Superconducting coils assembly and actuator system

Abstract

A lithographic apparatus including: a patterning device; a first positioner to position the patterning device support; a substrate support; a second positioner to position the substrate support; and a projection system configured to project a radiation beam from a patterning device onto a substrate, wherein the patterning device support, the first positioner, the substrate support, and / or the second positioner has, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils are grouped in a plurality of separable and discrete modules which, when assembled, form the assembly, each module including a subset of one or more coils of the plurality of coils and including an electrical interface to provide electricity to the subset of one or more coils and a cooling interface to provide cooling for the superconductivity of the subset of one or more coils.

Description

SUPERCONDUCTING COILS ASSEMBLY AND ACTUATOR SYSTEMCROSS-REFERENCE TO RELATED APPLICATION

[0001] The application claims priority of EP application 23189382.7 which was filed on 03 August, 2023 and EP application 23204881.9 which was filed on 20 October, 2023, and which are incorporated herein in their entirety by reference.FIELD

[0002] The present description relates to a superconducting coil system for use in a magnetic positioner of, for example, a lithographic apparatus.BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also often referred to as “design layout” or “design”) of a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer).

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as ‘Moore’s law’. To keep up with Moore’s law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. To provide a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which are patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm. A lithographic apparatus, which uses extreme ultraviolet (EUV) radiation, having a wavelength within a range of 4 nm to 20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm.

[0005] A lithographic apparatus may include an illumination system configured to provide a projection beam of radiation, and a support structure configured to support a patterning device. The patterning device may serve to impart the projection beam with a pattern in its cross-section. The apparatus may also include a projection system configured to project the patterned beam onto a target portion of a substrate. So, in a lithographic apparatus using radiation to create the pattern, the patterning device is subjected to a radiation beam. While passing via the patterning device, the pattern is imparted to this radiation beam. Subsequently, the radiation beam with imparted pattern passes via the projection system, which projects the imparted pattern onto the substrate.SUMMARY

[0006] In order to provide the substrate with a desired pattern, both the patterning device and the substrate are moved with respect to the projection system as well as with respect to each other. For this purpose linear and / or planar actuator systems are typically used based on one or more current conducting coils and one or more magnets at room temperature or higher due to heat developed by the one or more coils. Linear and planar actuator systems typically have a stator part and a mover part which is movable in a controlled manner with respect to the stator part by manipulating the current through the one or more current conducting coils. The one or more magnets (which can be, for example, one or more permanent magnets and / or one or more electromagnets) can be provided in the stator part and the one or more current conducting coils in the mover part or, the other way around, the one or more magnets can be provided in the mover part and the one or more current conducting coils in the stator part. For example, in some arrangements, the surface of a positioner is equipped with strong permanent magnets in a checkerboard pattern on the stator (e.g., in Halbach array). The mover part contains one or more electromagnets (e.g. in a Lorentz actuator) and levitates over the stator.

[0007] The magnetic field density in the one or more coils of a linear or planar actuator system can be improved by a factor of, e.g., 3-5 by using one or more superconducting electromagnets at a temperature of 4K. In practice superconductors are available which are superconducting at higher cryogenic temperatures in the range of 70K to 150K. Not only the one or more magnets may be one or more superconducting magnets having one or more superconducting coils but additionally or alternatively the one or more current conducting coils may be one or more superconducting coils.

[0008] So, replacing a permanent magnet on, for example, a stator with a superconducting electromagnet can increase the magnetic field density, and therefore provide significant throughput improvement. However, realizing a high field density superconductive coil involves cryogenic cooling. So, to put a superconducting electromagnet into practice a thermal insulation from the cryogenic temperature to room temperature is used which desirably fits within a small stack height. Otherwise the distance between the one or more coils of the mover and the one or more superconducting magnets increases due to the insulation to an extent that the increase of magnetic field density in the one or more coils is lost. There is therefore a desire for a thermal insulation layer of small height.

[0009] In an embodiment, there is provided a superconductive assembly for an actuator, the assembly comprising, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils are grouped in a plurality of separable and discrete modules which, when assembled, form the assembly, each module comprising a subset of one or more coils of the plurality of coils and comprising an electrical interface to provide electricity to the subset of one or more coils.

[0010] In an embodiment, there is provided a magnet body for a planar motor, the magnet body comprising, during use, a plurality of superconductive coils that are configured to, during use, generate a 2D spatially alternating magnetic field, wherein the plurality of superconductive coils are grouped ina set of separable and discrete modules which, when assembled, form the magnet body, each module comprising a subset of the plurality of coils.

[0011] In an embodiment, there is provided a module for a superconductive assembly for an actuator, the module comprising one or more superconductive coils of a plurality of superconductive coils of the assembly, the module having an exterior or multi-surface non-planar wall.

[0012] In an embodiment, there is provided a lithographic apparatus assembly comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils are grouped in a plurality of separable and discrete modules which, when assembled, form the assembly, each module comprising a subset of one or more coils of the plurality of coils and comprising an electrical interface to provide electricity to the subset of one or more coils.

[0013] In an embodiment, there is provided a superconductive assembly for an actuator, the assembly comprising a superconductive coil array configured to cooperate with a mover of the actuator, and one or more superconductive coils configured to cooperate with a separate body from the mover, the superconductive coil array and the one or more superconductive coils having a common cooling arrangement to provide cooling for the superconductivity.

[0014] In an embodiment, there is provided a lithographic apparatus assembly comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises a superconductive coil array configured to cooperate with a mover, and one or more superconductive coils configured to cooperate with a separate body from the mover, the superconductive coil array and the one or more superconductive coils having a common cooling arrangement to provide cooling for the superconductivity.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which corresponding reference symbols indicate corresponding parts and in which:

[0016] Figure 1 schematically depicts a schematic overview of a lithographic apparatus;

[0017] Figure 2 schematically depicts a view of a part of the lithographic apparatus of Figure 1 ;

[0018] Figure 3 schematically depicts a position control system;

[0019] Figure 4 schematically depicts a cross section of an actuator system according to an embodiment;

[0020] Figure 5 schematically depicts in top view an actuator system;

[0021] Figure 6 schematically depicts an embodiment of an insulation covering of an assembly of an actuator system;

[0022] Figure 7 schematically depicts an embodiment of an insulation covering of an assembly of an actuator system;

[0023] Figure 8 schematically depicts a detail of an insulation covering of an assembly of an actuator system;

[0024] Figure 9 schematically depicts a cross section of an actuator system in accordance with an embodiment;

[0025] Figure 10 schematically depicts a thermal conditioning plate in accordance with an embodiment;

[0026] Figure 11 schematically depicts a cross-section of a flexible conduit in accordance with an embodiment;

[0027] Figures 12A and 12B schematically depict arrangements of an internal passage network in accordance with embodiments;

[0028] Figure 13a schematically depicts a cross section of an actuator system in accordance with an embodiment;

[0029] Figure 13b schematically depicts a power supply as can be applied in an actuator system in accordance with an embodiment;

[0030] Figures 13c and 13d schematically depict a cross section of actuator systems in accordance with an embodiment;

[0031] Figure 14 schematically depicts a perspective view of an arrangement of modules to hold coils of an actuator system in accordance with an embodiment;

[0032] Figures 15A, 15B and 15C schematically depict cross-sections (when viewed from the bottom or top) of a partial arrangement of modules to hold coils of an actuator system in accordance with an embodiment; and

[0033] Figure 16 depicts schematically depicts a cross section of an actuator system in accordance with an embodiment.

[0034] The features shown in the Figures are not necessarily to scale, and the size and / or arrangement depicted is not limiting. It will be understood that the Figures include optional features which may not be essential to the invention. Furthermore, not all of the features of the apparatus are depicted in each of the figures, and the Figures may only show some of the components relevant for describing a particular feature.DETAILED DESCRIPTION

[0035] In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation or charged particles, including ultraviolet radiation (e.g. with a wavelength of 365, 248, 193, 157 or 126 nm), EUV radiation (extreme ultra-violet radiation, e.g. having a wavelength in the range of about 5-100 nm such as 13.5 nm), or charged particles (e.g., electron beams, ion beams, etc.).

[0036] The term “reticle”, “mask” or “patterning device” as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow a radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term “light valve” can also be used in this context. Besides the classic mask (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable LCD array.

[0037] Figure 1 schematically depicts a lithographic apparatus LA. The lithographic apparatus LA includes an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation or EUV radiation), a patterning device support (e.g., a mask table) MT constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA in accordance with certain parameters, a substrate support (e.g., a substrate table or a substrate holder) WT constructed to hold a substrate (e.g., a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate support in accordance with certain parameters, and a projection system (e.g., a refractive and / or reflective projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0038] The assembly according to an embodiment of the invention - which will be elucidated further below - may be used in the first positioner PM and / or the support MT. In addition or alternatively, the assembly according to an embodiment of the invention - which will be elucidated further below - may be used in the second positioner PW and / or the support WT.

