ABSTRACT
Particles from clean-room processing equipment or workers now play the dominant role in wafer contamination. The particles generated by any source within the clean room are continuously swept away by the airflow, typically designed to be a vertical laminar flow. Airflow modeling is the first step toward gaining further understanding of particle contamination problems. This chapter reviews the computational methods for airflow modeling in clean rooms and mechanisms of particle deposition on silicon wafers. The flow fields are calculated by solving the two-dimensional Navier-Stokes equations, and clean-room case studies are presented to help understand the role of the flow field. The chapter discusses the theoretical guidelines for describing clean-room airflows. Finally, it discusses the deposition of particles on silicon wafers under idealized flow conditions and the effect of electrostatic forces and thermal gradients on particle deposition.
