JP6427632B2 - Indium electroplating composition containing 2-imidazolidine thione compound, and method of electroplating indium - Google Patents

Description

  The present invention relates to indium electroplating compositions containing 2-imidazolidinethione compounds, and methods for electroplating indium metal on metal layers. More specifically, the present invention relates to an indium electroplating composition containing a 2-imidazolidinethione compound, and a method of electroplating indium metal on a metal layer, wherein the indium metal deposit is uniform and substantially Void-free and has a smooth surface morphology.

The ability to reproducibly plate void-free, uniform indium of target thickness and smooth surface morphology on metal layers is difficult. Indium reduction occurs at a potential more negative than that of proton reduction and significant hydrogen bubbling at the cathode results in increased surface roughness. The indium (1 ⁺ ) ions, stabilized by the inert electron pair effect and formed in the indium deposition process, catalyze proton reduction and participate in the disproportionation reaction to regenerate the indium (3 ⁺ ) ions. In the absence of complexing agents, indium ions begin to precipitate out of solution at pH> 3. The plating of indium on metals such as nickel, tin, copper and gold is that these metals are good catalysts for proton reduction and are more noble than indium, and thus can cause corrosion of indium in galvanic interactions Because it is difficult. Indium can also form unwanted intermetallic compounds with these metals. Finally, the chemistry and electrochemistry of indium have not been well studied, so the interaction with compounds that can function as additives is unknown.

  In general, conventional indium electroplating baths have not been able to electroplate indium deposits compatible with multiple bump underlayer metals (UBMs) such as nickel, copper, gold and tin. More importantly, conventional indium electroplating baths have not been able to electroplate indium with high coplanarity and high surface planarity on a substrate comprising nickel. However, indium is a highly desirable metal in many industries because of its unique physical properties. For example, it is soft enough so that it deforms easily, filling the microstructure between the two mating parts, low melting temperature (156 ° C.) and high thermal conductivity (̃82 W / m ° K) Good electrical conductivity, alloying, and good ability to form intermetallic compounds with other metals in the stack. It can be used as a low temperature solder bump material, which is a desirable process of 3D stack assembly to reduce damage to assembled chips due to thermal stress induced during reflow process. Such properties allow indium to be used in a variety of applications in the electronics and related industries, including semiconductor and polycrystalline thin film solar cells.

  Indium can also be used as a heat conducting material (TIM). TIMs are important to protect electronic devices such as integrated circuits (ICs) and active semiconductor devices, such as microprocessors, from exceeding their operating temperature limits. They allow heat-generating devices (eg, silicon semiconductors) to be bonded to heat sinks or heat spreaders (eg, copper and aluminum components) without creating excessive thermal barriers. TIMs may also be used in the assembly of heat sinks or other components of a heat spreader stack that comprise the entire thermal impedance path.

  For example, several types of materials, such as thermal greases, thermal gels, adhesives, elastomers, thermal pads, and phase change materials, have been used as TIMs. While the TIMs described above have been suitable for many semiconductor devices, the increased performance of semiconductor devices has made such TIMs unsuitable. The thermal conductivity of many current TIMs does not exceed 5 W / m ° K and many are less than 1 W / m ° K. However, there is currently a need for TIMs that form thermal interfaces with an effective thermal conductivity greater than 15 W / m ° K.

  Thus, indium is a highly desirable metal for electronic devices, and there is a need for improved indium compositions for electroplating indium metal on metal substrates.

  The composition comprises one or more sources of indium ions, one or more 2-imidazolidinethione compounds, and citric acid, a salt thereof, or a mixture thereof.

  The method comprises providing a substrate comprising a metal layer; the substrate comprising one or more sources of indium ions, one or more 2-imidazolidinethione compounds, and citric acid, a salt thereof, or a mixture thereof. And D. contacting an indium electroplating composition; and electroplating the indium metal layer on the metal layer of the substrate using the indium electroplating composition.

  The present indium electroplating compositions can provide a deposit of indium metal that is substantially void free, uniform, and has a smooth morphology on the metal layer. The ability to reproducibly plate void-free, uniform indium with target thickness and smooth surface morphology enables expanded use of indium in the electronics industry, including semiconductor and polycrystalline thin film solar cells. Indium deposited from the electroplating composition of the present invention can be used as a low temperature solder bump material desirable in 3D stack assemblies to reduce damage to assembled chips due to thermal stress induced during reflow processing . Indium can also be used as a thermally conductive material to protect electronic devices such as microprocessors and integrated circuits. The present invention addresses many of the problems of not being able to electroplate an indium layer of sufficient properties to meet the requirements of applications in previous advanced electronic devices.

8 is an optical microscope image of a nickel plated via having a diameter of 75 μm. 8 is an optical microscope image of an indium layer on a nickel plated via having a diameter of 75 μm. Optical microscope of an indium layer on a nickel plated via having a diameter of 75 μm, wherein the indium is electroplated from an indium composition containing 0.25 g / L of 1- (2-hydroxyethyl) -2-imidazolidinethione It is an image. An indium layer on a nickel-plated rectangular via having a length of 50 μm, wherein the indium is electroplated from an indium composition containing 1.25 g / L of 1- (2-hydroxyethyl) -2-imidazolidinethione It is an optical microscope image. Optical microscope of an indium layer on a nickel plated via having a diameter of 75 μm, wherein the indium is electroplated from an indium composition containing 0.01 g / L 1- (2-hydroxyethyl) -2-imidazolidinethione It is an image. Optical microscope of an indium layer on a nickel plated via having a diameter of 75 μm, wherein the indium is electroplated from an indium composition containing 0.1 g / L 1- (2-hydroxyethyl) -2-imidazolidinethione It is an image. FIG. 6 is an optical microscope image of an indium layer on a nickel plated via having a diameter of 75 μm electroplated from an indium composition containing indium, 1- (2-hydroxyethyl) -2-imidazolidinethione and sodium chloride .

