US6674510B1 — Off-axis levelling in lithographic projection app…

Claim 1

Independent Claim 255 words

A lithographic projection apparatus comprising: a first object table constructed and arranged to hold a mask; a second, movable object table constructed and arranged to hold a substrate and having a physical reference surface fixed thereon; 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 second object table 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 substrate 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 substrate; 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 second object table 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.

Claim 2

Dependent Claim 255 words

A lithographic projection apparatus comprising: a first object table constructed and arranged to hold a mask; a second, movable object table constructed and arranged to hold a substrate and having a physical reference surface fixed thereon; 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 second object table 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 substrate 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 substrate; 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 second object table 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.

Claim 3

Dependent Claim 37 words

Apparatus according to claim 1 , wherein said controller is further arranged to control a tilt of said second object table about at least one axis perpendicular to said first direction in accordance with said height map.

Claim 4

Dependent Claim 30 words

Apparatus according to claim 1 , wherein said sensor comprises a level sensor constructed and arranged to simultaneously measure positions in said first direction of a linear array of points.

Claim 5

Dependent Claim 36 words

An apparatus according to claim 3 , wherein the level sensor is constructed and arranged to adjust the linear array of points to match a width of a target portion on the surface of the substrate.

Claim 6

Dependent Claim 37 words

An apparatus according to claim 3 , wherein the level sensor is constructed and arranged such that a central point of the linear array of points passes along a midline of the target portion during height mapping.

Claim 7

Dependent Claim 36 words

An Apparatus according to claim 3 , wherein the level sensor is constructed and arranged such that data obtained from points of the linear array which do not lie wholly within the target portion are ignored.

Claim 8

Dependent Claim 80 words

An apparatus according to claim 3 , wherein the level sensor is constructed and arranged to measure a position in said first direction of an additional point which is spaced apart from the linear array of points, the additional point being measurable over a wider range of positions in the first direction than the linear array of points, and the level sensor is constructed and arranged such that during height mapping the additional point precedes the linear array of points.

Claim 9

Dependent Claim 74 words

An apparatus according to claim 7 , wherein the level sensor comprises a dedicated detector configured to measure the position in the first direction of the additional point, the dedicated detector comprising an array of detection regions which lie in either side of a line corresponding to a desired value of the measured position in the first direction, the array being symmetric about a line which bisects a central detection region of the array.

Claim 10

Dependent Claim 33 words

An apparatus according to claim 8 , wherein the linear array of points and the additional point are illuminated for measurement using a single optical source, the projection grating and the projection optics.

Claim 11

Dependent Claim 47 words

Apparatus according to claim 1 , wherein said sensor comprises a level sensor constructed and arranged to measure a position of a measurement beam reflected by at least one of said surface and said physical reference surface whose position in said first direction is to be measured.

Claim 12

Dependent Claim 112 words

Apparatus according to claim 10 , wherein said level sensor comprises: a projection grating; projection optics constructed and arranged to project an image of said projection grating onto said at least one of said surface and said physical reference surface whose position in said first direction is to be measured; a detection grating; detection optics constructed and arranged to focus light reflected by said at least one of said surface and said physical reference surface to form on said detection grating an image of said projection grating; and a detector constructed and arranged to detect Moiré patterns formed by an overlay of said image of said projection grating on said detection grating.

Claim 13

Dependent Claim 41 words

Apparatus according to claim 11 , wherein said level sensor further comprises a radiation source or illuminator constructed and arranged to illuminate said projection grating with polychromatic radiation and wherein said projection optics and said detection optics comprise reflective optical elements.

Claim 14

Dependent Claim 33 words

An apparatus according to claim 11 , wherein the linear array of points and the additional point are illuminated for measurement using a single optical source, the projection grating and the projection optics.

Claim 15

Dependent Claim 36 words

An apparatus according to claim 11 , wherein said projection grating is positioned with a rotation around its optical axis such that said image of said projection grating is not parallel to any substrate co-ordinate axis.

Claim 16

Dependent Claim 41 words

An apparatus according to claim 11 , wherein said projection optics is constructed and arranged to project illumination forming the image, at an angle of between 60 degrees and 80 degrees relative to a normal to the surface of said substrate.

Claim 17

Dependent Claim 73 words

Apparatus according to claim 1 , wherein said height mapping system comprises a first sensor constructed and arranged to detect at least one of the positions of said plurality of points on the surface of said substrate and the position of said physical reference surface and a second sensor constructed and arranged to detect a position in said first direction of said second object table substantially simultaneously with measurements by said first sensor.

