Lithographic apparatus and device manufacturing method with feed-forward focus control
First Claim
1. A lithographic apparatus, comprising:
- an illumination system configured to provide a beam of radiation;
a first support structure configured to support a patterning device that imparts said beam of radiation with a desired pattern in its cross-section;
a second support structure that includes a substrate holder for holding a substrate;
a projection system configured to project said patterned beam of radiation onto a target portion on a surface of said substrate;
a servo unit configured to position said substrate holder;
a sensor unit configured to determine a distance of at least one location point on the surface of said substrate relative to a reference plane;
a memory unit configured to store surface information of said substrate based on respective distances of corresponding said at least one location point on said substrate surface; and
a calculating unit configured to determine a feed-forward set-point signal based on said stored surface information, wherein said feed-forward set-point signal is forwardly fed to said servo unit in order to position said substrate holder.
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Abstract
The present invention discloses a lithographic apparatus a lithographic apparatus with an improved focus control system. The lithographic apparatus includes an illumination system configured to provide a beam of radiation, a first support structure configured to support a patterning device that imparts the beam of radiation with a desired pattern in its cross-section, a second support structure that includes a substrate holder for holding a substrate, a projection system configured to project the patterned beam of radiation onto a target portion on a surface of the substrate, and a servo unit configured to position the substrate holder. The apparatus further includes a sensor unit configured to determine a distance of at least one location point on the surface of the substrate relative to a reference plane, 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.
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Citations
19 Claims
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1. A lithographic apparatus, comprising:
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an illumination system configured to provide a beam of radiation;
a first support structure configured to support a patterning device that imparts said beam of radiation with a desired pattern in its cross-section;
a second support structure that includes a substrate holder for holding a substrate;
a projection system configured to project said patterned beam of radiation onto a target portion on a surface of said substrate;
a servo unit configured to position said substrate holder;
a sensor unit configured to determine a distance of at least one location point on the surface of said substrate relative to a reference plane;
a memory unit configured to store surface information of said substrate based on respective distances of corresponding said at least one location point on said substrate surface; and
a calculating unit configured to determine a feed-forward set-point signal based on said stored surface information, wherein said feed-forward set-point signal is forwardly fed to said servo unit in order to position said substrate holder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A device manufacturing method, comprising:
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providing a substrate on a supporting surface of a substrate holder;
providing a beam of radiation using an illumination system;
imparting said beam of radiation with a desired pattern in its cross-section, said desired pattern provided by a patterning device;
projecting said pattern beam of radiation onto a surface of said substrate via a projection system;
determining a distance of at least one location point on said substrate surface relative to a reference plane, said reference plane being in a fixed position relative to said projection system;
storing surface information of said substrate based on respective distances of corresponding said at least one location point on said substrate surface;
calculating a set-point signal based on said stored surface information;
forwarding said set-point signal to a servo unit configured to position said substrate holder; and
positioning said substrate holder relative to said projection system based on said forwarded set-point signal.
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11. A lithographic substrate focus control system, comprising:
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a substrate support structure having a substrate holder configured to hold a substrate;
a servo unit configured to position said substrate holder;
a sensor unit configured to determine a distance of at least one location point on the surface of said substrate relative to a reference plane;
a memory unit configured to store surface information of said substrate based on respective distances of corresponding said at least one location point on said substrate surface; and
a calculating unit configured to determine a feed-forward set-point signal based on said stored surface information, wherein said feed-forward set-point signal is forwardly fed to said servo unit in order to position said substrate holder. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification