Imaging system

Abstract

A plate for use in an imaging system to determine two optical properties of an illumination beam of the imaging system configured to illuminate an illumination area with the illumination beam. The plate includes a plurality of markers, wherein a first subset of the plurality of markers includes markers for determining a first type of a first optical property of the illumination beam, and a second subset of the plurality of markers includes markers for determining a second type of a second optical property of the illumination beam. The plurality of markers are located within a marker area of ​​the plate, and the marker area substantially corresponds to the illumination area.

Description

Technical Field

[0001] This invention relates to an imaging system, and more particularly to an apparatus and method for determining one or more optical properties of an imaging system. The imaging system may be part of a lithography apparatus. Prior Technology

[0002] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. Lithography apparatuses can be used, for example, in the manufacture of integrated circuits (ICs). A lithography apparatus can project a pattern at a patterned device (e.g., a mask) onto a radiation-sensitive material (resist) layer disposed on a substrate. The lithography apparatus includes an imaging system that images the pattern at the patterned device onto a plane containing the substrate. Specifically, a projection system can be used to focus radiation patterned by the patterned device onto the substrate.

[0003] To project a pattern onto a substrate, a lithography apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Compared to a lithography apparatus using radiation with a wavelength of, for example, 193 nm, a lithography apparatus using extreme ultraviolet (EUV) radiation with wavelengths in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0004] Radiation supplied to a patterning device possesses a range of optical properties. For example, radiation may have a specific angular distribution, which can be referred to as the pupil shape. Projection systems can introduce optical aberrations that cause the image formed on the substrate to deviate from the desired image (e.g., the diffraction-limited image of the patterning device). Optical aberrations can be considered another type of optical property of radiation. Knowledge of the optical properties of radiation allows for better control of radiation and / or optimization of lithography processes.

[0005] Methods and apparatus may be required for accurately determining optical properties such as pupil shape and optical aberrations. Summary of the Invention

[0006] In one example described herein, an imaging system includes: a first plane configured to receive an illumination beam in a first region; a second plane configured to receive an image of the first region in a second region of the second plane; a first plate including a first plurality of markers; and a second plate including a second plurality of markers. A first subset of the first plurality of markers includes markers for determining a first type of a first optical property of the illumination beam. A second subset of the first plurality of markers includes markers for determining a second type of a second optical property of the illumination beam. The first plate is positionable in the first plane such that the first plurality of markers are located within the first region. The first subset of the second plurality of markers includes markers for determining the first type of the first optical property of the illumination beam. The second subset of the second plurality of markers includes markers for determining the second type of the second optical property of the illumination beam. The arrangement of the second plurality of markers substantially matches the arrangement of the first plurality of markers. The second plate can be positioned in the second plane such that the second plurality of markers are located within the second region. The imaging system further includes a detector that can be positioned in a third plane. The detector is operable to receive radiation from the second plate when the second plate is positioned in the second region; and to output a signal indicating one of the first optical properties and / or the second optical properties of the illumination beam.

[0007] This configuration enables the determination of the first and second optical properties of the illumination beam substantially simultaneously. That is, the illumination beam can illuminate the first plurality of markers in the first plane, and the first and second optical properties of the illumination beam can be determined without moving the first plate or the illumination beam. This results in a considerable time saving compared to determining the first and second optical properties in two separate measurements.

[0008] The imaging system can be a lithography system, which can be used to form an image of a photomask on a substrate (e.g., a resist-coated silicon wafer). A first plane can be referred to as an object plane. The first plane can be a plane in which the photomask can be positioned during substrate exposure. The first plane can be referred to as being at the photomask level, and an object placed in the first plane can be referred to as being at the photomask level. A second plane can be referred to as an image plane. The second plane can be a plane in which the substrate can be positioned during substrate exposure. The second plane can be referred to as being at the substrate level, and an object placed in the second plane can be referred to as being at the substrate level.

[0009] The first region may be referred to as the illumination region, slit, illumination slit, or exposure slit. The first region may also be referred to as the magnification mask alignment slit. Similarly, the second region may be referred to as the slit, illumination slit, or exposure slit. The second region may also be referred to as the substrate alignment slit.

[0010] The illumination beam can be generated by an illumination system, which may also include a portion of an imaging system. The imaging system may further include imaging components, such as a projection system, operable to form an image of the first region at the second region.

[0011] Generally, the first and second regions can be elongated, each having a longer and a shorter dimension. The first and second regions can be curved or straight. The shorter dimension can coincide with the scanning direction of the imaging system, and the longer dimension can coincide with the non-scanning direction of the imaging system.

[0012] The configuration of the second plurality of markers substantially matching the configuration of the first plurality of markers means that the first plurality of markers and the second plurality of markers are configured in substantially the same way. Specifically, the configuration of the second plurality of markers substantially matching the configuration of the first plurality of markers may mean that the spatial ordering of the first and second types of markers within the first plurality of markers is the same as the spatial ordering of the first and second types of markers within the second plurality of markers. For example, the number of markers in the first subset of the first plurality of markers may be the same as the number of markers in the first subset of the second plurality of markers; the number of markers in the second subset of the first plurality of markers may be the same as the number of markers in the second subset of the second plurality of markers; and the spatial ordering of the first and second types of markers within the first plurality of markers may be the same as the spatial ordering of the first and second types of markers within the second plurality of markers. In use, the first plate can be positioned such that an illumination beam generated by the illumination system is received by the first plate in a first area and forms images of a first plurality of markers in a second area. The illumination beam containing the images of the first plurality of markers can be referred to as a patterned illumination beam. In use, the second plate is positionable such that the image of each of the first plurality of markers formed in the second area coincides with a corresponding one of the second plurality of markers. That is, the first and second plates can be configured in a conjugate arrangement.

[0013] For the avoidance of doubt, the fact that the first plate includes a first plurality of markers and the second plate includes a second plurality of markers, and that the arrangement of the second plurality of markers substantially matches the arrangement of the first plurality of markers, does not preclude the presence of additional markers on the first or second plate. For example, in some embodiments, the second plate may include additional markers having an arrangement substantially matching that of a plurality of markers on another plate, which may be individually positioned in a first plane such that such a plurality of markers on this other plate may be located within a first region.

[0014] The second plate, positioned within the second zone, is intended to house a second plurality of markers within the second zone. It is claimed that when the second plate is configured in this manner, the detector receives radiation from the second plurality of markers. The second plate may be attached to the detector or may form part of the detector.

[0015] The signal may contain information relating to at least one optical property of the radiated beam from the first and / or second illumination zones of the illumination system. The optical property may relate to one or more properties of the illumination system of the imaging system, such as the pupil shape of the illumination at the first plane. Additionally, the optical property may relate to one or more properties of the projection system, such as aberrations caused by the imaging element (e.g., by the projection system) from the first plane to the second plane. Aberrations caused by the imaging element can be determined by judging the aberration map of the illumination beam in the second plane.

[0016] In some embodiments, a first plurality of markers may be simultaneously positioned within a first area. As used herein, simultaneous positioning means that all the first plurality of markers can be located in the first area at the same time. That is, all markers can be illuminated simultaneously without moving them. Similarly, in some embodiments, a second plurality of markers may be simultaneously positioned within a second area. As used herein, simultaneous positioning means that all the second plurality of markers can be located in the second area at the same time. That is, all markers can be illuminated simultaneously without moving them.

[0017] The markers may align in a first direction on the first and second plates. When the plates are positioned in use, the markers may align or not align in a second direction on the first and second plates, as now discussed.

[0018] The configuration of the second plurality of markers can substantially match the configuration of the first plurality of markers, such that when the first plate is placed in the first area and the second plate is placed in the second area, one image of each of the first plurality of markers coincides with a corresponding one of the second plurality of markers in a first direction.

[0019] The placement of the first board in the first zone is intended to mean that the first board is placed in the first zone such that the first plurality of markers are located within the first zone.

[0020] The first direction may correspond to the longer dimension of the first and second regions. The first direction may correspond to the non-scanning direction of the imaging system. With this configuration, the image of each of the first plurality of markers can be projected onto a corresponding one of the second plurality of markers by the relative movement of the first and second plates in a second direction perpendicular to the first direction. The image of the first plurality of markers can be formed by the projection system.

[0021] The configuration of the second plurality of markers can substantially match the configuration of the first plurality of markers, such that when the first plate is placed in the first area and the second plate is placed in the second area, one image of each of the first plurality of markers coincides with a corresponding one of the second plurality of markers.

[0022] That is, the image of each of the first plurality of markers coincides with the corresponding one of the second plurality of markers in both the first direction and the second direction perpendicular to the first direction. This configuration does not require any relative movement of the first and second plates to image all the first plurality of markers onto all the second plurality of markers. Therefore, all corresponding magnification mask level and substrate level markers can be used to simultaneously determine the optical properties of the illumination beam. The images of the first plurality of markers can be formed by a projection system.

[0023] The configurations of the first and second plates can be identical. That is, the arrangement of the first plurality of markers can be the same as that of the second plurality of markers. Alternatively, and for example, if scaling is applied to the imaging between the first and second planes, the arrangement of markers on the first plate can be a scaled version of the arrangement of markers on the second plate.

[0024] The first optical property may be an aberration map of the illumination beam (e.g., it may characterize aberrations introduced by the projection system, rather than the image on the first to second regions). Each of the markers of the first type may include a grating.

[0025] An aberration map may contain a representation of one or more aberrations in an illumination beam. One or more aberrations may be imparted to the illumination beam by a projection system. Thus, a first optical property may represent the aberration map of the projection system. One or more aberrations may be measured, for example, with reference to one or more orders of Rennie aberrations. The use of a grating makes it possible to determine the aberration state from the illumination beam interacting with the grating.

[0026] The second optical property can be that the illumination beam is distributed at one corner of the first region. Each of the second type of markers can contain a pinhole.

[0027] Angular distribution can correspond to the shape or intensity profile of an illumination beam. Angular distribution can also be referred to as pupil shape. The use of a pinhole allows for the determination of the shape of the angular distribution of the illumination beam interacting with the pinhole.

[0028] The imaging system may further include a third plurality of markers, which may be positioned within the first plane. A first subset of the third plurality of markers may include markers for determining a first type of a first optical property of the illumination beam. A second subset of the third plurality of markers may include markers for determining a second type of a second optical property of the illumination beam. The third plurality of markers may be positioned within the first region. The configuration of the third plurality of markers may differ from the configuration of the first plurality of markers. The imaging system may further include a fourth plurality of markers, which may be positioned within the second plane. A first subset of the fourth plurality of markers may include markers for determining a first type of a first optical property of the illumination beam. A second subset of the fourth plurality of markers may include markers for determining a second type of a second optical property of the illumination beam. The fourth plurality of markers may be positioned within the second region. The configuration of the fourth plurality of markers may substantially match the configuration of the third plurality of markers.

[0029] In some embodiments, a third plurality of markers may be simultaneously positioned within a first area. As used herein, simultaneous positioning means that all third plurality of markers can be located in the first area simultaneously. That is, all markers can be illuminated simultaneously without moving them. Similarly, in some embodiments, a fourth plurality of markers may be simultaneously positioned within a second area. As used herein, simultaneous positioning means that all fourth plurality of markers can be located in the second area simultaneously. That is, all markers can be illuminated simultaneously without moving them.

[0030] Various plurality of markers can be located at a set of field points within the first and second zones. For example, the first and second plurality of markers can sample a set of field points that is substantially the same as the third and fourth plurality of markers, but the configuration or arrangement of the first and second types of markers within the first and second plurality of markers can differ from the configuration and arrangement of the first and second types of markers within the third and fourth plurality of markers. This configuration allows for sampling of a first optical property at the first set of field points and a second optical property at the second set of field points when using the first and second plurality of markers, and also allows for sampling of the first optical property at the second set of field points and the first optical property at the first set of field points, for example, when using the third and fourth plurality of markers. Therefore, information obtained for a specific field point can be relatively easily alternated. Furthermore, by alternating between the first and second plurality of markers and the third and fourth plurality of markers, information related to the first optical property can be obtained for each field point using only two measurements. Similarly, information related to the second optical property can be obtained for each field point using only two measurements.

[0031] The imaging system may further include an additional plurality of markers, such as a fifth and a sixth plurality of markers, wherein the configuration of the fifth plurality of markers differs from the configuration of the first plurality of markers and the configuration of the third plurality of markers, and the configuration of the sixth plurality of markers is substantially matched with the configuration of the fifth plurality of markers.

[0032] The first plate may further include the third plurality of markers. The first plate may be further positioned such that the third plurality of markers are located within the first area. The second plate may further include the fourth plurality of markers. The second plate may be further positioned such that the fourth plurality of markers are located within the second area.

[0033] For example, each of the first and second plates may contain two sets of markers. By positioning the first and second plates differently within the first and second planes, the first and second plurality of markers can be used to determine the first and / or second optical properties, or the third and fourth plurality of markers can be used to determine the first and / or second optical properties. This device allows for easy alternation between different configurations of the markers by allowing relatively small positional changes in the first and second plates.

[0034] The imaging device may further include a third plate containing the third plurality of markers, the third plate being positioned in the first plane such that the third plurality of markers are located within the first region. Alternatively, the imaging device may further include a fourth plate containing the fourth plurality of markers, the fourth plate being positioned in the second plane such that the fourth plurality of markers are located within the second region.

[0035] That is, an additional set of plates can be provided to the imaging apparatus to provide an alternative configuration of markers. This apparatus can advantageously enable, for example, the replacement of a single plate when it is contaminated without replacing other plates.

[0036] In another example described herein, there is a lithography apparatus that includes the imaging apparatus as described above. The lithography apparatus further includes an illumination system operable to illuminate the first region with an illumination beam; and a projection system operable to form an image of the first region at the second region.

[0037] Lithography apparatuses can particularly benefit from simultaneously determining the first and second optical properties. For example, simultaneously determining the two optical properties allows for optimization of the lithography process without significant time loss, thereby increasing the output and / or improving the performance of the lithography process.

[0038] The lithography apparatus may use EUV radiation, meaning the illumination beam may contain EUV radiation. First and / or second types of markers may include markers operable to interact with EUV radiation. These markers may include reflective markers, such as reflective gratings. In one embodiment, markers provided at the magnification mask level (i.e., in the first plane) may be reflective, and markers provided at the substrate level (i.e., in the second plane) may be transmissive.

