Off-axis levelling in lithographic projection apparatus
First Claim
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1. A lithographic projection apparatus comprising:
- a radiation system constructed and arranged to condition a beam of radiation including an EUV radiation;
a patterning device support constructed and arranged to support a patterning device, said patterning device being configured to pattern the beam of radiation including the EUV radiation to form a patterned beam of radiation;
a substrate support constructed and arranged to hold a substrate;
an exposure station having a projection system configured to project the patterned beam of radiation including the EUV radiation onto target portions of the substrate;
a sensor constructed and arranged to measure a position of each of a plurality of points on a surface of said patterning device in a first direction perpendicular to said surface so as to generate a height map of said surface of said patterning device; and
a controller configured to control a tilt of said patterning device support about at least one direction substantially perpendicular to said first direction based on said height map.
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Abstract
In an off-axis levelling procedure a height map of the substrate is generated at a measurement station. The height map is referenced to a physical reference surface of the substrate table. The physical reference surface may be a surface in which is inset a transmission image sensor. At the exposure station the height of the physical reference surface is measured and related to the focal plane of the projection lens. The height map can then be used to determine the optimum height and/or tilt of substrate table to position the exposure area on the substrate in best focus during exposure. The same principles can be applied to (reflective) masks.
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Citations
14 Claims
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1. A lithographic projection apparatus comprising:
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a radiation system constructed and arranged to condition a beam of radiation including an EUV radiation; a patterning device support constructed and arranged to support a patterning device, said patterning device being configured to pattern the beam of radiation including the EUV radiation to form a patterned beam of radiation; a substrate support constructed and arranged to hold a substrate; an exposure station having a projection system configured to project the patterned beam of radiation including the EUV radiation onto target portions of the substrate; a sensor constructed and arranged to measure a position of each of a plurality of points on a surface of said patterning device in a first direction perpendicular to said surface so as to generate a height map of said surface of said patterning device; and a controller configured to control a tilt of said patterning device support about at least one direction substantially perpendicular to said first direction based on said height map. - 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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conditioning a beam of radiation including an EUV radiation; patterning the beam of radiation including the EUV radiation with a patterning device to form a patterned beam of radiation, said patterning device being supported by a patterning device support; projecting the patterned beam of radiation including the EUV radiation with a projection system onto target portions of a substrate; measuring a position of each of a plurality of points on a surface of said patterning device in a first direction perpendicular to said surface so as to generate a height map of said surface of said patterning device, and controlling a tilt of said patterning device support about at least one direction substantially perpendicular to said first direction based on said height map. - View Dependent Claims (11, 12, 13, 14)
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Specification