Electroplating solution for electroplating gold-silver alloy and application thereof

Abstract

The embodiment of the invention provides electroplating liquid for electroplating gold-silver alloy and application of the electroplating liquid. The electroplating liquid comprises a gold ion source, a silver ion source, a first complexing agent and a second complexing agent, the first complexing agent comprises hydantoin substances, and the second complexing agent comprises organic sulfonic acid or salt thereof. Through the synergistic effect of the two complexing agents, the stability of the electroplating liquid is high, the specific inhibition effect on silver electrodeposition can be achieved, gold deposition is not affected, the influence of current density fluctuation on the gold element content in an alloy coating is reduced, and the electroplating quality is improved. And the alloy coating with the gold element content stabilized within the range of 30-50 wt% can be prepared within the wide current density range with the interval width of at least 0.3 ASD.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electroplating gold-silver alloy, and particularly relates to an electroplating solution for electroplating gold-silver alloy and application thereof. BACKGROUND

[0002] 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 expensive. In order to reduce costs, gold-silver alloy can be used to replace pure gold in some scenarios.

[0003] Due to the larger difference between the oxidation-reduction equilibrium potentials of gold ions and silver ions, as the current density increases, the content of gold elements in the alloy plating layer will increase sharply, which makes it 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

[0004] In view of this, the present application provides an electroplating solution for electroplating gold-silver alloy and application thereof with innovative components, so as 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.

[0005] 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.

[0006] 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 that the content of gold elements in the alloy plating layer changes sharply with the current density due to the large difference between the deposition potentials of gold ions and silver ions, and ensuring that the electroplating using the electroplating solution can produce a gold-silver alloy plating layer with stable gold element content in a wide current density range. The electroplating solution can be a cyanide electroplating solution or a cyanide-free electroplating solution.

[0007] In the present application, 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.

[0008] In some 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, and methyl sulfonamide.

[0009] In some embodiments of the present application, the concentration of the second complexing agent in the electroplating solution is less than the concentration of the first complexing agent. This can ensure that the electroplating solution has good stability and is less likely to have components precipitate or decompose.

[0010] In some embodiments of the present application, the concentration of the hydantoin substance in the electroplating solution is 10 g / L-150 g / L. This can ensure that the electroplating solution has good storage stability and the appearance of the alloy plating layer obtained by electroplating is good.

[0011] In some embodiments of the present application, the concentration of the second complexing agent 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.

[0012] 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 the electroplating solution is 2-20. In this case, the synergistic effect of the two complexing agents is better, which can ensure that the current density range corresponding to the gold-silver alloy plating layer with a stable gold content of 30wt%-50wt% is wider, and the appearance of the plating layer is better.

[0013] In some embodiments of the present application, the gold ion source includes a sulfite of gold and / or a thiosulfate 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.

[0014] In some 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.

[0015] In some embodiments of the present application, the electroplating solution further includes a buffering agent. The presence of the buffering agent can improve the stability of the electroplating solution and ensure the long-term use efficiency of the electroplating solution.

[0016] In some embodiments of the present application, the buffering agent includes one or more of ethylenediaminetetraacetate, citrate, tartrate, phosphate, borate, and picolinate.

[0017] In the embodiments of the present application, the concentration of the buffering agent in the electroplating solution is 10-30 g / L. In this way, the buffering capacity of the electroplating solution is ensured to be sufficient, the stability is good, and the appearance of the plated layer formed is not uneven and too rough.

[0018] In some embodiments of the present application, the electroplating solution further comprises a pH additive; and / or, the pH of the electroplating solution is 9.0-11.0. The pH of the above-mentioned electroplating solution is in a suitable strong alkaline range, which can ensure that the complexing capacity of the above-mentioned 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.

[0019] 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 plated layer formed by using the electroplating solution.

[0020] The second aspect of the embodiments of the present application provides an application of the electroplating solution as described in the first aspect of the embodiments of the present application in electroplating a gold-silver alloy. The gold content in the gold-silver alloy plated layer formed by using the above-mentioned electroplating solution in a wider current density range is stable and uniform, which can better meet the actual application requirements.

[0021] The third aspect of the embodiments of the present application provides an electroplating device, comprising:

[0022] An electroplating tank, wherein the electroplating tank is filled with the electroplating solution as described in the first aspect of the embodiments of the present application;

[0023] 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;

[0024] An electroplating power supply, wherein the negative electrode of the electroplating power supply is electrically connected with the cathode, the positive electrode of the electroplating power supply is electrically connected with the anode, and the electroplating power supply is used to apply a current to the substrate to be plated when the electroplating power supply is turned on.

[0025] When the electroplating device filled with the above-mentioned 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 30wt%-50wt% can be formed in a current density range with a width of ≥0.3 ASD.

[0026] The fourth aspect of the embodiments of the present application provides a method for electroplating a gold-silver alloy, comprising:

[0027] Contacting a substrate to be plated with the electroplating solution as described in the first aspect of the embodiments of the present application, and electroplating to form a gold-silver alloy plated layer on the substrate to be plated.

[0028] In this embodiment, the electroplating temperature is 30-60℃; the electroplating current density is 0.1-2.0 ASD. These electroplating conditions help ensure good stability of the electroplating solution during electroplating and result in an excellent appearance of the formed alloy coating.

[0029] In this embodiment of the application, during electroplating, a gold-silver alloy coating with a gold content of 30wt%-50wt% can be formed within a current density range ≥0.3ASD. Thanks to the aforementioned electroplating solution containing specific components, fluctuations in current density have minimal impact on the gold content in the electroplated alloy coating, enabling the formation of an alloy coating with stable and uniform gold content over a wide current density range.

