Gold electroplating solution and use thereof

Abstract

Embodiments of this application provide a gold electroplating solution, including an aurous cyanide salt serving as a gold source, an oxalate, a lead-containing compound, a water-soluble polysaccharide substance, and an organic acid conductive medium, where the organic acid conductive medium includes an organic phosphonic acid or a salt of the organic phosphonic acid. Under cooperative coordination of the organic acid conductive medium and other components, it can be ensured that an electrical conduction rate of the electroplating solution is relatively high, and a gold bump obtained through electroplating has high surface flatness, and has high hardness after heat treatment, so that the gold bump is particularly suitable for reliable interconnection between a semiconductor substrate and a substrate between which there is a small spacing. Embodiments of this application further provide a related application of the foregoing gold electroplating solution.

Description

[0001] This application claims priority to Chinese Patent Application No. 202211706098.3, filed with the China National Intellectual Property Administration on December 29, 2022 and entitled "GOLD ELECTROPLATING SOLUTION AND APPLICATION THEREOF", which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] This application relates to the field of electroplating technologies, and specifically to a gold electroplating solution and an application thereof.BACKGROUND

[0003] During manufacture of a liquid crystal display, interconnection between a liquid crystal drive chip and a routing substrate is usually implemented by using a gold bump (Gold Bump) technology. With development of liquid crystal display technologies, there is an increasingly high requirement for a display resolution, a contrast, and the like of the display, and the liquid crystal drive chip, as a control unit, is required to achieve better performance. Therefore, a size of a gold bump on the chip and a spacing between gold bumps need to be correspondingly reduced. However, when the size of the gold bump and the spacing between gold bumps are reduced, during thermal compression bonding between the chip and the substrate, the gold bumps are prone to deformation, and consequently adjacent gold bumps are connected to each other, causing short-circuiting. To resolve this problem, it is especially necessary to develop a gold bump with high hardness (90 HV to 120 HV).

[0004] At present, gold electroplating solutions used for forming a gold bump may be classified into a cyanide electroplating solution and a non-cyanide electroplating solution based on whether a gold source is a cyanide. The non-cyanide electroplating solution has high costs, and the electroplating solution cannot compete with the cyanide electroplating solution in terms of stability. However, a gold bump formed by using a conventional cyanide electroplating solution has low hardness. Especially after heat treatment at a relatively high temperature (for example, at least 260°C), it is relatively difficult to ensure that the hardness is at least 90 HV. In addition, appearance uniformity and flatness of a surface of the gold bump are relatively poor.SUMMARY

[0005] In view of this, embodiments of this application provide a gold electroplating solution that can be used to make a high-hardness gold bump, to resolve a problem that it is difficult to make a gold bump obtained by using an existing cyanide gold electroplating solution have both high surface flatness and high hardness after heat treatment.

[0006] A first aspect of embodiments of this application provides a gold electroplating solution, including an aurous cyanide salt serving as a gold source, an oxalate, a lead-containing compound, a water-soluble polysaccharide substance, and an organic acid conductive medium, where the organic acid conductive medium includes an organic phosphonic acid or a salt of the organic phosphonic acid.

[0007] In the foregoing cyanide gold electroplating solution, under cooperative coordination of the foregoing specific components such as the organic acid conductive medium, the water-soluble polysaccharide substance, the oxalate, and the lead-containing compound, it can be ensured that an electrical conduction rate and precipitation efficiency of the electroplating solution are high, and an electroplated gold layer obtained through electroplating has an even and flat surface and high hardness. Therefore, the electroplating solution can be used to form a gold bump with high surface flatness and high hardness after heat treatment, and the gold bump is particularly suitable for reliable electrical interconnection between a semiconductor substrate and a substrate between which there is a small spacing.

[0008] In an implementation of this application, an electrical conductivity of the electroplating solution at a room temperature ranges from 40 mS / cm to 90 mS / cm. When the specific organic acid conductive medium is used, the electrical conductivity of the electroplating solution can still meet a requirement of gold electroplating, and an obtained electroplated gold layer has a uniform appearance and high surface flatness.

[0009] In an implementation of this application, the electroplating solution does not include an inorganic acid conductive salt. In the case in which the electroplating solution does not include an inorganic acid conductive salt, the electrical conductivity of the electroplating solution is still appropriate, and an electroplated gold layer with a uniform thickness, a uniform appearance, and high surface flatness can be prepared by using the electroplating solution.

[0010] In an implementation of this application, in the electroplating solution, a concentration of the organic acid conductive medium in terms of organic phosphonic acids ranges from 10 g / L to 100 g / L. In some implementations, in the electroplating solution, the concentration of the organic acid conductive medium in terms of organic phosphonic acids ranges from 55 g / L to 95 g / L. This is relatively beneficial for the electroplating solution to have appropriate viscosity and an appropriate conduction rate, and an electroplated gold layer obtained by using the electroplating solution has relatively high hardness and surface flatness.

[0011] In an implementation of this application, at least one of hydroxyethylidene diphosphonic acid, amino trimethylene phosphonic acid, and ethylenediamine tetramethylenephosphonic acid is selected as the organic phosphonic acid.

[0012] In an implementation of this application, the water-soluble polysaccharide substance includes at least one of dextrin, α-cyclodextrin, β-cyclodextrin, or dextran.

[0013] In an implementation of this application, a concentration of the water-soluble polysaccharide substance in the electroplating solution ranges from 0.1 g / L to 5 g / L. An appropriately low concentration of the water-soluble polysaccharide substance can cooperate with the lead-containing compound and the organic phosphonic acid to increase hardness of the electroplated gold layer after heat treatment, without affecting purity of the electroplated gold layer.

[0014] In an implementation of this application, a ratio of mass of the organic acid conductive medium in terms of organic phosphonic acids to mass of the water-soluble polysaccharide substance is (9-900): 1. In this case, there is a better synergistic effect between the water-soluble polysaccharide substance and the organic acid conductive medium.

[0015] In an implementation of this application, pH of the electroplating solution ranges from 5 to 7. The lead-containing compound in the weakly acidic electroplating solution may have relatively high solubility, and it is not easy to precipitate. Moreover, the aurous cyanide salt does not affect a gold electroplating effect due to precipitation in an excessively acidic system.

[0016] A second aspect of embodiments of this application provides an application of the electroplating solution according to the first aspect of the embodiments of this application in gold electroplating.

[0017] In an implementation of this application, the application includes an application in preparing a semiconductor gold-electroplated part provided with a gold bump.

[0018] The electroplating solution in this application can be used to form an electroplated gold layer that has a regular shape, a uniform appearance, low roughness, and high flatness and that still has relatively high hardness after heat treatment, so that a high requirement of gold electroplating in the semiconductor field can be better met.

[0019] A third aspect of embodiments of this application provides a gold electroplating method, including: causing a to-be-electroplated part to be in contact with the electroplating solution according to the first aspect of the embodiments of this application; and applying a current to the to-be-electroplated part to perform electroplating, to form an electroplated gold layer on the to-be-electroplated part.

[0020] In an implementation of this application, after the electroplating, the method further includes: performing heat treatment at a temperature ranging from 260°C to 300°C; and hardness of the electroplated gold layer ranges from 90 HV to 120 HV after the heat treatment. After heat treatment is performed at a relatively high temperature, the electroplated gold layer formed by using the foregoing electroplating solution provided in the embodiments of this application still has relatively high hardness, and can be better used in the semiconductor field. In some implementations, hardness of the electroplated gold layer ranges from 95 HV to 120 HV after the heat treatment.

