Water Motion over a Wafer Surface Rotating in a Single-Water Wet Cleaner

Abstract

Water motion over a 200-mm diameter wafer surface rotating in a single-wafer wet cleaner was studied, using the water flow visualization technique with a video camera and blue-colored ink as the tracer. When the tracer was injected from the wafer center, it was seen to symmetrically spread over the rotating wafer surface from its center to the edge. The radial velocity of the water showed a negligibly small change over the wafer surface except at its center area. The water layer thickness in the rotation rate range between 500 and 1400 rpm was approximately 0.1 mm; it gradually decreased with the increasing rotation rate. The tracer injected from non-center positions showed that the water flow tended to be localized in the peripheral region of the wafer, particularly at the high rotation rates.