Method and lithographic apparatus for measuring a radiation beam

Abstract

The present invention provides a device comprising a projection system, the projection system having an optical axis and being configured to project a radiation beam. The device comprises a measuring unit arranged to measure the radiation beam projected by the projection system, the measuring unit comprising an opening, through which the radiation beam passes when in use, and a sensing surface, the sensing surface extending transversely to the optical axis and being arranged to measure the radiation beam passing through the opening. The lithographic device is configured to move the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions. The radiation beam defines a view in the above-mentioned plane, and the measuring unit is configured so that the sensing surface captures a portion of the view at each measurement position, the portion being smaller than 100% of the view. The present invention comprises a corresponding method.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 19156895.5 filed on February 13, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] The invention relates to a method and a lithographic apparatus for measuring a radiation beam. Background Art

[0004] A lithographic apparatus is a machine that applies a desired pattern to a substrate or a portion of a substrate. For example, a lithographic apparatus can be used to manufacture flat panel displays, integrated circuits (ICs), and other devices involving fine structures. In conventional equipment, a patterning device, which may be referred to as a mask or reticle, can be used to generate circuit patterns corresponding to individual layers of a flat panel display (or other device). The pattern can be transferred to all or part of a substrate (e.g., a glass plate) by imaging onto a layer of radiation-sensitive material (e.g., a resist) disposed on the substrate.

[0005] Instead of a circuit pattern, a patterning device can be used to generate other patterns, such as a color filter pattern or a dot matrix. Instead of a mask, a patterning device can be a patterned array comprising an array of individually controllable elements. In such a system, patterns can be changed faster and at a lower cost than in a mask-based system. The shape of a flat panel display substrate is typically rectangular. A lithography device designed to expose this type of substrate can provide an exposure area covering the entire width of a rectangular substrate or covering a portion of the width (e.g., half of the width). The substrate can be scanned below the exposure area while the mask or mask is scanned synchronously by a light beam. In this way, the pattern is transferred to the substrate. If the exposure area covers the entire width of the substrate, the exposure can be completed by a single scan. If the exposure area covers, for example, half of the width of the substrate, the substrate can be moved laterally after the first scan, and further scans are typically performed to expose the remainder of the substrate.

[0006] Photolithography involves projecting a pattern onto a substrate with high precision. To ensure that the projection is achieved with high precision, various calibration measurements are performed within the apparatus. In some cases, the apparatus is adjusted in response to these measurements.

[0007] It is known that image sensors can be used to measure lens aberrations and intensity distribution in the pupil plane of the illuminator. Such sensors can consist of a top plate that transmits light from the projection lens through a grating or pinhole and a sensor placed at a conjugate pupil plane to record the light spot. The resolution of the light that can be measured depends on the angular resolution of the sensor. The resolution is limited by the number of pixels and the available space of the sensor.

[0008] As the development of lithography tools has advanced, the demands on projection optics have increased, requiring tighter aberration control to achieve better imaging. In order to provide improved correction techniques, high spatial resolution wavefront measurements may be required to match the necessary resolution to provide advanced high resolution lithography tools. Such high spatial resolution wavefront measurements may be particularly beneficial for measuring the illumination pupil during the setup of a lithography apparatus.

[0009] The resolution that can be used for such a sensor may be limited for a number of reasons, but in particular due to the number of pixels of the sensor and the space available for the sensor. Since a higher resolution is preferred, either smaller pixels are required or the spot size should be increased by placing the detector further away from the mark used in the sensor. However, both solutions have their limitations. If the pixel size is too small, crosstalk may occur between the pixels, thereby reducing the measurement quality of the sensor. For this type of sensor, there are also geometrical limitations on the space available and it may not be possible to increase the distance between the sensor and the mark. In addition, the type of sensor used is often commercially available (i.e., off-the-shelf detectors). Therefore, it is advantageous to use sensor technology that is already available or even already used to provide a solution in a more advantageous manner. Summary of the invention

[0010] In the present invention, a lithography device is provided, which includes: a projection system having an optical axis and configured to project a radiation beam; a measuring unit arranged to measure the radiation beam projected by the projection system, the measuring unit including: an opening through which the radiation beam passes when in use; and a sensing surface extending transversely to the optical axis and arranged to measure the radiation beam passing through the opening, wherein the lithography device is configured to move the sensing surface in a plane transverse to the optical axis between multiple measurement positions, wherein the radiation beam defines a view in the above-mentioned plane, and wherein the measuring unit is configured so that the sensing surface captures a portion of the view at each measurement position, the portion being smaller than 100% of the view.

[0011] According to the present invention, a method for measuring a radiation beam in a lithography device is also provided, the method comprising: providing a radiation beam; projecting the radiation beam through an opening in a measuring system using a projection system having an optical axis; and measuring the radiation beam that has passed through the opening at multiple measurement positions using a sensing surface of the measuring system, the sensing surface extending transversely to the optical axis; wherein measuring the radiation beam comprises: moving the sensing surface in a plane transverse to the optical axis between the multiple measurement positions, wherein the radiation beam defines a view in the above-mentioned plane, and wherein the sensing surface captures a portion of the view at each measurement position, the portion being smaller than 100% of the view.

[0012] Other embodiments, features, and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate one or more embodiments of the invention and, together with the description, further serve to explain the principles of the invention and enable a skilled person to make and use the relevant techniques of the invention.

[0014] Figure 1 A lithographic apparatus is schematically depicted.

[0015] Figure 2A and Figure 2B A known measuring sensor is schematically depicted.

[0016] Figure 3A , Figure 3B , Figure 3C and Figure 3D The apparatus of an embodiment is schematically depicted.

[0017] Figure 4A and Figure 4B The apparatus of an embodiment is schematically depicted.

[0018] Figure 5 and Figure 6 A method according to an embodiment is described.

[0019] One or more embodiments of the present invention will now be described with reference to the accompanying drawings.In the drawings, like reference numbers may indicate identical or functionally similar elements. DETAILED DESCRIPTION

[0020] This specification discloses one or more embodiments that incorporate features of the present invention. The disclosed embodiments merely illustrate the present invention. The scope of the present invention is not limited to the disclosed embodiments. The present invention is defined by the appended claims.

[0021] The described embodiments and references in the specification to "one embodiment", "an embodiment", "an example embodiment", etc. indicate that the described embodiments may include certain features, structures, or characteristics, but every embodiment does not necessarily include the certain features, structures, or characteristics. Moreover, these phrases do not necessarily refer to the same embodiment. Furthermore, when a certain feature, structure, or characteristic is described in conjunction with an embodiment, it should be understood that it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0022] Figure 1A lithographic apparatus is schematically depicted. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., UV radiation or any other suitable radiation), a patterning device support or support structure (e.g., mask stage) MT configured to support a patterning device (e.g., mask) MA, and connected to a first positioning device PM, the first positioning device PM being configured to accurately position the patterning device according to certain parameters. The lithographic apparatus also comprises a substrate table (e.g., wafer stage) WT or "substrate support" configured to hold a substrate (e.g., a wafer coated with a resist) W and connected to a second positioning device PW, the second positioning device PW being configured to accurately position the substrate according to certain parameters. The substrate support may comprise a substrate table WT (also referred to as a chuck), on which a substrate holder is supported. The substrate holder may be configured to support a substrate W. The apparatus also comprises a projection system (e.g., a refractive projection lens system) PS, which is configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0023] The illumination system IL may include various types of optical components for directing, shaping or controlling the radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof.

