Gas injection disc assembly for cvd applications

Abstract

A gas injection disc is provided which includes an outer ring and a tubular modular insert which slips into the outer ring. The outer ring is provided with an inner bore, a ring-shaped plenum located around the inner bore, an outer gas sealing surface around the plenum, and two gas feed paths extending from the periphery of the outer ring to the plenum. The gas feed paths are each provided with a gas feed attachment for coupling gas supply tubes thereto. The insert is provided with a plurality of radially aligned injectant holes, an inner gas sealing surface, and an axial bore. The insert is seated in the inner bore of the outer ring such that the inner and outer gas sealing surface face each other with a small gap provided therebetween which enables the insertion of the insert into the inner bore. The insert thereby substantially encloses the plenum, and the injectant holes are aligned with the plenum to receive injectant gases and direct the injectant gases into the axial bore of the insert. During the CVD process, the heat generated by the arc jet causes the insert to expand and eliminate the gap between the inner and outer sealing surfaces to thereby prevent undesirable gas leakage. Once the CVD operation is stopped the insert is permitted to cool and contract and return to its cooled dimensions unencumbered by the outer ring. The insert may then be removed for cleaning or for replacement with an insert having different characteristics.