TW201331427A - Non-cyanide gold electroplating bath for gold bump formation and method for forming gold bump - Google Patents

Abstract

This invention provides a non-cyanide gold electroplating bath for gold bump formation having the bump hardness and shape suitable for electrode joining with a substrate electrode, and a method for forming a gold pump using the gold plating bath. The non-cyanide gold electroplating bath for the gold bump formation of this invention is characterized by comprising: an alkali salt of gold sulfite or ammonium gold sulfite; a conductive salt; a crystal stabilizer; a crystal conditioner; a buffer; and a brightening agent. The content of the alkali salt of gold sulfite or ammonium gold sulfite is 1 to 20 g/L as a gold concentration, the conductive salt is sodium sulfite with its content of 5 to 150 g/L, and the content of the brightening agent is 0.5 to 100 mmol/L. As the brightening agent, one or more kinds of compounds selected from a sulfoxide and/or sulfone are preferably used.

Description

Non-cyanide electrolytic gold plating bath for gold bump formation and gold bump forming method

The present invention relates to a non-cyanide electrolytic gold plating bath for forming a gold bump used for forming a semiconductor wafer, and a gold bump forming method using the non-cyanide electrolytic gold plating bath for forming a gold bump.

When a semiconductor wafer is provided on a printed wiring board, a glass substrate or the like, the gold bump formed on the integrated circuit on the semiconductor wafer is bonded to the electrode connected to the substrate electrode formed on the substrate. Method (refer to Patent Documents 1 and 2).

Specific electrode bonding methods are known as line bonding or waferless methods. The wire bonding method refers to a bonding method in which a gold bump and a substrate electrode are bonded using a line. The waferless method refers to a bonding method in which a negative semiconductor wafer is mounted on a substrate, and the gold bumps and the substrate electrodes are joined by an anisotropic conductive adhesive.

When the substrate is a film-shaped flexible substrate used for a package method such as a TCP (Tape carrier package) or a COF (Chip on Film), bonding of the gold bumps to the substrate electrodes is mainly performed by a wafer-free method.

In the waferless method, a tin-plated layer or a gold-plated layer formed on a substrate electrode and a gold bump formed on a semiconductor wafer are hot-pressed and eutectic bonded using an anisotropic conductive adhesive. The anisotropic conductive adhesive refers to an adhesive in which conductive particles coated with a Ni/Au plating layer on a resin particle are uniformly dispersed in a thermosetting resin such as an epoxy resin. Eutectic bonding refers to bonding of electrodes bonded to gold bumps by thermocompression or supersonic formation of eutectic.

In recent years, in order to simplify the manufacturing steps of a semiconductor package and to perform electrode bonding more reliably, most of the electrode bonding methods using a film-shaped anisotropic conductive adhesive have been used.

Fig. 1 is a cross-sectional view showing an example of a state in which a semiconductor wafer is provided on a printed wiring board.

In the printed wiring board 10, the substrate electrode 13 is formed on the surface of the hard substrate 11 on which the substrate wiring pattern 12 is formed.

The semiconductor wafer 9 is formed on one surface of the semiconductor wafer 1 to form a circuit layer 1'. On the surface on which the circuit layer 1' is formed, the Al electrode 2, the purification layer 3, the TiW sputtering film 4, the Au sputtering film 5, and the gold bump 7' are laminated in this order. In the laminated structure, the gold bumps 7' are formed on the region where the Al electrode 2 is disposed, and are formed on the opposite side to the bonding surface of the gold bumps 7' and the Au sputtering film 5, and the printed wiring substrate 10 is formed. The bonding surface 7'a of the substrate electrode 13.

In the first embodiment, the semiconductor wafer 9 is formed such that the bonding surface 7'a of the gold bumps 7' faces the printed wiring board 10 and is superposed on the printed wiring board 10. Then, the gold bumps 7 and the substrate electrodes 13 are electrode-bonded using the anisotropic conductive adhesive 20, and are provided on the printed wiring substrate 10. Between the semiconductor wafer 9 and the printed wiring board 10, the sealing material 14 is sealed.

When the semiconductor wafer 9 described above is provided on the printed wiring board 10, the flatness of the bonding surface 7'a of the gold bumps 7' and the substrate electrodes 13 and the hardness of the gold bumps 7' are adjusted.

<Ensure the flatness of the joint surface>

When the electrode bonding is performed using the conductive adhesive 20, the gold bump 7' and The bonding force of the substrate electrode 13 is stronger as the bonding area (the region where the conductive particles are present) when the bonding surface 7'a of the gold bump 7' is bonded to the substrate electrode 13 is larger. However, the joint surface 7'a of the conventional gold bump 7' is not flat, and a shape capable of securing a sufficient joint area cannot be formed.

Fig. 2 is a partially enlarged cross-sectional view showing a portion of the semiconductor wafer 9 on which the conventional gold bump 7' is formed. Fig. 2 is a view showing that the expanded semiconductor wafer is opposite to the state shown in Fig. 1, that is, the semiconductor wafer 1 is below, and the bonding surface 7'a of the gold bump 7' is above, forming a portion of the gold bump. The symbols used in Fig. 2 are common to the symbols in Fig. 1.

The second portion of the joint surface 7'a is formed in a central portion from the Au sputtering film 5 side and protrudes from the peripheral portion. In the protruding shape shown in Fig. 2, the gold bump 7' is in contact with the substrate electrode 13 only at the most distal end portion of the protruding shape.

Further, although not shown in the drawing, the joint surface 7'a is formed to collapse toward the Au sputtering film 5 side, and the peripheral portion of the gold bump 7' is formed. At this time, the conductive particles in the anisotropic conductive adhesive 20 easily fall into the collapsed portion or the missing portion of the joint surface 7'a, and the conductive particles are offset by a portion of the joint surface 7'a.

As described above, when the joint surface 7'a of the gold bump 7' is not flat, the joint surface 7'a cannot be fully utilized for electrode bonding. In other words, the bonding area of the bonding surface 7'a of the conventional gold bump 7' and the substrate electrode 13 when the electrode is bonded to the electrode is small. Therefore, the bonding force between the gold bumps 7' and the substrate electrode 13 is weakened, and there is a problem of electrical defects such as disconnection or poor bonding in the subsequent assembly step.

In order to solve the above problem, it is sought to make the joint surface 7'a of the gold bump 7' The flat shape allows the conductive particles to be uniformly distributed over the entire surface of the joint surface 7'a, ensuring that the joint area with the substrate electrode is maximized.

