Aspects of the present disclosure generally relate to oscillating a boundary layer of a flow of process gas in methods and systems for processing substrates. In one aspect, one or more of a pressure, a gas flow rate, and/or a height of a substrate are oscillated during processing. In one implementation, a method of processing a substrate includes conducting a processing operation on the substrate in an interior volume of a processing chamber. The conducting the processing operation on the substrate includes moving a flow of one or more process gases over a surface of the substrate. The method also includes oscillating a boundary layer of the flow of one or more process gases while the flow of one or more process gases moves over the surface of the substrate.