Impact of polisher kinematics and conditioner disc designs on fluid transport during chemical mechanical planarization

Fluid film thicknesses weremeasured and general flow patterns were analyzed during conditioning on a polishing pad using a recently developed UV-enhanced fluorescence experimental technique. The method was used to analyze how conditioners with different working face designs and polisher kinematics (platen angular velocities) affected fluid flow characteristics on the pad surface. In general, fluid film thicknesses followed the same general trends across the pad surface for both disc designs and platen speeds. Regardless of the parameters used, the fluid film was the thickest in sections nearest to the wafer track and was significantly thinner near the center and edge of the pad. For both discs, the time for film thicknesses to reach steady-state increased with distance from the radius. In general, the full-face conditioner had a smaller maximum attainable fluid thickness (MAFT) and time to reach steady-state (TTRSS) as it most effectively expelled (i.e. squeegeed) the fluid off the pad surface. In contrast, the partial-face conditioner had a larger MAFT and TTRSS as its more intricate design allowed for greater fluid retention and generated more back-flow.