JP5629065B2 - Electrode forming gold plating bath and electrode forming method using the same - Google Patents

Description

  The present invention relates to a non-cyan electrolytic gold plating bath suitably used for forming an electrode on a semiconductor wafer and a method for forming an electrode using the same. In particular, among electrodes, gold for electrode formation that is suitably used for forming gold bumps suitable for electrode bonding using an anisotropic conductive adhesive and electrode bonding for forming a eutectic with a counterpart metal on a semiconductor wafer. The present invention relates to a plating bath and an electrode forming method using the same.

  In the non-cyan electrolytic gold plating bath, gold sulfite alkali salt or gold ammonium sulfite is generally used as a gold salt. These gold salts, a water-soluble amine that acts as a stabilizer for the gold complex produced from the gold salt, a small amount of each of Tl, Pb, or As compounds as a crystal modifier for the plating film, and an electrolyte A gold plating bath comprising a buffering agent is known.

  Electrodes for use in the electronic circuit board are formed by electrolytic plating using such a gold plating bath. Among them, gold bumps formed on integrated circuits on semiconductor wafers have been widely used in recent years as circuit forming electrodes for semiconductor wafers (see Patent Documents 1 and 2).

  FIG. 3 is a configuration diagram showing an example of a cross section of a conventional gold bump formed on a wafer.

  Formation of gold bumps on a wafer is generally performed as follows. First, a short-axis columnar Al electrode 203 is formed on the wafer 201 by sputtering or the like. As the wafer 201, a silicon wafer or a compound wafer such as GaAs is used. Next, a patterned passivation film 205 is formed on the wafer. An opening 205 a is formed in the passivation film 205 above the Al electrode 203. Thereafter, an UBM (Under Bump Metal) layer 207 made of a film such as TiW is formed by sputtering. The UBM layer 207 covers the passivation film 205 and the Al electrode 203 exposed in the opening 205a. A gold sputtered film 209 is formed on the UBM layer 207, and a mask is formed on the gold sputtered film 209 with a resist film 211. An opening 211 a is formed in the resist film 211 above the Al electrode 203. Gold bumps 213 are formed on the upper surface of the gold sputtered film 209 in the opening 211a of the resist film 211 by electrolytic gold plating. Thereafter, the resist film 211 is removed. Subsequently, the part of the gold sputtered film 209 and the part of the UBM film 207 not covered with the gold bump 213 are removed. As a result, a wafer in which the passivation film 205 is exposed and the gold bumps 213 are formed above the Al electrode 203 is obtained.

  Gold bumps formed on the wafer are bonded to electrodes of a substrate to be bonded to the wafer in a subsequent process (electrode bonding). Electrode bonding includes electrode bonding that uses a film-like anisotropic conductive adhesive in which conductive particles are dispersed, and electrode bonding that forms a eutectic with a counterpart metal.

  In recent years, for the purpose of simplifying the manufacturing process of a semiconductor package and surely performing electrode bonding, the former of thermocompression bonding the film and the substrate using a film-like anisotropic conductive adhesive for electrode bonding Joining methods are frequently used. An anisotropic conductive adhesive is one in which conductive particles such as resin particles coated with gold are uniformly dispersed in an epoxy resin or the like after nickel coating.

  In FIG. 3, reference numeral 213a denotes a gold bump bonding surface on which the gold bump 213 is bonded to the substrate. The gold bump bonding surface 213a has a convex shape with the center protruding upward with respect to the wafer surface. In some cases, the bump bonding surface is concave or the peripheral edge is notched. When the bump bonding surface 213a has these shapes, the conductive particles in the anisotropic conductive adhesive easily fall into the concave portion or the peripheral edge of the bump bonding surface. Therefore, the conductive particles are not uniformly distributed on the gold bump bonding surface 213a but are unevenly distributed on a part of the gold bump bonding surface 213a. As a result, the bonding area between the gold bump bonding surface and the substrate is reduced during bonding, and the bonding force between the gold bump and the substrate is weakened. Therefore, an electrical defect due to disconnection or poor bonding occurs in the subsequent assembly process.

