JP4925792B2 - Non-cyan electrolytic gold plating bath for bump formation - Google Patents

Description

  The present invention is a non-cyan for bump formation suitable for forming gold bumps on a silicon wafer or a Ga / As compound wafer having a bump pattern patterned with a novolac positive photoresist, an acrylic negative photoresist, or the like. The present invention relates to a system electrolytic gold plating bath and a bump forming method using the same.

  For non-cyan electrolytic gold plating baths, for example, a plating bath using a chloroaurate or gold sulfite as a gold source and a compound such as thiouracil as a complex compound (stabilizer) (Patent Document 1), or a gold source A plating bath or the like using a gold sulfite alkali salt or gold ammonium sulfite as a stabilizer and a water-soluble amine as a stabilizer is known.

  As the latter electrolytic gold plating bath, gold sulfite alkali salt or ammonium gold sulfite, water-soluble amine, a trace amount of Tl compound, Pb compound or As compound as a crystal modifier, sulfite and sulfate as conductive salts, Those having a basic composition with a buffer are conventionally used.

  The plating film formed by this non-cyan electrolytic gold plating bath is excellent in physical properties such as electrical conductivity and thermocompression bonding, and is excellent in chemical properties such as oxidation resistance and chemical resistance. Therefore, this plating bath is used for forming bumps and wirings on compound wafers such as silicon wafers and Ga / As wafers. A method of forming gold bumps by electrolytic gold plating is known per se. For example, Patent Document 2 discloses a method of forming gold bumps using potassium gold cyanide.

By the way, the gold bump film formed by the non-cyan electrolytic gold plating bath having the above-mentioned basic composition is slightly crushed by the pressing force and spreads sideways because of its low hardness (soft Hv is 50 Hv or less). The trend is inevitable. As a result, the risk of short-circuiting has increased, and the recent trend toward smaller bump diameters and smaller bump pitches has led to problems in which sufficient mounting reliability cannot be obtained.
JP 2004-176171 A (paragraph number [0006]) JP 2003-7762 A (paragraph numbers [0021], [0022])

  Usually, a gold plating film such as a gold bump formed using a non-cyan electrolytic gold plating bath is as high as 70 to 140 Hv immediately after plating, but after a heat treatment (up to about 300 ° C.) step, the gold crystal grains are The hardness decreases to about 35-60 Hv by coarsening and recrystallization. Therefore, it is necessary to form a gold bump (about 80 ± 20 Hv) having a high film hardness not only immediately after plating but also after heat treatment.

  In other words, gold bumps, which are the legs of LCD driver ICs, are becoming smaller and smaller pitches year by year for mounting on small and medium-sized machines, and direct bonding to LCD glass such as COG increases. The minimum pitch is 15 μm or less. Are becoming practical levels.

  In the semiconductor mounting process, gold bumps have a low film hardness (softness) whether they are bonded via an anisotropic conductive film or directly bonded when bonded to a counterpart substrate. The tendency for the gold bumps to spread laterally due to being crushed by the pressure is inevitable. As a result, it is conceivable that adjacent bumps are crushed between the narrow pitch bumps, resulting in a short circuit.

  Accordingly, from the viewpoint of mounting reliability, the gold bump film preferably has a certain degree of film hardness (depending on the specification, the Vickers hardness is in the range of 60 to 100 Hv, and the film hardness near 80 Hv may be referred to. Many) is required.

  The present invention has been made in view of the above circumstances, and in order to cover a decrease in reliability that a gold bump is crushed and spreads by a crimping force when bonded to a counterpart substrate or the like, a gold bump having a relatively high film hardness (generally, The purpose is to form a film hardness of around 80 ± 20 Hv.

  As a result of repeated studies to achieve the above object, the present inventor blends a predetermined amount of polyalkylene glycol and / or amphoteric surfactant into the basic composition of the above-described general non-cyan electrolytic gold plating bath. Thus, it was found that a gold bump film having a high Vickers hardness (about 80 ± 20 Hv) can be formed after heat treatment (about 300 ° C. at the maximum), and the present invention has been completed.