[0030] The fifth aspect of this application provides an electroplated part, including a substrate and a gold-silver alloy plating layer disposed on the substrate. The gold-silver alloy plating layer is formed by electroplating with the electroplating solution described in the first aspect of this application, or by electroplating gold-silver alloy using the method described in the fourth aspect of this application.

[0031] The gold-silver alloy plating on this electroplated part exhibits stable and uniform gold content and a good appearance, demonstrating promising application prospects. It is particularly suitable for etching the silver to obtain porous gold. Both the gold-silver alloy plating and the porous gold can be used as metal bonding materials.

[0032] The sixth aspect of this application provides a porous gold, which is obtained by etching silver through a gold-silver alloy plating layer. The gold-silver alloy plating layer is formed by electroplating with the electroplating solution described in the first aspect of this application, or by electroplating gold-silver alloy using the method described in the fourth aspect of this application.

[0033] Since the gold content in the gold-silver alloy coating is stable in the range of 30wt%-50wt%, the silver is relatively easy to etch away, and the porous gold obtained after removing the silver has high structural stability. Therefore, this porous gold has broad application prospects and high quality reliability.

[0034] This application also provides an electronic device that includes an electroplated part as described in the fifth aspect of this application, or a porous gold part as described in the sixth aspect of this application. Attached Figure Description

[0035] Figure 1 The diagram shows two chips to be bonded and their structure after bonding.

[0036] Figure 2 This is a schematic diagram of the structure of an electroplating apparatus provided in an embodiment of this application.

[0037] Figure 3The figure shows a linear fit between the gold content and the current density in the alloy coating formed on a brass specimen using the electroplating solution of Example 1 at different current densities.

[0038] Figure 4 Photographs of a 4-inch diameter silicon wafer after electroplating with the plating solution of Example 1 at an average current density of 1.0 ASD are provided, along with the gold content at various locations.

[0039] Figure 5 A top view and elemental analysis results are provided for gold-silver alloy bumps obtained by electroplating on a patterned silicon wafer with a diameter of 6 inches using the electroplating solution of Example 1 at an average current density of 1.0 ASD. Detailed Implementation

[0040] The embodiments of this application will now be described in conjunction with the accompanying drawings.

[0041] Figure 1 This diagram illustrates two chips to be bonded during semiconductor manufacturing and their resulting structure after bonding. (See also...) Figure 1 The chip 10a to be bonded includes a substrate 11a and a metal bonding layer 12a disposed on the substrate 11a. The other chip 10b to be bonded includes a substrate 11b and a metal bonding layer 12b disposed on the substrate 11b. Through hot pressing, the metal bonding layer 12a and the metal bonding layer 12b are fused together, thereby bonding the chips 10a and 10b. In some embodiments, the metal bonding layer 12a and the metal bonding layer 12b can be specifically a relatively inexpensive gold-silver alloy plating, or a porous gold layer; wherein, the porous gold layer can be formed by removing the silver from a gold-silver alloy plating.

[0042] Currently, electroplating solutions used for gold and silver alloys include cyanide-based and cyanide-free solutions. Because silver is more reactive than gold, and the redox equilibrium potentials of gold and silver ions differ significantly, the gold content in the alloy coating increases dramatically with increasing current density during gold-silver alloy electroplating. This phenomenon is particularly pronounced in cyanide-free solutions than in cyanide-based solutions, making it extremely difficult to deposit gold-silver alloy coatings with stable gold content over a wide current density range using either cyanide-free or cyanide-based solutions. Unstable gold content in the gold-silver alloy coating leads to significant performance deviations and affects bonding yield. Furthermore, during the electroplating process in semiconductor manufacturing, the current density varies at different locations on the substrate due to the influence of the electric field distribution. For example, the current density differs significantly between the center and edge regions of a wafer, between different opening areas of the photoresist, or between the bottom and opening of a hole in a hole pattern. This results in substantial differences in the gold content of the gold-silver alloy plating layer formed at different locations on the same substrate. In some areas, the gold content may not meet application requirements (e.g., excessively high gold content in porous gold alloy plating layers makes silver removal extremely difficult). Therefore, this application addresses the problem of drastic variations in gold content with current density in the alloy plating layer obtained during gold-silver alloy electroplating by improving the composition of the plating solution.

[0043] Specifically, embodiments of this application provide an electroplating solution for electroplating gold and silver alloys. The electroplating solution includes: a gold ion source, a silver ion source, a first complexing agent, and a second complexing agent. The first complexing agent includes a hydantoin-like substance, and the second complexing agent includes an organic sulfonic acid or its salt.

[0044] In the aforementioned electroplating solution, the combined use of hydantoin-based substances and organic sulfonic acids or their salts as complexing agents can prevent the deposition of gold and silver ions in the electroplating solution. This also specifically inhibits the electrodeposition of highly reactive silver without affecting gold deposition. This makes the polarization of these two ions more consistent during the electroplating process, thereby significantly reducing the problem of drastic changes in gold content with current density in the alloy coating caused by excessive differences in the deposition potentials of gold and silver ions, as well as the problem of large differences in gold content in different areas of the alloy coating due to large differences in current density at different locations on the substrate. Therefore, electroplating with this solution can produce gold-silver alloy coatings with relatively stable gold content.

[0045] In some embodiments of this application, the electroplating solution may be free of cyanide ions (CN). -That is, the above-mentioned electroplating solution is a cyanide-free electroplating solution. When using existing cyanide-free electroplating solutions to electroplat gold and silver alloys, the phenomenon that the gold content in the alloy coating increases with increasing current density is particularly serious. However, this application introduces both the first and second complexing agents into the cyanide-free electroplating solution for electroplating gold and silver alloys, which can achieve the deposition of a gold and silver alloy coating with stable gold content over a wider current density range, and the cyanide-free electroplating solution has high environmental friendliness. In some other embodiments of this application, the above-mentioned electroplating solution contains cyanide ions (CN). - That is, the electroplating solution is a cyanide-based electroplating solution. Using a cyanide-based electroplating solution containing the aforementioned first and second complexing agents to electroplat gold and silver alloys can also solve the problem of large variations in gold content in the alloy coating with current density, and can also achieve the deposition of gold and silver alloy coatings with stable gold content over a wide range of current densities.

