Patent ID: 7922440

Claim:
An apparatus for positioning a substrate in a processing chamber, comprising: a substrate support having a support surface adapted to receive the substrate; and a plurality of centering members configured to center the substrate relative to a reference axis substantially perpendicular to the support surface, wherein the plurality of the centering members are movably disposed along a periphery of the support surface, each of the plurality of centering members is pivotally mounted on the substrate support via a shaft, and each of the plurality of centering members comprises: a first end portion configured to contact a periphery edge of the substrate, wherein the first end portion is movable between a first position and a second position, a movement from the first position to the second position causes the centering member to move out of contact with the peripheral edge of the substrate, and a movement from the second position to the first position causes the centering member to contact the periphery edge of the substrate; and a weighted portion having an embedded mass of solid material with high density, wherein the first end portion and weighted portion are disposed on opposing sides of the shaft, and the weighted portion is configured to bias the first end portion towards the first position by gravity.