  In the gold bump film formed by the above non-cyan electrolytic gold plating bath, both organic and inorganic components contained in the plating bath coexist due to the remarkable precipitation suppressing effect of polyalkylene glycol or amphoteric surfactant. Analyze. As a result, even after the heat treatment step, the coarsening / recrystallization of the gold crystal is suppressed, and a high film hardness of 80 ± 20 Hv can be obtained without lowering the hardness.

  That is, the present invention that solves the above problems is described below.

  [1] A gold source composed of gold sulfite alkali salt or gold ammonium sulfite, a stabilizer composed of a water-soluble amine, a crystal modifier, a conductive salt composed of sulfite and sulfate, and a buffer, A non-cyan electrolytic gold plating bath for bump formation containing an alkylene glycol and / or an amphoteric surfactant, and a non-cyan electrolytic gold plating bath for bump formation containing 0.01 g / L or more of polyalkylene glycol.

  [2] A gold source comprising a gold sulfite alkali salt or ammonium gold sulfite, a stabilizer comprising a water-soluble amine, a crystal modifier, a conductive salt comprising sulfite and sulfate, and a buffer, A non-cyan electrolytic gold plating bath for bump formation containing an alkylene glycol and / or an amphoteric surfactant, containing 1.5 to 20 g / L of polyalkylene glycol having an average molecular weight of less than 300 to 900, or an average A non-cyan electrolytic gold plating bath for bump formation containing 0.01 g / L or more of a polyalkylene glycol having a molecular weight of 900 to 10,000 and 0.1 to 1000 mg / L of an amphoteric surfactant.

  [3] Amphoteric surfactant is 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, lauric acid amidopropyl hydroxysulfobetaine, fatty acid amidopropyl betaine, and fatty acid acyl-N-carboxyethyl- The non-cyan electrolysis gold plating bath for bump formation according to [1], which is one or more selected from N-hydroxyethylethylenediamine alkali salts.

  [4] The non-cyan electrolytic gold plating bath for bump formation according to [1], wherein the crystal modifier is a Tl compound, a Pb compound, or an As compound.

  [5] A bump forming method for performing electrolytic gold plating on a wafer patterned using the non-cyan electrolytic gold plating bath for bump formation described in [1].

  By using the non-cyan electrolytic gold plating bath of the present invention, it is possible to form a plating film having excellent liquid stability and liquid life, and uniform, dense and good appearance characteristics to the object to be plated. In addition, while maintaining good shear strength characteristics, gold bumps with high Vickers hardness (80 ± 20Hv) after heat treatment (before mounting) are formed according to the design size and the coating surface is flat. Is possible.

  The non-cyanide electroplating bath for gold bump formation of the present invention comprises a gold sulfite alkali salt or gold ammonium sulfite as a gold source, a water-soluble amine as a stabilizer, a trace amount of a crystal modifier, and a sulfite as a conductive salt. An electrolytic gold plating bath characterized by containing a predetermined amount of palladium, polyalkylene glycol and / or an amphoteric surfactant in a known gold plating basic bath comprising a salt, a sulfate and a buffer. Hereinafter, the essential components of the electrolytic gold plating bath of the present invention will be described for each component.

(1) Gold sulfite alkali salt, gold ammonium sulfite (gold source)
As the gold sulfite alkali salt used in the present invention, a known gold sulfite alkali salt can be used without limitation. Examples of the gold sulfite alkali salt include gold (I) sodium sulfite and potassium gold (I) sulfite. These may be used alone or in combination of two or more.

  In the electrolytic gold plating bath of the present invention, the above-described alkali gold sulfite or ammonium ammonium sulfite is used as a gold source, and the amount thereof is usually 1 to 20 g / L, preferably 8 to 15 g / L as the gold amount. L. If the blending amount of the gold sulfite alkali salt or the gold ammonium sulfite is less than 1 g / L, the plating film becomes non-uniform, and in some cases, it may be burnt. If it exceeds 20 g / L, there is no problem in the properties of the plating film, but it is an economical burden.

