Published online by Cambridge University Press: 06 April 2017
Clarifying the mechanism of particle removal by megasonic cleaning and multiple-bubble dynamics in megasonic fields is essential for removing contaminant particles during nanodevice cleaning without pattern damage. In particular, the effect of the interaction of multiple bubbles on bubble-collapse behaviour and impulsive pressure induced by bubble collapse should also be discussed. In this study, a compressible locally homogeneous model of a gas–liquid two-phase medium is used to numerically analyse the multiple-bubble behaviour in a megasonic field. The numerical results indicate that, for bubbles with the same equilibrium radius, the natural frequency of the bubble decreases, and bubbles with smaller equilibrium radii resonate with the megasonic wave as the number of bubbles increases. Therefore, the equilibrium radius of bubbles showing maximum wall pressure decreases with an increasing number of bubbles. The increase in bubble number also results in chain collapse, inducing high wall pressure. The effect of the configuration of bubbles is discussed, and the bubble–bubble interaction in the concentric distribution makes a greater contribution to the decrease in the natural frequency of bubbles than the interaction in the straight distribution.
Time evolution of pressure distribution on the side wall and isosurface of the void fraction α = 0:5 (R0 = 2:0 μm, single bubble)
Time evolution of pressure distribution on the side wall and isosurface of the void fraction α = 0:5 (R0 = 1:4 μm, seven bubbles, circular distribution)
Time evolution of pressure distribution and isoline of the void fraction α = 0:5 on the z plane (R0 = 1:6 μm, nine bubbles, circular distribution)
Time evolution of pressure distribution on the side wall and isosurface of the void fraction α = 0:5 (R0 = 2:0 μm two bubbles)
Time evolution of pressure distribution on the side wall and isosurface of the void fraction α = 0:5 (R0 = 2:0 μm, three bubbles)
Time evolution of pressure distribution on the side wall and isosurface of the void fraction α = 0:5 (R0 = 1:6 μm, nine bubbles)
Time evolution of pressure distribution and isoline of the void fraction α = 0:5 on the z = 0 plane during the inner bubble collapse (R0 = 1:6 μm, nine bubbles)
Time evolution of pressure distribution on the side wall and isosurface of the void fraction α = 0:5 (R10 = 2:0 μm, R20 = 1:6 μm)
Time evolution of pressure distribution on the side wall and isosurface of the void fraction α = 0:5 (R0 = 2:0 μm, two bubbles, long initial distance between bubbles)