The effect of surface wettability on the frictional condition for PVA roll brush

INTRODUCTION As the future size of semiconductor device rapidly shrinking, the surface contamination becomes the critical issues. Especially CMP process essentially contains nano-scale particles that must be removed before the next process. Typically PVA (PolyVinyl Acetal) brush is used for cleaning such contaminations. However the mechanisms of brush cleaning are still under discussion. Hydrodynamic drag force, direct contact of brush, and so on, have been proposed as a cleaning mechanisms [1-5]. Recently, we measured the shear and normal forces due to PVA brush rotation and evaluated the coefficient of friction [6]. The results indicate that the coefficient of friction shows relatively large value and the value is decreased as the rotation speed increased. This suggests that the tribological contact condition between the brush and surface are outside of the fluid lubrication regime. In this study, we change the wettability of the surfaces and measure the coefficient of friction between surface and PVA brush. We discuss the effect of water existing inside and around the brush on the contact condition.