Use of Water Soluble Lanthanide Compounds As Stabilizer In Electrolytes For Electroless Metal Deposition

Abstract

The present invention relates to the use of water soluble lanthanide compounds as stabilizer in electrolytes for electroless metal deposition, an electrolyte as well as a method for the electroless deposition of metals, particularly layers of nickel, copper, cobalt, boron, silver, palladium or gold, as well as layers of alloys comprising at least one of the aforementioned metals as alloying metal.

1 . An aqueous electrolyte composition for the electroless deposition of a metal layer on a substrate, comprising a metal ion source for the metal to be deposited, a reducing agent, a complexing agent, an accelerator, and a stabilizer, characterized in that the electrolyte comprises as stabilizer a water-soluble lanthanide compound. 
     
     
         2 . The aqueous electrolyte composition according to  claim 1 , wherein the water-soluble lanthanide compound is comprised in a concentration between ≧0.05 mg/L and ≦100 mg/L. 
     
     
         3 . The aqueous electrolyte composition according to  claim 1 , wherein the metal to be deposited comprises at least one metal selected from the group consisting of nickel, copper, cobalt, boron, silver, and gold. 
     
     
         4 . The aqueous electrolyte composition according to  claim 3 , wherein the accelerator is at least one accelerator of selected from the group consisting of saccharine, hydantoin, rhodanine, carbamide and carbamide derivates. 
     
     
         5 . The aqueous electrolyte composition according to  claim 3 , wherein the electrolyte is essentially free of inorganic stabilizers. 
     
     
         6 . The aqueous electrolyte composition according to  claim 3 , wherein the composition is essentially free of cyanides, selenium compounds and sulfur compounds comprising sulfur in an oxidation state between −2 and +5. 
     
     
         7 . The aqueous electrolyte composition according to  claim 3 , further comprising at least one additional carboxylic acid and/or at least one salt of a carboxylic acid. 
     
     
         8 . The aqueous electrolyte composition according to  claim 7 , wherein the carboxylic acid is a compound of the group consisting of acrylic acids, aromatic carboxylic acids, fatty acids, aliphatic carboxylic acids, keto acids, dicarboxylic acids, tricarboxylic acids, straight chained carboxylic acids, heterocyclic carboxylic acids, saturated carboxylic acids, unsaturated carboxylic acids, and α-hydroxy acids. 
     
     
         9 . The aqueous electrolyte composition according to  claim 3 , wherein the pH-value of the composition is in the range of between pH 4 and pH 7. 
     
     
         10 . The aqueous electrolyte composition according to  claim 3 , wherein the reducing agent is at least one compound of the group consisting of sodium hypophosphite, formaldehyde, dimethyl aminoborane, amino borane, and other organic boranes. 
     
     
         11 . The aqueous electrolyte composition according to  claim 3 , wherein the complexing agent is at least one compound of the group consisting of 2-hydroxy propionic acid, propanedioic acid, EDTA and amino acetic acid. 
     
     
         12 . A method for the electroless deposition of a metal layer on a substrate comprising the steps of contacting the substrate to be plated with an electrolyte comprising a metal ion source for the metal to be deposited, a reducing agent, a complexing agent, an accelerator, and a stabilizer, characterized in that the electrolyte comprises as stabilizer a water-soluble lanthanide compound. 
     
     
         13 . The method according to  claim 12 , wherein the substrate is contacted with the electrolyte at a temperature within the range of between ≧20° C. and 85° C. 
     
     
         14 . The method according to  claim 12 , wherein the substrate is contacted with the electrolyte for a time between ≧1 s and ≦180 min. 
     
     
         15 . (canceled) 
     
     
         16 . The method according to  claim 12 , wherein the water-soluble lanthanide compound is comprised in a concentration between ≧0.05 mg/L and ≦100 mg/L. 
     
     
         17 . The method according to  claim 12 , wherein the metal to be deposited comprises at least one metal selected from the group consisting of nickel, copper, cobalt, boron, silver, and gold. 
     
     
         18 . The method according to  claim 17 , wherein the accelerator is at least one accelerator of the group consisting of saccharine, hydantoin, rhodanine, carbamide and carbamide derivates. 
     
     
         19 . The method according to  claim 17 , wherein the electrolyte is essentially free of inorganic stabilizers. 
     
     
         20 . The method according to  claim 17 , wherein the composition is essentially free of cyanides, selenium compounds and sulfur compounds comprising sulfur in an oxidation state between −2 and +5. 
     
     
         21 . The method according to  claim 17 , further comprising at least one additional carboxylic acid and/or at least one salt of a carboxylic acid. 
     
     
         22 . The method according to  claim 21 , wherein the carboxylic acid is a compound of the group consisting of acrylic acids, aromatic carboxylic acids, fatty acids, aliphatic carboxylic acids, keto acids, dicarboxylic acids, tricarboxylic acids, straight chained carboxylic acids, heterocyclic carboxylic acids, saturated carboxylic acids, unsaturated carboxylic acids, and α-hydroxy acids. 
     
     
         23 . The aqueous electrolyte composition according to  claim 2 , wherein the water-soluble lanthanide compound is comprised in a concentration between ≧0.1 mg/L and ≦25 mg/L. 
     
     
         24 . The aqueous electrolyte according to  claim 23 , wherein the water-soluble lanthanide compound is comprised in a concentration between ≧0.5 mg/L and 10 mg/L. 
     
     
         25 . The aqueous electrolyte composition according to  claim 1 , wherein the electrolyte is essentially free of lead, bismuth, zinc and/or tin. 
     
     
         26 . The method according to  claim 13 , wherein the substrate is contacted with the electrolyte at a temperature within the range of between ≧25° C. and ≦70° C. 
     
     
         27 . The method according to  claim 14 , wherein the substrate is contacted with the electrolyte for a time between ≧10 s and ≦60 min.