Effect of CVD-Coated Diamond Discs on Pad Surface Micro-Texture and Polish Performance in Copper CMP

Abstract

The effect of pad surface characteristics on the thermal, tribological and kinetic attributes of copper CMP was investigated. Three CMC D100 pads with very different surface micro-textures were generated using three very different CVD-coated diamond conditioning discs. Pad samples were collected after polishing and analyzed for their surface contact area and topography using confocal microscopy. The contact area, contact density, and asperity height increased with increasing conditioner aggressiveness. Copper removal rates and pad surface temperatures increased with increasing polishing pressure and sliding velocity for all pads albeit in a non-Prestonian manner. The pad generated by the most aggressive disc caused the highest removal rates yet it showed the lowest overall coefficient of friction (COF). The tall asperities, open pores, and adequate contact of this pad produced a greater removal rate than pad surfaces with shorter asperities and glazed pores produced by the less aggressive discs. Trends in COF, temperature and removal rate were successfully simulated using a two-step modified Langmuir-Hinshelwood model which also yielded values for the chemical and mechanical rate constants. The simulation results indicated that the process was chemically limited for all polishing conditions, and that the process became even more chemically limited as P × v increased.