In recent years, in addition to the increase in the number of electrodes due to the high function of the liquid crystal, the IC chip has been miniaturized by reducing the package cost. Therefore, in forming gold bumps, it is also required to narrow the arrangement pitch and reduce the size of the IC wafer. When electrode bonding is performed using gold bumps corresponding to a narrow pitch, in order to maximize the bonding surface of the gold bumps for electrode bonding, it is desirable to make the bonding surface flat and to secure a sufficient bonding area.

<hardness adjustment of gold bumps>

When the electrode bonding is performed using the anisotropic conductive adhesive 20, when the hardness of the gold bump 7' is too low for the hardness of the conductive particles in the anisotropic conductive adhesive 20, the conductive particles are buried in the gold bump during hot press melting. In block 7'. At this time, at the time of electrode bonding, the conductive particles are not thermally pressed between the gold bumps 7' and the substrate electrodes 13, and the electrode bonding between the gold bumps 7' and the substrate electrodes 13 is insufficient. When the hardness of the gold bump 7' is too high for the conductive particles in the anisotropic conductive adhesive 20, the conductive particles are crushed on the gold bump 7' during hot press melting. At this time, the gold bump 7' is not electrode-bonded to the substrate electrode 13.

When the eutectic bonding is performed, when the hardness of the gold bump 7' is too high for the hardness of the metal forming the eutectic, the gold bump 7' cannot be buried in the target metal, and a sufficient eutectic phenomenon cannot be formed. At this time, an electrical defect may occur due to a broken wire or poor joint.

Therefore, the hardness of the gold bump 7' must be different depending on the electrode used for bonding. The hardness of the conductive particles in the conductive adhesive or the metal to be eutectic with the gold bumps is formed to have an appropriate hardness.

The eutectic bonding is bonded to the electrode using an anisotropic conductive adhesive, and the hardness required for the gold bump is different. The appropriate hardness of the gold bumps is 50 to 120 HV after heat treatment using an anisotropic conductive adhesive for electrode bonding, and 35 to 60 HV after heat treatment for eutectic bonding. The width of the appropriate hardness depends on the type of the conductive particles or the hardness of the metal to be treated, and the appropriate hardness varies depending on the conductive particles or the target metal.

Therefore, a method of simply forming the hardness of the gold bumps corresponding to the appropriately selected conductive particles or the target metal is preferable.

[Practical Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-62584

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-57631

An object of the present invention is to provide a non-cyanide type for gold bump formation suitable for forming a gold bump having a sufficient bonding force with a substrate electrode when electrode bonding is performed by a common bonding or an anisotropic conductive adhesive. An electrolytic gold plating bath and a gold bump forming method using the non-cyanide electrolytic gold plating bath for forming the gold bump.

A first aspect of the present invention relates to a non-cyanide electrolytic gold plating bath for forming gold bumps, which comprises gold alkali sulfite or gold ammonium sulfite. a conductive salt, a crystallizing stabilizer, a crystal modifier, a buffering agent and a glossing agent, and the content of the aforementioned gold sulfite salt or gold ammonium sulfite is 1 to 20 g/L, and the conductive salt is sodium sulfite. The content is 5 to 150 g/L, and the content of the glossing agent is 0.5 to 100 mmol/L.

According to a second aspect of the present invention, there is provided a non-cyanide electrolytic gold plating bath for forming a gold bump according to the first aspect of the present invention, wherein the glossing agent is one or more compounds selected from the group consisting of arsenic and/or cerium.

According to a third aspect of the present invention, there is provided a non-cyanide electrolytic gold plating bath for forming a gold bump according to the first aspect or the second aspect of the present invention, wherein the glossing agent is selected from the group consisting of tetramethylene sulfoxide and propane sultone; 4-butane sultone, cyclobutyl hydrazine, 3-hydroxycyclobutyl hydrazine, 4,4-dioxy-1,4-oxathiocyclohexane, 3-cyclobutene oxime, 3-cyclobutenazole One or two or more compounds selected from the group consisting of -3-methyl carbonate and acesulfame potassium.

According to a fourth aspect of the present invention, the non-cyanide electrolytic gold plating bath for forming a gold bump according to any one of the first aspect to the third aspect, wherein the crystal modifier is selected from the group consisting of a T1 compound, a Pb compound, or an As compound. One or two or more compounds having a metal concentration of 0.1 to 100 mg/L.

According to a fifth aspect of the present invention, the non-cyanide electrolytic gold plating bath for forming a gold bump according to any one of the first aspect to the fourth aspect, wherein the crystal stabilizer is a water-soluble amine, and the content of the water-soluble amine is 1~12g/L.

According to a sixth aspect of the present invention, the non-cyanide electrolytic gold plating bath for forming a gold bump according to any one of the first aspect to the fifth aspect, wherein the crystal stabilizer is selected from the group consisting of 1,2-diaminoethane 1,2-diaminopropane or 1,6-diamine One or a combination of two or more kinds of hexane.

According to a seventh aspect of the present invention, there is provided a method of performing electrolytic gold plating on a patterned semiconductor wafer by using a non-cyanide electrolytic gold plating bath for forming a gold bump according to any one of the first to sixth aspects of the present invention. a step of electrolytic gold plating, and a heat treatment step of heat-treating the semiconductor wafer subjected to electrolytic gold plating at 150 to 400 ° C for 5 minutes or more, and forming a surface height difference of 2 μm or less after the electrolytic gold plating step, after the heat treatment step Gold bumps with a hardness of 35~120HV.

The gold bump formed by the non-cyanide electrolytic gold plating bath for forming a gold bump of the present invention has no uniform appearance such as spots or brownish brown on the plating film, and the joint surface with the substrate electrode is flat. Since the joint surface is flat, electrode bonding using an anisotropic conductive adhesive is used, and the conductive particles are uniformly distributed over the joint surface. Thereby, it becomes easy to ensure the joint area with the board|substrate electrode in the joint surface comprehensively. In particular, when a gold bump corresponding to a narrow pitch is formed, since the present invention can effectively secure the joint area, a sufficient joint force is generated.

The present invention can form a gold bump suitable for the electrode bonding of the anisotropic conductive adhesive and a gold bump suitable for the eutectic bonding by adjusting the content of the glossing agent in the gold plating bath.

