Pulsed electrodeposition of copper from alkaline and acid baths for metallization in integrated circuits

Pulsed electroplating parameters for the electrodeposition of copper on patterned wafers were compared in alkaline and acid baths. In an alkaline bath with trace amounts of ethylenediamine added feature filling and smoothness were optimized for a reversed pulse cycles. In an acid bath containing commercial additives, the optimum parameters for good filling and smoothness were observed under direct current or forward pulse plating. The results of this work indicate that the specific plating parameters required for interconnects in integrated circuits are a strong function of the solution chemistry. In the case of alkaline baths, complexing of the copper results in a more uniform distribution of copper ion in the features and requires less dependence on mass transport and preferential nucleation of the copper plate.