A method of processing a semiconductor wafer is provided. The method includes installing upper lid. The installation of the upper lid includes placing an inlet manifold on a water box; inserting a jig into a lower gas channel in the water box and inserting into an upper gas channel in the inlet manifold; fastening the water box to the inlet manifold; and removing the jig after the water box engaging with the inlet manifold. The method also includes connecting a shower head on a lower side of the water box; and connecting the upper lid to a housing. The method further includes placing a semiconductor wafer into the housing. In addition, the method includes supplying a process gas over the semiconductor wafer through the upper gas channel, the lower gas channel and the shower head.