Numerical Analysis of Single Bubble Behavior in a Megasonic Field by Non-Spherical Eulerian Simulation

Abstract

The mechanism of particle removal in megasonic cleaning needs to be clarified so that it can be controlled and used to clean nanodevices without causing pattern damage. Single bubble behavior in a standing megasonic wave was analyzed using a compressible locally homogeneous model of a gas-liquid two-phase medium. This simulation is the first step toward understanding the particle removal mechanism in megasonic cleaning. We confirmed that our numerical method simulated the characteristics of bubble translational motion in a standing wave, in which the direction of the movement due to the primary Bjerknes force changed at the resonant radius. When the initial position of the bubble was near a moving wall, even a bubble with a radius smaller than the resonant radius moved toward the pressure node. In the three-dimensional calculations, bubble collapse near a side wall induced a higher pressure on the side wall than the maximum pressure of the megasonic wave. The bubble dynamics calculation with gas diffusion indicated that the effect of the rectified diffusion was small because the effect of the dynamic bubble motion was dominant on a timescale of several milliseconds.