[0039] In operation, the illumination system IL receives a radiation beam from a radiation source SO, e.g. via a beam delivery system BD. The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for directing, shaping, and / or controlling radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and / or angular intensity distribution in its cross section at a plane of the patterning device MA.

[0040] The term “projection system” PS used herein should be broadly interpreted as encompassing various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, and / or for other factors such as the use of an immersion liquid or the useof a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system” PS.

[0041] The lithographic apparatus LA may be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system PS and the substrate W - which is also referred to as immersion lithography. More information on immersion techniques is given in United States patent no. US6952253, which is incorporated herein in its entirety by reference.

[0042] In addition to the substrate support WT, the lithographic apparatus LA may comprise a utility support arranged at the level of the substrate support WT. In an embodiment, the utility support is arranged to hold a sensor and / or a cleaning device. In an embodiment, the utility support is not configured to support a substrate W, i.e., not capable of holding a substrate W for exposure. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The utility support may hold multiple sensors. The cleaning device may be arranged to clean part of the lithographic apparatus, for example a part of the projection system PS or a part of a system that provides the immersion liquid. The utility support may move beneath the projection system PS when the substrate support WT is away from the projection system PS.

[0043] So, the lithographic apparatus LA may be of a type having two or more substrate supports WT and having one or more substrate supports WT and one or more utility supports. In such a “multiple stage” machine, the supports may be used in parallel, and / or steps in preparation of a subsequent exposure of a substrate may be carried out on a substrate W located on substrate support WT or carried out using a utility support, while a substrate W on a substrate support WT is being used for exposing a pattern on that substrate W.

[0044] Also in the case of two or more supports (e.g., two or more substrate supports or one or more substrate supports with one or more utility supports, the assembly according to an embodiment of the invention - which will be elucidated further below - may be used in the second positioner PW and / or one or more of the associated supports (e.g., support WT and / or utility support) at the second positioner PW.

[0045] In operation, the radiation beam B is incident on the patterning device, e.g. mask, MA which is held on the support MT, and is patterned by the pattern (design layout) present on patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and a position measurement system PMS, the substrate support WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B at a focused and aligned position. Similarly, the first positioner PM and possibly another position sensor (which is not explicitly depicted in Figure 1) may be used to accurately position the patterning device MA with respect to the path of the radiation beam B. Patterning device MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks Pl, P2.Although the substrate alignment marks Pl, P2 as illustrated occupy dedicated target portions, they may be located in spaces between target portions. Substrate alignment marks Pl, P2 are known as scribelane alignment marks when these are located between the target portions C.

[0046] To clarify an embodiment of the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes, i.e., an x-axis, a y-axis and a z-axis. Each axis of the three axes is orthogonal to the other two axes. A rotation around the x-axis is referred to as an Rx-rotation. A rotation around the y-axis is referred to as an Ry-rotation. A rotation around the z-axis is referred to as an Rz-rotation. The x- axis and the y-axis define a horizontal plane, whereas the z-axis is in a vertical direction. The Cartesian coordinate system is not limiting the invention and is used for clarification only. Instead, another coordinate system, such as a cylindrical coordinate system, may be used to clarify an embodiment of the invention. The orientation of the Cartesian coordinate system may be different, for example, such that the z-axis has a component along the horizontal plane.

[0047] Figure 2 shows a more detailed view of a part of the lithographic apparatus LA of Figure 1. The lithographic apparatus LA may be provided with a base frame BF, a balance mass BM, a metrology frame MF and a vibration isolation system IS. The metrology frame MF supports the projection system PS. Additionally, the metrology frame MF may support a part of the position measurement system PMS. The metrology frame MF is supported by the base frame BF via the vibration isolation system IS. The vibration isolation system IS is arranged to prevent or reduce vibrations from propagating from the base frame BF to the metrology frame MF. An embodiment of the balance mass BM would be located between the second positioner PW and the base shown in Figure 1.

[0048] At least part of the second positioner PW (e.g., the sole actuator of second positioner PW if the second positioner PW has just one actuator or a particular actuator of a plurality of actuators if second positioner PW has a plurality of actuators) is arranged to accelerate the substrate support WT by providing a driving force between the substrate support WT and the balance mass BM. The driving force accelerates the substrate support WT in a desired direction. Due to the conservation of momentum, the driving force is also applied to the balance mass BM with equal magnitude, but in a direction opposite to the desired direction. Typically, the mass of the balance mass BM is significantly larger than the masses of the moving part of the at least part of the second positioner PW and the substrate support WT. In an embodiment, the balance mass BM is movable (e.g., supported by a bearing on the base frame BF or supported by one or more flexures on the base frame BF). In an embodiment, there may be one or more drift motors configured to help movement of the balance mass, e.g., to help put it into a proper location.

[0049] In an embodiment, the at least part of the second positioner PW is supported by the balance mass BM. For example, in an embodiment, the balance mass BM supports a stator part of an electric actuator, while the substrate support WT has a mover part of the electric actuator. For example, a part of a planar actuator system of second positioner PW to levitate or accelerate the substrate support WT above and / or relative to the balance mass BM. In an embodiment, the second positioner PW is supportedby the base frame BF, for example, where the second positioner PW comprises a stator of an actuator and comprises a bearing, like a gas bearing, to levitate the substrate support WT above the base frame BF. According to an example, the second positioner PW may comprise a linear actuator system.

[0050] The position measurement system PMS may comprise any type of sensor that is suitable to determine a position of the substrate support WT. The position measurement system PMS may comprise any type of sensor that is suitable to determine a position of the support MT. The sensor may be an optical sensor such as an interferometer or an encoder. The position measurement system PMS may comprise a combined system of an interferometer and an encoder. The sensor may be another type of sensor, such as a magnetic sensor, a capacitive sensor or an inductive sensor. The position measurement system PMS may determine the position relative to a reference, for example the metrology frame MF or the projection system PS. The position measurement system PMS may determine the position of the support WT and / or support MT by measuring the position or by measuring a time derivative of the position, such as velocity or acceleration.

[0051] The position measurement system PMS may comprise an encoder system. An encoder system is known from for example, United States patent application publication no. US2007 / 0058173, which is incorporated herein in its entirety by reference. The encoder system comprises an encoder head, a grating and a sensor. The encoder system may receive a primary radiation beam and a secondary radiation beam. Both the primary radiation beam as well as the secondary radiation beam originate from the same radiation beam, i.e., the original radiation beam. The primary radiation beam and / or secondary radiation beam is created by diffracting the original radiation beam with the grating. If both the primary radiation beam and the secondary radiation beam are created by diffracting the original radiation beam with the grating, the primary radiation beam needs to have a different diffraction order than the secondary radiation beam. Different diffraction orders are, for example, +lstorder, -1storder, +2ndorder and -2ndorder. The encoder system optically combines the primary radiation beam and the secondary radiation beam into a combined radiation beam. A sensor in the encoder head determines a phase or phase difference of the combined radiation beam. The sensor generates a signal based on the phase or phase difference. The signal is representative of a position of the encoder head relative to the grating. One of the encoder head and the grating may be arranged on the substrate structure WT. The other of the encoder head and the grating may be arranged on the metrology frame MF or the base frame BF. For example, in an embodiment, a plurality of encoder heads are arranged on the metrology frame MF, whereas one or more grating are arranged on a top surface of the substrate support WT. In another example, one or more gratings are arranged on a bottom surface of the substrate support WT, and an encoder head is arranged below the substrate support WT.

[0052] The position measurement system PMS may comprise an interferometer system. An interferometer system is known from, for example, United States patent 6,020,964, which is incorporated herein in its entirety by reference. The interferometer system may comprise a beam splitter, a mirror, a reference mirror and a sensor. A beam of radiation is split by the beam splitter into a referencebeam and a measurement beam. The measurement beam propagates to the mirror and is reflected by the mirror back to the beam splitter. The reference beam propagates to the reference mirror and is reflected by the reference mirror back to the beam splitter. At the beam splitter, the measurement beam and the reference beam are combined into a combined radiation beam. The combined radiation beam is incident on the sensor. The sensor determines a phase or a frequency of the combined radiation beam. The sensor generates a signal based on the phase or the frequency. The signal is representative of a displacement of the mirror. In an embodiment, the mirror is connected to the substrate support WT. The reference mirror may be connected to the metrology frame MF. In an embodiment, the measurement beam and the reference beam are combined into a combined radiation beam by an additional optical component instead of the beam splitter.

[0053] The first positioner PM may comprise a long-stroke module and a short-stroke module. The short-stroke module is arranged to move the patterning device support MT relative to the long-stroke module with a high accuracy over a small range of movement. The long-stroke module is arranged to move the short-stroke module relative to the projection system PS with a relatively low accuracy over a large range of movement. With the combination of the long-stroke module and the short-stroke module, the first positioner PM is able to move the patterning device support MT relative to the projection system PS with a high accuracy over a large range of movement. For example, the long- stroke module can move the support MT with pm accuracy while the short-stroke module can move the support MT with nm accuracy.