[0046] The aforementioned hydantoin substances may be substituted or unsubstituted hydantoin or their salts. In the embodiments of this application, the hydantoin substances may include at least one of the following: hydantoin, 1-methylhydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-bromohydantoin, 5-hydroxyhydantoin, 5-ureidohydantoin, 1-aminohydantoin or their salts, 5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, 1-hydroxymethyl-5,5-dimethylhydantoin, 5-methyl-5-ethylhydantoin, and 1,3-dichloro-5-methyl-5-ethylhydantoin, but are not limited thereto.

[0047] The structural formula of hydantoin is: The structural formula of 1-methylhydantoin is: The structural formula of 5-methylhydantoin is: The structural formula of 5-ethylhydantoin is: The structural formula of 5-bromohydantoin is: The structural formula of 5-hydroxyhydantoin is: The structural formula of 5-ureidohydantoin is The structural formula of 1-aminohydantoin is: The structural formula of 5,5-dimethylhydantoin is: The structural formula of 1,3-dibromo-5,5-dimethylhydantoin is: The structural formula of 1-hydroxymethyl-5,5-dimethylhydantoin is: The structural formula of 5-methyl-5-ethylhydantoin is The structural formula of 1,3-dichloro-5-methyl-5-ethylhydantoin is:

[0048] In the embodiments of this application, the organic sulfonic acid may include at least one of methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, pyridinesulfonic acid, aminosulfonic acid, 3-aminopropanesulfonic acid, and methanesulfonamide, but is not limited thereto. Generally, when the pH of the above-mentioned electroplating solution is above 8, these organic sulfonic acids exist in the system in the form of organic sulfonates.

[0049] The structural formula of methanesulfonic acid is: The chemical formula for ethanesulfonic acid is CH3CH2-S(=O)2OH. The chemical formula for propanesulfonic acid can also be CH3CH2CH2-S(=O)2OH. Pyridinesulfonic acid can specifically include 3-pyridinesulfonic acid. and / or pyridine-4-sulfonic acid The structural formula of aminosulfonic acid is The structural formula of 3-aminopropanesulfonic acid is: methyl

[0050] The structural formula of sulfamethoxazole is:

[0051] In this embodiment of the application, the concentration of the second complexing agent in the electroplating solution, calculated as an organic sulfonic acid, is lower than the concentration of the hydantoin-like substance. Both concentrations are expressed in g / L. Thus, the hydantoin-like substance acts as the main complexing agent, and the second complexing agent acts as an auxiliary complexing agent, ensuring good stability of the electroplating solution.

[0052] In this embodiment, the concentration of the hydantoin-like substance in the electroplating solution can be between 10 g / L and 150 g / L. A suitable concentration of the hydantoin-like substance in the electroplating solution ensures good stability of the electroplating solution containing gold and silver ion sources, preventing decomposition / precipitation, while also preventing excessive complexation by the hydantoin-like substance, which could lead to poor appearance of the plating layer (such as blackening). Specifically, the concentration of the hydantoin-like substance in the electroplating 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. In some embodiments, the concentration of hydantoin in the electroplating solution is 50 g / L-150 g / L, or more specifically 60 g / L-150 g / L, 50 g / L-100 g / L, or 60 g / L-100 g / L.

[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 this embodiment, the amount of gold ion source used ensures that the concentration of gold ions in the electroplating solution is 1 g / L-20 g / L. That is, the concentration of the gold ion source, calculated as gold ions, is 1 g / L-20 g / L. Maintaining this concentration range ensures sufficient gold ions in the electroplating solution, preventing excessively low gold deposition efficiency on the cathode during electroplating, while also preventing excessively high gold ion concentrations that could lead to waste of gold source and increased production costs due to carryover from the plating solution after electroplating. 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. In some embodiments, the concentration of gold ions in the plating solution is 5-15 g / L.

[0057] In this embodiment, the silver ion source may include at least one of silver nitrate, silver carbonate, silver chloride, silver acetate, and 5,5-dimethylhydantoin silver complex. In the presence of the first and second complexing agents described above, these silver ion sources can remain stable in aqueous electroplating solutions without settling. Among them, the 5,5-dimethylhydantoin silver complex exhibits higher stability in the aforementioned electroplating solution.

[0058] In this embodiment, the amount of silver ion source used ensures that the concentration of silver ions in the electroplating solution is between 1 g / L and 20 g / L. This concentration range ensures sufficient silver ions for electrodeposition without wasting the silver ion source. 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. In some embodiments, the concentration of gold ions in the plating solution is 5-15 g / L.

[0059] In some embodiments of this application, the electroplating solution further includes a buffer. The buffer can be used to enhance the buffering capacity of the electroplating solution, improve the stability of the gold ion source and silver ion source in the electroplating solution, and ensure the long-term effectiveness of the electroplating solution.

[0060] In this embodiment, the buffer may include one or more of ethylenediaminetetraacetic acid (EDTA), citrate, tartrate, phosphate, borate, and pyridinecarboxylate. Specifically, EDTA may be selected from one or more of disodium EDTA, dipotassium EDTA, and magnesium disodium EDTA. Citrate may be selected from one or more of sodium citrate, potassium citrate, and ammonium citrate. Tartrate may be selected from one or more of sodium tartrate and sodium potassium tartrate. Phosphate may be selected from one or more of potassium dihydrogen phosphate (also known as monopotassium phosphate), disodium hydrogen phosphate, dipotassium hydrogen phosphate, and sodium dihydrogen phosphate. Borate may be selected from one or more of sodium borate, potassium borate, and ammonium borate. Pyridinecarboxylate may be selected from one or more of sodium pyridinecarboxylate and potassium pyridinecarboxylate.

