Ultrasonic and Hydrodynamic Techniques for Particle Removal from Silicon Wafers

Ultrasonic and hydrodynamic cleaning techniques were used to remove particulate contaminants from bare silicon wafers and wafers with surface oxide layers. The variation of cleaning efficiency with particle size, composition and cleaning solvent was quantified. In comparison to submicrometer polystyrene and glass particles, silicon dust was found to be a particularly difficult contaminant to clean. The RCA standard cleaning solution (SC-1), which is a blend of 5 H₂O : 1 NH₄OH: 1 H₂O₂, when used in the ultrasonic or hydrodynamic cleaner, was less effective than DI-water in removing silicon particles, especially at low cleaning energies. Both types of cleaning systems resulted in particle removal efficiencies above 80% for submicrometer particles, the ultrasonic technique being more sensitive to particle and wafer surface composition.