| 摘要 |
PROBLEM TO BE SOLVED: To directly detect a sucking-holding condition of a substrate on a holding stand, and prevent erroneous detection of substrate holding force by providing a detecting means to detect pressing force between the substrate and the holding stand. SOLUTION: Even if there is foreign matter in piping 4, since sucking-holding force is directly detected by a pressure sensitive sensor 14, a sensor signal is outputted, and after delay time taken for suction-hold passes, the sucking- holding force reaches a specified value, and a reticule 2 is safely moved. When the foreign matter in the piping 4 completely fills up the inside of the piping or a flow of air is stopped since the piping 4 is broken for any cause, the suction-hold is not completed, and is not put in a suction-hold completed condition. In this case, a movement of the reticule 2 is prohibited, and a damage accident is avoided. |
