ABSTRACT
A wide variety of substrate surfaces are cleaned in ultrasonic or megasonics cleaners, whereby ultrasound emanates into a ¯uid to generate cavitation. ¤e ¯uid will typically contain an aqueous solution, which includes additives such as surfactants and detergents that enhance the cleaning performance of the system. ¤e standard approach is to have a bath of the ¯uid with bottom-mounted or side-mounted transducers. Recently, more specialized means of delivery have been employed, most notably for single-wafer applications. One application has the megasonics diverted into a stream of ¯ uid that impacts the substrate surface. In another, megasonics imparts directly on a ©lm of ¯uid no more than a few millimeters thick on the wafer surface. Ultrasonics can also be delivered via an ultrasonic horn, which is a popular method not for cleaning, but for cell disruption, emulsi©cation, and homogenizing of biological matter. In both cleaning and cell disruption applications, it is the occurrence of cavitation that drives the actions.
