Apparatus and method for selectivity restricting process fluid flow in semiconductor processing

A semiconductor processing apparatus (10) is disclosed which includes a process chamber (12) and at least one substrate support (18) disposed within the process chamber (12) operable to support a substrate wafer (20). The semiconductor processing apparatus includes at least one showerhead assembly (14) disposed within the process chamber (12) facing the substrate support (18) and has a showerhead plate (16). The showerhead plate (16) has a plurality of passageways (17) extending therethrough for directing process fluid toward a substrate wafer (20) disposed on the substrate support (18). A blocking assembly (21) is disposed within the process chamber (12), the blocking assembly has an active position (32) between the showerhead assembly (14) and the substrate support (18) to restrict the flow of process fluid between the showerhead assembly (14) and the substrate support (18). The blocking assembly also has a neutral position (30) that does not restrict the flow of process fluid between the showerhead assembly (14) and the substrate support (18).