is pressed against the pad. The peaks of the polishing pad are pressed down and the pits are filled up, so the polishing pad surface becomes smoother and less abrasive. As a result, the polishing time increases. Therefore, the polishing pad surface must be periodically returned to an abrasive condition, or xe2x80x9cconditionedxe2x80x9d, to maintain a high throughput.
In addition, during the conditioning process, waste materials produced by conditioning the pad may fill or clog the perforations in the pad. Perforations clogged with such waste materials do not hold slurry effectively, thereby reducing the effectiveness of the polishing process.
An additional problem associated with filled or clogged pad perforations relates to the separation of the polishing pad from the substrate after polishing has been completed. The polishing process produces a highhaving a second plurality of substantially circular concentric grooves with a second width and a second pitch. At least one of the second width and second pitch differs from the first width and first pitch.
In another aspect, the polishing pad comprises a polishing surface having a first polishing region and a second polishing region surrounding the first polishing region, a spiral groove formed in the polishing surface, the spiral groove having a first pitch in the first polishing region and a second, different pitch in the second polishing region.
In another aspect, the polishing pad comprises a first polishing region having a first plurality of substantially circular concentric grooves, and a second polishing region surrounding the first polishing region and having a plurality of substantially serpentine grooves.
In another aspect,