[0061] In this embodiment, the concentration of the buffer in the electroplating solution is 10 g / L-30 g / L. A suitable concentration of buffer ensures sufficient buffering capacity and good stability of the electroplating solution, while also preventing uneven or excessively rough appearance of the resulting plating layer. Specifically, the concentration of the buffer 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 this application, the plating solution may further contain a pH additive. The pH additive may be an alkali and / or an acid. Exemplarily, the alkali may be at least one selected from potassium hydroxide, sodium hydroxide, ammonia, etc. The acid may be one or more selected from sulfurous acid, sulfuric acid, hydrochloric acid, etc. In some embodiments, the pH additive is at least one selected from potassium hydroxide, sodium hydroxide, and ammonia.

[0063] To ensure the first and second complexing agents possess good complexing abilities and the long-term stability of the plating solution, the pH of the electroplating solution is alkaline. In this embodiment, the pH of the electroplating solution can be 9.0-11.0. Specifically, a pH not exceeding 11.0 avoids excessively strong complexing abilities of the two complexing agents, which could lead to poor coating appearance (such as blackening or roughness). The pH of the electroplating solution 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.

[0064] In some embodiments of this application, the electroplating solution further includes a brightener. The brightener helps improve the surface brightness and smoothness of the gold-silver alloy plating layer formed using the electroplating solution, thereby preventing poor bonding (such as voids leading to high contact resistance) during the bonding process. The brightener may be selected from at least one of polyethylenepolyamine, polyethyleneimine and its derivatives, bipyridine and its derivatives, and o-phenanthroline.

[0065] In this application, the electroplating solution is an aqueous solution. Understandably, the plating solution also contains water as a solvent.

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

[0067] Furthermore, the order in which the components are added is not limited in the preparation of the above-mentioned electroplating solution. In some embodiments of this application, the method for preparing the above-mentioned electroplating solution includes: mixing a gold ion source, a silver ion source, a first complexing agent, a second complexing agent, and optionally a buffer agent and a brightener (if present) in water; adjusting the pH of the mixture to a predetermined pH using a pH adjuster; adjusting the volume of the mixture to a predetermined volume; and obtaining an electroplating solution that meets the requirements for the concentration of each component. Wherein, when the pH of the obtained plating solution is 9.0-11.0, the added second complexing agent exists in the electroplating solution in the form of an organic sulfonate.

[0068] This application also provides the application of the above-described electroplating solution in electroplating gold and silver alloys. This electroplated gold and silver alloy can be used for filling holes and trenches on a substrate, fabricating redistribution layers, etc. Specifically, the application of this electroplated gold and silver alloy can be used to prepare electroplated parts with a gold and silver alloy coating, and it 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 completely placed in an electroplating tank containing the aforementioned electroplating solution. An anode may be placed in this electroplating tank. The anode, for example, can be a platinum-titanium plate. The cathode and anode can be electrically connected to the electroplating power source via wiring, and using the aforementioned electroplating solution as an electrolyte, the cathode and anode together form a conductive circuit (see [link to documentation]). Figure 2 This allows for the deposition of electroplated gold and silver alloys on the substrate to be plated.

[0075] To better understand the electroplating process described above, this application also provides an electroplating apparatus. See [link to relevant documentation]. 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 terminal electrically connected to the cathode 22 and its positive terminal electrically connected to the anode 23, so that current is applied to the substrate to be plated when the electroplating power supply 24 is turned on.

[0079] In this configuration, the cathode 22 and anode 23 are generally placed opposite each other and are typically separated, for example, by a diaphragm 25. Furthermore, Figure 2 Although the cathode 22 and anode 23 are placed vertically in the electroplating tank 20, it is understandable that the cathode 22 and anode 23 can also be placed horizontally in the electroplating tank 20 depending on specific needs.

[0080] During electroplating, a potential is typically applied to the cathode 22, so that when the electroplating power supply 24 is turned on, a current is also applied to the substrate to be plated. During electroplating, gold and silver ions in the electroplating solution are reduced at the cathode 22, thereby forming a gold-silver alloy on the substrate. After obtaining a gold-silver alloy plating layer with a predetermined amount of gold and silver deposition, the electroplating process is completed.

[0081] The current applied during the electroplating process can be direct current, pulsed current, or other suitable current. In some embodiments of this application, the applied current is direct current. Compared to pulsed current, when using direct current for electroplating, the adsorption of additives (such as complexing agents, brighteners, etc.) in the electroplating solution that regulate the properties of the plating layer at the electrochemical interface does not change much, making it easier to obtain a plating layer with easily controllable hardness and roughness.

[0082] In this embodiment, the electroplating temperature is 30-60℃, specifically 30℃, 32℃, 35℃, 38℃, 40℃, 42℃, 45℃, 48℃, 50℃, 55℃, 58℃, or 60℃. A suitable electroplating temperature ensures high plating solution precipitation efficiency, avoids uneven coating appearance, and guarantees high overall stability of the plating solution, preventing difficulties in plating solution management due to excessively rapid evaporation.

[0083] In this embodiment of the application, the current density of the electroplating is between 0.1 and 2.0 ASD (i.e., A / dm²). 2 Within the range of current density, decomposition of the plating solution components or abnormal appearance of the coating may occur.