Claim 18

Dependent Claim 13 words

Apparatus according to claim 16 , wherein said second sensor comprises an interferometer.

Claim 19

Dependent Claim 18 words

Apparatus according to claim 16 , wherein said first sensor is said sensor and comprises a level sensor.

Claim 20

Dependent Claim 36 words

Apparatus according to claim 16 , wherein the measurement by said second sensor is made at a substantially same position in a plane substantially perpendicular to said first direction as the measurement by said first sensor.

Claim 21

Dependent Claim 34 words

An apparatus according to claim 16 , wherein the apparatus further comprises a synchronization bus configured and arranged to use clock signals to synchronize said substantially simultaneous measurement by said first and second sensors.

Claim 22

Dependent Claim 33 words

Apparatus according to claim 1 , wherein said position system comprises an image sensor mounted to said second object table and said physical reference surface comprises an upper surface of said image sensor.

Claim 23

Dependent Claim 33 words

Apparatus according to claim 1 , wherein said position measuring system is constructed and arranged to measure the position of said physical reference surface relative to the focal plane of said projection system.

Claim 24

Dependent Claim 52 words

An apparatus according to claim 22 , wherein the apparatus further comprises an additional sensor at the exposure station, the sensor being constructed and arranged to provide an initial determination of the position in said first direction at which said physical reference surface corresponds to the focal plane of said projection system.

Claim 25

Dependent Claim 45 words

Apparatus according to claim 1 , wherein: said second object table has a plurality of spaced-apart physical reference surfaces; and said lithographic apparatus is constructed and arranged to create the height map relative to a reference plane defined by said plurality of physical reference surfaces.

Claim 26

Dependent Claim 80 words

An apparatus according to claim 24 , wherein the additional sensor comprises at least two detectors and a beamsplitter constructed and arranged such that a zero measurement is obtained when a beam incident on the beamsplitter is split equally into two beans by the beamsplitter to the at least two detectors, the beamsplitter being constructed and arranged such that the two beams upon exiting the beamsplitter have substantially the same cross-sectional shape and have traveled substantially the same path length.

Claim 27

Dependent Claim 112 words

Apparatus according to claim 1 , further comprising: a height mapping system located at said exposure station constructed and arranged to measure positions of a plurality of points on a surface of a substrate in a direction substantially perpendicular to said 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 substrate; and a height calibrator constructed and arranged to compare height maps of said substrate prepared by each of said height mapping systems to derive a relative calibration for separate position detection systems provided at said measurement and exposure stations.

Claim 28

Dependent Claim 108 words

Apparatus according to claim 26 , wherein: said height mapping system located at said measurement station comprises a confidence sensor constructed and arranged to measure the positions in a direction substantially perpendicular to the substrate of the same plurality of points on the surface of the substrate as measured by the height mapping system located at said exposure station; and said lithogaphic apparatus is constructed and arranged to create the height map used for comparison by the height calibrator, said height map created, relative to said physical reference surface, from said positions of the plurality of points on the surface of the substrate measured by the confidence sensor.

Claim 29

Dependent Claim 51 words

Apparatus according to claim 1 , wherein said lithographic apparatus is constructed and arranged to calculate from said height map Z, R x , and R y position setpoints for said position controller, wherein Z is in said first direction and X and Y are substantially perpendicular to said first direction.

Claim 30

Dependent Claim 23 words

Apparatus according to claim 28 , wherein said setpoints are calculated using one of a least squares method and a moving focus method.

Claim 31

Dependent Claim 34 words

An appartus according to claim 28 , wherein the apparatus is constructed and arranged to calculate the position setpoints for the position controller before the second object table is moved to the exposure station.

Claim 32

Dependent Claim 65 words

Apparatus according to claim 1 , wherein said lithographic apparatus is constructed and arranged to calculate from said height map a sequence of Z, R x , and R y position setpoints for said position controller matched to an X-Y scan path of said second object table, wherein Z is in said first direction and X and Y are substantially perpendicular to said first direction.

Claim 33

Dependent Claim 89 words

An apparatus according to claim 1 , wherein the measurement station comprises a position controller constructed and arranged to control a position of the second object table in at least the first direction, and the position of the physical reference surface in the first direction is adjusted to a preferred value prior to height mapping, and said preferred value is set as a zero measurement in the first direction of the at least one sensor and as a zero measurement in the first direction of the position measuring system.

