Patent ID: 7411384

Claim:
A wafer chuck comprising: a plurality of pins, each of which protrudes and retreats via a through hole formed in a vertical direction in a mounting table, each of the pins including at a top end thereof a receiving surface part which virtually makes no gap between each of the pins and the through hole; a joint member for supporting the pins; an ascending/descending mechanism for ascending and descending the joint member to thereby protrude and retreat the pins, the wafer chuck being configured to receive or deliver a wafer by protruding the pins above a mounting surface of the mounting table; and a mechanism for aligning the receiving surface part of each of the pins to be flush with the mounting surface, wherein the mechanism includes a supported surface part formed below the receiving surface part of each of the pins, a supporting part formed in the through hole to be contacted with the supported surface part, and a pressing arrangement for making the supported surface part constantly contact the supporting part, and wherein the pressing arrangement includes a first pressing mechanism for biasing the joint member, and a second pressing mechanism provided at each of the pins for biasing each of the pins.