[0024] The patterning device support supports the patterning device MA in a manner that depends on the orientation of the patterning device MA, the design of the lithographic equipment, and other conditions (such as, for example, whether the patterning device MA is maintained in a vacuum environment). The patterning device support can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The patterning device support can be, for example, a frame or a stage, which can be fixed or movable as required. The patterning device support can ensure that the patterning device MA is in a desired position, for example, relative to the projection system PS. Any use of the term "reticle" or "mask" herein can be considered to be synonymous with the more general term "patterning device".

[0025] The term "patterning device" as used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section so as to produce a pattern in a target portion of the substrate W. It should be noted that the pattern imparted to the radiation beam B may not exactly correspond to the desired pattern in the target portion of the substrate W, for example if the pattern includes phase-shifting features or so called assist features. Typically, the pattern imparted to the radiation beam B will correspond to a specific functional layer in a device produced in the target portion, such as an integrated circuit.

[0026] The patterning device MA can be transmissive or reflective. Examples of patterning devices MA include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary, alternating phase shift, and attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam reflected by the mirror matrix.

[0027] The term "projection system" as used herein should be broadly interpreted as covering any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, depending on the exposure radiation used or other factors, such as the use of immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system".

[0028] As depicted herein, the device is transmissive (eg, employing a transmissive mask). Alternatively, the device may be reflective (eg, employing a programmable mirror array of the type described above, or employing a reflective mask).

[0029] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables or "substrate supports" (and / or two or more mask tables or "mask supports"). In such a "multi-stage" machine, the additional tables or supports may be used in parallel, or preparatory steps may be performed on one or more tables or supports while exposure is being carried out on the other tables or supports.

[0030] The lithographic apparatus may also be of a type in which at least a portion of the substrate W may be covered by a liquid having a relatively high refractive index (e.g., water) to fill the space between the projection system PS and the substrate W. Immersion liquid may also be applied to other spaces in the lithographic apparatus, such as between the patterning device (e.g., mask) MA and the projection system PS. Immersion techniques may be used to increase the numerical aperture of the projection system. The term "immersion" as used herein does not imply that structures such as the substrate must be immersed in the liquid, but only that the liquid is located between the projection system PS and the substrate W during exposure.

[0031] refer to Figure 1, the illuminator IL receives a radiation beam B from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In this case, the source is not regarded as forming part of the lithographic apparatus, and the radiation beam B is transferred from the source SO to the illuminator IL with the aid of a beam delivery system BD, which comprises, for example, suitable directional mirrors and / or a beam expander. In other cases, the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL together with the beam delivery system BD (if necessary) may be referred to as a radiation system.

[0032] The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial extent (commonly referred to as outer σ and inner σ, respectively) of the intensity distribution in a pupil plane of the illuminator may be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to adjust the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

[0033] The radiation beam B is incident on a patterning device (e.g. a mask) MA held on a mask support structure (e.g. a mask table) MT and is patterned by the patterning device MA. After passing through the patterning device (e.g. a mask) MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of the substrate W. With the aid of a second positioning device PW and a position sensor IF (e.g. an interferometric device, a linear encoder or a capacitive sensor), the substrate table WT can be accurately moved, for example in order to position different target portions C in the path of the radiation beam B. Similarly, the first positioning device PM and a further position sensor (in Figure 1The first positioning device PM (not explicitly depicted in the figure) can be used to accurately position the patterning device (e.g., mask) MA relative to the path of the radiation beam B, for example after mechanical retrieval from a mask library, or during scanning. Typically, movement of the patterning device support (e.g., mask table) MT can be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) that form part of the first positioning device PM. Similarly, movement of the substrate table WT or "substrate support" can be achieved using a long-stroke module and a short-stroke module that form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the patterning device support (e.g., mask table) MT may be connected only to the short-stroke actuator, or may be fixed. The patterning device (e.g., mask) MA and the substrate W may be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks as shown occupy dedicated target portions, they may be located in the spaces between target portions (these are referred to as scribe alignment marks). Similarly, where more than one die is provided on the patterning device (eg, mask) MA, the patterning device alignment marks may be located between the dies.

[0034] The depicted device can be used in at least one of the following modes:

[0035] 1. In step mode, the patterning support (e.g. mask table) MT or "mask support" and the substrate table WT or "substrate support" remain substantially stationary while the entire pattern imparted to the radiation beam B is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT or "substrate support" is then moved in the X and / or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C that is imaged in a single static exposure.

[0036] 2. In scan mode, the patterning device support (e.g. mask table) MT or "mask support" and the substrate table WT or "substrate support" are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (i.e. a single dynamic exposure). The speed and direction of the substrate table WT "substrate support" relative to the patterning device support (e.g. mask table) MT or "mask support" may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width of the target portion in a single dynamic exposure (in the non-scanning direction), while the length of the scanning movement determines the height of the target portion (in the scanning direction).

[0037] 3. In another mode, the patterning device (e.g., mask table) MT or "mask support" is kept substantially stationary to hold the programmable patterning device, and the substrate table WT or "substrate support" is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, a pulsed radiation source is typically employed and the programmable patterning device is updated as required after each movement of the substrate table WT or "substrate support" or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography utilizing a programmable patterning device, such as a programmable mirror array of the type described above.

[0038] Combinations and / or variations of the above-described modes of use or entirely different modes of use may also be employed.

[0039] As described above, measurements can be performed to reduce errors in the radiation beam B incident on the substrate W. Known sensors can be used to perform calibration measurements of the radiation beam B projected by the projection system PS. One such calibration measurement performed in a lithographic apparatus is to measure the aberrations present in the radiation beam projected by the projection system PS. However, there are limitations on the resolution of known sensors that perform such measurements. As described above, the resolution may be limited by the number of pixels in the sensor and / or the available space for the sensor. For example, the number of pixels may be limited by the sensor technology and / or the cost of the sensor to be used. Depending on the location of the sensor, the space available for the sensor may be limited.

[0040] It would therefore be beneficial to provide an apparatus and method for measuring a radiation beam in a lithographic apparatus.Ideally, the apparatus and method of the present invention may be used to provide improved measurements in a lithographic apparatus.

[0041] The present invention relates to a lithographic apparatus such as described above. The lithographic apparatus may include some or all of the features described above. The lithographic apparatus may not be limited to including all of the features described above.

[0042] The lithographic apparatus comprises a projection system having an optical axis and configured to project a radiation beam. The projection system of the lithographic apparatus may be configured as described in the above examples or may be configured in other ways. Typically, the projection system is any system for projecting a radiation beam. The radiation beam may be the same as the radiation beam B described above.

[0043] The optical axis may be understood to have the general meaning of a line along which there is a certain degree of rotational symmetry in an optical system (i.e., a projection system). The optical axis may not necessarily pass through a central axis of the projection system. A radiation beam projected by the projection system may be along the optical axis. Thus, the optical axis may be the axis along which the projection system projects the radiation beam.

[0044] The lithographic apparatus further comprises a measuring unit arranged to measure a radiation beam projected via the projection system. The measuring unit comprises an opening through which the radiation beam passes when in use. The measuring unit further comprises a sensing surface extending transversely to the optical axis. The sensing surface is arranged to measure the radiation beam passing through the opening. The sensing surface can be positioned relative to the optical axis so that the radiation beam passing through the opening is incident on the sensing surface. Thus, the sensing surface is downstream of the opening so that the radiation beam passes through the opening and then is incident on the sensing surface.