[0039] In another example described herein, there is a method for determining one or more optical properties of the imaging system described above. The method includes: positioning a first plate in the first plane such that the first plurality of markers are located within the first region; positioning a second plate in the second plane such that the second plurality of markers are located within the second region; illuminating the first region with an illumination beam; receiving radiation from the second plate using the detector; receiving from the detector a signal indicating the first optical property and / or the second optical property of the illumination beam; and determining the first optical property and / or the second optical property of the illumination beam based on the signal.

[0040] The determination of the first and / or second optical properties can be performed by a processor (e.g., a computer processor). The processor may be part of the imaging system or part of an external computing system.

[0041] In another example described herein, there is a plate for use in an imaging system to determine two optical properties of an illumination beam of the imaging system configured to illuminate an illumination area with the illumination beam. The plate includes a plurality of markers. A first subset of the plurality of markers includes markers for determining a first type of a first optical property of the illumination beam. A second subset of the plurality of markers includes markers for determining a second type of a second optical property of the illumination beam. The plurality of markers are located within a marker area of ​​the plate. This marker area substantially corresponds to the illumination area.

[0042] The plate can serve as a reference plate. That is, the plate can be used in the object plane of the imaging system. The plate can have specific applications in lithography apparatus. Specifically, the plate can be used as a reference plate at the magnification mask alignment point.

[0043] In some embodiments, the space between adjacent markers from a plurality of markers may be greater than the size of each of the plurality of markers.

[0044] The marker area roughly corresponds to the illumination area, meaning that the board can be positioned in a plane containing the illumination area such that the entire marker area is illuminated by a beam of light. The marker area and the illumination area have similar or identical size and shape. The marker area may have a similar size to but smaller than the illumination area; for example, the marker area may be a scaled-down version of the illumination area. The markers may be discrete markers disposed within the marker area of ​​the board.

[0045] This configuration enables the determination of the first and second optical properties of the illumination beam substantially simultaneously. That is, the illumination beam can illuminate multiple markers within the illumination area, and the first and second optical properties of the illumination beam can be determined without moving the plate or the illumination beam itself. This results in a considerable time saving compared to determining the first and second optical properties in two separate measurements.

[0046] The plate can be used with any of the imaging systems or lithography devices described above; for example, the plate can be used as a first plate and / or a second plate in the examples described above.

[0047] Each of the markers of this first type may contain a grating.

[0048] The use of a grating allows for the determination of one or more aberrations in an imaging system. These aberrations can be measured, for example, with reference to one or more orders of Reynolds aberrations. One of the optical properties to be determined can be related to the aberration; for example, the optical property may include an aberration map of a portion of the imaging system. For instance, the aberration map of the projection system of the imaging system can be determined.

[0049] Each of the markers of this second type may contain a pinhole.

[0050] The use of a pinhole allows for the determination of the angular distribution of the illumination beam within the illuminated area. This angular distribution can be referred to as the pupil shape. The angular distribution corresponds to the shape and / or intensity profile of the illumination beam in the pupil plane of the imaging system.

[0051] The marker area can be elongated. That is, the marker area has a size in both a first direction and a second direction, and the size of the marker area in the first direction can be larger than its size in the second direction. Similarly, the illumination area can comprise a similar elongated shape having a first direction and a second direction, wherein the size of the illumination area in the first direction is larger than its size in the second direction. Therefore, the size (of the marker area and / or the illumination area) in the first direction can be referred to as the longer dimension. Therefore, the size (of the marker area and / or the illumination area) in the second direction can be referred to as the shorter dimension. The shorter dimension can coincide with the scanning direction of the imaging system, and the longer dimension can coincide with the non-scanning direction of the imaging system. The plate can be positioned in the plane of the imaging system (i.e., the plane containing the illumination area) such that the shorter dimension of the marker area is substantially aligned with the shorter dimension of the illumination area, and the longer dimension of the marker area is substantially aligned with the longer dimension of the illumination area. The marker area can be curved or straight.

[0052] In some applications, such as lithography, the illumination area is elongated. Therefore, it is advantageous to arrange the markers in similarly elongated marker areas so that all markers can be illuminated simultaneously.

[0053] One of the plurality of markers, the first marker, may be located at or near a first end of the marker region. One of the plurality of markers, the second marker, may be located at or near a second end of the marker region, away from the first end. The other markers of the plurality of markers may be distributed between the first marker and the second marker.

[0054] The first and second ends of the elongated region can represent the distal ends of the elongated region at its longest dimension. By arranging the markers in this manner, the markers are substantially distributed across all marker areas. Thus, the set of field points distributed across substantially all illumination areas can be sampled. Advantageously, this makes it possible to determine two optical properties across substantially the entire illumination area.

[0055] The first marker, other markers, and the second marker may be distributed along a first direction (e.g., the direction of the longest dimension of the elongated region). That is, for an elongated marker region, multiple markers may be distributed approximately along the longer dimension of the elongated region.

[0056] The other plurality of markers may be distributed substantially evenly between the first marker and the second marker. That is, the distance between adjacent markers, for example, in the first direction, may be substantially equal.

[0057] Adjacent markers among the plurality of markers may alternate between markers of the first type and markers of the second type.

[0058] Multiple markers can be alternated between markers of a first type and markers of a second type along a first direction (e.g., the direction of the longest dimension of the elongated marker region). By alternating between different types of markers within a marker region, each type of marker can be distributed across virtually all marker regions. Advantageously, this makes it possible to determine two optical properties across virtually all illumination regions. It should be understood that since the illumination region has an infinite number of field points, not all field points are sampled, but rather the optical properties of virtually all illumination regions can be determined by interpolation (or other similar methods) between adjacent pairs of markers of the same type.

[0059] In another example described herein, there is a plate system for use in an imaging system to determine two optical properties of an illumination beam of the imaging system configured to illuminate an illumination area with the illumination beam. The plate system includes a first plate and a second plate, each according to the plates described above. On the first plate, a first subset of a plurality of markers is located at a set of first positions, and a second subset of the plurality of markers is located at a set of second positions. On the second plate, the first subset of the plurality of markers is located at a set of second positions, and the second subset of the plurality of markers is located at a set of first positions. The first positions of the first plate correspond to the first positions of the second plate, and the second positions of the first plate correspond to the second positions of the second plate.

[0060] This configuration can be referred to as a reciprocal, reciprocal, or complementary configuration. The plurality of markers on the first plate can be referred to as the first plurality of markers. The plurality of markers on the second plate can be referred to as the second plurality of markers. When using the first plate, it can be positioned in a plane containing the illumination area, such that the first plurality of markers are illuminated. Alternatively, the second plate can be positioned in a plane containing the illumination area, such that the second plurality of markers are illuminated. When using the first plate, a first set of field points corresponding to a set of first positions can be sampled relative to a first optical property, and a second set of field points corresponding to a set of second positions can be sampled relative to a second optical property. When using the second plate, a first set of field points corresponding to a set of first positions can be sampled relative to a second optical property, and a second set of field points corresponding to a set of second positions can be sampled relative to a first optical property. In this way, each optical property can be sampled at each position (i.e., including both the first and second positions) in only two measurements. This plate system enables the acquisition of a wealth of information about the optical properties of a high-frequency illumination beam. For example, two different optical properties corresponding to each field point at a first or second location can be detected by performing two measurements, the first using the first plate and the second using the second plate. Alternatively, the determination of two optical properties can be made in a single measurement (e.g., using a plurality of first or second markers in use), although this determination is less precise than that obtained through two measurements, but can be performed at an increased frequency.

[0061] This plate system offers the further benefit that if one plate (e.g., the first or second plate) is damaged or contaminated, the other plate can still be used to determine the two optical properties.

[0062] The first and second plates can be integrated. That is, the plate system can contain a single plate that includes both the first and second plurality of markers.

[0063] This plate system can be used with any of the imaging systems or lithography devices described above.

[0064] In another example described herein, there is a plate system for use in an imaging system to determine two optical properties of an illumination beam of the imaging system. The plate system includes a first plate, a second plate, and a third plate, each according to the plates described above. On the first plate, a first subset of the plurality of markers is located at a set of first positions, and a second subset of the plurality of markers is located at a set of second positions. The first plate further includes a set of third positions that do not contain markers. On the second plate, the first subset of the plurality of markers is located at a set of second positions, and the second subset of the plurality of markers is located at a set of third positions. The second plate further includes a set of first positions that do not contain markers. On the third plate, the first subset of the plurality of markers is located at a set of third positions, and the second subset of the plurality of markers is located at a set of first positions. The third plate further includes a set of second positions that do not contain markers. The first positions of the first plate correspond to the first positions of the second plate and the first positions of the third plate. The second positions of the first plate correspond to the second positions of the second plate and the second positions of the third plate. The third positions of the first plate correspond to the third positions of the second plate and the third positions of the third plate.

[0065] Within an EUV lithography apparatus, in the presence of EUV radiation from the illumination beam source, some parts of the apparatus may become contaminated. The portion of the apparatus at the substrate level may be particularly susceptible to this contamination. Markers at the photomask level, such as gratings and pinholes, allow the illumination beam to travel forward to the wafer level. Contamination of these markers at the substrate level can lead to reduced accuracy in determining aberrations and pupil shapes and / or may require cleaning and / or component replacement. By providing n boards, each board can be used 1 / n times, and some locations on the boards may be free of markers. This reduces the amount of contamination experienced by each wafer level marker.

[0066] By providing marker-free locations in a plate system as described herein, where these locations are unmarked on the first plate but have different types of markers on other plates, contamination can be reduced while still being able to determine the optical properties of the relevant field points (i.e., corresponding to the first, second, and third locations). Each time different plates from the three plates are used, one set of locations (i.e., the set of the first, second, or third locations) is shielded from contamination, while the other two sets of locations are sampled. This provides a beneficial trade-off between collecting information for determining optical properties and reducing contamination.

[0067] Areas without markers can be referred to as blank areas. This arrangement of Type I markers, Type II markers, and blank areas on different plates can be described as a reversible, inverse, or complementary arrangement.

[0068] In another example described herein, there is a plate system for use in an imaging system to determine an optical property of an illumination beam of the imaging system configured to illuminate an illumination area with the illumination beam. The plate system includes a first plate and a second plate. The first plate includes: a first plurality of markers for determining the optical property of the illumination beam, the first plurality of markers being located at a set of first positions; and a set of second positions not containing markers. The second plate includes: a second plurality of markers for determining the optical property of the illumination beam, the second plurality of markers being located at a set of second positions corresponding to the set of second positions of the first plate; and a set of first positions not containing markers. The set of first positions of the second plate corresponds to the set of first positions of the first plate. The first plurality of markers are located in a first marker area substantially corresponding to the illumination area. The second plurality of markers are located in a second marker area substantially corresponding to the illumination area.

[0069] Within EUV lithography apparatuses, parts of the apparatus may become contaminated, for example, in the presence of EUV radiation from the source of the illumination beam. Parts of the apparatus at the substrate level may be particularly susceptible to this contamination. Markers at the photomask level, such as gratings and pinholes, allow the illumination beam to travel forward to the wafer level. Contamination of these markers at the substrate level can lead to reduced accuracy in determining aberrations and pupil shapes and / or may require cleaning and / or component replacement. By providing boards in which some locations are free of markers, the amount of contamination experienced by each wafer level marker can be reduced.

[0070] By providing marker-free locations in a plate system as described herein, where these locations are unmarked on the first plate but have different types of markers on other plates, contamination can be reduced while still being able to determine the optical properties of the relevant field points (i.e., corresponding to the first and second locations). Each time a different plate is used, one set of locations (i.e., the set of the first or second locations) is shielded from contamination, while another set of locations is sampled. This provides a beneficial trade-off between collecting information for determining optical properties and reducing contamination.

[0071] Areas without markers can be referred to as blank areas. This arrangement of Type I markers, Type II markers, and blank areas on different plates can be described as a reversible, inverse, or complementary arrangement.

[0072] This plate system offers the further benefit that if one plate (e.g., the first or second plate) is damaged or contaminated, the other plate can still be used to determine optical properties.

[0073] The first and second plates can be integrated. That is, the plate system can contain a single plate that includes both the first and second plurality of markers.

[0074] The marker area roughly corresponds to the illumination area, meaning that the board can be positioned in a plane containing the illumination area such that the entire marker area is illuminated by a beam of light. The marker area and the illumination area have similar or identical size and shape. The marker area may have a similar size to but smaller than the illumination area; for example, the marker area may be a scaled-down version of the illumination area. The markers may be discrete markers disposed within the marker area of ​​the board.

[0075] This plate system can be used with any of the imaging systems or lithography devices described above.

[0076] In another example described herein, there is a stage for holding a 1x scaled mask. This stage comprises any of the plates or plate systems described above.

[0077] This plate or plate system can be used on a stage for a magnifying mask to determine one or more optical properties of the illumination beam of a portion (i.e., the illumination area) of the magnifying mask. Determining the optical properties of the illumination beam at the magnifying mask can be beneficial, for example, by performing corrections to improve the quality of the pattern imparted to the illumination beam by the magnifying mask. Corrections can be adjustments to the shape and / or intensity profile of the illumination beam. Corrections can also be adjustments to alter the aberration state of the illumination beam.

[0078] The plate or plate system can be mounted on a magnifying mask stage. The magnifying mask stage can be movable to move the plate or plate system into and out of the position where multiple markers are illuminated by the illumination beam.

[0079] The reduction mask stage can form part of any of the imaging systems or lithography apparatuses described above. The reduction mask stage can be positioned at the reduction mask alignment of this imaging system or lithography apparatus.

[0080] In another example described herein, there is a substrate stage for holding a substrate. The substrate stage includes any of the boards or board systems described above.

[0081] This plate or plate system can be used on a substrate stage to determine one or more optical properties of an illumination beam illuminating (and, where appropriate, patterning) a portion of the substrate. Determining the optical properties of the illumination beam at the substrate can be beneficial, for example, by performing corrections to improve the quality of the pattern illuminated on the substrate. Corrections can be adjustments to the shape and / or intensity profile of the illumination beam. Corrections can be adjustments to change the aberration state of the illumination beam. Corrections can be adjustments to one or more elements of a projection system configured to image from a first plane of the imaging system to a second plane of the imaging system.

