Techniques herein include a process chamber for depositing thin films to backside surfaces of wafers to reduce wafer bowing and distortion. A substrate support provides an annular perimeter seal around the bottom and/or side of the wafer which allows the majority of the substrate backside to be exposed to a process environment. A supported wafer separates the chamber into lower and upper chambers that provide different process environments. The lower section of the processing chamber includes deposition hardware configured to apply and remove thin films. The upper section can remain a chemically inert environment, protecting the existing features on the top surface of the wafer. Multiple exhausts and differential pressures are used to prevent deposition gasses from accessing the working surface of a wafer.