(2) Water-soluble amine (stabilizer)
Examples of water-soluble amines include polyamines such as 1,2-diaminoethane, 1,2-diaminopropane, diamines such as 1,6-diaminohexane, and the like. These may be used individually by 1 type and may use 2 or more types together.

  The compounding quantity of a water-soluble amine is 1-30 g / L normally, Preferably it is 4-20 g / L. If the blending amount of the water-soluble amine exceeds 30 g / L, the stability of the gold complex salt increases, but on the other hand, the resulting plating film is too hard and the surface roughness is too small, so that the anchor effect is insufficient and the bonding Insufficient strength or a large decrease in hardness after heat treatment of the film may cause a bump crushing, which may cause problems in terms of bondability. If it is less than 1 g / L, the limiting current density may be reduced, resulting in burnt plating.

(3) Tl compound, Pb compound, As compound (crystal modifier)
Examples of the crystal conditioner used in the electrolytic gold plating bath of the present invention include Tl compounds such as thallium formate, thallium malonate, thallium sulfate, and thallium nitrate; Pb compounds such as lead citrate, lead nitrate, and lead alkanesulfonate; Examples include As compounds such as diarsenic trioxide. These Tl compound, Pb compound, and As compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  The compounding amount of the crystal modifier can be appropriately used as long as the object of the present invention is not impaired, but the metal concentration is usually 0.1 to 100 mg / L, preferably 0.5 to 50 mg / L, particularly preferably. 3 to 25 mg / L. When the blending amount of the crystal modifier is less than 0.1 mg / L, there are cases where the plating bath is deteriorated, the stability and durability of the plating bath are deteriorated, and the plating bath is decomposed. If it exceeds 100 mg / L, the plating surface becomes non-uniform due to uneven current distribution, and the surface of the plated surface deteriorates due to the deterioration of the area around the plating, where the coarse Au particle agglomerates and the fine Au agglomerates are mixed. Since the Au particle mass to be analyzed becomes too large, the gold film formed becomes a “matte” mat-like appearance. Uneven appearance due to rough gold deposition, and peeling of the gold film due to excessive eutectoid of crystal modifiers In some cases, such as a bonding failure occurs.

(4) Sulfite, sulfate (conductive salt)
Examples of the sulfite and sulfate used as the conductive salt in the present invention include sulfites such as sodium sulfite, potassium sulfite, sodium pyrosulfite and sodium hydrogensulfite; and sulfates such as sodium sulfate. Of these, a combination of sodium sulfite and sodium sulfate is preferred.

  The blending amount of the sulfite and sulfate in the electrolytic gold plating bath of the present invention can be appropriately set within a range not impairing the object of the present invention, but is preferably the following blending amount.

The sulfite is usually 5 to 100 g / L as SO ₃ ^2- amount, preferably 10 to 80 g / L, particularly preferably 20 to 60 g / L. If the blending amount of sulfite is less than 5 g / L, the throwing power and liquid stability may be deteriorated and the plating bath may be decomposed. If it exceeds 100 g / L, the limit current density decreases and burnt plating occurs. There is a case.

The sulfate is usually 1 to 120 g / L as SO ₄ ^2- amount, preferably 1 to 60 g / L, particularly preferably 1 to 40 g / L. If it is less than 1 g / L, the hardness of the formed film after heat treatment may be too high, resulting in defects in the bonding between the bump and the substrate, or deterioration of the liquid stability and decomposition of the plating bath. If it exceeds 120 g / L, the limiting current density may be lowered, resulting in burnt plating.

(5) Buffering agent The buffering agent used in the present invention is not particularly limited as long as it is usually used in an electrolytic gold plating bath. For example, inorganic acid salts such as phosphates and borates, Organic acid (carboxylic acid, hydroxycarboxylic acid) salts such as citrate, phthalate and ethylenediaminetetraacetate can be used, but phosphate is particularly preferable.

