Recent experimental advances using dual emission laser induced fluorescence and image processing have provided high spatial and temporal resolution maps of the slurry layer during chemical mechanical polishing (CMP). Intensity differences in the images correspond to fluid layer thickness variations as the slurry passes between different pad and wafer topographies. Asperities expand under 14 mu m deep wells and are compressed beyond the trailing edge of the wells. Air pockets travel from the leading to the trailing edge of the wafer through 27 mu m deep wells. The pads tested were Freudenberg FX9, Rodel IC1000, and experimental pads from Cabot Microelectronics. (C) 2005 The Electrochemical Society.