  Therefore, in the case of performing electrode bonding using an anisotropic conductive adhesive, it is necessary to form an electrode having a flat bonding surface.

  Moreover, the hardness of the other metal which forms a eutectic with the electroconductive particle and gold bump in the anisotropic conductive adhesive used for electrode joining cannot be specified uniformly. Therefore, various troubles occur.

For example, when the hardness of the electrode is lower than that of the conductive particles in the anisotropic conductive adhesive, the conductive particles are embedded in the electrode during thermocompression bonding. As a result, the conductive particles are not thermocompression bonded between the electrode and the substrate during electrode bonding, and the electrode bonding between the electrode and the substrate becomes insufficient. On the other hand, when the hardness of the electrode is too high compared to the conductive particles in the anisotropic conductive adhesive, the conductive particles are crushed during thermocompression bonding, and the electrode and the substrate are not joined.
In addition, in the case of electrode bonding that forms a eutectic with the counterpart metal, if the electrode hardness is too high compared to the counterpart metal that forms the eutectic, the electrode cannot sink into the counterpart metal and forms a sufficient eutectic. do not do. As a result, an electrical defect due to disconnection or poor bonding is generated.

  Therefore, when electrode bonding is performed using an anisotropic conductive adhesive or a eutectic formed with a counterpart metal, it is necessary to selectively form electrodes having appropriate hardness.

  When electrodes are formed using a conventional electrolytic gold plating bath, it is difficult to join electrodes corresponding to both a method using an anisotropic conductive adhesive and a method using eutectic formation. That is, it is not possible to obtain an electrode having a desired hardness after the joining surface is kept flat and heat treatment is performed. The desired hardness here is 50 to 120 HV for electrode bonding using an anisotropic conductive adhesive, and 35 to 60 HV for electrode bonding with a eutectic formed with a counterpart metal. This hardness is subjected to heat treatment. The hardness after it is done.

  As described above, the shape and hardness of the electrode greatly affect the bondability between the electrode and the substrate. Therefore, the electrode is required to have a predetermined shape and hardness in addition to excellent electrical conductivity and oxidation resistance.

JP 2007-092156 A JP 2006-322037 A

  The object of the present invention is that the appearance of the plating film is uniform and has a shape suitable for electrode bonding using an anisotropic conductive adhesive or electrode bonding for forming a eutectic with a counterpart metal, and is desired by heat treatment. An object of the present invention is to provide a gold plating bath for forming an electrode for forming an electrode having a hardness. Another object of the present invention is to provide a plating method in which an electrode having a uniform appearance and a predetermined shape and hardness is formed by electrolytic plating using this plating bath.

  As a result of investigations to solve the above-mentioned problems, the present inventor blended a predetermined substituted aromatic compound in a plating bath for forming an electrode, and blended sodium sulfite as a conductive salt, whereby the appearance of the plating film was obtained. Has been found that an electrode having a uniform bonding surface can be obtained. Such an electrode can adjust the hardness after heat treatment arbitrarily within a range of 35 to 120 HV suitable for electrode bonding between the electrode and the substrate.

  The present invention for achieving the above object is described below.

[1]
(A) 1-20 g / L of gold sulfite alkali salt or gold ammonium sulfite as a gold concentration,
(B) One or two or more compounds selected from Tl compounds, Pb compounds, and As compounds have a metal concentration of 0.1 to 100 mg / L,
(C) 5 to 150 g / L of sodium sulfite as a conductive salt;
(D) 1 or 2 or more types of compounds selected from inorganic acid salts, carboxylate salts, and hydroxycarboxylate salts have a salt concentration of 1 to 60 g / L,
(E) one or two or more substituted aromatic compounds selected from benzoic acids, aromatic carboxylic acids, aromatic sulfonic acids, pyridines, and salts thereof are 0.1 to 200 mmol / L;
A gold plating bath for electrode formation containing

  The invention described below is also included in the present invention.

[2]
Benzoic acids are 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6- Dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, 2-aminobenzoic acid, 3- Aminobenzoic acid, 4-aminobenzoic acid, 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 2,4-dinitrobenzoic acid, 2,6-dinitrobenzoic acid, 3,5-dinitrobenzoic acid The gold plating bath for forming an electrode according to [1], which is one or more selected from acids.

