| 摘要 |
A semiconductor wafer positioner including a rotating table on which a wafer is placed and a peripheral shape of the wafer is optically detected as a first peripheral shape signal. A control section combines two half cycle components of the first peripheral shape signal, the components being 180 DEG out of phase, to obtain a second peripheral shape signal exhibiting a characteristic feature of flat orientation. A peak in the second peripheral shape signal is detected, and data in the first peripheral shape signal corresponding to the peak and 180 DEG from the peak is invalidated. A curve approximation is utilized to approximate the invalidated data to produce a third peripheral shape signal from which an eccentricity amount and direction are calculated.
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