MASK HOLDING BACKUP MECHANISM FOR EXPOSURE SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a mask holding backup mechanism for an exposure system which can prevent mask fall preventive means from interfering with a work of a size larger than the size of the mask even if the work is brought into proximity to the mask and can surely prevent the fall of the mask even if the attractive holding force of the mask to a mask holder is lost. SOLUTION: The mask holder 101 is provided with at least one set of the mask fall preventive means 103 in its positions facing each other via the mask 102. The mask fall preventive means 103 consist of mask bearing bodies 104 which have mask receiving parts 104a corresponding to engaging parts 102 a at the outer peripheral edges of the mask 102 at their front ends and are so disposed that their under surfaces do not exist below the lowermost surface of the mask 102 and drive mechanisms 105 which drive these mask bearing bodies 104 in such a manner that the mask receiving parts 104a attach and detach to and from the engaging parts 102a.