Experimental Investigation of Pressure and Velocity on Chemical Mechanical Planarization

Abstract

Chemical-mechanical planarization or polishing (CMP) is an emerging process used in surface planarization and polishing for semiconducter wafer with multilevel interconnections. This paper investigates the effects of polishing pressure and velocity on the material removal rate (RR) and the non-uniformity (NU) in the CMP process. Wear models for CMP process from mechanical aspect, including abrasive-based model and flow-based model, are first discussed. Experiments using different polishing pressures, velocities, and back pressures are then designed and conducted based on the Taguchi method. Experimental results showed that RR and NU are consistent with theoretical models in a certain range. Both RR and NU increase as polishing speed increases. As RR and NU also increase with the polishing pressure at low pressure, their values become saturated and then decrease when the pressure exceeds certain value. It further verified that NU can be improved using proper back pressure as predicted by the flow-based wear model.