Device for supporting a wafer

A device for supporting a wafer, comprising:

• a base plate;
• a group of first supports circumferentially arranged at regular intervals on said plate to support a periphery of the wafer above said plate, and a group of second supports circumferentially arranged on said plate, in spaced relation to each of the first supports, to support the periphery of the wafer above said plate, each of the first and second supports being movable between a supporting position for supporting the wafer and a releasing position, radially outward of said supporting position, in which the support is released from the wafer;
• releasing means urging each of said first and second supports radially outwardly toward said releasing position;
• and
• means for alternatively
• (1) moving each of said first supports into said supporting position while simultaneously allowing said releasing means to urge each of said second supports into said releasing position or
• (2) moving each of said second supports into said supporting position while simultaneously allowing said releasing means to urge each of said first supports into said releasing position, said alternatively moving means including an annular member rotatably mounted on said base plate, said annular member having a plurality of internal projections circumferentially arranged along an inside surface of said annular member in correspondence with said first and second supports.