APPARATUS FOR PREVENTING EXPANSION OF MASK

摘要

PURPOSE: An expansion preventing apparatus is to improve an overlay of a circuit pattern formed on a wafer by detecting amount of change in a temperature and size of a mask according to an exposing process and compensating an expansion rate. CONSTITUTION: An apparatus for preventing expansion of a mask comprises: a cooling tube(20) into which a cooling air is flown; a mask(21) formed in the cooling tube; a displacement detect pattern(22) formed at four corners of the mask; a displacement detection unit(24) for detecting a displacement value of the displacement detect pattern according to expansion of the mask; an expansion rate calculation unit(25) for calculating the expansion rate of the mask according to the displacement value; and a cooling air adjusting unit(26) for selectively adjusting amount of the cooling air according to the result of the expansion rate calculation unit and preventing expansion of the mask. The displacement detection unit further comprises a high resolution detector(23) for detecting a position change of the displacement detection pattern.