Techniques are disclosed for methods and apparatuses for delivering process gas for processing a substrate. In one embodiment, the method begins by injecting process gas into a processing chamber proximate an edge of a substrate disposed in the processing chamber from a first location. The method then continues by way of injecting the process gas into the processing chamber proximate the edge of the substrate disposed in the processing chamber from a second location while no gas is injected from the first location. Finally, the method finishes by way of processing the substrate in the presence of the processing gas injected from the first and second location.