Electroplating solution and electroplating method, alloy bump and preparation method thereof

Abstract

The present application provides an electroplating solution and an electroplating method, an alloy bump and a preparation method thereof. The electroplating solution includes the following components in mass concentration: 5-20 g / L of water-soluble cyanide-containing gold salt, 1-15 g / L of water-soluble silver salt, 0.5-5 g / L of cobalt citrate, 1-10 g / L of refiner, 20-100 g / L of conductive salt, 10-90 g / L of complexing agent, and the remainder is deionized water; the refiner is selected from one or more of sodium lignin sulfonate, sodium 5-nitroguaiacol, sodium carboxymethyl cellulose and sodium alginate. By selecting cobalt citrate and specific substances as refiners, the gold-silver alloy bumps obtained have high hardness and low surface roughness; by combining complexing agents, antioxidants and stabilizers, the antioxidant and stability of the electroplating solution are greatly improved, and the service life is extended.

Description

Technical Field

[0001] The present application relates to the field of electroplating technology, and in particular to an electroplating solution and an electroplating method, an alloy bump and a preparation method thereof. Background Art

[0002] As a chip interconnection structure, the bump plays an important role in improving packaging density, shortening the length of interconnection lines, reducing parasitic effects during signal transmission, enhancing the heat dissipation capacity of components, and improving the reliability of integrated circuits. Therefore, the preparation of high-quality micro-bumps is one of the key technologies for microelectronic packaging. The preparation of gold bumps in wafer-level packaging is actually a dispersed local electrodeposition on the entire silicon wafer. For example, the geometric dimensions of a typical gold bump of an LCD driver chip are 50μm×108μm×17μm, the bump pitch is about 20μm, the height range of the bumps in the entire wafer should be controlled within ±2.5μm, and the height range of the bumps in the die should be controlled within ±1.5μm.

[0003] In the related art, alloy bumps with hardness, roughness and anti-sulfurization performance comparable to those of pure gold bumps can be obtained by controlling the gold content in the electroplating solution components and regulating the average grain size. However, the grain size of the gold-silver alloy layer needs to be strictly controlled within a very small range, and can only meet the technical requirements of flip-chip packaging. Therefore, it is urgent to prepare an alloy bump to meet the technical requirements of bumps for different chip packaging, especially wafer-level packaging. Summary of the invention

[0004] Based on this, in order to better meet the high quality requirements of different chip packages, especially wafer-level packaging, for bumps, the present application provides a plating solution, an alloy bump and a preparation method thereof. The plating solution includes cobalt-doped soluble gold and silver salts. The prepared alloy bumps have high and adjustable hardness, low bump surface roughness and high conformality.

[0005] The specific technical solution of this application is:

[0006] In a first aspect, the present application provides an electroplating solution, which includes the following components in mass concentration: 5-20 g / L of water-soluble cyanide gold salt, 1-15 g / L of water-soluble silver salt, 0.5-5 g / L of cobalt citrate, 1-10 g / L of refiner, 20-100 g / L of conductive salt, 10-90 g / L of complexing agent, and the balance is deionized water; the refiner is selected from one or more of sodium lignin sulfonate, sodium 5-nitroguaiacol, sodium carboxymethyl cellulose and sodium alginate.

[0007] In the present application, the mass concentration of the components is calculated on a compound basis.

[0008] In the electroplating solution described in this application, the gold concentration will affect the electroplating deposition efficiency and morphology, etc. If it is too low, the electroplating deposition efficiency will be slow and the morphology will not meet the requirements, while if it is too high, it will affect the stability of the plating solution and increase the production cost. The amount of silver and cobalt used will also affect the electroplating morphology and hardness.

[0009] In the present application, the volume of the electroplating solution is a conventional amount in the art, which may be 20-60L.

[0010] In the present application, adding a specific refiner into the electroplating solution can refine the grains, inhibit the growth of oversized grains, and reduce the surface roughness of the bumps.

[0011] In the present application, preferably, the mass concentration of the refiner is 2-8 g / L, such as 2-4 g / L.

[0012] In the present application, the water-soluble cyanide-containing gold salt is generally potassium gold cyanide.

[0013] In the present application, the water-soluble silver salt is generally silver citrate.

[0014] In the present application, the conductive salt is added to the electroplating solution to improve the conductivity of the electroplating solution so that metal ions can be smoothly deposited in the graphic area to form bumps.