[3]
Aromatic carboxylic acids (excluding benzoic acids) are DL-4-hydroxymandelic acid, pyromellitic acid, metanilic acid, 2-hydroxy-m-toluic acid, isovanillic acid, 1-naphthoic acid, 3-hydroxy-2- The gold plating bath for electrode formation according to [1], which is one or more selected from naphthoic acid, 1,4-dihydroxy-2-naphthoic acid, and 3,5-dihydroxy-2-naphthoic acid.

[4]
Aromatic sulfonic acids are 1-naphthol-8-sulfonic acid, 2-naphthol-7-sulfonic acid, 2-naphthol-6,8-disulfonic acid, 2-amino-5-naphthol-7-sulfonic acid, 1 type or 2 or more types selected from 5-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid, gamma acid, naphthalene-1,3,6-trisulfonic acid, methanyl acid, amino J acid, crocenic acid The gold plating bath for electrode formation as described in [1].

[5]
The pyridine is one or more selected from 2-pyridinecarboxylic acid, 3-pyridinecarboxylic acid, 4-pyridinecarboxylic acid, 2-aminopyridine, 3-aminopyridine, and 4-aminopyridine. 1] The gold plating bath for electrode formation as described in 1].

[6]
After the electrode is formed in the opening of the resist film by plating the wafer using the electrode-forming gold plating bath according to any one of [1] to [5], the wafer is heated at 150 to 400 ° C. at 5 ° C. An electrode forming method in which an electrode having a hardness of 35 to 120 HV and a difference in height of a bonding surface within 2 μm is formed on a wafer by performing heat treatment for at least minutes.

[7]
The electrode formation method according to [6], wherein electrolytic gold plating is performed at a current density of 0.2 to 2.0 A / dm ² and a liquid temperature of 40 to 70 ° C.

[8]
The electrode forming method according to [6], wherein the electrode is a gold bump.

  Since the electrode formed using the plating bath of the present invention has a flat joining surface and a predetermined hardness, electrode joining via an anisotropic conductive adhesive or a eutectic with a counterpart metal in a semiconductor manufacturing process Electrode bonding for forming can be performed easily and reliably. In addition, the rate of disconnection and poor bonding is extremely low. In particular, the hardness after heat treatment of the electrode can be controlled to an arbitrary value within a range of 35 to 120 HV suitable for electrode bonding with an anisotropic conductive adhesive or electrode bonding for forming a eutectic with a counterpart metal. Therefore, this plating bath is suitable for forming gold bumps.

  The electrode formed using the plating bath of the present invention has a uniform plating film and is excellent in electrical conductivity, oxidation resistance and the like.

  The electrode formed using the plating bath of the present invention does not swell not only on the bonding surface but also on the side surface of the electrode in contact with the resist film. Therefore, an electrode along the shape of the opening of the resist film can be formed. Accordingly, it is possible to form a prismatic or polygonal electrode having a flat side surface, or a cylindrical electrode having a uniform diameter.

It is a block diagram which shows an example regarding the gold bump cross section formed using the gold plating bath of this invention. 2 is a drawing-substituting photograph by a metallographic microscope showing an appearance of a gold bump in Example 1. FIG. It is a block diagram which shows an example regarding the gold bump cross section formed using the conventional gold plating bath. 4 is a drawing-substituting photograph by a metallographic microscope showing an appearance of a gold bump of Comparative Example 1.

  Hereinafter, the essential components of the gold plating bath for electrode formation 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 gold plating bath for electrode formation of the present invention, a known gold sulfite alkali salt can be used without limitation. Examples thereof include gold (I) sodium sulfite and potassium gold (I) sulfite. These may be used alone or in combination of two or more.

  The compounding quantity of gold sulfite alkali salt or gold ammonium sulfite is 1-20 g / L as gold concentration, and 10-16 g / L is preferable. When it is less than 1 g / L, the thickness of the plating film becomes non-uniform. If it exceeds 20 g / L, there is no problem in the properties of the plating film, but the production cost increases.

