Electro-chemical mechanical planarization and its evaluation on BEOL with 65nm node dimensions

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 evaluated on 65nm hardware. In the integrated Ecmp process, the bulk Cu is removed by electrochemical mechanical polishing at a high rate. The rate is controlled by applied charge and is independent of down force (0.3psi 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 removal-profile and an endpoint control across the wafer allows to tune the bulk Cu profile across the wafer. The Cu thickness profile produced by electro-chemical planarization allows the following conventional planarization step to clear remaining Cu with low dishing across the wafer and a careful selection of the barrier slurry allows further fine tuning to enhance overall Ecmp performance. The attributes of electropolish are analyzed. Electrical, defectivity and reliability data on 65nm node using Ecmp for Cu planarization are presented.