Nodule Deformation on Cleaning of PVA Roller Brushes and its Relation to Cross-contamination

This study investigates nodule deformation and contact area during PVA roller-type brush scrubbing to clarify their relationship with cross-contamination. Two high-speed video cameras with collimating LED light sources and an evanescent field on a prism enabled us to observe brush nodule deformation and contact area. Deformation analysis showed that the volume of a roller-type brush changes gradually at the beginning of compression, deforms more when vertically pushed at maximum compression, and then recovers rapidly at the end of compression. The brush contact area changes according to the brush and wafer rotation speed. The contact area can be categorized into three: the front, rear side face in the brush traveling direction, and vertically pushed bottom face on the surface. We analyzed the three types of brush contacts on a 100 mm type wafer and observed that the vertical compression type significantly affected the cross-contamination region.