[0082] The board can be mounted on a wafer stage. The wafer stage can be movable to allow the board to be moved in and out of positions where multiple markers are illuminated by an illumination beam.

[0083] The substrate stage can form part of any of the imaging systems or lithography apparatuses described above. The substrate stage can be positioned at the substrate alignment of this imaging system or lithography apparatus.

[0084] In another example described herein, there exists a detector that includes any of the boards or board systems described above.

[0085] The detector's plate portion can be configured such that when a marker on the plate or plate system is illuminated by an illumination beam, the detector can receive radiation from the plate and output a signal indicating one or more optical properties of the illumination beam. The detector's plate portion can be disposed in a second plane, and the detector's radiation receiving portion can be disposed in a third plane. The second and third planes can be parallel. Depending on the situation, the detector may include optics configured to guide radiation from the second plane to the third plane. Simple Explanation of the Diagram

[0086] The present invention will now be described with reference only to the accompanying drawings, in which: - Figure 1 shows a lithography system including a lithography device and a radiation source; Figure 2 depicts the imaging system; Figure 3 depicts an example configuration of markers on two boards; Figure 4 depicts a plate system that can be used in an imaging system to determine two optical properties of the illumination beam of the imaging system; Figure 5 depicts a plate system that can be used in an imaging system to determine the optical properties of the illumination beam of the imaging system; Figure 6 depicts a plate system that can be used in an imaging system to determine two optical properties of the illumination beam of the imaging system; Figure 7 depicts an example configuration of markers on two boards; and - Figure 8 shows an alternative configuration of the markers on the drawing board.

[0087] These diagrams are schematic in nature and are not drawn to scale. Implementation

[0088] Figure 1 illustrates a lithography system including a radiation source SO and a lithography device LA. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography device LA. The radiation beam B may be referred to as an illumination beam. The lithography device LA includes an illumination system IL, a support structure MT configured to support a patterned device MA (e.g., a mask), a projection system PS, and a substrate stage WT configured to support a substrate W. The patterned device MA may be referred to as a magnification mask. The support structure MT is configured to hold the magnification mask MA in a magnification mask plane 100 of the lithography device LA. The magnification mask plane 100 may be referred to as the object plane of the lithography device LA. The magnification mask plane 100 may be referred to as being at a magnification mask level. The substrate stage WT is configured to hold a substrate W in a substrate plane 102 of the lithography device LA. The substrate plane 102 may be referred to as the image plane of the lithography device LA. The substrate plane 102 may be referred to as being at a substrate level. The projection system PS is configured to form an image of one of the objects in the magnifying mask plane 100 in the substrate plane 102. Therefore, the magnifying mask plane 100 and the substrate plane 102 can be referred to as conjugate planes. The magnifying mask level (and its components, such as the support structure MT), the substrate level (and its components, such as the substrate stage WT), and the projection system PS can be considered to form an imaging system. The imaging system uses radiation imaging from the illumination system IL. Therefore, the illumination system IL can also be said to include a portion of the imaging system.

[0089] Detector D is located on substrate stage WT. The detector is positioned in another plane such that it is operable to receive radiation from substrate plane 102 during aberration or pupil measurement. In Figure 1, detector D is positioned below substrate plane 102 such that it can receive radiation from a transmission element (e.g., a transmission grating or pinhole) held in substrate plane 102 by substrate stage WT.

[0090] The illumination system IL is configured to adjust the EUV radiation beam B before it is incident on the patterning device MA. Additionally, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. Together, the faceted field mirror device 10 and the faceted pupil mirror device 11 provide the EUV radiation beam B with a desired cross-sectional shape, a desired intensity distribution, and a desired angular distribution. The angular distribution of the radiation beam B can be described by an intensity distribution in the pupil plane and may be referred to as a pupil shape. In addition to or in place of the faceted field mirror device 10 and the faceted pupil mirror device 11, the illumination system IL may include other mirrors or devices. For example, one or more blades (not shown) may be used to provide a cross-sectional shape for the radiation beam B. The blades may be operated by intersecting the radiation beam B before the patterning device, wherein the position of the blades changes the cross-sectional shape of the radiation beam B. The blades may be movable, allowing controllable overlap between the blades and the radiation beam B. Therefore, the radiation beam illuminates a region of the magnifying mask plane 100, the shape of which depends on the shape of the radiation beam B. The region on the magnifying mask plane 100 illuminated by the radiation beam B (e.g., the region of the patterned device MA) can be referred to as an illumination region.

[0091] After such adjustment, the EUV radiation beam B interacts with the patterning device MA. This interaction generates a patterned EUV radiation beam B'. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. That is, the projection system PS forms an image of an object disposed in the magnification mask plane 100 on the substrate plane 102, and by positioning the patterning device MA in the magnification mask plane 100 and the substrate W in the substrate plane, the projection system PS can be used to form an image of the magnification mask MT on the substrate W. For this purpose, the projection system PS may include a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate stage WT. The area on the substrate plane 102 where the patterned EUV radiation beam B' is projected (e.g., the area of ​​the substrate W) may be referred to as the illumination area.

[0092] The projection system PS can apply a reduction factor to the patterned EUV radiation beam B', thus forming an image with features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 can be applied. Thus, the illumination area on the magnification mask plane 100 can be a scaled version of the illumination area on the substrate plane 102 (e.g., scaled by a reduction factor of, for example, 4 or 8). Alternatively, for example, if the projection system PS does not apply a reduction factor, the illumination area on the magnification mask plane 100 can be equivalent in size and shape to the illumination area on the substrate plane 102. Although the projection system PS is illustrated in FIG. 1 as having only two mirrors 13, 14, the projection system PS can include a different number of mirrors (e.g., six or eight mirrors).

[0093] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure far below atmospheric pressure, can be provided in the radiation source SO, the lighting system IL, and / or the projection system PS. The radiation source SO can be a laser-generated plasma (LPP) source, a discharge-generated plasma (DPP) source, a free electron laser (FEL), or any other radiation source capable of generating EUV radiation.

[0094] Generally, a projection system PS has a potentially non-uniform optical transfer function, which can affect the pattern imaged on a substrate W. For unpolarized radiation, such effects can be well described by two scalar maps that describe the transmission (apodization) and relative phase (aberration) of the radiation, which vary depending on the position of the radiation exiting the projection system PS in the pupil plane. These scalar maps can be referred to as transmission maps and aberration maps. Transmission and aberration are examples of the optical properties of a radiation beam B (or a patterned radiation beam B') induced by the projection system PS.

[0095] Transmission and aberration maps are expressed as a linear combination of the entire set of basis functions. A particularly suitable set is the Zernike polynomial, which forms a set of orthogonal polynomials defined on the unit circle. Determining each scalar map may involve determining the coefficients in this expansion. Each Zernike coefficient relates to different types of aberrations, such as tilt (in the x and y directions), astigmatism, coma, spherical aberration, etc. Determining aberrations (which may be caused by the projection system or by placement errors of the patterning device or substrate) may involve fitting measurements of the Zernike polynomials by a detector to obtain the Zernike coefficients. Different Zernike coefficients can provide information about different forms of aberrations caused by the projection system. It should be understood that, in alternative embodiments, other sets of basis functions may be used. For example, for masked aperture systems, some embodiments may use Tatian Zernike polynomials.

[0096] An aberration map represents the distortion of the wavefront of light from a point on the image plane of the projection system PS (i.e., substrate plane 102) approaching the projection system PS from a spherical wavefront (based on the position on the pupil plane, or alternatively, based on the angle at which the radiation approaches the image plane of the projection system PS). Throughout this specification, the term "aberration" is intended to include all forms of deviation of the wavefront from a perfect spherical wavefront. Furthermore, any reference to an aberration map used for a projection system may include all forms of deviation of the wavefront from a perfect spherical wavefront, including deviations due to image placement.

[0097] Transmission maps and aberration maps are field- and system-dependent. That is, generally speaking, each projection system PS will have a different Renekton expansion for each field point (that is, for each spatial location in the image plane of the projection system PS, such as the substrate plane 102).

[0098] The projection system PS includes a plurality of optical elements (including mirrors 13, 14). As explained, although the projection system PS is illustrated in Figure 1 as having only two mirrors 13, 14, the projection system PS may include a different number of mirrors (e.g., six or eight mirrors). The lithography device LA may further include an adjustment member for adjusting these optical elements to correct aberrations (any type of phase change across the pupil plane of the field) after aberrations have been determined (e.g., by determining an aberration map). To achieve this correction, the adjustment member PA is operable to manipulate the optical elements within the projection system PS in one or more different ways. The adjustment member PA is operable to perform any combination of the following: displacing one or more optical elements; tilting one or more optical elements; and / or deforming one or more optical elements. The deformation of the optical elements may be performed, for example, by using an actuator to apply force to the side of the optical element and / or by using a heating element to heat a selected area of ​​the optical element.

[0099] The aberration map of the projection system PS in its pupil plane can be determined by projecting the radiation of an object from the magnifying mask plane 100 of the projection system PS through the projection system PS and using shear interferometry to measure the wavefront (i.e., the trajectory of points with the same phase). A first diffraction grating (e.g., a one-dimensional reflection grating) is placed in the illumination area of ​​the magnifying mask plane 100 and illuminated by a radiation beam B. This causes the radiation beam B to diffract in the shear direction into a plurality of diffraction orders, which are at least partially captured by the projection system PS. A second diffraction grating (e.g., a transmission two-dimensional checkerboard or pinhole array grating) is placed in the illumination area of ​​the substrate plane 102. The projection system forms an image of the first diffraction grating (in the magnifying mask plane 100) on the second diffraction grating (in the substrate plane 102).

[0100] Detector D is positioned to receive radiation from substrate plane 102 (i.e., detector D receives radiation from a diffraction grating positioned in substrate plane 102). Detector D outputs a signal indicating the wavefront. From this signal, an aberration map can be derived using any known method (e.g., using Renekton coefficients as described above). The aberration map can be derived computationally on a processor (e.g., on a computer associated with the lithography device).

[0101] Match the distance between the first and second diffraction gratings (considering any reduction factors in the PS projection system application). That is, considering any reduction factor, the distance between the first and second diffraction gratings in the shear direction can be equal. This matching of the distances results in the spatial overlap of coherent rays from the radiation beam B, which produces an interference pattern in the plane of detector D.

[0102] The first and second diffraction gratings scan or step relative to each other in the shear direction, thereby causing oscillations in the interference signal. The first and / or second diffraction gratings can be stepped to a distance corresponding to a fraction of the grating period of the diffraction grating. Measurements taken at different step positions can be analyzed to derive information about the wavefront in the step direction. For example, the phase of the first harmonic of the measured signal (which may be referred to as the phase-stepped signal) may contain information about the derivative of the wavefront in the step direction. Measurements can be taken using two mutually orthogonal shear directions, which allows information about the wavefront to be derived in two perpendicular directions (specifically, it provides information about the derivative of the wavefront in each of the two perpendicular directions), thereby allowing the reconstruction of the complete wavefront.

[0103] The pupil shape (i.e., the angular distribution of the radiation beam B in the pupil plane) can be determined as follows: A pinhole is positioned in the illumination area of ​​the magnifying mask plane 100. A pinhole is also positioned in the corresponding illumination area of ​​the substrate plane 102, such that the projection system PS generates an image of the pinhole in the magnifying mask plane 100 at the pinhole in the substrate plane 102. The two pinholes are illuminated by illuminating the illumination area of ​​the magnifying mask plane 100 using the radiation beam B of the illumination system IL. A detector D is positioned to receive radiation from the substrate plane 102 (i.e., the detector D receives radiation from the pinhole positioned in the substrate plane 102). The detector D outputs a signal indicating the angular distribution of the radiation beam B in the pupil plane. From this signal, the pupil shape can be determined using any known method. The pupil shape can be derived using computational methods on a processor (e.g., on a computer associated with the lithography device).

[0104] Figure 2 illustrates the imaging system 20. The imaging system 20 may represent a portion of the lithography apparatus LA of Figure 1. The imaging system 20 includes an illumination system 22, which may be of the same type as the illumination system IL depicted in Figure 1. The illumination system 22 is operable to generate an illumination beam 21 and illuminate a portion of a first plane 200 of the imaging system 20. The illuminated portion of the first plane 200 may be referred to as the illumination area. The first plane 200 may be exemplified by the magnification mask plane 100 of Figure 1. The imaging system 20 further includes a projection system 24, operable to form an image of an object placed in the first plane 200 in a second plane 202. The area where the image is formed may be referred to as the illumination area, provided that this area receives radiation from the illumination beam 21. The second plane 202 may be exemplified by the substrate plane 102 of Figure 1. The imaging system 20 further includes a detector 29, which can receive radiation from the second plane. The detector 29 is disposed in a third plane 204, which may be conjugate to the pupil plane of the projection system 24. That is, the detector 29 can detect the pattern in the illumination beam 21 at the pupil plane (or the plane associated with it) of the projection system 24 (e.g., the angular distribution or interference pattern indicating the aberration map).

[0105] The imaging system further includes a first plate 26 and a second plate 28. The first plate 26 can be positioned in a first plane 200, for example on a support structure (not shown). A support structure such as the support structure MT shown in FIG. 1 can be used. The first plate 26 has a plurality of markers 210, 220 disposed in an area of ​​the first plate 26. The first plate 26 can be positioned in the first plane 200 such that all the plurality of markers 210, 220 are illuminated by the illumination beam 21. That is, the plurality of markers 210, 220 are arranged such that the plurality of markers 210, 220 can be positioned in the illumination area of ​​the first plane 200. Similarly, the second plate 28 includes a plurality of markers 211, 221 disposed in an area of ​​the plate 28. The second plate 28 can be positioned in a second plane 202 such that all the plurality of markers 211, 221 are illuminated by the illumination beam 21. That is, a plurality of markers 211 and 221 are arranged in such a way that the plurality of markers 211 and 221 can be positioned in the illumination area of ​​the second plane 200.

