Ligand Effects in Electroless Copper Deposition

Abstract

The induction period and cathodic processes in electroless deposition of copper have been studied by galvanostatic, chronopotentiometric, and potential sweep methods. It is shown that the factors which determine the duration of the induction period are the type and concentration of the ligand that is complexing the copper ions. The rate‐determining factor is the rate of establishment of the potential of the partial anodic process. Dissociation of a copper complex preceding the charge transfer in the electrochemical and electroless deposition of copper has been studied by chronopotentiometry and potential sweep method. Chronopotentiometric and potential sweep functions have been used to estimate the relative rates of dissociation. The properties of the complexes of Cu(II) with ethylenediaminetetraacetic acid (EDTA), N,N,N',N'‐tetrakis‐2 (2‐hydroxypropyl)ethyl‐enediamine (Quadrol), cyclohexane‐1, 2‐diamine‐N,N,N',N'‐tetraacetic acid (CDTA), and tartaric acid have been studied. The galvanostatic transient technique has been used for kinetic studies of copper deposition. A definite correlation has been established between the rate of dissociation of the complex and the rate of metal deposition. The rate of deposition of copper and the rate of dissociation of complex as a function of a ligand increase in the order: tartrate, EDTA, Quadrol, CDTA complex.