Patent ID: 8100147

Claim:
A processing apparatus comprising: a processing chamber configured to be evacuated; a mount table disposed in the processing chamber and configured to place thereon a target object; an exhaust system configured to exhaust gas from inside the processing chamber; a showerhead disposed on the processing chamber and configured to introduce a gas into the processing chamber, the showerhead having a gas inlet port formed on its upper side; and a gas mixer attached to the upper side of the showerhead and configured to mix first and second gases to form a gas mixture and supply the gas mixture into the showerhead, the gas mixer having a gas outlet port formed on its lower side and connected to the gas inlet port of the showerhead, wherein the gas mixer includes a casing having a top plate, securing members attaching the casing to the showerhead, and a plurality of inner plates overlaid with each other and fitted inside the casing, the top plate and the inner plates include first and second gas introducing holes both extending downward from an upper surface of the top plate at positions shifted from its center and configured to respectively introduce the first and second gases, the top plate and the inner plates form a first interface between an upper pair of plates and a second interface between a lower pair of plates below the first interface, the first interface includes an upper central space present at its central position and an upper flow path connecting the first gas introducing hole to the upper central space, the upper central space and the upper flow path being respectively defined by a recessed portion and a recessed groove formed in at least one of the upper pair of plates, the second interface includes a lower central space present at its central position and a lower flow path connecting the second gas introducing hole to the lower central space, the lower central space and the lower flow path being respectively defined by a recessed portion and a recessed groove formed in at least one of the lower pair of plates, and the upper central space communicates with the lower central space through an upper central communication channel extending through corresponding parts of the inner plates, and the lower central space communicates with the gas outlet port through a lower central communication channel extending through corresponding parts of the inner plates, so as for the first and second gases to interflow in the lower central space and further to flow through the lower central communication channel to the gas outlet port.