As used throughout this specification, the following abbreviations have the following meanings, unless the context clearly indicates otherwise. ° C = degrees Celsius, ° K = degrees Kelvin, g = grams, mg = milligrams, L = liters, A = amps, dm = decimeters, ASD = A / dm ² = current density, μm = microns = micrometers; ppm = 1,000,000, ppb = billion, ppm = mg / L, indium ion = In ³⁺ , Li ⁺ = lithium ion, Na ⁺ = sodium ion, K ⁺ = potassium ion, NH ₄ ⁺ = ammonium ion, nm = Nanometer = 10 ^-9 meters, μm = micrometer = 10 ^-6 meters, M = mole, MEMS = microelectromechanical system, TIM = thermally conductive material, IC = integrated circuit, EO = ethylene oxide, and PO = propylene oxide .

  The terms "deposit," "plate," and "electroplate" are used interchangeably throughout this specification. The term "copolymer" is a compound consisting of two or more different mers. The term "dendrite" refers to branched spike-like metal crystals. Unless otherwise stated, all plating baths are aqueous solvent based, ie, aqueous plating baths. All amounts are weight percent and all ratios are on a molar basis, unless otherwise stated. All numerical ranges are inclusive and combinable in any order, except where it is logical that such numerical ranges are constrained to add up to 100%.

  The composition comprises one or more sources of indium ions that are soluble in an aqueous environment. The indium composition does not contain an alloying metal. Such sources include, for example, methanesulfonic acid, ethanesulfonic acid, butanesulfonic acid, benzenesulfonic acid, and alkanesulfonic acids such as toluenesulfonic acid and indium salts of aromatic sulfonic acids, indium salts of sulfamic acid, and indium sulfuric acid Salts, chlorides and bromides of indium, nitrates, hydroxides, indium oxide, fluoroborates, such as citric acid, acetoacetic acid, glyoxylic acid, pyruvic acid, glycolic acid, malonic acid, hydroxamic acid, iminodiacetic acid Indium salts of carboxylic acids such as salicylic acid, glyceric acid, succinic acid, malic acid, tartaric acid and hydroxybutyric acid, eg, arginine, aspartic acid, asparagine, glutamic acid, glycine, glutamine, leucine, lysine, threonine, threonine, isoleucine and valine An indium salt of an amino acid, including but not limited to. Typically, the indium ion source is one or more indium salts of sulfuric acid, sulfamic acid, alkanesulfonic acid, aromatic sulfonic acid, and carboxylic acid. More typically, the indium ion source is one or more indium salts of sulfuric acid and sulfamic acid.

A water soluble salt of indium is included in the composition in an amount sufficient to provide an indium deposit of the desired thickness. Preferably, the water soluble indium salt is present in the composition in an amount of 2 g / L to 70 g / L, more preferably 2 g / L to 60 g / L, most preferably 2 g / L to 30 g / L of indium (3 ⁺ And the like) to be included in the present composition to provide ions.

  One or more 2-imidazolidinethione compounds are included in the indium composition. The one or more 2-imidazolidinethione compounds are indium in amounts of 0.005 g / L to 5 g / L, preferably 0.01 g / L to 3 g / L, more preferably 0.01 g / L to 1.5 g / L. It is contained in a composition.

  Examples of 2-imidazolidinethione compounds include, but are not limited to, compounds having the following formulae:

Wherein R ₁ and R ₂ are independently hydrogen, linear or branched (C ₁ -C ₁₂ ) alkyl, linear or branched hydroxy (C ₁ -C ₁₂ ) alkyl, linear or branched (C _1- C ₁₂ ) Alkoxy, linear or branched (C ₃ -C ₁₂ ) allyl, amino, primary, secondary or tertiary amino (C ₁ -C ₁₂ ) alkyl, acetyl, and substituted or unsubstituted aryl _(C 1 _{-C 12)} is selected from _{alkyl; R 3, R 4, R} 5, and _{R 6} are independently hydrogen, a linear or branched _(C 1 _{-C 12)} alkyl, hydroxyl, straight-chain or branched Hydroxy (C ₁ -C ₁₂ ) alkyl, primary, secondary or tertiary amino, aryl, linear or branched (C ₁ -C ₁₂ ) alkoxy, primary, secondary or tertiary Grade Mino _(C 1 _{-C 12)} alkyl, and is selected from acetyl. Substituents on aryl include linear or branched (C ₁ -C ₅ ) alkyl, hydroxyl, hydroxy (C ₁ -C ₅ ) alkyl, (C ₁ -C ₃ ) alkoxy, as well as primary and secondary And tertiary amino (C ₁ -C ₅ ) alkyls, but is not limited thereto. As a substituent replacing hydrogen of secondary and tertiary amino groups, linear or branched (C ₁ -C ₅ ) alkyl, substituted or unsubstituted phenyl, linear or branched hydroxyl (C ₁ -C ₅ ) alkyl And (C ₄ -C ₈ ) alicyclic, but is not limited thereto.

