Patent ID: 7992877

Claim:
A chuck for releasably retaining a substrate, the chuck comprising: a body formed of a porous material having a substantially complete vitreous shell on all surfaces except for a substrate receiving surface, the substrate receiving surface disposed in an X-Y coordinate plane and adapted to receive the substrate, the substrate receiving surface having recessed annular channels with vitreous sidewalls disposed between discreet annular rings of the porous material, the recessed annular channels defining gas vacuum drawing portions and the discreet annular rings defining gas pressure delivery portions, the porous material of the body acting as gas pressure delivery channels, the body having gas vacuum drawing channels with vitreous sidewalls to isolate the gas vacuum drawing channels from the gas pressure delivery channels, where the gas pressure delivery channels and gas vacuum drawing channels are mutually exclusive within the body, the gas pressure delivery portions in communication with the gas pressure delivery channels, for delivering a gas pressure against the substrate while the substrate is retained by the chuck, and thereby keeping the substrate from contacting the substrate receiving surface, the gas vacuum drawing portions in communication with the gas vacuum drawing channels, for drawing a gas vacuum against the substrate while the substrate is retained by the chuck, and thereby retaining the substrate proximate the substrate receiving surface, and retaining means for retaining the substrate in X-Y directions from sliding off of the substrate receiving surface.