WO2021193696A1 - Solution d'électrodéposition et procédé d'électrodéposition - Google Patents

Solution d'électrodéposition et procédé d'électrodéposition Download PDF

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WO2021193696A1
WO2021193696A1 PCT/JP2021/012153 JP2021012153W WO2021193696A1 WO 2021193696 A1 WO2021193696 A1 WO 2021193696A1 JP 2021012153 W JP2021012153 W JP 2021012153W WO 2021193696 A1 WO2021193696 A1 WO 2021193696A1
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acid
surfactant
plating
plating solution
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PCT/JP2021/012153
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English (en)
Japanese (ja)
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康司 巽
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三菱マテリアル株式会社
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Priority claimed from JP2021046364A external-priority patent/JP2021155850A/ja
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Publication of WO2021193696A1 publication Critical patent/WO2021193696A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/30—Electroplating: Baths therefor from solutions of tin
    • C25D3/32—Electroplating: Baths therefor from solutions of tin characterised by the organic bath constituents used
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/60—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of tin
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/12—Semiconductors

Definitions

  • the present invention relates to an electrolytic plating solution and an electrolytic plating method for forming a tin or tin alloy plating film. More specifically, the present invention relates to an electrolytic plating solution and an electrolytic plating method used for tin or tin alloy plating suitable for forming solder bumps for semiconductor wafers and printed circuit boards.
  • This application claims priority based on Japanese Patent Application No. 2020-058073 filed in Japan on March 27, 2020 and Japanese Patent Application No. 2021-46364 filed in Japan on March 19, 2021. Is used here.
  • a device that performs electrolytic plating is generally an anode (hereinafter, may be simply referred to as plating solution) arranged to face each other in a plating tank containing an electrolytic plating solution (hereinafter, may be simply referred to as plating solution).
  • An anode) and a semiconductor wafer or substrate which is a member to be plated connected to the cathode (cathode) are provided, and a voltage is applied to the anode and the member to be plated.
  • a plating film is formed on the surface of the member to be plated.
  • the anode used in this electroplating apparatus can be roughly divided into a soluble anode and an insoluble anode.
  • platinum (Pt) and platinum-coated titanium (Pt) are used as anodes in order to suppress the reaction of the plating solution components (metal components noble than additives and tin) on the anode surface.
  • An insoluble anode made of / Ti) or iridium oxide (IrO 2 ) or the like is generally used.
  • the electrolysis reaction of water which is represented by the following reaction formula, occurs on the surface of the anode during electrolysis.
  • the oxygen gas (air bubbles) generated on the surface of the anode is desorbed from the surface of the anode and released into the plating solution.
  • Oxygen bubbles released into the plating solution disappear by floating in the plating solution and then reaching the liquid surface to defoam or dissolving in the plating solution as a dissolved gas.
  • the bubbles adhere to the member to be plated connected to the cathode (cathode) before the bubbles disappear they are likely to prevent the precipitation of plating and cause pit defects, and are incorporated into the plating film. There was a problem that it was easy to cause voids.
  • the solder bump is formed on the semiconductor wafer in the horizontal plating tank 1, it faces the insoluble anode 3 arranged horizontally in the plating solution 2. Then, the semiconductor wafer (member to be plated) 4 horizontally connected to the cathode is arranged above the anode. During the plating, the semiconductor wafer 4 rotates in a horizontal state. Further, the plating solution 2 is circulated by the suction port 1a, the return port 1b, and the circulation pump 1c provided at the bottom of the plating tank 1, respectively. The bubbles 8 desorbed from the surface of the anode 3 float and adhere to the surface of the semiconductor wafer 4. Therefore, as shown in the enlarged view of FIG.
  • Patent Document 1 (Claim 1, paragraphs [0001] to []. 0003]).
  • the bump electrode has become finer to a diameter of 100 ⁇ m or less, and the depth (depth / diameter) of the via to the diameter of the via in the resist layer has become higher in aspect ratio. ) Has become difficult to desorb depending on the device conditions. Therefore, it is necessary to reduce the occurrence rate of pit defects due to the growth of the plating deposit layer due to the generated bubbles and the voids in the bump after the plating deposit layer has grown.
  • the method of plating in a decompressed plating tank is one method of reducing the occurrence rate of pit defects and voids, but the above problem is still unsolved by this plating method. ..
  • An object of the present invention is an electrolytic plating solution and an electrolytic plating method for reducing the occurrence rate of pit defects in bumps and voids in bumps, which are caused by the fact that plating does not precipitate due to bubbles generated in the plating solution. Is to provide.
  • the present inventor has made oxygen bubbles generated on the surface of the anode (anode) by containing a surfactant having a specific structure in the plating bath. Before being released into the plating solution, it is aggregated on the surface of the anode and enlarged, and the enlarged oxygen bubbles are quickly carried to the liquid surface by buoyancy, so that the oxygen bubbles do not disperse in the plating solution. As a result, it has been found that the adhesion of bubbles having a diameter smaller than the via diameter to the surface of the member to be plated connected to the cathode is reduced, and the occurrence of pit defects and voids is dramatically reduced. Reached.
  • a first aspect of the present invention is an electrolytic plating solution containing a soluble salt (A) containing at least a stannous salt, an acid or a salt thereof (B), and a surfactant (C), wherein the anode current is present.