[0084] In this embodiment, during electroplating, a gold-silver alloy coating with a gold content of 30wt%-50wt% can be formed within a current density range ≥ 0.3 ASD. Even when using direct current electroplating, as mentioned earlier, the current density varies at different locations on the substrate due to the influence of the electric field distribution. For example, when electroplating a wafer with an average current density of 1.0 ASD, the current density difference between the center and edge regions of the wafer is generally greater than or equal to 0.3 ASD. When using the electroplating solution described in this application, a current density range ≥ 0.3 ASD can be found, and within this current density range, a gold-silver alloy coating with a gold content in the range of 30wt%-50wt% can be formed. This solves the problem of obtaining a gold-silver alloy coating with a stable gold content within a wide current density operating range. The gold content in the gold-silver alloy coating is in the range of 30-50 wt%, which ensures that the silver in the alloy coating is easy to etch away, and that the porous gold formed after etching the silver can maintain good structural stability.

[0085] In this embodiment, the gold content (by mass percentage) in any region of the formed gold-silver alloy coating is within the range of 30 wt% to 50 wt%. The gold content in any region of the alloy coating is unaffected by its distribution location, remaining within the 30 wt% to 50 wt% range, thus ensuring the consistency of the overall coating's structural characteristics and performance (e.g., high consistency in density, wear resistance, and hardness). Furthermore, it avoids the situation where excessively high gold content in the alloy coating leads to severe silver encapsulation, making it difficult to completely remove silver during subsequent dealloying and obtain a more stable porous gold structure; conversely, excessively low gold content results in extremely poor structural stability of the alloy coating after dealloying.

[0086] In some embodiments of this application, after electroplating, the formed gold-silver alloy coating may be annealed to improve the hardness of the gold-silver alloy coating and the uniformity of atomic mixing within the gold-silver alloy coating.

[0087] This application also provides an electroplated part, which includes a substrate and a gold-silver alloy plating layer disposed on the substrate. The gold-silver alloy plating layer is formed by electroplating with the electroplating solution described in this application embodiment or by electroplating the gold-silver alloy using the method described in this application embodiment.

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

[0089] As described above, in any region of the gold-silver alloy plating on the electroplated part, the mass percentage of gold is within the range of 30wt%-50wt%. Thanks to the aforementioned electroplating solution containing specific components, fluctuations in current density have little effect on the gold content in the plating, enabling the acquisition of an alloy plating with stable and uniform gold content over a wide range of current densities.

[0090] In some embodiments of this application, the difference in the mass percentage of gold in any two regions of the gold-silver alloy coating is less than or equal to 20%. In this case, the equivalent area of ​​the substrate surface on which the gold-silver alloy coating is disposed is preferably the area of ​​a circle with a diameter of less than 12 inches. The substrate can be circular or other shapes. Using the electroplating solution provided in the embodiments of this application can significantly reduce the difference in gold content in different regions of the gold-silver alloy coating on the substrate. Taking the formation of a gold-silver alloy coating on a silicon wafer with a diameter of less than 12 inches as an example, the difference in the mass percentage of gold in the gold-silver alloy coating located at the center and edge of the wafer is less than or equal to 20% in the equivalent surface area. It should be noted that if the substrate is not circular, its surface area can be equivalent to the area of ​​a circle (the diameter of the circle does not exceed 12 inches), and the difference in the mass percentage of gold in any two regions of the gold-silver alloy coating formed on such a substrate is still less than or equal to 20%.

[0091] In this application, no limitations are imposed on the thickness, hardness, surface roughness, etc. of the formed gold-silver alloy coating.

[0092] This application also provides a porous gold, which is obtained by etching silver after the gold-silver alloy plating layer prepared in the above-described embodiments of this application is formed.

[0093] In some embodiments of this application, the silver in the gold-silver alloy plating can be etched away by immersing it in nitric acid. The resulting porous gold can have a loose, porous structure, and can also be called a porous gold sponge, which has nanoscale pore sizes.

[0094] This porous gold can also be used as a metal bonding material, exhibiting good electrical conductivity and compressibility. Because the gold content in the formed gold-silver alloy coating is stable and uniform, ranging from 30wt% to 50wt%, the silver is easily etched away, and the resulting porous gold exhibits high structural stability, making it less prone to structural collapse during hot pressing. Furthermore, besides its use as a metal bonding material, this porous gold can also be used as a filter material, catalyst, sensor material, or biological agent.

[0095] This application also provides an electronic device, which includes the electroplated part or the porous gold described in this application. Specifically, the electroplated part or porous gold can be disposed on the circuit board of the electronic device.

[0096] In this application embodiment, the electronic device can be a mobile phone, tablet computer, laptop computer, wearable device (such as a smartwatch, smart bracelet), television, camera, video recorder, camcorder, home smart device, vehicle device, or other terminal product; it can also be various wired or wireless communication devices such as antennas, radar, routers, gateways, walkie-talkies, switches, surge arresters, etc.; or a communication base station. The circuit boards of these terminal products, communication devices, or communication base stations may be connected to the aforementioned electroplated parts or porous gold.

[0097] The embodiments of this application will be further described below through multiple examples.

[0098] Example 1

[0099] An electroplating solution for electroplating gold and silver alloys is prepared by: adding a gold source in the form of sodium gold sulfite, a silver source in the form of a 5,5-dimethylhydantoin silver complex, a first complexing agent (specifically 5,5-dimethylhydantoin), a second complexing agent (specifically aminosulfonic acid), and a buffer (specifically boric acid) to a 2L beaker containing deionized water; adjusting the pH of the resulting mixture to 10 using sodium hydroxide; stirring to fully dissolve all the raw materials; and adjusting the volume of the mixture to a predetermined volume to obtain the desired electroplating solution. In this electroplating solution, the concentrations of gold ions (8 g / L), silver ions (8 g / L), 5,5-dimethylhydantoin (80 g / L), aminosulfonate (calculated as aminosulfonic acid) (15 g / L), and borate (15 g / L) are all present.