[0015] Wherein, the conductive salt is generally potassium citrate.

[0016] Furthermore, the mass concentration of the conductive salt is 30-90 g / L, such as 80-90 g / L.

[0017] In the present application, the function of the composite complexing agent is to complex free metal ions in the electroplating solution to improve the stability of the electroplating solution.

[0018] The composite complexing agent is generally a composite of 1,3-dihydroxymethyl-5,5-dimethylhydantoin and ethylenediamine. Preferably, the mass ratio of the 1,3-dihydroxymethyl-5,5-dimethylhydantoin to ethylenediamine is 5:1-20:1.

[0019] In the present application, preferably, the electroplating solution also includes an antioxidant and a stabilizer.

[0020] The antioxidant in the electroplating solution can prevent other effective components such as silver from being oxidized and becoming ineffective, thereby appropriately extending the service life of the electroplating solution.

[0021] The addition of the stabilizer can inhibit the excessively rapid reduction and precipitation of metal ions, stabilize the plating solution, and improve the stability and service life of the system.

[0022] Further preferably, the antioxidant is selected from 1-phenyl-3-methyl-5-pyrazolone and / or 4-methoxyphenol.

[0023] Further preferably, the mass concentration of the antioxidant is 1-5 g / L, such as 1.5-3.5 g / L.

[0024] Further preferably, the stabilizer is selected from nitro-substituted benzoic acid derivatives, such as one or more of 3-nitrophthalic acid, 2,3-dinitrobenzoic acid, 3,5-dinitrobenzoic acid, 2-amino-5-nitrobenzoic acid and 3-methyl-2-nitrobenzoic acid.

[0025] Further preferably, the mass concentration of the stabilizer is 0.1-2.5 g / L, such as 0.2-2 g / L.

[0026] In some embodiments, the electroplating solution includes components in the following mass concentrations: potassium gold cyanide 5-20 g / L, silver citrate 1-15 g / L, cobalt citrate 0.5-5 g / L, refiner 1-10 g / L, potassium citrate 20-100 g / L, complex complexing agent 10-90 g / L, antioxidant 1-5 g / L, stabilizer 0.1-2.5 g / L, and the balance is deionized water.

[0027] In some embodiments, the electroplating solution includes components in the following mass concentrations: potassium gold cyanide 5-20 g / L, silver citrate 1-15 g / L, cobalt citrate 0.5-5 g / L, refiner 2-8 g / L, potassium citrate 30-90 g / L, complex complexing agent 10-90 g / L, antioxidant 1.5-3.5 g / L, stabilizer 0.2-2 g / L, and the balance is deionized water.

[0028] In some embodiments, the electroplating solution includes components with the following mass concentrations: potassium gold cyanide 5-20 g / L, silver citrate 1-15 g / L, cobalt citrate 0.5-5 g / L, sodium lignin sulfonate 2-8 g / L, potassium citrate 30-90 g / L, complex complexing agent 10-90 g / L, 1-phenyl-3-methyl-5-pyrazolone 1.5-3.5 g / L, 3-nitrophthalic acid 0.2-2 g / L, and the balance is deionized water.

[0029] In some preferred embodiments, the electroplating solution includes components with the following mass concentrations: 5-20 g / L potassium gold cyanide, 1-15 g / L silver citrate, 0.5-5 g / L cobalt citrate, 2-8 g / L sodium lignin sulfonate, 30-90 g / L potassium citrate, 10-90 g / L of 1,3-dihydroxymethyl-5,5-dimethylhydantoin and ethylenediamine added in a mass ratio of 5:1-20:1, 0.2-2 g / L of 3-nitrophthalic acid, and the balance is deionized water.

[0030] In some preferred embodiments, the electroplating solution includes components with the following mass concentrations: 5-20 g / L potassium gold cyanide, 1-15 g / L silver citrate, 0.5-5 g / L cobalt citrate, 2-8 g / L sodium 5-nitroguaiacol, 30-90 g / L potassium citrate, 10-90 g / L 1,3-dihydroxymethyl-5,5-dimethylhydantoin and ethylenediamine added in a mass ratio of 5:1-20:1, 1.5-3.5 g / L 1-phenyl-3-methyl-5-pyrazolone, 0.2-2 g / L 3-methyl-2-nitrobenzoic acid, and the balance is deionized water.

