Patent ID: 8043430
Filing Date: 2011-10-25
Classification: C23C,H01J,H01L

Abstract:
1. An apparatus for controlling gas flow conductance in a plasma processing chamber including an upper electrode disposed opposite a lower electrode adapted to support a substrate, the apparatus comprising: a stationary ground ring configured to concentrically surround the lower electrode, the ground ring including a first set of slots formed therein; a stationary cover ring including a second set of slots formed therein; a bypass choke ring disposed between the ground ring and the cover ring, the bypass choke ring including a third set of slots formed therein; and a mechanism adapted to rotate the bypass choke ring relative to the ground ring to vary an amount of overlap between the first and third sets of slots to thereby control gas flow conductance through the first, second, and third sets of slots between (i) an ON state in which the first set of slots is in fluid communication with the third set of slots such that gas can flow through the first, second and third sets of slots and (ii) an OFF state in which the first set of slots is blocked by the bypass choke ring such that gas cannot flow through the first, second and third sets of slots, the mechanism comprising an actuation rod and an actuation system coupled to the actuation rod and operative to move the actuation rod in an axial direction of the ground ring and, wherein: (a) the actuation system is a pneumatic cylinder or an electrical solenoid; (b) the actuation rod comprises a first end and a second end coupled to the actuation system and the mechanism further comprises a shaft rotatably secured to the ground ring and having a rotational axis substantially perpendicular to the axial direction of the ground ring, an elongated arm having one end secured to one end of the shaft and the other end coupled to the bypass choke ring, a lever having first and second ends and secured to the shaft intermediate the first and second ends thereof, a counterweight attached to the first end of the lever, and an actuation component attached to the second end of the lever and urged against the first end of the actuation rod by the counterweight, wherein the actuation rod, when moved by the actuation system in the axial direction of the ground ring, rocks the lever along the rotational axis of the shaft, causing the shaft and the elongated arm to rotate along the rotational axis of the shaft, thereby causing the bypass choke ring to rotate relative to the ground ring; (c) the actuation rod comprises a first end coupled to the actuation system and a tapered end portion opposite to the first end and the mechanism further comprises a lever comprising first and second end portions and pivoted to the ground ring intermediate the first and second end portions about an axis substantially parallel to the axial direction of the ground ring, the second end portion of the lever being in sliding contact with the tapered end portion of the actuation rod, an elongated arm having one end secured to the first end portion of the lever and the other end coupled to the bypass choke ring, and a first spring having two ends respectively secured to the ground ring and the lever and operative to resiliently urge the second end portion of the lever against the tapered end portion of the actuation rod, wherein the tapered end portion of the actuation rod, when moved by the actuation mechanism in the axial direction of the ground ring, rocks the lever causing the elongated arm to rotate, thereby causing the bypass choke ring to rotate relative to the ground ring; or (d) the mechanism further comprises an outer case secured to the ground ring and having walls that partially surround the tapered end portion of the actuation rod and a second spring interposed between one of the walls and a tip of the actuation rod and operative to urge the actuation rod toward the actuation system.