Numerical Investigation of Flow Entering the Top of the Wafer in Single-Wafer Wet Cleaner

This study investigates factors contributing to process defects in the single wafer wet cleaner equipment used for semiconductor wet cleaning processes. For a possible cause of defects in the cleaning process, we suspect the presence of a radially inward flow during the drying step where the cleaning process is completed. We explore the complex flow characteristics of the rotational structure to investigate the backflow in the radial direction. The wafer rotation structure, with a disk-shaped coaxial design, induces radial backflow on the wafer side. On the other hand, when a guide structure is present, backflow occurs along the guide, and it was observed that the flow through the guide structure increases with an increase in exhaust pressure. Backflow through the lower part of the guide, influenced by the vortex generated by exhaust pressure and guide, was identified. We propose a method to improve backflow by adjusting the position of the guide edge to enhance the inflow through the guide's upper part.