[0031] In some preferred embodiments, the electroplating solution includes components with the following mass concentrations: 15 g / L potassium gold cyanide, 10 g / L silver citrate, 3.5 g / L cobalt citrate, 3.5 g / L sodium lignin sulfonate, 80 g / L potassium citrate, 60 g / L 1,3-dihydroxymethyl-5,5-dimethylhydantoin, 5 ml / L ethylenediamine, 2.5 g / L 1-phenyl-3-methyl-5-pyrazolone, 0.8 g / L 3-nitrophthalic acid, and the balance is deionized water.

[0032] In a second aspect, the present application provides an electroplating method, using the aforementioned electroplating solution for electroplating.

[0033] The circulation flow rate of the electroplating solution is generally 0.1-0.5 m / s, preferably 0.1-0.3 m / s.

[0034] The electroplating temperature is generally 40-70°C, preferably 45-60°C, such as 50°C or 55°C.

[0035] The current density of the electroplating is generally 0.1-1.5 ASD, preferably 0.8-1.5 ASD, such as 1.0 ASD.

[0036] The electroplating time is generally 10-35 min, preferably 15-30 min, such as 21 min.

[0037] The pH of the electroplating solution is generally 6.0-9.0, preferably 6.0-7.0, such as 6.0 or 6.5.

[0038] In a third aspect, the present application also provides a method for preparing an alloy bump, wherein a substrate is placed in a plating solution for electroplating, and then annealed after washing and drying. The plating solution is the aforementioned plating solution, and the electroplating method is the aforementioned electroplating method.

[0039] The annealing atmosphere is generally a nitrogen atmosphere.

[0040] The annealing temperature is generally 200-300°C, preferably 250-300°C.

[0041] The annealing time is generally 10-40 min, preferably 10-30 min.

[0042] The substrate is generally a wafer to be packaged.

[0043] The washing and drying are performed by conventional operations in the art.

[0044] In a fourth aspect, the present application also provides an alloy bump produced by the aforementioned production method.

[0045] Compared with the prior art, this application has the following advantages:

[0046] (1) The present application uses a specific cobalt citrate as one of the components of the electroplating solution to controllably adjust the hardness of the gold-silver alloy bumps to meet the different hardness requirements of the gold-silver bumps for semiconductor wafer packaging; and adds a specific substance as a refiner, so that the surface roughness of the gold-silver alloy bumps obtained is low, the appearance has no color difference, and the conformal rate is high. The upper surface of the bump is flat, and when the bump height is greater than 10μm, the height difference of the bump is less than 2μm, and further is 1.3-1.7μm, which can greatly ensure the effective area of ​​the package connection and improve the subsequent packaging quality.

[0047] (2) The electroplating solution of the present application is prepared by selecting a specific complex complexing agent, an antioxidant and a stabilizer, so that the antioxidant property and stability of the electroplating solution are greatly improved, and the service life is extended, and the electroplating solution can be applied to industrial-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the description of the present application will be briefly introduced below.

[0049] Figure 1 This is an oblique electron microscope image of the electroplated bump in Example 1 at ×1000 times.

[0050] Figure 2 The 3D microscopic morphology of the lower surface of the electroplated bump in Example 2 at ×2000 magnification.

[0051] Figure 3 This is the 3D microscopic morphology of the electroplated bump in Example 3 at ×2500 magnification.

[0052] Figure 4 This is a longitudinal section electron microscope image of the electroplated bump in Example 3 at ×3000 times.

[0053] Figure 5 This is the 3D microscopic morphology of the lower surface of the electroplated bump in comparative example 1 at ×2000 times.

[0054] Figure 6 This is the 3D microscopic morphology of the lower surface of the electroplated bump in comparative example 2 at ×2000 times.

[0055] Figure 7 This is the 3D microscopic morphology of the lower surface of the electroplated bump in comparative example 4 at ×2000 times. DETAILED DESCRIPTION

[0056] Examples of the present embodiment are described in detail below. The examples are only used to explain the present embodiment and are not to be construed as limiting the present embodiment.

[0057] In the description of the present application embodiment, it should be noted that all ranges disclosed in the present application will be understood as covering any and all sub-ranges included therein. For example, the stated range "5 to 20g / L" should be deemed to include any and all following sub-ranges: it starts with a minimum value of 5g / L or greater, and ends with a maximum value of 20g / L or less, for example, 5 to 15g / L or 6 to 17g / L or 12 to 18g / L. Meanwhile, all ranges disclosed in the present application are also deemed to include the endpoints of the scope, unless otherwise explicitly stated. For example, the range "between 5.5 and 7" or "5.5 to 7" or "5.5-7" should generally be deemed to include endpoints 5.5 and 7.