[0100] Electroplating experiments were conducted using the above-mentioned electroplating solution: The electroplating solution from Example 1 was heated to 40°C and placed in an electroplating tank. The temperature of the electroplating solution in the tank was maintained at 40°C. A titanium plate with a surface area of ​​9 cm² was used as the anode. 2A rectangular brass specimen was used as the cathode. Electroplating experiments were conducted at four suitable current densities within the range of 0.4-1.2 ASD. In this embodiment, 0.6 ASD, 0.8 ASD, 1.0 ASD, and 1.2 ASD were selected. Assuming an electroplating efficiency of 100%, the electroplating time required to form a 10 μm thick alloy coating at different current densities was calculated, and electroplating was performed according to these times. After electroplating, the mass percentage of gold and silver in each alloy coating was measured using X-ray fluorescence spectrometry. The change in gold content in the alloy coating at different current densities was linearly fitted with the change in current density, and the slope was calculated as a parameter to evaluate the electroplating effect. If a coating with a gold content of 30-50 wt% needs to be prepared within a current density range of at least 0.3 ASD, the slope value of the gold content vs. current density in the alloy coating, calculated based on 20 wt% / 0.3 ASD, must be less than 66.

[0101] Figure 3 The diagram shows a linear fit between the gold content and the current density in the alloy coatings formed on brass specimens using the electroplating solution of Example 1 at different current densities. Figure 3 The fitted relationship shows that the slope of the gold content vs. current density in the alloy coating in Example 1 is 58, which satisfies the condition of being less than 66. From... Figure 3 The fitting relationship can be calculated that the electroplating solution of Example 1 can produce an alloy coating with a gold content of 30-50 wt% in the current density range of 0.81-1.16 ASD, and the current density range is wide, from 0.35 ASD to greater than 0.3 ASD.

[0102] Example 2

[0103] An electroplating solution differs from Example 1 in that the second complexing agent is replaced with 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 based on 3-pyridine sulfonic acid.

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

[0105] Example 3

[0106] An electroplating solution differs from Example 1 in that the second complexing agent is replaced with methanesulfonic acid, and the second complexing agent in the final electroplating solution is methanesulfonate, with a concentration of 15 g / L based on methanesulfonic acid.

[0107] According to the method described in Example 1, the electroplating solution of Example 3 was subjected to electroplating experiments at several different current density values. The gold content in the alloy coating 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 differs from Example 1 in that the second complexing agent is replaced with 3-aminopropanesulfonic acid, and the second complexing agent in the final electroplating solution is 3-aminopropanesulfonate, with a concentration of 10 g / L based on 3-aminopropanesulfonic acid.

[0110] According to the method described in Example 1, the electroplating solution of Example 4 was subjected to electroplating experiments at several different current density values. The gold content in the alloy coating 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 differs from Example 1 only in that the amount of aminosulfonic acid used in preparing the electroplating solution is changed so that the concentration of aminosulfonate in the final electroplating solution, calculated as aminosulfonic acid, is 25 g / L.

[0113] According to the method described in Example 1, the electroplating solution of Example 5 was subjected to electroplating experiments at several different current density values. The gold content in the alloy coating 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 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, the concentration of the second complexing agent (aminosulfonate) is 5 g / L based on the corresponding organic sulfonic acid, and the concentration ratio of the two is 12.

[0116] Example 7

[0117] An electroplating solution 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, the concentration of the second complexing agent (aminosulfonate) is 40 g / L based on the corresponding organic sulfonic acid, and the concentration ratio of the two is 3.5.

[0118] Example 8

[0119] An electroplating solution differs from Example 5 only in that the concentration of the first complexing agent (5,5-dimethylhydantoin) in the electroplating solution is 100 g / L, the concentration of the second complexing agent (aminosulfonate) is 40 g / L based on the corresponding organic sulfonic acid, and the concentration ratio of the two is 2.5.

[0120] Example 9

[0121] An electroplating solution differs from Example 5 only in that the concentration of the second complexing agent (aminosulfonate) is 50 g / L based on the corresponding organic sulfonic acid, and the concentration ratio of the two is 1.6.

[0122] Example 10

[0123] An electroplating solution differs from Example 5 only in that the concentration of the first complexing agent (5,5-dimethylhydantoin) is 140 g / L, the concentration of the second complexing agent (aminosulfonate) is 5 g / L based on the corresponding organic sulfonic acid, and the concentration ratio of the two is 28.

[0124] Example 11

[0125] An electroplating solution differs from Example 5 only in that the first complexing agent is replaced with hydantoin, and its concentration in the electroplating solution is 80 g / L. The concentration of aminosulfonate, calculated as aminosulfonic acid, remains 25 g / L.

[0126] To highlight the beneficial effects of the embodiments of this application, the following comparative examples are provided.

[0127] Comparative Example 1

[0128] An electroplating solution differs from Example 1 only in that: no second complexing agent is added during the preparation of the electroplating solution, and the electroplating solution of Comparative Example 1 does not contain a second complexing agent, while the concentrations of other components are the same as in Example 1.

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

[0130] Comparative Example 2

[0131] An electroplating solution differs from Example 1 only in that the second complexing agent is replaced with hydroxyethylidene diphosphonic acid, which exists in the electroplating solution in the form of hydroxyethylidene diphosphonate, the concentration of which is 10 g / L based on hydroxyethylidene diphosphonic acid.

[0132] According to the method described in Example 1, the electroplating solution of Comparative Example 2 was subjected to electroplating experiments at several different current density values. The gold content in the alloy coating 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] An electroplating solution differs from Example 1 only in that the second complexing agent is replaced with disodium ethylenediaminetetraacetate, which has a concentration of 30 g / L in the electrolyte.

