Method and system for improving deposition uniformity in a vapor deposition system

A processing system for treating a substrate includes a process chamber, a substrate holder, a gas distribution system, and a flow modulation element. The process chamber has a pumping system to evacuate the process chamber. The substrate holder is coupled to the process chamber and supports the substrate. The gas distribution system is coupled to the process chamber. The gas distribution system introduces a process gas to a process space above an upper surface of the substrate. The flow modulation element is coupled to the substrate holder beyond a peripheral edge of the substrate. The flow modulation element includes one or more gas distribution openings that introduce an additive process gas beyond the peripheral edge of the substrate in a direction substantially away from the substrate. The additive process gas has a directional component substantially parallel to the upper surface of the substrate.