Patent ID: 8500182

Claim:
An apparatus for supporting a wafer, the apparatus comprising: a base; a gas-penetration layer of a circular shape, wherein the gas-penetration layer and a portion of the base directly underlying the gas-penetration layer form a gas passage therebetween, and wherein the gas passage is configured to be sealed by the wafer placed directly over the gas-penetration layer, and a diameter of the gas-penetration layer is slightly smaller than a diameter of the wafer placed on the gas-penetration layer; a rim portion of the base encircling the gas-penetration layer, wherein the rim portion has a top end higher than a top surface of the gas-penetration layer, the rim portion is configured such that a wafer, when placed on the rim portion, is in contact with and supported solely by an inner edge of the rim portion; and a valve connected to the gas passage.