[0045] The sensing surface is transverse to the optical axis means that the sensing surface extends across the optical axis. Therefore, the sensing surface is not parallel to the optical axis. In addition, the sensing surface is positioned so that the optical axis passes through the sensing surface. For example, the sensing surface can be orthogonal to the optical axis. However, this is not required, and the sensing surface can be tilted relative to the optical axis in some way, that is, the angle between the sensing surface and the optical axis is greater than 0° and less than 90°.

[0046] The lithographic apparatus is configured to move the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions. Therefore, the plane in which the sensing surface is moved is not parallel to the optical axis, i.e. not only in a direction parallel to the optical axis. In other words, at least one component of the movement of the sensing surface between a plurality of measurements is not parallel to the optical axis, i.e. there is a component of movement perpendicular to the optical axis, and optionally, there is a component of movement parallel to the optical axis. In addition, the plane is positioned so that the optical axis passes through the plane. Preferably, the plane in which the sensing surface is moved is orthogonal to the optical axis. This can allow measurements to be made in a more easily handled manner, since the measurements will be made at a set distance from the opening. However, this is not required, and the plane can be tilted relative to the optical axis in some way, i.e. the angle between the plane and the optical axis is greater than 0° and less than 90°.

[0047] As will be described in further detail below, the sensing surface can be moved to different measurement positions to measure the radiation beam incident on the sensing surface at the measurement position. The sensing surface can be moved in a variety of ways. The sensing surface can be moved relative to the radiation beam, i.e. along the optical axis as described above.

[0048] The radiation beam defines a view in the plane in which the sensing surface moves. This means that a cross section through the radiation beam in the plane provides the view. The radiation beam can be measured by the sensing surface in the plane. It will be appreciated that the intensity of the radiation beam can vary throughout the view.

[0049] The measuring unit is configured such that the sensing surface captures a portion of the view at each measuring position which is smaller than 100% of the view. In other words, the sensing surface is smaller than 100% of the view in the plane in which the sensing surface is moved. Therefore, if a cross section of the radiation beam is taken in the plane in which the sensing surface is moved, the cross-sectional area of ​​the radiation beam (i.e., 100% of the view) will be larger than the cross-sectional area of ​​the sensing surface. This means that at any time, i.e. when the sensing surface is in one measuring position, only a portion of the radiation beam, but not all of it, is incident on the sensing surface. As described above, the sensing surface is moved to different measurement positions in the plane so that multiple measurements of the radiation beam can be performed over the entire plane. 100% of the view may also be referred to as the entire view.

[0050] Providing a measurement unit configured in this way is beneficial because measurements with higher resolution can be made than using known sensors. In more detail, since the sensing surface is used to measure smaller portions of the radiation beam than with known sensors, this means that measurements of the radiation beam can be made with higher resolution using the same sensing surface (i.e. having the same number of pixels and sensing surface size). Alternatively, if such an improvement in resolution does not provide a great benefit to the user, the user may replace an existing system with the present invention and measurements of the same resolution may be performed using a smaller volume of the measurement unit. Alternatively, if such an improvement in resolution does not provide a great benefit to the user, the user may replace an existing system with the present invention and measurements of the same resolution may be performed using larger pixels (e.g. a cheaper sensing surface), which will provide more accurate measurements due to reduced pixel crosstalk and lower noise.

[0051] The sensing surface may be part of a sensor. The sensing surface may be substantially flat or may be curved. The sensing surface may be flat, but may be provided at an angle (not parallel or orthogonal) to the optical axis, i.e., the sensing surface may be inclined. The sensing surface may have any suitable shape. The figures described below show the sensing surface as a square or a rectangle. However, the sensing surface is not limited to a specific shape. The sensing surface is a part of a sensor capable of measuring a radiation beam. That is, the radiation beam will be incident on a part of the sensor, which is used to measure the radiation beam. Various different types of sensing surfaces / sensors may be used. For example, the sensing surface may be part of a charge coupled device (CCD) and / or a complementary metal oxide semiconductor (CMOS) sensor. The sensor may be further referred to as a detector or a sensing unit. Any sensor or detector that may be configured to capture light intensity may be used. The sensing surface may be provided by a plurality of units and / or discrete sensing devices. For example, the sensing surface may be formed by strips of photosensitive devices.

[0052] As described above, the lithographic apparatus is configured to move the sensing surface. Thus, the lithographic apparatus may be arranged to change the position of the sensing surface, and in particular to move the sensing surface between a plurality of measurement positions. The sensing surface may thus acquire measurements of a plurality of portions of the radiation beam in the plane in which the sensing surface is moved. This is beneficial because it means that a larger portion of the radiation beam in the plane may be measured with a higher resolution.

[0053] The position of the sensing surface can be moved relative to the radiation beam. The lithographic apparatus can be configured to maintain the position of the radiation beam projected by the projection system at a substantially constant position when the sensing surface is configured to measure the radiation beam at a plurality of measurement positions. Thus, the position of the radiation beam can be maintained substantially constant and the position of the sensing surface can be changed. The movement of the sensing surface will be described in more detail below. In this way, the sensing surface can be used to measure different portions of the radiation beam in the plane in which the sensing surface is moved. The portion of the radiation beam that is measured can be determined based on the position of the sensing surface at which the measurement is performed.

[0054] The lithographic apparatus may include a support table as described above. The support table may be configured to support a substrate W, for example, the support table may be a substrate table WT as described above. The measurement unit may be arranged on the support table. Thus, the measurement unit may be supported on a surface of the support table. The measurement unit may form a part of the support table.

[0055] The lithographic apparatus can be configured to move the sensing surface by moving the support table. The lithographic apparatus can be configured to move the sensing surface in a variety of different ways. If the sensing surface (and more generally, the measuring unit) is supported by a support table, the movement of the support table can move the position of the sensing surface (and the measuring unit). For example, the lithographic apparatus may include a positioner and a sensor configured to accurately move the support table, such as a second positioner PW and a position sensor IF. As described above, the positioner may optionally include a long-stroke module and a short-stroke module to accurately position the support table and thereby accurately position the sensing surface. If the sensing surface is disposed on or as part of any other support, similar components may be used to accurately position the support and / or the sensing surface.

[0056] Additionally or alternatively, the position of the sensing surface can be controlled independently of the support on which the sensing surface is placed. Thus, the lithographic apparatus can be configured to move the sensing surface relative to the support. For example, as further described below, the lithographic apparatus can include an actuator configured to move the measurement unit. Additionally or alternatively, the sensing surface can be moved separately from other components of the measurement unit. For example, at least one actuator (not shown) can be provided to move the sensing surface relative to other components of the measurement unit and / or the radiation beam.

[0057] In theory, the position of the sensing surface could be kept constant and the radiation beam could be moved. This would provide the same advantage, as different parts of the radiation beam's view in the plane could thus be measured.

[0058] Preferably, at least a portion of the portion of the view captured by the sensing surface in one measurement position does not overlap with a portion of the view captured by the sensing surface in any of the other measurement positions. In other words, the sensing surface can be used to measure at least one different unmeasured area of ​​the radiation beam in the view at each measurement position. Thus, at each measurement position, the sensing surface can measure a portion of the radiation beam that was not measured when the sensing surface was in any other measurement position. This is beneficial because it means that a larger portion of the entire view can be measured by the sensing surface at different measurement positions because each measurement position captures at least one new portion of the view that was not measured at the other measurement positions. Reducing overlap increases angular resolution. Angular resolution can also be increased by increasing the number of apertures.

