Hydrodynamic Investigation of Ultraclean Wafer Drying Combining Marangoni Effect and Centrifugal Force

Abstract

The Marangoni effect induced by organic vapor has drawn considerable attention in integrated circuit manufacturing for eliminating watermark defects encountered in the wafer drying process. Accordingly, a vertical rotational Marangoni (VRM) dryer based on the combination of the Marangoni effect and centrifugal force is proposed and developed. In particular, the hydrodynamic behavior of the VRM dryer is investigated to reveal the mechanism of ultraclean drying. A three-dimensional model of the VRM dryer is proposed, and the flow field of the water film and distribution of organic species are adequately analyzed. The results show that the rotational velocity and wettability significantly affect the coverage uniformity of the water film, and the exposure region at the three-contact line leads to the watermark. Furthermore, the coupling behavior of the Marangoni effect and centrifugal force is revealed. A higher rotational velocity leads to worse integrity of the water film covering, and thus, fainter Marangoni effect. Polishing and cleaning experiments are conducted to verify the effectiveness of theoretical analysis. The results indicate that the optimized rotational velocity for the hydrophilic surface is higher than that of the hydrophobic surface. The mechanism analysis of wafer drying based on the VRM drying technology provides effective guidance for ultraclean surface manufacturing during the cleaning process.