Integrated electro-chemical mechanical planarization (Ecmp) for future generation device technology

Abstract

A novel copper (Cu) planarization process, Ecmp, integrating electro-chemical mechanical polishing capability on a 300 mm CMP platform with low down force conventional polishing process is being developed and evaluated on low-k CVD devices. In the integrated Ecmp process, the bulk Cu is removed by electro-chemical mechanical polishing at a high rate which is controlled by applied charge and is independent of down force (O.3psi bulk Cu removal step). The Ecmp process removes topography efficiently and produces a thin planarized Cu film across all pattern densities with a uniform thickness profile across the wafer. A model based electro-chemical profile and endpoint control across the wafer allows one to tune the bulk Cu removal rate profile across the wafer to match that of the conventional Cu planarization step. The Cu thickness profile produced by electro-chemical planarization allows the conventional planarization process to clear remaining Cu with low dishing across the wafer. Therefore, an excessive dielectric removal for dishing correction is not required, making the process extendible to ultra-low k dielectrics that require a protective capping layer to be retained after polishing. Experiments are conducted to evaluate the planarization efficiency, film profile and endpoint control, cost of consumables, pattern density sensitivity and defect density. The mechanical and electrical results indicate that Ecmp enables the planarization of dual damascene structures with minimal dielectric erosion and defect density (<0.1 defects/cm2).