[0059] Preferably, there may be some overlap between portions of the views captured by the sensing surface at different measurement positions. More preferably, there is a selected amount of overlap between views measured at adjacent measurement positions. It may be advantageous for views measured when the sensing surface is in different measurement positions to have a certain amount of overlap, as this may help improve accuracy by allowing comparison of measurements made at different measurement positions. Overlapping measurements may be used to correct for changes over time and improve the accuracy of the measurements. The amount of overlap may be controlled by controlling the movement of the sensing surface and / or by selecting the position of the openings relative to each other (if multiple openings are provided and / or by selecting the position of the sensing surface relative to the openings).

[0060] Ideally, the sensing surface is moved to different measurement positions so that at least a portion of the views being measured do not overlap, and there is a selected amount of overlap to ensure accurate measurement as described above. In other words, the sensing surface is moved to different measurement positions so that at most a portion of the view being measured, such as at most 10% or 50% of the view, overlaps with one or more portions of the view captured by the sensing surface at any other measurement position.

[0061] The lithographic apparatus may be configured to combine portions of views captured at multiple measurement positions. In this way, the lithographic apparatus may be used to combine measurements of various different portions of a radiation beam. Ideally, the lithographic apparatus may be configured to combine these portions to provide a measurement of 100% of the view in the plane described above. This may be beneficial because measurements may be made across the entire radiation beam in the plane in which the sensing surface is moved. Because the measurement made by the sensing surface is not 100% of the view, this means that the measurement of the radiation beam is smaller than the view, which means that the resolution of the measurement is higher than when a similar sensing surface is used to capture the entire view at one measurement position. This means that a more accurate measurement across the entire radiation beam may be provided. In this way, improved measurements may be made while still using the same sensing surface as may be used in a known sensing device.

[0062] The lithographic apparatus may include a processor configured to combine portions of views captured at multiple measurement positions. The processor may receive data representing views captured by the sensing surface from the sensing surface. The data may be sent from the sensing surface to the processor over a network (i.e. wirelessly) or using wires. The processor may be any suitable computing device / electronic circuit that may be used to receive and combine data.

[0063] The distance between the opening and the sensing surface is such that 100% of the view in the above plane has an area larger than the sensing surface, i.e. the total area of ​​the sensing surface. In other words, the sensing surface can be positioned relative to the opening such that the view of the radiation beam in the above plane is larger than the sensing surface. For a given size of the opening and the sensing surface, there may be a minimum predetermined distance. Thus, the distance may vary depending on at least these factors.

[0064] The sensing surface (i.e., the total area of ​​the sensing surface) can be less than or equal to about 70% of the area of ​​100% of the view. Thus, in any measurement position, the sensing surface can be used to measure less than or equal to about 70% of the radiation beam in the plane in which the sensing surface is moved, i.e., less than or equal to about 70% of the entire view. Alternatively, the area of ​​the sensing surface can be smaller. For example, the sensing surface can be less than or equal to about 60% of the area of ​​100% of the view, or less than or equal to about 50% of the area of ​​100% of the view, or less than or equal to about 30% of the area of ​​100% of the view.

[0065] The openings may be provided in a number of different configurations. The openings may be simply holes through the plate, as described later, or slits or a set of lines. The openings may be of any suitable shape and size. If the openings are slits, this means that the sensor surface can only move in one direction, resulting in a continuous or discontinuous scanner motion. The openings may optionally be a 1D or 2D pattern and may preferably comprise a grating. The grating may be of any suitable form. For example, the grating may be a 1D pattern or a 2D pattern, such as a chessboard pattern with a predetermined spacing.

[0066] The measuring unit may comprise a plate, wherein the plate forms an opening. The plate may have any suitable number of openings. For example, the plate may comprise a single opening or a plurality of openings, as will be further described. The plate may provide the opening by having a through hole through which radiation may pass. As described above, the plate may comprise some form of grating in the opening. The plate may be any element of any suitable shape and thickness to form an opening through which a radiation beam may pass to reach the sensing surface.

[0067] Just as a side comparison, Figure 2A and 2B A sensor that may have been previously used in the prior art is depicted in FIG. Figure 2A A schematic diagram in the XY plane is shown, which can also be regarded as a plan view. Figure 2B A schematic diagram in the ZX plane is shown, which can also be considered as a side view. As shown, the sensor includes a plate PL forming an opening O and a sensing surface S. A light beam B passes through the opening O and forms a radiation cone in the sensor. Although a radiation cone is generated and shown here, this is only an example and any shape of light beam can be measured. The sensing surface S is used to measure the radiation beam. The view of the radiation beam B in the plane of the sensing surface S is smaller than the sensing surface. Therefore, in the case of Figure 2A and 2B With a single measurement position shown, the sensing surface S captures the entire view V, ie 100% of the view. Having said this, we now return to the present invention.

[0068] In one embodiment, the measuring unit comprises a plurality of openings through which the radiation beam passes when in use, and one of the openings is used in each measuring position. This means that when the sensing surface is in each measuring position, the radiation beam passes through one of the plurality of openings and is incident on the sensing surface. Preferably, the plurality of openings are in fixed positions relative to the sensing surface. Thus, the sensing surface and the plurality of openings do not move relative to each other. This embodiment is Figure 3A , Figure 3B , Figure 3C and Figure 3D. These figures depict a measurement unit M configured such that the sensing surface S captures a portion of the view at each measurement position that is smaller than 100% of the view. The entire view V of the radiation beam B in the plane of the sensing surface S is shown as being larger than the area of ​​the sensing surface S.

[0069] As mentioned above, the lithographic apparatus may include a projection system PS (eg Figure 3C and Figure 3D ). A radiation beam B is projected by a projection system PS and is incident on a sensing surface S. The sensing surface S is configured to measure a portion of the view at each measurement position, the portion being smaller than 100% of the view. Figure 3A and Figure 3B A measuring unit M, more specifically a sensing surface S, is depicted moving between a first 1 , a second 2 , a third 3 and a fourth 4 measuring position. Figure 3C and Figure 3D The first measuring position 1 and the second measuring position 2 are shown in more detail.

[0070] The measuring system M may include a plurality of openings O1, O2, O3, O4 as shown in the figure, through which the radiation beam passes when in use. One of the plurality of openings can be used at each measuring position. The measuring system M may include a plate PL as described above, which includes a plurality of openings. As shown in these figures, four openings O1, O2, O3, O4 are depicted at a distance Z1 from the sensing surface S. As shown, the four openings O1, O2, O3, O4 are located in a plane parallel to the sensing surface S, so that the distance Z1 from the sensing surface S to each of the plurality of openings O1, O2, O3, O4 is the same. There may be any number of suitable openings. The number of openings may vary and the distance of each opening to the sensing surface S may be different from the other openings.

[0071] The plurality of openings O1, O2, O3, O4 may be in a fixed position relative to the sensing surface S, for example, a plate PL comprising the openings may be connected to the sensing surface S in some way. The measurement unit M may comprise a housing H supporting the sensing surface S and a plate PL having the openings O1, O2, O3, O4. The sensing surface S and the plate PL may be attached to the housing H such that these components have a fixed position relative to each other. In this embodiment, the openings O1, O2, O3, O4 are moved relative to the radiation beam B in the same way as the sensing surface S is moved relative to the radiation beam B. Although a housing H is depicted in the figures, the sensing surface S and the openings O1, O2, O3, O4 may be provided as part of a support such as a substrate table WT, which may hold the openings O1, O2, O3, O4 and the sensing surface S in a fixed position relative to each other.

[0072] One of the plurality of openings may be used at each measurement position. Thus, when measuring at one of the measurement positions, the radiation beam B may pass through one of the plurality of openings O1, O2, O3, O4 and be incident on the sensing surface S. When the sensing surface S and the opening O move relative to the radiation beam B, the radiation beam B may pass through different openings O and be incident on the sensing surface S to perform measurements at different measurement positions. Thus, there may be one opening corresponding to each measurement position.

