Seedless electrochemical deposition of copper on physical vapor deposition-W2N liner materials for ultra large scale integration (ULSI) devices

Electrochemical studies are designed to identify processes that provide adequate nucleation and thin film growth directly on ultrathin, air-exposed physical vapor deposition (PVD)-tungsten nitride diffusion barriers. In this study, it is shown that very thin copper films can be nucleated directly on a conducting PVD-W2N liner surface. A complex chemistry model based on mass balance and thermodynamic equilibrium has been applied to numerous ammoniacal platting bath compositions and the resulting concentration profiles inserted into the Nernst equation. Comparing the experimental results with the predicted model indicates that a strong adhesion is associated with the reduction of several copper-ammonia complexes at the metal nitride surface, Nucleation, growth mechanisms, and film resistivity are found to be dependent on the reduction potential, electrolyte velocity, and platting bath chemistry.