[0135] According to the method described in Example 1, the electroplating solution of Comparative Example 3 was subjected to electroplating experiments at several different current density values. The gold content in the alloy coating 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] An electroplating solution that differs from Example 1 only in that the second complexing agent is replaced with thymine, and the concentration of thymine in the electroplating solution is 10 g / L.

[0138] According to the method described in Example 1, the electroplating solution of Comparative Example 4 was subjected to electroplating experiments at several different current density values. The gold content in the alloy coating 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] An electroplating solution that differs from Example 1 only in that the electroplating solution of Comparative Example 5 does not contain hydantoin complexing agents, while the concentrations of other components are the same as in Example 1.

[0141] The electroplating solution of Comparative Example 5 became turbid after 1 hour of preparation, making it impossible to continue the electroplating experiment according to the method of Example 1.

[0142] Table 1 below summarizes the test results of electroplating gold and silver alloys on brass test pieces using the electroplating solutions of each embodiment or comparative example, as well as the slope of the fitted straight line between the gold content in the alloy coating and the current density used for electroplating.

[0143] Table 1

[0144]

[0145] The comparison between Comparative Example 5 and Example 1 shows that when the electroplating solution does not contain hydantoin as a complexing agent, the stability of the electroplating solution is poor. The electroplating solution will quickly decompose due to the photosensitivity of silver ions, resulting in turbidity of the electroplating solution.

[0146] A comparison of Example 1 and Comparative Example 1 in Table 1 shows that, when the electroplating solution contains hydantoin-based complexing agents, the introduction of organic sulfonates as complexing agents can effectively maintain the stability of the gold content in the electroplated alloy coating. A wider current density range with a width greater than 0.3 ASD can be found, and alloy coatings with a gold content in the range of 30-50 wt% can be prepared within this wider current density range. A comparison of Example 1 and Comparative Examples 2-4 shows that using commonly used electroplating complexing agents (hydroxyethylidene diphosphonic acid, or disodium ethylenediaminetetraacetate) or using thymine, which has a certain complexing effect on silver, instead of the organic sulfonates used in this application, cannot achieve the goal of obtaining alloy coatings with a stable gold content in the range of 30-50 wt% within a wider current density range.

[0147] Compared with Example 1, Examples 2-4 mainly changed the type of the second complexing agent, but still achieved similar results to Example 1: alloy coatings with a stable gold content of 30-50 wt% can be obtained over a wide current density range.

[0148] Furthermore, a comparison between Example 1 and Example 5 reveals that when the type of the second complexing agent in the electroplating solution is the same (both are organic sulfonates) but the content is different, the electroplating solution of Example 5 exhibits a better electroplating effect. The slope of the gold element content of the plating layer versus the current density is 35. Based on this slope, the range of current density corresponding to obtaining an alloy plating layer with an Au content of 30-50 wt% can be calculated to be 0.57 ASD, which is sufficient to cope with the influence of the non-uniformity of current density caused by the electric field distribution during wafer electroplating.

[0149] Furthermore, a comparison between Examples 9 and 10 and Examples 5, 6, 7, and 8 reveals that when the mass concentration ratio of the first complexing agent to the concentration of the second complexing agent (calculated as organic sulfonic acid) in the electroplating solution is greater than 2 and less than 28 (e.g., in the range of 2-20), the slope of the gold content relative to the current density in the alloy coating formed by the electroplating solution at different current densities is smaller. Correspondingly, the range of electroplating current densities corresponding to the formation of an alloy coating with an Au content in the range of 30-50 wt% is also wider, making it easier to increase the electroplating process window.

[0150] To demonstrate that the electroplating solution provided in the embodiments of this application can achieve good electroplating results on actual substrates, Figure 4 Also provided are photographs of a 4-inch diameter silicon wafer after electroplating with the plating solution of Example 1 at an average current density of 1.0 ASD, and the gold content at each location.

[0151] from Figure 4As shown in the middle left image, the surface coating on the wafer after electroplating is bright and there is no blackening. The numbers 1-24 in the left image represent the test points of the coating taken. Figure 4 The right-middle figure shows the mass percentage of Au at these coating test points, measured using X-ray fluorescence spectrometry. From... Figure 4 As shown in the right-middle figure, the Au content in the plating layer at different locations on the wafer ranges from 31-49 wt%. This difference is due to the difference in actual current density between the central and edge regions of the wafer during electroplating (the difference is generally around 0.3 ASD). Figure 4 The results show that the electroplating solution used in this application embodiment can reduce the influence of fluctuations in current density during electroplating on the gold content in the resulting alloy coating, thereby obtaining an alloy coating with stable gold content.

[0152] Figure 5 A top view and elemental analysis results of gold-silver alloy bumps prepared by electroplating on a 6-inch patterned silicon wafer at an average current density of 1.0 ASD using the electroplating solution of Example 1 are also provided. Figure 5 The elemental analysis results shown in the right-hand figure were obtained using energy-dispersive X-ray spectroscopy (EDX) on the gold-silver alloy bump. The figure indicates that the gold content in the bump is 38.9 wt%, which is essentially consistent with the gold content in the gold-silver alloy coating obtained on a brass sample using the electroplating solution from Example 1 at the same current density, as shown in Table 1 above.

[0153] The above description merely illustrates exemplary embodiments of this application, and while the description is specific and detailed, it should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0154] It should be understood that the use of the terms "first," "second," and various numerical designations in this document is merely for descriptive convenience and is not intended to limit the scope of this application.