[0073] As described above, the lithographic apparatus is configured to move the sensing surface S in a plane transverse to the optical axis OA of the projection system PS. Figure 3A and 3B The measuring unit M is shown with a change of position in the measuring positions 1-4. In the figure, the sensing surface S is moved in an XY plane orthogonal to the optical axis OA, purely as an example. As mentioned above, this is not essential.

[0074] The position of the sensing surface S (and in this example the entire measurement unit M) can be moved relative to the projection beam B so that different parts of the entire view V of the radiation beam B in the plane in which the sensing surface S is moved can be measured. Figure 3A As shown, there is little or no overlap between the measurements made by the sensing surface S at the first measurement location 1, the second measurement location 2, the third measurement location 3 and the further measurement location 4. As mentioned above, some overlap may be beneficial.

[0075] In this embodiment, the lithographic apparatus is configured to move the sensing surface S within the above-mentioned plane and relative to the radiation beam B projected by the projection system PS to acquire measurements at a plurality of measurement positions. The lithographic apparatus may be configured to maintain the position of the radiation beam B projected by the projection system PS at a substantially constant position for measurements at a plurality of measurement positions.

[0076] exist Figure 3A and 3B, four measurement positions are shown from left to right. At the first measurement position 1 (the one on the left), the sensing surface S captures a portion of the view in which the radiation beam has passed through the first opening O1. At the second measurement position 2, the sensing surface S captures a portion of the view in which the radiation beam has passed through the second opening O2. At the third measurement position 3, the sensing surface S captures a portion of the view in which the radiation beam has passed through the third opening O3. At the fourth measurement position 4, the sensing surface S captures a portion of the view in which the radiation beam has passed through the fourth opening O4. The lithographic apparatus of this embodiment can be configured to move the sensing surface S relative to the radiation beam to each of the measurement positions (1-4) to obtain a measurement of the radiation beam B through each of the openings O1, O2, O3, O4. Therefore, each of the multiple openings O1, O2, O3, O4 can correspond to a measurement position. In this embodiment, the multiple openings O1, O2, O3 and O4 can also be moved relative to the radiation beam in association with moving the sensor surface between the multiple measurement positions. The multiple openings can be moved simultaneously or non-simultaneously with the sensing surface. Additionally or alternatively, the plurality of openings may be moved the same distance as the sensing surface or a different distance than the sensing surface is moved.

[0077] The plurality of openings may be arranged at fixed positions relative to each other. Alternatively, the plurality of openings may be arranged at movable positions relative to each other, or may be arranged to move in groups relative to one or more other groups of openings of the plurality of openings.

[0078] The plurality of openings O1, O2, O3, O4 may be arranged such that at each measurement position at least one opening is outside the radiation beam, i.e. outside 100% of the view V in plan view. This means that the radiation beam does not pass through at least one opening outside the entire view V. This may reduce the noise generated for a specific measurement position due to radiation passing through a plurality of openings. This is particularly useful in Figure 3A Described in , the third opening O3 is outside the radiation beam (and the entire view V in the plane) at the first measurement position 1, the fourth opening O4 is outside the radiation beam (and the entire view V in the plane) at the second measurement position 2, the first opening O1 is outside the radiation beam (and the entire view V in the plane) at the third measurement position 3, and the second opening O2 is outside the radiation beam (and the entire view in the plane) at the fourth measurement position 4.

[0079] Alternatively, if Figure 3C and Figure 3DAs shown, the lithographic device may include a mask MK, which is configured to mask all openings except the opening at each measurement position in a plurality of openings. This can prevent or reduce radiation from entering the measurement unit via other openings during such measurement. This may be beneficial in reducing noise by ensuring that the radiation beam incident on the sensing surface passes only through one of the openings. This reduces the possibility of errors caused by providing multiple openings and reduces noise. The mask MK can be made of any suitable material. The mask MK should be made of a material that can substantially prevent radiation from passing through the mask. Although the mask MK can ideally mask all openings except one of the openings, the mask MK can be used only to mask one or more of the openings, for example, the opening closest to the opening used at a specific measurement position. The position of the mask MK can be controlled in the form of an actuator (not shown).

[0080] As described above, the openings may include gratings. In this embodiment, at least one of the plurality of openings may include gratings. All openings may include gratings. The gratings may be identical. This may be beneficial because measurements made through different openings may be more easily compared and / or manufacturing may be easier and therefore cheaper for identical gratings.

[0081] In any of the above embodiments, the sensing surface S may be offset in plan view from the opening through which the radiation beam B passes in use. This means that in plan view, for example Figure 3A In the XY view shown, the sensing surface S is not aligned with the opening through which the radiation beam passes at any measurement position. In other words, when taking a measurement, the center point of the sensing surface S may not be aligned with the center point of the opening. For example, at the first measurement position 1, the sensing surface S is offset from the first opening O1 through which the radiation beam passes.

[0082] In another embodiment, the measurement unit may comprise only a single opening through which the radiation beam passes when in use. In this embodiment, the lithographic apparatus may be configured to maintain the position of the single opening relative to the radiation beam projected by the projection system between measurements at each of the plurality of measurement positions. In this embodiment, Figure 4A and Figure 4B As described above, the lithographic apparatus may be configured to move the sensing surface S in a plane transverse to the optical axis between a plurality of measurement positions. Figure 4A and Figure 4B The lithographic apparatus may be configured to maintain the position of a single opening O5 at a substantially constant position, such as Figure 4A and Figure 4B The constant positions between the measurement positions 1-5 are shown as indicated.

[0083] In this embodiment, a plate PL comprising only a single opening O5 may be provided. In this embodiment, the sensing surface S is moved relative to the other components of the measurement unit M. In each measurement position, the sensing surface S is configured to measure a portion of the view of the radiation beam in a plane transverse to the optical axis in which the sensing surface S is moved, wherein the portion of the view is less than 100% of the view V. The position of the radiation beam B and the single opening O5 is maintained in a substantially constant position and the sensing surface S is moved to different measurement positions 1-5. The sensing surface S then measures a different portion of the radiation beam B in each measurement position 1-5. There may be some overlap in the portion of the view measured in each of the measurement positions 1-5.

[0084] Lithographic equipment may include Figure 4B The actuator A is shown. The actuator A may be part of a measurement system M. The actuator A may be configured to move the sensing surface S between a plurality of measurement positions, for example Figure 4A and Figure 4B As shown. The actuator A may be provided in any suitable form. For example, the actuator A may include a moving part that supports the sensing surface S and moves along a track within the measurement unit M. The actuator A may include a roller system, similar to a conveyor belt, to move the sensing surface S back and forth in the X direction, such as Figure 4B Any suitable actuator capable of providing a means of moving the sensing surface S on a sufficiently small scale may be used.

[0085] In any embodiment, the sensing surface S can be used to perform measurements at any number of measurement positions. The sensing surface S can be moved in a stepping mode, in which the sensing surface S is moved to the measurement positions and the measurements are performed when the sensing surface S is substantially stationary. Alternatively, the sensing surface can be moved in a scanning mode, for example while the sensing surface S is moved and the measurements are performed during the movement of the sensing surface S. When only a single opening is provided, the sensing surface S can be moved continuously, preferably very slowly, so that measurements can be performed at a specific time, to provide measurements of different measurement positions, i.e. in a scanning mode.