  • This electroplating solution is characterized in that the maximum value of the particle size distribution of bubbles released from the insoluble anode when electrolyzed at a density of 0.7 A / dm 2 is 150 ⁇ m or more.
  • the maximum value of the particle size distribution may be 200 ⁇ m or more.
  • the upper limit is not particularly limited, but may be, for example, 1000 ⁇ m or less.
  • a second aspect of the present invention is the invention according to the first aspect, wherein the surfactant (C) is a polyoxyethylene polyoxypropylene block polymer (PO-) having a polyoxypropylene (PO) terminal.
  • EO-PO) nonionic surfactant the EO ratio in the block polymer (PO-EO-PO) is in the range of 35% or more and 50% or less in terms of molar ratio, and the nonionic surfactant.
  • An electrolytic plating solution having a mass average molecular weight in the range of 3000 or more and 5000 or less.
  • the EO ratio may be in the range of 35% or more and 45% or less in terms of molar ratio, or may be in the range of 40% or more and 45% or less.
  • the mass average molecular weight may be in the range of 3000 or more and 4500 or less, or may be in the range of 3500 or more and 4500 or less.
  • a third aspect of the present invention is the invention according to the first aspect, wherein the surfactant (C) is an electrolytic plating solution which is an amphoteric surfactant of alkylsulfobetaine or alkylhydroxysulfobetaine. ..
  • a fourth aspect of the present invention is the invention according to any one of the first to third aspects, wherein the content of the surfactant (C) is 0.5 g / L or more and 10 g / L. It is an electrolytic plating solution in the range of L or less. The content may be in the range of 1 g / L or more and 5 g / L or less.
  • a fifth aspect of the present invention is to supply the electroplating solution according to any one of the first to fourth aspects to a plating tank in which an insoluble anode is arranged so as to face a member to be plated connected to a cathode.
  • This is a method of electrolytically plating the member to be plated. It is preferable that the facing surfaces are substantially parallel to each other.
  • a sixth aspect of the present invention is the invention according to the fifth aspect, which is an electrolytic plating method in which electrolytic plating is performed using a plating tank in which the member to be plated and the insoluble anode are horizontally arranged.
  • the vertical relationship between the member to be plated and the insoluble anode is not limited, but it is preferable that the insoluble anode is located on the lower side and the member to be plated is located on the upper side.
  • the particle size distribution of the bubbles 8 released from the insoluble anode 3 is maximized. Since the value is 150 ⁇ m or more, it is difficult for bubbles 8 to enter the via 6 of the resist layer 5 formed by the resist pattern. Since the plating deposit layer grows to become bumps 7 in a state where the bubbles 8 do not adhere to the plating deposit layer in the via 6, the occurrence rate of pit defects and voids in the bumps caused by the non-precipitation of plating can be determined. Can be reduced.
  • the same elements as those shown in FIG. 2 are designated by the same reference numerals.
  • the surfactant (C) is a nonionic interface of a polyoxyethylene polyoxypropylene block polymer (PO-EO-PO) having a polyoxypropylene (PO) terminal. It is an activator, and the EO ratio in the block polymer (PO-EO-PO) is in the range of 35% or more and 50% or less in terms of molar ratio, and the mass average molecular weight of the nonionic surfactant is 3000 or more and 5000 or less. Is the range of. Since such a surfactant has a property intermediate between hydrophilicity and hydrophobicity, it has a strong adsorptive power to the surface of an insoluble anode and the surface of oxygen bubbles.
  • the surfactant (C) is an amphoteric surfactant of alkylsulfobetaine or alkylhydroxysulfobetaine, the adsorption force on the surface of the insoluble anode and the surface of oxygen bubbles. Has the effect of being strong.
  • the surfactant (C) is insoluble because the content of the surfactant (C) is in the range of 0.5 g / L or more and 10 g / L or less. A sufficient amount can be adsorbed on the surface of the anode and the surface of oxygen bubbles. As a result, the occurrence rate of pit defects and voids can be further reduced.
  • the object to be plated is arranged to face the insoluble anode 3.
  • electrolytic plating is performed without the bubbles 8 being taken into the via. As a result, this plating method can reduce the occurrence rate of pit defects and voids.
  • the electroplating method of the sixth aspect of the present invention since the member 4 to be plated and the insoluble anode 3 are arranged horizontally, the bubbles 8 discharged from the insoluble anode 3 reach the upper member 4 to be plated. However, since the bubbles 8 are enormous, electrolytic plating is performed without the bubbles 8 being taken into the vias 6 of the resist layer 5 formed on the member 4 to be plated. As a result, this plating method can reduce the occurrence rate of pit defects and voids.
  • FIG. 5 (a) is a cross-sectional view of the member to be plated before plating
  • FIG. 2 (b) is a cross-sectional view of the member to be plated in which normal mushroom-shaped bumps are formed.
  • FIG. 2 (e) is a cross-sectional view of the member to be plated in which voids are formed.
  • This plating solution is used as a material for forming a plating film of tin or a tin alloy used as a solder bump for a semiconductor wafer or a printed circuit board.
  • the tin or tin alloy plating solution of the present embodiment is an electrolytic plating solution containing a soluble salt (A) containing at least a first tin salt, an acid or a salt thereof (B), and a surfactant (C).
