Optimization of catalyzing process on Ta substrate for copper electroless deposition using electrochemical method

An electrochemical monitoring method was introduced to optimize catalyzing process prior to Cu electroless deposition on a TaTaN barrier. It utilized the electro-oxidation of dimethylaminoborane on the Pd particles formed on the substrate after the catalyzing process. The anodic current of the dimethylaminoborane oxidation was only detected when Pd particles existed, and its peak current showed a linear dependency on the Pd particle density. It was also found that the oxidation on Pd particles was an irreversible process accompanying 3-electron transfer. Using the electrochemical method, the optimization of the catalyzing process was performed to maximize the number of Pd particles per unit area (1 cm ²). After the optimization, Cu electroless deposition was performed. A minimum 18-nm-thick Cu seed layer was successfully obtained and the adhesion strength was good enough to maintain the flaking-free film even after Cu electrodeposition.