[0086] As described above, the lithographic apparatus may comprise a processor configured to combine portions of views captured at a plurality of measurement positions. Figure 3A , Figure 3B , Figure 3C and Figure 3D The processor PR is depicted in . The processor PR is not Figure 4A or Figure 4B 1, but may also be provided with this embodiment. The processor PR may be located in any convenient place. The processor PR may form part of the substrate table WT.

[0087] The present invention also provides a method for measuring a radiation beam. The method may correspond to the above-mentioned apparatus, as will be described in further detail below. The definitions and descriptions provided in relation to the apparatus may also apply to the method, but are not repeated below for the sake of brevity. The advantages described above with respect to the apparatus also apply to certain steps of the method.

[0088] The method is for measuring a radiation beam in a lithographic apparatus. The method may comprise using a lithographic apparatus as described in any variant and / or embodiment above. The method is as Figure 5 The method comprises providing a radiation beam, as in step S1 , projecting the radiation beam, as in step S2 , and measuring the radiation beam, as in step S3 .

[0089] The radiation beam B may be provided and / or projected as described above. For example, the radiation beam projected by the projection system may be along an optical axis. The radiation beam B may be provided and / or projected using the apparatus described above, or other configurations or apparatus may be used. In general, the projection system PS is any system for projecting the radiation beam B. The method includes projecting the radiation beam through an opening in the measurement system. The measurement system M may be as described in any of the above variants or embodiments.

[0090] The measuring step S3 comprises measuring the radiation beam having passed through the opening at a plurality of measurement positions using a sensing surface of the measurement system.As mentioned above, the sensing surface may extend transversely to the optical axis.

[0091] Measuring the radiation beam includes moving the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions. The plane in which the sensing surface is moved may be orthogonal to the optical axis. As described above, the radiation beam defines a view in the above plane, and the sensing surface captures a portion of the view at each measurement position that is less than 100% of the view.

[0092] In more detail, the measurement step can be considered as having Figure 6 As shown, the method may include measuring a radiation beam projected by a projection system at a first measurement position, as in step S3A, moving the sensing surface in a plane transverse to the optical axis to a second measurement position, as in step S3B, and measuring the radiation beam projected by the projection system at the second measurement position, as in step S3C. Additional movement steps may be included to move the sensing surface to other measurement positions where additional measurements can be performed.

[0093] The method comprises moving the sensing surface so that measurements are performed at a plurality of measurement positions. Thus, the method comprises changing the position of the sensing surface, and in particular moving the sensing surface between a plurality of measurement positions. The sensing surface may thus acquire measurements of a plurality of portions of the radiation beam in the plane in which the sensing surface is moved. The sensing surface may be moved in a plane in a variety of ways as described above.

[0094] The measuring step may comprise maintaining the position of the radiation beam projected by the projection system at a substantially constant position when the sensing surface is measured at a plurality of measurement positions. Thus, the position of the radiation beam may be maintained substantially constant and the position of the sensing surface may be changed. This means that the radiation beam may be maintained at a substantially constant position relative to the moving sensing surface. In this way, the sensing surface may be used to measure different parts of the radiation beam in the plane in which the sensing surface is moved. The part of the radiation beam that is measured may be determined based on the position of the sensing surface at which the measurement is performed.

[0095] Preferably, at least a portion of the portion of the view captured by the sensing surface in one measurement position does not overlap with a portion of the view captured by the sensing surface in any of the other measurement positions. As described above, at least a portion of the non-overlap is beneficial. There may also be an overlap, which may advantageously improve the accuracy of the measurements as described above.

[0096] The openings may be provided in various different configurations as described above. The method may include providing a grating in the above-mentioned openings. The method may include providing any suitable number of openings. As in the examples described for the apparatus, the method may include using a single opening or multiple openings (including the above example, which includes four openings). The measurement system may include a plate forming the above-mentioned openings.

[0097] The method may further comprise providing a support table configured to support the measurement unit.The support table may be as described above.As described above, the measurement unit may be supported on a surface of the support table WT or formed as part of the support table WT.

[0098] The method may also include the step of combining portions of the view captured at a plurality of measurement positions. Ideally, the method includes combining these portions to provide a measurement of 100% of the view. As described above, this means that improved measurements can be made while still using the same sensing surface as might be used in a known sensing arrangement.

[0099] Preferably, the distance between the opening and the sensing surface is such that 100% of the views in the above plane have an area larger than the sensing surface, i.e. the total area of ​​the sensing surface. In other words, the sensing surface may be positioned relative to the opening such that the view of the radiation beam in the above plane is larger than the sensing surface. For a given size of the opening and the sensing surface, there may be a minimum predetermined distance. Thus, the distance may vary depending on at least these factors.

[0100] The sensing surface (i.e., the total area of ​​the sensing surface) may be less than or equal to about 70% of the area of ​​100% of the view. Thus, in any measurement position, the sensing surface may be used to measure less than or equal to about 70% of the radiation beam in the plane in which the sensing surface is moved, i.e., less than or equal to about 70% of the entire view. Alternatively, the area of ​​the sensing surface may be smaller. For example, the sensing surface may be less than or equal to about 60% of the area of ​​100% of the view, or less than or equal to about 50% of the area of ​​100% of the view, or less than or equal to about 30% of the area of ​​100% of the view.

[0101] In one embodiment, the measuring unit includes a plurality of openings through which the radiation beam passes when in use. One of the plurality of openings is used at each measurement position. Therefore, when measuring at the measurement position, the radiation beam can pass through one of the openings and be incident on the sensing surface. In this embodiment, the method also includes moving the plurality of openings and the sensing surface relative to the radiation beam between measurements at each of the plurality of measurement positions. When the sensing surface and the openings move relative to the radiation beam, the radiation beam can pass through different openings and be incident on the sensing surface to be measured at different measurement positions. Therefore, there can be an opening corresponding to each measurement position. Optionally, when the plurality of openings and the sensing surface are moved relative to the radiation beam, the positions of the plurality of openings relative to the sensing surface are maintained.

[0102] In this embodiment, the radiation beam may be measured at a first measurement position, such as Figure 6 This may correspond, for example, to Figure 3A , Figure 3B and Figure 3C Thus, for example, a first measurement may be performed using the first opening O1. The method may then comprise the step of moving the sensing surface in the plane to another measurement position, such as Figure 6 For example, this may correspond to moving the sensing surface and the openings O1, O2, O3 and O4 (relative to the radiation beam) to Figure 3A and Figure 3B The radiation beam can then be measured at the second measurement position, such as Figure 6 This may correspond to, for example, Figure 3A , Figure 3B and Figure 3D Thus, for example, the second measurement can be performed using the second opening O2.

[0103] The plurality of openings may be arranged such that at each measurement position at least one opening is outside the radiation beam, ie outside 100% of the view in plan view. As described above, this may reduce noise for a particular measurement position due to radiation passing through the plurality of openings.

[0104] The method may further comprise masking at least one opening, or preferably masking all openings of the plurality of openings except for the opening at each measurement position. As described above, this may be advantageous for reducing noise. Masking may be performed using a mask MK.

[0105] The method may further comprise providing a grating in at least one of the plurality of openings, or preferably providing the plurality of openings with the same grating.

[0106] In another embodiment, the measurement unit comprises only a single opening through which the radiation beam passes in use. The method further comprises maintaining the position of the single opening relative to the radiation beam projected by the projection system between measurements of each of the plurality of measurement positions. In this embodiment, the sensing surface is thus moved relative to other components of the measurement unit between measurements of the plurality of portions of the radiation beam.