[0106] The first plate 26 has a first subset of markers 210, each of which contains a marker of a first type. These first-type markers are configured to determine a first optical property of the illumination beam. For example, the first-type markers may be diffraction gratings and can be used to determine aberration maps. The first plate 26 has a second subset of markers 220, each of which contains a marker of a second type. The second-type markers are configured to determine a second optical property of the illumination beam. For example, the second-type markers may be pinholes and can be used to determine the pupil shape of the illumination beam. Similarly, the second plate 28 has: a first subset of markers 211, each of which contains the same first-type markers; and a second subset of markers 221, each of which contains the same second-type markers. The plurality of markers 210, 220 on the first plate 26 may be referred to as the first plurality of markers 210, 220. The plurality of markers 211 and 221 on the second plate 28 can be referred to as the second plurality of markers 211 and 221.

[0107] The arrangement of the second plurality of markers 211, 221 on the second plate 28 substantially matches the arrangement of the first markers 210, 220 on the first plate 26. Therefore, when the plates are in the appropriate position and illuminated, each marker on the first plate 26 (e.g., a marker of the first type) is imaged onto a corresponding marker on the second plate 28 (e.g., a marker corresponding to the first type). This arrangement can be referred to as a conjugate arrangement because the image of each of the markers is formed on a corresponding marker of the same type in a conjugate plane.

[0108] When the plates are positioned as described above, detector 29 receives radiation that interacts with a pair of markers of the same type. For example, a portion of the illumination beam 21 interacts with a first type of marker in the first plate 26 and a first type of marker in the second plate 28 before being received by detector 29. Different portions of the illumination beam 21 interact with a second type of marker in the first plate 26 and a second type of marker in the second plate 28 before being received by detector 29. Thus, detector 29 receives radiation containing information related to the first and second optical properties. Detector 29 can output this signal indicating the first and / or second optical properties, which can be transmitted, for example, to a computer processor to determine these optical properties.

[0109] The use of an imaging system and plates 26, 28, as shown in Figure 2, enables the substantial simultaneous determination of two different optical properties. This is because the illumination beam 21 of the illumination system 22 can substantially simultaneously illuminate the first plurality of markers 210, 220 in the first plane 200 and the second plurality of markers 211, 221 in the second plane 202, without the need to move plates 26, 28 or the illumination beam 21. This contrasts with previous systems where a single plate could be used to determine the first and second optical properties, or where significant movement of the plate or illumination beam was required to switch between a first type of measurement detecting the first optical property and a second type of measurement determining the second type of optical property. Using the configuration described herein, two optical properties can be determined in a single measurement. This results in significant time savings, which may be particularly beneficial when used in conjunction with lithography apparatuses, where throughput is especially important and any time savings are particularly advantageous.

[0110] It should be noted that the illumination beam 21 in Figure 2 is schematic in nature and may have different shapes and / or paths in actual imaging systems. For example, the illumination beam 21 may diverge and / or focus one or more times along the path between the illumination system 22 and the detector 29. Furthermore, the illumination beam 21 is shown traveling through each plate 26, 28, indicating the transmission markers 210, 220, 211, 221 (i.e., markers that allow at least a portion of the illumination beam 21 to propagate). However, in other configurations and embodiments, reflective markers (i.e., markers that reflect at least a portion of the illumination beam 21) may be used.

[0111] Figure 3 depicts an example configuration of markers on the two plates 36 and 38. The first plate 36 can be used to replace the first plate 26 of Figure 2, that is, the first plate 36 can be positioned in the first plane of the imaging system. The second plate 38 can be used to replace the second plate 28 of Figure 2, that is, the second plate 38 can be positioned in the second plane of the imaging system.

[0112] The first plate 36 contains a first plurality of markers 310, 320. Similar to the markers described with reference to FIG. 2, a first subset 310 of the first plurality of markers contains markers of a first type, and a second subset 320 of the first plurality of markers contains markers of a second type. The first plurality of markers 310, 320 are disposed within a marker area 31. The marker area 31 is simply the area of ​​plate 36 containing all the first plurality of markers 310, 320. The marker area 31 is depicted in FIG. 3 with a solid line defining the marker area 31. However, the marker area 31 is essentially indicative and does not need to take any physical form.

[0113] The illumination area 32 is also depicted as a dashed line in Figure 3. Illumination area 32 indicates the area of ​​the first plate 36 that can be illuminated by the illumination beam of the illumination system (e.g., beam 21 generated by the illumination system 22 of the imaging system in Figure 2). Specifically, illumination area 32 indicates the area of ​​the first plate 36 that can be illuminated when the first plate 36 is positioned within the illumination area of ​​the first plane of the imaging system. It should be understood that because the first plate 36 can move within the first plane, for example, in the nominal x and y directions indicated in Figure 3, illumination area 32 can move correspondingly in the x and y directions relative to the first plate 36 and the plurality of markers 310, 320 on it. However, the size and shape of illumination area 32 remain constant as the first plate 36 moves within the first plane. Marker area 31 roughly corresponds to illumination area 32. They may have similar size and shape. In the example depicted in Figure 3, the marker area 31 has the same shape but a smaller size compared to the illumination area 32; that is, the marker area 31 is a (smaller) scaled-down version of the illumination area 32. In other configurations, the marker area 31 and the illumination area 32 may have the same shape and size. In an alternative configuration, the marker area 31 may have a different shape than the illumination area 32, but the shape and size are set such that the marker area 31 is completely contained within the illumination area 32. Due to the correspondence between the marker area 31 and the illumination area 32, it is possible to position a plurality of markers 310, 320 such that the entire marker area (and therefore all markers 310, 320) is illuminated by the illumination beam. Since two different types of markers (the first subset 310 and the second subset 320) are illuminated simultaneously, the two different optical properties of the illumination beam can be determined substantially simultaneously.

[0114] As can be seen, the marker area 31 and illumination area 32 of the first plate 36 are elongated. That is, the size of the marker area 31 in the first direction (x-direction) is longer than its size in the second direction (y-direction). The size in the first direction can be referred to as the longer direction, and the size in the second direction can be referred to as the shorter direction. In addition, the marker area 31 is curved along the longer direction. In some lithography apparatuses, such as the lithography apparatus LA shown in FIG. 1, which has a generally elongated and curved illumination area, the marker configuration depicted in FIG. 3 may be particularly advantageous for use on this lithography apparatus. The shorter dimension of the elongated area may coincide with the scanning direction of the lithography apparatus or imaging system, and the longer dimension of the elongated area may coincide with the non-scanning direction of the lithography apparatus or imaging system. However, it should be understood that marker areas of any size and shape may be used depending on the specific imaging system to be used with the plate.

[0115] The first plurality of markers 310, 320 can be arranged in any manner within the marker area 31. In the depicted example, the first plurality of markers 310, 320 are distributed across substantially all marker areas 31. That is, the first marker 330 of the first plurality of markers 310, 320 is located at a first end of the marker area 31, and the second marker 340 of the first plurality of markers 310, 320 is located at a second end of the marker area 31, away from the first end. It can be claimed that the first marker 330 and the second marker 340 are located at opposite ends of an elongated region containing the marker area 31. The other markers of the first plurality of markers 310, 320 are distributed between the first marker 330 and the second marker 340. By arranging the markers in this manner, the markers are substantially distributed across all marker areas 31, and thus, a set of field points substantially distributed across all illumination areas 32 can be sampled. This allows for determination of optical properties over substantially the entire illumination area 31. In the depicted example, a plurality of markers 310, 320 are distributed substantially evenly between the first marker 330 and the second marker 340. However, it should be understood that different configurations are also possible.

[0116] The first plurality of markers 310, 320 depicted in Figure 3 also alternate between markers of the first type and markers of the second type. By alternating between different types of markers within marker area 31, each type of marker can be distributed across virtually all marker areas, making it possible to determine each optical property across virtually all illumination areas 31. It can be seen that in the configuration of Figure 3, the first optical property can be determined across virtually the entire illumination area 32 (using markers of the first type, i.e., the first subset 310 of the markers), but the second optical property is determined over a shorter range in the x-direction (using markers of the second type, i.e., the second subset 320 of the markers). However, by alternating between markers, a considerable portion of the illumination area 32 is still sampled relative to the second optical property. This is advantageous compared to having clusters of markers of the first type in the first area of ​​marker area 31 and clusters of markers of the second type in the second area of ​​marker area 31.

[0117] The second plate 38 includes a second plurality of markers 311 and 321. A first subset 311 of the second plurality of markers includes markers of a first type and a second subset 321 of the second plurality of markers includes markers of a second type. The second plurality of markers 311 and 321 are disposed in a marker area 33 that generally corresponds to the lighting area 34.

[0118] The arrangement of the second plurality of markers 311, 321 roughly matches the arrangement of the first plurality of markers 310, 320 of the first plate 36. Specifically, the spatial arrangement of the first type 310 and the second type 320 markers 310, 320 in the first plurality of markers 310, 320 (on the longer dimension of the marker area 31) is the same as the spatial arrangement of the first type 311 and the second type 321 markers 311, 321 in the second plurality of markers 311, 321 (on the longer dimension of the marker area 34).

[0119] Illumination area 34 indicates the area of ​​the second plate 38 that can be illuminated by the illumination beam of the illumination system (e.g., beam 21 generated by the illumination system 22 of the imaging system in FIG. 2). Specifically, illumination area 32 indicates the area of ​​the second plate 38 that can be illuminated when the second plate 36 is positioned in the illumination area of ​​the second plane of the imaging system. As described above with respect to illumination area 32 of the first plate 36, because the second plate 38 can move within the second plane, illumination area 34 can move correspondingly relative to the second plate 38 and the plurality of markers 311, 321 on it. However, when the second plate 38 moves within the first plane, the size and shape of illumination area 33 will remain constant. Compared to illumination area 32 and marker area 31 of the first plate 31, illumination area 34 and marker area 33 of the second plate 38 have the same shape but are smaller in size. This is because the plates 36, 38 depicted in FIG. 3 are projection systems used for applying reduction factors.

[0120] The first and second types of markers on the second plate 38 are arranged in the marker area 33 in a manner that matches the arrangement of the first and second types of markers in the marker area 31 of the first plate 36. For example, the first marker 350 is located at the first end of the marker area 33, the second marker 360 is located at the second end of the marker area 33 away from the first end, and other markers are distributed between the first marker 350 and the second marker 360 in an alternating manner between the first type of markers and the second type of markers. Because the marker area 33 of the second plate 38 is a scaled version of the marker area 31 of the first plate 36, the arrangement of the second plurality of markers 311, 321 is scaled accordingly relative to the arrangement of the first plurality of markers 310, 320. Because the markers on the first plate 36 and the second plate 38 are configured to match, when the first plate 36 and the second plate 38 are positioned in the first and second planes of the imaging system and are illuminated, the image of each of the first type of markers on the first plate 36 is formed on the corresponding first type of marker on the second plate 38.

[0121] In the above discussion, the first subset 310 of the first plurality of markers on the first plate 36 and the first subset 311 of the second plurality of markers on the second plate 38 are both described as markers containing the first type. Similarly, in Figure 3, the first subset 310 of the first plurality of markers on the first plate 36 and the first subset 311 of the second plurality of markers on the second plate 38 are schematically shown using similar symbols. However, those skilled in the art will understand that, generally speaking, the first subset 310 of the first plurality of markers on the first plate 36 and the first subset 311 of the second plurality of markers on the second plate 38 are not the same. For example, the first subset 310 of the first plurality of markers on the first plate 36 may be in the form of a one-dimensional reflective grating; and the first subset 311 of the second plurality of markers on the second plate 38 may be in the form of a transmissive two-dimensional checkerboard or pinhole array grating.

[0122] Figure 4 depicts a plate system 40 that can be used in an imaging system (such as imaging system 20 of Figure 2) to determine two optical properties of the illumination beam of the imaging system. The plate system 40 includes a first plate 46 and a second plate 48.

[0123] The first plate 46 has a first plurality of markers 410 and 420. A first subset 410 of the first plurality of markers 410 and 420 is a first type of marker configured to determine a first optical property of the illumination beam. A second subset 420 of the first plurality of markers 410 and 420 is a second type of marker configured to determine a second optical property of the illumination beam. The first subset 410 of the markers is located at a first location and the second subset 420 of the markers is located at a second location. Similar to the configuration depicted in FIG3, the markers 410 and 420 alternate between the first type of markers and the second type of markers along the longer dimension of the elongated marker area where the markers 410 and 420 are located.

[0124] The second plate 48 of the plate system 40 has a second plurality of markers 430 and 440. A first subset 430 of the second plurality of markers 430 and 440 includes markers of the same first type as the first subset 410 of the markers on the first plate 46. A second subset 440 of the second plurality of markers 430 and 440 includes markers of the same second type as the second subset 420 of the markers on the first plate 46. The second plurality of markers 430 and 440 on the second plate 48 are located at a set of positions that substantially correspond to the sets of first and second positions on the first plate 46. That is, each position in the set of positions on the second plate 48 where one of the second plurality of markers 430 and 440 is placed corresponds to the position of one of the first plurality of markers 410 and 420 on the first plate 46. However, the first subset 430 of the markers on the second plate 48 is located at the set of second positions corresponding to the set of second positions on the first plate 46. Correspondingly, the second subset 440 of the markers on the second plate 48 is located at the set of first positions corresponding to the set of first positions on the first plate 46. That is, for each position on the first plate 46 where a marker of the first type is found, the corresponding position on the second plate 48 contains a marker of the second type, and for each position on the first plate 46 where a marker of the second type is found, the corresponding position on the second plate 48 contains a marker of the first type. The arrangement of the first and second types of markers on the two plates 46 and 48 can be referred to as a complementary arrangement or a reversible arrangement.

[0125] In use, the plate system 40 is configured for use as a single level of the imaging system. For example, the plate system 40 can be used in a magnification mask level of the imaging system (i.e., each plate can be interchangeably positioned in a magnification mask plane or an object plane). Although described below as being used in a single level of the imaging system (e.g., at a magnification mask level), it will be understood that the plate system 40 can typically be used in conjunction with another substantially matching plate system provided at another level of the imaging system (e.g., at a substrate level) to determine one or more optical properties of the illumination beam. Each plate 46, 48 can be used to perform a single measurement set and perform determinations of the first and second optical properties of the illumination beam. Thus, the interchangeable use of each plate 46, 48 enables two measurement sets, each using different marker configurations on the plate, and each measurement set allows for multiple determinations of the first and second optical properties.

