Autocatalysis during Electroless Copper Deposition using Glyoxylic Acid as Reducing Agent

Interactions between the cathodic and anodic processes during electroless Cu deposition using glyoxylic acid reducing agent are studied. It is shown that application of the mixed potential theory by decoupling the anodic and cathodic processes leads to erroneous predictions of the electroless deposition rate and the surface mixed potential observed in this electroless system. Chronoamperometry under various conditions of bath composition, electrode surface preparation and applied potential provides evidence for an autocatalytic mechanism in the glyoxylic acid based electroless Cu system. Specifically, it is observed that the electroless Cu surface accelerates the glyoxylic acid oxidation and the glyoxylic acid in turn enhances the cupric-ion reduction leading to a positive feedback loop. The autocatalysis explains shortcomings in the simplistic application of the mixed potential theory to the decoupled partial reactions, and suggests a more complex reaction mechanism in which the partial reactions are coupled. (C) 2013 The Electrochemical Society. All rights reserved.