MECHANISMS OF PARTICLE-TRANSPORT IN-PROCESS EQUIPMENT

Mechanisms affecting particle transport in wafer processing environments include: sedimentation, convective diffusion, thermophoresis, electrophoresis, and photophoresis. The first two mechanisms are universal; they exist everywhere and at all times. The latter three mechanisms, however, depend on conditions that can be introduced and used to minimize particle deposition on product wafers. This paper reviews theoretical models of all five mechanisms and describes procedures and hardware configurations that use one or more of the three controllable mechanisms to protect wafers from particulate contamination.