Effect of Pad Type on Passivation Film Formation Relevant to Copper Chemical Mechanical Planarization

Abstract

Copper (Cu) chemical mechanical planarization (CMP) is an extremely critical step in the manufacturing of ultra-large-scale integrated (ULSI) semiconductor devices. By optimizing the synergistic relationship between a chemical dispersion, referred to as a slurry, and mechanical parameters, global planarization is able to be achieved utilizing CMP. Traditional slurries for Cu CMP promote Cu oxidation, promoting the creation of a passivation film which readily able to be removed by the same mechanical process. However, the efficiency of film removability is strongly correlated to the molecular structure of the passivating agent and also the composition of the polyurethane polishing pad. This work aims to mechanistically understand the relationship between molecular structure of the passivating agent and the pad type on the modulation of the passivation film formed. The film formation kinetics and characteristics were studied through various electrochemical techniques and surface spectroscopy. Results have indicated that the film is directly correlated to the molecular structure of the passivating agent, and the ease of removing the film is strongly contingent on the type of polyurethane pad implemented in the CMP polishing process.