Water flow in an overflow rinse bath of the carrierless wet station for cleaning silicon wafers of 300 mm diam was studied, from the view point of the transport phenomena. Both the experiment of flow visualization and the numerical calculation using the transport equations show that the direction and the velocity distribution of the water from the water nozzle can be optimized by adjusting the wall thickness of the water nozzle. Additionally, this direction is shown to influence the water motion in the entire rinse bath and that between the wafers. Theoretical calculations taking the entire geometry and the detail of the water nozzle into account are shown to be applicable to predict and design the water flow in the wet cleaning bath. (C) 2004 The Electrochemical Society.