Search

Chemical mechanical planarization (CMP) is a key processing step in the fabrication of copper interconnects. The present work focuses on certain electroanalytical aspects of evaluating slurry materials of CMP to aid the new processing strategies for the sub-22 nm technology nodes. The test slurry uses sodium percarbonate, sodium bicarbonate, benzotriazole and colloidal silica as an oxidizer, a complexing additive, a dissolution inhibitor, and an abrasive agent, respectively. The experiments employ open circuit potential transients, voltammetry and impedance spectroscopy, along with tactically applied tribological conditions appropriate for processing Ru barrier lines. The removal of surface materials is based on controlled tribo-corrosion, while the effects of dissolution and galvanic corrosion are suppressed. The results of the different measurements are analyzed in a combined framework of mixed potential effects to probe the underlying mechanisms of material removal and corrosion suppression.

Chemical mechanical planarization (CMP) is routinely used in the fabrication of microelectronic devices. The surface chemistries of this technique have become quite complex with the emergence of the sub–22 nm technology nodes. While this has introduced new challenges in the field of slurry-engineering for CMP, certain electroanalytical techniques have been recognized as useful tools for the assessment of CMP slurry chemistries. In this regard, electrochemical impedance spectroscopy (EIS), a powerful probe of interfacial kinetics, can play a unique role in aiding the development/evaluation of new slurry formulations. To fully explore this capability of EIS in CMP research, it is necessary to address the experimental requirements and constraints of EIS that are linked to the mechanical component of planarization. The present work focuses on certain analytical aspects of this subject using an exploratory CMP scheme for Cu. The surface reactions of CMP are characterized here by tribologically controlled voltammetry and open circuit potentials in an alkaline slurry of H2O2 (oxidizer), guanidine nitrate (complexing agent), and colloidal SiO2 (abrasive). An experimental protocol is demonstrated to check the validation criteria of EIS for typical CMP systems. The EIS data are analyzed by complex nonlinear least square calculations, and the resulting parameters are used to corroborate the reaction mechanisms of CMP.