An apparatus and method for performing a cyclical layer deposition process, such as atomic layer deposition is provided. In one aspect, the apparatus includes a substrate support having a substrate receiving surface, and a chamber lid comprising a tapered passageway extending from a central portion of the chamber lid and a bottom surface extending from the passageway to a peripheral portion of the chamber lid, the bottom surface shaped and sized to substantially cover the substrate receiving surface. The apparatus also includes one or more valves coupled to the gradually expanding channel, and one or more gas sources coupled to each valve.