| 摘要 |
A table holding a substrate thereon is placed on a focusing and levelling stage through three fulcrums, and a calculator receives as inputs the coordinates values of the table measured by an interferometer, the amount of positional deviation between the surface of a wafer and a predetermined fiducial plane at each of a plurality of measuring points on the substrate which is measured by a multipoint AF sensor, and a weight coefficient given to be to the amount of positional deviation at each of the plurality of measuring points, thereby calculating the residual deviation at each of the three fulcrums. A controller adopts the PID control system and controls the amounts of displacement of the three fulcrums on the basis of the residual deviation calculated by the calculator, the integrated value of this residual deviation and the differentiated value of this residual deviation.
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