[0054] Similarly, the second positioner PW may comprise a long-stroke module and a short-stroke module. The short-stroke module is arranged to move the substrate support WT relative to the long- stroke module with a high accuracy over a small range of movement. The long-stroke module is arranged to move the short-stroke module relative to the projection system PS with a relatively low accuracy over a large range of movement. With the combination of the long-stroke module and the short-stroke module, the second positioner PW is able to move the substrate support WT relative to the projection system PS with a high accuracy over a large range of movement. For example, the long- stroke module can move the support WT with pm accuracy while the short-stroke module can move the support WT with nm accuracy. In an embodiment, the long-stroke module of the second positioner PW interacts with a balance mass BM.

[0055] The first positioner PM and the second positioner PW each are provided with an actuator to move respectively the patterning device support MT and the substrate support WT. The actuator of the first positioner and / or second positioner may be a linear actuator to provide a driving force along a single axis, for example the y-axis. Multiple linear actuators may be applied to provide driving forces along multiple axes. The actuator may be a planar actuator to provide a driving force along multiple axes. For example, the planar actuator may be arranged to move a support in 6 degrees of freedom. The actuator may be an electro-magnetic actuator comprising at least one coil and at least one magnet. In an embodiment, the actuator is arranged to provide relative movement between the at least one coil andthe at least one magnet by applying an electrical current to the at least one coil. The actuator may be a moving-magnet type actuator, which has the at least one magnet coupled to the support (e.g., support WT or support MT). The actuator may be a moving-coil type actuator which has the at least one coil coupled to the support (e.g., support WT or support MT). The actuator may be a voice-coil actuator, a reluctance actuator, a Lorentz-actuator, a piezo-actuator, or any other suitable actuator.

[0056] A position control system PCS as schematically depicted in Figure 3 can be provided. In an embodiment, a lithographic apparatus comprises the position control system PCS. In an embodiment, the position control system PCS comprises a setpoint generator SP, a feedforward controller FF and a feedback controller FB. The position control system PCS provides a drive signal to the actuator ACT. The actuator ACT may be the actuator of the first positioner PM or the second positioner PW. The actuator ACT drives the plant P, which may comprise the substrate support WT or the patterning device support MT. An output of the plant P is a position quantity such as position or velocity or acceleration. The position quantity is measured with the position measurement system PMS. The position measurement system PMS generates a signal, which is a position signal representative of the position quantity of the plant P. The setpoint generator SP generates a signal, which is a reference signal representative of a desired position quantity of the plant P. For example, the reference signal represents a desired trajectory of the substrate support WT. A difference between the reference signal and the position signal forms an input for the feedback controller FB. Based on the input, the feedback controller FB provides at least part of the drive signal for the actuator ACT. The reference signal may form an input for the feedforward controller FF. Based on the input, the feedforward controller FF provides at least part of the drive signal for the actuator ACT. The feedforward FF may make use of information about one or more dynamical characteristics of the plant P, such as mass, stiffness, a resonance mode and / or eigenfrequency.

[0057] Figure 4 shows, schematically, a side cross-section of actuator system 1 according to an embodiment, which system has a coil layer 3 of one or more coils 2 to form one or more electromagnets and is provided with an arrangement 6, 7, 8, 9. Due to the coil layer 3 being flat, this actuator system 1 is a linear actuator system or planar actuator system. The coil layer 3 is flat, because the one or more coils 2 are arranged in a plane. In the example of Figure 4, it is a planar actuator system. In the example shown, this planar actuator system 1 is used in, for example, the wafer stage of a lithographic apparatus. For this purpose, the substrate W, substrate support WT and second positioner PW are indicated with the same references as used in Figures 1-3. In addition or alternatively, the positioning system 1 may be used as a planar or linear actuator system in the mask stage of a lithographic apparatus, in which case the substrate W may be the patterning device MA (e.g. a mask), the substrate support WT may be the patterning device support MT and the second positioner PW may be the first positioner PM.

[0058] Figure 5 shows a detail of Figure 4, which details are shown in Figure 4 in cross-section according to the arrows IV as indicated in Figure 5.

[0059] In the embodiments of Figures 4 and 5 the arrangement 6, 7, 8, 9 is provided in the stator partof the planar actuator system 1. The mover part of this planar actuator system, in this example indicated as WT, is at its underside provided with a layer of conducting coils 21, 22 (in an embodiment, a flat layer) in which the current can be manipulated by means of a controller in order to control the position of the mover part WT with respect to the stator part PW; 8, 3, 9.

[0060] The arrangement 6, 7, 8 and 9 is configured to cryocool the one or more superconducting coils 2 in the coil layer 3 at a cryogenic temperature, for example a temperature at or below 30 K as indicated in Figure 4. In an embodiment, the arrangement 6, 7, 8, 9 has features akin to a cryostat. Taking into account that presently there are materials available which are superconducting in the range of 70K to 150K, this temperature may also be higher than 30K.

[0061] In the embodiments of Figures 4 and 5, the coil layer 3 is a layer of one or more superconducting coils 2. In an embodiment, the coil layer is flat and has opposing layer faces 4, 5. In Figure 4, layer face 4 is the lower face of the coil layer 3 and layer face 5 is the upper face of coil layer 3.

[0062] The arrangement comprises a cryocooler system 6, a vacuum system 7, and two insulation coverings 8, 9. The coil layer 3 and two insulation coverings 8, 9 are arranged in a sandwich manner, with the coil layer 3 arranged between the two insulation coverings 8, 9 such that each of the two opposing layer faces 4, 5 is covered by one of the insulation coverings 8, 9.

[0063] One of the insulation coverings or both the insulation coverings 8, 9 may each comprise an inner plate 10 and an outer plate 11 substantially parallel to the inner plate 10. The inner plate 10 is closest to the coil layer 3 and arranged between the outer plate 11 and the coil layer 3. One of or both the insulation coverings 8, 9 may further comprise an insulation system 12 arranged between the inner plate 10 and outer plate 11.

[0064] The vacuum system is configured to provide a low pressure / vacuum (layer) 13 in the insulation system.

[0065] The cryocooler system is configured to cryocool the inner plate 10 and is for this purpose at 14 connected with the inner plate 10 of the insulation covering 9. Because the inner plate 10 of the insulation covering 8 is thermally connected with the inner plate 10 of the insulation covering 9, also the inner plate 10 of the insulation covering will be cryocooled. This thermal connection may for example be provided via the magnets 2 or by unshown thermal bridges.

[0066] According to an embodiment, the insulation system 12 of one or both the insulation coverings 8, 9 comprises, in the low pressure / vacuum (layer) 13, one or more layers of bodies 101 each defining an, for example, a contour 102 (e.g., that is at least partly circular) and a central axis extending through a central portion of each body 101 as well as perpendicular to the contour 102. The central axes of the bodies 101 of each layer of bodies extend parallel to the inner plate 10 and outer plate 11.

[0067] In the embodiment in Figure 4, the bodies 101 are spheres, in this case full-spheres, but these bodies 101 may be half-spheres, oval or straight cylindrical bodies, e.g. full-cylindrical bodies, oval bodies or half-cylindrical bodies. The term “full-“ relates specifically to the outer contour of the bodiesnot to the inner of the bodies. The inner of a full-circular bodies may for example be hollow or a fullcircular body may have a through bore in order to save weight and / or to reduce the thermal conductivity of the bodies.

[0068] In an embodiment, the insulation covering 8, 9 are configured to provide at least one layer 104, 105 of point contacts 106 between two layers of bodies 101 or between a layer of bodies 101 and the inner plate 10 and / or outer plate 11. This configuration is such that each possible thermal conductive path between the inner plate 10 and outer plate 11 has to pass, at some place, through at least one point contact 106. This can result in an insulation covering having minimal or low thermal conductivity due to the layer of point contacts, on the one hand, and high load bearing capacity due to the bodies on the other hand. In the example of Figure 4, there are two layers 104 and 105 of point contacts 106. One layer 105 at the side of the outer plates 11 and one layer 104 at the side of the inner plates 10.

[0069] In the embodiment of Figure 4, the bodies 101 may be (full-) spheres of zirconium with a diameter of 7 mm. These spheres lie between the inner plate 10 and outer plate 11. In a linear actuator the vertical distance D between the layer 3 of electro-magnets 2 and the conducting coils 21, 22 is limited. This means that the vertical thickness (in the direction of double arrow D) of especially the insulation covering 8 is to be kept low. With an aluminum inner plate 10 and aluminum outer plate 11 of each 0.75 mm thickness and spheres with a diameter of 7 mm, the total thickness of the insulation covering is about 9 mm. This thickness can be reduced by using a thinner inner plate 10 and thinner outer plate 11 and / or by using bodies 101 of smaller cross-sectional width. In this respect it is to be noted that zirconium spheres with diameters from 0.2 mm can be obtained.

[0070] Also the insulation covering 9 can be designed to be very thin. But taking into account that on this side of the layer 3 of one or more superconducting coils 2 space is in general not a real issue, the bodies 101 in the insulation covering 9 can be larger than the bodies 101 in the insulation covering 8. The bodies in the insulation covering 9 may for example be in the range of 15-20 mm.

[0071] In order to help prevent these bodies from moving, a spacer plate 107 may be provided. This spacer plate 107 may be provided with a pattern of through holes, each having a cross-sectional width in the range of 70-100% of the cross-sectional width of the bodies. By using a spacer plate with a thermal expansion coefficient larger than the thermal expansion coefficient of the bodies, a sealing shrunk connection between the bodies 101 and the spacer plate 107 can be obtained when the inner plate is cryocooled. Further, the spacer plate 107 may be kept at a temperature of, in this example, about 80 K by the crycooler. For this purpose the crycooler 6 is at 108 connected with the spacer plate 107 of the insulation covering 9 (and / or 8, not shown). The spacer plate 107 then serves as a shield which improves the insulation capacity of the insulation covering 8, 9. In order to cool both the spacer plates 107, the spacer plates 107 are thermally connected by thermal connection 109.

[0072] As shown in Figure 4 by means of the indicated temperatures, the substrate support WT may be at room temperature (295 K), the coils 21 and 22 may have a temperature higher than room temperature (>295 K) due to heat development in the coils 21 and 22, and a frame 15 to support theactuator system 1 may be at room temperature as well. Further the crycooler cryocools both the inner plates 10 at a cryogenic temperature, which will, according to this example, be below 30K. To improve the insulation, the spacer plates 107 are cooled by the cryocooler to have a temperature between the temperature of the inner plates (in this example < 30K) and the temperature of the outer plates (in his example 295 K). The temperature of the spacer plates may for example be 80 K.

[0073] In the example of Figures 4 and 5, the planar actuator system has a stator part provided with a layer of one or more superconducting coils 2 and a mover part provided with a layer of normalconducting coils 21, 22 (which are in general at room temperature or higher when, in use, the coils 21, 22 produce heat), see Figures 4 and 5. It is noted that additionally or alternatively the layer of coil 21 and / or 22 may be a layer of one or more superconducting coils having on both sides or one side of the layer an insulation covering 8, 9 according to an embodiment with bodies in a low pressure / vacuum layer. In this case the coil layer 3 may be a coil layer of one or more permanent magnets or one or more normal electromagnets or one or more superconducting electromagnets.

[0074] As shown in very schematic cross-section in Figures 6 and 7, the insulation covering 8 and / or insulation covering 9 may also comprise multiple layers of bodies, separated by intermediate plates.

[0075] Figure 6 shows two layers 200, 210 of bodies 201 and 211, respectively. The bodies 201 in the layer 200 may be maintained in position by a spacer plate 207 and the bodies 211 in the layer 210 may be maintained in position by a spacer plate 217. The two layers 200 and 210 of bodies 201 and 211 may be separated by an intermediate layer 240. This configuration provides a total of four layers 204, 205, 214 and 215 of point contacts 206 and 216. By using bodies of smaller cross-sectional width (e.g. diameter), the thickness of the insulation covering of Figure 6 can still be maintained at or below the 9 mm thickness as mentioned in relation to Figure 4.

[0076] Figure 7 shows four layers 300, 310, 320, 330 of bodies 301, 311, 321 and 331, respectively. The bodies 301 in the layer 300 may be maintained in position by a spacer plate 307, the bodies 311 in the layer 310 may be maintained in position by a spacer plate 317, the bodies 321 in the layer 320 may be maintained in position by a spacer plate 327, and the bodies 331 in the layer 330 may be maintained in position by a spacer plate 337. The two layers 300 and 310 of bodies 301 and 311 may be separated by an intermediate layer 340, the two layers 310 and 320 of bodies 311 and 321 may be separated by an intermediate layer 350, and the two layers 320 and 330 of bodies 321 and 331 may be separated by an intermediate layer 360. This configuration provides a total of eight layers 304, 305, 314, 315, 324, 325, 334 and 335 of point contacts 206, 216, 226 and 236. By using spheres of smaller cross-sectional width (e.g. diameter), the thickness of the insulation covering of Figure 7 can still be maintained at or below the 9 mm thickness as mentioned in relation to Figure 4.

[0077] As shown in a very schematic perspective view in Figure 8, an insulation system 400 providing at least one layer of point contacts can also be obtained with cross-wise stacked layers of straight (e.g., cylindrical) bodies 401, 411, like wires having respective circular outer contours 402, 412. At the crossings of the bodies 401 and 411 there will be point contacts 406, as schematically indicatedat four crossings in Figure 8. In the construction of Figure 8, the bodies 401, 402 of each layer are straight and the layers being crosswise stacked help ensured that each possible thermal conductive path between the inner and outer plate has to pass, at some place, through at least one point contact.

[0078] So, in an embodiment, there is provided a cryostat environment for a coil layer that comprises two insulation coverings. The coil layer and two insulation coverings are arranged in a sandwich manner, with the coil layer arranged between the two insulation coverings and each of two opposing layer faces of the coil layer covered by one of the insulation coverings in order to be able to keep the coil layer at a cryogenic condition required for superconductivity of the one or more coils.

[0079] In an embodiment, the insulation coverings each comprise: an inner plate and an outer plate parallel to the inner plate, the inner plate being arranged between the outer plate and the coil layer, and an insulation system arranged between the inner plate and the outer plate. The inner plate and / or outer plate may be made of a stainless steel alloy.

[0080] In an embodiment, the insulation system is configured to have a vacuum layer. A vacuum layer in the insulation system reduces thermal conductivity between the inner plate and outer plate. This vacuum may be a vacuum of 10'3Pa or lower. If an insulation covering is in an ambient of normal air pressure, this results in the insulation covering having to be able to withstand a pressure difference of about 100 kPa.

[0081] In an embodiment, the inner plates are configured to be cryocooled in order to bring and maintain the coil layer at cryogenic condition.

[0082] In an embodiment, the insulation system of one or both the insulation coverings:- comprises, in a vacuum layer, one or more layers of bodies each defining a contour and a central axis extending through a central portion of the contour as well as perpendicular to the contour, the central axes of the bodies of each layer of circular bodies extending parallel to the inner and outer plate, and- is configured to provide at least one layer of point contacts between two layers of bodies or between a layer of the bodies and the inner and / or outer plate such that each possible thermal conductive path between the inner and outer plate has to pass, at some place, through at least one point contact.

[0083] In an embodiment, the layer of bodies is arranged between the inner and outer plate and support the inner plate on the outer plate when the inner plate lies above the outer plate or support the outer plate on the inner plate when the outer plate lies above the inner plate. The bodies can have a high load-bearing capacity, on the one hand, while providing a point contact, on the other hand. As a point contact has a very small contact surface, the thermal conductivity through the point contact is very low. With one or more layers of bodies having their central axes parallel to the inner and outer plate and configured to provide at least one layer of point contacts it helps ensure that each possible thermal conductive path between the inner and outer plate has to pass, at some place, through at least one point contact. This can result in an insulation covering having minimal thermal conductivity, on the one hand, and high load bearing capacity on the other hand.

[0084] In an embodiment, the bodies may be fully circular or partly circular having a partly circular contour extending over an angle of 180° or less, like 60-120°. The bodies may be spherical bodies, like spheres and / or half-spheres, and / or straight cylindrical bodies, like cylinders and / or half-cylinders. For example, in the case of half-spheres or half-cylinders, the half-spheres or half-cylinders may be glued onto the face of the inner plate facing the outer plate and / or onto the face of the outer plate facing the inner plate, and stacked onto each other resulting in a the layer of point contacts between half spheres, between half-cylinders, or between half-spheres and half-cylinders.

[0085] Defining a diameter of a body as twice the radius from the center of a circular contour to a circular contour, the diameter of the bodies may, according to an embodiment, be smaller than 7 mm, such as smaller than 5 mm. The diameter may be in the range of 0.1 to 5 mm, such as in the range of 0.5 to 4 mm. Bodies of such diameter can allow insulation coverings with a thickness - perpendicular to the inner and outer plate - of less than 10 mm. Even a thickness much lower is possible and / or multiple layers of point contact are possible with smaller diameters while still keeping the total thickness of the insulation covering below 10 mm. The thickness may for example be at most 7-8 mm.

[0086] The point contacts in a layer of point contacts may, according to an embodiment, be arranged with a pitch of 5-20 mm, for example a pitch of 10-15 mm.

[0087] According to an embodiment, the bodies may be made from a material selected from: zirconia, Kevlar, a Kevlar composite, a Kevlar fiber composite, glass, a glass composite, a glass fiber composite, or a titanium alloy. These materials are commercially available in the form of wires and spheres, have a large strength and low thermal conductivity.

[0088] According to an embodiment, the bodies may be made from a material having a ratio of the Young modulus with respect to the integral of the thermal conductivity coefficient over the temperature range of 4K to 80K, which is at least 1 N / Wm, such as at least 1.5 N / Wm.

