| Chemical Mechanical Polishing (CMP) involves rubbing a workpiece against a soft pad in the presence of a chemically active, abrasive containing slurry. CMP is vital in integrated circuit fabrication which requires smooth ;Negative vertical wafer displacements ;The mechanism for the interfacial contact can be described as follows. The sliding wafer causes a nonsymmetrical compressive stress distribution along the pad surface. High leading edge stress causes collapse of pad asperities expelling slurry residing in interasperity voids. Lower stress beneath the wafer allows asperity elastic re-bound and re-formation of interasperity voids leading to the suction force. Poiseuille in-flow through interconnected voids defines the magnitude of negative pressures. Numerical simulations from this model predict a suction force and negative vertical wafer displacement. |
