Evaluation of K3Fe(CN)6 on deposition behavior and structure of electroless copper plating

Abstract

Potassium ferricyanide (K3Fe(CN)6) as a stabilizer was used for electroless copper plating in EDTA/THPED dual-ligands system. The deposition behavior and surface structure of copper layer were studied systematically. The results indicated that the overall deposition process was divided into three regions designated as induction, transitional and stable regions. It was confirmed that K3Fe(CN)6 can delay the fall-off trend of electrode potential, which may be related to the competitive adsorption between Fe(CN)63− with large radius and OH− with small radius on the electrode surface. The addition of K3Fe(CN)6 led to a decrease of 70% in redox current density, which reduced obviously Cu deposition rate. Meanwhile, the decomposition time of electroless solution sharply increased and the reoxidation of Cu(I) ion was effectively inhibited in the presence of K3Fe(CN)6. Metallographic studies of copper layers with and without K3Fe(CN)6 stabilizer revealed that surface structures and fine particle distribution were uniform. The resultant product was high-purity without detectable iron impurities. Moreover, the addition of K3Fe(CN)6 was favorable to the formation of the preferred orientation on (220) crystal plane, and the grain size decreased from 61.5 nm to 40.4 nm with the addition of 50 mg L−1 K3Fe(CN)6