Experimental Investigation on the Roles of Chemical Corrosion and Mechanical Polishing on Copper CMP

Abstract

This paper is an experimental investigation on the roles of chemical corrosion and mechanical polishing of the chemical mechanical polishing (CMP) of wafers with copper film of 1,000 nm thickness. Three types of experiments are designed and conducted: chemical corrosion, mechanical polishing, and CMP with φ0.3μm Al2O3 as abrasives. The results showed that copper films after PVD and annealing sustain tensile stress that intensifies corrosion rate. In general, the stress of copper film increases at higher annealing temperature and the corrosion rate increases correspondingly though the relationship is weak. The polishing rate of pure mechanical polishing is about the same as that of pure chemical corrosion, but surface roughness of mechanical polishing and CMP are much better than that of chemical corrosion. Furthermore, the removal rate of mechanical polishing and chemical corrosion, about 2nm/min, are relatively low compared to that of CMP, about 30nm/min, it indicates that the removal mechanism of CMP is not simply a linear superposition of chemical corrosion and mechanical polishing. The strong interaction and the combined reaction of chemical corrosion and mechanical polishing need further investigation.