Effect of retaining ring slot design on slurry film thickness during CMP

This article studied the effect of retaining ring slot designs on the slurry film thickness within the pad-wafer interface during chemical mechanical planarization (CMP). Two retaining rings, with "standard" and "alternative" slot designs, were tested. Slurry film thickness within the pad-wafer interface was measured during polishing using dual emission UV-enhanced fluorescence. Results showed that slurry flow rate, pressure, and pad-wafer rotational rate had impacts on the slurry film thickness. Under the same polishing condition, the ring with the "alternative" slot design generated, on average, 30% thicker slurry film compared with the ring with the "standard" slot design.