The present inventors have conceived of a showerhead inlet with an annular plenum and radial flow paths into a central passage. A process gas, that may include a precursor and a carrier gas, may be flowed into the annular plenum. The annular plenum and central passage may contribute to the uniform mixing of the precursor and the carrier gas. Additionally, the radial passage may be angled upward to help more effectively purge any dead legs within the central passage. The central passage may also interface with a remote plasma source valve. The remote plasma source valve may control the flow of reactive species generated by a remote plasma source into the central passage.