In other words, the gold bump formed by the non-cyanide electrolytic plating bath for forming gold bumps of the present invention is bonded by electrode bonding using an anisotropic conductive adhesive by flattening the joint surface and adjusting an arbitrary hardness. At the time of the joint surface, the conductive particles can be thermally pressed in a state of being uniformly disposed. and The eutectic bonding can sufficiently form a eutectic. Therefore, with the gold bump formed by the present invention, a sufficient bonding force can be exerted between the substrate and the substrate electrode in any of the bonding methods, and the ratio of occurrence of disconnection or poor bonding is extremely low.

[In order to implement the invention] <Ingredients of non-cyanide electrolytic gold plating bath>

The components of the electrolytic gold plating bath of the present invention are described in the following (1) to (7). (1)~(6) are essential components.

(1) gold sulfite alkali salt, gold ammonium sulfite (gold source)

The present invention is not limited to the conventional gold sulfite salt as a gold source, and can be used. Conventional gold sulfite salts, such as sodium (I) sulfite, potassium (I) sulfite, and the like. These may be used alone or in combination of two or more.

The content of the gold sulfite salt or the gold ammonium sulfite in the non-cyanide electrolytic gold plating bath of the present invention is 1 to 20 g/L, preferably 8 to 15 g/L, in terms of gold concentration. When the content of the gold sulfite alkali salt or the gold ammonium sulfite is less than 1 g/L, the thickness of the plating film becomes uneven. When the content of the gold sulfite alkali salt or the gold ammonium sulfite exceeds 20 g/L, the physical properties of the plating film and the like do not cause a problem, but the production cost becomes high.

(2) Water-soluble ammonium (crystallizing stabilizer)

The present invention uses a water-soluble amine as a crystal stabilizer. The water-soluble amine used in the present invention has a carbon number of 2 or more, preferably a carbon number of 2 to 6. Diamine. The diamine having 2 to 6 carbon atoms is preferably 1,2-diaminoethane, 1,2-diaminopropane or 1,6-diaminohexane. These may be used alone or in combination of two or more.

The content of the water-soluble amine in the non-cyanide electrolytic gold plating bath of the present invention is 0.1 to 30 g/L, preferably 1 to 12 g/L. When the content of the water-soluble amine is less than 0.1 g/L, the critical current density is lowered, and it is a cause of forming brown-plated plating. When the content of the water-soluble amine exceeds 30 g/L, the stability of the gold salt is increased. Further, the plating film is too dense and has a problem in adhesion to the substrate electrode.

(3) Tl compound, Pb compound, As compound (crystal modifier)

In the present invention, a T1 compound, a Pb compound, and an As compound are used as a crystal modifier. The T1 compound used in the present invention is, for example, cesium formate, strontium malonate, barium sulfate, cesium nitrate or the like. The Pb compound is, for example, lead citrate, lead nitrate, lead alkane sulfonate or the like. As compounds such as arsenic trioxide and the like. These T1 compounds, Pb compounds, and As compounds may be used alone or in combination of two or more.

The content of the crystal modifier in the non-cyanide electrolytic gold plating bath of the present invention is 0.1 to 100 mg/L, preferably 0.5 to 50 mg/L, and more preferably 3 to 25 mg/L, in terms of metal concentration. This content can be appropriately set within the range not impairing the object of the present invention. When the amount of the crystal modifier is less than 0.1 mg/L, the plating bath is applied, the stability and durability of the plating bath are deteriorated, and the components of the plating bath are decomposed. The amount of crystallization modifier is more than At 100 mg/L, the plating periphery deteriorates and the plating film may cause appearance spots.

(4) sodium sulfite (conductive salt)

The present invention uses sodium sulfite as the conductive salt. The content of sodium sulfite in the non-cyanide electrolytic gold plating bath of the present invention is 5 to 150 g/L, preferably 10 to 80 g/L. When the content of sodium sulfite is less than 5 g/L, the surface of the gold bump is prevented from being flattened because the expansion of the gold bump shape cannot be sufficiently controlled. The deterioration of the periphery of the plating or the deterioration of the stability of the plating bath may cause decomposition of the constituent components of the plating bath. When the content of sodium sulfite exceeds 150 g/L, the critical current density is lowered to form a brownish-plated plating.

(5) Inorganic salts, carboxylic acids, hydroxycarboxylic acids (buffering agents)

The present invention is not limited to the conventional buffer used when electrolytic gold plating is used, and can be used. A known buffering agent is an organic acid (carboxylic acid, hydroxycarboxylic acid) salt such as a mineral acid salt such as phosphate or borate, a citrate, a phthalate or an ethylenediaminetetraacetate.

The content of the buffering agent in the non-cyanide electrolytic gold plating bath of the present invention is 1 to 30 g/L, preferably 2 to 15 g/L, and more preferably 2 to 10 g/L. When the content of the buffer is less than 1 g/L, the stability of the plating bath is deteriorated due to a decrease in the pH value, and the composition of the plating bath may be decomposed. When the content of the buffer exceeds 30 g/L, the critical current density is lowered and there is a case where the brown color is plated.

(6) Luminating agent

The present invention uses a glossing agent. The glossing agents used in the present invention are anthraquinone and/or hydrazine. The hydrazine and/or hydrazine is selected as a compound dissolved in water. The compound is, for example, a sulfonium such as tetramethylene hydrazine or a salt thereof, propane sultone, 1,4-butane sultone, cyclobutyl hydrazine, 3-hydroxycyclobutanthene, 4,4-dioxo- Anthracene and salts thereof of 1,4-oxathiane, 3-sulfene, methyl 3-sulfon-3-carboxylate, potassium acesulfame, and the like. These may be used alone or in combination of two or more.

The content of the glossing agent in the non-cyanide electrolytic gold plating bath of the present invention is from 0.5 to 150 mmol/L, preferably from 1 to 100 mmol/L.

The glossing agent can impart densification to the plating film and planarize the surface of the gold bump. Further, when the content of the glossing agent is less than 0.5 mmol/L, the surface of the gold bump cannot be made flat. When the content of the glossing agent exceeds 200 mmol/L, the glossing agent is not dissolved in the plating bath, the critical current density is lowered, and brown-plated plating is formed, and the plating film is too dense, resulting in poor adhesion to the substrate electrode. Good question.

The glossing agent can also impart hardness to the gold bump after heat treatment. The hardness of the formed gold bump after heat treatment corresponds to the content of the glossing agent in the non-cyanide electrolytic gold plating bath. When the content of the glossing agent is large, hard gold bumps are formed, and soft gold bumps are formed in a small amount.

