Effect of Retaining Ring Slot Design on Slurry Film Thickness during CMP

Abstract

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.