GAS REACTION TRAJECTORY CONTROL THROUGH TUNABLE PLASMA DISSOCIATION FOR WAFER BY-PRODUCT DISTRIBUTION AND ETCH FEATURE PROFILE UNIFORMITY

Methods, systems, and computer programs are presented for controlling gas flow in a semiconductor manufacturing chamber. The method includes flowing a reactant gas thorough an inner feed and a tuning gas through an outer feed surrounding the inner feed, such that the gases do not mix until both are introduced in the chamber. Further, the flow of the reactant gas is convective, and the flow of the tuning gas is directed at an angle from the direction of the reactant gas, providing a delivery of the tuning gas in closer proximity to the RF power before further mixing with the reactant gas. Radio frequency power is provided to the electrode to ignite a plasma using the reactant and tuning gases. The diffusive flow of the tuning gas enables the tuning gas to be dissociated by the RF power allowing for control of the local residence time variation and preferential spatial dissociation patterns with respect to the local residence time of the reactant gas. The introduction of the gases into the chamber without pre-mixing imparts control of etch uniformity across the surface of the substrate during etching.