[0021] A fourth aspect of embodiments of this application provides a gold-electroplated part, including a substrate and an electroplated gold layer disposed on the substrate, where the electroplated gold layer may be formed through electroplating using the electroplating solution according to the first aspect of the embodiments of this application, or may be formed by using the gold electroplating method according to the third aspect of the embodiments of this application. The electroplated gold layer on the gold-electroplated part has a uniform appearance, high surface flatness, and relatively high hardness after heat treatment, and has a wider application prospect.

[0022] In an implementation of this application, surface roughness Ra of the electroplated gold layer falls within a range of 60 nm to 100 nm when a thickness of the electroplated gold layer ranges from 7 µm to 11 µm. Appropriately high Ra is conducive to alignment and bonding between the electroplated gold layer and the substrate.

[0023] In some implementations of this application, the electroplated gold layer is a gold bump, and the substrate is a semiconductor substrate. The gold-electroplated part in this case may be referred to as a semiconductor gold-electroplated part provided with a gold bump.

[0024] In an implementation of this application, hardness of the gold bump falls within a range of 90 HV to 120 HV; and a height difference between a point farthest to the substrate and a point nearest to the substrate on a surface that is of the gold bump and that is away from the substrate is less than 1.2 µm. This can reflect that the surface that is of the gold bump and that is away from the substrate has high flatness, and hardness of the gold bump is high after the heat treatment. By using the gold bump, convenient and stable interconnection between the gold-electroplated part and the substrate can be implemented.

[0025] The embodiments of this application further provide a gold-electroplated part, including a substrate and an electroplated gold layer disposed on the substrate, where the electroplated gold layer is formed through electroplating using an electroplating solution containing an aurous cyanide salt, and surface roughness Ra of the electroplated gold layer falls within a range of 60 nm to 100 nm when a thickness of the electroplated gold layer ranges from 7 µm to 11 µm.

[0026] In an implementation of this application, hardness of the electroplated gold layer falls within a range of 90 HV to 120 HV, and further falls within a range of 95 HV to 120 HV.

[0027] In some implementations of this application, the electroplated gold layer is a gold bump; and a height difference between a point farthest to the substrate and a point nearest to the substrate on a surface that is of the gold bump and that is away from the substrate is less than 1.2 µm.

[0028] The foregoing electroplated gold layer has high surface flatness, high hardness, and good toughness, is conducive to alignment and bonding with the substrate, and has a wide application prospect.

[0029] In some implementations, the electroplating solution further includes an oxalate, a lead-containing compound, a water-soluble polysaccharide substance, and an organic acid conductive medium, where the organic acid conductive medium includes an organic phosphonic acid or a salt of the organic phosphonic acid. In other words, the electroplated gold layer is formed through electroplating using the electroplating solution according to the first aspect of the embodiments of this application.

[0030] The embodiments of this application further provide an electronic device. The electronic device includes the foregoing gold-electroplated part according to the embodiments of this application.BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 is a diagram of a process in which a gold bump is formed by using a gold electroplating solution; FIG. 2 is a diagram of a structure of an electroplating apparatus according to an embodiment of this application; FIG. 3 is a diagram of a structure of a gold-electroplated part according to an embodiment of this application; FIG. 4 compiles microscopic profile images of electroplated gold layers obtained through electroplating on unpatterned silicon wafers using an electroplating solution in Embodiment 1 and an electroplating solution in Comparative Example 1 respectively, where (a) in FIG. 4 is the image of the electroplated gold layer obtained by using the electroplating solution in Embodiment 1, and (b) in FIG. 4 is the image of the electroplated gold layer obtained by using the electroplating solution in Comparative Example 1; FIG. 5 is a cross-sectional view of a patterned silicon wafer provided with a gold bump and formed through electroplating using the electroplating solution in Embodiment 1 of this application; and FIG. 6 compiles a top-view microscopic image (a in FIG. 6) of the patterned silicon wafer provided with the gold bump and obtained by using the electroplating solution in Embodiment 1, a top-view profile image (b in FIG. 6) of the gold bump, a top-view microscopic image (c in FIG. 6) of a patterned silicon wafer provided with a gold bump and obtained by using the electroplating solution in Comparative Example 1, and a top-view profile image (d in FIG. 6) of the gold bump. DESCRIPTION OF EMBODIMENTS

[0032] The following describes technical solutions in this application with reference to accompanying drawings in embodiments of this application.

[0033] FIG. 1 is a diagram of a process in which a gold bump 6 is formed by using a gold electroplating solution according to an embodiment of this application. (A) in FIG. 1 is a diagram of a structure of a to-be-electroplated part on which gold electroplating is to be performed. The structure shown in (A) in FIG. 1 includes a substrate 1, an electrode 2 disposed on a surface on one side of the substrate 1, and a passivation layer 3 covering the substrate 1 and the electrode 2. The passivation layer 3 is provided with a specific opening that exposes a part of the electrode 2. A lower metal layer 4 is formed on the passivation layer 3, the lower metal layer 4 covers the passivation layer 3 and the electrode 2 exposed from an opening 3a of the passivation layer 3, and the conductive lower metal layer 4 is a forming basis for gold electroplating. The lower metal layer 4 includes a TiW layer and a gold seed layer that are stacked, and the TiW layer is close to the electrode 2, so that bonding force between the electrode 2 and the gold seed layer can be increased. A photoresist layer 5 is formed on a surface of the lower metal layer 4, the photoresist layer 5 is provided with an opening part 5a that can allow a part of the lower metal layer 4 to be exposed, and the opening part 5a is located above the electrode 2. Gold electroplating is subsequently performed in the opening part 5a to form a gold bump 6, as shown in (B) in FIG. 1. After the photoresist layer 5 is removed from the structure shown in (B) in FIG. 1, the structure may be bonded with a printed routing substrate and the like, which is specifically implemented by bonding the gold bump 6 with a substrate electrode on the printed routing substrate.

[0034] Hardness of the gold bump 6 formed by using a conventional cyanide gold electroplating solution is usually not high. Especially after heat treatment is performed at a relatively high temperature (for example, at least 260°C), it is relatively difficult to ensure that the hardness of the gold bump 6 is at least 90 HV. In addition, surface flatness of the gold bump 6 is relatively poor, and a surface 601 that is of the gold bump 6 and that is away from one side of the electrode 2 fluctuates greatly. In other words, a distance between a point that is on the surface 601 and that is nearest to the substrate 1 (point a in the figure) and a point that is on the surface 601 and that is farthest to the substrate 1 (point b in the figure) is relatively long. This greatly reduces an effective contact area during bonding. Therefore, this application provides a cyanide gold electroplating solution that can be used to make a gold bump with both high surface flatness and high hardness after heat treatment.

[0035] Specifically, the gold electroplating solution provided in embodiments of this application includes an aurous cyanide salt serving as a gold source, an oxalate, a lead-containing compound, a water-soluble polysaccharide substance, and an organic acid conductive medium, where the organic acid conductive medium includes an organic phosphonic acid or a salt of the organic phosphonic acid.