Preferably, R ₁ and R ₂ are independently hydrogen, linear or branched (C ₁ -C ₅ ) alkyl, linear or branched hydroxy (C ₁ -C ₅ ) alkyl, (C ₁ -C ₃ ) alkoxy , Amino, primary or secondary amino (C ₁ -C ₅ ) alkyl, and acetyl. Preferably, R ₃ , R ₄ , R ₅ and R ₆ are independently hydrogen, linear or branched (C ₁ -C ₅ ) alkyl, hydroxyl, linear or branched hydroxy (C ₁ -C ₅ ) alkyl And substituted or unsubstituted phenyl. More preferably, R ₁ and R ₂ are independently hydrogen, (C ₁ -C ₂ ) alkyl, hydroxy (C ₁ -C ₃ ) alkyl, primary amino (C ₁ -C ₃ ) alkyl, and acetyl It is selected from More preferably, R ₃ , R ₄ , R ₅ and R ₆ are independently selected from hydrogen, (C ₁ -C ₄ ) alkyl, hydroxyl and phenyl.

  Examples of such 2-imidazolidinethione compounds are 2-imidazolidinethione, 1,3-dimethyl-2-imidazolidinethione, 1-methyl-5-phenyl-2-imidazolidinethione, 1,3-diethyl-2-imidazolidinethione, 1-methyl-2 -Imidazolidinethione, 4,4-dimethyl-2-imidazolidinethione, 4,5-dimethyl-2-imidazolidinethione, (4S) -4-methyl-2-imidazolidinethione, 1-dodecyl-2-imidazolidinethione, 1-butyl-5- ( 1-Methylethyl) -2-imidazolidinethione, 1,3-diallyl-2-imidazolidinethione, 1-acetyl-3-allyl-2-imidazolidinethione, 1- (2-aminoethyl) -2-imidazolidinethione, 1-acetyl-2 -Imidazolidine Thione, 4,5-dihydroxy-1-methyl-2-imidazolidinethione, 1- (2-hydroxyethyl) -2-imidazolidinethione, 1,3-bis (hydroxymethyl) -2-imidazolidinethione, 1-ethyl-5- ( 4-methoxyphenyl) -2-imidazolidinethione, 1,3-diethyl-4,5-dihydroxy-4,5-diphenyl-2-imidazolidinethione, and 1,3 bis [(cyclohexylamino) methyl] -2-imidazolidinethione .

  Citric acid, its salts or mixtures thereof are included in the present indium composition. Citrate salts include, but are not limited to sodium citrate dihydrate, monosodium citrate, potassium citrate, and diammonium citrate. Citric acid, its salts or mixtures thereof may be included in amounts of 5 g / L to 300 g / L, preferably 50 g / L to 200 g / L. Preferably, a mixture of citric acid, and salts thereof, are included in the present indium composition in the amounts described above.

  Optionally, but preferably, one or more chloride ion sources are included in the present indium electroplating compositions. Chloride ion sources include, but are not limited to sodium chloride, potassium chloride, hydrogen chloride, or mixtures thereof. Preferably, the chloride ion source is sodium chloride, potassium chloride or a mixture thereof. More preferably, the chloride ion source is sodium chloride. The one or more chloride ion sources may have a molar ratio of chloride ions to indium ions of at least 2: 1, preferably 2: 1 to 7: 1, more preferably 4: 1 to 6: 1. It is contained in a composition.

Optionally, in addition to citric acid, its salts, or mixtures thereof, one or more additional buffering agents may be included in the present indium composition to provide a pH of 1 to 4, preferably 2 to 3. . Buffering agents include salts of acids and their conjugate bases. As the acid, amino acid, carboxylic acid, glyoxylic acid, pyruvic acid, hydroxamic acid, iminodiacetic acid, salicylic acid, salicylic acid, succinic acid, hydroxybutyric acid, acetic acid, acetoacetic acid, tartaric acid, phosphoric acid, oxalic acid, carbonic acid, ascorbic acid, boric acid Butanoic acid, thioacetic acid, glycolic acid, malic acid, formic acid, heptanoic acid, hexanoic acid, hydrofluoric acid, lactic acid, nitric acid, nitrous acid, octanoic acid, pentanoic acid, uric acid, nonanoic acid, decanoic acid, sulfurous acid, sulfuric acid, alkane Sulfonic acid and arylsulfonic acid, such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid and the like, and sulfamic acid can be mentioned. The acid is combined with the conjugated bases Li ⁺ , Na ⁺ , K ⁺ , NH ₄ ⁺ , or (C _n H _{(2n + 1) 2} ) ₄ N ⁺ salt, where n is an integer of 1 to 6.

