It is very difficult to remove extremely small particles from the surface of the wafer. Here, we proposed a new cleaning strategy using brush scrubbing, namely, nodule deformation induced fluid flow. Liquid absorption and desorption due to brush deformation enhance the mixing of liquids containing small particles. In this study, we developed a setup that reproduced the actual movement of PVA roller brushes on a rotating wafer and observed the contact surface of the brush nodule. We modeled the brush nodule deformation for each rotating condition. As a result, three types of nodule deformation were observed. In most cases, the nodule side face, rather than the bottom face was mainly in contact with the wafer surface. Moreover, we compared two types of roller brushes, normal cylindrical nodules, and edge treated nodules and found that the deformation can be significantly changed by chamfering nodule edge.

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Understanding the contact area distribution during brush scrubbing is important in order to better design the optimal shape of brushes. In this study, we visualized the contact area distribution of polyvinyl alcohol (PVA) brushes on a prism surface via the total reflection method. Brush deformation during scrubbing is also discussed in this study. Results show that the nodule side face, rather than the bottom face, mainly contacted the surface. In addition, we observed that the rotational speed range of stick-slip phenomena occurrence depended on the wettability of the prism.

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