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May 12, 2015 - Onda is pleased to support the cavitation measurement research at University of Arizona which was presented at the SEMATECH SPCC meeting in Albany, NY.
Professor Manish Keswani from the Materials Science Department presented:
Characterization of Acoustic Cavitation in Surfactant Containing Aqueous Solutions using Hydrophone and Fluorescence Spectroscopy Techniques
Megasonic cleaning is a commonly used method in integrated circuit industry for surface cleaning and preparation. Although effective particle removal can be achieved at higher power densities, it also results in feature damage. Both stable and transient cavitation and streaming contribute to cleaning whereas the damage is mainly caused by transient cavitation. Stable cavitation arises by oscillation of bubbles and generates microstreaming. By contrast, transient cavitation is the growth and eventual collapse of bubbles that generates extremely high temperatures and pressures and forms shock waves and microjets that damage the surface. The relative extent of stable and transient cavitation is controlled by tuning of various sound field and solution variables including transducer operating frequency and power density, dissolved gases, solution temperature, and use of additives such as surfactants. The benefit of using surfactants is that they improve the wettability of the surface and also prevent re-deposition of contaminant particles, which assist in achieving higher cleaning efficiency. Further, surfactants can also adsorb on the bubble-liquid interface and in turn affect cavitation. In the current work, we have used acoustic emission (hydrophone) and fluorescence spectroscopy techniques to characterize stable and transient cavitation and hydroxyl (OH) generated in solutions containing a non-ionic surfactant such as Triton X-100 and irradiated with 1 MHz sound field at two different power densities. The choice of this surfactant for this study was based on its wide use by semiconductor industry for cleaning applications.