  Optionally, one or more surfactants may be included in the present indium compositions. As such surfactants, amine surfactants such as quaternary amines, which are commercially available as TOMAMINE (registered trademark) -Q-C-15 surfactants, TOMAMINE (registered trademark) -AO-455 surfactants Amine oxides (both available from Air Products) commercially available as: Hydrophilic polyether monoamines commercially available from Huntsman as SURFONAMINE® L-207 amine surfactant; RALUFON® EA 15-90 Polyethylene glycol octyl (3-sulfopropyl) diether marketed as surfactant; a potassium salt marketed as RALUFON® NAPE 14-90 surfactant [(3-sulfopropoxy) -polyalcohol ] -Β-Naphthyl ether, octaethylene glycol octyl ether marketed as RALUFON® EN 16-80 surfactant, potassium salt marketed as RALUFON® F 11-3 surfactant Polyethylene glycol alkyl (3-sulfopropyl) diethers (all available from Raschig GmbH); EO / PO block copolymers commercially available as TETRONIC®-304 surfactants available from BSF; ADUXOLTM ) Ethoxylated beta-naphthols from Schaerer & Schlaepfer AG such as NAP-08, ADUXOL (TM) NAP-03, ADUXOL (TM) NAP-06, etc; Air Products and Ch emicals Co. Ethoxylated 2,4,7,9-Tetramethyl-5-decyne-4,7-diol such as SURFYNOL® 484 surfactant from: Ethoxylated such as TIB Chemicals LUXTM NPS surfactant LUXTM BN-13 surfactant which is β-naphthol; PCC Chemax, Inc. And ethoxylated-.beta.-naphthols such as, but not limited to, POLYMAX.RTM. PA-31 surfactants available from U.S. Pat. Such surfactants are included in amounts of 1 ppm to 10 g / L, preferably 5 ppm to 5 g / L.

  Optionally, the indium composition may include one or more crystal grain refining agents. Such crystal refining agents include 2-picolinic acid, sodium 2-naphthol-7-sulfonate, 3- (benzothiazol-2-ylthio) propane-1-sulfonic acid (ZPS), 3- (carbanimidoylthio ( carbamimidoylthio)) propane-1-sulfonic acid (UPS), bis (sulfopropyl) disulfide (SPS), mercaptopropanesulfonic acid (MPS), 3-N, N-dimethylaminodithiocarbamoyl-1-propanesulfonic acid (DPS) And (O-ethyldithiocarbonato) -S- (3-sulfopropyl) -ester (OPX), but is not limited thereto. Preferably, such grain refiners are included in the present indium compositions in amounts of 0.1 ppm to 5 g / L, more preferably 0.5 ppm to 1 g / L.

  Optionally, one or more inhibitors may be included in the present indium compositions. Examples of inhibitors include phenanthroline and its derivatives such as 1,10-phenanthroline, triethanolamine and its derivatives such as triethanolamine lauryl sulfate, sodium lauryl sulfate, and ammonium ethoxylated lauryl sulfate, etc. polyethylenimine and its derivatives For example, but not limited to, hydroxypropyl polyene imine (HPPEI-200) and the like, and alkoxylated polymers. Such inhibitors are included in the present indium compositions in conventional amounts. Typically, the inhibitor is included in an amount of 1 ppm to 5 g / L.

  Optionally, one or more levelers may be included in the present indium composition. Levelers include, but are not limited to, polyalkylene glycol ethers. Such ethers include dimethyl polyethylene glycol ether, di-tertiary butyl polyethylene glycol ether, polyethylene / polypropylene dimethyl ether (mixed or block copolymer), and octyl monomethyl polyalkylene ether (mixed or block copolymer). It is not limited. Such levelers are included in conventional amounts. Generally, such levelers are included in amounts of 100 ppb to 500 ppb.

  Optionally, one or more hydrogen inhibitors can be included in the present indium composition to suppress hydrogen gas formation during electroplating of indium metal. Hydrogen inhibitors include epihalohydrin copolymers. Epihalohydrin includes epichlorohydrin and epibromohydrin. Typically, a copolymer of epichlorohydrin is used. Such copolymers are water soluble polymerization products of epichlorohydrin or epibromohydrin and one or more organic compounds comprising nitrogen, sulfur, oxygen atoms, or combinations thereof.

As nitrogen-containing organic compounds copolymerizable with epihalohydrin,
1) Aliphatic chain amine,
2) Unsubstituted heterocyclic nitrogen compounds having at least two reactive nitrogen sites, and 3) having at least two reactive nitrogen sites and selected from alkyl groups, aryl groups, nitro groups, halogens, and amino groups It includes, but is not limited to, substituted heterocyclic nitrogen compounds having 1 to 2 substituents.

  Examples of aliphatic chain amines include dimethylamine, ethylamine, methylamine, diethylamine, triethylamine, ethylenediamine, diethylenetriamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, 2-ethylhexylamine, isooctylamine and nonylamine Include, but are not limited to, isononylamine, decylamine, undecylamine, dodecylamine, tridecylamine, and alkanolamines.

  Examples of unsubstituted heterocyclic nitrogen compounds having at least two reactive nitrogen sites include imidazole, imidazoline, pyrazole, 1,2,3-triazole, tetrazole, pyradazine, 1,2,4-triazole, 1,2,3 Examples include, but are not limited to, 3-oxadiazole, 1,2,4-thiadiazole, and 1,3,4-thiadiazole.

  Examples of substituted heterocyclic nitrogen compounds having at least two reactive nitrogen sites and having 1 to 2 substituents include benzimidazole, 1-methylimidazole, 2-methylimidazole, and 1,3-diemthyl imidazole And 4-hydroxy-2-aminoimidazole, 5-ethyl-4-hydroxyimidazole, 2-phenylimidazoline, and 2-tolylimidazoline, but not limited thereto.

  Preferably, imidazole, pyrazole, imidazoline, 1,2,3-triazole, tetrazole, pyridazine, 1,2,4-triazole, 1,2,3-oxadiazole, 1,2,4-thiadiazole, and 1, 3,4-thiadiazole, and one or more compounds selected from methyl, ethyl, phenyl and derivatives thereof incorporating one or two substituents selected from amino groups are used to form epihalohydrin copolymers Ru.

  Some of the epihalohydrin copolymers are commercially available from, for example, Raschig GmbH, Ludwigshafen Germany and BASF, Wyandotte, MI, USA, or can be made by methods disclosed in the literature. An example of a commercially available imidazole / epichlorohydrin copolymer is LUGALVAN® IZE copolymer obtained from BASF.

  The epihalohydrin copolymer may be formed by reacting the epihalohydrin with a nitrogen, sulfur or oxygen containing compound described above under any suitable reaction conditions. For example, in one method, both materials are dissolved in mutual solvent at a suitable concentration and reacted therein, for example, for 45 to 240 minutes. The aqueous chemical product of the reaction is separated by distilling off the solvent and then added to the water body, which functions as an electroplating solution when the indium salt dissolves. In another method, these two materials are placed in water and heated to 60 ° C. with constant vigorous stirring until they dissolve in water as they react.

  A wide range of reactant to epihalohydrin ratios such as 0.5: 1 to 2: 1 moles may be used. Typically, the molar ratio is 0.6: 1 to 2: 1 molar, more typically the molar ratio is 0.7 to 1: 1, and most typically the molar ratio is 1: It is 1.

  In addition, the reaction product may be further reacted with one or more reagents before the electroplating composition is completed by the addition of the indium salt. Thus, the described product may be further reacted with a reagent that is at least one of ammonia, aliphatic amines, polyamines, and polyimines. Typically, the reagent is at least one of ammonia, ethylenediamine, tetraethylenepentamine, and polyethylenimine having a molecular weight of at least 150, but other species meeting the definition described herein are It may be used. The reaction can occur in water with stirring.

  For example, the reaction between the reaction product of epichlorohydrin and the nitrogen-containing organic compound described above and a reagent selected from one or more of ammonia, aliphatic amines, and arylamines or polyimines, for example, At a temperature of 30 <0> C to 60 <0> C, for example, 45 to 240 minutes may occur and may be performed. The molar ratio between the reaction product and the reagent of the nitrogen-containing compound-epichlorohydrin reaction is typically 1: 0.3-1.

  The epihalohydrin copolymer is included in the present composition in an amount of 0.01 g / L to 100 g / L. Preferably, the epihalohydrin copolymer is included in an amount of 0.1 g / L to 80 g / L, more preferably in an amount of 0.1 g / L to 50 g / L, most preferably in an amount of 1 g / L to 30 g / L Included.

  The present indium compositions may be used to deposit substantially uniform, void-free indium metal layers on metal layers of various substrates. The indium layer is also substantially dendrite free. The indium layer preferably has a thickness in the range of 10 nm to 100 μm, more preferably 100 nm to 75 μm.

  The apparatus used to deposit indium metal on the metal layer is conventional. Preferably, conventional soluble indium electrodes are used as the anode. Any suitable reference electrode may be used. Typically, the reference electrode is a silver chloride / silver electrode. The current density may range from 0.1 ASD to 10 ASD, preferably 0.1 to 5 ASD, more preferably 1 to 4 ASD.

  The temperature of the indium composition during indium metal electroplating can range from room temperature to 80 ° C. Preferably, the temperature is in the range of room temperature to 65 ° C, more preferably room temperature to 60 ° C. Most preferably, the temperature is room temperature.

  The present indium compositions are used to electroplate indium metal onto nickel, copper, gold, and tin layers of various substrates including components for electronic devices, for magnetic field devices and superconducting MRI. It is also good. Preferably, the indium is electroplated on nickel. The metal layer is preferably in the range of 10 nm to 100 μm, more preferably 100 nm to 75 μm. The present indium compositions may also be used with conventional photographic imaging methods for electroplating indium metal small diameter solder bumps on various substrates such as silicon wafers. The small diameter bumps preferably have a diameter of 1 μm to 100 μm, more preferably 2 μm to 50 μm, with an aspect ratio of 1 to 3.

  For example, the present indium composition may be, for example, a component for an electrical device such as, but not limited to, as a TIM for an IC, a microprocessor of a semiconductor device, a MEMS, a component for an optoelectronic device, etc. May be used to electroplate indium metal. Such electronic components may be included in printed wiring boards and enclosed chip scale and wafer level packages. Such packages are typically sealed and include an enclosed volume formed between the base substrate and the lid, and the electronic device is disposed within the enclosed volume. The package provides containment and protection of the enclosed device from dirt and water vapor in the air outside the package. The presence of dirt and water vapor in the package can cause problems such as corrosion of metal parts and optical losses in the case of optoelectronic devices and other optical components. Low melting temperatures (156 ° C.) and high thermal conductivities (̃82 W / m ° K) are properties that make indium metal highly desirable for use as a TIM.

  In addition to TIM, the present indium compositions may be used to electroplate an underlayer on a substrate to prevent whisker formation in electronic devices. The substrate may be an electrical or electronic component or component such as a film carrier for attaching a semiconductor chip, a printed circuit board, a lead frame, a contact element such as a contact or terminal, and plating requiring a good appearance and high operation reliability. Structural members are included, but not limited thereto.

  The following examples further illustrate the invention but are not intended to limit the scope of the invention.