  • A soluble salt
  • B acid or a salt thereof
  • C surfactant
  • the feature is that when the anode current density is electrolyzed at 0.7 A / dm 2 , the maximum particle size distribution of bubbles released from the insoluble anode is 150 ⁇ m or more, and may be 200 ⁇ m or more.
  • the upper limit is not particularly limited, but may be, for example, 1000 ⁇ m or less.
  • the reason why the anode current density is limited to 0.7 ASD (A / dm 2 ) is that pit defects and voids tend to become apparent at 0.7 ASD or more.
  • the maximum particle size distribution of bubbles discharged from the insoluble anode is set to 150 ⁇ m or more because the via diameter of the resist layer formed by the resist pattern of the member to be plated is generally in the range of 10 ⁇ m or more and less than 100 ⁇ m.
  • the tin alloy of the present embodiment is an alloy of tin and one or more predetermined metals selected from silver, copper, bismuth, nickel, antimony, indium, and zinc.
  • binary alloys such as tin-silver alloys, tin-copper alloys, tin-bismas alloys, tin-nickel alloys, tin-antimon alloys, tin-indium alloys, and tin-zinc alloys, tin-copper-bismus, etc.
  • ternary alloys such as tin-copper-silver alloys.
  • the soluble salt (A) of the present embodiment is the stannous salt alone, or one selected from the group consisting of the stannous salt and silver, copper, bismuth, nickel, antimony, indium, and zinc. It consists of a mixture of two or more metal salts.
  • the soluble salt (A) of the present embodiment contains Sn 2+ alone in the plating solution, or together with Sn 2+ , Ag + , Cu + , Cu 2+ , Bi 3+ , Ni 2+ , It contains one or more arbitrary soluble salts that generate various metal ions such as Sb 3+ , In 3+ , and Zn 2+.
  • the soluble salt include oxides of these metals, halides, the metal salt of an inorganic acid or an organic acid, and the like.
  • metal oxides include stannous oxide, silver oxide, copper oxide, nickel oxide, bismuth oxide, antimony oxide, indium oxide, and zinc oxide.
  • metal halides include stannous chloride, bismuth chloride, bismuth bromide, cuprous chloride, cupric chloride, nickel chloride, antimony chloride, indium chloride, and zinc chloride.
  • Metal salts of inorganic or organic acids include copper sulfate, stannous sulfate, bismuth sulfate, nickel sulfate, antimony sulfate, bismuth nitrate, silver nitrate, copper nitrate, antimonyate nitrate, indium nitrate, nickel nitrate, zinc nitrate, and copper acetate.
  • the content of the first tin salt in the plating solution of the present embodiment is preferably in the range of 5 g / L or more and 200 g / L or less, more preferably 20 g / L or more and 100 g / L or less in terms of the amount of tin. Is the range of.
  • the acid or salt (B) thereof of the present embodiment is one or more acids selected from organic acids, inorganic acids, and salts thereof, or salts thereof.
  • organic acid include organic sulfonic acids such as alkane sulfonic acid, alkanol sulfonic acid and aromatic sulfonic acid, and aliphatic carboxylic acids.
  • inorganic acid include borofluoric acid, silicate hydrofluoric acid, sulfamic acid, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid and the like.
  • These salts are alkali metal salts, alkaline earth metal salts, ammonium salts, amine salts, sulfonates and the like.
  • Organic sulfonic acids are more preferable from the viewpoint of solubility of metal salts and ease of wastewater treatment.
  • 2-hydroxyethane-1-sulfonic acid 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, etc.
  • 1- Hydroxypropane-2-sulfonic acid 3-hydroxypropane-1-sulfonic acid
  • 4-hydroxybutane-1-sulfonic acid 2-hydroxyhexane-1-sulfonic acid
  • 2-hydroxydecane-1-sulfonic acid 2- Hydroxidodecane-1-sulfonic acid and the like
  • the aromatic sulfonic acid is basically benzenesulfonic acid, alkylbenzenesulfonic acid, phenolsulfonic acid, naphthalenesulfonic acid, alkylnaphthalenesulfonic acid and the like. Specifically, 1-naphthalene sulfonic acid, 2-naphthalene sulfonic acid, toluene sulfonic acid, xylene sulfonic acid, p-phenol sulfonic acid, cresol sulfonic acid, sulfosalicylic acid, nitrobenzene sulfonic acid, sulfobenzoic acid, diphenylamine-4- Examples include sulfonic acid.
  • aliphatic carboxylic acid examples include acetic acid, propionic acid, butyric acid, citric acid, tartaric acid, gluconic acid, sulfosuccinic acid, and trifluoroacetic acid.
  • the content of the acid selected from the organic acid and the inorganic acid or the salt (B) thereof in the plating solution of the present embodiment is not particularly limited, but is, for example, in the range of 10 g / L or more and 500 g / L or less, preferably 50 g. It is preferably in the range of / L or more and 300 g / L or less.
  • surfactant (C) examples of the surfactant (C) used in the plating solution of the present embodiment include a nonionic surfactant and an amphoteric surfactant. These two types of surfactants may be used alone or in combination.
  • the nonionic surfactant contains polyoxyethylene (EO) and polyoxypropylene (PO), and the terminal is polyoxypropylene (PO).
  • Polyoxyethylene polyoxypropylene block polymer (PO-EO-PO) Can be used.
  • the EO ratio in this block polymer (PO-EO-PO) is in the range of 35% or more and 50% or less in terms of molar ratio, and the mass average molecular weight of this nonionic surfactant is in the range of 3000 or more and 5000 or less. ..
  • the hydrophobic tendency of the surfactant becomes strong, and when it exceeds 50%, the hydrophilic tendency of the surfactant becomes strong, and in any case, it is released from the insoluble anode. It becomes difficult to make the maximum value of the particle size distribution of bubbles 150 ⁇ m or more.
  • the mass average molecular weight of the surfactant is less than 3000, the effect of suppressing the precipitation of tin or a tin alloy may not be sufficient, and if it exceeds 5000, the effect of suppressing the precipitation of tin or a tin alloy becomes too strong, and uniform plating is performed. The film may not be formed.
  • the EO ratio is preferably in the range of 35% or more and 45% or less in terms of molar ratio, and more preferably in the range of 40% or more and 45% or less.
  • the mass average molecular weight is preferably in the range of 3000 or more and 4500 or less, and more preferably in the range of 3500 or more and 4500 or less.
  • the nonionic surfactant of this embodiment is represented by the following formula (1).
  • a, b, and c are the number of repeating units of (PO), (EO), and (PO) in the block polymer, respectively.
  • ethylenediamine polyoxyethylene obtained by addition polymerization of polyoxyethylene (EO) and polyoxypropylene (PO) to ethylenediamine and having polyoxypropylene (PO) at the end.
  • Polyoxypropylene block polymer can also be used.
  • the EO ratio in this block polymer is in the range of 35% or more and 50% or less in terms of molar ratio, and the mass average molecular weight of this surfactant is in the range of 3000 or more and 5000 or less.
  • the hydrophobic tendency of the surfactant becomes strong, and when it exceeds 50%, the hydrophilic tendency of the surfactant becomes strong, and in any case, the particles of bubbles released from the insoluble anode. It becomes difficult to set the maximum diameter distribution value to 150 ⁇ m or more.
  • the mass average molecular weight of the surfactant is less than 3000, the effect of suppressing the precipitation of tin or a tin alloy may not be sufficient, and if it exceeds 5000, the effect of suppressing the precipitation of tin or a tin alloy becomes too strong, and uniform plating is performed. The film may not be formed.
  • the nonionic surfactant of the present embodiment is also represented by the following formula (2).
  • m and n are the number of repeating units of (PO), (EO) and (PO) in the block polymer, respectively.
  • the nonionic surfactant represented by the above structure is a block polymer containing polyoxyethylene (EO) and polyoxypropylene (PO), and when polyoxypropylene (PO) is present at the terminal, the surfactant is hydrophobic. It has the effect of strengthening the adsorption force to the insoluble anode and the surface of oxygen bubbles.
  • this block polymer when polyoxyethylene (EO) is present at the terminal, there causes a problem that the adsorption force to the insoluble anode and the surface of oxygen bubbles is weakened because the hydrophilicity of the surfactant is strengthened.
  • the maximum value of the particle size distribution of the bubbles released from the insoluble anode is set to 150 ⁇ m or more.
  • the EO ratio can be measured by comparing the intensity ratios of polyoxyethylene (EO) and polyoxypropylene (PO) using NMR (Nuclear Magnetic Resonance). This measuring method is described in detail in "Surfactant Analysis Method” edited by Surfactant Analysis Study Group, Koshobo (published in 1975), and the like.
  • the mass average molecular weight can be measured by comparing with a commercially available standard substance using Size Exclusion Chromatography (SEC).
  • the content of the nonionic surfactant in the plating solution should be in the range of 0.5 g / L or more and 10 g / L or less, and the EO ratio should be in the range of 35% or more and 50% or less in terms of molar ratio.
  • the mass average molecular weight of the surfactant is in the range of 3000 or more and 5000 or less in order to more accurately set the maximum value of the particle size distribution of bubbles released from the insoluble anode to 150 ⁇ m or more. preferable. It is more preferable that the content of the nonionic surfactant in the plating solution is in the range of 1 g / L or more and 5 g / L or less.
  • the maximum value of the particle size distribution of bubbles discharged from the insoluble anode may not be 150 ⁇ m or more, and if it exceeds 10 g / L, a uniform plating film is formed. It may not be formed.
  • the nonionic surfactant of the present embodiment can be used by purifying a commercially available product as EP-461 manufactured by Aoki Oil & Fat Industry Co., Ltd. Further, the surfactant of the present embodiment can be produced by a known technique. For example, it can be synthesized by adjusting the molecular weight of the raw material polyoxyethylene in US Pat. No. 4,726,909 and the reaction amount of the polyoxypropylene to be added.
  • An amphoteric surfactant can be used as the surfactant (C) of the present embodiment.
  • alkyl sulfobetaine or alkyl hydroxysulfobetaine can be used.
  • the alkylsulfobetaine is represented by the following formula (3).
  • lauryl sulfobetaine, stearyl sulfobetaine and the like can be mentioned.
  • the alkylhydroxysulfobetaine is represented by the following formula (4).
