Influence of process parameters on chemical-mechanical polishing of copper

A systematic study of Cu CMP concerning the influence of process parameters such as polishing pressure (between 10.9 and 32.8 kPa) and relative velocity between wafer and pad (between 24.3 and 105.5 cm/s) on the planarization behavior of the CMP process and also Cu dishing and SiO2 thinning has been performed. A geometry-independent parameter like the planarization rate was defined and used to describe the global-scale planarization ability of the process. Within the investigated range, the polishing pressure has no impact on the planarization rate. On the contrary, polishing at lower velocities has to be avoided, because it would lead to a slower planarization process. For the consumables used (IC 1000/SUBA IV as a polishing pad and QCTT 1010 as a slurry), both the polishing pressure and the relative velocity between wafer and pad do not influence Cu dishing and SiO2 thinning at the nominal endpoint of the process and also during overpolishing. As a consequence, a wide-margin process was established.