Measurement of Liquid Film Thickness Distribution Formed on a Two-fluid Jet Sprayed Surface Using a Fiber Optic Probe

Abstract

In single-wafer wet processes, the surface etch rate is strongly dependent not only on the concentration and temperature of the chemicals but also on the structure of the formed liquid film flow. The two-fluid jet method, widely used in the single wafer process, will cause a different liquid film structure from the single liquid jet. In this study, we investigated the liquid film structure formed by a two-fluid jet where many droplets are sprayed with a highvelocity air stream. Using a fiber-optic probe, we measured the liquid film thickness distribution by changing the air and water flow rate. The liquid film just below the irradiation is thicker than the single liquid jet and rapidly decreases around it, and circular hydraulic jumps occur at a greater distance. The jump radius varied significantly depending on the air flow rate and the temperature of the liquid. The different liquid film structure formed by the two-fluid jet differs in the areas that are just below the irradiation and hydraulic jump, expected different chemical reactions occur.