Abstract: A method and apparatus for selecting an optimum frequency for driving a transducer in a megasonic cleaning system. The method comprises the steps of selecting a plurality of frequency values that span a frequency range containing an optimum frequency for driving a piezoelectric crystal, determining the reflection coefficient at each frequency value, fitting the data set to a function, obtaining the first derivative equation of the function, finding the roots of the first derivative equation to yield a set of roots, and selecting the optimum frequency from the set of roots. The reflection coefficient is defined as the reflected power divided by the forward power. The apparatus comprises a microprocessor, a frequency generator, a directional coupler/detector and an analog to digital converter circuit.

Abstract: A megasonic cleaning system comprised of a container, a resonator, one or more piezoelectric crystals and a bonding layer comprised of indium or tin for attaching the piezoelectric crystal to the resonator. The resonator comprises a material selected from the group consisting of quartz, sapphire, silicon carbide, silicon nitride, aluminum, ceramics and stainless steel. The piezoelectric crystal may be attached directly to a side or to the bottom of the container, in which case the container acts as the resonator.

Abstract: A transducer comprised of a resonator and a piezoelectric crystal for cleaning single items such as semiconductor wafers and flat panel displays. The resonator is an elongated piece of material having a cross section that is trapezoidal in shape. The parallel sides of the trapezoid form the top and bottom ends of the resonator and the nonparallel sides of the trapezoid focus the acoustic energy on the bottom end of the resonator.

Abstract: A system for making electrical connections to a piezoelectric crystal in a megasonic transducer. The system comprises a printed circuit board, one or more first spring connectors and one or more second spring connectors. The printed circuit board has a first copper trace plated on it that is adapted for electrical connection to the active terminal of an RF generator. A second copper trace is plated on the printed circuit board and is adapted for electrical connection to the ground terminal of the RF generator. The first spring connectors are electrically connected to the first trace and are positioned to make electrical contact with the back side of the piezoelectric crystal. The second spring connectors are electrically connected to the second trace and are positioned to make electrical contact with the front side of the piezoelectric crystal, so that the piezoelectric crystal is exited when the RF generator is in operation.

Abstract: A megasonic cleaning system comprised of a container, a resonator, a piezoelectric crystal and an indium layer for attaching the resonator to the piezoelectric crystal. The container includes a fluid chamber for holding a volume of cleaning solution. The resonator is selected from the group consisting of sapphire, quartz, silicon carbide, silicon nitride and ceramic. The resonator forms the bottom of the container and has an interface surface which abuts the fluid chamber.

Abstract: A megasonic transducer comprised of a stainless steel plate attached to a piezoelectric crystal by an indium attachment layer. To facilitate the attachment, a chromium layer and a silver layer are positioned between the stainless steel plate and the indium layer. Similarly, silver and chromium layers are positioned between the indium layer and the piezoelectric crystal.