Mechanisms of Post-CMP Cleaning

Abstract

We investigate the post-CMP cleaning process with a tribological approach. A cleaning process involves three components: brush, wafer/disk, fluid undergoing three-body sliding contact between the brush, wafer, and particles from slurry. Having this in mind, we investigated cleaning mechanisms through experimental measurement of friction force and analyzed the contact condition for particle removal. Our investigation leads to the conclusions that the cleaning process is a boundary to elastohydrodynamic lubricating process that involves a constant contact between a brush and the wafer or disk surface. The motion of the brush nodule is such that the surface forces between the brush and workpiece change from an initial adhesion to sliding abrasion. These analysis leads to insight of particle removal mechanisms.

Evaluation of friction characteristics between PVA sponge and solid materials using surface free energy measurements

“…For example, H. Liang et al investigated the relationship between the particle removal by a PVA brush and frictional force and found that the CMP cleaning process was characterized by both boundary lubrication and the elastohydrodynamic lubrication phenomena caused by the constant contact between the PVA brush and the cleaning target. 1) However, even though friction is explained by the interactions between the contacting interfaces and viscoelastic properties, it is difficult to evaluate those interactions quantitatively. For example, Y.…”