| 摘要 |
A positioning apparatus includes a wafer chuck which retains a wafer and a hollow plate unit which retains the chuck, which is composed of a ceramic material in an integral, hollow structure having a hollow section, the hollow section having a rib structure which serves to increase the natural frequency of the hollow plate unit with respect to torsional mode vibration, and which has holes for providing connection between the interior and exterior of the hollow section. The rib structure is constructed such that a rib unit having a rectangular shape in cross section, the sides thereof extending along X and Y fine movement directions, and a rig unit having a diamond shape in cross section are alternately disposed inside each other and are bonded to each other.
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