[0126] For the first measurement procedure (or the first measurement set), the first plate 46 can be inserted into the magnifying glass plane, such that the first plurality of markers 410, 420 are illuminated by the illumination beam. In this configuration, a first set of field points corresponding to the first set of positions (i.e., the positions of the first subset 410 of markers) is sampled to determine a first optical property, and a second set of field points corresponding to the second set of positions (i.e., the positions of the second subset 420 of markers) is sampled to determine a second optical property. For the second measurement procedure (or the first measurement set), alternatively, the second plate 48 can be inserted into the magnifying glass plane, such that the second plurality of markers 430, 440 are illuminated by the illumination beam. In this configuration, a first set of field points corresponding to the first set of positions (i.e., the positions of the second subset 440 of the markers) is sampled to determine the second optical property, and a second set of field points corresponding to the second set of positions (i.e., the positions of the first subset 430 of the markers) is sampled to determine the first optical property. In this way, by using two plates 46 and 48 to perform two sets of measurements, each optical property can be sampled at each field position corresponding to the position of the marker (i.e., the set including the first and second positions) in two measurements.

[0127] Using only the first plate 46 or only the second plate 48 as a single measurement set may result in lower accuracy in determining the first and second optical properties, because only a subset of field points is sampled to determine each optical property. By using two measurement sets sequentially, using the first plate 46 and the second plate 48, a more accurate determination of the first and second optical properties for each field is obtained because each optical property is sampled at each field point in both measurement sets. It has been found that acceptable imaging performance can be achieved by sampling each field point with every two measurement sets. This plate system 40 enables information about the first and second optical properties to be obtained at an increased frequency (i.e., for each measurement in each measurement set) and enables higher accuracy determinations at a relatively high frequency (for each other measurement set).

[0128] The plate system 40 provides an additional benefit: if one of the plates 46 and 48 is damaged or contaminated, the other plate 46 or 48 can continue to be used to determine the first and second optical properties without the need to remove, clean, or replace any components. This increases the uptime of the imaging system and correspondingly leads to higher output of lithography devices incorporating the imaging system.

[0129] The plate system 40 depicted in Figure 4 has two separate plates 46 and 48. However, in an alternative embodiment, a single plate may be used, comprising a first and a second plurality of markers 410, 420, 430, and 440. That is, plates 46 and 48 may be integral. In this embodiment, the single plate may be positioned in a plane such that the first plurality of markers 410, 420 or the second plurality of markers 430, 440 are illuminated by an illumination beam.

[0130] Alternatively, one or both of plates 46 and 48 may form part of a patterned device (e.g., the patterned device MA of FIG1). In this embodiment, the patterned device may have a central region containing a pattern to be imaged by the lithography device, and a plurality of markers 410, 420, 430, 440 may be disposed at the edge region of the patterned device.

[0131] The plate system 40, as described above, can be positioned in a first (e.g., a magnifying mask) plane of the imaging system. However, it should be understood that the plate system 40 can also be used in a second (e.g., a wafer) plane of the imaging system. When this plate system 40 is used for wafer alignment in the imaging system, one or more of the plates 46, 48 can form a portion of a substrate stage (e.g., substrate stage WT of FIG. 1). Alternatively, one or more of the plates 46, 48 can form a portion of a detector (e.g., detector D of FIG. 1 or detector 29 of FIG. 2) and can be attached to the detector, for example. In this embodiment, one or more of the plates 46, 48 can be positioned such that when illuminated by an illumination beam, radiation from those plates 46, 48 (e.g., radiation interacting with a marker) is received by a radiation receiving portion of the detector.

[0132] Another plate system may include the plate system 40 of FIG. 4 in a first plane for the imaging system, and additionally include third and fourth plates in a second plane for the imaging system. In this alternative plate system, the third and fourth plates substantially match the first plate 46 and the second plate 48 (i.e., for example, the arrangement of markers on the third plate substantially matches the arrangement of markers on the first plate 46, and the markers on the fourth plate are arranged in a reversible manner relative to the third plate, such that the arrangement of markers on the fourth plate substantially matches the arrangement of markers on the second plate 48). For example, the spatial order of the first plurality of markers 410 and the second plurality of markers 420 on the first plate 46 (on the longer dimension of the first plate 46) may be the same as the spatial order of the first plurality of markers and the second plurality of markers on the third plate (on the longer dimension of the third plate). Similarly, the spatial arrangement of the first plurality of markers 430 and the second plurality of markers 440 on the second plate 48 (on the longer dimension of the second plate 48) can be the same as the spatial arrangement of the first plurality of markers and the second plurality of markers on the fourth plate (on the longer dimension of the fourth plate).

[0133] The third and fourth plates are substantially matched with the first plate 46 and the second plate 48, in a manner similar to the substantially matched configuration of the second plurality of markers 311, 321 of the second plate 38 and the first plurality of markers 310, 320 of the first plate 36 in Figure 3. In use, the plate system 40 of Figure 4 can be configured in the first plane, alternating between the first plate 46 and the second plate 48 for each measurement, while the additional plate system can be configured in the second plane, correspondingly alternating between the third and fourth plates. In this other plate system, the first and second plates can actually be integrated, and the third and fourth plates can be additionally or alternatively integrated.

[0134] Figure 5 depicts a plate system 50 that can be used in an imaging system (such as imaging system 20 of Figure 2) to determine the optical properties of the illumination beam of the imaging system. The plate system includes a first plate 56 and a second plate 58.

[0135] The first plate 56 has a first plurality of markers 510, which are first type of markers configured to determine a first optical property of the illumination beam. Figure 5 schematically depicts the first plurality of markers 510 as a grating configured to determine an aberration map. However, any other type of marker may be selected to determine the optical property. The first plurality of markers 510 are located at a first position on the first plate 56.

[0136] The first plate 56 has an area at the set of second positions that does not contain the marker 530. That is, at the defined set of second positions, the plate does not contain the marker and is essentially blank. The body located at each second position or its absence may be referred to as the blank area 530.

[0137] The first plurality of markers 510 and blank areas 530 of the first plate 56 are disposed in a marker area (not shown), which generally corresponds to the illumination area of ​​the imaging system. Specifically, in the depicted configuration, the sets of first positions and the sets of second positions are equidistantly spaced along the elongated, curved marker area, and alternate between markers of the first type and blank areas. It should be understood that different configurations of the markers and marker areas are possible in other embodiments (e.g., using different imaging systems and / or different illumination areas).

[0138] The second plate 58 has markers 511 and blank areas 531 arranged in a reversible manner relative to the first plate 56. That is, the second plate 58 has a second plurality of markers 511 at a second set of positions, where the second set of positions of the second plate 58 corresponds to the second set of positions of the first plate 56. In other words, the second plate 58 contains markers 511 in the defined set of positions of the first plate 56 where the blank area 530 is located. Furthermore, the second plate 58 has areas at the first set of positions that do not contain markers 531, where the first set of positions of the second plate 58 corresponds to the first set of positions of the first plate 56. In other words, the second plate 58 does not contain markers in the defined set of positions of the first plate 56 where markers 510 are located. The areas that do not contain markers may be referred to as blank areas 531. The second plurality of markers 511 are markers of the same type as the first plurality of markers 510 of the first plate 56. The blank area 531 on the second plate 58 is equivalent to the blank area 530 on the first plate 56. Since the first and second positions of the first plate 56 and the second plate 58 are equal, the marker 511 and the blank area 531 on the second plate 58 are arranged in the marker area that roughly corresponds to the illumination area of ​​the imaging system.

[0139] In use, the plate system 50 is configured for use as a single level in the imaging system. For example, the plate system 50 can be used in a magnification mask level of the imaging system (i.e., each plate is interchangeably positioned in the magnification mask plane). Although described below as being used in a single level (e.g., at a magnification mask level) of the imaging system, it will be understood that the plate system 50 can typically be used in conjunction with another substantially matching plate system provided at another level (e.g., at a substrate level) of the imaging system to determine one or more optical properties of the illumination beam. Each plate 56, 58 can be used to perform a single measurement set and perform the determination of the optical properties of the illumination beam. Thus, the interchangeable use of each plate 56, 58 enables two measurement sets, each using different marker configurations on the plate, and each measurement set allows for multiple determinations of optical properties.

[0140] In a first measurement procedure (e.g., a first measurement set), a first plate 56 can be inserted into a magnifying glass plane, such that the first plurality of markers 510 and the blank area 530 are illuminated by an illumination beam. In this configuration, a first set of field points corresponding to the first set of positions (i.e., the positions of the first plurality of markers 510) is sampled to determine optical properties. In a second measurement procedure (e.g., a second measurement set), a second plate 58 can be inserted into a magnifying glass plane, such that the second plurality of markers 511 and the blank area 530 are illuminated by an illumination beam. In this configuration, a second set of field points corresponding to the second set of positions (i.e., the positions of the second plurality of markers 511) is sampled to determine optical properties. In this way, optical properties can be sampled at each field position corresponding to the positions of the markers (i.e., the set including the first and second positions) in both measurement sets. As previously described with reference to plate system 40 in Figure 4, using only a single set of measurements from plates 56, 58 may result in lower accuracy in determining optical properties because only a subset of field points is sampled. More accurate determinations may be obtained after using two sets of measurements. This plate system 50 enables the acquisition of information about optical properties at an increased frequency (i.e., for each measurement in each set) and enables higher accuracy determinations at a relatively high frequency (for each additional set of measurements).

[0141] Within an EUV lithography apparatus, in the presence of EUV radiation from the illumination beam source, some parts of the apparatus may become contaminated. The portion of the apparatus at the substrate level may be particularly susceptible to this contamination. Markers at the photomask level, such as gratings and pinholes, allow the illumination beam to travel forward to the wafer level. Contamination of these markers at the substrate level can lead to reduced accuracy in determining aberrations and pupil shapes and / or may require cleaning and / or component replacement. By providing n boards, each board can be used 1 / n times, and some locations on the boards may be free of markers. This reduces the amount of contamination experienced by each wafer level marker.

[0142] By providing marker-free locations in a plate system as described herein, where these locations are unmarked on the first plate but have different types of markers on other plates, contamination can be reduced while still being able to determine the optical properties of the relevant field points (i.e., corresponding to the first, second, and third locations). Each time different plates from the three plates are used, one set of locations (i.e., the set of the first, second, or third locations) is shielded from contamination, while the other two sets of locations are sampled. This provides a beneficial trade-off between collecting information for determining optical properties and reducing contamination.

[0143] Therefore, advantageously, blank areas 530 and 531 reduce the frequency of contamination of the substrate level markers when the two boards 56 and 58 are used alternately. Blank areas 530 and 531 may contain a medium that prevents a portion of the illumination beam from propagating forward. For example, in embodiments using transmissive markers on the board (i.e., markers that allow a portion of the illumination beam to propagate through the marker), blank areas 530 and 531 may be substantially opaque to the illumination beam. Contamination in a system typically has negative consequences, such as reduced performance and shortened lifespan, and cleaning or replacing contaminated components is generally beneficial. Specifically, contamination of detectors configured to receive radiation from boards as described herein (e.g., detector D in FIG. 1 or detector 29 in FIG. 2) may reduce their ability to output signals indicating the first and / or second optical properties and / or lead to reduced accuracy in determining the optical properties.

[0144] By providing a plate system 50 with markers 510, 511 and blank areas 530, 531 in an inverse configuration on two plates 56, 58, the two plates are used at half the frequency that a single plate configuration might use. Each substrate level marker can receive radiation at half the frequency (relative to a single plate configuration) while still being able to determine the optical properties at all relevant field points. For example, when using the first plate 56, the second set of locations is essentially shielded from radiation, and therefore the second set of locations is less likely to be contaminated when sampling the first set of locations to determine optical properties. Similarly, when using the second plate 58, the first set of locations is shielded from radiation, and therefore the first set of locations is less likely to be contaminated when sampling the second set of locations to determine optical properties.

[0145] Clearly, there are other areas on plates 56 and 58 that could be blank (e.g., the area around the marker area, the area between the first and second positions). However, the reversible arrangement of markers 510 and 511 and blank areas 530 and 531 on the two plates 56 and 58 provides the significant benefit of reducing contamination in the imaging system.

[0146] The board system 50 depicted in Figure 5 has two separate boards 56, 58. However, in an alternative embodiment, a single board may be used, comprising first and second plurality of markers 510, 511 and blank areas 530, 531. That is, boards 56, 58 may be integral. In this embodiment, the single board may be positioned in a plane, and positioned such that the first plurality of markers 510 and blank areas 530 or the second plurality of markers 511 and blank areas 531 are illuminated by an illumination beam.

[0147] Alternatively, one or both of plates 56 and 58 may form part of a patterned device (e.g., the patterned device MA of FIG1). In this embodiment, the patterned device may have a central area containing a pattern to be imaged by a lithography device, and a plurality of markers 510, 511 and blank areas 530, 531 may be disposed at the edge area of ​​the patterned device.

[0148] The plate system 50, as described above, can be positioned in a first (e.g., a magnifying mask) plane of an imaging system. However, it should be understood that the plate system 50 can also be used in a second (e.g., a wafer) plane of an imaging system. When this plate system 50 is used for wafer alignment in an imaging system, one or more of the plates 56, 58 can form part of a substrate stage (e.g., substrate stage WT of FIG. 1). Alternatively, the plate system 50 can form part of a detector (e.g., detector D of FIG. 1 or detector 29 of FIG. 2) and can be attached to the detector, for example. In this embodiment, one or more of the plates 56, 58 can be positioned such that when illuminated by an illumination beam, radiation from those plates 56, 58 (e.g., radiation interacting with a marker) is received by a radiation receiving portion of the detector.