[0036] A specific organic acid conductive medium used in the foregoing cyanide gold electroplating solution can reduce resistance of the electroplating solution, increase an electrical conductivity of the electroplating solution, and ensure that a surface of an electroplated gold layer formed through electroplating using the electroplating solution is more uniform (for example, almost no protruding gold nodule is generated) and has higher flatness and better performance of filling a step-shaped opening part; and the organic acid conductive medium further has a function of increasing hardness of the electroplated gold layer to some extent. The oxalate, as an organic acid conductive salt, may also help increase a conduction rate of the electroplating solution, and may prevent the electroplating solution from penetrating into a photoresist layer and prevent an electroplated gold film from being formed under the photoresist layer, thereby ensuring that gold electroplating is performed in a limited area. The water-soluble polysaccharide substance can increase hardness of the electroplated gold layer. The lead-containing compound can adjust crystallinity, crystal orientation, and the like of the obtained electroplated gold layer, improve a depolarization effect of the electroplating solution, reduce an electroplating voltage, and improve precipitation efficiency of the electroplating solution, and can also help increase the hardness of the electroplated gold layer. Therefore, under cooperative coordination of the foregoing components, it can be ensured that the electroplating solution can be used to form an electroplated gold bump with high surface flatness, and film hardness of the gold bump is relatively high after heat treatment. Particularly, after heat treatment is performed at a relatively high temperature (for example, at least 260°C), the hardness of the gold bump may be still at least 90 HV, for example, 95 HV to 120 HV. The gold bump with high surface flatness and high hardness is particularly suitable for reliable electrical interconnection between a semiconductor substrate and a substrate between which there is a small spacing.

[0037] In an implementation of this application, an electrical conductivity of the electroplating solution at a room temperature ranges from 40 mS / cm to 90 mS / cm. In this case, the electrical conductivity of the electroplating solution is relatively appropriate, an electroplated gold layer formed through electroplating has a relatively uniform thickness and high surface flatness. The term "room temperature" may be any temperature from 20°C to 30°C, for example, 22°C, 25°C, or 28°C; and 25°C is relatively common.

[0038] In an implementation of this application, the electroplating solution does not include an inorganic acid conductive salt. The inorganic acid conductive salt may be inorganic phosphate (for example, potassium phosphate, sodium phosphate, or ammonium phosphate). In a case in which the electroplating solution does not include the inorganic acid conductive salt, the electrical conductivity of the electroplating solution is relatively appropriate. This is conducive to forming an electroplated gold layer with a uniform thickness, a uniform appearance, and high surface flatness. In addition, the electroplated gold layer still has relatively high hardness after heat treatment. It should be noted that "the electroplating solution does not include the inorganic acid conductive salt" is not limited to a case in which content of the inorganic acid conductive salt is definitely 0. When the content of the inorganic acid conductive salt in the electroplating solution is less than or equal to 100 mg / L, it may also be considered that the electroplating solution does not include the inorganic acid conductive salt.

[0039] In an implementation of this application, at least one of hydroxyethylidene diphosphonic acid (HEDP), amino trimethylene phosphonic acid (ATMP), and ethylenediamine tetramethylenephosphonic acid (EDTMP) is selected as the organic phosphonic acid. In some implementations, the organic phosphonic acid is hydroxyethylidene diphosphonic acid and / or amino trimethylene phosphonic acid. In this case, the organic acid conductive medium is better for improving a leveling effect of the electroplating solution.

[0040] In an implementation of this application, in the electroplating solution, a concentration of the organic acid conductive medium in terms of organic phosphonic acids ranges from 10 g / L to 100 g / L. In other words, when the organic acid conductive medium is an organic phosphonic acid, a concentration of the organic phosphonic acid ranges from 10 g / L to 100 g / L; and when the organic acid conductive medium is organic phosphonate, a concentration of an organic phosphonic acid corresponding to the organic phosphonate ranges from 10 g / L to 100 g / L. An appropriate concentration of the organic acid conductive medium can ensure that surface flatness of the electroplated gold layer formed by using the electroplating solution is obviously high, and does not excessively increase viscosity of the electroplating solution or reduce an electrical conduction rate. Specifically, the concentration of the organic acid conductive medium in terms of organic phosphonic acids may be 15 g / L, 20 g / L, 25 g / L, 30 g / L, 40 g / L, 50 g / L, 52 g / L, 55 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 95 g / L, or the like. In some implementations, in the electroplating solution, the concentration of the organic acid conductive medium in terms of organic phosphonic acids ranges from 10 g / L to 50 g / L. In some other implementations, the concentration of the organic acid conductive medium in terms of organic phosphonic acids ranges from 55 g / L to 95 g / L, and may further range from 55 g / L to 90 g / L, 55 g / L to 85 g / L, or the like. In this case, it is more beneficial for the foregoing electroplating solution to have appropriate viscosity, a higher electrical conduction rate, and a relatively high precipitation effect; and the obtained electroplated gold layer has appropriate hardness and higher surface flatness.

[0041] In an implementation of this application, the water-soluble polysaccharide substance includes at least one of dextrin, α-cyclodextrin, β-cyclodextrin, or dextran. A concentration of the water-soluble polysaccharide substance in the electroplating solution may range from 0.1 g / L to 5 g / L. The foregoing cyanide gold electroplating solution includes the foregoing organic acid conductive medium, so that content of the water-soluble polysaccharide substance can be appropriately low. This can ensure that the water-soluble polysaccharide substance can cooperate with the lead-containing compound and the organic acid conductive medium to increase hardness of the electroplated gold layer after heat treatment, and can also avoid a case in which purity of the electroplated gold layer is obviously reduced because the polysaccharide substance is included in the electroplated gold layer due to excessive addition of the water-soluble polysaccharide substance. Specifically, the concentration of the water-soluble polysaccharide substance in the electroplating solution may be 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.8 g / L, 1.0 g / L, 1.5 g / L, 2.0 g / L, 2.5 g / L, 3.0 g / L, 3.5 g / L, 4.0 g / L, 4.5 g / L, 4.8 g / L, 5.0 g / L, or the like. In some implementations, the concentration of the water-soluble polysaccharide substance in the electroplating solution may range from 0.1 g / L to 4.5 g / L, and may further range from 0.2 g / L to 4.5 g / L.

[0042] In some implementations of this application, a ratio of mass of the organic acid conductive medium calculated in terms of organic phosphonic acids to mass of the water-soluble polysaccharide substance is (9-900):1. In this case, there is a relatively good synergistic effect between the water-soluble polysaccharide substance and the organic acid conductive medium. Specifically, the mass ratio may be 10, 11, 12, 13, 15, 18, 20, 50, 60, 65, 80, 100, 200, 300, 500, 550, 600, 650, 700, 800, or the like. In some embodiments, the mass ratio is (11-900):1, and may further be (11-850): 1. In some other embodiments, the mass ratio is (13-850):1, and may further be (13-650):1. In this case, there is a better synergistic effect between the water-soluble polysaccharide substance and the organic acid conductive medium. This not only can obviously increase hardness of the electroplated gold layer after the heat treatment and surface flatness of the electroplated gold layer, but also can ensure that the electroplated gold layer has relatively high purity.

[0043] In an implementation of this application, the aurous cyanide salt includes at least one of potassium aurous cyanide, sodium aurous cyanide, and ammonium aurous cyanide. Solubility of these cyanide salts of monovalent gold in the foregoing electroplating solution is relatively high. In an implementation of this application, an amount of the aurous cyanide salt causes a concentration of gold ions ranging from 1 g / L to 15 g / L in the electroplating solution. In other words, a concentration of the aurous cyanide salt calculated in terms of gold ions ranges from 1 g / L to 15 g / L. The concentration of gold ions falls within this range, so that it can be ensured that precipitation efficiency of gold on a to-be-electroplated part at a cathode is not excessively low during electroplating, thickness distribution of an electroplated gold layer is relatively uniform. In addition, a case in which a gold source is wasted and production costs are increased due to the removal of the electroplating solution after electroplating is completed, and the like can be avoided. Specifically, the concentration of gold ions in the electroplating solution is specifically 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, 14.5 g / L, or the like.

