In the cleaning process of semiconductor device manufacturing, it is necessary to control the velocity, frequency, and size of droplets of the two-fluid jet method to avoid the feature damage. In this study we attempted the control of droplets generation using capillary tube and surrounding airflow. The generation process is visualized by high-speed photography. As a result, the droplets generation frequency can be controlled in the wide range, by utilizing the resistance of the capillary tube. The droplet diameter monotonically decreases with the airflow rate increased. In addition, it is found that the transition from droplets to liquid column formation at the nozzle tip greatly affects the generated droplets size. Using different liquids, which have different viscosities and surface tensions, and capillary tubes of different contact angles, the transition condition is investigated. The results indicate that the inertia and surface tension of liquid have a dominant role and contact angles of capillary has a small influence.
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