[0155] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0156] In the description of this application, unless otherwise stated, "multiple" means two or more. "At least one" means one or more. "At least one of the following" or similar expressions refer 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 both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0157] Furthermore, the numerical range indicated by "-" in this application refers to the range including the values ​​before and after "-" as the minimum and maximum values, respectively. Expressions of parameter ranges in this application, such as "greater than or equal to (≥)", "less than or equal to (≤)", "above", and "below", all include the stated number. The numerical values ​​and ranges involved in the embodiments of this application are approximate values ​​and may have a certain range of errors due to the influence of manufacturing processes / testing methods, etc. These errors are negligible to those skilled in the art.

Claims

1. An electroplating solution for electroplating gold and silver alloys, characterized in that, The electroplating solution includes a gold ion source, a silver ion source, a first complexing agent, and a second complexing agent, wherein the first complexing agent includes a hydantoin-like substance, and the second complexing agent includes an organic sulfonic acid or its salt.

2. The electroplating solution as described in claim 1, characterized in that, The hydantoin compounds include at least one of the following: hydantoin, 1-methylhydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-bromohydantoin, 5-hydroxyhydantoin, 5-ureidohydantoin, 1-aminohydantoin or its salts, 5,5-dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin, 1-hydroxymethyl-5,5-dimethylhydantoin, 5-methyl-5-ethylhydantoin, and 1,3-dichloro-5-methyl-5-ethylhydantoin.

3. The electroplating solution as described in claim 1 or 2, characterized in that, The organic sulfonic acid includes at least one of methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, pyridinesulfonic acid, aminosulfonic acid, 3-aminopropanesulfonic acid, and methanesulfonamide.

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

5. The electroplating solution according to any one of claims 1-4, characterized in that, The concentration of the hydantoin in the electroplating solution is 10 g / L-150 g / L.

6. The electroplating solution according to any one of claims 1-5, characterized in that, In the electroplating solution, the concentration of the second complexing agent, calculated as organic sulfonic acid, is 1 g / L-50 g / L.

7. The electroplating solution according to any one of claims 1-6, characterized in that, In the electroplating solution, the concentration ratio of the first complexing agent to the second complexing agent (calculated as organic sulfonic acid) is 2-20.

8. The electroplating solution according to any one of claims 1-7, characterized in that, The electroplating solution does not contain cyanide ions.

9. The electroplating solution according to any one of claims 1-8, characterized in that, The gold ion source includes gold sulfite and / or gold thiosulfate; the amount of gold ion source used is such that the concentration of gold ions in the electroplating solution is 1 g / L-20 g / L.

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

11. The electroplating solution according to any one of claims 1-10, characterized in that, The electroplating solution also includes a buffer.

12. The electroplating solution as described in claim 11, characterized in that, The buffer includes one or more of ethylenediaminetetraacetic acid, citrate, tartrate, phosphate, borate, and pyridinecarboxylate.

13. The electroplating solution as described in claim 11 or 12, characterized in that, The concentration of the buffer in the electroplating solution is 10 g / L-30 g / L.

14. The electroplating solution according to any one of claims 1-13, characterized in that, The electroplating solution further includes a pH additive; and / or, the pH of the electroplating solution is 9.0-11.

0.

15. The electroplating solution according to any one of claims 1-14, characterized in that, The electroplating solution also includes a brightener.

16. The application of the electroplating solution as described in any one of claims 1-15 in the electroplating of gold and silver alloys.

17. An electroplating apparatus, characterized in that, include: An electroplating tank, wherein the electroplating tank is filled with an electroplating solution as described in any one of claims 1-15; A cathode and an anode are disposed in the electroplating tank, wherein the cathode includes a substrate to be plated, and the substrate to be plated is at least partially immersed in the electroplating solution; An electroplating power supply, wherein the negative terminal of the electroplating power supply is electrically connected to the cathode and the positive terminal of the electroplating power supply is electrically connected to the anode, so as to apply current to the substrate to be plated when the electroplating power supply is turned on.

18. A method for electroplating a gold-silver alloy, characterized in that, include: The substrate to be plated is brought into contact with the electroplating solution as described in any one of claims 1-15, and electroplating is performed to form a gold-silver alloy coating on the substrate.

19. The method for electroplating gold and silver alloys as described in claim 18, characterized in that, The electroplating temperature is 30-60℃; the electroplating current density is 0.1-2.0 ASD.

20. The method for electroplating gold and silver alloys as described in claim 18 or 19, characterized in that, During the electroplating process, a gold-silver alloy plating layer with a gold element mass percentage of 30wt%-50wt% can be formed within a current density range with a width of ≥0.3ASD.

21. An electroplated part, characterized in that, It includes a substrate and a gold-silver alloy plating layer disposed on the substrate, the gold-silver alloy plating layer being formed by electroplating with an electroplating solution as described in any one of claims 1-15, or by electroplating a gold-silver alloy as described in any one of claims 18-20.

22. The electroplated part as described in claim 21, characterized in that, In any region of the gold-silver alloy coating, the mass percentage of gold is in the range of 30wt%-50wt%.

23. The electroplated part as described in claim 21 or 22, characterized in that, The difference in the mass percentage of gold in any two regions of the gold-silver alloy coating is less than or equal to 20%.

24. The electroplated part according to any one of claims 21-23, characterized in that, The substrate is a semiconductor substrate; the equivalent area of ​​the surface of the substrate on which the gold and silver alloy plating is disposed is the area corresponding to a circle with a diameter of less than 12 inches.

25. A porous gold, characterized in that, The porous gold is obtained by etching silver through a gold-silver alloy plating layer. The gold-silver alloy plating layer is formed by electroplating with the electroplating solution as described in any one of claims 1-15, or by electroplating gold-silver alloy as described in any one of claims 18-20.

26. An electronic device, characterized in that, It includes the electroplated part as described in any one of claims 21-24, or the porous gold as described in claim 25.

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