Evaluation of correlation between chemical modification state of pad and polishing rate in oxide chemical mechanical planarization

In the chemical-mechanical planarization of oxide films, the polishing rate (the rate of material removal) decreases if the polishing pad is not regularly conditioned. Pad brushing, which removed polishing debris but did not otherwise alter the pad surface, was unable to restore the original polishing rate. On the other hand, pad conditioning, in which the pad surface was scraped off, restored the original polishing rate. The morphological state and the chemical modification state of the pad surface were evaluated as factors affecting the polishing rate. FTIR (Fourier-Transform infrared spectroscopy) analysis showed that some of the polyurethane molecules of the pad surface were hydrolyzed. The degree of pad modification at each position in the pad radial direction was quantified based on the FTIR results, and the degree of pad modification was compared with the actual polishing profile within a wafer. The profile based on chemical modification of the pad matched the actual polishing profile. It was shown that not only the morphological factors of the pad but also the chemical modification factors greatly affected the polishing rate.