Novel Pad Conditioning and Slurry Dispense Methods in Chemical Mechanical Planarization

The first part of this study investigates the pad surface generated by conditioning with three different CVD-coated diamond discs and the corollary effect on polishing performance in copper CMP. The discs that were used had significantly different micro-structures with varying degrees of aggressiveness. Confocal microscopy was used to study the pad surface after the polishing experiments had been performed, where the contact area, contact density and surface topography were analyzed. The most aggressive disc generated a pad surface with the most contact area, contact density and the tallest asperities. These parameters decreased as the aggressiveness of the disc decreased. Thermal, tribological, and kinetic aspects of copper polishing were also investigated. The pad surface generated by the most aggressive disc produced the highest material removal rates. However, the pad surface generated by the least aggressive disc produced a slightly elevated coefficient of friction and mean pad temperature when compared to the other pad surfaces, most likely due to fluid suction caused by the glazed pad surface. Analysis of the chemical and mechanical rate constants indicated that this process was chemically limited for all P × V investigated. The second part of this study analyzed the thermal, tribological and kinetic aspects of the new and developing area of cobalt “buff step” CMP. A process-specific combination of consumables and polishing settings were used to investigate the removal of silicon dioxide in order to better characterize the second step of cobalt polishing in middle of the line (MOL) applications, where the overburden of deposited cobalt had already been polished away, and residual cobalt, along with the liner, needed to be completely removed. This was realized by polishing some of the surrounding dielectric in the “buff step”. Our study showed that the removal rate of the oxide and the mean pad temperature increased with increasing P × V, while the coefficient