Example 1 (comparative example)
Silicon Valley Microelectronics, Inc. Silicon Valley Microelectronics, Inc. A photoresist patterned silicon wafer having a plurality of vias having a diameter of 75 μm and a copper seed layer at the base of each via, using a NIKALTM BP nickel electroplating bath available from Dow Advanced Materials Electroplated with a nickel layer. Nickel electroplating was performed for 120 seconds at 55 ° C., 1 ASD cathodic current density. The current was supplied by a conventional rectifier. The anode was a soluble nickel electrode. After plating, the silicon wafer was removed from the plating bath and the photoresist was stripped from the wafer using a SHIPLEY BPRTM Photostripper available from Dow Advanced Materials and rinsed with water. The nickel deposits appeared to be substantially smooth and have no observable dendrites on the surface. FIG. 1A is an optical image of one of the nickel plated copper seed layers taken with a LEICATM light microscope.

  The following aqueous indium electrolyte compositions were prepared.

  Another photo, except that the nickel layer electroplating process described above was used to electroplate the nickel layer followed by immersing the nickel plated silicon wafer in the indium electroplating composition and electroplating the indium metal onto the nickel Repeat for the resist patterned wafer set. Indium electroplating was performed for 30 seconds at 25 ° C., 4 ASD current density. The pH of the indium electroplating composition was 2.4. The anode was an indium soluble electrode. After plating indium on nickel, the photoresist was stripped from the wafer and the morphology of the indium deposit was observed. All indium deposits appeared rough.

  FIG. 1B is an optical image of one of the indium metal deposits electroplated on a nickel layer. The indium deposits were very rough in contrast to the nickel deposits shown in FIG. 1A.

Example 2
The method described in Example 1 above was repeated except that the indium electroplating composition included the following components.

  The nickel plated silicon wafer was immersed in the indium electroplating composition and the indium metal was electroplated on nickel. Indium electroplating was performed for 30 seconds at 25 ° C., 4 ASD current density. The pH of the composition was 2.4. The anode was an indium soluble electrode. After electroplating the indium onto the nickel layer, the photoresist was stripped from the wafer and the indium morphology was observed. All indium deposits appeared uniform and smooth.

  FIG. 2 is an optical microscope image of one of the indium metal deposits electroplated on a nickel layer. The indium deposit appeared smooth in contrast to the indium deposit of FIG. 1B.

Example 3
The silicon wafer is photoresist patterned to have rectangular vias having a length of 50 μm, and described in Example 1 above, except that the indium electroplating composition contained the following components: The method was repeated.

  The nickel plated silicon wafer was immersed in the indium electroplating composition and the indium metal was electroplated on nickel. Indium electroplating was performed for 30 seconds at 25 ° C., 4 ASD current density. The pH of the composition was 2.4. After indium was electroplated onto nickel, the photoresist was stripped from the wafer and the indium morphology was observed. All indium deposits appeared uniform and smooth.

  FIG. 3 is an optical microscope image of one of the indium metal deposits electroplated on a nickel layer. The indium deposit appeared smooth in contrast to the indium deposit of FIG. 1B.

Example 4
The method described in Example 2 above was repeated except that the indium electroplating composition included the following components.

  The nickel plated silicon wafer was immersed in the indium electroplating composition and the indium metal was electroplated on nickel. Indium electroplating was performed for 30 seconds at 25 ° C., 4 ASD current density. The pH of the composition was 2.4. The anode was an indium soluble electrode. After electroplating the indium onto the nickel layer, the photoresist was stripped from the wafer and the indium morphology was observed. All indium deposits appeared uniform and smooth.

  FIG. 4 is an optical microscope image of one of the indium metal deposits electroplated on a nickel layer. The indium deposit appeared smooth in contrast to the indium deposit of FIG. 1B.

Example 5
The method described in Example 2 above was repeated except that the indium electroplating composition included the following components.

  The nickel plated silicon wafer was immersed in the indium electroplating composition and the indium metal was electroplated on nickel. Indium electroplating was performed for 30 seconds at 25 ° C., 4 ASD current density. The pH of the composition was 2.4. The anode was an indium soluble electrode. After electroplating the indium onto the nickel layer, the photoresist was stripped from the wafer and the indium morphology was observed. All indium deposits appeared uniform and smooth.

  FIG. 5 is an optical microscope image of one of the indium metal deposits electroplated on a nickel layer. The indium deposit appeared smooth in contrast to the indium deposit of FIG. 1B.

Example 6
The method described in Example 2 above is repeated except that the indium electroplating composition contains the following components.

  The pH of the bath during electroplating is 2.4. The nickel plated silicon wafer is immersed in an indium electroplating composition and indium metal is electroplated on nickel. Indium electroplating is performed for 11 seconds at 25 ° C. and a current density of 4 ASD. After electroplating the indium onto nickel, the photoresist is stripped from the wafer and the indium morphology is observed. The indium deposits all appear uniform and smooth, substantially as shown in FIGS.

Example 7
An indium electroplating composition is prepared comprising the following components.

  The pH of the bath during electroplating is 2.4. The nickel plated silicon wafer is immersed in an indium electroplating composition and indium metal is electroplated on nickel. Indium electroplating is performed for 11 seconds at 25 ° C. and a current density of 4 ASD. After electroplating the indium onto nickel, the photoresist is stripped from the wafer and the indium morphology is observed. The indium deposits all appear uniform and smooth, substantially as shown in FIGS.