[0089] According to an embodiment, at least one of the layers of bodies may comprise a spacer plate provided with a pattern of through holes for accommodating the bodies, each through hole having a cross-sectional width configured to contact a body such that the spacer plate is supported by the bodies, wherein the spacer plate is arranged parallel to the inner plate and outer plate. Viewed perpendicular to the spacer plate, the spacer plate is arranged at a distance from each of opposing ends of the bodies. This spacer plate prevents the bodies from moving away by keeping them at locations determined by the through holes. In this embodiment, the spacer plate may be configured for being cooled, like cryocooled, at a temperature between a temperature of the inner plate and a temperature of the outer plate. The spacer plate then additionally serves as an insulation shield increasing the thermal insulation. The width of the through holes may be, for example, in the range of 70-100%, such as 90-100%, of the width (e.g., diameter) of the bodies. In an embodiment, the thermal expansion coefficient of the spacer plate may be larger than the thermal expansion coefficient of the bodies such that when the spacer plate and bodies are cooled down a shrunk connection between the spacer plate and bodies is obtained in the through holes. This shrunk connection may provide a sealing closing the through hole with respect tothe body, which improves the insulation capacity of the insulation system. For this purpose, the spacer plate may be made from aluminum or an aluminum alloy.

[0090] According to an embodiment, the assembly may comprise a multiple of the layers of bodies, wherein between adjacent ones of the layers of bodies a separation plate is arranged which provides on each side an additional layer of point contacts between the separation plate and bodies. In this embodiment, the separation plate may be configured for being cooled, like cryocooled, at a temperature between a temperature of the inner plate and a temperature of the outer plate.

[0091] According to an embodiment, the one or more layers of bodies may comprise at least one set of two layers of bodies, such as cylinders and / or half-cylinders; wherein the bodies of a first of the two layers are arranged parallel to each other with a spacing between adjacent bodies and the bodies of a second of the two layers are arranged parallel to each other with a spacing between adjacent bodies; and wherein the first layer and second layer are stacked directly onto each other with the bodies of the first layer crosswise with respect to the bodies of the second layer to provide, between the bodies of the first layer and the bodies of the second layer, a layer of point contacts. In this embodiment, the bodies may be wires. Crosswise may be at an angle of 90° or at any other angle, like an angle in the range of 30° to 90°, for example an angle of about 60°.

[0092] According to an embodiment, there may be provided a cryocooler system configured to provide cryocooling of, e.g., the inner plates.

[0093] According to an embodiment, there may be provided a low pressure / vacuum system configured to provide low pressure / vacuum of 10 Pa or lower, 1 Pa or lower, 10'2Pa or lower or 10"3Pa or lower.

[0094] According to an aspect, there is provided a lithographic apparatus comprising an assembly as described herein. Such a lithographic apparatus may comprise a patterning device support constructed to support a patterning device, a first positioner configured to position the patterning device support with respect to the first positioner, a substrate support constructed to hold a substrate, a second positioner configured to position the substrate support with respect to the second positioner, and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner, are provided with an assembly as described herein.

[0095] According to an aspect, there is provided an assembly for use in a lithographic apparatus, the assembly comprising a thermal conditioning plate comprising an internal passage network for flowing a cryogen therein, and a plurality of superconducting coils for magnetically levitating and linearly displacing a stage thereon, wherein the plurality of superconducting coils is in thermal contact with an external surface of the thermal conditioning plate.

[0096] United States patent application publication no. US 2021 / 0223706, which is herein incorporated by reference in its entirety, discloses a cryocooling arrangement with one or more superconducting coils that is applicable for, e.g., lithography. It describes, for example, a first stage ofa cryocooler attached directly to a spacer plate at, e.g., 80K, and a second stage of the cryocooler attached to an inner plate at, e.g., <30K on which the one or more superconducting coils are mounted. In this design, the cryocooler acts a heat sink for the components at these two temperature levels. The cryocooler cold end has spot connections with the cold surfaces, i.e. the spacer plate and the inner plate.

[0097] In such an arrangement, the cooling capability of the cryocooler can be limited by the number of spot connections that the cryocooler makes on the cold surfaces, as well as the thermal conductivity between these connections and the generated / absorbed heat. Due to the generated heat near the one or more superconducting coils on top of the inner plate, given that the average dimensions of the inner plate can be larger than a meter, even if the cryocooler is centrally positioned, the temperature distribution of the one or more superconducting coils may have large variations. If the temperature variations are sufficiently large, they can potentially harm the performance of the positioner. In particular, the spatial temperature variations could generate unwanted variations in electromagnetic performance over the one or more superconducting coils.

[0098] To compensate for the temperature variations, a more powerful cryocooler may be employed so as to keep the warmest coil at the target temperature, but this can lead to a significant increase in required cooling power. Alternatively, the number of connections between the cryocooler and the cold surface may be increased, such as by providing multiple cryocoolers. However, as the positioner may be subject to sharp accelerations during operation, and one or more cryocooler components move with the positioner, increasing the number of connections could result in mechanical difficulties. For example, acceleration forces may be harmful for the mechanical connection between the long and slender cryocooler and the relatively rigid positioner. Another possible difficulty associated with increasing the number of connections is a lack of space.

[0099] Figure 9 depicts an actuator system 1 in accordance with an embodiment. The actuator system 1 comprises a thermal conditioning plate 25 and one or more superconducting coils 2 (e.g., desirably a plurality of superconducting coils). The one or more superconducting coils 2 are for magnetically levitating and linearly displacing stage 29 thereon. The actuator system 1 and the stage 29 may be any positioner and support within, for example, a lithographic apparatus. For example, the stage 29 may be a patterning device support MT for the patterning device MA and the actuator system 1 may be part of the first positioner PM. Alternatively or additionally, the stage 29 may be the substrate support WT, and the actuator system 1 may be the second positioner PW. The stage 29 may include a long-stroke component, which supports a short-stroke actuator as described herein. The stage 29 has one or more coils or one or more magnets, as applicable, to interact with one or more superconducting coils 2.

[0100] As shown in Figure 10, the thermal conditioning plate 25 may comprise an internal passage network 26 for flowing a cryogen therein. As a result, the thermal conditioning plate 25 may be thermally conditioned, e.g., cooled, by the cryogen flowing within the internal passage network 26. As shown, one or more superconducting coils 2 is in thermal contact with an external surface 27 of the thermal conditioning plate 25. More specifically, the one or more superconducting coils 2 may bedisposed on the external surface 27 of the thermal conditioning plate 25. The one or more superconducting coils 2 may be directly disposed on the external surface 27. The one or more superconducting coils 2 may be in thermal contact with the external surface 27 of the thermal conditioning plate 25 without coming into direct contact with (e.g., being submerged in) the cryogen. Alternatively, the one or more superconducting coils 2 may be embedded in the thermal conditioning plate 25 and may be in direct contact with (e.g., being submerged in) the cryogen.

[0101] Furthermore, as shown in Figure 10, the internal passage network 26 may be substantially co-extensive with the one or more superconducting coils 2. That is, the internal passage network 26 may have a lateral extent which is similar to or substantially the same as the lateral extent of the one or more superconducting coils 2. This may help improve the uniformity of the thermal conditioning, e.g., cooling provided to the one or more superconducting coils 2.

[0102] Because the cryogen is flowed in the internal passage network 26 within the thermal conditioning plate 25, compared with providing cooling at a limited number of connection spots of a cryocooler, the one or more superconducting coils 2 can be thermally conditioned, e.g., cooled, evenly. In other words, the temperature distribution of the one or more superconducting coils 2 can become more uniform. This, in turn, may result in a more uniform performance of the one or more superconducting coils 2.

[0103] Furthermore, because cooling is provided via the internal passage network 26 instead of multiple connection points of multiple cryocoolers, the actuator system 1 may be more compact, which may be desirable as space around the actuator system 1 may be limited. Specifically, the overall mass of the moving parts of the actuator system 1 may be reduced. This may reduce the amount of vibration generated during operation.

[0104] Furthermore, because the cryogen flows within the thermal conditioning plate 25, the cryogen that is within the thermal conditioning plate 25 at a given moment may provide a buffer capacity against a quench event. A quench event refers to a change of state of an electromagnet from superconducting to non-superconducting, resulting in an increase in electrical resistance. The increase in electrical resistance may initially be small as the electromagnet may only be slightly non-superconducting. However, the increase in electrical resistance may, in turn, cause a certain amount of heat to be generated (by Joule heating) as electricity continues to flow through the one or more coils. In the absence of an adequate heat sink or heat transfer path, this results in a further temperature rise in the one or more electromagnet coils, and a corresponding rise in electrical resistance in a self-reinforced, run-away fashion. In particular, quench may typically initiate at a localized point in an otherwise superconducting electromagnet and may propagate as a thermal wave to adjacent portions of the electromagnet, thereby causing further portions of the electromagnet to become non-superconducting. A chain reaction may thus ensue and may cause a total loss of superconductivity in the entire electromagnet. For example, all the superconducting coils may be in series and thus, in the case of a quench, all of the superconducting coils may not function anymore. A quench event is thereforeundesirable and may also cause irreversible weakening of the material of the thermal conditioning plate 25.

