Flow structure and agitation effect of liquid film flow formed by the two-fluid jet: prediction of etching rate distribution in wet processing

Abstract The two-fluid jet method, which accelerates droplets using a high-speed airflow, has been widely utilized in single-wafer wet processing, including etching or cleaning. This study experimentally investigated the liquid film flow formed by the two-fluid jet by varying the water and airflow rates. We also measured the agitations that contribute to the etching rate, focusing on the relationship between the mass transfer and heat transfer of the liquid film. Consequently, a relatively thick liquid film consistently existed directly below the nozzles that thinned rapidly in adjacent regions, and circular hydraulic jumps occurred. In particular, the two-fluid jet demonstrated a uniform heat-flux distribution over a wide range within the hydraulic jump. These results indicate the potential for achieving high uniformity in the wet processing of wafers using the two-fluid jet method. Notably, the two-fluid jet method enables easy control of a uniform agitation zone simply by varying the airflow rate.