(2) Tl compound, Pb compound, As compound (crystal modifier)
Crystal regulators used in the gold plating bath for electrode formation of the present invention include Tl compounds such as thallium formate, thallium malonate, thallium sulfate, and thallium nitrate; lead citrate, lead nitrate, lead alkanesulfonate, etc. Pb compound; As compounds such as diarsenic trioxide are listed. These 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 is 0.1 to 100 mg / L as a metal concentration, preferably 0.5 to 50 mg / L, and particularly preferably 10 to 35 mg / L. If it is less than 0.1 mg / L, the area around the plating and the stability and durability of the plating bath deteriorate. Moreover, the component of a plating bath may decompose | disassemble. When it exceeds 100 mg / L, deterioration around the plating and uneven appearance of the plating film occur.

(3) Sodium sulfite (conductive salt)
In the gold plating bath for electrode formation of the present invention, sodium sulfite is used as a conductive salt. The blending amount of sodium sulfite is 5 to 150 g / L, preferably 10 to 80 g / L, and particularly preferably 30 to 60 g / L. If it is less than 5 g / L, the swelling of the electrode shape is not sufficiently suppressed, and an electrode having a flat joining surface cannot be obtained. In addition, the area around the plating becomes uneven and the plating bath stability deteriorates. As a result, the constituent components of the plating bath may be decomposed. If it exceeds 150 g / L, the limiting current density is lowered, resulting in burnt plating.

(4) Inorganic salt, carboxylic acid, hydroxycarboxylic acid (buffering agent)
A well-known thing can be used as a buffering agent used for the gold plating bath for electrode formation of this invention. Examples thereof include inorganic acid salts such as phosphates and borates, organic acid (carboxylic acid, hydroxycarboxylic acid) salts such as citrate, phthalate, and ethylenediaminetetraacetate.

  The blending amount of the buffer is 1 to 60 g / L, preferably 5 to 40 g / L, and particularly preferably 10 to 30 g / L. If it is less than 1 g / L, the pH is lowered, the plating bath stability is deteriorated, and the constituent components of the plating bath may be decomposed. If it exceeds 60 g / L, the limiting current density is lowered, resulting in burnt plating.

(5) Substituted aromatic compound As the substituted aromatic compound to be blended in the gold plating bath for electrode formation of the present invention, a compound that is dissolved in water at 20 ° C by 0.1 to 200 mmol / L is selected.

For example, 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid Acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, 2-aminobenzoic acid, 3-aminobenzoic acid Acid, 4-aminobenzoic acid, 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 2,4-dinitrobenzoic acid, 2,6-dinitrobenzoic acid, 3,5-dinitrobenzoic acid, etc. Benzoic acids and salts thereof,
DL-4-hydroxymandelic acid, pyromellitic acid, metanilic acid, 2-hydroxy-m-toluic acid, isovanillic acid, 1-naphthoic acid, 3-hydroxy-2-naphthoic acid, 1,4-dihydroxy-2-naphthoic acid Acids, aromatic carboxylic acids such as 3,5-dihydroxy-2-naphthoic acid (excluding benzoic acids) and salts thereof,
1-naphthol-8-sulfonic acid, 2-naphthol-7-sulfonic acid, 2-naphthol-6,8-disulfonic acid, 2-amino-5-naphthol-7-sulfonic acid, 1,5-naphthalenedisulfonic acid, Aromatic sulfonic acids such as 2,7-naphthalenedisulfonic acid, gamma acid, naphthalene-1,3,6-trisulfonic acid, metanilic acid, amino J acid, crocenic acid, and salts thereof;
Examples thereof include pyridines such as 2-pyridinecarboxylic acid, 3-pyridinecarboxylic acid, 4-pyridinecarboxylic acid, quinolinic acid, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, and salts thereof.

  The compounding quantity of a substituted aromatic compound is 0.1-200 mmol / L, and 0.2-150 mmol / L is preferable. If it is less than 0.1 mmol / L, an electrode having a flat joining surface cannot be obtained. If it exceeds 200 mmol / L, it will not dissolve in the plating solution, or the critical current density will decrease, resulting in burnt plating.