[0105] The likelihood of a quench event can be reduced by increasing the heat sink. For example, a passive heat sink may be provided. For example, passive heat sink may be provided by thermally contacting the one or more superconducting coils 2 with a thermal mass, such as a thermally conductive (e.g. copper or aluminum) plate. For example, the material of the thermal conditioning plate 25 may provide some passive heat sink capacity.

[0106] However, active heat absorption capacity may be desirable. As noted above, the cryogen that is within the thermal conditioning plate 25 at a given moment may provide additional heat absorption capacity. Specifically, because the material of the thermal conditioning plate 25 may have a reduced heat capacity at cryogenic temperatures, the presence of the cryogen within the thermal conditioning plate 25 may provide additional heat absorbing capacity to the thermal conditioning plate 25 in case of unplanned shutdown, for example. More specifically, the cryogen may be able to maintain the thermal conditioning plate 25 at a cryogenic temperature while absorbing a large amount of heat from the one or more superconducting coils 2, notably as latent heat of fusion and / or latent heat of vaporization. Other active techniques such as dump resistors and quench back heaters may be additionally employed.

[0107] An advantage associated with flowing the cryogen in an internal passage network 26 is that sloshing may be reduced. That is, if the internal passage network 26 shown in Figure 10 were replaced by a single plenum in which the cryogen is provided, during operation of the lithographic apparatus, the cryogen may slosh around in the plenum, which may create greater mechanical vibrations. More specifically, when an enclosed volume (e.g. a single plenum) containing a fluid is subjected to acceleration, the fluid itself is also caused to accelerate. This non-flow-induced acceleration (i.e. sloshing) acts as an acoustic disturbance and generates pressure waves within the enclosed volume. These pressure waves may then travel through the fluid line (at the speed of sound) and may introduce dynamic pressures which lead to dynamic deformations (i.e. vibrations). By contrast, by employing an internal passage network 26, any movement of the cryogen is restricted within the passages of the internal passage network 26, which in turn limits mechanical vibrations.

[0108] The thermal conditioning plate 25 may be variously constructed. For example, the thermal conditioning plate 25 may comprise a thermally conductive material. Examples of thermally conductive materials include aluminum, copper, an aluminum alloy, and / or a copper alloy. The thermal conditioning plate 25 may comprise a material of high stiffness, such as stainless steel. High stiffness may be desirable as it may allow the thermal conditioning plate 25 to withstand sharp acceleration forces during operation. High stiffness may be achieved through a choice of material and / or constructional design. Depending on the manufacturing method, the thermal conditioning plate 25 may be constructed of a single material, or may be constructed of several materials. In particular, the thermal conditioning plate 25 may be constructed of several materials of different thermal conductivities.

[0109] For example, the thermal conditioning plate 25 may be formed by casting, in which case theinternal passage network 26 may be formed directly during the casting process. Alternatively, the thermal conditioning plate 25 may be manufactured initially as two plates, with open channels machined into one or both plates, which plates may then be bonded together using e.g., vacuum brazing or other suitable means to close the channels that form the internal passage network 26. Alternatively, the thermal conditioning plate 25 may be formed by fitting pipes that are forged into the required shape into corresponding machined channels on a surface of the thermal conditioning plate 25. The forged pipes may be tightly fitted in the thermal conditioning plate 25 so that the forged pipes and the material of the thermal conditioning plate 25 make a good thermal contact. As another alternative, the thermal conditioning plate 25 may be formed by drilling parallel bores through a solid plate, and closing the surface holes using plugs. As yet another alternative, the thermal conditioning plate 25 may be formed by forging pipes to the required shape of the internal passage network 26, and by casting the thermal conditioning plate 25 around the forged pipes. In particular, in this manufacturing method, the pipes may be made of stainless steel, which pipes may be cast in aluminum (or an aluminum alloy), which has a lower melting point, to form the thermal conditioning plate 25. It should be understood that these manufacturing methods are only non-limiting examples; other suitable manufacturing methods may be used to form the thermal conditioning plate 25.

[0110] The internal passage network 26 may have different geometries or topologies. Generally, the internal passage network 26 may comprise one or more elongated passages which cover an extent within the thermal conditioning plate 25. Figures 12A and 12B show two non-limiting examples of the internal passage network 26. As shown in Figure 12A, the internal passage network 26 may have a serpentine shape. In one example, the internal passage network 26 may be a single continuous passage with no branches. Alternatively, the internal passage network 26 may have branches. For example, Figure 12B shows an internal passage network 26 which comprises a series of passages which are connected in parallel. In this arrangement, a restrictor 223 may be provided at or near the entrance to each individual parallel passage, so that the internal passage network 26 may be calibrated to provide even cryogen flow through the parallel passages. Furthermore, in the arrangement of Figure 12B, the cryogen supply line 61 and the cryogen return line 62 may be provided at opposite ends of the series of parallel passages, which may help equalize the flow among the parallel passages.

[0111] The internal passage network 26 may be formed into any other suitable geometries. For example, the internal passage network 26 may have a labyrinthine geometry. The elongate shape of the internal passage network 26 may help reduce sloshing. Furthermore, the presence of bends in the internal passage network 26 may also help reduce sloshing. Specifically, sloshing may be reduced by reducing the number and / or length of straight passages.

[0112] It should be understood that the serpentine shape of Figure 12A and the parallel-passage arrangement of Figure 12B may be combined in a single internal passage network 26. It should also be understood that the internal passage network 26 may comprise several subsections, each of which may have the same or different geometry, and the subsections may be interconnected or isolated from oneanother. Furthermore, different subsections may be arranged laterally within the thermal conditioning plate 25, and / or may be stacked in the thickness direction of the thermal conditioning plate 25.

[0113] Different cryogens can be used to thermally condition, e.g., cool the thermal conditioning plate 25. Table 1 below lists examples of suitable cryogens together with some of their relevant thermodynamic properties. The ranges between their triple point and critical point identify their potential use for a flow boiling application. “Flow boiling” refers to evaporative cooling whereby a continuous flow of coolant evaporates as it flows through / past a heat source. By contrast, “pool boiling” refers to evaporative cooling wherein a non-flowing pool of coolant evaporates as it absorbs heat. Flow boiling is generally a more efficient cooling mechanism (in terms of Watts per unit amount of coolant). In particular, helium is suitable for a multiphase flow heat transfer application (albeit at superfluid conditions, lower than the point) down to 1.9 K. Alternatively, a multiphase flow cooling application with a target temperature of 20 K can be achieved using para-hydrogen. For another example, for an operation temperature of 25 K, liquid neon or hydrogen may be used. For 60 K, coolants such as fluorine or oxygen may be used. Generally, the coolant may be chosen so that the operation temperature falls above the triple point (so that the coolant does not solidify) and below the critical temperature (so that the coolant does not evaporate) of the coolant.Table 1

[0114] By way of a non-limiting example, in a 1.2 m to 2.4 m wide and 40 mm thick thermal conditioning plate 25 constructed out of aluminum, with an internal passage network 26 having passages of 20 mm diameter, assuming a modest heat transfer coefficient (e.g., 20 Wm-2K_1at 20K), thetemperature variance across the external surface 21 may be less than 0.02 K with an embodiment as described herein. At 20 K, liquid hydrogen is at its boiling point at 0.934 bar. At this pressure and temperature, liquid hydrogen has a latent heat of 445 kJ / kg and a density of around 71.1 kg / m3. Assuming a flow velocity of 0.1 m / s and a pipe diameter of 20 mm, the mass flowrate can be calculated as 2.2 g / s. Assuming complete evaporation of the liquid cryogen, the cooling capacity due to phase change is estimated to be 1 kW at 20 K, which is much larger than achievable by known arrangements in which a cryocooler is in thermal contact with the thermal conditioning plate at a spot connection. Furthermore, in this example, the cryogen may provide a surplus cooling capacity that can be used as a margin against a quench event or a power disruption. For example, assuming a normal heat load of 100 W at 20K, only about 10% of the cryogenic fluid would evaporate during normal operation and remaining 900 W may serve as a safety margin for a potential quench event. It should be understood that different dimensions, choice of cryogen, operating temperature, flow rates and / or flow velocities may be used depending on the specific implementation.

[0115] As noted above, the internal passage network 26 may comprise multiple sections. For example, as shown in Figure 10, the internal passage network 26 may comprise a first passage section221 and a second passage section 222. As shown, the first passage section 221 may be located relatively close to the one or more superconducting coils 2, and the second passage 222 may be located relatively further away from the one or more superconducting coils 2. Furthermore, the second passage section222 may be downstream of the first passage section 221. That is, the cryogen may first flow through the first passage section 221 before flowing through the second passage section 222. The temperature of the cryogen may absorb heat from the superconducting coils 2 as it flows through the first passage section 221, and then through the second passage section 222. As the first passage section 221 may be located closer to the plurality of superconducting coils 2, heat from the superconducting coils 2 may be effectively transferred into the cryogen in the first passage section 221, which may be at a lower temperature than the cryogen in the second passage 222.

