Investigation of a Novel Diamond Disk's Effect on Pad Topography in Oxide Chemical Mechanical Polishing

Polishing pads become glazed due to the accumulation of debris during chemical mechanical polishing (CMP) processes. Hence, the wafer removal rate is reduced. A pad conditioner or diamond disk must be frequently employed to restore the pad surface texture. Traditional diamond disks are prepared by adhering similar types of diamond grit to a flat substrate. In these cases, the diamond tips have different heights due to difficulties in controlling the levels of such large amounts of diamond grit. In this study, a new combined diamond disk is designed and manufactured to significantly improve the leveling of diamond tips, thereby reducing the amount of diamond grit. The proposed combined diamond disk incorporates two types of diamond grit (blocky and sharp) distributed across the entire disk surface. Such a combined diamond disk enables the manufacturer to tightly control diamond leveling and, moreover, reduces the number of diamond pieces by more than a factor of two. Experimental results reveal that that the removal rate correlates well with variations in force. The combined diamond disk provides a higher polishing rate and better uniformity while consuming less pad material. The pad lifetime is expected to be prolonged, and this consequently lowers the operational costs of the CMP process.