Wafer Cleaning with PVA Roller Brushes

Abstract

PVA roller brushes are widely used for cleaning after the CMP process, one of the semiconductor manufacturing processes. The PVA roller brush features protrusions called nodules and rotates on the semiconductor wafer in cleaning. This article introduces a cleaning model that uses that PVA roller brush to remove nanoscale impurities. The evanescent fields on a prism enable us to observe the contact behavior of the brush nodules and clarify that there is little brush volume near the surface during sliding. We classified brush deformation into three types depending on the relative velocity of the wafer and nodule. A stamped contact occurs at a negative relative velocity, i.e., when the wafer overtakes the nodule, and this contact is related to cross-contamination from the brush. Finally, we present a model where water absorption and desorption associated with nodule volume deformation plays an important role in nanoscale impurities removal.