| 摘要 |
PROBLEM TO BE SOLVED: To provide an overlap measuring apparatus, which improves the through put by measuring and adjusting the accuracy of an optical system with a prescribed timing before the measuring errors exceed a specified level. SOLUTION: Accuracy reference marks 23a and 23b are arranged on a Z stage 22Z which carries a wafer 21. An upper side overlap mark 20U is formed on a lower side overlap mark 20L of the wafer 21. Positional deviation between the upper and lower side overlap marks is measured, and the wafer with the resulting value exceeding a specified value is rejected as being defective. The accuracy of the optical system is measured periodically, utilizing the accuracy reference marks 23a and 23b on the Z stage 22Z to adjust an abberation, lighting telecentric, eclipse and the like. This can further improve the throughput, as compared with the case of accuracy detection of the optical system to counter a higher ratio of defectives.
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