| 摘要 |
The present invention discloses a lithographic apparatus a lithographic apparatus with an improved focus control system. The lithographic apparatus includes an illumination system (IL) configured to provide a beam of radiation (PB), a first support structure (MT) configured to support a patterning device (MA) that imparts the beam of radiation with a desired pattern in its cross-section, a second support structure (WT) that includes a substrate holder for holding a substrate (W), a projection system (PL) configured to project the patterned beam of radiation onto a target portion (C) on a surface of the substrate, and a servo unit (PW) configured to position the substrate holder. The apparatus further includes a sensor unit (LS) configured to determine a distance of at least one location point on the surface of the substrate relative to a reference plane (REF), a memory unit configured to store surface information of the substrate based on respective distances of corresponding the at least one location point on the substrate surface, and a calculating unit configured to determine a feed-forward set-point signal based on the stored surface information, such that the feed-forward set-point signal is forwardly fed to the servo unit in order to position the substrate holder. <IMAGE>
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