Claim 34

Dependent Claim 40 words

An apparatus according to claim 32 , wherein the preferred value is at or adjacent to a centre point of a range of measurements in the first direction for which the at least one sensor provides a substantially linear output.

Claim 35

Dependent Claim 88 words

An apparatus according to claim 32 , wherein the position controller is constructed and arranged to control in two steps the adjustment of the position of the physical reference surface to the preferred value, said two steps including a first step consisting of an initial coarse adjustment of the position of the physical reference surface based upon an output of the position measuring system, and a second step consisting of a fine adjustment of the physical reference surface based upon an output of the at least one sensor.

Claim 36

Dependent Claim 57 words

An apparatus according to claim 1 , wherein the at least one sensor has a measurement range over which an output of said at least one sensor is linearly related to the position in the first direction, or over which the output of said at least one sensor is linearized to the position in the first direction.

Claim 37

Dependent Claim 77 words

An apparatus according to claim 35 , wherein the at least one sensor is constructed and arranged to provide feedback to the position controller, and the position controller is constructed and arranged to receive said feedback and based upon the feedback, the position of the second object table in the first direction is adjusted such that the surface of the substrate remains in the linear or linearized range of the at least one sensor during height mapping.

Claim 38

Dependent Claim 36 words

An apparatus according to claim 36 , wherein the position controller is constructed and arranged to adjust the position of the second object table in the first direction according to a global wedge of the substrate.

Claim 39

Dependent Claim 32 words

An apparatus according to claim 35 , further comprising a device configured to retain a correction table or formula which is used to linearize the output of the at least one sensor.

Claim 40

Dependent Claim 44 words

An apparatus according to claim 1 , wherein the second object table is constructed and arranged to fixedly hold the substrate using vacuum suction, and to release and reapply the vacuum suction prior to height mapping to allow relaxing thermal stresses in the substrate.

Claim 41

Dependent Claim 293 words

A lithogaphic projection apparatus comprising: a first object table constructed and arranged to hold a mask; a second, movable object table constructed and arranged to hold a substrate and having a physical reference surface fixed thereon; 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 second object table 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 substrate 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 second object table 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 substrate 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 substrate; 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 second object table 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.

Claim 42

Dependent Claim 293 words

A lithogaphic projection apparatus comprising: a first object table constructed and arranged to hold a mask; a second, movable object table constructed and arranged to hold a substrate and having a physical reference surface fixed thereon; 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 second object table 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 substrate 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 second object table 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 substrate 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 substrate; 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 second object table 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.

Claim 43

Dependent Claim 45 words

Apparatus according to claim 40 , wherein said height mapping system comprises at least one sensor constructed and arranged both to measure the positions of the plurality of points on the surface of said substrate and to measure the position of said physical reference surface.

Claim 44

Dependent Claim 63 words

An apparatus according to claim 41 , wherein the position of the physical reference surface in the first direction is adjusted to a preferred value prior to height mapping, and said preferred value is set as a zero measurement in the first direction of the at least one sensor and as a zero measurement in the first direction of the position measuring system.

Claim 45

Dependent Claim 40 words

An apparatus according to claim 42 , wherein the preferred value is at or adjacent to a centre point of a range of measurements in the first direction for which the at least one sensor provides a substantially linear output.

Claim 46

Dependent Claim 88 words

An apparatus according to claim 42 , wherein the position controller is constructed and arranged to control in two steps the adjustment of the position of the physical reference surface to the preferred value, said two steps including a first step consisting of an initial coarse adjustment of the position of the physical reference surface based upon an output of the position measuring system, and a second step consisting of a fine adjustment of the physical reference surface based upon an output of the at least one sensor.

Claim 47

Dependent Claim 57 words

An apparatus according to claim 41 , wherein the at least one sensor has a measurement range over which an output of said at least one sensor is linearly related to the position in the first direction, or over which the output of said at least one sensor is linearized to the position in the first direction.

Claim 48

Dependent Claim 77 words

An apparatus according to claim 45 , wherein the at least one sensor is constructed and arranged to provide feedback to the position controller, and the position controller is constructed and arranged to receive said feedback and based upon the feedback, the position of the second object table in the first direction is adjusted such that the surface of the substrate remains in the linear or linearized range of the at least one sensor during height mapping.

Claim 49

Dependent Claim 36 words

An apparatus according to claim 45 , wherein the position controller is constructed and arranged to adjust the position of the second object table in the first direction according to a global wedge of the substrate.

Claim 50

Dependent Claim 32 words

An apparatus according to claim 45 , further comprising a device configured to retain a correction table or formula which is used to linearize the output of the at least one sensor.

Claim 51

Dependent Claim 37 words

An apparatus according to claim 41 , wherein said at least one sensor comprises a level sensor constructed and arranged to simultaneously measure positions in said first direction of a linear array of points on said substrate.

Claim 52

Dependent Claim 36 words

An apparatus according to claim 49 , wherein the level sensor is constructed and arranged to adjust the linear array of points to match a width of a target portion on the surface of the substrate.

Claim 53

Dependent Claim 37 words

An apparatus according to claim 49 , wherein the level sensor is constructed and arranged such that a central point of the linear array of points passes along a midline of the target portion during height mapping.

Claim 54

Dependent Claim 36 words

An Apparatus according to claim 49 , wherein the level sensor is constructed and arranged such that data obtained from points of the linear array which do not lie wholly within the target portion are ignored.

Claim 55

Dependent Claim 80 words

An apparatus according to claim 49 , wherein the level sensor is constructed and arranged to measure a position in said first direction or an additional point which is spaced apart from the linear array of points, the additional point being measurable over a wider range of positions in the first direction than the linear array of points, and the level sensor is constructed and arranged such that during height mapping the additional point precedes the linear array of points.

Claim 56

Dependent Claim 74 words

An apparatus according to claim 53 , wherein the level sensor comprises a dedicated detector configured to measure the position in the first direction of the additional point, the dedicated detector comprising an array of detection regions which lie in either side of a line corresponding to a desired value of the measured position in the first direction, the array being symmetric about a line which bisects a central detection region of the array.

Claim 57

Dependent Claim 37 words

Apparatus according to claim 40 , wherein said controller is further arranged to control a tilt of said second object table about at least one axis perpendicular to said first direction in accordance with said height map.

Claim 58

Dependent Claim 49 words

Apparatus according to claim 40 , wherein said height mapping system comprises a level sensor constructed and arranged to measure a position of a measurement beam reflected by at least one of said surface and said physical reference surface whose position in said first direction is to be measured.

Claim 59

Dependent Claim 112 words

Apparatus according to claim 56 , wherein said level sensor comprises: a projection grating; projection optics constructed and arranged to project an image of said projection grating onto said at least one of said surface and said physical reference surface whose position in said first direction is to be measured; a detection grating; detection optics constructed and arranged to focus light reflected by said at least one of said surface and said physical reference surface to form on said detection grating an image of said projection grating; and a detector constructed and arranged to detect Moiré patterns formed by an overlay of said image of said projection grating on said detection grating.

Claim 60

Dependent Claim 73 words

Apparatus according to claim 40 , wherein said height mapping system comprises a first sensor constructed and arranged to detect at least one of the positions of said plurality of points on the surface of said substrate and the position of said physical reference surface and a second sensor constructed and arranged to detect a position in said first direction of said second object table substantially simultaneously with measurements by said first sensor.

Claim 61

Dependent Claim 40 words

Apparatus according to claim 58 , wherein said first sensor is constructed and arranged both to measure the positions of the plurality of points on the surface of said substrate and to measure the position of said physical reference surface.

Claim 62

Dependent Claim 13 words

Apparatus according to claim 58 , wherein said second sensor comprises an interferometer.

Claim 63

Dependent Claim 36 words

Apparatus according to claim 58 , wherein the measurement by said second sensor is made at a substantially same position in a plane substantially perpendicular to said first direction as the measurement by said first sensor.

Claim 64

Dependent Claim 34 words

Apparatus according to claim 40 , wherein said position measuring system comprises an image sensor mounted to said second object table and said physical reference surface comprises an upper surface of said image sensor.

Claim 65

Dependent Claim 33 words

Apparatus according to claim 40 , wherein said position measuring system is constructed and arranged to measure the position of said physical reference surface relative to the focal plane of said projection system.

Claim 66

Dependent Claim 45 words

Apparatus according to claim 40 , wherein: said second object table has a plurality of spaced-apart physical reference surfaces; and said lithographic apparatus is constructed and arranged to create the height map relative to a reference plane defined by said plurality of physical reference surfaces.

Claim 67

Dependent Claim 59 words

Apparatus according to claim 40 , wherein measurements of the position of said second object table and of at least one of the positions of the plurality of points on the surface of said substrate and the position of said physical reference surface are made at a substantially same position in a plane substantially perpendicular to said first direction.

Claim 68

Dependent Claim 51 words

Apparatus according to claim 40 , wherein said lithographic apparatus is constructed and arranged to calculate from said height map Z, R x , and R y position setpoints for said position controller, wherein Z is in said first direction and X and Y are substantially perpendicular to said first direction.

Claim 69

Dependent Claim 23 words

Apparatus according to claim 66 , wherein said setpoints are calculated using one of a least squares method and a moving focus method.

Claim 70

Dependent Claim 65 words

Apparatus according to claim 40 , wherein said lithographic apparatus is constructed and arranged to calculate from said height map a sequence of Z, R x , and R y position setpoints for said position controller matched to an X-Y scan path of said second object table, wherein Z is in said first direction and X and Y are substantially perpendicular to said first direction.

Claim 71

Dependent Claim 271 words

A lithographic projection apparatus comprising: a first object table constructed and arranged to hold a mask; a second, movable object table constructed and arranged to hold a substrate and having a physical reference surface fixed thereon; 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 second object table between all 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 substrate 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 second object table 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 substrate and said positions of said second object table; 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 second object table 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.

Claim 72

Dependent Claim 271 words

A lithographic projection apparatus comprising: a first object table constructed and arranged to hold a mask; a second, movable object table constructed and arranged to hold a substrate and having a physical reference surface fixed thereon; 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 second object table between all 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 substrate 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 second object table 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 substrate and said positions of said second object table; 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 second object table 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.

Claim 73

Dependent Claim 49 words

Apparatus according to claim 69 , wherein said height mapping system comprises at least one sensor constructed and arranged both to measure the positions of the plurality of points on the surface of said substrate and to measure a position of said physical reference surface in said first direction.

Claim 74

Dependent Claim 37 words

Apparatus according to claim 69 , wherein said controller is further arranged to control a tilt of said second object table about at least one axis perpendicular to said first direction in accordance with said height map.

Claim 75

Dependent Claim 49 words

Apparatus according to claim 69 , wherein said height mapping system comprises a level sensor constructed and arranged to measure a position of a measurement beam reflected by at least one or said surface and said physical reference surface whose position in said first direction is to be measured.

Claim 76

Dependent Claim 112 words

Apparatus according to claim 72 , wherein said level sensor comprises: a projection grating; projection optics constructed and arranged to project an image of said projection grating onto said at least one of said surface and said physical reference surface whose position in said first direction is to be measured; a detection grating; detection optics constructed and arranged to focus light reflected by said at least one of said surface and said physical reference surface to form on said detection grating an image of said projection grating; and a detector constructed and arranged to detect Moiré patterns formed by an overlay of said image of said projection grating on said detection grating.

Claim 77

Dependent Claim 77 words

Apparatus according to claim 69 , wherein said height mapping system comprises a first sensor constructed and arranged to detect at least one of the positions of said plurality of points on the surface of said substrate and a position of said physical reference surface in said first direction and a second sensor constructed and arranged to detect the positions in said first direction of said second object table substantially simultaneously with measurements by said first sensor.

Claim 78

Dependent Claim 40 words

Apparatus according to claim 74 , wherein said first sensor is constructed and arranged both to measure the positions of the plurality of points on the surface of said substrate and to measure the position of said physical reference surface.

Claim 79

Dependent Claim 13 words

Apparatus according to claim 74 , wherein said second sensor comprises an interferometer.

Claim 80

Dependent Claim 34 words

Apparatus according to claim 69 , wherein said position measuring system comprises an image sensor mounted to said second object table and said physical reference surface comprises an upper surface of said image sensor.

Claim 81

Dependent Claim 33 words

Apparatus according to claim 69 , wherein said position measuring system is constructed and arranged to measure the position of said physical reference surface relative to the focal plane of said projection system.

Claim 82

Dependent Claim 45 words

Apparatus according to claim 69 , wherein: said second object table has a plurality of spaced-apart physical reference surfaces; and said lithographic apparatus is constructed and arranged to create the height map relative to a reference plane defined by said plurality of physical reference surfaces.

Claim 83

Dependent Claim 51 words

Apparatus according to claim 69 , wherein said lithographic apparatus is constructed and arranged to calculate from said height map Z, R x , and R y position setpoints for said position controller, wherein Z is in said first direction and X and Y are substantially perpendicular to said first direction.

