Dominant Forces for Driving Bubbles in a Wet Cleaning Bath Using Megasonic Wave

To evaluate the dominant forces for producing bubble motions in a wet cleaning bath for 300 mm diameter silicon wafers, the typical motions of small bubbles generated by the megasonic (MS) wave were studied using a video camera and an optical microscope. The bubbles with diameters of 10–30 and had upward velocities of 0.002–0.003 and 0.02–0.08 m/s, respectively, under the MS wave. The velocity of the diameter bubble depended on three forces, that is, the buoyancy, MS wave, and water flow. The motion of the diameter bubble was mainly driven by the MS wave; the influence of buoyancy was quite low. The path of the bubbles immediately above the wafer support bar could be changed by adjusting the MS wave power.