The Effect of Megasonic Input Power

EIGLfRE 16.31 Number of defects as a function of megasonic power (power level) at 65 °C after 8 min using SCI chemistry using a STEAG bench. 

Another factor that does not depend on power and is shared by DI water and SCI cleaning is the acoustic boundary layer thickness, which is a function of frequency and viscosity only. The boundary layer decreases from thousands of micrometers to a fraction of a micrometer when megasonics is applied at any power. The acoustic boundary layer thickness is inversely proportional to the frequency and directly proportional to the viscosity of the fluid. For example, a flow with a velocity of 4 m/s (maximum streaming velocity for the considered equipment) has a hydrodynamic boundary layer thickness of 1500 pm at the center of the wafer. By contrast, the acoustic boundary layer thickness on a wafer in a 850-kHz megasonic cleaning tank is 0.61 pm. The effect of a very 

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