Rotary friction welded blank for PECVD heated showerhead
A deposition apparatus for processing substrates includes a vacuum chamber including a processing zone in which a substrate may be processed. A showerhead assembly includes a stem, face plate and back plate wherein the stem is rotary friction welded to the back plate. A substrate pedestal assembly is configured to support a substrate on an upper surface thereof when a substrate is processed in the deposition apparatus.
1. A method of manufacturing a component of a showerhead assembly useful for depositing material on an upper surface of a substrate in a plasma enhanced chemical vapor deposition apparatus, the method comprising:
cutting a length of extruded solid aluminum bar to provide a stem precursor blank;
cutting a piece of rolled aluminum plate stock to provide a back plate precursor blank;
forming a welded blank by rotary friction welding the stem precursor blank to the back plate precursor blank such that a welded joint is formed across the stem precursor blank and intermetallic phases in the weld joint are elongated in a radially outward direction;
forming a showerhead component blank having an integral stem and back plate by machining the welded blank to remove welding flash.
2. The method of claim 1 , further comprising machining the back plate precursor blank to include a raised hub on one side thereof, machining the stem precursor blank to have an axial end perpendicular to a center axis of the stem precursor blank, clamping the back plate precursor blank with the raised hub exposed, rotating the stem precursor blank while pressing the axial end of the stem precursor blank against the raised hub so as to form a fusion weld joint between opposed surfaces of the stem precursor blank and the back plate precursor blank.
3. The method of claim 1 , further comprising machining the welded blank to final desired dimensions of a back plate and stem of a showerhead assembly and welding an outer periphery of the back plate to an outer wall of a face plate such that an inner plenum is formed between the back plate and the face plate.
4. The method of claim 3 , wherein at least one vertically extending gas passage is machined in the stem and back plate such that the gas passage is in fluid communication with the inner plenum.
5. The method of claim 3 , further comprising inserting posts extending from an inner surface of the face plate into holes in the back plate and welding upper ends of posts to the back plate.
6. The method of claim 1 , wherein the back plate precursor blank and the stem precursor blank are made of an aluminum alloy having the same composition.
7. The method of claim 1 , wherein the rotary friction welding is carried out with an axial pressure of at least 3000 psi while rotating the stem precursor blank at a rotational speed of at least 300 rpm.
8. The method of claim 1 , wherein the weld area is at least 30 square inches.
9. The method of claim 1 , wherein grain size of the weld zone is elongated in a radially outward direction with intermetallic phases distributed in the grain structure.
10. The method of claim 1 , wherein the weld joint is free of voids and cracking.
11. The method of claim 1 , wherein the back plate precursor blank has a diameter of at least 12 inches and a thickness of at least 1 inch, and the stem precursor blank has a diameter of at least 2 inches and a length of at least 6 inches.