An assembly for use in a process chamber for depositing a film on a wafer. The assembly includes a pedestal having a pedestal top surface extending from a central axis of the pedestal to an outer edge, the pedestal top surface having a plurality of wafer supports for supporting a wafer. A pedestal step having a step surface extending from a step inner diameter towards the outer edge of the pedestal. A focus ring rests on the step surface and having a mesa extending from an outer diameter of the focus ring to a mesa inner diameter. A shelf steps downwards from a mesa surface at the mesa inner diameter, and extends between the mesa inner diameter and an inner diameter of the focus ring. The shelf is configured to support at least a portion of a wafer bottom surface of the wafer at a process temperature.