Physical Simulation and Visualization of the Marangoni Convection inside Meniscus Region under IPA Vapor in Wafer Drying Process

Abstract

In cleaning and drying processes after chemical mechanical polishing process, there is a method of flowing pure water to a rotating wafer, and simultaneously supplying IPA (Iso-Propyl Alcohol) vapor to the meniscus region (this is known as Rotagoni drying). This method causes a surface tension difference on the liquid surface and then drives fluid convection by the Marangoni effect, which is thought to efficiently remove impure particles on the wafer surface. During the impingement of IPA vapor to the meniscus region, in-situ observation of Marangoni convection is technically difficult. In this study, physical simulation by creating a simplified two-dimensional flow was performed. Using MEMS device technique, a two-dimensional flow channel was created, and pure water and IPA vapor was supplied to reproduce the situation, and the flow was visualized by utilizing PIV (Particle Image Velocimetry) method. The flow velocities and the flow patterns were successfully obtained from the image analysis. The surface flow with IPA vapor was in the reversed direction of that with only nitrogen gas, and the velocity became larger.