Method to Electrodeposit Metals Using Ionic Liquids in the Presence of an Additive

Abstract

The present invention pertains to the use of an additive selected from the group consisting of amorphous silica, graphite powder, and a mixture thereof in a process to electroplate or electropolish a metal on a substrate using an ionic liquid as the electrolyte to increase metal layer thickness. It furthermore pertains to a method to electroplate or electropolish a metal on a metal substrate wherein an ionic liquid is employed as electrolyte, wherein a metal salt added to said ionic liquid or a metal anode is employed as metal source, and wherein said ionic liquid comprises said additive.

1 . A method for increasing metal layer thickness on a substrate, comprising electroplating or electropolishing a metal on said substrate using an ionic liquid as the electrolyte, said electrolyte comprising an additive selected from the group consisting of amorphous silica, graphite powder, and a mixture thereof. 
     
     
         2 . The method of  claim 1  wherein the ionic liquid is selected from the group consisting of N + R 1 R 2 R 3 R 4  X − , N + R 5 R 6 R 7 R 8  Y − , and mixtures thereof, wherein any one of R 1  to R 8  independently represents a hydrogen, alkyl, cycloalkyl, aryl, or aralkyl group that may be substituted with a group selected from OH, Cl, Br, F, I, phenyl, NH 2 , CN, NO 2 , COOR 9 , CHO, COR 9 , or OR 9 , wherein at least one of R 1  to R 4  is an, optionally branched, fatty alkyl chain, wherein R 2  can be a (C 2 -C 6  alkyl)-N + R 16 R 17 R 18  group with R 16 , R 17 , R 18  being similar to R 1 , R 3 , R 4 , respectively, or a C 1  to C 4  alkyl chain, and wherein one or more of R 1  to R 8  can be a (poly)oxyalkylene group wherein the alkylene is a C 1  to C 4  alkylene and the total number of oxyalkylene units can be from 1 to 50 oxyalkylene units, and wherein at least one of R 1  to R 8  is a C 1  to C 4  alkyl chain, wherein R 9  is an alkyl or cycloalkyl group, wherein X −  is an anion compatible with the N + R 1 R 2 R 3 R 4  ammonium cation, such as a halogenide anion, a carboxylate anion, a sulphate (both organic and inorganic sulphate), sulphonate, carbonate, nitrate, nitrite, thiocyanate, hydroxide, saccharinate anion, or sulphonylimide anion, and wherein Y −  is an anion having a sulfonylimide anion or an N-acyl sulphonylimide anion (—CO—N − —SO 2 —) functionality. 
     
     
         3 . The method of  claim 1  wherein the metal which is electroplated or electropolished on the substrate originates from a metal source either being a metal salt selected from the group consisting of chromium, aluminium, titanium, zinc and copper salts, or an anode selected from the group consisting of chromium, aluminium, titanium, zinc, and copper anodes. 
     
     
         4 . The method of  claim 1  wherein the molar ratio of the cation of the ionic liquid to the metal cation of the metal salt or derived from the metal anode is between 1,000:1 and 3:1. 
     
     
         5 . The method of  claim 4  wherein said additive is present in an amount of between 0.1 wt % and 5 wt %, based on the total weight of electrolyte. 
     
     
         6 . The method of  claim 1  wherein the ionic liquid is selected from choline saccharinate, choline acesulphamate, hexadecyltrimethyl ammonium chloride, octadecyltrimethyl ammonium chloride, cocotrimethyl ammonium chloride, tallowtrimethyl ammonium chloride, hydrogenated tallowtrimethyl ammonium chloride, hydrogenated palmtrimethyl ammonium chloride, oleyltrimethyl ammonium chloride, soyatrimethyl ammonium chloride, cocobenzyldimethyl ammonium chloride, C 12-16 -alkylbenzyldimethyl ammonium chloride, hydrogenated tallowbenzyldimethyl ammonium chloride, dioctyldimethyl ammonium chloride, didecyldimethyl ammonium chloride, dicocodimethyl ammonium nitrite, dicocodimethyl ammonium chloride, di(hydrogenated tallow)dimethyl ammonium chloride, di(hydrogenated tallow)benzylmethyl ammonium chloride, ditallowdimethyl ammonium chloride, dioctadecyldimethyl ammonium chloride, hydrogenated tallow(2-ethylhexyl)dimethyl ammonium chloride, hydrogenated tallow(2-ethylhexyl)dimethyl ammonium methylsulphate, trihexadecylmethyl ammonium chloride, octadecylmethylbis(2-hydroxyethyl) ammonium chloride, cocobis(2-hydroxyethyl)methyl ammonium nitrate, cocobis(2-hydroxyethyl) methyl ammonium chloride, cocobis(2-hydroxyethyl)benzyl ammonium chloride, oleylbis(2-hydroxyethyl)methyl ammonium chloride, coco[polyoxyethylene(15)]methyl ammonium chloride, coco[polyoxyethylene(15)]methyl ammonium methylsulphate, coco[polyoxyethylene(17)]methyl ammonium chloride, octadecyl[polyoxy-ethylene(15)]methyl ammonium chloride, hydrogenated tallow[polyoxy-ethylene(15)]methyl ammonium chloride, tris(2-hydroxyethyl)tallow ammonium acetate, tallow-1,3-propane pentamethyl diammonium dichloride, or a mixture or combination thereof. 
     