  The blending amount of the buffer in the non-cyan electrolytic gold plating bath of the present invention is usually 0.1 to 30 g / L, preferably 1 to 20 g / L, and particularly preferably 2 to 15 g / L. When the blending amount is less than 0.1 g / L, the solution stability may deteriorate due to a decrease in pH and the plating bath components may be decomposed. When the amount exceeds 30 g / L, the limit current density decreases. There are cases where defects such as burnt plating or densification of the plating film, a decrease in hardness after heat treatment of the film, and bondability occur.

(6) Polyalkylene glycol, amphoteric surfactant Examples of the polyalkylene glycol blended in the non-cyan electrolytic gold plating bath of the present invention include polyethylene glycol and polypropylene glycol.

  Examples of the amphoteric surfactant to be blended in the non-cyan electrolytic gold plating bath of the present invention include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, lauric acid amidopropyl hydroxysulfobetaine, and fatty acid amidopropyl. Examples include betaine-based amphoteric surfactants such as betaine; aminocarboxylate-based amphoteric surfactants such as fatty acid acyl-N-carboxyethyl-N-hydroxyethylethylenediamine alkali salts; imidazoline derivative-based amphoteric surfactants.

  The blending amount of the polyalkylene glycol used in the non-cyan electrolytic gold plating bath of the present invention is 0.01 g / L or more, preferably 0.01 to 20 g / L. The blending amount of the polyalkylene glycol is divided into a case where a polyalkylene glycol having an average molecular weight of 300 to less than 900 is blended and a case where a polyalkylene glycol having an average molecular weight of 900 to 10,000 is blended. It is more preferable to set the conditions for the blending amount.

  In this case, the blending amount of the polyalkylene glycol and amphoteric surfactant in the setting of separation conditions is set to 1.5 to 20 g / L when using a polyalkylene glycol having an average molecular weight of less than 300 to 900, 2-10 g / L is preferable. When the polyalkylene glycol having an average molecular weight of 900 to 10,000 is used in combination with the amphoteric surfactant, the blending amount of the polyalkylene glycol is 0.01 g / L or more and the blending amount of the amphoteric surfactant is 0.1 to 1000 mg / L. It is. Preferably, the blending amount of the polyalkylene glycol having an average molecular weight of less than 300 to 900 is 2 to 10 g / L, and the blending amount of the amphoteric surfactant is 0.5 to 500 mg / L. Particularly preferably, the blending amount of the polyalkylene glycol having an average molecular weight of 900 to 10,000 is 0.05 to 0.5 g / L, and the blending amount of the amphoteric surfactant is 1 to 200 mg / L.

  The low molecular weight polyalkylene glycol having an average molecular weight of 300 to less than 900 used in the non-cyan electrolytic gold plating bath of the present invention has the effect of increasing the bump hardness when the blending amount is as large as 1.5 g / L or more. Moreover, since low molecular weight polyalkylene glycol is easy to dissolve, it is not always necessary to use it together with an amphoteric surfactant. When the blending amount of the low molecular weight polyalkylene glycol exceeds 20 g / L, the effect of increasing the bump hardness does not increase as much as the blending amount increases.

  On the other hand, a high molecular weight polyalkylene glycol having an average molecular weight of 900 to 10000 also has an effect of increasing the bump hardness when the blending amount is as large as 0.01 g / L or more. However, it is necessary to add 0.1 mg / L or more of an amphoteric surfactant that has the same efficacy and that, when used in combination, provides a synergistic effect on the efficacy. Further, since the high molecular weight polyalkylene glycol is difficult to dissolve, it is necessary to use the high molecular weight polyalkylene glycol in combination with the amphoteric surfactant so that it can be easily dissolved. In addition, even if the compounding quantity exceeds 1000 mg / L, the amphoteric surfactant does not increase the effectiveness of increasing the bump hardness as much as the increase in the compounding quantity.