[0107] like Figure 4A and Figure 4B As shown, the position of the radiation beam B and the opening O5 remain at a substantially constant position, and the sensing surface S moves to another measuring position relative to the radiation beam and the opening O5. Thus, the sensing surface measures a different part of the radiation beam as it moves.

[0108] In this embodiment, the radiation beam can be measured at a first measurement position, such as Figure 6 This may correspond, for example, to Figure 4A and Figure 4B The method may then comprise the step of moving the sensing surface in the plane to another measurement position, such as Figure 6 In step S3B of . For example, this may correspond to moving the sensing surface to Figure 4A and Figure 4B The radiation beam can then be measured at the second measurement position, such as Figure 6 This may correspond to, for example, Figure 4A and Figure 4B The measurement is performed at a second measurement position in which the radiation beam has passed through the opening O5.

[0109] Although specific reference may be made herein to the use of lithographic apparatus in IC manufacturing, it should be understood that the lithographic apparatus described herein may have other applications, such as manufacturing integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc. The skilled person will understand that in the context of such alternative applications, any use of the term "wafer" or "die" herein may be considered synonymous with the more general term "substrate" or "target portion", respectively. Before or after exposure, the substrate referred to herein may be processed in, for example, a track (a tool that typically applies a resist layer to a substrate and develops the exposed resist) or a metrology tool or inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, a substrate may be processed more than once, for example to produce a multi-layer IC, so the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0110] As used herein, the terms "radiation" and "beam" encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength of or about 365, 248, 193, 157, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0111] The term "lens," where the context permits, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electrostatic optical components.

[0112] The above description is intended to be illustrative rather than limiting. It will therefore be apparent to those skilled in the art that modifications may be made to the invention as set forth above without departing from the scope of the claims set forth below.

[0113] The foregoing and / or alternative and / or additional embodiments of the present invention may be described in detail in the following clauses:

[0114] 1. A lithographic apparatus, comprising:

[0115] a projection system having an optical axis and configured to project a radiation beam; and

[0116] a measuring unit arranged to measure the radiation beam projected by the projection system, the measuring unit comprising:

[0117] an opening through which the radiation beam passes, in use; and

[0118] a sensing surface extending transversely to said optical axis and arranged to measure said radiation beam passing through said opening,

[0119] wherein the lithographic apparatus is configured to move the sensing surface in a plane transverse to the optical axis between a plurality of measurement positions,

[0120] wherein the radiation beam defines a view in the plane, and

[0121] The measuring unit is configured such that the sensing surface captures a portion of the view at each measuring position, the portion being smaller than 100% of the view.

[0122] 2. A lithographic apparatus according to clause 1, wherein the apparatus is configured to maintain a position of the radiation beam projected by the projection system at a substantially constant position when the sensing surface is configured to measure the radiation beam at the plurality of measurement positions.

[0123] 3. A lithographic apparatus according to clause 1 or 2, wherein at least a portion of the portion of the view captured by the sensing surface at one measurement position does not overlap with a portion of the view captured by the sensing surface at any of the other measurement positions.

[0124] 4. A lithographic apparatus according to any preceding clause, wherein the opening comprises a grating.

[0125] 5. The lithographic apparatus according to any of the preceding clauses, wherein the measurement unit is arranged on a support table.

[0126] 6. A lithographic apparatus according to any of the preceding clauses, wherein the radiation beam projected by the projection system is along the optical axis, and wherein the plane in which the sensing surface is moved is orthogonal to the optical axis.

[0127] 7. A lithographic apparatus according to any preceding clause, wherein the lithographic apparatus is configured to combine the portions of the view captured at the plurality of measurement positions to provide a measurement of the 100% of the view in the plane.

[0128] 8. A lithographic apparatus according to any preceding clause, wherein the distance between the opening and the sensing surface is such that 100% of the view in the plane has an area larger than the sensing surface.

[0129] 9. A lithographic apparatus according to claim 8, wherein the sensing surface is less than or equal to approximately 70% of the area of ​​100% of the views in the plane, or less than or equal to approximately 60% of the area of ​​100% of the views in the plane, or less than or equal to approximately 50% of the area of ​​100% of the views in the plane, or less than or equal to approximately 30% of the area of ​​100% of the views in the plane.

[0130] 10. A lithographic device according to any of the preceding clauses, wherein the measuring unit comprises a plurality of openings through which the radiation beam passes when in use and one of the plurality of openings is used at each measurement position, and wherein the lithographic device is configured to move the plurality of openings transversely to the optical axis in association with moving the sensor surface between the plurality of measurement positions.

[0131] 11. The lithographic apparatus of clause 10, wherein the plurality of openings are in fixed positions relative to the sensing surface.

[0132] 12. The lithographic apparatus of clause 10 or 11, wherein the plurality of openings are arranged such that at each measurement position at least one opening is outside the radiation beam.

[0133] 13. The lithographic apparatus of any of clauses 10 to 12, wherein the lithographic apparatus comprises a mask configured to mask all openings of the plurality of openings except for an opening at each measurement position.

[0134] 14. The lithographic apparatus of any of clauses 10 to 13, wherein the plurality of openings comprise the same grating.

[0135] 15. A lithographic device according to any one of clauses 1 to 9, wherein the measurement unit comprises only a single opening through which the radiation beam passes when in use, and the lithographic device is configured to maintain the position of the single opening relative to the radiation beam projected by the projection system between measurements at each of the plurality of measurement positions.

[0136] 16. A method of measuring a radiation beam in a lithographic apparatus, the method comprising:

[0137] providing a radiation beam;

[0138] projecting the radiation beam through an opening in the measurement system using a projection system having an optical axis; and

[0139] measuring the radiation beam having passed through the opening at a plurality of measurement positions using a sensing surface of the measurement system, the sensing surface extending transversely to the optical axis;

[0140] wherein measuring the radiation beam comprises: moving the sensing surface in a plane transverse to the optical axis between the plurality of measurement positions,

[0141] wherein the radiation beam defines a view in the plane, and

[0142] Wherein the sensing surface captures a portion of the view at each measurement location, the portion being smaller than 100% of the view.

[0143] 17. A method according to clause 16, wherein the measuring comprises maintaining a position of the radiation beam projected by the projection system at a substantially constant position while the measurements of the plurality of measurement positions are made by the sensing surface.

[0144] 18. A method according to clause 16 or 17, wherein at least a portion of the portion of the view captured by the sensing surface at one measurement position does not overlap with the portion of the view captured by the sensing surface at any of the other measurement positions.

[0145] 19. A method according to any of clauses 16 to 18, further comprising a 1D or 2D pattern such as a grating in the opening.

[0146] 20. The method according to any of clauses 16 to 19, further comprising providing a support table, wherein the measurement unit is arranged on the support table.

[0147] 21. A method according to any of clauses 16 to 20, wherein the radiation beam projected by the projection system is along the optical axis, and wherein the plane in which the sensing surface is moved is orthogonal to the optical axis.

[0148] 22. A method according to any of clauses 16 to 21, further comprising the step of combining the portions of the view captured at the plurality of measurement positions to provide a measurement of 100% of the view in the plane.

[0149] 23. A method according to any of clauses 16 to 22, wherein the distance between the opening and the sensing surface is such that 100% of the views in the plane have an area larger than the sensing surface.

[0150] 24. A method according to claim 23, wherein the sensing surface is less than or equal to approximately 70% of the area of ​​100% of the view, or less than or equal to approximately 60% of the area of ​​100% of the view, or less than or equal to approximately 50% of the area of ​​100% of the view, or less than or equal to approximately 30% of the area of ​​100% of the view.

