Importance

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Abstract

A method and apparatus for megasonic bath cleaning of wafers employs a megasonic resonator that is directed obliquely toward the front, active surface of the wafer, so that higher acoustic energy levels may be used without causing structural damage to the wafer. In one embodiment four transducers are coupled to a resonating plate, the four transducers being spaced apart to uniformly radiate separate portions of the wafer that total a 1/4 portion of the wafer surface. When the wafer is rotated, the wafer receives equal megasonic power across the entire surface. In a further embodiment, a resonating plate is driven by an acoustic transducer at an angle to the wafer and coupled to a refracting plate to result in an off-normal axis impingement angle. In another embodiment, a resonating plate is translated radially with respect to a wafer. The radiating surface of the plate may be rotated 0.degree.-10.degree. from normal to radiate obliquely to the wafer surface.

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First Claim