Resuspension of submicron Particles by Various Disturbances

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Resuspension of submicron particles from a duct wall by air stream was studied to clarify the detachment mechanisms of fine particles from various tubings and surfaces in clean room. Although the resuspension of particles in clean room leads to the contamination of products, the resuspension phenomena of particles by pulse air jet was investigated to develop dry wafer surface cleaning method. The followings are the main conclusions obtained in the present work.(1) Fine particles with diameter less than 1mum would not be resuspended by a steady air stream with velocity of over 100 m/s, but those which deposited at a bump of the wall or the aggregates of these particles could be detached from the surface at a lower airflow velocity.(2) Abrupt change in airflow velocity leads to particle reentrainment.(3) Sequence of pulse air jets is effective for the removal of fine particles from after surface because particle detachment takes place the moment air jet hits the surface.(4) Continual exposure of wafer surface to air jets brings complete removal of particles with diameter of 0.25mum.(5) Fraction of particles reentrained per pulse of air jet does not change in the sequence of the pulse air jets.(6) Particle removal efficiency from wafer surface by pulse air jets mostly depends on the air pressure rise at the collision of air jet on the surface.