ABSTRACT
This chapter addresses the importance to wafer processing for the calculations of particle deposition velocity and the supporting measurements carried out in carefully controlled laboratory deposition apparatus. In the absence of electrical or thermal forces, the dominant mechanisms of submicrometer particle deposition were shown to be gravitational settling and diffusion. These mechanisms are always present; airflow contributes a superimposing convective or turbulent transport mechanism that also affects deposition velocity. The addition of electrical or thermal forces (or both) further modifies predictions and results. The chapter discusses the significance of the modeling work in this environment. It reviews the specific control technology for minimizing electrical forces in clean rooms—room air ionization. Various electrical bias schemes that exist for creating bipolar ion clouds are: double direct current (dc) system, alternating current (ac) configuration, and pulsed dc operation. Finally, the chapter summarizes the studies of particle deposition on wafers dipped or immersed in liquids.