[0044] In an implementation of this application, at least one of potassium oxalate, sodium oxalate, and ammonium oxalate is selected as the oxalate. A concentration of the oxalate in the electroplating solution ranges from 5 g / L to 80 g / L. An appropriate concentration of the oxalate can ensure that the electroplating solution can be effectively prevented from penetrating the photoresist layer; and can avoid a case in which excessively high oxalate content causes an undesirable appearance of the electroplated gold layer, for example, a phenomenon in which the electroplated gold layer is burnt. Specifically, the concentration of the oxalate in the electroplating solution may be 5 g / L, 8 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, or the like. In some implementations, a concentration of the oxalate in the electroplating solution ranges from 10 g / L to 50 g / L.

[0045] In an implementation of this application, at least one of lead acetate, lead nitrate, lead citrate, and lead sulfate is selected as the lead-containing compound. In the electroplating solution, a concentration of the lead-containing compound in terms of lead element ranges from 2 mg / L to 15 mg / L. In other words, a concentration of a lead element in the electroplating solution is 2 mg / L to 15 mg / L. The lead-containing compound of appropriately low content can ensure that crystallinity and hardness of the electroplated gold layer can be adjusted, and avoids a case in which purity of the electroplated gold layer is reduced due to the inclusion of excessive Pb impurities in the formed electroplated gold layer.

[0046] In an implementation of this application, the electroplating solution further includes a pH additive. The pH additive may be an acid or a base, where at least one of organic phosphonic acids used as the foregoing organic conductive medium may be selected as the acid; and at least one of potassium hydroxide, sodium hydroxide, ammonia water, and the like may be selected as the base. In an implementation of this application, pH of the electroplating solution ranges from 5 to 7. The lead-containing compound has relatively good solubility in the weakly acidic electroplating solution, and is not easy to precipitate to avoid impact on an effect of the electroplating solution, so that the electroplating solution has good long-term stability. In addition, the aurous cyanide salt does not cause hydrogen cyanide volatilization and impact on a gold electroplating effect that are caused due to excessively low pH of the system. The pH of the electroplating solution may be specifically 5.0, 5.2, 5.5, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, or the like. In some implementations, the pH of the electroplating solution ranges from 5.5 to 7, and may further range from 6 to 7.

[0047] In this application, the cyanide gold electroplating solution is an aqueous solution. It may be understood that the electroplating solution further includes water used as a solvent.

[0048] In this application, the electroplating solution may be prepared after the foregoing components are completely dissolved in water. Each component may be added in a solid form or in a form of a corresponding aqueous solution. Usually, for the organic phosphonic acid or a salt of the organic phosphonic acid, the oxalate, and the water-soluble polysaccharide substance, corresponding compounds may be directly added into water for complete dissolution. A gold source is added in a form of a solid salt, but an actual amount of the gold source is calculated based on a gold element. An actual amount of the lead-containing compound is also calculated based on an actually introduced lead element, and the lead-containing compound is usually added after pH of the system is adjusted to weakly acidic for dissolution. In some implementations, a method for preparing the electroplating solution includes: First, the organic phosphonic acid or a salt of the organic phosphonic acid is mixed with water to obtain a completely dissolved solution; then pH of the solution is adjusted to predetermined pH by using a pH regulator; then the oxalate and the gold source are added; after the solution is fully dissolved, the lead-containing compound and the water-soluble polysaccharide substance are added; and after the solution is completely dissolved, the mixture is adjusted to a predetermined volume and predetermined pH to obtain an electroplating solution, and the electroplating solution is allowed to meet a requirement for a concentration of each component. When the pH of the electroplating solution ranges from 5 to 7, an added raw material of the organic phosphonic acid usually exists in the electroplating solution in a form of organic phosphonate (for example, organic phosphonate potassium salt, organic phosphonate sodium salt, and organic phosphonate ammonium salt).

[0049] An embodiment of this application further provides an application of the foregoing cyanide gold electroplating solution. The application may be specifically a function in preparing a gold-electroplated part, and may further be preparing a semiconductor gold-electroplated part. In some implementations, the application is an application in preparing a semiconductor gold-electroplated part provided with a gold bump.

[0050] For electroplating in the semiconductor field, there are specific technical requirements on hardness, roughness, flatness, and the like of an electroplated gold layer. The foregoing cyanide gold electroplating solution provided in this application is particularly suitable for the semiconductor manufacturing field, and is suitable for electroplating a semiconductor substrate with a patterned photoresist layer, to obtain a semiconductor gold-electroplated part product provided with a gold bump, for example, a liquid crystal drive chip, a CMOS image sensor, and a fingerprint sensor. Interconnection between a chip and a substrate may be implemented by using a flip technology TAB (Tape Automated Bonding), COG (Chip on glass), COF (Chip on Film), COP (Chip on Plastics), or the like.

[0051] An electroplated gold layer prepared by using the foregoing electroplating solution provided in the embodiments of this application can meet technical requirements of the semiconductor field for hardness, flatness, roughness, and the like of the electroplated gold layer, and the prepared semiconductor gold-electroplated part has a good line forming capability, a regular shape, and no infiltration plating defect, and has a good application prospect in the semiconductor field.

[0052] An embodiment of this application further provides a gold electroplating method, including: causing a to-be-electroplated part to be in contact with the electroplating solution according to the foregoing embodiment of this application; and applying a current to the to-be-electroplated part to perform electroplating, to form an electroplated gold layer on the to-be-electroplated part to obtain the gold-electroplated part.

[0053] Specifically, during electroplating, the to-be-electroplated part is usually used as a cathode, and may be partially or completely placed in an electroplating tank in which the electroplating solution is provided; and an anode may be placed in the electroplating tank. The anode may be, for example, a platinum-coated titanium plate. The cathode and the anode each may be electrically connected to an electroplating power supply through routing. The foregoing electroplating solution is used as an electrolyte, and the cathode and the anode jointly form a conducting loop to implement deposition of electroplated gold on a to-be-electroplated part.

[0054] To better understand the foregoing electroplating process, an embodiment of this application further provides an electroplating apparatus. Refer to FIG. 2. The electroplating apparatus 200 includes: an electroplating tank 20, where the electroplating tank 20 is internally provided with the foregoing electroplating solution 21 in this embodiment of this application; a cathode 22 and an anode 23 disposed in the electroplating tank 20, where the cathode 22 includes a to-be-electroplated part, and at least a part of the to-be-electroplated part is immersed in the electroplating solution 21; and an electroplating power supply 24, where a negative electrode of the electroplating power supply 24 is electrically connected to the cathode 22, and a positive electrode of the electroplating power supply is electrically connected to the anode 23, to apply a current to the to-be-electroplated part when the electroplating power supply 24 is powered on.

[0055] The cathode 22 and the anode 23 are usually disposed opposite to each other, and are usually separated from each other, for example, separated by using a diaphragm 25. In addition, in FIG. 2, although the cathode 22 and the anode 23 are vertically placed in the electroplating tank 20, it may be understood that the cathode 22 and the anode 23 may also be horizontally placed in the electroplating tank 20 based on a specific requirement.

[0056] During electroplating, a potential is usually applied to the cathode 22. In this way, when the electroplating power supply 24 is powered on, a current is also applied to the to-be-electroplated part correspondingly. During electroplating, gold ions in the electroplating solution are reduced at the cathode 22 to form metal gold on the to-be-electroplated part. The applied current may be a direct current, a pulse current, or another suitable current.