  • R represents an alkyl group, respectively.
  • the carbon number of R of alkylsulfobetaine or alkylhydroxysulfobetaine is preferably in the range of 10 or more and 22 or less, respectively.
  • the content of these amphoteric surfactants in the electrolytic plating solution is in the range of 0.5 g / L or more and 10 g / L or less, the maximum value of the particle size distribution of bubbles released from the insoluble anode is determined. It is preferable to make it more accurately 150 ⁇ m or more. It is more preferable that the content of the amphoteric surfactant in the electrolytic plating solution is in the range of 1 g / L or more and 5 g / L or less.
  • the surfactant (C) of the present embodiment has the above-mentioned characteristics, when the anode current density is electrolyzed with, for example, 0.7 ASD, the maximum particle size distribution of bubbles released from the insoluble anode is 150 ⁇ m or more. To. As a result, even in the via where the bump electrode is miniaturized to a diameter of 100 ⁇ m or less, it is difficult for air bubbles to enter the via of the resist layer, and the growth of the plating deposition layer in the via is smoothly performed without being disturbed by the air bubbles. Less likely to cause defects. In addition, it is difficult to generate voids in the plating deposit layer in the via. As a result, the height of the bumps formed when the plating deposit layer is reflowed becomes uniform, and the voids in the bumps are reduced.
  • the maximum particle size distribution of bubbles released from the insoluble anode can be set to 150 ⁇ m or more when the anode current density is electrolyzed at 0.7 A / dm 2. ..
  • the plating solution of the present embodiment may further contain an antioxidant, a complexing agent, a pH adjusting agent, and a brightening agent, if necessary.
  • antioxidant is intended to prevent the oxidation of Sn 2+ in the plating solution.
  • antioxidants include ascorbic acid or a salt thereof, pyrogallol, hydroquinone, fluoroglusinol, trihydroxybenzene, catechol, cresol sulfonic acid or a salt thereof, catechol sulfonic acid or a salt thereof, hydroquinone sulfonic acid or a salt thereof, and the like.
  • hydroquinone sulfonic acid or a salt thereof is preferable in an acidic bath
  • ascorbic acid or a salt thereof is preferable in a neutral bath.
  • the amount of the antioxidant added to the plating solution of the present embodiment is generally in the range of 0.01 g / L or more and 20 g / L or less, preferably in the range of 0.1 g / L or more and 10 g / L or less, more preferably 0. It is in the range of 1 g / L or more and 5 g / L or less.
  • the plating solution of the present embodiment can be applied to a tin or tin alloy plating bath in any pH range such as acidic, weakly acidic, and neutral.
  • Sn 2+ ions are stable in strong acidity (pH: ⁇ 1), but tend to cause white precipitation in the vicinity of acidic to neutral (pH: 1 to 7). Therefore, when the tin or tin alloy plating solution of the present embodiment is applied to a tin plating bath near neutrality, it is necessary to add a complexing agent for tin for the purpose of stabilizing Sn 2+ ions. preferable.
  • oxycarboxylic acid As the complexing agent for tin, oxycarboxylic acid, polycarboxylic acid, and monocarboxylic acid can be used. Specific examples include gluconic acid, citric acid, glucoheptonic acid, gluconolactone, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, succinic acid, glycolic acid, malic acid, tartrate acid, or salts thereof. And so on. Preferred are gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptlactone, or salts thereof.
  • the complexing agent for tin one type may be used alone, or two or more types may be used in combination.
  • the amount of the complexing agent for tin added to the plating solution of the present embodiment is generally 0.001 mol or more and 10 mol or less with respect to 1 mol of tin in the soluble tin salt compound contained in the tin or tin alloy plating solution. It is preferably in the range of. It is more preferably 0.01 mol or more and 5 mol or less, and even more preferably 0.5 mol or more and 2 mol or less.
  • tin alloy plating solution is a SnAg plating solution
  • a water-soluble sulfide compound or a water-soluble thiol compound can be used as the complexing agent for silver.
  • the plating solution of the present embodiment may contain a pH adjuster, if necessary.
  • the pH adjuster include various acids such as hydrochloric acid and sulfuric acid, various bases such as aqueous ammonia, potassium hydroxide, sodium hydroxide and sodium hydrogen carbonate.
  • monocarboxylic acids such as acetic acid and propionic acid
  • dicarboxylic acids such as boric acid, phosphoric acid, oxalic acid and succinic acid
  • oxycarboxylic acids such as lactic acid and tartaric acid are also effective.
  • the plating solution of the present embodiment may contain a brightener, if necessary.
  • a brightener an aromatic carbonyl compound is effective.
  • the aromatic carbonyl compound has an action of refining the crystal particles of the tin alloy in the tin alloy plating film.
  • Aromatic carbonyl compounds are carbon atoms of aromatic hydrocarbons with a carbonyl group (-CO-X: where X is a hydrogen atom, a hydroxy group, an alkyl group or a carbon atom having a carbon atom number in the range of 1 to 6). It is a compound to which (meaning an alkoxy group having a number in the range of 1 to 6) is bonded.
  • Aromatic hydrocarbons include a benzene ring, a naphthalene ring and an anthracene ring.
