Indium electroplating compositions and methods for electroplating indium

Abstract

Indium electroplating compositions electroplate substantially defect-free uniform layers which have a smooth surface morphology on metal layers. The indium electroplating compositions can be used to electroplate indium metal on metal layers of various substrates such as semiconductor wafers and as thermal interface materials.

1 : An indium electroplating composition comprising one or more sources of indium ions, wherein the one or more sources of indium ions are chosen from indium salts of alkane sulfonic acids, indium salts of aromatic sulfonic acids, indium salts of sulfamic acid, sulfate salts of indium, nitrate salts of indium, hydroxide salts of indium, indium oxides, fluoroborate salts of indium, indium salts of carboxylic acids and indium salts of amino acids, one or more thiourea derivatives and citric acid, salts thereof or mixtures thereof, wherein the indium electroplating composition is free of alloying metals, and, wherein a pH of the indium electroplating composition is 1-4. 
     
     
         2 : The indium electroplating composition of  claim 1 , wherein the thiourea derivatives are chosen from guanylthiourea, 1-allyl-2-thiourea, 1-acetyl-2-thiourea, 1-benzoyl-2-thiourea, 1-benzyl-2-thiourea, 1-butyl-3-phenyl-2-thiourea, 1,1-dimethyl-2-thiourea, tetramethyl-2-thiourea, 1,3-dimethyl thiourea, 1-methyl thiourea, 1,3-diethyl thiourea, 1,1-diphenyl-2-thiourea, 1,3-diphenyl-2-thiourea, 1,1-dipropyl-2-thiourea, 1,3-dipropyl-2-thiourea, 1,3-diisopropyl-2-thiourea, 1,3-di(2-tolyl)-2-thiourea, 1-methyl-3-phenyl-2-thiourea, 1(1-naphthyl)-3-phenyl-2-thiourea, 1(1-naphthyl)-2-thiourea, 1(2-naphthyl)-2-thiourea, 1-phenyl-2-thiourea, 1,1,3,3-tetramethyl-2-thiourea and 1,1,3,3-tetraphenyl-2-thiourea. 
     
     
         3 : The indium electroplating composition of  claim 2 , wherein the thiourea derivatives are chosen from guanylthiourea, 1-allyl-2-thiourea and tetramethyl-2-thiourea. 
     
     
         4 : The indium electroplating composition of  claim 1 , wherein the one or more thiourea derivatives is included in the composition in amounts of 0.01 g/L to 50 g/L. 
     
     
         5 : The indium electroplating composition of  claim 1 , wherein the composition further comprises one or more sources of chloride ions, wherein a molar ratio of the chloride ions to the indium ions is 2:1 or greater. 
     
     
         6 : The indium electroplating composition of  claim 5 , wherein the molar ratio of chloride ions to indium ions is 2:1 to 7:1. 
     
     
         7 : The indium electroplating composition of  claim 6 , wherein the molar ratio of chloride ions to indium ions is 4:1 to 6:1. 
     
     
         8 : The indium electroplating composition of  claim 1 , further comprising one or more surfactants chosen from amine surfactants, ethoxylated naphthols, sulfonated naphthol polyethers, (alkyl) phenol ethoxylates, sulfonated alkylalkoxylates, alkylene glycol alkyl ethers and sulfopropylated polyalkoxylated beta-naphthol alkali salts. 
     
     
         9 : The indium electroplating composition of  claim 1 , further comprising one or more copolymers of a reaction product of epihalohydrin and one or more nitrogen-containing organic compounds. 
     
     
         10 : A method comprising:
 a) providing a substrate comprising a metal layer;   b) contacting the substrate with an indium electroplating composition comprising one or more sources of indium ions, wherein the one or more sources of indium ions are chosen from indium salts of alkane sulfonic acids, indium salts of aromatic sulfonic acids, indium salts of sulfamic acid, sulfate salts of indium, nitrate salts of indium, hydroxide salts of indium, indium oxides, fluoroborate salts of indium, indium salts of carboxylic acids and indium salts of amino acids, one or more thiourea derivatives and citric acid, salt of citric acid or mixtures thereof, wherein the indium electroplating composition is free of alloying metals, and, wherein a pH of the indium electroplating composition is 1-4; and   c) electroplating an indium metal layer on the metal layer of the substrate with the indium electroplating composition.   
     
     
         11 : The method of  claim 10 , wherein the one or more thiourea derivatives is included in the indium electroplating composition in amounts of 0.01 g/L to 50 g/L. 
     
     
         12 : The method of  claim 10 , wherein the indium electroplating composition further comprises one or more sources of chloride ions, wherein a molar ratio of the chloride ions to the indium ions is 2:1 or greater. 
     
     
         13 : The method of  claim 10 , wherein the metal layer is nickel, copper, gold or tin. 
     
     
         14 : The method of  claim 13 , wherein the metal layer is nickel. 
     
     
         15 : The method of  claim 10 , wherein the metal layer is 10 nm to 100 μm thick. 
     
     
         16 : The method of  claim 10 , wherein the indium metal layer is 10 nm to 100 μm thick. 
     
     
         17 : The indium electroplating composition of  claim 1 , wherein the pH is from 2-3. 
     
     
         18 : The method of  claim 10 , wherein the pH of the indium electroplating composition is from 2-3.