Example 8
An indium electroplating composition is prepared comprising the following components.

  The pH of the bath during electroplating is 2.4. The nickel plated silicon wafer is immersed in an indium electroplating composition and indium metal is electroplated on nickel. Indium electroplating is performed for 11 seconds at 25 ° C. and a current density of 4 ASD. After electroplating the indium onto nickel, the photoresist is stripped from the wafer and the indium morphology is observed. The indium deposits all appear uniform and smooth, substantially as shown in FIGS.

Example 9
The method described in Example 2 above was repeated except that the indium electroplating composition included the following components.

The nickel plated silicon wafer was immersed in the indium electroplating composition and the indium metal was electroplated on nickel. Indium electroplating was performed for 30 seconds at 25 ° C., 4 ASD current density. The pH of the composition was 2.4. After electroplating the indium onto the nickel layer, the photoresist was stripped from the wafer and the indium morphology was observed. All indium deposits appeared uniform and smooth. FIG. 6 is an optical microscope image of indium electroplated from the baths of Table 9. As shown in FIG. 6, the indium deposit was uniform and smooth.

Claims (13)

One or more sources of indium ions, 0.005 g / L to 5 g / L of one or more 2-imidazolidinethione compounds, 5 g / L to 300 g / L of citric acid, a salt thereof, or a mixture thereof An indium electroplating composition ,
The one or more 2-imidazolidinethione compounds have the formula:
In the formula, _{R 1} and _{R 2} are independently hydrogen, a linear or branched _(C 1 _{-C 12)} alkyl, linear or branched hydroxy _(C 1 _{-C 12)} alkyl, linear or branched _{(C 1} - C ₁₂ ) Alkoxy, linear or branched (C ₃ -C ₁₂ ) allyl, amino, primary, secondary or tertiary amino (C ₁ -C ₁₂ ) alkyl, acetyl, and substituted or unsubstituted aryl _(C 1 _{-C 12)} is selected from _{alkyl; R 3, R 4, R} 5, and _{R 6} are independently hydrogen, a linear or branched _(C 1 _{-C 12)} alkyl, hydroxyl, straight-chain or branched Hydroxy (C ₁ -C ₁₂ ) alkyl, primary, secondary or tertiary amino, aryl, linear or branched (C ₁ -C ₁₂ ) alkoxy, primary, secondary or tertiary Grade Mino _(C 1 _{-C 12)} alkyl, and is selected from acetyl, substituents on said aryl, linear or branched _(C 1 -C ₅₎ alkyl, hydroxyl, hydroxy _(C 1 -C ₅₎ alkyl, ( Selected from the group consisting of C ₁ -C ₃ ) alkoxy and primary, secondary and tertiary amino (C ₁ -C ₅ ) alkyl;
The indium electroplating composition is free of alloying metals; and
The indium electroplating composition does not contain a compound of the following formula (II):
_{H-A 'p -Q- [C} (O) -CH 2 O - ((R 1 CH) t -O) Z -CH 2 -C (O) -NH-A] u -H (II)
(Wherein, A ′ is — (NH— (CH ₂ ) _{x ′} ) _{y ′} −; —NH (CH ₂ ) _{x ′} — (O— (CHR ₁ ) _{r ′} ) _w′— O— (CH ₂ ) _{x '-;} or _{-NH - ((R 1 CH)} r' -O) w '-C 2 H 4 - a and,
A is — (CH ₂ ) _x —NH) _y —; — ( CH ₂ ) _x — (O— (CHR ₁ ) _r ) _w —O— (CH ₂ ) _x —NH—; or — ((R ₁ CH) _r -O) _w -C ₂ H ₄ -NH-;
R ₁ is -H or -CH ₃ ,
Q is -NH- when p = 1 or -O- when p = 0,
p is 0 or 1, where H-and Q form a chemical bond when p = 0,
r 'is an integer of 2 to 4,
w 'is an integer of 1 to 50,
x 'is an integer of 2 to 6,
y 'is an integer of 0 to 5,
Where H- and Q form a chemical bond when y 'is 0,
r is an integer of 2 to 4,
w is an integer of 1 to 50,
x is an integer of 2 to 6,
y is an integer from 0 to 5, where H- is attached to the nitrogen of the terminal -C (O) -NH- when y is 0,
t is an integer of 2 to 4,
u is an integer of 1 to 20,
w is an integer of 1 to 50, and
z is an integer of 1 to 50). The one or more 2-imidazolidinethione compounds are 2-imidazolidinethione, 1,3-dimethyl-2-imidazolidinethione, 1-methyl-5-phenyl-2-imidazolidinethione, 1,3-diethyl-2-imidazolidinethione, 1-methyl -2-imidazolidinethione, 4,4-dimethyl-2-imidazolidinethione, 4,5-dimethyl-2-imidazolidinethione, (4S) -4-methyl-2-imidazolidinethione, 1-dodecyl-2-imidazolidinethione, 1-butyl-5 -(1-Methylethyl) -2-imidazolidinethione, 1,3-diallyl-2-imidazolidinethione, 1-acetyl-3-allyl-2-imidazolidinethione, 1- (2-aminoethyl) -2-imidazolidinethione, 1-acetyl -2-imidazo Zincthione, 4,5-dihydroxy-1-methyl-2-imidazolidinethione, 1- (2-hydroxyethyl) -2-imidazolidinethione, 1,3-bis (hydroxymethyl) -2-imidazolidinethione, 1-ethyl-5- ( Selection from 4-methoxyphenyl) -2-imidazolidinethione, 1,3-diethyl-4,5-dihydroxy-4,5-diphenyl-2-imidazolidinethione, and 1,3 bis [(cyclohexylamino) methyl] -2-imidazolidinethione It is the composition of claim 1 2. The composition according to claim 1 or 2 , wherein the composition further comprises one or more sources of chloride ions, and the molar ratio of the chloride ions to the indium ions is 2: 1 or more . The composition of claim 3 , wherein the molar ratio of chloride ion to indium ion is 2: 1 to 7: 1. 