Fundamental characterization of diamond disc, pad, and retaining ring wear in chemical mechanical planarization processes

Diamond discs, pads, and retaining rings are critical consumables subjected to wear in chemical mechanical planarization (CMP) processes. In this work, methods that are used to characterize diamond disc, pad, and retaining ring wear are introduced and examples are reviewed to illustrate some of the wear mechanisms to which consumables are subjected. For diamond disc characterization, a proprietary method is used to locate the active diamonds that actually make contacts with the pad and create cutting furrows during conditioning. Scanning electron microscopy indicates that wear normally occurs on the cutting edges of the active diamonds. For pad macro wear, an example is shown to illustrate that an optimized conditioning sweep schedule can generate a much more uniform pad cut rate profile. For pad surface micro wear characterization, interferometry analysis is used to establish pad surface height probability density functions and extract pad surface abruptness, and confocal microscopy analysis is used to analyze pad surface contact area. Interferometry analysis is also used to characterize retaining ring wear, which not only allows retaining rings to be subjected to significantly shorter than usual wear time, but also provides more accurate estimate of local wear rates than conventional micrometry or weight loss measurements.