[0149] Another plate system may include the plate system 50 of FIG. 5 in a first plane for the imaging system, and additionally include third and fourth plates in a second plane for the imaging system. In this alternative plate system, the third and fourth plates substantially match the first plate 56 and the second plate 58 (i.e., for example, the arrangement of markers and blank areas on the third plate substantially matches the arrangement of markers 510 and blank areas 530 on the first plate 56, and the markers on the fourth plate are arranged in a reversible manner relative to the third plate, such that the arrangement of markers and blank areas on the fourth plate substantially matches the arrangement of markers 511 and blank areas 531 on the second plate 58). For example, the spatial arrangement of markers 510 and blank areas 530 on the first plate 56 (on the longer dimension of the first plate 56) may be the same as the spatial arrangement of markers and blank areas on the third plate (on the longer dimension of the third plate). Similarly, the spatial arrangement of markers 511 and blank areas 531 on the second plate 58 (over the longer dimension of the second plate 58) can be the same as the spatial arrangement of markers and blank areas on the fourth plate (over the longer dimension of the fourth plate). The third and fourth plates are substantially matched with the first plate 56 and the second plate 58, in a manner similar to the substantially matched arrangement of the second plurality of markers 311, 321 on the second plate 38 and the first plurality of markers 310, 320 on the first plate 36 in Figure 3. In use, the plate system 50 of Figure 5 can be configured in the first plane of the imaging system, staggered between the first plate 56 and the second plate 58 for each set of measurements, while the additional plate system can be configured in the second plane, correspondingly staggered between the third and fourth plates. In this other plate system, the first and second plates can actually be integrated, and the third and fourth plates can be additionally or alternatively integrated.

[0150] Figure 6 depicts a plate system 60 that can be used in an imaging system (e.g., imaging system 20 of Figure 2) to determine one of two optical properties of the illumination beam of the imaging system. Plate system 60 includes a first plate 66, a second plate 67, and a third plate 68. As with the plate systems described previously, plates 66, 67, and 68 may actually be a single unit, rather than three separate plates as illustrated in Figure 6.

[0151] The first plate 66 has a first plurality of markers 610 and 620. A first subset 610 of the first plurality of markers 610 and 620 is a first type of marker configured to determine a first optical property of the illumination beam. A second subset 620 of the first plurality of markers 610 and 620 is a second type of marker configured to determine a second optical property of the illumination beam. The first subset 610 of markers is located at a first set of positions, and the second subset 620 of markers is located at a second set of positions. The first plate 66 also has a third set of positions, which includes areas without markers 630, which may be referred to as blank areas 630.

[0152] The second plate 67 has a second plurality of markers 611 and 621. A first subset 611 of the second plurality of markers 611 and 621 is a marker of a first type and is located at the set of second positions corresponding to the set of second positions on the first plate 66. That is, the markers of the first type on the second plate 67 occupy the positions occupied by the markers of the second type on the first plate 66. A second subset 621 of the second plurality of markers 611 and 621 is a marker of a second type and is located at the set of third positions corresponding to the set of third positions on the first plate 66. That is, the markers of the second type on the second plate 67 occupy the positions occupied by the blank areas on the first plate 66. The second plate 67 also has a set of first positions, which includes areas without markers 631, which may be referred to as blank areas. The set of first positions on the second plate 67 corresponds to the set of first positions on the first plate 66. That is, the blank area 631 on the second plate 67 occupies the position occupied by the first type of marker on the first plate 66.

[0153] The third plate 68 has a third plurality of markers 612 and 622. A first subset 612 of the third plurality of markers 612 and 622 is a marker of the first type and is located at the set of third positions corresponding to the set of third positions on the first plate 66. That is, the markers of the first type on the third plate 68 occupy the positions occupied by the blank areas on the first plate 66 (and the markers of the second type on the second plate 67). A second subset 622 of the third plurality of markers 612 and 622 is a marker of the second type and is located at the set of first positions corresponding to the set of first positions on the first plate 66. That is, the markers of the second type on the third plate 68 occupy the positions occupied by the markers of the first type on the first plate 66. The third plate 68 also has a set of second positions, which includes areas without marker 632, which can be referred to as blank areas. The set of second positions on the third plate 68 corresponds to the set of second positions on the first plate 66. That is, the blank area 632 on the third plate 68 occupies the position occupied by the second type of marker on the first plate 66.

[0154] In summary, the markers and blank areas of the first plate 66, the second plate 67, and the third plate 68 are arranged in a reversible or cyclical manner.

[0155] On each plate 66, 67, 68, markers and blank areas are arranged in a marker area (not shown), which generally corresponds to the illumination area of ​​the imaging system. Specifically, in the depicted arrangement, a set of first positions, a set of second positions, and a set of third positions are equidistantly spaced along an elongated, curved marker area, and alternate in a cyclical manner between first-type markers, second-type markers, and blank areas. It should be understood that different arrangements of markers and marker areas are possible in other embodiments (e.g., using different imaging systems and / or different illumination areas).

[0156] In use, the plate system 60 is configured for use as a single level in the imaging system. For example, the plate system 60 can be used in a magnification mask level of the imaging system (i.e., each plate is interchangeably positioned in the magnification mask plane). Although described below as being used in a single level (e.g., at a magnification mask level) of the imaging system, it will be understood that the plate system 60 can typically be used in conjunction with another substantially matching plate system provided at another level (e.g., at a substrate level) of the imaging system to determine one or more optical properties of the illumination beam. Each plate 66, 67, 68 can be used to perform a single measurement set and perform the determination of the optical properties of the illumination beam. Thus, the interchangeable use of each plate 66, 67, 68 enables three measurement sets, each using different marker configurations on the plate, and each measurement set allows for multiple determinations of optical properties.

[0157] In the first measurement procedure (e.g., the first measurement set), the first plate 66 can be inserted into the plane of the magnifying mask, such that the first plurality of markers 610, 620 and the blank area 630 are illuminated by the illumination beam. In this configuration, a first set of field points corresponding to the first set of positions (i.e., the positions of the first subset of markers 610) is sampled to determine a first optical property, and a second set of field points corresponding to the second set of positions (i.e., the positions of the second subset of markers 620) is sampled to determine a second optical property. A third set of field points corresponding to the third set of positions (i.e., the positions of the blank area 630) is shielded (and, as discussed above, contamination can be reduced).

[0158] In the second measurement procedure (e.g., the second measurement set), the second plate 67 can be inserted into the magnifying mask plane, such that the second plurality of markers 611, 621 and the blank area 631 are illuminated by the illumination beam. In this configuration, a second set of field points corresponding to the second set of positions (i.e., the positions of the first subset 611 of the second plurality of markers 611, 621) is sampled to determine the first optical property, and a third set of field points (i.e., the positions of the second subset 621 of the second plurality of markers 611, 621) is sampled to determine the second optical property. The first set of field points corresponding to the first set of positions (i.e., the positions of the blank area 631) is shielded (and, as discussed above, contamination can be reduced).

[0159] In the third measurement procedure (e.g., the third measurement set), the third plate 68 can be inserted into the magnifying mask plane, such that the third plurality of markers 612, 622 and the blank area 632 are illuminated by the illumination beam. In this configuration, the third set of field points corresponding to the third set of positions (i.e., the positions of the first subset 612 of the third plurality of markers 612, 622) is sampled to determine the first optical property, and the first set of field points (i.e., the positions of the second subset 622 of the third plurality of markers 612, 622) is sampled to determine the second optical property. The second set of field points corresponding to the second set of positions (i.e., the positions of the blank area 632) is shielded (and, as discussed above, contamination can be reduced).

[0160] In this manner, the first and second optical properties can be fully sampled at each field position of one of the three measurement sets corresponding to the location of the marker (i.e., the set containing the first, second, and third positions). It has been found that acceptable imaging performance can be achieved by sampling each field point with only three measurement sets. As previously described with reference to plate system 40 in Figure 4 and plate system 5 in Figure 5, using only a single measurement set of plates 66, 67, and 68 may produce lower accuracy in optical property determination because only a subset of field points is sampled, while more accurate determinations may be produced after two or three measurement sets. This plate system 60 enables information about the first and second optical properties to be obtained at an increased frequency (i.e., per measurement set) and enables determinations with higher accuracy at a relatively high frequency (per two or three measurement sets). Furthermore, by providing three plates 66, 67, and 68 with reciprocal configurations of markers 610, 620, 611, 621, 612, 622 and blank areas 630, 631, 632, contamination can be reduced while still being able to determine the optical properties of the relevant field points.

[0161] The board system 60 may form part of a patterned device (e.g., patterned device MA of FIG. 1), a scaled-down mask stage (e.g., support structure MT of FIG. 1), or a substrate stage (e.g., substrate W or substrate stage WT of FIG. 1). Alternatively, the board system 60 may form part of a detector (e.g., detector D of FIG. 1 or detector 29 of FIG. 2) and may be attached to such detector, for example. In this embodiment, one or more of the boards 66, 67, and 68 may be positioned such that when illuminated by an illumination beam, radiation from those boards 66, 67, and 68 (e.g., radiation interacting with a marker) is received by a radiation receiving portion of the detector.

[0162] Plate system 60 can be used as a magnification mask level or wafer level in the imaging system of a lithography system. A corresponding matching plate system can be used for another level in the magnification mask level or wafer level of the imaging system. That is, another plate system may include plate system 60 of FIG. 6 for the first plane of the imaging system, and additionally include fourth, fifth, and sixth plates for the second plane of the imaging system, wherein the fourth, fifth, and sixth plates substantially match the first plate 66, the second plate 67, and the third plate 68. For example, the spatial arrangement of markers 610, 620, 611, 621, 612, 622 and blank areas 630, 631, 632 on the first plate 66 (on the longer dimension of the first plate 66) may be the same as the spatial arrangement of markers and blank areas on the fourth plate (on the longer dimension of the fourth plate). Similarly, the spatial arrangement of markers 610, 620, 611, 621, 612, 622 and blank areas 630, 631, 632 on the second plate 67 (on the longer dimension of the second plate 68) can be the same as the spatial arrangement of markers and blank areas on the fifth plate (on the longer dimension of the fifth plate). Similarly, the spatial arrangement of markers 610, 620, 611, 621, 612, 622 and blank areas 630, 631, 632 on the third plate 68 (on the longer dimension of the third plate 68) can be the same as the spatial arrangement of markers and blank areas on the sixth plate (on the longer dimension of the sixth plate). In this other plate system, the fourth, fifth, and sixth plates can be integrated into one unit.

[0163] Figure 7 depicts an example configuration of markers on the two plates 76 and 78. One of the first plate 76 and the second plate 78 can be used to replace the first plate 26 of Figure 2, that is, one of the two plates 78 and 76 can be positioned in the first plane of the imaging system. The other of the first plate 76 and the second plate 78 can be used to replace the second plate 28 of Figure 2, that is, the other of the two plates 76 and 78 can be positioned in the second plane of the imaging system.

[0164] In one embodiment, the first plate 76 can be used in place of the first plate 26 in FIG2, that is, the first plate 76 can be positioned in a first plane of the imaging system, and the second plate 78 can be used in place of the second plate 28 in FIG2, that is, the second plate 78 can be positioned in a second plane of the imaging system. The nominal x-direction and y-direction are depicted. The x-direction corresponds to the non-scanning direction of the imaging system using plates 76 and 78. The y-direction corresponds to the scanning direction of the imaging system using plates 76 and 78.

[0165] The first plate 76 is similar to the first plate 36 depicted in Figure 3. That is, the first plate 76 includes a first plurality of markers 710, 720 disposed in a marker area 71 that generally corresponds to the illumination area 72. A first subset 710 of the first plurality of markers contains markers of a first type, and a second subset 720 of the first plurality of markers contains markers of a second type. The marker area 71 and the illumination area 72 are elongated and curved, and the markers 710, 720 are disposed in an elongated and curved manner, the radius of curvature of which generally corresponds to the curvature of the elongated illumination area 72.

[0166] The second plate 78 is similar to the second plate 38 depicted in Figure 3, but with a different marker configuration. The second plate 78 includes a second plurality of markers 711, 721 arranged in a marker area 73 that substantially corresponds to the illumination area 74. A first subset 711 of the second plurality of markers contains markers of a first type, and a second subset 721 of the second plurality of markers contains markers of a second type. However, the markers 711, 721 are arranged in a straight line rather than a curved one. The markers 711, 721 of the second plate 78 match the markers 710, 720 of the first plate 76, in that the spatial arrangement of the first plurality of markers 711 and the second plurality of markers 721 along the longer dimension of the marker area 72 is the same as the spatial arrangement of the first plurality of markers 710 and the second plurality of markers 720 along the longer dimension of the marker area 71. Specifically, the markers 711 and 721 of the second plate 78 are matched with the markers 710 and 720 of the first plate 76 in terms of their positional matching in the x-direction (e.g., taking into account any reduction factors for the imaging system application). Therefore, when the first plate 76 is illuminated in the first plane, the image of each of the first plurality of markers 710 and 720 is aligned (i.e., coincident) in the x-direction with the corresponding one of the second plurality of markers 711 and 721. However, the images of some of the first plurality of markers 710 and 720 may not be aligned in the y-direction with the corresponding one of the second plurality of markers 711 and 721. Therefore, a small relative movement (e.g., scanning or stepping) of the plates 76 and 78 in the y-direction may be required to form an image of each of the first plurality of markers 710 and 720 on the corresponding one of the second plurality of markers 711 and 721. Because the movement is small (e.g., compared to the size of the marker area), it can be performed quickly, making it possible to illuminate each of the markers almost simultaneously, although the illumination is not exactly simultaneous.

[0167] In an alternative configuration, the markers 710 and 720 of the first plate 76 can be arranged in a straight line rather than a curved manner, and the markers 711 and 721 of the second plate 78 can be arranged in a curved manner. Furthermore, generally, the radii of curvature of each of the two plates 76 and 78 can be different. For example, the markers 710 and 720 of the first plate 76 can be arranged with a first radius of curvature, and the markers 711 and 721 of the second plate 78 can be arranged with different second radii of curvature.

[0168] Figure 8 depicts an alternative configuration of the markers on plate 86. Plate 86 can be used in combination with a corresponding plate located at one field plane (e.g., the wafer plane) of the imaging system and at another field plane (e.g., the magnification mask plane) of the imaging system. The corresponding plate can be any other plate described herein. For example, plate 86 can be located at the wafer plane of the imaging system, and a corresponding plate from one of the plate systems 40, 50, and 60 described with reference to Figures 4, 5, and 6 can be located at the magnification mask plane of the imaging system.