[0151] 25. A method according to any one of clauses 16 to 24, wherein the measuring unit comprises a plurality of openings through which the radiation beam passes when in use and one of the plurality of openings is used at each measurement position, and wherein the method further comprises: moving the plurality of openings and the sensing surface relative to the radiation beam between measurements at each of the plurality of measurement positions.

[0152] 26. The method of clause 25, wherein a position of the plurality of openings relative to the sensing surface is maintained while the plurality of openings and the sensing surface are moved relative to the radiation beam.

[0153] 27. A method according to clause 25 or 26, wherein the plurality of openings are arranged such that at each measurement position at least one opening is outside the radiation beam.

[0154] 28. The method of any of clauses 25 to 27, further comprising masking all openings of the plurality of openings except for an opening at each measurement location.

[0155] 29. A method according to any of clauses 25 to 28, wherein the plurality of openings comprise identical gratings.

[0156] 30. A method according to any one of clauses 16 to 24, wherein the measuring unit comprises only a single opening through which the radiation beam passes when in use, and the method further comprises maintaining the position of the single opening relative to the radiation beam projected by the projection system between measurements at each of the plurality of measurement positions.

Claims

1. A sensing device for a lithographic device, the sensing device comprising: A measuring unit arranged to measure a radiation beam projected by a projection system having an optical axis, the measuring unit comprising: an opening through which the radiation beam passes, in use; and a sensing surface extending transversely to said optical axis and arranged to measure said radiation beam passing through said opening, wherein the sensing surface is movable relative to the opening in a plane transverse to the optical axis between a plurality of measurement positions, wherein the radiation beam defines a view in the plane, and The measuring unit is configured such that the sensing surface captures a portion of the view at each measuring position, the portion being smaller than 100% of the view.

2. The sensing device according to claim 1, Wherein the sensing device is configured to maintain a position of the radiation beam projected by the projection system at a substantially constant position when the sensing surface is configured to measure the radiation beam at the plurality of measurement positions.

3. The sensing device according to any one of claims 1 or 2, wherein at least a portion of the portion of the view captured by the sensing surface at one measurement position does not overlap with a portion of the view captured by the sensing surface at any of the other measurement positions.

4. A sensing device according to any one of claims 1 to 3, wherein a 1D or 2D pattern such as a grating is provided in the opening.

5. The sensing device according to any one of claims 1 to 4, The measuring unit is arranged on a supporting platform.

6. The sensing device according to any one of claims 1 to 5, wherein the radiation beam projected by the projection system is along the optical axis, and wherein the plane in which the sensing surface is moved is orthogonal to the optical axis.

7. The sensing device according to any one of claims 1 to 6, Wherein the sensing device is configured to combine the portions of the view captured at the plurality of measurement positions to provide a measurement of 100% of the view in the plane.

8. The sensing device according to any one of claims 1 to 7, The distance between the opening and the sensing surface is such that 100% of the views in the plane have an area larger than the sensing surface.

9. The sensing device according to claim 8, Wherein the sensing surface is less than or equal to 70% of the area of ​​100% of the view in the plane, or less than or equal to 60% of the area of ​​100% of the view in the plane, or less than or equal to 50% of the area of ​​100% of the view in the plane, or less than or equal to 30% of the area of ​​100% of the view in the plane.

10. A sensing device according to any one of claims 1 to 9, wherein the measuring unit comprises a plurality of openings through which the radiation beam passes when in use and one of the plurality of openings is used at each measuring position, and wherein the sensing device is configured to move at least one of the plurality of openings transversely to the optical axis in association with moving the sensing surface between the plurality of measuring positions.

11. The sensing device according to claim 10, Wherein the at least one opening of the plurality of openings is in a fixed position relative to the sensing surface.

12. The sensing device according to claim 10 or 11, The plurality of openings are arranged such that at each measurement position at least one opening is outside the radiation beam.

13. A sensing device according to any one of claims 10 to 12, The sensing device includes a mask configured to mask all of the plurality of openings except for an opening at each measurement position.

14. A sensing device according to any one of claims 10 to 13, Wherein the plurality of openings comprise the same grating.

15. A sensing device according to any one of claims 1 to 9, wherein the measuring unit comprises only a single opening through which the radiation beam passes when in use, and wherein the sensing device is configured to maintain the position of the single opening relative to the radiation beam projected by the projection system between measurements at each of the plurality of measurement positions.

16. A method of measuring a radiation beam by a sensing device for a lithographic apparatus, the method comprising: measuring a radiation beam having passed through an opening in the measurement cell at a plurality of measurement positions using a sensing surface of the measurement cell, the radiation beam being projected using a projection system having an optical axis, the sensing surface extending transversely to the optical axis; wherein measuring the radiation beam comprises moving the sensing surface relative to the opening in a plane transverse to the optical axis between the plurality of measurement positions, wherein the radiation beam defines a view in the plane, Wherein the sensing surface captures a portion of the view at each measurement location, the portion being smaller than 100% of the view.

17. The method according to claim 16, The measurements include: The position of the radiation beam projected by the projection system is maintained at a substantially constant position while the measurements of the plurality of measurement positions are performed by the sensing surface.

18. The method according to any one of claims 16 to 17, wherein at least a portion of the portion of the view captured by the sensing surface at one measurement position does not overlap with a portion of the view captured by the sensing surface at any of the other measurement positions.

19. A method according to any one of claims 16 to 18, wherein the opening is provided with a 1D or 2D pattern such as a grating.

20. The method according to any one of claims 16 to 19, The method further comprises providing a support table, wherein the measuring unit is disposed on the support table.

21. The method according to any one of claims 16 to 20, wherein the radiation beam projected by the projection system is along the optical axis, and wherein the plane in which the sensing surface is moved is orthogonal to the optical axis.

22. The method according to any one of claims 16 to 21, The method further comprises the following steps: The portions of the view captured at the multiple measurement positions are combined to provide a measurement of 100% of the view in the plane.

23. The method according to any one of claims 16 to 22, The distance between the opening and the sensing surface is such that 100% of the views in the plane have an area larger than the sensing surface.

24. The method according to claim 23, Wherein the sensing surface is less than or equal to 70% of the area of ​​100% of the view in the plane, or less than or equal to 60% of the area of ​​100% of the view in the plane, or less than or equal to 50% of the area of ​​100% of the view in the plane, or less than or equal to 30% of the area of ​​100% of the view in the plane.

25. A method according to any one of claims 16 to 24, wherein the measurement unit comprises a plurality of openings through which the radiation beam passes in use and one of the plurality of openings is used in each measurement position, and wherein the method further comprises: At least one opening of the plurality of openings and the sensing surface are moved relative to the radiation beam between measurements at each of the plurality of measurement positions.

26. The method according to claim 25, Wherein a position of the at least one of the plurality of openings relative to the sensing surface is maintained when the at least one of the plurality of openings and the sensing surface are moved relative to the radiation beam.

27. The method according to claim 25 or 26, The plurality of openings are arranged such that at each measurement position at least one opening is outside the radiation beam.

28. The method according to any one of claims 25 to 27, wherein the method further comprises: All of the plurality of openings except for an opening at each measurement position are masked.

29. The method according to any one of claims 25 to 28, Wherein the plurality of openings comprise the same grating.

30. A method according to any one of claims 16 to 29, wherein the measurement unit comprises only a single opening through which the radiation beam passes in use, and wherein the method further comprises: Between measurements at each of the plurality of measurement positions, a position of the single opening relative to the radiation beam projected by the projection system is maintained.

31. A lithographic apparatus comprising a sensing apparatus according to any one of claims 1 to 15.

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