  When gold bump plating is performed on a silicon wafer or compound wafer by plating using the non-cyan electrolytic gold plating bath of the present invention, the plating operation may be performed according to a conventional method. For example, a masking agent is used to mask a wafer having Ti—W as a connecting metal (a metal that connects the base aluminum and the gold bump) and an Au sputtered film or the like formed thereon, and then the wafer is covered. For example, a method of performing electrolytic gold plating as a plated product and then removing the mask agent by dissolving it in a solvent can be used.

  For the masking agent, as a novolak positive photoresist, for example, commercially available LA-900, HA-900, acrylic negative photoresist, for example, BMR C-1000 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), etc. Can be mentioned.

  The plating temperature is usually 40 to 70 ° C, preferably 50 to 65 ° C. When the plating bath temperature is less than 40 ° C., the current efficiency is lowered and the throwing power is deteriorated. In other words, due to uneven current distribution, the surface of the coarse Au particles and the portion of fine Au particles are mixed on the plating surface, and the plating film has a non-uniform film thickness / non-uniform appearance. The bath voltage increases and the plating bath may decompose. If the plating bath temperature exceeds 70 ° C., the surface Au particles on the plating film become coarse, resulting in a matte “smooth” surface, where the beads are buried and become unsuitable for bonding, or the gold complex of the components of the plating bath May thermally decompose and the plating bath may decompose.

The set current density that can be used is usually 2.0 A / dm ² or less, preferably 0.1 to 1.5 A / min under conditions of a gold concentration of 8 to 15 g / L and a plating bath temperature of 60 ° C. dm ^2, particularly preferably 0.3~0.8A / dm ^2. If the set current density is outside the above range, abnormal precipitation such as dendritic (limb) -like deposition occurs on the surface of the deposited plating film, or a bath load is applied due to high overvoltage, and the gold complex is As a result of destabilization, the plating bath may be decomposed. If the set current density falls outside the above range, the workability will deteriorate, making it unsuitable for mass production, or the surface Au particle lump of the plating film will become coarse, resulting in a mat-like “loose” surface and beads being buried May not be suitable for joining.

  The pH of the non-cyan electrolytic gold plating bath of the present invention is usually 7.0 or higher, preferably 7.2 to 10.0. If the pH of the non-cyan electrolytic gold plating bath is less than 7.0, the plating bath becomes extremely unstable, and decomposition may occur as in the case where the set current density exceeds the predetermined range. On the other hand, if the pH exceeds 10.0, the mask agent may dissolve and contaminate the plating film, or the desired gold bump shape may not be formed due to the disappearance of the resist pattern.

  In the non-cyan electrolytic gold plating bath of the present invention, other components such as a pH adjuster and a stabilizer may be appropriately used within a range not impairing the object of the present invention.

  Examples of the pH adjuster include dilute sulfuric acid, sulfite, and phosphoric acid as acids, and sodium hydroxide, potassium hydroxide, aqueous ammonia, and the like as alkalis.

  Examples of the crystal modifier include heavy metal (Tl, Pb, As, etc.) ions.

  The non-cyan electrolytic gold plating bath of the present invention is supplemented and managed with gold sulfite alkali salt as a gold source and other components constituting the plating bath for 2 turns (all the gold amount in the plating bath is consumed for plating) If you do this, you can make one turn.)

  The non-cyan electrolytic gold plating bath of the present invention is not selected as long as the substrate is metallized and can be electrically conductive. For example, a novolac positive photoresist or an acrylic negative photoresist is used as a mask agent. The present invention can be particularly suitably applied to formation of bumps, wirings, etc. on a silicon wafer patterned and used on a compound wafer such as a Ga / As wafer.

