MECHANISMS OF PARTICLE-TRANSPORT IN-PROCESS EQUIPMENT

Mechanisms affecting particle transport in wafer processing environmen ts include: sedimentation, convective diffusion, thermophoresis, elect rophoresis, 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 minim ize particle deposition on product wafers. This paper reviews theoreti cal models of all five mechanisms and describes procedures and hardwar e configurations that use one or more of the three controllable mechan isms to protect wafers from particulate contamination.