A cluster tool is disclosed that can increase throughput of a wafer fabrication process by facilitating removal of barrier overhang in contact holes of contact film stacks. Individual chambers of the cluster tool provide for deposition of barrier material onto a semiconductor structure, depositing over with an amorphous carbon film (ACF), etching back the ACF, and etching a corner region of the contact hole. Removal of the barrier overhang improves the quality of metal fill-in of the contact hole. An expectedly ensuing feature entails a technique in which filling-in of the contact hole with a metal such as tungsten can be achieved with attenuated or eliminated adverse consequence.