[0058] Herein, unless otherwise specified, ratio refers to mass ratio and percentage refers to mass percentage.

[0059] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0060] Based on the known fact that gold-silver alloy bumps have lower resistance and higher thermal conductivity than pure alloy bumps, in order to make the gold-silver bumps produced by electroplating better meet the high quality requirements of different chip packages, especially wafer-level packages for bumps, the present application further dopes metal cobalt and selects specific cobalt citrate to prepare the gold-silver alloy bumps. In addition, a special component is selected as a refiner, and a suitable complex chelating agent is selected to match an antioxidant and a stabilizer. The cobalt-doped gold-silver bumps obtained can simultaneously meet the multiple requirements of the packaging structure for hardness, roughness, and resistance to sulfidation and oxidation, and the performance is greatly improved.

[0061] The inventors of this case selected a specific cobalt citrate for doping and controlled the cobalt doping concentration within a certain range. They found that this can effectively regulate the hardness of the alloy bumps and improve their corrosion resistance. At the same time, the height difference of the bumps can be controlled below 2μm.

[0062] In the present application, the mass concentration of the cobalt citrate is 0.5-5 g / L, preferably 1-4 g / L, and further preferably 1.5-3.5 g / L, such as 1.5 g / L, 2.5 g / L or 3.5 g / L.

[0063] In the present application, citrate is generally used as a conductive salt, which is added to the electroplating solution to improve the conductivity of the system and enable metal ions to be smoothly electrodeposited in the pattern area to eventually form a stable alloy bump.

[0064] Preferably, the citrate is potassium citrate, and further preferably, the mass concentration of the potassium citrate is 30-90 g / L, such as 80-90 g / L.

[0065] In the present application, the inventors found that sodium lignin sulfonate, sodium 5-nitroguaiacol, sodium hydroxymethyl cellulose or sodium alginate can be added to the electroplating solution and used as a refiner to refine the grains, inhibit the growth of oversized grains, and greatly reduce the surface roughness of subsequent bumps, which to a certain extent greatly guarantees the effective area of ​​the package connection and improves the package quality.

[0066] In the present application, the mass concentration of the refiner is 1-10 g / L, preferably 2-8 g / L, and further preferably 2-4 g / L, such as 2.8 g / L or 3.5 g / L.

[0067] In this application, the inventors found that in the electroplating solution components of cobalt-doped gold-silver alloy bumps, a complexing agent is used, with antioxidants and stabilizers, to comprehensively complex metal ions, prevent the oxidation failure of the active ingredients and inhibit the excessive reduction and precipitation of metal ions from multiple angles, stabilize the plating solution, and increase the life span, making it suitable for process-scale production. In this application, the term "compounding" is interpreted in the conventional sense of the art, referring to mixing two functional components according to a certain formula to achieve a specific use effect.

[0068] In the present application, preferably, the composite complexing agent is a composite of 1,3-dihydroxymethyl-5,5-dimethylhydantoin and ethylenediamine, and the ratio of the two needs to be strictly controlled to achieve a better complexing effect of free metal ions.

[0069] Further preferably, the mass ratio of the 1,3-dihydroxymethyl-5,5-dimethylhydantoin to the ethylenediamine is 5:1-20:1, more preferably 5:1-15:1, such as 40:4.5 or 60:4.5.

[0070] In the present application, the density of the ethylenediamine is generally 0.899 g / cm³.

[0071] Further preferably, the mass concentration of the composite complexing agent is 10-90 g / L, such as 40-80 g / L.

[0072] In the present application, preferably, the antioxidant is selected from 1-phenyl-3-methyl-5-pyrazolone or 4-methoxyphenol.

[0073] Preferably, the mass concentration of the antioxidant is 1.5-3.5 g / L, such as 1.5 g / L or 2.5 g / L.

[0074] In the present application, preferably, the stabilizer is selected from nitro-substituted benzoic acid derivatives.

[0075] Further preferably, the stabilizer is one or more of 3-nitrophthalic acid, 2,3-dinitrobenzoic acid, 3,5-dinitrobenzoic acid, 2-amino-5-nitrobenzoic acid and 3-methyl-2-nitrobenzoic acid.