[0116] In order for the thermal conditioning plate 25 to reach and remain at cryogenic temperatures without using excessive cooling power, it may be beneficial to thermally insulate the thermal conditioning plate 25 and the one or more superconducting coils 2 from the outside environment. For example, as shown in Figure 9, the actuator system 1 may further comprise a vacuum / low pressure vessel 28. The vessel 28 may define a chamber 41 in which the thermal conditioning plate 25 and the one or more superconducting coils 2 is located and may enclose the thermal conditioning plate 25 and the one or more superconducting coils 2.

[0117] Low pressure (e.g., pressure at or below 20 Pa, pressure at or below 10 Pa, pressure at or below 5 Pa, pressure at or below 1 Pa, pressure at or below 0.1 Pa, pressure at or below 0.01 Pa, pressure at or below 0.001 Pa, or pressure at or below 0.0001 Pa) may be applied to the space within the vessel 28. A pump (not shown) may be connected to the volume of space within the vessel 28 for this purpose. The pump may also help prevent a build-up of solids on cold surfaces. Specifically, when a surfacereaches cryogenic temperature (e.g. less than 44K), any molecule (except helium, neon or hydrogen, for example) that comes into contact with the cold surface will solidify and will no longer be present as a free gas. This may in turn reduce the pressure within the vessel 28 even without the help of a pump. However, it may be undesirable to allow solidified condensates to build up because this may degrade thermal performance and / or create electrical short circuits (e.g. between the thermal conditioning plate 25 and the vessel 28). To avoid a build-up of solids, the pump may be used to evacuate molecules from within the vessel 28 before cooldown.

[0118] Furthermore, as molecules that are present in the vessel 28 would promote convective heat transfer, the presence of molecules may lengthen the time it takes to cool the thermal conditioning plate 25 down to target temperature. Therefore, by evacuating the vessel 28 before cooldown, the time and energy it takes to cool the thermal conditioning plate 25 may be reduced.

[0119] Although vacuum is an effective means of heat insulation, other means of heat ventilation may be used instead.

[0120] The actuator system 1 may alternatively or additionally comprise a thermal shield 30 to improve thermal insulation. As shown in Figure 9, the thermal shield 30 may form a chamber 31 in which the thermal conditioning plate 25 and the one or more superconducting coils 2 is located and may enclose the thermal conditioning plate 25 and the one or more superconducting coils 2. Where a vessel 28 is present, the thermal shield 30 may also be enclosed within the vessel 28.

[0121] With this arrangement, by way of a non-limiting example, it may be possible to maintain the thermal conditioning plate 25 and the one or more superconducting coils 2 at around 44 K or less, desirably 10 to 35 K, desirably 20 K or less. The thermal shield 30 may be maintained at around 50 to 90 K. The vessel 28 may be maintained at room temperature, i.e. around 295 K. It should be understood that the low pressure applied within the vessel 28 need not be a perfect vacuum. For example, the pressure within the vessel 28 may be maintained at around 10 Pa or less.

[0122] To further improve thermal insulation for the thermal conditioning plate 25, the thermal shield 30 may also comprise an internal passage network 32 for flowing a cryogen therein. This may further reduce the temperature within the thermal shield 30, which may help ensure that the thermal conditioning plate 25 and the one or more superconducting coils 2 can be maintained at a desired cryogenic temperature. To further improve thermal insulation, additional thermal shields similar to thermal shield 30 may be provided, subject to the availability of space.

[0123] As shown in Figure 9, the vessel 28 may comprise a penetration 43 through which the cryogen is supplied to the internal passage network 26 of the thermal conditioning plate 25. For example, as shown in Figure 9, a cryogen supply line 61 may be provided through the penetration 43, and may be connected to the internal passage network 26 of the thermal conditioning plate 25. Where there is a thermal shield 30, the thermal shield may be provided with a penetration 33 to allow the cryogen supply line 61 therethrough to reach the thermal conditioning plate 25. Cryogen for the internal passage network 32 of the thermal shield 30 may similarly be supplied through the penetration 43 of the vessel28. More generally, any required number of cryogen supplies may be provided through the penetration 43 of the vessel 28 (and optionally the penetration 33 of the thermal shield 30). Compared with contacting multiple cryocoolers with the thermal conditioning plate at multiple spot connections, which requires a corresponding number of penetrations, the present arrangement may reduce the number of penetrations required.

[0124] Furthermore, as shown in Figure 9, the actuator system 1 may comprise a flexible conduit 66 provided through the penetration 43 of the vacuum vessel 28. Cryogen may be supplied to internal passage network 26 of the thermal conditioning plate 25 and / or to the internal passage network 32 of the thermal shield 30 through this flexible conduit 66. The flexibility of flexible conduit 66 may be beneficial for accommodating movements of the thermal conditioning plate 25, the thermal shield 30, and / or the vessel 28 during operation. The thermal conditioning plate 25 may move as much as 10 to 100 mm, e.g. 50 mm. This may be caused by movements of the vessel 28 during movement operation of the actuator system 1, e.g., during scanning operation of a lithographic apparatus. Alternatively or additionally, the thermal conditioning plate 25 may move due to thermal shrinkage. Furthermore, in order to accommodate such movements, one or more selected from: the thermal conditioning plate 25, the thermal shield 30, and / or the vessel 28 may be mechanically suspended rather than rigidly fixed. For example, one or more flexible mechanical supports (not shown) may mechanically connect the thermal conditioning plate 25 and the vessel 28. These one or more mechanical supports may be provided through clearance holes in the thermal shield 30. The vessel 28, in turn, may also be similarly attached to the apparatus (e.g., lithographic apparatus) using one or more flexible mechanical supports. Generally, it may be desirable for these one or more mechanical supports to have low thermal conduction so as to reduce the amount of heat from the external environment reaching into the thermal conditioning plate 25. For example, the one or more mechanical supports may comprise a material having low thermal conductivity. The one or more mechanical support may have a small cross-sectional area.

[0125] In the simplest case, the cryogen supplied to the internal passage network 26 may be vented to the environment after it has passed through the internal passage network 26. However, as this may be wasteful, the cryogen supplied to the internal passage network 26 may be recycled. For example, as shown in Figure 9, in addition to a cryogen supply line 61 through which the cryogen flows towards the internal passage network 26, the actuator system 1 may comprise a cryogen return line 62 through which the cryogen flows away from the internal passage network 26. As shown in Figure 9, both the cryogen supply line 61 and the cryogen return line 62 may be provided within the flexible conduit 66. That is, both the cryogen supply and return lines 61, 62 may be provided through the same penetration 43 of the vessel 28. Compared with providing the cryogen supply and return lines 61, 62 through separate flexible conduits and separate penetrations, providing the cryogen supply and return lines 61, 62 through the same flexible conduit 66 or the same penetration 43 may reduce the number of flexible conduits and penetrations required. This, in turn, may reduce the amount of heat from the external environmentreaching into the thermal conditioning plate 25.

[0126] In order to provide electrical power to the one or more superconducting coils 2, one or more power supply leads 63 may be used. As shown in Figure 9, the one or more power supply leads 63 may be provided within the flexible conduit 66. Specifically, the one or more power supply leads 63 may be provided in the same flexible conduit 66 as the cryogen supply line 61. The one or more power supply leads 63 may generally be required to carry a large amount of electric current, e.g., 1 kA to 5 kA, or at least 2 kA. In view of the large electric current carried by the one or more power supply leads 63, it may be beneficial to cool the one or more power supply leads, so as to reduce resistive losses. For this purpose, the one or more power supply leads 63 may be surrounded by cryogen. In particular, the one or more power supply leads 63 may be surrounded by the same cryogen as that supplied to the internal passage network 26 of the thermal conditioning plate 25. The one or more power supply leads 63 may be superconducting. A further benefit of using one or more superconducting power supply leads 63 is that a cross-sectional width (e.g., diameter) of the one or more power supply leads 63 may be reduced without increasing resistive losses.

[0127] More specifically, as shown in Figure 9, the one or more power supply leads 63 may be provided within the cryogen supply line 61 and / or the cryogen return line 62. Advantageously, as shown in Figure 11, each of the cryogen supply lines 61 and the cryogen return line 62 may have one of the power supply leads 63 provided within. More particularly, as shown in Figure 11, one power lead 63 may be surrounded by cryogen 610 in the cryogen supply line 61, and another power lead 63 may be surrounded by cryogen 620 in cryogen return line 62. By providing one power supply lead 63 in each of the cryogen supply line 61 and the cryogen return line 62, instead of providing two (or more) power supply leads 63 in a single cryogen supply or return line 61, 62, the cryogen supply line 61 and / or the cryogen return line 62 may have a relatively smaller cross-sectional width (e.g., diameter), which may render the cryogen supply line 61 and / or the cryogen return line 62 more flexible. A greater flexibility may enable the cryogen supply line 61 and the cryogen return line 62 to better accommodate movement of the thermal conditioning plate 25, and / or the thermal shield 30, and / or the vessel 28. Furthermore, by combining power supply, cryogen supply and low pressure / vacuum supply in the same flexible conduit 6, compactness may be improved.

