Superconformal Cobalt Fill through the Use of Sacrificial Oxidants

Abstract

Conventional damascene electroplating utilizes a combination of organic additives, namely, a suppressor, an accelerator, and a leveler, to achieve superconformal fill of interconnects. An alternative mechanism for superconformal cobalt fill is proposed here. This mechanism, the Differential Current Efficiency Fill (DCEF) mechanism, utilizes sacrificial oxidants to achieve void-free superconformal fill. In the DCEF mechanism, the presence of a sacrificial oxidant, such as H+, O2, or an organic additive, promotes a difference in metal deposition rate between the field and the feature bottom. Addition of a single suppressor-type additive assists in driving the plating rate differential. By appropriately selecting the sacrificial oxidants, organic additives, the waveform, and the mass transport conditions, void-free superconformal cobalt fill can be achieved in a variety of features.