Patent ID: 8187415

Claim:
A workpiece processing apparatus, comprising: a housing defining a process chamber a workpiece support configured to support a workpiece within the chamber during processing and comprising a plasma bias power electrode; a supply of pure oxygen gas; a supply of a polymerizing etch process gas; a circular ceiling plasma source power electrode comprising: (1) a center gas disperser at the center of said ceiling and coupled to said supply of pure oxygen gas for distributing the oxygen gas over the center of the workpiece support; (2) an inner annular gas disperser concentric with said center gas disperser and coupled to said supply of polymerizing etch process gas for distributing polymerizing etch process gas over an annular portion of the workpiece; (3) an outer annular gas disperser centered around the inner annular gas disperser and coupled to said supply of polymerizing etch process gas, for distributing the polymerizing etch process gas over an outer annulus of the workpiece; a bias power impedance match and an HF or LF bias power generator connected through said bias power impedance match to said workpiece support; and a VHF impedance match and a VHF plasma source power generator connected through said VHF impedance match to said ceiling electrode; a flow ratio controller connected between said supply of polymerizing etch process gas and said inner and outer annular gas dispersers for separately controlling respective flow rates of polymerizing etch process gases to said inner and outer annular gas dispersers; a flow rate control valve coupled to said center gas disperser and governing the flow rate of oxygen gas through said center gas disperser; a first diversion valve coupled between said supply of pure oxygen gas and said inner annular gas disperser for governing a flow rate of oxygen gas to said inner annular gas disperser; a second diversion valve coupled between said supply of pure oxygen gas and said outer annular gas disperser for governing a flow rate of oxygen gas to said outer annular gas disperser.