Two-step deposition with improved selectivity

Abstract

A method for providing an electroless plating over at least one copper containing layer is provided. Surfaces of the at least one copper containing layer are sealed by selectively depositing a sealing layer of catalytically active metal on the at least one copper containing layer. The sealing layer is exposed to an electroless deposition bath that is more reactive to the catalytically active metal than to the at least one copper containing layer to provide an electroless deposition on the sealing layer.

What is claimed is: 
     
         1 . A sealing bath for sealing copper layers, comprising:
 a borane containing component;   a metal containing reagent comprising ions of at least one of Co, Ni, or Pd;   citric acid monohydrate, and   boric acid.   
     
     
         2 . The sealing bath, as recited in  claim 1 , wherein the sealing bath is oxygen free. 
     
     
         3 . The sealing bath, as recited in  claim 2 , wherein the metal containing reagent comprises cobalt sulfate heptahydrate. 
     
     
         4 . The sealing bath, as recited in  claim 3 , wherein the borane containing component comprises dimethylamine borane. 
     
     
         5 . The sealing bath, as recited in  claim 4 , wherein the sealing bath has a pH of 9. 
     
     
         6 . The sealing bath, as recited in  claim 5 , further comprising tetramethylammonium hydroxide, which is used to adjust pH. 
     
     
         7 . The sealing bath, as recited in  claim 1 , wherein the metal containing reagent comprises cobalt sulfate heptahydrate. 
     
     
         8 . The sealing bath, as recited in  claim 1 , wherein the borane containing component comprises dimethylamine borane. 
     
     
         9 . The sealing bath, as recited in  claim 1 , wherein the sealing bath has a pH of 9. 
     
     
         10 . The sealing bath, as recited in  claim 1 , further comprising tetramethylammonium hydroxide, which is used to adjust pH. 
     
     
         11 . The sealing bath, as recited in  claim 1 , wherein the sealing bath consists essentially of 40-50 mM cobalt sulfate heptahydrate, 140-160 mM citric acid monohydrate, 75-150 mM boric acid, 25-40 mM dimethylamine borane at a pH of 9, adjusted by tetramethylammonium hydroxide.