Patent ID: 8522715

Claim:
An apparatus for controlling gas flow conductance in a plasma processing chamber, the plasma processing chamber configured with an upper electrode disposed opposite a lower electrode adapted to support a substrate, the apparatus comprising: a ground ring configured to concentrically surround said lower electrode, said ground ring including a first set of radial slots formed therein; a confinement ring arrangement, said confinement ring arrangement including at least a first set of collapsible confinement rings and a second set of collapsible confinement rings, wherein a first ring of said first set of collapsible confinement rings includes a first chamber having disposed therein a first piston and a first ring of said second set of collapsible confinement rings includes a second chamber having disposed therein a second piston, said second set of collapsible confinement rings is configured to movably couple to said first set of collapsible confinement rings; and a mechanism configured at least to collapse and to expand said first set of collapsible confinement rings and said second set of collapsible confinement rings to control gas flow conductance through said first set of radial slots between (a) an ON state in which a gas flow through said first set of radial slots is unobstructed by said second set of collapsible confinement rings, and (b) an OFF state in which said gas flow through said first set of radial slots is obstructed by said second set of collapsible rings.