The state in which the amount of gold in the gold plating bath is completely plated is referred to as "one turn". The gold plating bath of the present invention can be used for more than two times by supplementing and managing the gold source and other components constituting the gold plating bath. Therefore, when the gold plating bath of the present invention is used to supplement the glossing agent, the amount of the glossing agent is adjusted to Within the above range, the hardness of the gold bump after heat treatment can be formed to be 35 to 120 HV.

(7) Other ingredients

In addition to the essential components described in (1) to (6), a suitable pH adjusting agent may be used. The pH adjuster is, for example, sulfuric acid, sulfurous acid, phosphoric acid or the like of an acid, and is used as an alkali sodium hydroxide or ammonium water. The pH adjusting agent can be used without departing from the scope of the invention.

<Gold bump formation method>

The present invention is carried out by a conventional plating operation to form gold bumps on a semiconductor wafer. A plating operation example will be described based on Fig. 3 as a reference.

Fig. 3 is a partially enlarged cross-sectional view showing a portion of a gold bump formed by using the non-cyanide electrolytic gold plating bath of the present invention in a semiconductor wafer. In the following description, the "non-cyanide electrolytic gold plating bath" is simply referred to as "gold plating bath".

(1) Lamination step

An Al electrode 2 is formed on the surface of the semiconductor wafer 1 on which the circuit layer 1' is formed. The coated circuit layer 1' and the purified film 3 of the Al electrode 2 are formed on the surface of the circuit layer 1'. The opening portion 3a is provided at a position where the partial Al electrode 2 is exposed on the purification film 3.

The TiW sputter film 4 is formed on the surface of the purification film 3. The TiW sputtering film 4 is coated with the purification film 3 and the Al electrode 2 exposed from the opening 3a of the purification film 3.

The Au sputtering film 5 is formed on the surface of the TiW sputtering film 4. The TiW sputter film 4 and the Au sputter film 5 constitute an Under Bump Metal (UBM) layer 6.

The photoresist film 8 is formed on the surface of the UBM layer 6 and subjected to a mask process. An opening 8a for exposing the partial Au sputtering film 5 is provided on the photoresist film 8. The opening portion 8a of the photoresist film 8 is provided in a position region of the Al electrode 2 in the lower layer of the photoresist film 8. As the material of the photoresist film 8, a novolac-based positive photoresist or the like can be used.

(2) Electroplating step

The semiconductor wafer 1 having the laminated structure is used as a plating material, and electrolytic gold plating is performed using the non-cyanide electrolytic gold plating bath of the present invention. The gold plating bath of the present invention is not limited to the material to be plated as long as the material is metalized and has high conductivity. In particular, it is preferable to form a gold bump on a circuit of a germanium wafer patterned with a novolac-based positive photoresist on a photoresist film 8, or to form a gold bump on a circuit of a compound wafer such as a GaAs wafer.

Since the gold plating bath of the present invention contains a glossing agent, the plating film can be densified, and the bonding surface 7a of the gold bumps 7 and the substrate electrodes can be made flat.

The plating temperature is 40 to 70 ° C, preferably 50 to 65 ° C. When the plating temperature is outside the range of 40 to 70 ° C, the plating film is not easily precipitated. In addition, the gold plating bath becomes unstable, which may cause decomposition of the constituent components of the gold plating bath.

The current density at the time of plating varies depending on the composition and temperature of the gold plating bath, but it is 2.0 A/dm ² or less under the conditions of a gold concentration of 8 to 15 g/L and a plating temperature of 60 ° C. Preferably, it is 0.2 to 1.2 A/dm ² . When the current density is outside the range, the workability is poor, and the appearance of the plating film or the characteristics of the plating film is abnormal. The gold-plated bath became significantly unstable and the composition of the gold-plated bath also decomposed.

The pH of the gold plating bath is 7.0 or more, preferably 7.2 to 10.0. When the pH of the gold plating bath is less than 7.0, the gold plating bath becomes significantly unstable, and the composition of the gold plating bath is decomposed. When the pH of the gold plating bath is 10.0 or more, the photoresist film 8 is dissolved and the desired gold bumps cannot be formed.

After electrolytic gold plating, the photoresist film 8 of the semiconductor wafer 1 is dissolved and removed by a solvent. By removing the photoresist film 8, the UBM layer 6 which is not covered by the gold bumps 7 is exposed. The exposed UBM layer 6 is also removed by etching or the like. Thereby, the purification film 3 is exposed in a region where the gold bumps 7 are not covered. The UBM layer 6 covered with the gold bumps 7 is not removed by this step, and the laminated structure is maintained.

(3) Heat treatment step

After the UBM layer 6 and the photoresist film 8 are removed, the gold bumps 7 are heat-treated at 150 to 400 ° C (preferably 200 to 300 ° C). The heat treatment time is 5 minutes or longer, preferably 30 to 60 minutes. A heat treatment oven or the like is used for the heat treatment. Since the refining oven can maintain the time required for the heat treatment and the inside of the reaction chamber at a set temperature for a certain period of time, it is suitable for the heat treatment. By this heat treatment, a gold bump 7 having a desired hardness and a flat surface can be obtained.

In the following, the invention will be more specifically described by way of examples. However, the invention is not limited by the examples described herein.

[Examples]

Adjusting a gold plating bath containing Na ₃ Au(SO ₃ ) ₂ , Na ₂ SO ₃ , sodium phosphate, 1,2-diaminoethane, Tl, and a lustering agent, forming gold bumps through an electrolytic gold plating step and a heat treatment step (Example 1-46). With respect to Examples 1-46, the shape of the gold bumps formed, the bath stability, the appearance of the plating film, the film hardness, and the uniform etching property of the gold bumps peeled off by the Au sputtering film were evaluated by the following evaluation methods.

[Gold bump shape: flatness (μm)]

The flatness of the surface of the gold bump, as shown in Fig. 2, is evaluated by using the height difference C between the highest point A and the lowest point B of the surface of the gold bump as an index. The smaller the value of the height difference, the more flat the surface is. "Highest point" means the most convex portion on the surface of the gold bump (the joint surface 7a with the substrate electrode), and the "lowest point" means the least convex portion or the most concave portion. For the flatness measurement, a laser microscope VK-9710 (manufactured by KEYENCE Co., Ltd.) was used.