  • Aromatic hydrocarbons may have substituents. Examples of the substituent include a halogen atom, a hydroxy group, an alkyl group having a carbon atom number in the range of 1 to 6, and an alkoxy group having a carbon atom number in the range of 1 to 6.
  • the carbonyl group may be directly linked to an aromatic hydrocarbon, or may be bonded via an alkylene group having 1 or more carbon atoms and 6 or less carbon atoms.
  • Specific examples of the aromatic carbonyl compound include benzalacetone, cinnamic acid, cinnamaldehyde, and benzaldehyde.
  • the aromatic carbonyl compound may be used alone or in combination of two or more.
  • the amount of the aromatic carbonyl compound added to the tin alloy plating solution of the present embodiment is generally preferably in the range of 0.01 mg / L or more and 500 mg / L or less. It is more preferably 0.1 mg / L or more and 100 mg / L or less, and even more preferably 1 mg / L or more and 50 mg / L or less.
  • the electroplating method of the present embodiment is performed using the electroplating apparatus shown in FIG.
  • an insoluble anode 3 is arranged to face a member to be plated connected to a cathode, for example, a semiconductor wafer 4.
  • the above-mentioned electrolytic plating solution 2 is supplied to the plating tank 1 to perform electrolytic plating.
  • the effect of the present invention is further exhibited in a horizontal plating apparatus in which the insoluble anode 3 is horizontally arranged on the semiconductor wafer 4.
  • it is preferable that the facing surfaces of the member 4 to be plated and the insoluble anode 3 are substantially parallel to each other.
  • the vertical relationship between the member to be plated and the insoluble anode is not limited, but as shown in FIG. 1, arranging the insoluble anode on the lower side and the member to be plated on the upper side facilitates replacement of the member to be plated. , Preferable from the viewpoint of mass productivity.
  • Anode current density at the time of forming the plating film of this embodiment or equal to 0.1 A / dm 2 or more and 5A / dm 2 or less.
  • the liquid temperature is preferably in the range of 10 ° C. or higher and 50 ° C. or lower, and more preferably in the range of 20 ° C. or higher and 40 ° C. or lower.
  • Nonion-based surfactant used in Examples and Comparative Examples Polyoxyethylene polyoxypropylene block polymer (PO-EO-PO) or (EO-) containing polyoxyethylene (EO) and polyoxypropylene (PO) used in Examples 1 to 5 and Comparative Examples 1 to 5.
  • Table 1 shows the structural formula of PO-EO), the EO ratio, and the mass average molecular weight of the surfactant.
  • the methanesulfonic acid Sn aqueous solution has methanesulfonic acid as a free acid and the structural formula (PO-EO-PO) shown in Table 1 above as a surfactant, and the EO ratio is 35% in terms of molar ratio, and the mass average.
  • a nonionic surfactant having a molecular weight of 4000 and benzalacetone as a brightener were added.
  • ion-exchanged water was added to bathe the Sn plating solution having the following composition.
  • the methanesulfonic acid Sn aqueous solution was prepared by electrolyzing a metal Sn plate in the methanesulfonic acid aqueous solution.
  • Methanesulfonic acid Sn (as Sn 2+ ): 50 g / L Methanesulfonic acid (as free acid): 100 g / L Surfactant: 5g / L Benzalacetone (as a brightener): 10 mg / L Ion-exchanged water: balance
  • Examples 2 to 4 Comparative Examples 1 to 5>
  • the structural formula (PO-EO-PO) or (EO-PO-EO), the EO ratio, and the mass average molecular weight are the properties shown in Table 1 above as the surfactant.
  • a nonionic surfactant was used.
  • the Sn plating solutions of Examples 2 to 4 and Comparative Examples 1 to 5 were bathed in the same manner as in Example 1.
  • the methanesulfonic acid Sn aqueous solution was prepared by electrolyzing a metal Sn plate, and the methanesulfonic acid Ag aqueous solution was prepared by electrolyzing a metal Ag plate in the methanesulfonic acid aqueous solution.
  • Methanesulfonic acid Sn (as Sn 2+ ): 50 g / L Methanesulfonic acid Ag (as Ag + ): 0.2 g / L Methanesulfonic acid (as free acid): 100 g / L Thiodiethanol (as a complexing agent): 5 g / L Surfactant: 5g / L Benzalacetone (as a brightener): 10 mg / L Ion-exchanged water: balance
  • Example 6 As the surfactant, the nonionic surfactant 1 shown in Comparative Example 4 of Table 1 above and the amphoteric surfactant 2 of lauryl hydroxysulfobetaine (12 carbon chains) shown in Table 2 above were used. Methanesulfonic acid as a free acid and thiodiethanol as a compositing agent were mixed and dissolved in an aqueous solution of methanesulfonic acid Sn, and then a methanesulfonic acid Ag solution was further added and mixed. After mixing to obtain a uniform solution, the above-mentioned surfactant 1, the above-mentioned surfactant 2, and benzalacetone as a brightening agent were further added.
  • the methanesulfonic acid Sn aqueous solution was prepared by electrolyzing a metal Sn plate, and the methanesulfonic acid Ag aqueous solution was prepared by electrolyzing a metal Ag plate in the methanesulfonic acid aqueous solution.
