Visualization of the contact area between PVA brush and a surface using total reflection light

Abstract

Scrub cleaning with PVA brushes is widely used in the post CMP cleaning process for semiconductor device manufacturing. PVA brushes are hydrophilic porous sponges, and the PVA brush scrubbing is a complex system in which a gas-liquid-solid interface exists. To elucidate the lubrication condition between a PVA brush and contacting surface, we observed the real contact area of the brush using a total reflection optical device. We investigated the real contact area of the brush by applying a normal load and sliding with various speeds. As a result, the real contact area increased with the increase of brush compression, however the increase was non-linear. It was also confirmed that contact points concentrated in the front part for moving direction and detached in the rear part on surfaces. Additionally, stick-slip motion was observed under low rotating speed by observing the contact surface of PVA roller brushes.