Kinetics and mechanism of electroless copper deposition at moderate-to-high copper ion and low-to-moderate formaldehyde concentrations

Abstract

Studies were carried out to establish the effect of moderate-to-high copper ion and low-to-moderate formaldehyde concentrations on electroless deposition of copper. The individual half-cell polarization curves were generated from a steady-state two-compartment cell as well as from potentiostatic measurements. The anodic and cathodic plots were superimposed on one another to get the mixed potential (E(m)) and mixed current(i(m)). Actual deposition rates were measured gravimetrically. At very low [HCHO] levels, E(m) was found to lie in the cathodic linear region and no copper deposition took place. Above a certain level of [HCHO], the E(m) and i(m) values were found to shift to a position in the cathodic Tafel region, resulting in a smooth deposit on the substrate surface. A kinetic expression, derived employing the Butler-Volmer equation, matched well with the experimental findings.