[0169] Board 86 includes a plurality of markers 800 disposed at a plurality of locations. The markers 800 are generally disposed relative to the marking area and the illumination area, as previously described for other boards. The markers 800 illustrated in FIG8 are configured to generally match the positions of the markers on the boards of board systems 40, 50, 60 of FIG4, 5, or 60 (e.g., a set of first, second, and, if applicable, third positions). Thus, the markers 800 are disposed at positions that generally match the positions of the markers on the corresponding boards of the board system used with board 86.

[0170] Each position on plate 86 includes two markers 810 and 820, and therefore the markers 800 on the plate can be referred to as dual markers 800. Each dual marker 800 includes a first type of marker 810 and a second type of marker 820. The first type of marker 810 and the second type of marker 820 are configured to determine the first or second optical properties of the illumination beam, respectively. A plurality of dual markers 800 are configured such that each marker from a corresponding plate of a plate system in another plane of the imaging system can be imaged onto the dual markers 800 of plate 86. Specifically, a plurality of dual markers 800 are configured such that each marker from a corresponding plate of a plate system in another plane of the imaging system can be imaged onto one of the two markers 810 and 820 of the dual markers 800 of plate 86.

[0171] The use of board 86 will be described with reference to its use with board system 40 of Figure 4 (i.e., such that boards 46, 48 contain corresponding boards). However, it should be understood that this use is illustrative in nature, and board 86 can be used in a similar manner with any other corresponding board (or set of corresponding boards).

[0172] The spatial arrangement of the first plurality of markers 410 and the second plurality of markers 420 on the first plate 46 shown in Figure 4 (on the longer dimension of the first plate 46) is the same as the spatial arrangement of the first type of markers 810 and the second type of markers 820 above the double markers 800 on the plate 86 shown in Figure 8 (on the longer dimension of the plate 86). Similarly, the spatial arrangement of the first plurality of markers 430 and the second plurality of markers 440 on the second plate 48 shown in Figure 4 (on the longer dimension of the first plate 48) is the same as the spatial arrangement of the first type of markers 810 and the second type of markers 820 below the double markers 800 on the plate 86 shown in Figure 8 (on the longer dimension of the plate 86).

[0173] The first plate 46 of the plate system 40 can be used as a corresponding plate (i.e., the first corresponding plate 46) for the first measurement. The first corresponding plate 46 is positioned in a first plane of the imaging system and is illuminated, while plate 86 is positioned in a second plane of the imaging system. The image of the first subset 410 of the markers is formed at a set of first positions on plate 86 corresponding to the first subset of the dual markers 800. Specifically, the image of the first subset 410 of the markers is formed at a set of first positions on plate 86 corresponding to the upper marker 810 of each dual marker in the first subset of the dual markers 800 in FIG. 8. Therefore, the radiation received by each marker 810 from the first subset of the dual markers 800 interacts with the portion of the dual markers 800 corresponding to the first type of markers, such that when the radiation is received by the detector, the first optical properties of the set of first positions can be determined. Similarly, the image of the second subset 420 of the markers is formed on the plate 86 at a set of second positions corresponding to the second subset of the dual markers 800. Specifically, the image of the second subset 420 of the markers is formed on the plate 86 at a set of second positions corresponding to the upper marker 820 of each dual marker in the second subset of the dual markers 800 in FIG. 8. Therefore, the radiation received by each marker 820 from the second subset of the dual markers 800 interacts with the portion of the dual markers 800 corresponding to the second type of markers, such that when the radiation is received by the detector, the first optical properties of the set of first positions can be determined.

[0174] The second plate 48 of the plate system 40 can be used as a corresponding plate (i.e., the second corresponding plate 48) for the second measurement. The second corresponding plate 48 is positioned in the first plane of the imaging system and is illuminated, and the plate 86 is positioned in the second plane of the imaging system. The image of the first subset 430 of the markers is formed on the plate 86 at the set of second positions corresponding to the lower markers 810 in the second subset of the dual markers 800 in FIG. 8. Therefore, the radiation received by each marker 810 from the second subset of the dual markers 800 interacts with the portion of the dual markers 800 corresponding to the first type of markers 810, such that when the radiation is received by the detector, the first optical properties of the set of first positions can be determined. Similarly, the image of the second subset 440 of the markers is formed on the plate 86 at the set of first positions corresponding to the first subset of the dual markers 800. Specifically, the image of each marker in the second subset 440 of the markers is formed at the lower marker 820 of the double markers in the first subset of the double markers 800. Therefore, the radiation received by each marker 800 from the first subset of the double markers 800 interacts with the portion of the double markers 800 corresponding to the second type of marker 820, such that when the radiation is received by the detector, the second optical properties of the set of first locations can be determined.

[0175] In any measurement (i.e., when the first corresponding plate 46 or the second corresponding plate 48 is used in the first plane), the same plate 86 can be used in the second plane while still achieving the aforementioned advantages of the plate system described herein. Furthermore, using the same plate 86 allows for easy attachment of the plate 86 to the detector (e.g., while minimizing the size of the detector). Each pair of markers 800 allows radiation to propagate from the marker 800 to the detection portion of the corresponding detector. Having a single plate 86 attached to the detector allows for the detection of one or more optical properties using multiple corresponding plates (e.g., in a magnified mask level) without the need for exchange of plates associated with the detector and / or relative movement between the detector and its associated plates. Using a single plate 86 results in time savings (e.g., because no time is spent alternating between plates in the second plane). Using a single plate 86 produces more robust judgments, for example, because fewer components (e.g., plates) result in fewer exchanges or movements, thus requiring fewer moving parts.

[0176] Each portion of the dual markers 800 (i.e., the portions corresponding to the first type of marker 810 and the second type of marker 820) can be considered to be located at substantially the same position on the plate 86. Specifically, each portion of each dual marker 800 (i.e., the portions corresponding to the first type of marker 810 and the second type of marker 820) can be considered to be located at substantially the same position on the plate 86 in the direction of the longer dimension of the plate 86 (which may correspond to the non-scanning direction of the imaging system using the plate 86). Thus, each dual marker 800 can be considered to be sampled from a single field point relative to the field point sampled from the corresponding plate. It should be understood that, in practice, the first type of marker 810 and the second type of marker 820 may, for example, have some spatial separation in the direction of the shorter dimension of the plate 86. However, the distance between the first type of marker 810 and the second type of marker 820 of each dual marker 800 is small, especially compared to the distance between adjacent dual markers 800. For example, the distance between the first type of marker 810 and the second type of marker 820 of each pair of markers 800 can be about 10 to 100 times smaller than the distance between adjacent pair of markers 800.

[0177] When a plate with dual markers (e.g., plate 86 in Figure 8) is used in combination with a corresponding plate with a blank area (e.g., plates in the plate system of Figure 5 or Figure 6), the plate with dual markers may not have a blank area. However, the plate with dual markers can be considered to roughly match the corresponding plate, because each marker (e.g., a marker of the first and / or second type) can still correspond to the position of the dual markers on the plate with dual markers. Furthermore, even if the second plate (e.g., in the second plane) does not contain a blank area, the beneficial effect of reducing contamination propagating through the imaging system can still be achieved by using a single plate with a blank area (e.g., in the first plane).

[0178] This article describes specific example configurations of imaging systems, plates, and plate systems. However, it should be understood that features of different configurations (e.g., features related to configuration, marker type, and implementation method) can be combined.

[0179] This document has specifically referenced the use of gratings to determine aberration maps and pinholes to determine angular distribution. However, many types of markers will be known to those skilled in the art, and it should be understood that different markers can be used to determine aberration maps and / or angular distribution, and other optical properties can be determined by appropriately selecting the type of marker. Other examples of markers that can be used include slits, pinhole arrays, or polarizers to measure the polarization of radiation in an illumination beam. In embodiments that measure radiation polarization, the optical property under discussion may be the polarization of the illumination beam.

[0180] The grating depicted in the figures is schematically shown as a single grating with a single orientation. However, gratings comprising different patterned regions with different orientations can be used. For example, the grating may include a first patterned region aligned along a first direction and a second patterned region aligned along a second direction perpendicular to the first direction. The first and second directions may form an angle of approximately 45° with respect to the x-direction and y-direction (e.g., the scanning direction and the non-scanning direction). Illumination of the first patterned region provides information related to aberrations in the first direction, and illumination of the second patterned region provides information related to aberrations in the second direction.

[0181] To determine aberrations caused by the projection system, the illumination system mode can be changed. For example, during normal operation of the lithography apparatus, the illumination system can be configured to illuminate the in-use illumination area of ​​the first plane. However, the illumination system mode can be changed so that the measurement illumination area of ​​the first plane is illuminated. In this case, the marker area can correspond to the measurement illumination area.

[0182] In addition to applying or alternatively applying a reduction factor, the projection system may also rotate and / or mirror and / or distort the image of the first plane formed in the second plane. In such cases, the second plate, which can be positioned in the second plane, matches the first plate, which can be positioned in the first plane, such that any rotation and / or mirroring and / or distortion is taken into account in the arrangement of markers (and, where appropriate, blank areas) on the second plate.

[0183] In some implementations, the illumination beam, plate, and / or detector may be scanned and / or stepped sequentially. Stepping may be in a direction perpendicular to the alignment of the diffraction grating being illuminated. Stepping may be a distance corresponding to a fraction of the grating period. Measurements taken at different stepping positions can be analyzed to derive information about the wavefront in the stepping direction. Stepping can be performed in two perpendicular directions, allowing information about the wavefront to be derived in both perpendicular directions (specifically, providing information about the derivative of the wavefront in each of the two perpendicular directions), thereby allowing the reconstruction of the complete wavefront. This stepping should not be considered a substantial movement of the illumination beam, plate, and / or detector. For example, the stepping distance may be small relative to the size of the marker area and not commensurate with moving the illumination beam and / or plate to illuminate different marker areas.

[0184] The illustrated marker configuration includes four or seven markers (and, as appropriate, a blank area). However, it should be understood that any number of markers can be used, such as two (one of each type) or thirty. Furthermore, the illustrated marker configuration includes markers arranged in a single line (albeit a curve). In alternative configurations, markers may be arranged in multiple rows or generally dispersed over an area. For example, in imaging systems where the illumination area is not elongated, markers may typically be positioned around the edge and interior of a marker area corresponding to the illumination area. In a non-limiting example, for a circular illumination area, markers may be arranged within a circular marker area within concentric circles.

[0185] While references may be specifically made herein to the use of lithography devices in IC manufacturing, it should be understood that the lithography devices described herein may have other applications. Possible other applications include the fabrication of integrated optical systems, guiding and detecting patterns for magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, and so on.

[0186] Although specific reference may be made herein to embodiments or exemplary implementations of the invention within the context of lithography apparatus, embodiments of the invention can be used in other apparatuses. Embodiments of the invention can form components of any apparatus for mask detection, measurement, or measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). Such apparatuses may generally be referred to as lithography tools. These lithography tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0187] Where the context permits, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. Machine-readable media may include any means for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, machine-readable media may include read-only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.); and others. Furthermore, firmware, software, conventions, and instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are merely for convenience, and such actions are in fact caused by a computing device, processor, controller, or other device executing firmware, software, conventions, instructions, etc. And this enables actuators or other devices to interact with the physical world.

[0188] While specific examples of the invention have been described above, it will be understood that the invention may be practiced in other ways different from those described. The description above is intended to be illustrative and not restrictive. Thus, it will be apparent to those skilled in the art that modifications can be made to the described invention without departing from the scope of the claims set forth below.

