exemplary embodiment of the present application, which is described in a more specific and detailed manner, but should not be understood as limiting the scope of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the scope of protection of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

[0153] It should be understood that the first, second and various numerical numbers involved herein are only for the convenience of differentiation and do not limit the scope of the present application.

[0154] In the present application, the association relationship of "and / or" between the associated objects means that there can be three kinds of relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone, wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0155] In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is greater than or equal to two. "At least one" refers to one or more. "At least one of the following" or the like refers to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent: a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0156] In addition, the numerical range represented by "-" in the present application refers to the range including the minimum value and the maximum value represented by the numerical value before and after the "-" respectively. The expression of the parameter range in the present application, such as "greater than or equal to (≥)", "less than or equal to (≤)", "above", "below" all include the present number. The values and value ranges involved in the embodiments of the present application are approximate values, which may have a certain range of error due to the influence of manufacturing process / testing method, etc., which can be considered negligible by those skilled in the art.

Claims

1. An electroplating solution for electroplating a gold-silver alloy, characterized by comprising: The electroplating solution comprises a gold ion source, a silver ion source, a first complexing agent and a second complexing agent, wherein the first complexing agent comprises a hydantoin substance, and the second complexing agent comprises an organic sulfonic acid or a salt thereof.

2. The electroplating solution of claim 1, wherein, The hydantoin substance comprises at least one of hydantoin, 1-methylhydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-bromohydantoin, 5-hydroxyhydantoin, 5-ureidohydantoin, 1-amino hydantoin or a salt thereof, 5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, 1-hydroxymethyl-5,5-dimethylhydantoin, 5-methyl-5-ethylhydantoin, 1,3-dichloro-5-methyl-5-ethylhydantoin.

3. The electroplating solution of claim 1 or 2, wherein, The organic sulfonic acid comprises at least one of methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, pyridine sulfonic acid, sulfamic acid, 3-aminopropane sulfonic acid, methyl sulfonamide.

4. The electroplating solution according to any one of claims 1 to 3, wherein In the electroplating solution, the concentration of the second complexing agent in terms of organic sulfonic acid is less than that of the first complexing agent.

5. The electroplating solution according to any one of claims 1 to 4, wherein the concentration of the at least one compound of formula (I) is 0.1 to 10 g / L. The concentration of the hydantoin substance in the electroplating solution is 10-150 g / L.

6. The electroplating solution of any one of claims 1-5, wherein, In the electroplating solution, the concentration of the second complexing agent in terms of organic sulfonic acid is 1-50 g / L.

7. The electroplating solution according to any one of claims 1 to 6, wherein In the electroplating solution, the ratio of the concentration of the first complexing agent to the concentration of the second complexing agent in terms of organic sulfonic acid is 2-20.

8. The electroplating solution of any one of claims 1-7, wherein, The electroplating solution is free of cyanide ions.

9. The electroplating solution of any one of claims 1-8, wherein, The gold ion source comprises a sulfite salt of gold and / or a thiosulfate salt of gold; the gold ion source is used in an amount such that the concentration of gold ions in the electroplating solution is 1-20 g / L.

10. The electroplating solution of any one of claims 1-9, wherein, The silver ion source comprises at least one of silver nitrate, silver carbonate, silver chloride, silver acetate, and 5,5-dimethylhydantoin silver complex; the silver ion source is used in an amount such that the concentration of silver ions in the electroplating solution is 1-20 g / L.

11. The electroplating solution of any one of claims 1-10, wherein, The electroplating solution further comprises a buffering agent.

12. The electroplating solution of claim 11, wherein, The buffering agent comprises one or more of ethylenediaminetetraacetate, citrate, tartrate, phosphate, borate, and picolinate.

13. The electroplating solution of claim 11 or 12, wherein, The concentration of the buffering agent in the electroplating solution is 10-30 g / L.

14. The electroplating solution of any one of claims 1-13, wherein, The electroplating solution further comprises a pH additive; and / or, the pH of the electroplating solution is 9.0-11.

0.

15. The electroplating solution of any one of claims 1-14, wherein, The electroplating solution further comprises a brightener.

16. Use of the electroplating solution according to any one of claims 1-15 in electroplating a gold-silver alloy.

17. An electroplating apparatus characterized by comprising: It comprises: an electroplating tank, wherein the electroplating tank is filled with the electroplating solution according to any one of claims 1-15; a cathode and an anode disposed in the electroplating tank, wherein the cathode comprises a substrate to be plated, and the substrate to be plated is at least partially immersed in the electroplating solution; an electroplating power source, wherein a negative pole of the electroplating power source is electrically connected to the cathode, and a positive pole of the electroplating power source is electrically connected to the anode, so as to apply an electric current to the substrate to be plated when the electroplating power source is turned on.

18. A method of electroplating a gold-silver alloy, characterized by, It comprises: contacting a substrate to be plated with the electroplating solution according to any one of claims 1-15, and electroplating to form a gold-silver alloy plating layer on the substrate to be plated.

19. The method of electroplating a gold-silver alloy of claim 18, wherein, The electroplating is performed at a temperature of 30-60 ℃, and at a current density of 0.1-2.0 ASD.

20. The method of electroplating a gold-silver alloy of claim 18 or 19, wherein, The gold silver alloy plating layer has a gold element mass percentage of 30wt%-50wt% in a current density range of 0.3ASD.

21. An electroplated part, characterized by, The gold silver alloy plating layer has a gold element mass percentage of 30wt%-50wt% in a current density range of 0.3ASD.

22. The electroplating assembly of claim 21, wherein the electroplating assembly is configured to electroplate a plurality of layers of the metal onto the substrate. The gold silver alloy plating layer has a gold element mass percentage of 30wt%-50wt% in a current density range of 0.3ASD.

23. The electroplating member of claim 21 or 22, wherein, The gold silver alloy plating layer has a gold element mass percentage of 30wt%-50wt% in a current density range of 0.3ASD.

24. The electroplating member of any one of claims 21-23, wherein, The substrate is a semiconductor substrate; and an equivalent area of a surface of the substrate provided with the gold silver alloy plating layer is an area corresponding to a circle with a diameter of less than or equal to 12 inches.

25. A porous gold characterized in that, The porous gold is obtained by etching silver from a gold silver alloy plating layer, which is formed by electroplating using the electroplating solution according to any one of claims 1-15, or by electroplating a gold silver alloy using the method according to any one of claims 18-20.

26. An electronic device, comprising: The porous gold is obtained by etching silver from a gold silver alloy plating layer, which is formed by electroplating using the electroplating solution according to any one of claims 1-15, or by electroplating a gold silver alloy using the method according to any one of claims 18-20.

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