Claim 84

Dependent Claim 23 words

Apparatus according to claim 80 , wherein said setpoints are calculated using one of a least squares method and a moving focus method.

Claim 85

Dependent Claim 65 words

Apparatus according to claim 69 , wherein said lithographic apparatus is constructed and arranged to calculate from said height map a sequence of Z, R x , and R y position setpoints for said position controller matched to an X-Y scan path of said second object table, wherein Z is in said first direction and X and Y are substantially perpendicular to said first direction.

Claim 86

Dependent Claim 56 words

Apparatus according to claim 69 , wherein said height mapping system is constructed and arranged to measure a position of said physical reference surface in said first direction and to measure at a substantially same position in a plane substantially perpendicular to said first direction a position of said second object table in said first direction.

Claim 87

Dependent Claim 285 words

A lithographic projection apparatus comprising: a first object table constructed and arranged to hold a mask; a second, movable object table constructed and arranged to hold a substrate and having a physical reference surface fixed thereon; 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 second object table 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 substrate 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 second object table 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 substrate; 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 second object table 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.

Claim 88

Dependent Claim 285 words

A lithographic projection apparatus comprising: a first object table constructed and arranged to hold a mask; a second, movable object table constructed and arranged to hold a substrate and having a physical reference surface fixed thereon; 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 second object table 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 substrate 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 second object table 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 substrate; 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 second object table 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.

Claim 89

Dependent Claim 88 words

Apparatus according to claim 84 , wherein said height mapping system is constructed and arranged to measure at a substantially same position to the measurement of said plurality of points in a plane substantially perpendicular to said first direction positions of said second object table in said first direction, said lithographic apparatus constructed and arranged to create the height map, relative to said physical reference surface, from said positions of the plurality of points on the surface of the substrate and said positions of said second object table.

Claim 90

Dependent Claim 49 words

Apparatus according to claim 84 , wherein said height mapping system comprises at least one sensor constructed and arranged both to measure the positions of the plurality of points on the surface of said substrate and to measure the position of said physical reference surface in said first direction.

Claim 91

Dependent Claim 77 words

Apparatus according to claim 84 , wherein said height mapping system comprises a first sensor constructed and arranged to detect at least one of the positions of said plurality of points on the surface of said substrate and a position of said physical reference surface in said first direction and a second sensor constructed and arranged to detect the positions in said first direction of said second object table substantially simultaneously with measurements by said first sensor.

Claim 92

Dependent Claim 40 words

Apparatus according to claim 87 , wherein said first sensor is constructed and arranged both to measure the positions of the plurality of points on the surface of said substrate and to measure the position of said physical reference surface.

Claim 93

Dependent Claim 13 words

Apparatus according to claim 87 , wherein said second sensor comprises an interferometer.

Claim 94

Dependent Claim 34 words

Apparatus according to claim 84 , wherein said position measuring system comprises an image sensor mounted to said second object table and said physical reference surface comprises an upper surface of said image sensor.

Claim 95

Dependent Claim 33 words

Apparatus according to claim 84 , wherein said position measuring system is constructed and arranged to measure the position of said physical reference surface relative to the focal plane of said projection system.

Claim 96

Dependent Claim 45 words

Apparatus according to claim 84 , wherein: said second object table has a plurality of spaced-apart physical reference surfaces; and said lithographic apparatus is constructed and arranged to create the height map relative to a reference plane defined by said plurality of physical reference surfaces.

Claim 97

Dependent Claim 51 words

Apparatus according to claim 84 , wherein said lithographic apparatus is constructed and arranged to calculate from said height map Z, R x , and R y position setpoints for said position controller, wherein Z is in said first direction and X and Y are substantially perpendicular to said first direction.

Claim 98

Dependent Claim 23 words

Apparatus according to claim 93 , wherein said setpoints are calculated using one of a least squares method and a moving focus method.

Claim 99

Dependent Claim 65 words

Apparatus according to claim 84 , wherein said lithographic apparatus is constructed and arranged to calculate from said height map a sequence of Z, R x , and R y position setpoints for said position controller matched to an X-Y scan path of said second object table, wherein Z is in said first direction and X and Y are substantially perpendicular to said first direction.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2007-01-05	2007-07-07	2008-01-06	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2011-01-05	2011-07-07	2012-01-06	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2015-01-05	2015-07-07	2016-01-06	$7700.00	Window Closed / Lapsed

Off-axis levelling in lithographic projection apparatus

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