[Bath stability]

After performing electrolytic gold plating on the plated object, observe the situation of the gold plating bath to The following benchmarks were evaluated. The symbols shown in Table 1-7 refer to the following observations.

○: There is no gold deposit in the gold plating bath

×: In the gold-plated bath, the level of gold is judged by the naked eye.

[Appearance of plating film]

The surface appearance of the gold bumps formed on the object to be plated was observed and evaluated on the basis of the following criteria. The symbols shown in Tables 1-7 each refer to the observations described below.

○: uniform appearance

×: The color is red, there is a land-like precipitate, and there is a spot, or a brownish brown

[Film hardness (Vicat hardness; HV)]

A square gold bump having a side of 100 μm was used for the two gold bumps formed on the object to be plated, and after heat treatment at 200 ° C for 30 minutes, and heat treatment at 300 ° C for 30 minutes, after heat treatment, The hardness of the gold bumps was measured. The measurement was carried out using a micro hardness tester HM-221 manufactured by MITSUTOYO Co., Ltd., and the measurement conditions were such that the measurement pressure was maintained at a load of 25 gf for 10 seconds.

[Uniform etching of gold bumps]

When the Au sputtering film of the object to be plated was etched by iodine etching, the surface morphology of the bump was observed. Use a metal microscope to 50~ Observation at a magnification of 150 times. The symbols shown in Tables 1-7 refer to the following observations.

In the meaning of the following symbols, "spot" refers to a form in which a portion selectively dissolved during etching forms a difference with a portion which is particularly dissolved. The "observed spot" refers to a state in which the color tone can be easily recognized by a microscope.

○: There are no "spots" on the surface of all the bumps on the plated object.

×: There is a "spot" on the surface of the bump.

[Comprehensive Evaluation]

A comprehensive evaluation is performed from the above evaluation results. The meanings of the symbols shown in Tables 1-7 are as follows.

○: The above evaluation results regarding the formed gold plating film (gold bump) and the gold plating bath after the plating treatment were all good.

X: The above evaluation results regarding the formed gold plating film (gold bump) and the gold plating bath after the plating treatment contained poor results.

(Example 1-5)

Tetramethylidene is selected as a glossing agent. The content of each component of the non-cyanide electrolytic gold plating bath of the present invention in Example 1-5 is as follows. The content of other ingredients except tetramethylammonium is the same.

<Content of each component of the gold-plated bath>

Na ₃ Au(SO ₃ ) ₂ : containing Au element, 10g/L

Na ₂ SO ₃ : 60g/L

Sodium phosphate: 5g/L

1,2-diaminoethane: 10g/L

Tl: 15mg/L

Tetramethylidene: Example 1:1mmol/L

Example 2: 5 mmol/L

Example 3: 10 mmol/L

Example 4: 50 mmol/L

Example 5: 100 mmol/L

The material to be plated is a cross-section of Au/TiW/SiO ₂ . The resist film 8 of the tantalum wafer is a positive resist of a novolak type. The photoresist film 8 is provided with two openings 8a which are patterned with a pitch of 20 μm. One opening 8a is a rectangle having a short side of 20 μm and a long side of 100 μm. The other opening portion 8a is a square having a side of 100 μm.

In the electrolytic gold plating, the object to be plated was immersed in a gold plating bath of 1 L of Example 1-5, and the plating temperature was 50 to 60 ° C and the current density was 0.8 A/dm ² . The current efficiency of the non-cyanide electrolytic gold plating bath is usually 100% under a certain plating operation condition.

A plating film having a film thickness of 18 μm was formed on the object to be plated by an electrolytic gold plating step. After the plating film was formed, the photoresist film 8 was dissolved and removed from the object to be plated (矽 wafer) using methyl ethyl ketone. After the photoresist film 8 was removed, the plated material was immersed in the sufficiently stirred iodine-based etching solution at room temperature for 90 seconds, and the Au sputtering film was etched. Then, the object to be plated was subjected to co-washing using an alcohol-based rinsing liquid, and dried air was blown and dried.

The plated material is heat treated using a refined oven. The temperature conditions were carried out at 200 ° C for 30 minutes and at 300 ° C for 30 minutes.

The evaluation results of Examples 1-5 are shown in Table 1. In Table 1, the tetramethylene fluorene system is represented by yttrium A.

(Examples 6-10)

In the gold plating bath used in Example 1, a gold plating bath containing propane sultone instead of tetramethylene fluorene was adjusted, and gold bumps were formed (Examples 6-10). The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 1-5. The respective contents of the propane sultones of Examples 6 to 10 are as follows. The contents of the other components were the same as those of Examples 1-5 except for propane sultone. The evaluation results of Examples 6-10 are shown in Table 1. In Table 1, propane sultone is represented by 碸B.

<content of propane sultone>

Example 6: 1 mmol/L

Example 7: 5 mmol/L

Example 8: 10 mmol/L

Example 9: 50 mmol/L

Example 10: 100 mmol/L

(Examples 11-15)

In the gold plating bath used in Example 1, a gold plating bath containing 1,4-butane sultone substituted tetramethylene fluorene was adjusted, and gold bumps were formed (Examples 11-15). Electrolytic gold plating conditions and heat treatment conditions are the same as in Examples 1-5 . The respective contents of the 1,4-butane sultones of Examples 11 to 15 are shown below. The content of the other components except 1,4-butane sultone was the same as in Example 1 except that 1,2-diaminoethane. The content of 1,2-diaminoethane was 12 g/L. The evaluation results of Examples 11-15 are shown in Table 2. In Table 2, 1,4-butane sultone is represented by 碸C.

<Content of 1,4-butane sultone>

Example 11:1 mmol/L

Example 12: 5 mmol/L

Example 13: 10 mmol/L

Example 14: 50 mmol/L

Example 15: 100 mmol/L

(Examples 16-20)

In the gold plating bath used in Example 11, a gold plating bath containing cyclobutanide substituted 1,4-butane sultone was adjusted, and gold bumps were formed (Examples 16-20). The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 1-5. The respective contents of the cyclic oxime of Examples 16-20 are as follows. The other contents except for the cyclic oxime are the same as those of the examples 11-15. The evaluation results of Examples 16-20 are shown in Table 2. In Table 2, the ring oxime is represented by 碸D.