[0189] Terms and conditions 1. An imaging system comprising: A first plane, configured to receive an illumination beam in a first region; A second plane, configured to receive an image of the first area in a second area of ​​the second plane; A first plate, which contains a first plurality of markers, wherein: The first subset of the first plurality of markers includes markers used to determine a first type of a first optical property of the illumination beam; The second subset of the first plurality of markers includes markers for determining a second type of a second optical property of the illumination beam; and The first plate can be positioned in the first plane such that the first plurality of markers are located within the first area; A second plate, which contains a second plurality of markers, wherein: The first subset of the second plurality of markers includes markers for determining a first type of the first optical property of the illumination beam; The second subset of the second plurality of markers includes markers for determining a second type of the second optical property of the illumination beam; The configuration of the second plurality of markers roughly matches the configuration of the first plurality of markers; and The second plate can be positioned within the second plane such that the second plurality of markers are located within the second area; and A detector that can be positioned in a third plane and is operable to: When the second plate is placed in the second zone, it receives radiation from the second plate; and The output signal indicates one of the first optical properties and / or the second optical properties of the illumination beam. 2. The imaging system of clause 1, wherein the arrangement of the second plurality of markers substantially matches the arrangement of the first plurality of markers, such that when the first plate is placed in the first region and the second plate is placed in the second region, an image of each of the first plurality of markers coincides with a corresponding image of the second plurality of markers in a first direction. 3. An imaging system as described in clause 1 or clause 2, wherein the arrangement of the second plurality of markers substantially matches the arrangement of the first plurality of markers, such that when the first plate is placed in the first region and the second plate is placed in the second region, an image of each of the first plurality of markers coincides with a corresponding image of the second plurality of markers. 4. An imaging system as described in any of the preceding clauses, wherein the first optical property is an aberration map of the illumination beam, and wherein each of the markers of the first type comprises a grating. 5. An imaging system as described in any of the preceding clauses, wherein the second optical property is that the illumination beam is distributed at an angle in the first region, and wherein each of the second type of markers includes a pinhole. 6. The imaging system of any of the preceding clauses further comprises: The third plurality of markers can be positioned in the first plane, wherein: The first subset of the third plurality of markers includes markers used to determine the first type of a first optical property of the illumination beam; The second subset of the third plurality of markers includes markers used to determine the second type of the second optical property of the illumination beam; The third plurality of markers can be simultaneously located within the first area; and The configuration of the third plurality of markers differs from the configuration of the first plurality of markers; and A fourth plurality of markers, which can be positioned in the second plane, wherein: The first subset of the fourth plurality of markers includes markers used to determine the first type of one of the first optical properties of the illumination beam; The second subset of the fourth plurality of markers includes markers used to determine the second type of the second optical property of the illumination beam; The fourth plurality of markers can be located within the second area; and The configuration of the fourth plurality of markers roughly matches the configuration of the third plurality of markers. 7. The imaging device as described in item 6, wherein: The first plate further includes the third plurality of markers, and the first plate is further locating such that the third plurality of markers are located within the first area; and The second plate further includes the fourth plurality of markers, and the second plate is further configurable such that the fourth plurality of markers are located within the second area. 8. The imaging apparatus of item 6, further comprising: A third plate, comprising the third plurality of markers, the third plate being positionable in the first plane such that the third plurality of markers are located within the first region; and A fourth plate containing the fourth plurality of markers, the fourth plate being positionable in the second plane such that the fourth plurality of markers are located within the second area. 9. A lithography apparatus comprising an imaging device as described in any of the preceding claims and further comprising: A lighting system operable to illuminate the first area with a beam of light; and A projection system operable to form an image of one of the first zones at the second zone. 10. A method for determining one or more optical properties of an imaging system as described in any one of items 1 to 8, the method comprising: Position the first plate in the first plane such that the first plurality of markers are located within the first area; Position the second plate within the second plane such that the second plurality of markers are located within the second area; Illuminate the first area with a beam of light; The detector is used to receive radiation from the second plate; The detector receives the signal indicating the first optical property and / or the second optical property of the illumination beam; and The first optical property and / or the second optical property of the illumination beam are determined based on the signal. 11. A plate for use in an imaging system to determine two optical properties of an illumination beam of the imaging system configured to illuminate an illumination area with the illumination beam, the plate comprising a plurality of markers, wherein: The first subset of the plurality of markers includes markers used to determine a first type of a first optical property of the illumination beam; The second subset of the plurality of markers includes markers used to determine a second type of a second optical property of the illumination beam; and The plurality of markers are located within one of the marker areas of the plate; and The marked area roughly corresponds to the illuminated area. 12. The plate as described in clause 11, wherein each of the markers of the first type comprises a grating. 13. The plate as described in clause 11 or 12, wherein each of the markers of the second type contains a pinhole. 14. A plate as described in any of items 11 to 13, wherein the marked area is elongated. 15. A plate as described in any of clauses 11 to 14, wherein a first marker of the plurality of markers is located at or near a first end of the marker area, a second marker of the plurality of markers is located at or near a second end of the marker area away from the first end, and the other markers of the plurality of markers are distributed between the first marker and the second marker. 16. A plate as described in any of clauses 11 to 15, wherein adjacent markers of the plurality of markers alternate between markers of the first type and markers of the second type. 17. A plate system for use in an imaging system to determine two optical properties of an illumination beam of the imaging system, the imaging system being configured to illuminate an illumination area with the illumination beam, the plate system comprising a first plate and a second plate, each as described in any one of items 11 to 16, wherein: On the first board, the first subset of the plurality of markers is located at one set of first positions, and the second subset of the plurality of markers is located at one set of second positions; On the second board, the first subset of the plurality of markers is located at one set of second positions, and the second subset of the plurality of markers is located at one set of first positions; The first positions of the first plate correspond to the first positions of the second plate, and the second positions of the first plate correspond to the second positions of the second plate. 18. A plate system for use in an imaging system to determine two optical properties of an illumination beam of the imaging system, the plate system comprising a first plate, a second plate, and a third plate, each as claimed in any one of claims 11 to 16, wherein: On the first board, the first subset of the plurality of markers is located at one set of first positions, and the second subset of the plurality of markers is located at one set of second positions; The first plate further includes a set of third positions that do not contain markers; On the second board, the first subset of the plurality of markers is located at one set of second positions, and the second subset of the plurality of markers is located at one set of third positions; The second plate further includes a set of first positions that do not contain markers; On the third board, the first subset of the plurality of markers is located at one set of third positions, and the second subset of the plurality of markers is located at one set of first positions; The third plate further includes a set of second locations that do not contain markers; The first positions of the first plate correspond to the first positions of the second plate and the first positions of the third plate; The second positions of the first plate correspond to the second positions of the second plate and the second positions of the third plate; and The third positions of the first plate correspond to the third positions of the second plate and the third positions of the third plate. 19. A plate system for use in an imaging system to determine an optical property of an illumination beam of the imaging system, the imaging system being configured to illuminate an illumination area with the illumination beam, the plate system comprising: The first board contains: A first plurality of markers, used to determine the optical properties of the illumination beam, the first plurality of markers being located at a set of first positions; and Not containing one set of the second positions of the marker; The second board contains: A second plurality of markers, used to determine the optical properties of the illumination beam, are located at one set of second positions corresponding to the second position of the first plate; and It does not contain one set of the first positions of the markers; and Wherein the set of the first position of the second board corresponds to the set of the first position of the first board; and The first plurality of markers are located in a first marker area that roughly corresponds to one of the illumination areas; and The second plurality of markers are located in a second marker area that roughly corresponds to one of the lighting areas. 20. A stage for holding a 1x reduction mask, the stage comprising a plate or plate system as described in any one of items 11 to 19. 21. A substrate stage for holding a substrate, the substrate stage comprising a plate as described in any one of items 11 to 19. 22. A detector comprising a plate as described in any one of items 11 to 19.

[0190] 10: Faceted field mirror devices 11: Faceted pupil mirror device 13: Mirror 14: Mirror 20: Imaging System 21: Illumination beam 22: Lighting System 24: Projection System 26: First board 28: Second board 29: Detector 31: Marker Area 32: Lighting Area 33: Marker Area 34: Lighting Area 36: First board 38: Second board 40: Board System 46: First board 48: Second board 50: Board System 56: First board 58: Second board 60: Board System 66: First board 67: Second board 68: Third Board 71: Marker Area 72: Lighting Area 73: Marker Area 74: Lighting Area 76: First board 78: Second board 86: Board 100: Reduced Mask Plane 102: Substrate Plane 200: First plane 202: Second Plane 204: Third Plane 210: Marker 211: Marker 220: Marker 221: Marker 310: Marker 311: Marker 320: Marker 321: Marker 330: First marker 340: Second marker 350: First marker 360: Second marker 410: Marker 420: Marker 430: Marker 440: Marker 510: Marker 511: Marker 530: Blank area / marker 531: Blank area / marker 610: Marker 611: Marker 612: Marker 620: Marker 621: Marker 622: Marker 630: Blank area / marker 631: Blank area / marker 632: Blank area / marker 710: Marker 711: Marker 720: Marker 721: Marker 800: Marker 810: Marker 820: Marker B: EUV radiation beam D: Detector IL: Lighting System LA: Microfilm Installation MA: Patterning Devices / Reducing Masks MT: Support structure / reduced photomask PS: Projection system SO: Radiation source W: substrate WT: substrate table x: direction y: direction

Claims

1. An imaging system comprising: a first plane configured to receive an illumination beam in a first region; a second plane configured to receive an image of the first region in a second region of the second plane; and a first plate comprising a first plurality of markers, wherein: A first subset of the first plurality of markers includes markers for determining a first type of a first optical property of the illumination beam; a second subset of the first plurality of markers includes markers for determining a second type of a second optical property of the illumination beam, the second type of markers having a form different from the first type of markers; and the first plate can be positioned in the first plane such that the first plurality of markers are located within the first region; a second plate includes a second plurality of markers, wherein: a first subset of the second plurality of markers includes markers for determining the first optical property of the illumination beam. A first type of marker of one property; a second subset of a second plurality of markers including a second type of marker for determining the second optical property of the illumination beam; the arrangement of the second plurality of markers substantially matching the arrangement of the first plurality of markers; and the second plate being positionable in the second plane such that the second plurality of markers are located within the second region; and a detector being positionable in a third plane and operable to: receive radiation from the second plate when the second plate is placed in the second region; and output a signal indicating the first optical property and / or one of the second optical properties of the illumination beam.

2. The imaging system of claim 1, wherein the configuration of the second plurality of markers substantially matches the configuration of the first plurality of markers, such that when the first plate is placed in the first region and the second plate is placed in the second region, an image of each of the first plurality of markers coincides with a corresponding image of the second plurality of markers in a first direction.

3. The imaging system of claim 1 or claim 2, wherein the configuration of the second plurality of markers substantially matches the configuration of the first plurality of markers, such that when the first plate is placed in the first region and the second plate is placed in the second region, an image of each of the first plurality of markers coincides with a corresponding image of the second plurality of markers.

4. An imaging system as claimed in claim 1 or claim 2, wherein the first optical property is an aberration map of the illumination beam, and wherein each of the first type of markers includes a grating, or / and wherein the second optical property is an angular distribution of the illumination beam in the first region, and wherein each of the second type of markers includes a pinhole.

5. The imaging system of claim 1 or claim 2, further comprising: a third plurality of markers, which can be positioned in the first plane, wherein: The first subset of the third plurality of markers includes markers for determining a first type of the first optical property of the illumination beam; the second subset of the third plurality of markers includes markers for determining a second type of the second optical property of the illumination beam; the third plurality of markers can be simultaneously positioned within the first region; and the configuration of the third plurality of markers is different from the configuration of the first plurality of markers; and the fourth plurality of markers can be positioned in the second plane, wherein: the first subset of the fourth plurality of markers includes markers for determining a first type of the first optical property of the illumination beam; the second subset of the fourth plurality of markers includes markers for determining a second type of the second optical property of the illumination beam; the fourth plurality of markers can be positioned within the second region; and the configuration of the fourth plurality of markers substantially matches the configuration of the third plurality of markers.

6. The imaging system as described in claim 5, wherein: The first plate further includes the third plurality of markers, and the first plate is further positioned such that the third plurality of markers are located within the first area; and the second plate further includes the fourth plurality of markers, and the second plate is further positioned such that the fourth plurality of markers are located within the second area.

7. The imaging system of claim 5, further comprising: a third plate containing the third plurality of markers, the third plate being positionable in the first plane such that the third plurality of markers are located within the first region; and a fourth plate containing the fourth plurality of markers, the fourth plate being positionable in the second plane such that the fourth plurality of markers are located within the second region.

8. A lithography apparatus comprising an imaging system as claimed in any one of claims 1 to 7 and further comprising: an illumination system operable to illuminate the first region with an illumination beam; and a projection system operable to form an image of the first region at the second region.

9. A method for determining one or more optical properties of an imaging system as claimed in any one of claims 1 to 7, the method comprising: positioning a first plate in the first plane such that a first plurality of markers are located within the first region; positioning a second plate in the second plane such that a second plurality of markers are located within the second region; illuminating the first region with an illumination beam; receiving radiation from the second plate with the detector; receiving from the detector a signal indicating the first optical property and / or the second optical property of the illumination beam; and determining the first optical property and / or the second optical property of the illumination beam based on the signal.

10. A plate for use in an imaging system to determine at least two optical properties of an illumination beam of the imaging system configured to illuminate an illumination area with the illumination beam, the plate comprising a plurality of markers, wherein: The first subset of the plurality of markers includes markers for determining a first type of a first optical property of the illumination beam; the second subset of the plurality of markers includes markers for determining a second type of a second optical property of the illumination beam, the second type of markers having a form different from the first type of markers; and the plurality of markers are located within a marker area of ​​the plate; and the marker area substantially corresponds to the illumination area.

11. The plate of claim 10, wherein one of the plurality of markers, a first marker, is located at or near a first end of the marker area, one of the plurality of markers, a second marker, is located at or near a second end of the marker area away from the first end, and the other markers of the plurality of markers are distributed between the first marker and the second marker.

12. The board as requested in claim 10, wherein adjacent markers among the plurality of markers are staggered between the markers of the first type and the markers of the second type.

13. A plate system for use in an imaging system to determine at least two optical properties of an illumination beam of the imaging system configured to illuminate an illumination area with the illumination beam, the plate system comprising a first plate and a second plate, each as claimed in any one of claims 10 to 12, wherein: On the first board, the first subset of the plurality of markers is located at a set of first positions, and the second subset of the plurality of markers is located at a set of second positions; on the second board, the first subset of the plurality of markers is located at a set of second positions, and the second subset of the plurality of markers is located at a set of first positions; the first positions of the first board correspond to the first positions of the second board, and the second positions of the first board correspond to the second positions of the second board.

14. A plate system for use in an imaging system to determine at least two optical properties of an illumination beam of the imaging system, the plate system comprising a first plate, a second plate, and a third plate, each as claimed in any one of claims 10 to 12, wherein: On the first board, a first subset of the plurality of markers is located at one set of first positions, and a second subset of the plurality of markers is located at one set of second positions; the first board further includes one set of third positions that do not contain markers; on the second board, a first subset of the plurality of markers is located at one set of second positions, and a second subset of the plurality of markers is located at one set of third positions; the second board further includes one set of first positions that do not contain markers; on the third board, the ... third subset of the plurality of markers is located at one set of third positions; the second board further includes one set of first positions that do not contain markers; the first subset of the plurality of markers is located at one set of third positions, and a third subset of the plurality of markers is located at one set of third positions. The first subset is located at one set of third positions, and the second subset of the plurality of markers is located at one set of first positions; the third board further includes one set of second positions that do not contain markers; the first positions of the first board correspond to the first positions of the second board and the first positions of the third board; the second positions of the first board correspond to the second positions of the second board and the second positions of the third board; and the third positions of the first board correspond to the third positions of the second board and the third positions of the third board.

15. A plate system for use in an imaging system to determine an optical property of an illumination beam of the imaging system, the imaging system being configured to illuminate an illumination area with the illumination beam, the plate system comprising: a first plate comprising: at least three first markers for determining the optical property of the illumination beam, the at least three first markers being located at a set of first positions; and a set of second positions not containing markers; a second plate comprising: a plurality of second markers for determining the optical property of the illumination beam, the plurality of second markers being located at a set of second positions corresponding to the set of second positions of the first plate; and a set of first positions not containing markers; wherein the set of first positions of the second plate corresponds to the set of first positions of the first plate, wherein the at least three first markers are located in a first marker region substantially corresponding to the illumination area, such that the at least three first markers are illuminated together by the illumination beam; and wherein the plurality of second markers are located in a second marker region substantially corresponding to the illumination area.

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