     
         7 . A method to electroplate or electropolish a metal on a metal substrate wherein an ionic liquid is selected from the group consisting of N + R 1 R 2 R 3 R 4  X − , N + R 5 R 6 R 7 R 8  Y − , and mixtures thereof, wherein any one of R 1  to R 8  independently represents a hydrogen, alkyl, cycloalkyl, aryl, or aralkyl group that may be substituted with a group selected from OH, Cl, Br, F, I, phenyl, NH 2 , CN, NO 2 , COOR S , CHO, COR S , or OR 9 , wherein at least one of R 1  to R 4  is an, optionally branched, fatty alkyl chain, wherein R 2  can be a (C 2 -C 6  alkyl)-N + R 16 R 17 R 18  group with R 16 , R 17 , R 18  being similar to R 1 , R 3 , R 4 , respectively, or a C 1  to C 4  alkyl chain, and wherein one or more of R 1  to R 8  can be a (poly)oxyalkylene group wherein the alkylene is a C 1  to C 4  alkylene and the total number of oxyalkylene units can be from 1 to 50 oxyalkylene units, and wherein at least one of R 1  to R 8  is a C 1  to C 4  alkyl chain, wherein R 9  is an alkyl or cycloalkyl group, wherein X −  is an anion compatible with the N + R 1 R 2 R 3 R 4  ammonium cation, such as a halogenide anion, a carboxylate anion, a sulphate (both organic and inorganic sulphate), sulphonate, carbonate, nitrate, nitrite, thiocyanate, hydroxide, saccharinate anion, or sulphonylimide anion, and wherein Y −  is an anion having a sulfonylimide anion or an N-acyl sulphonylimide anion (—CO—N − —SO 2 —) functionality; wherein a metal salt added to said ionic liquid or a metal anode is employed as metal source; and wherein said ionic liquid comprises at least 0.01 wt%, based on the total weight of electrolyte, of an additive selected from the group consisting of amorphous silica, graphite powder, and of a mixture thereof. 
     
     
         8 . The method according to  claim 7  wherein the metal which is electroplated or electropolished on the substrate originates from a metal source either being a metal salt selected from the group consisting of chromium, aluminium, titanium, zinc and copper salts, or an anode selected from the group consisting of chromium, aluminium, titanium, zinc, and copper anodes. 
     
     
         9 . The method of  claim 7  wherein the molar ratio of the cation of the ionic liquid to the metal cation of the metal salt or derived from the metal anode is between 1,000:1 and 3:1, and preferably between 100:1 and 7:1. 
     
     
         10 . The method of  claim 7  wherein the ionic liquid is selected from choline saccharinate, choline acesulphamate, hexadecyltrimethyl ammonium chloride, octadecyltrimethyl ammonium chloride, cocotrimethyl ammonium chloride, tallowtrimethyl ammonium chloride, hydrogenated tallowtrimethyl ammonium chloride, hydrogenated palmtrimethyl ammonium chloride, oleyltrimethyl ammonium chloride, soyatrimethyl ammonium chloride, cocobenzyldimethyl ammonium chloride, C 12-16 -alkylbenzyldimethyl ammonium chloride, hydrogenated tallowbenzyldimethyl ammonium chloride, dioctyldimethyl ammonium chloride, didecyldimethyl ammonium chloride, dicocodimethyl ammonium nitrite, dicocodimethyl ammonium chloride, di(hydrogenated tallow)dimethyl ammonium chloride, di(hydrogenated tallow)benzylmethyl ammonium chloride, ditallowdimethyl ammonium chloride, dioctadecyldimethyl ammonium chloride, hydrogenated tallow(2-ethylhexyl)dimethyl ammonium chloride, hydrogenated tallow(2-ethylhexyl)dimethyl ammonium methylsulphate, trihexadecylmethyl ammonium chloride, octadecylmethylbis(2-hydroxyethyl) ammonium chloride, cocobis(2-hydroxyethyl)methyl ammonium nitrate, cocobis(2-hydroxyethyl)methyl ammonium chloride, cocobis(2-hydroxyethyl)benzyl ammonium chloride, oleylbis(2-hydroxyethyl)methyl ammonium chloride, coco[polyoxyethylene(15)]methyl ammonium chloride, coco[polyoxyethylene(15)]methyl ammonium methylsulphate, coco[polyoxyethylene(17)]methyl ammonium chloride, octadecyl[polyoxyethylene(15)]methyl ammonium chloride, hydrogenated tallow[polyoxyethylene(15)]methyl ammonium chloride, tris(2-hydroxyethyl)tallow ammonium acetate, tallow-1,3-propane pentamethyl diammonium dichloride, or a mixture or combination thereof. 
     
     
         11 . The method of  claim 1  wherein the molar ratio of the cation of the ionic liquid to the metal cation of the metal salt or derived from the metal anode is between between 100:1 and 7:1.