Mechanisms of Material Removal in the Cmp Process

The Chemical Mechanical Polishing (CMP) process is now widely employed in the manufacture of Ultra-Large-Scale Integrated (ULSI) circuits. Yet, the effects of various process parameters on the material removal rate (MRR) and the resulting surface topography are not well understood. In this chapter, accordingly, several polishing models are reviewed with emphasis on the mechanical aspects of CMP. Experiments are conducted to verify the mechanical polishing models and to identify the dominant mechanism of material removal under typical CMP conditions. The effects of such important process parameters as the hardness of material being polished, pad stiffness and the abrasive size on MRR, Preston constant, wear coefficient, within-wafer nonuniformity and surface roughness are investigated. Process optimization schemes for enhancing MRR and Preston constant and for meeting the process specifications are also proposed.