<Content of ring 碸 >>

Example 16: 1 mmol/L

Example 17: 5 mmol/L

Example 18: 10 mmol/L

Example 19: 50 mmol/L

Example 20: 100 mmol/L

(Examples 21-25)

In the gold plating bath used in Example 1, a gold plating bath containing a 3-sulfo-substituted tetramethylene afluorene was adjusted, and gold bumps were formed (Examples 21-25). The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 1-5. The respective contents of the 3-sulfenes of Examples 21 to 25 are shown below. The content of the other components except 3-sulfene was the same as in Example 1-5. The evaluation results of Examples 21-25 are shown in Table 3. In Table 3, the 3-sulfene group is represented by 碸E.

<3-sulfene content>

Example 21:1mmol/L

Example 22: 5 mmol/L

Example 23: 10 mmol/L

Example 24: 50 mmol/L

Example 25: 100 mmol/L

(Examples 26-30)

In the gold plating bath used in Example 1, the gold plating bath containing 4,4-dioxo-1,4-oxathiane substituted tetramethylene fluorene was adjusted, and gold bumps were formed (Example 26) -30). The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 1-5. The respective contents of 4,4-dioxo-1,4-oxathiolane of Examples 26 to 30 are shown below. The content of the other components except 4,4-dioxy-1,4-oxathiane was the same as in Example 1-5. The evaluation results of Examples 26-30 are shown in Table 3. In Table 3, 4,4-dioxo-1,4-oxathiolane Expressed as 碸F.

<4,4-Dioxy-1,4-oxothiane content>

Example 26: 1 mmol/L

Example 27: 5 mmol/L

Example 28: 10 mmol/L

Example 29: 50 mmol/L

Example 30: 100 mmol/L

(Examples 31-35)

In the gold plating bath used in Example 1, a gold plating bath containing potassium butylsulfonate in place of tetramethylene fluorene was adjusted, and gold bumps were formed (Examples 31-35). The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 1-5. The respective contents of potassium acesulfame of Examples 31 to 35 are shown below. The contents of the other components except potassium sulfonamide were the same as in Examples 1-5. The evaluation results of Examples 31-35 are shown in Table 4. In Table 4, potassium acesulfame is represented by 碸G.

<content of potassium sulfonamide>

Example 31:1mmol/L

Example 32: 5 mmol/L

Example 33: 10 mmol/L

Example 34: 50 mmol/L

Example 35: 100 mmol/L

(Examples 36-38)

In the gold-plated bath using Examples 26-35, the adjustment was not only used alone Gold bumps (Examples 36-38) were formed using 4,4-dioxo-1,4-oxathiane or potassium butyl sulfonate in combination with two gold plating baths of the glossing agent. The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 26-35. The respective contents of 4,4-dioxo-1,4-oxathiane and potassium acesulfame of Examples 36 to 38 are shown below. The contents of the other components except 4,4-dioxo-1,4-oxathiane and potassium acesulfame were the same as in Examples 26-35. The evaluation results of Examples 36-38 are shown in Table 4. In Table 4, 4,4-dioxo-1,4-oxathiane is represented by 碸F, and potassium acesulfame is represented by 碸G.

<4,4-Dioxy-1,4-oxothiane content>

Example 36: 10 mmol/L

Example 37: 10 mmol/L

Example 38: 50 mmol/L

<content of potassium sulfonamide>

Example 36: 10 mmol/L

Example 37: 50 mmol/L

Example 38: 50 mmol/L

(Examples 39-40)

In the gold plating bath used in Example 1, a gold plating bath in which the content of Na ₃ Au(SO ₃ ) _{2 was} changed was adjusted, and gold bumps were formed (Examples 39-40). The electrolytic gold plating conditions and the heat treatment conditions were the same as in the first embodiment. The respective contents of the Au element of Na ₃ Au(SO ₃ ) ₂ of Examples 39 to 40 are as follows. The content of the other components except Na ₃ Au(SO ₃ ) _{2 was the} same as in Example 1. The evaluation results of Examples 39-40 are shown in Table 4. In Table 4, the tetramethylene fluorene system is represented by yttrium A.

<Na ₃ Au(SO ₃ ) ₂ content>

Example 39: Containing Au element 8g/L

Example 40: Containing Au element 15g/L

(Examples 41-42)

In the gold plating bath used in Example 1, a gold plating bath in which the content of 1,2-diaminoethane was changed was adjusted, and gold bumps were formed (Examples 41 to 42). The electrolytic gold plating conditions and the heat treatment conditions were the same as in the first embodiment. The respective contents of 1,2-diaminoethane of Examples 41 to 42 are shown below. The content of the other components except the 1,2-diaminoethane was the same as in Example 1. The evaluation results of Examples 41-42 are shown in Table 5. In Table 5, the tetramethylene fluorene system is represented by yttrium A.

<1,2-diaminoethane content>

Example 41: 8 g/L

Example 42: 12g/L

(Examples 43-44)

In the gold plating bath used in Example 1, a gold plating bath having a content of the change T1 was adjusted, and gold bumps were formed (Examples 43 to 44). The electrolytic gold plating conditions and the heat treatment conditions were the same as in the first embodiment. The respective contents of Tl of Examples 43-44 are shown below. The content of the other components except Tl was the same as in Example 1. The evaluation results of Examples 43-44 are shown in Table 5. In Table 5, the tetramethylene fluorene system is represented by yttrium A.

<Tl content>

Example 43: 10 mg/L

Example 44: 20 mg/L

(Examples 45-46)

In the gold plating bath used in Example 1, a gold plating bath in which the content of Na ₂ SO _{3 was} changed was adjusted, and gold bumps were formed (Examples 45 to 46). The electrolytic gold plating conditions and the heat treatment conditions were the same as in the first embodiment. The respective contents of Na ₂ SO ₃ of Examples 45-46 are shown below. The content of the other components except Na ₂ SO _{3 was the} same as in Example 1. The evaluation results of Examples 45-46 are shown in Table 5. In Table 5, the tetramethylene fluorene system is represented by yttrium A.

<Content of Na ₂ SO ₃ >

Example 45: 40 g/L

Example 46: 80 g/L

Examples 1-35 are examples in which gold plating baths each containing one type of glossing agent at different concentrations are used. The flatness (height difference) required for the use of the gold bump is 3 μm or less, preferably 2 μm or less. It can be seen from Table 1-5 that the gold bumps formed in Examples 1-35 have a height difference of 2 μm or less. The appearance of the plating film is not reddish color, land-like precipitate, brownish brown, plaque, etc., and the plating periphery is also good.

