Patent ID: 7722925

Claim:
A method of dispensing gas into a vacuum chamber, comprising the steps of: providing a vacuum chamber having a chamber wall that encloses a chamber interior; positioning a shelf within the chamber interior, wherein the shelf has an upward facing surface; providing a showerhead having a radially outer perimeter, a rim that includes said radially outer perimeter, an upper surface, a lower surface, and one or more gas orifices extending between the upper surface and the lower surface, wherein the rim of the showerhead includes a downward facing surface; positioning the showerhead within the chamber interior so that the downward facing surface of the rim of the showerhead rests on the upward facing surface of the shelf and so that the rim of the showerhead is free to slide along the upward facing surface of the shelf; and flowing gas through the gas orifices of the showerhead into the chamber interior.