  • Methanesulfonic acid Sn (as Sn 2+ ): 50 g / L Methanesulfonic acid Ag (as Ag + ): 0.2 g / L Methanesulfonic acid (as free acid): 100 g / L Thiodiethanol (as a complexing agent): 5 g / L Nonionic surfactant 1: 5g / L Amphoteric surfactant 2: 2 g / L Benzalacetone (as a brightener): 10 mg / L Ion-exchanged water: balance
  • Example 7 A SnAg plating solution having the same composition as that of Example 6 was used in the bath, except that the amphoteric surfactant 2 of Example 6 was replaced with lauryl sulfobetaine.
  • Example 8> A SnAg plating solution having the same composition as that of Example 6 was used in the bath, except that the amphoteric tenside agent 2 of Example 6 was replaced with stearyl sulfobetaine.
  • Example 9 A SnAg plating solution having the same composition as that of Example 6 was used in the bath, except that the methanesulfonic acid Ag and the nonionic surfactant were removed from Example 6.
  • the plating tank 11 is a tank for performing face-down type (Fountain type) plating, and has a cylindrical shape with an inner diameter of 35 cm and a depth of 50 cm. The height from the bottom surface to the liquid surface was 35 cm.
  • a Pt / Ti disk having a diameter of 300 mm in which a Pt layer having a thickness of 3 ⁇ m was formed on a Ti plate having a thickness of 1.5 mm was used and installed so as to be in contact with the bottom surface in the plating tank 11.
  • a pipe 11a serving as a suction port for the circulation pump 11c was installed at a height of 5 cm from the bottom surface of the plating tank 11.
  • a pipe 11b serving as a return port was installed at a position 5 cm in height from the bottom surface.
  • the circulation pump 11c and the pipe 11b serving as the return port were connected by the pipe 11d.
  • a sampling pipe 11e was branched from the pipe 11d, and a transparent measurement cell 11f was installed in the middle of the sampling pipe 11e.
  • 11 g of a VisiSize particle size distribution measuring device manufactured by Oxford Lasers, device model number: SF, analysis software: SOLO
  • the inner diameters of the pipes 11a, 11b and 11d were 60 mm, and the inner diameter of the sampling pipe 11e was 40 mm.
  • a silicon wafer 14 having a diameter of 300 mm was fixed in the plating tank 11 as shown in FIG. 3 using a cylindrical jig having an outer diameter of 33 cm (not shown). .. Specifically, the wafer 14 was fixed by immersing the wafer 14 so that the lower surface of the wafer 14 was immersed at a depth of 2 cm from the liquid surface of the plating solution 12. The wafer 14 was connected to the cathode, and the plating solution 12 was stirred by horizontally rotating at a rotation speed of 50 rpm in order to suppress the generation of bubbles due to stirring.
  • the circulation pump 11c was first operated for 10 minutes without electroplating, and the pipes 11d and 11e After filling the inside with the plating solution 12, the circulation pump 11c was stopped and allowed to stand for 1 hour for degassing. Next, the plating solution was circulated by the circulation pump 11c for 1 hour, and it was confirmed that the number of bubbles having a diameter of 10 ⁇ m or less passing through the measurement cell was 100 cells / mL or less.
  • the flow rate in the pipe 11d was set to 5 L / min, and the flow rate in the sampling pipe 11e was controlled to 0.5 L / min to circulate the plating solution 12. Then, the liquid temperature of the plating solution 12 was set to 25 ° C. and the anode current density was set to 0.7 ASD, respectively, and electrolytic plating was performed for 30 minutes.
  • oxygen bubbles 18 were generated from the insoluble anode 13.
  • the air bubbles 18 were sucked into the suction port pipe 11a, passed through the pipes 11d and 11e, and floated in the plating solution from the return port pipe 11b toward the wafer 14.
  • the size (particle size) of the bubbles 18 passing through the measurement cell 11f was measured by the particle size distribution measuring device 11g described above.
  • the maximum value of the particle size distribution of the measured bubbles is shown in Tables 1 and 3 above. When the particle size distribution has two or more maximum values (so-called two or more peaks), the largest peak is set as the maximum value.
  • Titanium 0.1 ⁇ m and copper 0.3 ⁇ m are laminated in this order on the surface of a silicon wafer with a diameter of 300 mm by a sputtering method to form a seed layer for electrical conduction, and the seed layer is formed.
  • a dry film resist (thickness 50 ⁇ m) was laminated on top of it. The dry film resist was then partially exposed via an exposure mask and then developed. In this way, as shown in FIG. 4, a resist layer 5 having a pattern in which 1.6 million vias 6 having openings having a diameter of 75 ⁇ m are formed at a pitch of 150 ⁇ m is formed on the surface of the wafer 4.
  • the temperature of the plating solution was set to 25 ° C. and the anode current density was set to 0.7 ASD, and the via 6 of the resist layer 5 was electrolytically plated with a target plating film thickness of 75 ⁇ m.
  • the wafer 4 was taken out from the plating tank 1, washed and dried, and then the resist layer 5 was peeled off using an organic solvent. In this way, a bumped wafer having a pattern in which bumps having a diameter of 75 ⁇ m are arranged at a pitch of 150 ⁇ m and 1.6 million at equal pitch intervals was produced on one die.
  • FIG. 5 (a) shows the wafer 4 before plating
  • FIGS. 5 (b) to 5 (e) show the wafer 4 after plating.