  By adjusting the compounding quantity of a substituted aromatic compound within the said range, it becomes possible to adjust the hardness of the electrode after heat processing in the range of 35-120HV. In addition, the hardness of an electrode becomes high, so that there are many compounding quantities of a substituted aromatic compound.

  In the gold plating bath for electrode formation of the present invention, other components such as a pH adjuster may be appropriately used within a range not impairing the object of the present invention. Examples of the pH adjuster include sulfuric acid, aqueous sulfite, phosphoric acid and the like as acid, and sodium hydroxide, aqueous ammonia and the like as alkali.

  In order to form an electrode on a semiconductor wafer by plating using the gold plating bath for electrode formation of the present invention, a plating operation may be performed according to a conventional method. Hereinafter, a method for forming gold bumps on a semiconductor wafer using the gold plating bath for electrode formation of the present invention will be described.

  FIG. 1 is a configuration diagram showing an example of a cross section of a gold bump formed on a wafer using the electrode forming gold plating bath of the present invention. In FIG. 1, reference numeral 11 denotes a wafer, which is a silicon wafer or a known compound wafer such as GaAs. First, a short-axis columnar Al electrode 13 is formed on the wafer 11 by sputtering or the like. Next, a patterned passivation film 15 is formed. An opening 15 a is formed in the passivation film 15 above the Al electrode 13. Thereafter, the UBM layer 17 made of a film such as TiW is formed by sputtering. The UBM layer 17 covers the passivation film 15 and the Al electrode 13 exposed through the opening 15a. A gold sputtered film 19 is formed on the UBM layer 17, and a mask is formed on the gold sputtered film 19 with a resist film 21. An opening 21 a is formed in the resist film 21 above the Al electrode 13. The said process can be performed by a well-known method. The wafer on which the opening 21a is formed is plated using the electrode forming plating bath of the present invention. Thereby, a gold bump 23 is formed in the opening 21 a of the resist film 21. Thereafter, the resist film 21 is removed by a known method, and then the portion of the gold sputtered film 19 and the portion of the UBM film 17 that are not covered with the gold bumps 23 are removed by a known method. As a result, a wafer on which the passivation film 15 is exposed and the gold bumps 23 are formed is obtained.

  The gold bump bonding surface 23a formed as described above is flat, and the height difference (described later) of the bump bonding surface is 2 μm or less.

  A novolac positive photoresist can be used as the masking agent. As a commercial item, LA-900, HA-900 (above, Tokyo Ohka Kogyo Co., Ltd. make) etc. can be mentioned, for example.

  The plating temperature is usually 40 to 70 ° C, preferably 50 to 65 ° C. When the plating bath temperature is outside the range of 40 to 70 ° C., the plating film may be difficult to deposit. In addition, the plating bath may become unstable and the plating bath components may be decomposed.

The set current density used for plating has an appropriate range depending on conditions such as the composition and temperature of the plating solution, and may be determined as appropriate. For example, the gold concentration is 2.0 A / dm ² or less, preferably 0.2 to 1.2 A / dm ² under the conditions of a plating bath temperature of 8 to 15 g / L and 60 ° C. When the set current density is out of the above range, workability may be deteriorated. Moreover, an abnormality may occur in the appearance of the plating film and the characteristics of the plating film. Furthermore, the plating bath may become extremely unstable, and decomposition of the plating bath components may occur.

  The pH of the gold plating bath for electrode formation of the present invention is 7.0 or more, and preferably 7.2 to 10.0. If it is less than 7.0, the plating bath becomes extremely unstable, which may cause decomposition of the components of the plating bath. If it exceeds 10.0, the mask material may be dissolved in the plating bath and a desired gold bump may not be formed.

  The gold plating bath for electrode formation of the present invention has two turns (one turn when the entire amount of gold in the plating bath is consumed for plating) by replenishing and managing the gold source and other components constituting the plating bath. ) You can also use the above.