[0076] Further preferably, the mass concentration of the stabilizer is 0.2-2 g / L, such as 0.2-1.0 g / L, and another example is 0.8 g / L.

[0077] The present application also provides a method for electroplating using the aforementioned electroplating solution.

[0078] In some embodiments, the circulation flow rate of the electroplating solution is generally 0.1-0.5 m / s, preferably 0.1-0.3 m / s.

[0079] In some embodiments, the electroplating temperature is generally 40-70°C, preferably 45-60°C, such as 50°C or 55°C.

[0080] In some embodiments, the current density of the electroplating is generally 0.1-1.5 ASD, preferably 0.8-1.5 ASD, such as 1.0 ASD.

[0081] In some embodiments, the electroplating time is generally 10-35 min, preferably 15-20 min, such as 15-21 min or 21-30 min.

[0082] In some embodiments, the pH of the plating solution is generally 6.0-9.0, preferably 6.0-7.0, such as 6.0 or 6.5.

[0083] The present application also protects a method for preparing the alloy bumps, which comprises placing a test substrate in the aforementioned electroplating solution and electroplating the substrate, wherein the electroplating method adopts the aforementioned electroplating method, and washing, drying, and annealing are performed after the electroplating is completed.

[0084] The washing and drying are generally carried out by conventional washing and drying methods in the art, and the purposes of washing and drying can be achieved respectively.

[0085] In some embodiments, the annealing atmosphere is generally a nitrogen atmosphere, the annealing temperature is generally 200-300° C., and the annealing time is generally 10-40 min.

[0086] In some preferred embodiments, the annealing atmosphere is a nitrogen atmosphere, the annealing temperature is 250° C., and the annealing time is 30 min.

[0087] The present application also protects the alloy bumps produced by the above-mentioned production method.

[0088] In some embodiments, the surface roughness Ra of the alloy bump is between 65-83 nm, preferably Ra is 68-76 nm.

[0089] In some embodiments, the bump height difference of the alloy bumps is 1.0-1.8 μm, preferably 1.3-1.7 μm.

[0090] In some embodiments, the hardness of the alloy bump is 72-90 Hv, preferably 81-89 Hv.

[0091] The present application is further explained below with reference to embodiments.

[0092] The raw materials and reagents used in the examples and comparative examples of the present application are all commercially available, and all the raw materials used are of analytical grade.

[0093] Example 1

[0094] Embodiment 1 of the present application provides an alloy bump, comprising the following steps:

[0095] S1. Prepare an electroplating solution, including the following components: 15 g / L potassium cyanide, 10 g / L silver citrate, 3.5 g / L cobalt citrate, 80 g / L potassium citrate, complexing agent: 60 g / L 1,3-dihydroxymethyl-5,5-dimethylhydantoin and 5 ml / L ethylenediamine (mass ratio is 60:4.5), 2.5 g / L 1-phenyl-3-methyl-5-pyrazolone, 3.5 g / L sodium lignin sulfonate, 0.8 g / L 3-nitrophthalic acid, and the balance is deionized water. After adding deionized water, the liquid volume reaches 20 L;

[0096] S2, placing the test substrate in the electroplating solution for electroplating, setting the electroplating temperature to 50°C, adjusting the pH value of the plating solution to 6.5, the plating solution circulation flow rate to 0.3m / s, the current density to 1.5ASD, and the electroplating time to 15min;

[0097] S3. After completion, the product is washed and dried, and annealed in a nitrogen atmosphere at 250°C for 30 minutes.

[0098] Example 2

[0099] Embodiment 2 of the present application provides an alloy bump, comprising the following steps:

[0100] S1. Prepare an electroplating solution, including the following components: 15 g / L potassium cyanogen gold, 10 g / L silver citrate, 2.5 g / L cobalt citrate, 80 g / L potassium citrate, complexing agent: 60 g / L 1,3-dihydroxymethyl-5,5-dimethylhydantoin and 5 ml / L ethylenediamine (mass ratio is 60:4.5), 1.5 g / L 4-methoxyphenol, 2.8 g / L sodium 5-nitroguaiacol, 0.8 g / L 3-nitrophthalic acid, and the balance is deionized water. After adding deionized water, the liquid volume reaches 20 L;

[0101] S2, placing the test substrate in the electroplating solution for electroplating, setting the electroplating temperature to 55°C, adjusting the pH value of the plating solution to 6.0, the plating solution circulation flow rate to 0.3m / s, the current density to 1.0ASD, and the electroplating time to 21min;

[0102] S3. After completion, the product is washed and dried, and annealed in a nitrogen atmosphere at 250°C for 30 minutes.