Examples 1-6, Comparative Examples 1-2
A non-cyan electrolytic gold plating bath was prepared with the formulation shown in Tables 1-2. The unit of blending concentration of each raw material is g / L unless otherwise specified. However, Na ₃ Au (SO ₃ ) ₂ represents the concentration with respect to the Au amount, Na ₂ SO ₃ represents the SO ₃ amount, and Na ₂ SO ₄ represents the concentration with respect to the SO ₄ amount.

As the object to be plated, a silicon wafer having a bump opening patterned with a novolac positive photoresist (base cross-sectional composition is gold sputtered film / TiW / SiO ₂ .Si) was used. A cross-sectional view thereof is shown in FIG. In FIG. 1A, 2 is a mask agent (photoresist), 4 is a gold sputtered film, 6 is a silicon wafer, and 8 is a gold bump. The silicon wafer 6 is covered with TiW to form a connection metal layer (not shown because the layer is extremely thin).

Usually, a silicon wafer having a bump opening patterned with a novolac-based positive photoresist as the object to be plated [the cross-sectional view of which is shown in FIG. 1B] (the substrate cross-sectional composition is gold sputtered film / TiW / SiO ₂ Use Si). However, in Examples 1 to 6 and Comparative Examples 1 and 2, in order to facilitate the evaluation of the plating bath, an object to be plated shown in FIG.

  In FIG. 1B, 12 is a mask agent (photoresist), 14 is a sputtered gold film, 16 is a passivation film, 18 is a silicon wafer, 20 is an Al electrode, and 22 is a gold bump. The passivation film 16 and the Al electrode 20 are covered with TiW to form a connection metal layer (not shown because the layer is extremely thin).

  An object to be plated was immersed in 1 L of the prepared non-cyan electrolytic gold plating bath and energized to form a plating film having a thickness of 18 μm. The current efficiency of the non-cyan electrolytic gold plating bath is usually 100% under the steady plating operation conditions.

  After forming a film having a predetermined film thickness, the mask agent is removed, and the formed gold bump plating film appearance, film hardness (unheated, after heat treatment at 150 ° C. for 30 minutes, after heat treatment at 200 ° C. for 30 minutes, at 250 ° C. After the heat treatment for 30 minutes and after the heat treatment at 300 ° C. for 30 minutes, the etching property of the Au sputtered film by the iodine-based etchant was evaluated by the following method and criteria, and the stability of the gold plating bath was evaluated. A result is combined with Tables 1-2 and shown.

[Bath stability]
The state of the plating bath after plating the object to be plated was observed and evaluated according to the following criteria.
Decomposition: The plating solution was decomposed.
X: Precipitation of gold was observed in the plating bath at a level that can be seen with the naked eye.
Δ: No gold precipitation was observed in the plating bath. A level at which 1000 mL of plating bath can be filtered through a 0.2 μm membrane filter and precipitation can be visually observed.
○: No gold precipitation was observed in the plating bath.

[Appearance of plating film]
The appearance of the surface film of the gold bump formed on the object to be plated was visually observed and observed with an optical microscope, and evaluated according to the following criteria.
X: The color tone is red, dendrite-like precipitation is observed, unevenness is observed, or burns occur.
(Triangle | delta): Although there is no abnormal precipitation, it is a glossy appearance.
○: The color tone is lemon yellow, and it has a non-semi-glossy uniform appearance.

[Film hardness (Vickers hardness; Hv)]
Using the specific bump portion formed on the object to be plated, the film hardness (unheated, after heat treatment at 150 ° C. for 30 minutes, after heat treatment at 200 ° C. for 30 minutes, after heat treatment at 250 ° C. for 30 minutes, and at 30 ° C. at 30 ° C. Was measured with a Vickers hardness tester.

  The characteristics required for gold bump plating for fine pitch LCD driver ICs are that the film hardness range after heat treatment is within 80 ± 20 Hv. The measurement conditions were based on the condition that the measurement indenter was held at 25 gf load for 10 seconds.

