Patent ID: 7156721

Claim:
A polishing pad useful for chemical mechanical polishing a wafer, the polishing pad comprising: a. a polishing portion having a wafer track, a rotational axis and a plurality of grooves, each groove including: i. a first portion; and ii. a second portion positioned radially outward of the first portion in communication with the first portion at a transition location for increasing residence time of polishing medium in the second portion; and b. wherein the transition location of at least a first one of the plurality of grooves is spaced a first radial distance from the rotational axis and the transition location of at least a second one of the plurality of grooves is spaced a second radial distance from the rotational axis, the first radial distance being different than the second radial distance and the transition locations of the plurality of grooves are positioned within the wafer track to have a different residence time of polishing medium within the first one the plurality of grooves across the polishing portion.