[0057] In some implementations of this application, the to-be-electroplated part may be a substrate without a complex device structure, for example, an unpatterned wafer or a wafer with an epitaxially stacked structure. In other implementations of this application, the to-be-electroplated part is a patterned wafer. The patterned wafer includes a substrate and a passivation layer disposed on the substrate, the passivation layer is provided with at least one opening formed by using a patterned photoresist layer, and one opening can expose one corresponding electrode on the substrate. Gold electroplating is specifically performed in the opening. After the photoresist layer is removed, the electroplated gold layer obtained through electroplating is usually protruded on the passivation layer, and is provided with a step. Therefore, the electroplated gold layer may be referred to as a "gold bump". The substrate is usually a semiconductor substrate, for example, a silicon substrate. The gold bump is usually formed on a semiconductor chip, and the gold bump is a key structure for implementing interconnection between the semiconductor chip and the substrate.

[0058] In some embodiments, the to-be-electroplated patterned wafer may be shown in (A) in FIG. 1, and include a substrate 1, a patterned electrode 2, and a passivation layer 3 that covers the electrode 2 and the substrate 1, where the patterned electrode 2 and the passivation layer 3 are sequentially stacked on the substrate 1. A lower metal layer 4 is deposited in an opening 3a of the passivation layer 3, and a photoresist layer 5 is disposed on each of two sides of an opening 3a of the passivation layer 3. An opening part 5a (or referred to as a gap) between adjacent photoresist layers 5 allows a part of the lower metal layer 4 to be exposed. Electroplating may be performed in the opening part 5a, and an electroplated gold layer formed through electroplating in the opening part 5a may be referred to as a gold bump.

[0059] In an implementation of this application, a temperature of the electroplating ranges from 30°C to 50°C. For example, the temperature is specifically 32°C, 35°C, 40°C, 45°C, 48°C, or 50°C. An appropriate electroplating temperature can ensure that the electroplating solution has relatively high precipitation efficiency, avoid a uniform appearance of an electroplated layer, and ensure high stability of the overall electroplating solution. In this way, a case in which it is difficult to manage the electroplating solution due to excessively rapid volatilization of the electroplating solution can be avoided. In an implementation of this application, a current density during electroplating ranges from 0.1 A / dm 2< to 1.0 A / dm 2< (that is, ASD). When the current density exceeds the foregoing range, the electroplated layer may have a non-uniform appearance, defect filling may occur, and the like. In addition, a total time of electroplating can be adjusted based on a size parameter of an electroplated gold layer to be formed and a concentration of each component in the electroplating solution.

[0060] In an implementation of this application, purity of gold in the electroplated gold layer formed by using the foregoing electroplating solution is relatively high, and the purity of gold may be greater than or equal to 99.9%.

[0061] In an implementation of this application, after electroplating, the method further includes: performing heat treatment at a temperature ranging from 200°C to 300°C for more than 5 minutes, so that hardness of the electroplated gold layer obtained after the heat treatment still falls within a range of 90 HV to 120 HV. Heat treatment can increase toughness of the electroplated gold layer, and ensure impact resistance of a connecting piece subsequently connected by using the electroplated gold layer. Usually, heat treatment causes a decrease in hardness of the electroplated gold layer to some extent. However, the electroplated gold layer formed by using the foregoing electroplating solution in this embodiment of this application still has relatively high hardness after heat treatment is performed at a relatively high temperature. In some implementations of this embodiment of this application, after the electroplating, after heat treatment is performed at a temperature ranging from 260°C to 300°C for 0.5 hours to 2 hours, the hardness of the electroplated gold layer is greater than or equal to 90 HV, for example, 90 HV to 120 HV, and may further range from 95 HV to 120 HV. A time for performing heat treatment may be 0.5h, 1.2h, 1h, 1.5h, 2h, or the like. In some embodiments, after the electroplating, after heat treatment is performed at a temperature of 280°C for one hour, the hardness of the electroplated gold layer is greater than or equal to 95 HV, for example, 95 HV to 120 HV.

[0062] An embodiment of this application further provides a gold-electroplated part. The gold-electroplated part includes a substrate and an electroplated gold layer disposed on the substrate. The electroplated gold layer may be formed by using a cyanide electroplating solution containing an aurous cyanide salt. In some implementations, the electroplated gold layer is formed through electroplating using the foregoing cyanide electroplating solution in the embodiments of this application that includes an aurous cyanide salt, an oxalate, a lead-containing compound, a water-soluble polysaccharide substance, and an organic acid conductive medium, or is formed by using the foregoing gold electroplating method in the embodiments of this application.

[0063] In some implementations of this application, with reference to FIG. 3, a gold-electroplated part 300 includes a substrate 1 and an electroplated gold layer 6' disposed on the substrate 1. The electroplated gold layer 6' is specifically a gold bump 6', and is T-shaped and provided with steps. The substrate 1 is usually a semiconductor substrate, for example, a silicon substrate, a silicon-on-insulator substrate, or a germanium substrate. The gold-electroplated part 300 in this case may be referred to as a "semiconductor gold-electroplated part provided with a gold bump". As shown in FIG. 3, an electrode 2 and a passivation layer 3 that covers the electrode 2 and the substrate 1 are disposed on the substrate 1, the passivation layer 3 is provided with an opening 3a that can expose a part of the electrode 2, and the gold bump 6' includes an internal electroplated layer filled in the opening 3a and a surface electroplated layer deposited on the passivation layer 3. A thickness h' of the gold bump 6' may fall within a range of 7 µm to 11 µm. This is a common thickness of a gold bump in a semiconductor gold-electroplated part.

[0064] In an implementation of this application, a first surface 601' that is of the gold bump 6' and that is away from the substrate 1 is basically a plane, and flatness of the surface is relatively high. A height difference between a point that is on the first surface 601' of the gold bump 6' and that is farthest to the substrate 1 and a point that is on the first surface 601' and that is nearest to the substrate 1 may be less than or equal to 1.2 µm. The relatively small height difference may reflect that surface flatness of the first surface 601' that is of the gold bump 6' and that is away from the substrate 1 is relatively high. This can greatly increase an effective contact area during bonding with another substrate by using the electroplated gold layer 6', and increase stability of a bonding structure. In some implementations, the height difference may be less than or equal to 1.1 µm, less than or equal to 1.0 µm, or even less than or equal to 0.9 µm. In some cases, the height difference may be measured by using surface roughness Rz of the gold bump 6'. Rz represents a maximum height of a profile, and may be represented by a distance between a profile peak line and a profile valley line within a sampling length. In an implementation of this application, the surface roughness Rz of the gold bump 6' is less than or equal to 1.2 µm, or less than or equal to 1.1 µm, or less than or equal to 1.0 µm, or even less than or equal to 0.9 µm.

[0065] In an implementation of this application, after heat treatment is performed at a relatively high temperature of 280°C for one hour, hardness of the gold bump 6' may still fall within a range of 90 HV to 120 HV, or even fall within a range of 95 HV to 120 HV. The gold bump 6' with a thickness of 7 µm to 11 µm can have both high toughness and high hardness after heat treatment. In a case in which a horizontal size and a spacing of the gold bump 6' are relatively small, the gold bump 6' with relatively high hardness can ensure that in a process of thermal compression bonding between a chip provided with the gold bump 6' and a substrate, the gold bump 6' is not easily deformed to cause a connection between adjacent gold bumps and short circuiting of a line.

[0066] When the thickness of the gold bump 6' falls within a range of 7 µm to 11 µm, in this application, surface roughness Ra of the first surface 601' that is of the gold bump 6' and that is away from the substrate 1 falls within a range of 60 nm to 100 nm, for example, 65 nm, 70 nm, 72 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, or 98 nm. In some implementations, Ra falls within a range of 70 nm to 95 nm, and may further fall within a range of 71 nm to 95 nm. Appropriately high Ra facilitates subsequent alignment, bonding, and the like between a substrate and a gold bump. Ra represents an arithmetic average deviation of the profile, and is represented by an arithmetic average value of absolute values of profile offsets within the sampling length L.

