The role of neutral drag force in pulsed plasma enabled particle contamination control

Driven by the continuous decrease of the length scales of fabricated semiconductor structures, ultraclean semiconductor processing equipment suffers more and more from contamination with nano- and micrometer sized particles, which may be introduced in such systems from the outside via gas flows either externally injected or through translational and/or rotational (robotic) feedthroughs. One promising approach to filter contaminating particulates from these gas flows is the application of a plasma particle seal in which airborne particles carried by a gas flow pick up free charges from a plasma and then are deflected by an externally applied electric field in the plasma’s afterglow region. Consecutively, these contaminating particles may be guided to less harmful locations in the system or even be fully removed. In this contribution, we present measurements that reveal the importance of additional drag forces imposed on the particles and the influence of these drag forces on the particles’ trajectories when the plasma is operated in pulsed mode.