Effect of grain size on tungsten material removal rate during chemical mechanical planarization process.

The effect of grain size on the tungsten (W) material removal rate (MRR) was studied during chemical mechanical planarization (CMP) process in this paper. It was found that the average grain size of atomic layer deposition (ALD) W was significantly smaller than that of chemical vapor deposition (CVD) W by TEM and SEM analysis. The MRR of ALD W with small grain size was higher than that of CVD W with large grain size. The static etch rate and XPS results indicated that the W film with smaller grain size had a higher oxidation rate, which were further demonstrated by the analysis of potentiodynamic polarization and the electrochemical impedance spectroscopy (EIS). This can be explained that W film with smaller grain size has a higher grain boundary density, leading to easier oxidizers diffusion along the grain boundaries and faster oxidation in the W film surface consequently. According to the oxidation-removal model, it is concluded that smaller grain size facilitates faster oxidation on the W film surface, leading to higher material removal rates during W CMP process. [ABSTRACT FROM AUTHOR]