[0067] The substrate 1 may be a semiconductor substrate, for example, a silicon substrate, a silicon-on-insulator substrate, or a germanium substrate. The electrode 2 is usually an aluminum (Al) electrode, and is usually formed on a side that is of the substrate 1 and on which a circuit layer is formed. The passivation layer 3 is usually an insulation dielectric material such as SiO 2 and silicon nitride.

[0068] In an implementation of this application, a lower metal layer 4 is further disposed between the passivation layer 3 and the electroplated gold layer 6'. The lower metal layer 4 may fill only the bottom of the opening 3a, or may cover both the passivation layer 3 and the electrode 2 exposed from the opening 3a of the passivation layer 3, as shown in FIG. 3. Due to the presence of the lower metal layer 4, smooth electroplating of the electroplated gold layer 6' on the substrate 1 can be ensured. The lower metal layer 4 may include a TiW layer and a gold seed layer that are stacked, and the TiW layer is close to the electrode 2. Due to the presence of the TiW layer, bonding force between the electrode 2 and the gold seed layer can be increased.

[0069] In addition, a plurality of electrodes 2 that are distributed at intervals may be disposed on the substrate 1. Correspondingly, the substrate 1 is also provided with a plurality of gold bumps 6' that are distributed at intervals, to ensure electrical interconnection between the electrodes 2 and conductive parts on another substrate.

[0070] In some other implementations of this application, the electroplated gold layer on the gold-electroplated part may not be a gold bump provided with a step, and may be specifically an electroplated gold layer without a step. In this case, a surface that is of the electroplated gold layer and that is close to the substrate is not a step surface, but a flat surface.

[0071] When the thickness of the electroplated gold layer ranges from 7 µm to 11 µm, the surface roughness Ra may also fall within a range of 60 nm to 100 nm. For example, the surface roughness Ra is specifically 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, or 95 nm. In some implementations, Ra may fall within a range of 70 nm to 95 nm. The hardness of the electroplated gold layer falls within a range of 90 HV to 120 HV. Particularly, after heat treatment is performed at a temperature ranging from 260°C to 300°C, the hardness of the electroplated gold layer is still greater than or equal to 90 HV, for example, 90 HV to 120 HV, and may further range from 95 HV to 120 HV. The electroplated gold layer has both relatively high toughness and hardness, and has a good application prospect.

[0072] An embodiment of this application further provides an electronic device provided with the foregoing gold-electroplated part.

[0073] In this application, the term "and / or" describes an association relationship between associated objects and may indicate that three relationships may exist. For example, A and / or B may indicate the following cases: Only A exists, both A and B exist, and only B exists, where A and B may be singular or plural. The character " / " generally indicates an "or" relationship between the associated objects.

[0074] In this application, "at least one" means one or more, and "a plurality of" means more than or equal to two. "At least one of the following items (pieces / types)" or a similar expression thereof means any combination of these items, including any combination of singular items (pieces) or plural items (pieces). For example, "at least one item (piece) of a, b, or c" or "at least one item (piece) of a, b, and c" may indicate: a, b, c, a-b (namely, a and b), a-c, b-c, or a-b-c, where a, b, and c each may be singular or plural.

[0075] The following further describes the technical solutions in the embodiments of this application by using a plurality of embodiments.Embodiment 1

[0076] In a 2L beaker with 600 mL of deionized water, 65 g of hydroxyethylidene diphosphonic acid (HEDP) is first added, and then the solution is stirred. After the solution is completely dissolved, pH of the solution is adjusted to 6.0 by using a potassium hydroxide solution, and then 30 g of potassium oxalate and potassium aurous cyanide with gold element content of 8 g are added. After the solution is fully dissolved, lead acetate with lead element content of 10 mg and 5 g of α-cyclodextrin are added. After the mixture is completely dissolved, a volume of the mixture is adjusted to 1 L, and a pH value of the mixture is adjusted to 6.0, to obtain a required gold electroplating solution.Comparative Example 1

[0077] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "65 g of HEDP" is replaced with "65 g of monopotassium phosphate".Embodiment 2

[0078] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "5 g of α-cyclodextrin" is replaced with "0.1 g of β-cyclodextrin".Embodiment 3

[0079] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "10 mg of lead acetate" is replaced with "5 mg of lead acetate", and "5 g of α-cyclodextrin" is replaced with "0.1 g of dextrin".Embodiment 4

[0080] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "10 mg of lead acetate" is replaced with "5 mg of lead acetate", and "5 g of α-cyclodextrin" is replaced with "5 g of dextrin".Embodiment 5

[0081] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "10 mg of lead acetate" is replaced with "5 mg of lead acetate", and "5 g of α-cyclodextrin" is replaced with "5 g of β-cyclodextrin".Embodiment 6

[0082] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "10 mg of lead acetate" is replaced with "5 mg of lead acetate", and "5 g of α-cyclodextrin" is replaced with "0.1 g of α-cyclodextrin".Embodiment 7

[0083] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "65 g of HEDP" is replaced with "65 g of amino trimethylene phosphonic acid (ATMP)".Embodiment 8

[0084] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "65 g of HEDP" is replaced with "65 g of amino trimethylene phosphonic acid (ATMP)", "10 mg of lead acetate" is replaced with "5 mg of lead acetate", and "5 g of α-cyclodextrin" is replaced with "0.1 g of α-cyclodextrin".Embodiment 9

[0085] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 1 in that: "65 g of HEDP" is replaced with "65 g of amino trimethylene phosphonic acid (ATMP)", "10 mg of lead acetate" is replaced with "5 mg of lead acetate", and "5 g of α-cyclodextrin" is replaced with "1 g of dextran".Embodiment 10

[0086] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 7 in that: "65 g of ATMP" is replaced with "30 g of ATMP".Embodiment 11

[0087] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 7 in that: "65 g of ATMP" is replaced with "10 g of ATMP" .Embodiment 12

[0088] A gold electroplating solution is provided, and the gold electroplating solution differs from the gold electroplating solution in Embodiment 7 in that: "65 g of ATMP" is replaced with "90 g of ATMP".

[0089] To reflect precipitation efficiency of the electroplating solution in this embodiment of this application and hardness of the obtained electroplated gold layer, each of the electroplating solutions in the embodiments and the comparative example is placed in a Yamamoto vertical electroplating tank, a temperature of the electroplating solution is controlled to be maintained at 40°C, and electroplating is performed at a current density of 0.5 ASD for 32 min with a platinum-coated titanium plate as an anode and a fresh unpatterned gold-electroplated silicon wafer as a cathode, to obtain a gold-electroplated part. After the electroplating is completed, precipitation efficiency of each electroplating solution is calculated. Results are compiled in Table 1. In addition, hardness, before heat treatment, of electroplated layers formed on unpatterned gold-electroplated silicon wafers and hardness of the electroplated layers after heat treatment at 280°C for 30 min are tested by using a Vickers hardness tester. Results are compiled in Table 1. The precipitation efficiency of the electroplating solution may be measured by using a gravimetric method, after electroplating is completed. The parameter is specifically a ratio of a weight of gold obtained through electroplating to a theoretical weight of monovalent gold to which total electric charge that passes through during electroplating is converted. During the test of the hardness using the Vickers hardness tester, a load of 10 gf is applied to hold an indenter on a surface of the electroplated layer for 10s, to test the hardness of the electroplated layer.