  • the same elements as those in FIGS. 1, 2 and 4 are designated by the same reference numerals.
  • reference numeral 7 is a bump which is a plating deposit layer. The heights of 1.6 million bumps on this wafer were measured using an automatic visual inspection device (Camtek, model number Falcon). From the measured bump height, the pit defect occurrence rate in the bump was calculated by the following formula. As shown in FIGS.
  • FIG. 5 (e) shows the void 9b in the bump 7 formed before the reflow.
  • a transmission X-ray apparatus manufactured by Dage
  • 5000 bumps on the reflowed wafer were observed from above and inspected for the presence of voids.
  • the case where the void area with respect to the bump area (maximum horizontal cross-sectional area of the bump) is 1% or more is counted as a "bump with a void”
  • the void generation rate is calculated based on the following equation.
  • Void generation rate (%) (number of bumps with voids / number of total bumps) x 10 2
  • Tables 1 and 3 The results are shown in Tables 1 and 3 above.
  • the maximum value of the particle size distribution of bubbles was as small as 40 ⁇ m. Therefore, the number of bumps having pit defects was 857, and the pit defect occurrence rate was as high as 536 ppm.
  • the number of bumps with voids having a void area of 1% or more was 53, and the void occurrence rate was 1.1%.
  • the maximum value of the particle size distribution of bubbles was as small as 25 ⁇ m. Therefore, the number of bumps having pit defects was 1073, and the pit defect occurrence rate was as high as 671 ppm.
  • the number of bumps with voids having a void area of 1% or more was 126, and the void occurrence rate was 2.5%.
  • the maximum value of the particle size distribution of bubbles was as small as 83 ⁇ m. Therefore, the number of bumps having pit defects was 135, and the pit defect occurrence rate was as high as 84 ppm.
  • the number of bumps with voids having a void area of 1% or more was 6, and the void occurrence rate was 0.1%.
  • the plating solutions of Examples 1 to 9 had a large maximum value of the particle size distribution of bubbles of 150 ⁇ m or more, and therefore, in the bumps formed from these plating solutions.
  • the pit defect occurrence rate was extremely low at 0 ppm to 15 ppm.
  • the void occurrence rate was 0%.
  • the bump electrode is made finer to a diameter of 100 ⁇ m or less and the depth of the resist pattern with respect to the diameter of the via is increased, the plating is deposited due to air bubbles generated in the plating solution. It was confirmed that the occurrence rate of pit defects and voids in the tin-containing bumps was reduced without being hindered.
  • the plating solution of the present invention can be used to form a part of an electronic component such as a semiconductor wafer or a bump electrode of a printed circuit board. Therefore, it can be used industrially.

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Abstract

La présente invention concerne une solution d'électrodéposition comprenant (A) un sel soluble contenant au moins un premier sel d'étain, (B) un acide ou un sel de celui-ci, et (C) un tensioactif. Lorsque l'électrolyse est conduite à une densité de courant anodique de 0,7 A/dm2, la valeur maximale de la distribution granulométrique des bulles d'air libérées à partir d'une anode insoluble est de 150 µm ou plus. Il est préférable que le tensioactif (C) soit un tensioactif non ionique comprenant un polymère séquencé de polyoxyéthylène-polyoxypropylène (PO-EO-PO) dont la terminaison est de polyoxypropylène (PO), la proportion d'EO dans le polymère séquencé (PO-EO-PO) est de 35 à 50 % en moles, inclus, et le poids moléculaire moyen en masse du tensioactif non ionique est de 3000 à 5000, inclus.
PCT/JP2021/012153 2020-03-27 2021-03-24 Solution d'électrodéposition et procédé d'électrodéposition WO2021193696A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06240489A (ja) * 1993-02-19 1994-08-30 Motorola Inc 緻密で光沢のあるスズまたはスズ−鉛合金を電着するための方法および溶液
JP2015092021A (ja) * 2013-11-05 2015-05-14 ローム アンド ハース エレクトロニック マテリアルズ エルエルシーＲｏｈｍ ａｎｄ Ｈａａｓ Ｅｌｅｃｔｒｏｎｉｃ Ｍａｔｅｒｉａｌｓ ＬＬＣ めっき浴および方法
JP2018162512A (ja) * 2017-03-27 2018-10-18 三菱マテリアル株式会社 めっき液
JP2019163507A (ja) * 2018-03-20 2019-09-26 三菱マテリアル株式会社 錫又は錫合金めっき液

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06240489A (ja) * 1993-02-19 1994-08-30 Motorola Inc 緻密で光沢のあるスズまたはスズ−鉛合金を電着するための方法および溶液
JP2015092021A (ja) * 2013-11-05 2015-05-14 ローム アンド ハース エレクトロニック マテリアルズ エルエルシーＲｏｈｍ ａｎｄ Ｈａａｓ Ｅｌｅｃｔｒｏｎｉｃ Ｍａｔｅｒｉａｌｓ ＬＬＣ めっき浴および方法
JP2018162512A (ja) * 2017-03-27 2018-10-18 三菱マテリアル株式会社 めっき液
JP2019163507A (ja) * 2018-03-20 2019-09-26 三菱マテリアル株式会社 錫又は錫合金めっき液

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