Examples 36-38 are examples of gold plating baths using two glossing agents in combination. When two types of glossing agents are used in combination, a gold bump having a flatness of 2 μm or less, a plating film appearance, or a good plating periphery can be obtained in the same manner as in the case of using one type of glossing agent alone.

In other words, the gold bump of the present invention has a required flatness because it exhibits sufficient bonding force when the electrodes are joined. In particular, gold bumps of the present invention are suitable for gold bumps having a narrow pitch.

The flatness of the gold bumps corresponds to the concentration of each glossing agent. The correspondence relationship differs depending on the glossing agent, and when, for example, tetramethylene sulfonium (Example 1-5) or 1,4-butane sultone (Examples 11-15) is used as the glossing agent, The higher the concentration of the glossing agent, the lower the flatness of the gold bumps.

Therefore, the present invention can adjust the gold bumps to the desired flatness by adjusting the concentration of the glossing agent used. In particular, when cyclobutene (Examples 16-20) or 4,4-dioxo-1,4-oxathiane (Examples 26-30) are used as the glossing agent, the concentration of the glossing agent The lower the temperature, the lower the flatness of the gold bumps. Therefore, when the present invention uses cyclobutyl fluorene or 4,4-dioxo-1,4-oxathiane as a glossing agent, a small amount of a glossing agent is used. The content of the gold bumps with a small flatness can be obtained.

The gold bumps formed in Examples 1-38 were distributed at a hardness of about 35 to 120 HV after heat treatment. For example, in Example 28 and Example 29, 4,4-dioxo-1,4-oxethiohexane was used as a glossing agent at a concentration of 10 mmol/L and 50 mmol/L. The hardness of the gold bump formed by the above examples at 300 ° C was 10 HV/L when the concentration of the glossing agent was 10 mmol/L (Example 28), and was 50 mmol/L (Example 29). It is 62HV.

In Example 33 and Example 34, potassium acesulfame was used as a glossing agent, and the concentrations thereof were 10 mmol/L and 50 mmol/L. The hardness of the gold bump formed by the above examples at 200 ° C was 10 mmol/L when the concentration of the glossing agent was 10 mmol/L (Example 33), and was 50 HV/L (Example 34). It is 110HV. The hardness at the time of heat treatment at 300 ° C was 48 HV when the concentration of the glossing agent was 10 mmol/L (Example 33), and 54 HV when it was 50 mmol/L (Example 34).

The hardness of the gold bump after heat treatment tends to be higher as the concentration of the cerium or lanthanum as the glossing agent is higher. Therefore, in the present invention, by increasing the concentration of the glossing agent, it is possible to form a gold bump having a high hardness in accordance with the type of the conductive particles of the conductive adhesive to be used or the hardness of the target metal at the time of eutectic bonding.

Here, in the glossing agent used in the present invention, when the concentration of 4,4-dioxo-1,4-oxathiane is higher, the flatness tends to be larger (Example 26- 30). The hardness of the gold bump after heat treatment, the higher the concentration of the glossing agent, the higher the tendency, when the glossing agent is used alone, When a gold bump having a high hardness after heat treatment is formed, there is a case where the flatness is increased or a heat treatment condition must be adjusted.

For example, in the case of Example 28 and Example 29 described above, when the concentration of 4,4-dioxo-1,4-oxathiane is 10 mmol/L, the flatness of the gold bump is 1.40 μm (implementation) Example 28). In this regard, when the concentration of 4,4-dioxo-1,4-oxathiane is 50 mmol/L, the flatness of the gold bump is 1.59 μm (Example 28), as in Example 29 The gold bumps formed were flatter than the gold bumps formed in Example 28.

However, when the concentration of the present invention such as 4,4-dioxo-1,4-oxathiane is higher, there is a tendency for the flatness to become larger, even if a high hardness gold convex is obtained. In the case of a block, it is possible to prevent the flatness from becoming large by using other glossing agents in combination.

Example 37 and Example 38 were used in combination with a concentration of 10 mmol/L (Example 37) and 50 mmol/L (Example 38) of 4,4-dioxo-1,4-oxathiane, at a concentration of 50 mmol/L of potassium acesulfame was used as a glossing agent.

The hardness of the gold bump formed by the above examples was heat-treated at 200 ° C, and the concentration of 4,4-dioxo-1,4-oxathiane as a glossing agent was 10 mmol/L ( Example 37) was 108 HV, and when it was 50 mmol/L (Example 38), it was 115 HV. The hardness at the time of heat treatment at 300 ° C, when the concentration of 4,4-dioxo-1,4-oxathiane is 10 mmol/L (Example 37) is 51 HV, and is 50 mmol/L (Example) 38) is 57HV. In other words, the hardness after heat treatment increases as the concentration of the glossing agent increases.

When comparing the embodiments with respect to the flatness of the gold bumps, the gold bumps formed in Example 38 were 1.25 μm with respect to the flatness of the gold bumps formed in Example 37 being 1.34 μm. When 4,4-dioxo-1,4-oxathiane is used alone, the higher the concentration of the glossing agent, the smaller the flatness.

In other words, in the present invention, by using a glossing agent together with other glossing agents, gold bumps having high hardness and low flatness after heat treatment can be obtained without adjusting the heat treatment conditions.

Example 1 and Examples 39-46 are examples in which the concentration of each component other than the glossing agent was changed under the same concentration of the glossing agent. In these examples, the same results as in Examples 1-38 were obtained regarding the flatness of the formed gold bumps, the appearance of the plating film, the periphery of the plating, and the hardness after the heat treatment. In other words, the present invention is not limited by the content of other components other than the glossing agent, and the desired flatness, hardness, and the like can be obtained.

(Comparative Example 1-6)

In the gold plating bath used in Example 1, gold bumps were formed without using a glossing agent (Comparative Example 1-6). The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 1-5. The evaluation results of Comparative Examples 1-6 are shown in Table 6.

(Comparative Example 7-13)

In the gold plating bath used in Example 1, one selected from the group consisting of Aamu A and 碸B-G was used as a glossing agent to adjust the content to 200 mmol/L to form a gold convex. Block (Comparative Example 1-6). The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 1-5. The evaluation results of Comparative Example 7-13 are shown in Tables 6 and 7.