5. The composition of claim 4 , wherein the molar ratio of chloride ion to indium ion is 4: 1 to 6: 1. Selected from amine surfactants, ethoxylated naphthols, sulfonated naphthol polyethers, (alkyl) phenol ethoxylates, sulfonated alkyl alkoxylates, alkylene glycol alkyl ethers, and sulfopropylated polyalkoxylated beta-naphthol alkali salts, The composition of any one of claims 1 to 5 , further comprising one or more surfactants. 7. The composition according to any one of the preceding claims, further comprising one or more copolymers of reaction products of epihalohydrin and one or more nitrogen-containing organic compounds. Method,
a) providing a substrate comprising a metal layer,
b) said substrate comprises one or more sources of indium ions, one or more 2-imidazolidinethione compounds from 0.005 g / L to 5 g / L , and 5 g / L to 300 g / L citric acid, salts of citric acid An indium electroplating composition comprising: or a mixture thereof ;
The one or more 2-imidazolidinethione compounds have the formula:
In the formula, _{R 1} and _{R 2} are independently hydrogen, a linear or branched _(C 1 _{-C 12)} alkyl, linear or branched hydroxy _(C 1 _{-C 12)} alkyl, linear or branched _{(C 1} - C ₁₂ ) Alkoxy, linear or branched (C ₃ -C ₁₂ ) allyl, amino, primary, secondary or tertiary amino (C ₁ -C ₁₂ ) alkyl, acetyl, and substituted or unsubstituted aryl _(C 1 _{-C 12)} is selected from _{alkyl; R 3, R 4, R} 5, and _{R 6} are independently hydrogen, a linear or branched _(C 1 _{-C 12)} alkyl, hydroxyl, straight-chain or branched Hydroxy (C ₁ -C ₁₂ ) alkyl, primary, secondary or tertiary amino, aryl, linear or branched (C ₁ -C ₁₂ ) alkoxy, primary, secondary or tertiary Grade Mino _(C 1 _{-C 12)} alkyl, and is selected from acetyl, substituents on said aryl, linear or branched _(C 1 -C ₅₎ alkyl, hydroxyl, hydroxy _(C 1 -C ₅₎ alkyl, ( Selected from the group consisting of C ₁ -C ₃ ) alkoxy and primary, secondary and tertiary amino (C ₁ -C ₅ ) alkyl;
The indium electroplating composition is free of alloying metals; and
Contacting the indium electroplating composition with an indium electroplating composition which does not contain a compound of the following formula (II) :
_{H-A 'p -Q- [C} (O) -CH 2 O - ((R 1 CH) t -O) Z -CH 2 -C (O) -NH-A] u -H (II)
(Wherein, A ′ is — (NH— (CH ₂ ) _{x ′} ) _{y ′} −; —NH (CH ₂ ) _{x ′} — (O— (CHR ₁ ) _{r ′} ) _w′— O— (CH ₂ ) _{x '-;} or _{-NH - ((R 1 CH)} r' -O) w '-C 2 H 4 - a and,
A is — (CH ₂ ) _x —NH) _y —; — ( CH ₂ ) _x — (O— (CHR ₁ ) _r ) _w —O— (CH ₂ ) _x —NH—; or — ((R ₁ CH) _r -O) _w -C ₂ H ₄ -NH-;
R ₁ is -H or -CH ₃ ,
Q is -NH- when p = 1 or -O- when p = 0,
p is 0 or 1, where H-and Q form a chemical bond when p = 0,
r 'is an integer of 2 to 4,
w 'is an integer of 1 to 50,
x 'is an integer of 2 to 6,
y 'is an integer of 0 to 5,
Where H- and Q form a chemical bond when y 'is 0,
r is an integer of 2 to 4,
w is an integer of 1 to 50,
x is an integer of 2 to 6,
y is an integer from 0 to 5, where H- is attached to the nitrogen of the terminal -C (O) -NH- when y is 0,
t is an integer of 2 to 4,
u is an integer of 1 to 20,
w is an integer of 1 to 50, and
z is an integer of 1 to 50)
c) electroplating an indium metal layer on the metal layer of the substrate with the indium electroplating composition. 9. The method of claim 8 , wherein the indium electroplating composition further comprises one or more sources of chloride ions, and the molar ratio of the chloride ions to the indium ions is 2 : 1 or greater . The method according to claim 8 or 9 , wherein the metal layer is nickel, copper, gold or tin. 11. The method of claim 10 , wherein the metal layer is nickel. The method according to any one of claims 8 to 11 , wherein the metal layer is 10 nm to 100 μm thick. The method according to any one of claims 8 to 12 , wherein the indium metal layer is 10 nm to 100 μm thick.