Effect of CMP conditioner diamond shape on pad topography and oxide wafer performances

Abstract

Chemical mechanical polishing (CMP) performance is often determined by the pad surface texture, which is mainly controlled by using a pad conditioner: usually, a diamond disk comprising numerous diamond grits attached to a flat metal substrate by means of brazing with an alloy. During the conditioning process, the diamonds interact with the pad surface to mainly remove the glazed layer and restore pad asperities. Selection of the appropriate diamond shape is crucial for obtaining the desired pad properties, conditioner life, and wafer removal rate. In this investigation, three different diamond shapes were carefully fabricated: (1) “sharp,” a sharp-edged diamond; (2) “blocky,” a high-quality crystalline diamond; and (3) “mixed,” a combination of sharp and blocky diamonds. Three new disks were fabricated using the above mentioned diamond shapes. Pad surface characterization was carried out to compare the new disks with conventional diamond disks, and the effect of the diamond shape on the wafer removal rate was studied. Oxide CMP tests revealed that the “mixed” diamond grit provided the highest wafer removal rate and the best uniformity. As compared to a conventional diamond disk, it also achieved a higher wafer removal rate and a better uniformity while consuming less pad material. On the other hand, if the dressing stability is the major concern, the use of “blocky” diamond grit is recommended because it provided the most stable wafer removal rate over a conditioning time of up to 20 h. However, if the dressing capability is the major concern, the use of “sharp” diamond grit is suggested because it provided the highest pad cut rate.