[0103] Example 3

[0104] Embodiment 3 of the present application provides an alloy bump, comprising the following steps:

[0105] S1. Prepare an electroplating solution, including the following components: 20 g / L potassium cyanide, 15 g / L silver citrate, 1.5 g / L cobalt citrate, 80 g / L potassium citrate, complexing agent: 40 g / L 1,3-dihydroxymethyl-5,5-dimethylhydantoin and 5 ml / L ethylenediamine (mass ratio is 40:4.5), 2.5 g / L 1-phenyl-3-methyl-5-pyrazolone, 3.5 g / L sodium 5-nitroguaiacol, 0.8 g / L 3-methyl-2-nitrobenzoic acid, and the balance is deionized water, and the liquid volume reaches 20 L after adding deionized water;

[0106] S2, placing the test substrate in the electroplating solution for electroplating, setting the electroplating temperature to 50°C, adjusting the pH value of the plating solution to 6.5, the plating solution circulation flow rate to 0.3m / s, the current density to 0.8ASD, and the electroplating time to 30min;

[0107] S3. After completion, the product is washed and dried, and annealed in a nitrogen atmosphere at 250°C for 30 minutes.

[0108] Comparative Example 1

[0109] Comparative Example 1 provides an alloy bump, comprising the following steps:

[0110] The difference between it and Example 1 is that the electroplating solution components in S1 do not contain cobalt citrate; and the current density in S2 is 1.0 ASD.

[0111] Comparative Example 2

[0112] Comparative Example 2 provides an alloy bump, comprising the following steps:

[0113] The difference between it and Example 1 is that the concentration of cobalt citrate in the electroplating solution component in S1 is 1.5 g / L, and no refiner is included; and the current density in S2 is 1.0 ASD.

[0114] Comparative Example 3

[0115] Comparative Example 3 provides an alloy bump, comprising the following steps:

[0116] The difference between this and Example 1 is that cobalt sulfate: 1.0 g / L is used in S1 to add the same molar number of cobalt element.

[0117] Comparative Example 4

[0118] Comparative Example 4 provides an alloy bump, comprising the following steps:

[0119] The difference between it and Example 1 is that in S1, 80 g / L of triammonium citrate is used as the complexing agent of the electroplating solution.

[0120] Performance Evaluation

[0121] Test 1: Surface roughness Ra test

[0122] The sample to be tested is placed in a DektakXT step profiler, and the roughness measurement procedure (refer to the procedure standard ISO:21920-1:2022) is used to measure the surface roughness Ra of the electroplated bump.

[0123] Test 2: Hardness test after annealing

[0124] After the sample to be tested is annealed, the Vickers hardness Hv value of the bump is measured using the Vickers hardness test method (national standard GB / T 4340).

[0125] Test 3: Thickness (height) measurement

[0126] The sample to be tested is placed in an X-ray thickness measuring instrument to measure the thickness of the bump. The height difference between different bumps on the wafer can be obtained by statistical analysis of multi-point thickness.

[0127] Test 4: Plating solution stability test

[0128] The prepared plating solution was placed in a 60°C water bath and heated in an empty state. The time when gold particles began to precipitate or the solution became turbid began to be recorded on the side wall or bottom of the beaker.

[0129] The test results are shown in Table 1:

[0130] Table 1

[0131] serial number Surface roughness Ra / nm Gold / Silver / Cobalt Content wt% Bump height / μm Height range / μm Hardness after annealing / Hv Bath stability Example 1 68 75% / 23% / 2% 12 1.3 89 ＞60d Example 2 83 78% / 21% / 1% 12 1.8 81 ＞60d Example 3 76 83% / 16.5% / 0.5% 13 1.7 72 ＞60d Comparative Example 1 78 76% / 24% / 0% 15 2.1 47 ＞60d Comparative Example 2 258 81% / 18% / 1% 14 2.9 85 ＞60d Comparative Example 3 89 74% / 22% / 4% 12 2.2 101 ＞60d Comparative Example 4 189 82% / 17% / 1% 14 3.5 75 ＜20d

[0132] It can be seen from the above embodiments and comparative examples that: the gold and silver bumps electroplated and deposited according to the given plating solution formula in Embodiments 1 to 3 have a fine and bright surface with a roughness of <90nm; when the bump height is >10μm, the height range of the bump is <2μm, indicating that the bump has good uniformity; and it can be seen from the slice morphology that the surface of the bump is flat, the edge corners are almost vertical, and the conformal rate is high; after annealing, the hardness decreases with the decrease of the cobalt doping amount, and the hardness is 70-90Hv, which meets the hardness requirements of semiconductor wafer packaging.