[Etching property of Au sputtered film with iodine-based etchant]
The object to be plated was immersed in an iodine-based etchant sufficiently stirred at room temperature for 90 seconds, washed with an alcohol-based rinse, sprayed with ethanol, and dried with a dryer. Thereafter, the surface state of all the bumps formed on the object to be plated was observed at an magnification of 50 to 150 times using an optical microscope, and evaluated according to the following criteria.
X: Unevenness is observed on the surface of the bump of 50% or more.
Δ: Unevenness is observed on the surface of the bump in a limited area.
○: Unevenness is not observed on the surface of all bumps on the object to be plated.

〔Comprehensive evaluation〕
From the above evaluation results, the evaluation was made according to the following evaluation criteria.
X: Unfavorable results were included in the evaluation results regarding the formed gold plating film (gold bump) and the non-cyan electrolytic gold plating bath after the plating treatment.
◯: All the above evaluation results regarding the formed gold plating film (gold bump) and the non-cyan electrolytic gold plating bath after the plating treatment were good results.

In Tables 1 and 2, the following were used as the buffer A, buffer B, polyalkylene glycol A, polyalkylene glycol B, amphoteric surfactant C, and amphoteric surfactant D.
Buffer A; Disodium ethylenediaminetetraacetate Buffer B; Monosodium phosphate polyalkylene glycol A; Polyethylene glycol Average molecular weight 600
Polyalkylene glycol B; polyethylene glycol Average molecular weight 2000
Amphoteric surfactant C; 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine amphoteric surfactant D; amidopropyl hydroxysulfobetaine laurate

It is the schematic which shows the cross section of the to-be-plated object used for a plating bath evaluation test, (A) is the schematic which shows the cross section of the to-be-plated object used for the plating bath evaluation test in Examples 1-6 and Comparative Examples 1-2. (B) is the schematic which shows the cross section of the to-be-plated object used for a normal plating bath evaluation test.

Explanation of symbols

2,12 Mask material 4,14 Gold sputtered film 6,18 Silicon wafer 8,22 Gold bump 16 Passivation film 20 Al electrode

Claims (5)

Containing a gold source comprising a gold sulfite alkali salt or a gold ammonium sulfite, a stabilizer comprising a water-soluble amine, a crystal modifier, a conductive salt comprising a sulfite and a sulfate, a buffer, a polyalkylene glycol and A non-cyan electrolytic gold plating bath for bump formation containing an / amphoteric surfactant, containing 1.5 to 20 g / L of polyalkylene glycol having an average molecular weight of less than 300 to 900, and / or an average molecular weight A non-cyan electrolysis gold plating bath for bump formation containing 900 to 10,000 polyalkylene glycol in an amount of 0.01 g / L or more and an amphoteric surfactant in an amount of 0.1 to 1000 mg / L. Containing a gold source comprising a gold sulfite alkali salt or a gold ammonium sulfite, a stabilizer comprising a water-soluble amine, a crystal modifier, a conductive salt comprising a sulfite and a sulfate, a buffer, a polyalkylene glycol and A bump forming non-cyan electrolytic gold plating bath containing an amphoteric surfactant, containing 1.5 to 20 g / L of polyalkylene glycol having an average molecular weight of less than 300 to 900, or having an average molecular weight of 900 to 900 A non-cyan electrolytic gold plating bath for bump formation containing 10,000 g / L or more of 10,000 polyalkylene glycol and 0.1 to 1000 mg / L of an amphoteric surfactant. Amphoteric surfactants include 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, lauric acid amidopropyl hydroxysulfobetaine, fatty acid amidopropyl betaine, and fatty acid acyl-N-carboxyethyl-N-hydroxy. The non-cyan electrolytic gold plating bath for bump formation according to claim 1, which is one or more selected from ethylethylenediamine alkali salts. The non-cyan electrolytic gold plating bath for bump formation according to claim 1, wherein the crystal adjusting agent is a Tl compound, a Pb compound, or an As compound. A bump forming method for performing electrolytic gold plating on a wafer patterned using the non-cyan electrolytic gold plating bath for bump formation according to claim 1.

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