(Comparative Example 14-20)

In the gold plating bath used in Example 1, one of Acetone A and 碸B-G was used as a glossing agent to adjust the content to 0.1 mmol/L to form gold bumps (Comparative Examples 14-20). The electrolytic gold plating conditions and heat treatment conditions were the same as in Examples 1-5. The evaluation results of Comparative Examples 14-20 are shown in Table 7.

As can be seen from Tables 6 and 7, the appearance of the plating film of the gold bump of Comparative Example 1-20 was confirmed by hue red, land-like precipitate, brownish brown, plaque, and the like. Therefore, the plating periphery of these gold bumps is not good.

In Comparative Examples 1-20, Comparative Example 1-6 was a gold bump formed by a gold plating bath containing no glossing agent. These gold bumps have a surface height difference of more than 2 μm. In order to effectively secure the joint area at the time of electrode bonding, when the flatness (height difference) required for the bump application is 2 μm or less, the flatness of the gold bump is insufficient, and it is difficult to secure the joint area. Therefore, sufficient bonding force at the time of electrode bonding cannot be obtained.

Comparative Example 7-20 is a gold bump formed by a gold plating bath containing a glossing agent. However, since the content of the glossing agent is not appropriate, the color of the appearance of the plating film is red, and it is confirmed that there is a land-like precipitate or a spot, and a brownish-brown color is generated, and the periphery of the plating is not good.

Comparative Examples 7-13 of Comparative Examples 7-20, gold bumps formed by a gold plating bath having a higher concentration of the glossing agent than the examples. The flatness (surface height difference) of these gold bumps is 2 μm or less. Further, the gold bump of Comparative Example 7-10 using Aachen A and 碸B-E as a glossing agent had a hardness of more than 35 to 60 HV after heat treatment. Therefore, these gold bumps are not suitable for eutectic bonding.

The gold bumps of Comparative Examples 14-20 were gold bumps formed by a gold plating bath having a lower concentration of the glossing agent than the examples. The flatness (surface height difference) of these gold bumps exceeds 2 μm. Therefore, the flatness is insufficient, and the joint area cannot be ensured. Therefore, sufficient bonding force at the time of electrode bonding cannot be obtained. It was also confirmed that it was used for etching by Au sputtering on the surface of gold bumps. Iodine-based etching solution affects and is spotted.

1‧‧‧Semiconductor wafer

1'‧‧‧ circuit layer

2‧‧‧Al electrode

3‧‧‧Purified membrane

3a‧‧‧Opening membrane opening

4‧‧‧TiW Sputter

5‧‧‧ Gold Sputter

6‧‧‧UBM layer

7‧‧‧ Gold bumps

7a‧‧‧ joints of gold bumps

7’‧‧‧known gold bumps

7'a‧‧‧The joint surface of a conventional gold bump

8‧‧‧Photoresist film

8a‧‧‧ Opening of the photoresist film

9‧‧‧Semiconductor wafer

10‧‧‧Printed wiring substrate

11‧‧‧Hard substrate

12‧‧‧Substrate wiring pattern

13‧‧‧ substrate electrode

14‧‧‧ Sealing material

A‧‧‧ highest point

B‧‧‧ lowest point

C‧‧‧ height difference

[Fig. 1] is a cross-sectional view showing an example of a state in which a semiconductor wafer is provided on a conventional printed wiring board.

[Fig. 2] is a partially enlarged cross-sectional view showing a conventional gold bump portion formed on a semiconductor wafer.

[Fig. 3] is a partially enlarged cross-sectional view showing a gold bump portion of the present invention formed on a semiconductor wafer.

1‧‧‧Semiconductor wafer

1'‧‧‧ circuit layer

2‧‧‧Al electrode

3‧‧‧Purified membrane

3a‧‧‧Opening membrane opening

4‧‧‧TiW Sputter

5‧‧‧ Gold Sputter

6‧‧‧UBM layer

7‧‧‧ Gold bumps

7a‧‧‧ joints of gold bumps

8‧‧‧Photoresist film

8a‧‧‧ Opening of the photoresist film

Claims (7)

The invention relates to a non-cyanide electrolytic gold plating bath for forming gold bumps, which is characterized in that it comprises gold alkali sulfite or gold ammonium sulfite, a conductive salt, a crystal stabilizer, a crystal modifier, a buffer and a glossing agent, and the foregoing The content of the gold alkali sulfate salt or the gold ammonium sulfite is 1-20 g/L, the conductive salt is sodium sulfite, the content is 5 to 150 g/L, and the content of the glossing agent is 0.5 to 100 mmol/L. The non-cyanide electrolytic gold plating bath for forming a gold bump according to the first aspect of the invention, wherein the glossing agent is one or more compounds selected from the group consisting of an anthraquinone and/or a hydrazine. The non-cyanide electrolytic gold plating bath for forming gold bumps according to claim 1 or 2, wherein the glossing agent is selected from the group consisting of tetramethylene sulfonium, propane sultone, and 1,4-butane sulfonate. Lactone, cyclobutyl hydrazine, 3-hydroxycyclobutyl hydrazine, 4,4-dioxy-1,4-oxothiocyclohexane, 3-cyclobutene oxime, 3-cyclobutenazole-3-carbonate One or two or more compounds in the group of ester and potassium acesulfame potassium. The non-cyanide electrolytic gold plating bath for forming a gold bump according to any one of the first to third aspects, wherein the crystal modifier is one or more selected from the group consisting of a T1 compound, a Pb compound, and an As compound. The compound has a metal concentration of 0.1 to 100 mg/L. The non-cyanide electrolytic gold plating bath for forming gold bumps according to any one of claims 1 to 4, wherein the crystallizing stabilizer is a water-soluble amine, and the content of the water-soluble amine is 1 to 12 g/L. Gold bump formation as in any one of claims 1 to 5 a non-cyanide electrolytic gold plating bath, wherein the crystallizing stabilizer is one selected from the group consisting of 1,2-diaminoethane, 1,2-diaminopropane or 1,6-diaminohexane or Combination of 2 or more types. A method of forming a gold bump, comprising: performing electrolysis on a patterned semiconductor wafer by using a non-cyanide electrolytic gold plating bath for forming gold bumps according to any one of claims 1 to 6; a gold plating electroplating step, and a heat treatment step of heat-treating the semiconductor wafer subjected to electrolytic gold plating at 150 to 400 ° C for 5 minutes or more, and forming a surface height difference of 2 μm or less after the electrolytic gold plating step, after the heat treatment step Gold bumps with a hardness of 35~120HV.