Indium electroplating compositions containing 2-imidazolidinethione compounds and methods for electroplating indium

Abstract

Indium electroplating compositions containing 2-imidazolidinethione compounds 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.

What is claimed is: 
     
         1 . An composition comprising one or more sources of indium ions, one or more 2-imidazolidinethione compounds and citric acid, salt thereof or mixtures thereof. 
     
     
         2 . The composition of  claim 1 , wherein the one or more 2-imidazolidinethione compounds have the following formula: 
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 2  are independently chosen from 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 )alkyl; R 3 , R 4 , R 5  and R 6  are independently chosen from hydrogen, linear or branched (C 1 -C 12 )alkyl, hydroxyl, linear 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 amino(C 1 -C 12 )alkyl and acetyl. Substituent groups on the aryl include, but are not limited to linear or branched (C 1 -C 5 )alkyl, hydroxyl, hydroxy(C 1 -C 5 )alkyl, (C 1 -C 3 )alkoxy and primary, secondary and tertiary amino(C 1 -C 5 )alkyl. 
     
     
         3 . The composition of  claim 2 , wherein the one or more 2-imidazolidinethione compounds are chosen from 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-imidazolidinethione, 4,5-dihydroxy-1-methyl-2-imidazolidinethione, 1-(2-hydroxyethyl)-2-imidazoladinethione, 1,3-bis(hydroxymethyl)-2-imidazolidinethione, 1-ethyl-5-(4-methoxyphenyl)-2-imidazoladinethione, 1,3-diethyl-4,5-dihydroxy-4,5-diphenyl-2-imidazolidinethione and 1,3 bis[(cyclohexylamino)methyl]-2-imidazolidinethione. 
     
     
         4 . The composition of  claim 1 , wherein the one or more 2-imidazolidinethione compounds are included in the composition in amounts of 0.005 g/l to 5 g/L. 
     
     
         5 . The 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 composition of  claim 5 , wherein the molar ratio of chloride ions to indium ions is 2:1 to 7:1. 
     
     
         7 . The composition of  claim 6 , wherein the molar ratio of chloride ions to indium ions is 4:1 to 6:1. 
     
     
         8 . The 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 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, one or more 2-imidazolidinethione compounds and citric acid, salt of citric acid or mixtures thereof; 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 2-imidazolidinethione compounds are included in the indium electroplating composition in amounts of 0.005 g/l to 5 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.