In a single wafer spin cleaner, the wafer is rotated at high speed to spin off ultrapure water and clean air is blown perpendicular onto the surface to dry the wafer. Interaction between the rotating wafer and blown air generates vortices and the recirculation flow due to the vortices may cause reattachment of contaminants on the wafer surface. Therefore, we experimentally studied vortical structures and the conditions of their formation in a modeled cleaner by using particle image velocimetry (PIV). The model was a 330 mm diameter rotating disk in a 520 mm diameter cylindrical stationary housing, and laminar blown air came from the housing inlet onto the rotating disk. The angular speed of the rotating disk was changed up to 500 rpm and the blown air rate was 0.5 m3/min. Our PIV data show that turbulent kinetic energy near the housing wall with a vortex is as large as that around the rotating disk around at SOOrpm. This vortex may cause reattachment of particles onto the wafer. The vortices generated in the experimental apparatus have three-dimensional structures regardless of their size.
