Off-axis leveling in lithographic projection apparatus
First Claim
Patent Images
1. A lithographic projection apparatus comprising:
- an illumination system constructed and arranged to irradiate at least a portion of a reflective mask a first movable support constructed and arranged to hold said reflective mask, and having a physical reference surface fixed thereon;
a second support constructed and arranged to hold a substrate;
a projection system constructed and arranged to image the irradiated portion of the reflective mask onto a target portion of the substrate;
a positioning system constructed and arranged to move said first support between an exposure station, at which said projection system can image said mask portion onto said substrate, and a measurement station;
a height mapping system located at said measurement station comprising at least one sensor constructed and arranged both to measure positions of a plurality of points on a surface of said mask in a first direction substantially perpendicular to said surface and to measure a position of said physical reference surface in said first direction, said lithographic apparatus constructed and arranged to create a height map, relative to said physical reference surface, from said positions of the plurality of points on the surface of the mask;
a position measuring system located at said exposure station constructed and arranged to measure a position of said physical reference surface in said first direction, after movement of said first support to said exposure station; and
a position controller constructed and arranged to control a position of said first support in at least said first direction, during exposure of said target portion, in accordance with said height map and said position measured by said position measuring system.
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Accused Products
Abstract
In an off-axis leveling procedure a height map of a mask is generated at a measurement station. The height map is referenced to a physical reference surface of a mask support. 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 the mask support to position the exposure area on the mask in best focus during exposure.
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Citations
60 Claims
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1. A lithographic projection apparatus comprising:
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an illumination system constructed and arranged to irradiate at least a portion of a reflective mask a first movable support constructed and arranged to hold said reflective mask, and having a physical reference surface fixed thereon;
a second support constructed and arranged to hold a substrate;
a projection system constructed and arranged to image the irradiated portion of the reflective mask onto a target portion of the substrate;
a positioning system constructed and arranged to move said first support between an exposure station, at which said projection system can image said mask portion onto said substrate, and a measurement station;
a height mapping system located at said measurement station comprising at least one sensor constructed and arranged both to measure positions of a plurality of points on a surface of said mask in a first direction substantially perpendicular to said surface and to measure a position of said physical reference surface in said first direction, said lithographic apparatus constructed and arranged to create a height map, relative to said physical reference surface, from said positions of the plurality of points on the surface of the mask;
a position measuring system located at said exposure station constructed and arranged to measure a position of said physical reference surface in said first direction, after movement of said first support to said exposure station; and
a position controller constructed and arranged to control a position of said first support in at least said first direction, during exposure of said target portion, in accordance with said height map and said position measured by said position measuring system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A lithographic projection apparatus comprising:
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a first movable support constructed and arranged to hold a mask, and having a physical reference surface fixed thereon;
a second support constructed and arranged to hold a substrate;
a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate;
a positioning system constructed and arranged to move said first support between an exposure station, at which said projection system can image said mask portion onto said substrate, and a measurement station;
a height mapping system, located at said measurement station, constructed and arranged to measure positions of a plurality of points on a surface of said mask in a first direction substantially perpendicular to said surface, to measure a position of said physical reference surface in said first direction and to measure a position of said first support in said first direction substantially simultaneously with the measurement of at least one of the positions of the plurality of points on the surface of said mask and the position of said physical reference surface, said lithographic apparatus constructed and arranged to create a height map, relative to said physical reference surface, from said positions of the plurality of points on the surface of the mask;
a position measuring system located at said exposure station constructed and arranged to measure a position of said physical reference surface in said first direction, after movement of said second object table to said exposure station; and
a position controller constructed and arranged to control a position of said first support in at least said first direction, during exposure of said target portion, in accordance with said height map and said position measured by said position measuring system. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A lithographic projection apparatus comprising:
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a first movable support constructed and arranged to hold a mask, and having a physical reference surface fixed thereon;
a second support constructed and arranged to hold a substrate;
a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate;
a positioning system constructed and arranged to move said first support between an exposure station, at which said projection system can image said mask portion onto said substrate, and a measurement station;
a height mapping system located at said measurement station and constructed and arranged to measure positions of a plurality of points on a surface of said mask in a first direction substantially perpendicular to said surface and to measure at a substantially same position in a plane substantially perpendicular to said first direction positions of said first support in said first direction, said lithographic apparatus constructed and arranged to create a height map, relative to said physical reference surface, from said positions of the plurality of points on the surface of the mask and said positions of said first support;
a position measuring system located at said exposure station constructed and arranged to measure a position of said physical reference surface in said first direction, after movement of said first support to said exposure station; and
a position controller constructed and arranged to control a position of said first support in at least said first direction, during exposure of said target portion, in accordance with said height map and said position measured by said position measuring system. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
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49. A lithographic projection apparatus comprising:
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a first movable support constructed and arranged to hold a mask, and having a physical reference surface fixed thereon;
a second support constructed and arranged to hold a substrate;
a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate;
a positioning system constructed and arranged to move said first support between an exposure station, at which said projection system can image said mask portion onto said substrate, and a measurement station;
a height mapping system located at said measurement station and constructed and arranged to measure positions of a plurality of points on a surface of said mask in a first direction substantially perpendicular to said surface, to measure a position of said physical reference surface in said first direction and to measure at a substantially same position to the measurement of said physical reference surface in a plane substantially perpendicular to said first direction a position of said first support in said first direction, said lithographic apparatus constructed and arranged to create a height map, relative to said physical reference surface, from said positions of the plurality of points on the surface of the mask;
a position measuring system located at said exposure station constructed and arranged to measure a position of said physical reference surface in said first direction, after movement of said first support to said exposure station; and
a position controller constructed and arranged to control a position of said support in at least said first direction, during exposure of said target portion, in accordance with said height map and said position measured by said position measuring system. - View Dependent Claims (50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60)
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Specification