  In the gold plating bath for electrode formation of the present invention, any material to be plated can be used as long as the substrate is metallized and can be electrically connected. It can be particularly suitably used when gold bumps are formed on a silicon wafer patterned using a novolac positive photoresist as a mask material or a compound wafer circuit such as a Ga / As wafer.

  Next, heat treatment is performed on the wafer on which the electrodes are formed. The heat treatment is performed by heating at 150 to 400 ° C. for 5 minutes or more. More preferable heat treatment is performed by heating at 200 to 350 ° C. for 20 to 30 minutes. The heat treatment is performed using a fine oven or the like that can maintain the interior of the chamber at a set temperature for a certain period of time. By this heat treatment, the hardness of the electrode becomes 35 to 120 HV.

  EXAMPLES Next, although an Example is given and this invention is demonstrated concretely, this invention is not limited by these Examples.

(Examples 1 to 49, Comparative Examples 1 to 10)
A non-cyan electrolytic gold plating bath was prepared according to the formulation shown in Tables 1-6. The unit of the blending concentration of each raw material is (g / L) unless otherwise specified. However, Na ₃ Au (SO ₃ ) ₂ indicates the concentration of the gold element.

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 ) was used. A silicon wafer having the above bump openings is immersed in 1 L of each plating bath maintained at 60 ° C., and plated at 0.8 A / dm ² for 35 minutes to form a plating film having a thickness of 18 μm. It was. Note that the current efficiency of the non-cyan electrolytic gold plating bath is usually 100% under steady plating operation conditions.

  Thereafter, the masking agent is removed, and the following method and criteria for the shape of the formed bump, bath stability, plating film appearance, and film hardness (after non-heat treatment, 200 ° C. × 30 minutes, 300 ° C. × 30 minutes heat treatment) Evaluation was performed. The results are shown in Tables 1-6.

[Evaluation of bump shape (μm)]
As shown in FIG. 1, using a novolac positive photoresist on a silicon wafer, patterning having a square opening with a side of 100 μm was performed. After plating using an electrolytic gold plating bath, a novolak positive photoresist was dissolved with methyl ethyl ketone. About the obtained gold bump, the highest point of the bump bonding surface (maximum point of the distance between the wafer surface and the bump bonding surface) and the lowest point of the bump bonding surface (with the wafer surface) using a Keyence Corporation laser microscope VK-9710 The difference in the minimum distance) from the bump bonding surface was measured as a height difference and used as an index of smoothness. In general, the height difference required for bump plating is 3 μm or less and preferably 2 μm or less.

[Bath stability]
The state of the plating bath after plating the object to be plated was observed and evaluated according to the following criteria.
X: Precipitation of gold was observed in the plating bath at a level that can be seen with the naked eye.
○: 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 observed and evaluated according to the following criteria.
X: The color tone is red, dendrite-like precipitation is observed, unevenness is observed, or burns are generated.
○: Uniform appearance.

[Film hardness (Vickers hardness; HV)]
The film hardness (non-heat-treated, after heat treatment at 200 ° C. for 30 minutes, after heat treatment at 300 ° C. for 30 minutes) of the gold bump at a specific part formed on the object to be plated is measured with a micro hardness tester HM-221 manufactured by Mitutoyo Corporation. Measured with In the measurement, a square bump with a side of 100 μm was used, and the measurement conditions were based on the condition that the measurement indenter was held at 25 gf load for 10 seconds.

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

(Comparative Example 9)
The substituted aromatic compound A of Example 1: 50 (mmol / L) was changed to propionic acid (aliphatic carboxylic acid) 100 (mmol / L), and a plating film was formed according to Example 1. The film hardness of the gold bump obtained (after heat treatment at 200 ° C. for 30 minutes) is 55 HV, (after heat treatment at 300 ° C. for 30 minutes) is 51 HV, the height difference is 3.7 μm, and the plating film has a non-uniform appearance. It was.

(Comparative Example 10)
The substituted aromatic compound A of Example 1: 50 (mmol / L) was changed to hydroxymethanesulfonic acid (aliphatic sulfonic acid) 100 (mmol / L), and a plating film was formed according to Example 1. The film hardness of the gold bump obtained (after heat treatment at 200 ° C. for 30 minutes) was 52 HV, (after heat treatment at 300 ° C. for 30 minutes) was 46 HV, and the height difference was 4.0 μm, and the plating film had a non-uniform appearance. .

  The height difference of the bonding surfaces of the gold bumps (Examples 1 to 49) formed by using the gold plating bath for electrode formation of the present invention was 2 μm or less. On the other hand, the height difference of the bonding surfaces of the gold bumps (Comparative Examples 1, 9, and 10) formed without using the electrode-forming gold plating bath of the present invention exceeded 2 μm.

  The hardness after heat treatment of the gold bumps (Examples 1 to 49) formed using the electrode-forming gold plating bath of the present invention was 35 to 120 HV. Moreover, the hardness after heat processing could be arbitrarily selected in the range of 35-120HV by changing the density | concentration of a substituted aromatic compound.

The plating film appearance of the gold bumps (Examples 1 to 49) formed using the electrode-forming gold plating bath of the present invention was uniform and good. On the other hand, the appearance of the plating film of the gold bumps (Comparative Examples 1 to 8) formed without using the electrode-forming gold plating bath of the present invention has a red color tone, dendrite-like precipitation, irregularities are observed, or burns are observed. It has occurred.

11 Wafer 13 Al Electrode 15 Passivation Film 15a Passivation Film Opening 17 UBM Layer 19 Gold Sputtered Film 21 Resist Film 21a Resist Film Opening 23 Gold Bump 23a Gold Bump Bonding Surface 201 Wafer 203 Al Electrode 205 Passivation Film 205a Passivation Film 207 UBM layer 209 Sputtered gold film 211 Resist film 211a Resist film opening 213 Gold bump 213a Gold bump bonding surface

Claims (4)

(A) 1-20 g / L of gold sulfite alkali salt or gold ammonium sulfite as a gold concentration,
(B) One or two or more compounds selected from Tl compounds, Pb compounds, and As compounds have a metal concentration of 0.1 to 100 mg / L,
(C) 5 to 150 g / L of sodium sulfite as a conductive salt;
(D) 1 or 2 or more types of compounds selected from inorganic acid salts, carboxylate salts, and hydroxycarboxylate salts have a salt concentration of 1 to 60 g / L,
(E) 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxy Benzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, 2-aminobenzoic acid, 3-amino Benzoic acid, 4-aminobenzoic acid, DL-4-hydroxymandelic acid, pyromellitic acid, metanilic acid, 2-hydroxy-m-toluic acid, isovanillic acid, 1-naphthoic acid, 3-hydroxy-2-naphthoic acid, 1,4-dihydroxy-2-naphthoic acid, 3,5-dihydroxy-2-naphthoic acid, 1-naphthol-8-sulfonic acid, 2-naphtho 7-sulfonic acid, 2-naphthol-6,8-disulfonic acid, 2-amino-5-naphthol-7-sulfonic acid, 1,5-naphthalenedisulfonic acid, 2,7-naphthalenedisulfonic acid, gamma acid, Naphthalene-1,3,6-trisulfonic acid, metanilic acid, amino J acid, crocenic acid, 2-pyridinecarboxylic acid, 3-pyridinecarboxylic acid, 4-pyridinecarboxylic acid, 2-aminopyridine, 3-aminopyridine, 0.1-200 mmol / L of one or two or more substituted aromatic compounds selected from 4-aminopyridine and salts thereof;
A gold plating bath for electrode formation containing By plating a wafer using the gold plating bath for electrode formation according to claim 1, after forming an electrode in the opening of the resist film, the wafer is heat-treated at 150 to 400 ° C. for 5 minutes or more, An electrode forming method in which an electrode having a hardness of 35 to 120 HV and a difference in height of a bonding surface within 2 μm is formed on a wafer. The electrode forming method according to claim 2 , wherein electrolytic gold plating is performed at a current density of 0.2 to 2.0 A / dm ² and a liquid temperature of 40 to 70 ° C. The electrode forming method according to claim 2 , wherein the electrode is a gold bump.