[0090] It is learned through the test that precipitation efficiency of the electroplating solution in Embodiment 1 is 97.5%. An obtained electroplated gold layer is matte and is uniform in color (refer to FIG. 4 for details). Hardness of the electroplated gold layer obtained in Embodiment 1 is 124 HV before heat treatment, and hardness of the electroplated gold layer is 106 HV after the heat treatment. After heat treatment is performed at a temperature of 280°C for one hour, the hardness of the electroplated gold layer can still be as high as 106 HV. This can meet a technical requirement of the semiconductor field for a gold bump with high hardness (90 HV to 120 HV). When concentrations of a gold cyanide source, potassium oxalate, water-soluble polysaccharide, and lead compound in the electroplating solution in Comparative Example 1 are the same as concentrations of a gold cyanide source, potassium oxalate, water-soluble polysaccharide, and lead compound in the electroplating solution in Embodiment 1 of this application, in Comparative Example 1, precipitation efficiency of the electroplating solution with monopotassium phosphate as a conductive salt is lower than the precipitation efficiency of the electroplating solution in Embodiment 1, and an obtained electroplated gold layer is matte and is not uniform in color (refer to FIG. 4 for details). Hardness of the electroplated gold layer is only 81 HV after heat treatment is performed at 280°C for one hour. It can be learned that the electroplating solution in Comparative Example 1 is not suitable for making a high-hardness gold bump.

[0091] FIG. 4 compiles microscopic profile images of gold bumps obtained through electroplating on patterned silicon wafers using the electroplating solution in Embodiment 1 and the electroplating solution in Comparative Example 1 respectively, where magnifications are 500x. (a) in FIG. 4 is the image of the gold bump obtained by using the electroplating solution in Embodiment 1, and (b) in FIG. 4 is the image of the gold bump obtained by using the electroplating solution in Comparative Example 1. It can be learned from FIG. 4 that, the electroplated gold layer formed through electroplating using the electroplating solution with an organic phosphonic acid as a conductive medium in Embodiment 1 of this application has a relatively uniform appearance with almost no noticeably protruding particles. In contrast, the electroplated layer formed through electroplating using the electroplating solution with monopotassium phosphate as a conductive salt in Comparative Example 1 has an obviously non-uniform appearance with noticeably protruding gold nodules in some areas. In addition, each image in FIG. 4 is divided into a plurality of rectangular areas with dimensions of 50 µm x 50 µm, and there are more than three gold nodules in each of the plurality of rectangular areas.

[0092] To evaluate a leveling capability of the electroplating solution and improvement of the electroplating solution on the appearance of the electroplated layer in this embodiment of this application, a patterned silicon wafer is designed based on an actual requirement. The patterned silicon wafer is a patterned silicon wafer with an Au seed layer deposited on a surface. A specific structure of the patterned silicon wafer may be shown in (A) in FIG. 1. A surface cross-sectional structure of a middle part of the patterned silicon wafer from bottom to top is Si / SiO 2 / Al / TiW / Au. In other words, the substrate 1 is a silicon substrate with SiO 2 , the electrode 2 is Al, and the lower metal layer 4 is a TiW layer and an Au seed layer that are stacked. A negative photoresist PR NR9-8000 (Futurrex) is used to form a bump opening. Dimensions of the bump opening are 80 µm (length) x 20 µm (width w) x 15 µm (depth h). A passivation layer with a height of 1.2 µm is designed on the aluminum electrode, and a width w 1 of an opening, in the passivation layer, that can expose the aluminum electrode is 12 µm. Gold electroplating is performed in the bump opening by using each electroplating solution. A temperature of the electroplating is 40°C, a current density of the electroplating is 0.5 ASD, and duration of the electroplating is 32 min. After the electroplating is completed, the photoresist is removed by using an N-methylpyrrolidinone (NMP) solvent, to obtain a gold bump filled in the bump opening, and a shape and a height of the gold bump are measured by using VK-X3100.

[0093] FIG. 5 is a cross-sectional view of a patterned silicon wafer provided with a gold bump and formed through electroplating using the electroplating solution in Embodiment 1 of this application. It can be learned from FIG. 5 that a shape of the obtained gold bump is relatively regular, and no phenomenon of skipping plating or infiltration plating occurs.

[0094] FIG. 6 compiles a top-view microscopic image (a in FIG. 6) of the patterned silicon wafer provided with the gold bump and obtained by using the electroplating solution in Embodiment 1, a top-view profile image (b in FIG. 6) of the gold bump, a top-view microscopic image (c in FIG. 6) of a patterned silicon wafer provided with a gold bump and obtained by using the electroplating solution in Comparative Example 1, and a top-view profile image (d in FIG. 6) of the gold bump, where magnifications in FIG. 6 are 500x.

[0095] It can also be learned from FIG. 6 that, a shape of the gold bump obtained through electroplating is relatively regular, no phenomenon of skipping plating or infiltration plating occurs, and no photoresist dissolution or breakage occurs (a location at which the photoresist exists corresponds to gaps between long strip-shaped gold bumps in a and c in FIG. 6). A height of the gold bump prepared by using the electroplating solution in Embodiment 1 is 9.681 µm, and a height of the gold bump prepared by using the electroplating solution in Comparative Example 1 is 10.396 µm. In addition, by measuring a maximum height difference of a front end of a gold bump (that is, a height difference between a point closest to the aluminum electrode and a point farthest to the aluminum electrode on a surface that is of the gold bump and that is away from a side of the electrode, that is, a height difference between two points a and b shown in (B) in FIG. 1), it can be learned that a height difference of a front end of the gold bump obtained by using the electroplating solution in Comparative Example 1 is approximately 1.31 µm, while a height difference of a front end of the gold bump obtained by using the electroplating solution in Embodiment 1 is only approximately 0.90 µm. This indicates that in this embodiment of this application, the electroplating solution in which an organic phosphonic acid is used to replace inorganic phosphate has relatively good leveling performance. High flatness of the front end of the gold bump can greatly increase an effective contact area between the gold bump and a substrate during thermal compression bonding, thereby ensuring a relatively high bonding success rate and a more reliable bonding structure. Table 1Precipitation efficiency (%) of electroplating solutionsHardness (HV) of electroplated layers before heat treatmentHardness (HV) of the electroplated layers after heat treatmentRa (nm) of gold bumpsRz (µm) of the gold bumpsEmbodiment 197.5124106780.90Embodiment 295.8121100810.95Embodiment 396.611097720.87Embodiment 496.411398710.82Embodiment 596.6129112810.91Embodiment 696.611595790.79Embodiment 797.5132118830.94Embodiment 897.511296820.89Embodiment 997.511799870.96Embodiment 1097.1123101740.99Embodiment 1196.111999811.02Embodiment 1297.2117103800.86Comparative Example 195.810281531.31Note: Heat treatment in Table 1 is performed at 280°C for one hour.

[0096] Table 1 further compiles data such as precipitation efficiency of electroplating solutions in other embodiments of this application when electroplating is performed on unpatterned silicon wafers by using the electroplating solutions, and hardness of electroplated layers before and after heat treatment. It can be learned from a comparison between Embodiment 1 and Embodiment 7 that, when concentrations of other components in the electroplating solutions are the same, concentrations of added organic phosphonic acids are the same, but types of the organic phosphonic acids are different, the electroplating solutions also have high precipitation efficiency, and hardness of electroplated layers after heat treatment is also high. Embodiment 6 and Embodiment 8 are also different in only types of added organic phosphonic acids in the electroplating solutions, so results in the two embodiments are also relatively close to each other. In addition, it can be learned from a comparison between Embodiment 3 and Embodiment 4 that, when types of water-soluble polysaccharides in the electroplating solutions are the same but amounts of the water-soluble polysaccharides are different, if concentrations of the water-soluble polysaccharides increase in a range of 0.1 g / L to 5 g / L, this is relatively helpful for enhancing hardness of electroplated layers. Particularly, it can be learned from a comparison between Embodiment 7 and Embodiments 10 to 12 that, when mass of a same type of organic phosphonic acid added in the electroplating solutions is different, and concentrations of organic acid conductive media in the electroplating solutions in terms of organic phosphonic acids are allowed to be greater than 30 g / L, for example, in a range of 55 g / L to 90 g / L, the electroplating solutions have appropriate viscosity and relatively high precipitation effects, and obtained gold bumps have appropriate hardness and good surface flatness.