[0133] However, in Comparative Example 1, there is no cobalt doping, and the hardness of the electroplated bumps after annealing is low. It may be severely deformed during the packaging and pressing process, and may even cause short circuits between fine lines, posing a quality risk. In Comparative Example 2, because no refinement agent was used in the plating solution, the surface roughness of the electroplated bumps was high, and the overall uniformity was poor, which could not meet the surface flatness requirements of wafer-level packaging. Comparative Example 3 used different cobalt salts for electroplating doping, and the overall roughness was not much different, but the proportion of co-deposited cobalt increased, the hardness increased, and the overall height uniformity was also affected, and the range became larger. Comparative Example 4 used other complexing agents to complex the metal ions in the plating solution, but the complexing effect was poor. After electroplating, the bumps were roughly crystallized, the range was large, and the stability of the plating solution was poor.

[0134] Although examples of the present embodiment have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present embodiment, and the scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. An electroplating solution, characterized in that: The electroplating solution comprises the following components in mass concentrations: 5-20 g / L potassium gold cyanide, 1-15 g / L silver citrate, 0.5-5 g / L cobalt citrate, 1-10 g / L refiner, 20-100 g / L potassium citrate, 10-90 g / L complexing agent, 1-5 g / L antioxidant, 0.1-2.5 g / L stabilizer, and the balance is deionized water; The refiner is selected from sodium lignin sulfonate and / or sodium 5-nitroguaiacol; The composite complexing agent comprises 1,3-dihydroxymethyl-5,5-dimethylhydantoin and ethylenediamine, and the mass ratio of the 1,3-dihydroxymethyl-5,5-dimethylhydantoin to the ethylenediamine is 5:1-20:1; The antioxidant is selected from 1-phenyl-3-methyl-5-pyrazolone and / or 4-methoxyphenol; The stabilizer is a nitro-substituted benzoic acid derivative, and the nitro-substituted benzoic acid derivative is one or more of 3-nitrophthalic acid, 2,3-dinitrobenzoic acid, 3,5-dinitrobenzoic acid, 2-amino-5-nitrobenzoic acid and 3-methyl-2-nitrobenzoic acid.

2. The electroplating solution according to claim 1, characterized in that The mass concentration of the refiner is 2-8 g / L, the mass concentration of the potassium citrate is 30-90 g / L, the mass concentration of the antioxidant is 1.5-3.5 g / L, and the mass concentration of the stabilizer is 0.2-2 g / L.

3. The electroplating solution according to claim 1, characterized in that The electroplating solution comprises the following components in mass concentrations: 5-20 g / L potassium aurine cyanide, 1-15 g / L silver citrate, 0.5-5 g / L cobalt citrate, 2-8 g / L sodium lignin sulfonate, 30-90 g / L potassium citrate, 10-90 g / L composite complexing agent, 1.5-3.5 g / L 1-phenyl-3-methyl-5-pyrazolone, 0.2-2 g / L 3-nitrophthalic acid, and the balance is deionized water.

4. An electroplating method, characterized in that: Electroplating is carried out using the electroplating solution as described in any one of claims 1 to 3.

5. The electroplating method according to claim 4, characterized in that: The circulation flow rate of the electroplating solution is 0.1-0.5 m / s, the electroplating temperature is 40-70° C., the electroplating current density is 0.1-1.5 ASD, the electroplating time is 10-35 min, and the pH of the electroplating solution is 6.0-9.

0.

6. A method for preparing an alloy bump, comprising placing a substrate in an electroplating solution for electroplating, washing, drying, and then annealing, wherein: The electroplating solution is the electroplating solution as claimed in any one of claims 1 to 3; the electroplating method is the electroplating method as claimed in claim 4 or 5; and the preparation method satisfies the following conditions at the same time: a. The annealing atmosphere is a nitrogen atmosphere; b. The annealing temperature is 200-300°C; c. The annealing time is 10-40min; d. The substrate is a wafer to be packaged.

7. An alloy bump, characterized in that: The method according to claim 6 is used to prepare the product.

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