[0097] It should be noted that, in Table 1, after heat treatment is performed at 280°C for one hour, hardness of each of electroplated layers obtained by using the electroplating solutions in the embodiments of this application may fall within a range of 95 HV to 120 HV, and may further fall within a range of 96 HV to 120 HV. Because hardness of an electroplated layer usually decreases with an increase of a heat treatment temperature, it may be understood that, for the electroplated layers obtained in the embodiments of this application, if heat treatment is performed at a relatively low temperature (for example, heat treatment is performed at 250°C for 0.5 hour), hardness of each electroplated layer after the heat treatment may definitely be greater than 95 HV, for example, may fall within a range of 100 HV to 120 HV.

[0098] In addition, gold bumps formed on the patterned silicon wafers by using the electroplating solutions in Embodiments 2 to 12 of this application also have a similar effect as that in Embodiment 1. For example, a shape of the gold bump is regular, and no skipping plating or infiltration plating occurs. A surface that is of the gold bump and that is away from the silicon substrate has a uniform appearance, and a maximum height difference (corresponding to Rz in Table 1) on the surface that is of the gold bump and that is away from the silicon substrate is also relatively low, and is basically less than 1.1 µm. This indicates that the surface of the gold bump is relatively flat, facilitating bonding between the patterned silicon wafer and a routing substrate, and the like.

Claims

1. A gold electroplating solution, wherein the electroplating solution comprises an aurous cyanide salt serving as a gold source, an oxalate, a lead-containing compound, a water-soluble polysaccharide substance, and an organic acid conductive medium, wherein the organic acid conductive medium comprises an organic phosphonic acid or a salt of the organic phosphonic acid.

2. The electroplating solution according to claim 1, wherein an electrical conductivity of the electroplating solution at a room temperature ranges from 40 mS / cm to 90 mS / cm.

3. The electroplating solution according to claim 1 or 2, wherein the electroplating solution does not comprise an inorganic acid conductive salt.

4. The electroplating solution according to any one of claims 1 to 3, wherein at least one of hydroxyethylidene diphosphonic acid, amino trimethylene phosphonic acid, and ethylenediamine tetramethylenephosphonic acid is selected as the organic phosphonic acid.

5. The electroplating solution according to any one of claims 1 to 4, wherein in the electroplating solution, a concentration of the organic acid conductive medium in terms of organic phosphonic acids ranges from 10 g / L to 100 g / L.

6. The electroplating solution according to any one of claims 1 to 5, wherein in the electroplating solution, the concentration of the organic acid conductive medium in terms of organic phosphonic acids ranges from 55 g / L to 95 g / L.

7. The electroplating solution according to any one of claims 1 to 6, wherein a concentration of the water-soluble polysaccharide substance in the electroplating solution ranges from 0.1 g / L to 5 g / L.

8. The electroplating solution according to any one of claims 1 to 7, wherein the water-soluble polysaccharide substance comprises at least one of dextrin, α-cyclodextrin, β-cyclodextrin, or dextran.

9. The electroplating solution according to any one of claims 1 to 8, wherein a ratio of mass of the organic acid conductive medium in terms of organic phosphonic acids to mass of the water-soluble polysaccharide substance is (9-900): 1.

10. The electroplating solution according to any one of claims 1 to 9, wherein the aurous cyanide salt comprises at least one of potassium aurous cyanide, sodium aurous cyanide, and ammonium aurous cyanide.

11. The electroplating solution according to any one of claims 1 to 10, wherein an amount of the aurous cyanide salt causes a concentration of gold ions ranging from 1 g / L to 15 g / L in the electroplating solution.

12. The electroplating solution according to any one of claims 1 to 11, wherein at least one of potassium oxalate, sodium oxalate, and ammonium oxalate is selected as the oxalate; and a concentration of the oxalate in the electroplating solution ranges from 5 g / L to 80 g / L.

13. The electroplating solution according to any one of claims 1 to 12, wherein at least one of lead acetate, lead nitrate, lead citrate, and lead sulfate is selected as the lead-containing compound; and in the electroplating solution, a concentration of the lead-containing compound in terms of lead elements ranges from 2 mg / L to 15 mg / L.

14. The electroplating solution according to any one of claims 1 to 13, wherein the electroplating solution further comprises a pH additive.

15. The electroplating solution according to any one of claims 1 to 14, wherein pH of the electroplating solution ranges from 5 to 7.

16. An application of the electroplating solution according to any one of claims 1 to 15 in gold electroplating.

17. The application according to claim 16, wherein the application comprises an application in preparing a semiconductor gold-electroplated part provided with a gold bump.

18. A gold electroplating method, comprising: causing a to-be-electroplated part to be in contact with the electroplating solution according to any one of claims 1 to 15; and applying a current to the to-be-electroplated part to perform electroplating, to form an electroplated gold layer on the to-be-electroplated part.

19. The gold electroplating method according to claim 18, wherein a temperature of the electroplating ranges from 30°C to 50°C; and / or a current density of the electroplating ranges from 0.1 A / dm2 to 1.0 A / dm2.

20. The gold electroplating method according to claim 18 or 19, wherein after the electroplating, the method further comprises: performing heat treatment at a temperature ranging from 260°C to 300°C; and hardness of the electroplated gold layer ranges from 90 HV to 120 HV after the heat treatment.

21. A gold-electroplated part, comprising a substrate and an electroplated gold layer disposed on the substrate, wherein the electroplated gold layer is formed through electroplating using the electroplating solution according to any one of claims 1 to 15, or is formed by using the gold electroplating method according to any one of claims 18 to 20.

22. The gold-electroplated part according to claim 21, wherein surface roughness Ra of the electroplated gold layer falls within a range of 60 nm to 100 nm when a thickness of the electroplated gold layer ranges from 7 µm to 11 µm.

23. The gold-electroplated part according to claim 21 or 22, wherein the electroplated gold layer is a gold bump, and the substrate is a semiconductor substrate.

24. The gold-electroplated part according to claim 23, wherein hardness of the gold bump falls within a range of 90 HV to 120 HV when a thickness of the gold bump ranges from 7 µm to 11 µm; and a height difference between a point farthest to the substrate and a point nearest to the substrate on a surface that is of the gold bump and that is away from the substrate is less than 1.2 µm.

25. A gold-electroplated part, comprising a substrate and an electroplated gold layer disposed on the substrate, wherein the electroplated gold layer is formed through electroplating using an electroplating solution containing an aurous cyanide salt, and surface roughness Ra of the electroplated gold layer falls within a range of 60 nm to 100 nm when a thickness of the electroplated gold layer ranges from 7 µm to 11 µm.

26. The gold-electroplated part according to claim 25, wherein hardness of the electroplated gold layer falls within a range of 90 HV to 120 HV.

27. The gold-electroplated part according to claim 25 or 26, wherein the electroplating solution further comprises an oxalate, a lead-containing compound, a water-soluble polysaccharide substance, and an organic acid conductive medium, wherein the organic acid conductive medium comprises an organic phosphonic acid or a salt of the organic phosphonic acid.

28. An electronic device, wherein the electronic device comprises the gold-electroplated part according to any one of claims 21 to 24, or the gold-electroplated part according to any one of claims 25 to 27.

Images