[0128] As the flexible conduit 66 may be of a certain length necessary for accommodating the movement of the thermal conditioning plate 25, the thermal shield 30, and / or the vessel 28, the cryogen may absorb heat from the external environment while flowing in the flexible conduit 66. In order to reduce the amount of heat from the external environment reaching into the cryogen within the flexible conduit 66, low pressure / vacuum may be applied to the space 60 between the cryogen supply and return lines 61, 62 and the flexible conduit 66. In one arrangement, as shown in Figure 9, this interstitial space 60 (i.e. the space between the cryogen supply and return lines 61, 62 and the flexible conduit 66) may be fluidly connected to the internal volume of the vessel 28. With this arrangement, low pressure I vacuum may be applied to the internal volume of the vessel 28 and the interstitial space 60 of theflexible conduit 66 using a common low pressure I vacuum source, such as a pump. Alternatively, the interstitial space 60 of the flexible conduit 66 and the internal volume of the vessel 28 may be fluidly non-connected, and low pressure / vacuum may be applied separately.

[0129] In order to reuse the cryogen, the actuator system 1 may comprise a cryogen recycling unit 70, as shown in Figure 9. The cryogen recycling unit 70 may be configured to receive the cryogen from the internal passage network 26, cool the received cryogen, and supply the cooled cryogen to the internal passage network 26. For example, the cryogen received from the internal passage network 26 may be cooled by a cryocooler 73 before being returned to the internal passage network 26.

[0130] In addition, the cryogen recycling unit 70 may comprise a control system (not shown) to control the flow rate, pressure, and / or temperature of the cryogen supplied to the internal passage network 26. For example, it may be desirable to keep the cryogen in the liquid state throughout the internal passage network 26 of the thermal conditioning plate 25. Therefore, the control system may be configured to control the flow rate, pressure and / or temperature of the cryogen supplied to the internal passage network 26 so that the temperature of the cryogen received from the internal passage network 26 is at or below the boiling point of the cryogen. This may be desirable because the cryogen in its liquid state may have a greater volume metric heat capacity than in the gaseous state. Furthermore, by helping ensure that the entire internal passage network 26 is filled with the cryogen in its liquid state, the cryogen within the internal passage network 26 may have a greater capacity of heat absorption, so that the thermal conditioning plate 25 may be more able to cope with an unplanned quench event.

[0131] More generally, the control system may be configured to control the flow rate, pressure and / or temperature of the cryogen supplied to the internal passage network 26 such that the cryogen remains in a single phase throughout the internal passage network 26. The single phase may be gaseous, liquid or supercritical.

[0132] In an embodiment, the control system may be configured to control the flow rate, pressure and / or temperature of the cryogen supplied to the internal passage network 26 such that a portion of the cryogen changes from the liquid state to the gaseous state as it flows through the internal passage network 26. In other words, the cryogen may gradually boil as it absorbs latent heat of vaporization as it flows through the internal passage network 26 of the thermal conditioning plate 25. This arrangement may be beneficial because boiling occurs at a substantially constant temperature, which may in turn help reduce temperature variation across the thermal conditioning plate 25. Furthermore, the control system may be configured to control the flow rate, pressure and / or temperature of the cryogen supplied to the internal passage network 26 such that an adequate reserve of liquid cryogen remains at the exit of the internal passage network 26. This reserve of liquid cryogen may provide additional heat absorption capacity in case of an unplanned quench event.

[0133] An advantage of allowing a portion of the cryogen to boil as it flows through the internal passage network 26 is that a two-phase flow may have a superior vibration damping property. For example, a two-phase flow may help reduce sloshing. In short, interfacial waves between the two phasesmay act as an energy dissipating mechanism and hence provide additional acoustic and mechanical damping. A damping ratio of about 2 to 3% is achievable using two-phase flow, whereas the actual structural damping in most single-phase systems is much less than 1%. Compared with single-phase flow, a smaller amount of two-phase fluid may be used while maintaining the substantially same damping performance.

[0134] In an embodiment, the control system may be configured to control the flow rate, temperature and / or pressure of the cryogen supplied to the internal passage network 26 such that the cryogen is in slush form. In other words, the cryogen supplied to the internal passage network 26 may comprise solid particles of the cryogen suspended in the cryogen in liquid form. The presence of the solid cryogen may cool the one or more superconducting coils 2 to a temperature lower than achievable with the same cryogen in liquid or gaseous form, and may provide a greater reserve of heat absorption capacity for an unplanned quench event. At the same time, the use of the cryogen in slush form, as opposed to purely solid, may enable the cryogen to be transported like a liquid.

[0135] The temperature of the cryogen supplied to the internal passage network 26 may be variously controlled. For example, the temperature of the cryogen may be controlled by varying its pressure. More specifically, a pressure reduction may induce a drop of the saturation temperature of the cryogen. As shown in Figure 9, cryogen may be supplied from the cryogen recycling unit 70 to the internal passage network 26 of the thermal conditioning plate 25 through a cryogen supply line 61. In order to control the temperature of the cryogen supplied to the internal passage network 26, the control system may comprise a cryogen pressure controller 71 installed on the supply line 61. The cryogen pressure controller 71 may cause a pressure drop of the cryogen as it flows from an upstream section 611 of the cryogen supply line 61 to a downstream section 612 of the cryogen supply line 61. The cryogen pressure controller 71 may control the amount of pressure drop of the cryogen. By controlling the amount of pressure drop, the temperature of the cryogen in the downstream section 612 of the supply line 61 may be controlled.

[0136] Furthermore, the cryogen pressure controller 71 may be located relatively close to the thermal conditioning plate 25. That is, the downstream section 612 of the cryogen supply line 61 may be shorter than the upstream section 611 of the supply line 61. This may be beneficial because the amount of heat absorbed by the cryogen while in the cryogen supply line 61 may be difficult to predict. By placing the cryogen pressure controller 71 relatively close to the point of use (i.e. close to the thermal conditioning plate 25), the conditions of the cryogen actually supplied to the internal passage network 26 may be controlled with greater accuracy.

[0137] The actuator system 1 may further comprise a buffer tank 72 configured to hold a volume of the cryogen. The cryocooler 73 may cool the cryogen using a cooling circuit 731. As shown in Figure 9, the cooling circuit 731 may comprise a heat exchanger 721 configured to cool the cryogen in the buffer tank 72. The working fluid within the cooling circuit 731 may be helium in an embodiment. The buffer tank 72 may provide a thermal buffer as a relatively large amount of cryogen can be maintainedat the desired temperature during planned or unplanned shutdown (e.g., during maintenance or a short power disruption). When the shutdown is over, the cool-down process of the system can be shortened compared to an arrangement without a buffer tank 72.

[0138] Although the buffer tank 72 and the cryocooler 73 are shown as separate components in Figure 9, it should be understood that these components may be provided within a single unit. It should further be understood that any cryogenic cooler, including off-the-shelf equipment, that is suitable for supplying cryogen to the thermal conditioning plate 25 may be used.

[0139] Although an embodiment may be implemented using a single cryogen, several cryogens may be used. For example, the actuator system 1 may comprise a supply of a first cryogen and a supply of a second cryogen (not shown). The first and second cryogens may be different. In particular, the second cryogen may have a lower boiling point than the first cryogen. The boiling points of the first and second cryogens may be compared at 1 atm. The positioner assembly 1 may switch between the first and second cryogens depending on the temperature of the thermal conditioning plate 25 at a given moment.

[0140] In particular, when reducing the temperature of the thermal conditioning plate 25 from a higher temperature towards a target temperature, the actuator system 1 may initially supply the first cryogen (higher boiling point) in the internal passage network 26, then subsequently switch to the second cryogen (lower boiling point). In particular, the actuator system 1 may be configured to supply the first cryogen to the internal passage network 26 as the thermal conditioning plate 25 cools, and may switch to the second cryogen when the temperature of the thermal conditioning plate 25 has reduced to or below the boiling point of the second cryogen. This may help ensure that the cryogen supplied to the internal passage network 26 remains in liquid form for a greater portion of the cooling process. This may be beneficial because a cryogen in liquid form may have a greater heat capacity than the same cryogen in gaseous form. More particularly, the second cryogen may be chosen to have a greater specific heat capacity than the first cryogen, so that the flow rate of cryogen may be reduced after switching to the second cryogen.

[0141] The first and second cryogens may be any two cryogens, e.g., selected from Table 1 above (Table 1 lists the cryogens in ascending order in terms of boiling points from left to right). For example, the first cryogen may be liquid nitrogen, and the second cryogen may be para-hydrogen. As can be seen in Table 1, it may be beneficial to switch to para-hydrogen as the second cryogen because para-hydrogen has a relatively large heat of vaporization. For another example, the first cryogen may be liquid nitrogen, and the second cryogen may be liquid neon or liquid helium. In one example, the first cryogen may be used to cool the thermal conditioning plate 25 down to about 77 K (e.g. starting from room temperature) before switching to the second cryogen. The second cryogen may be used to further cool the thermal conditioning plate 25 to an operating temperature, such as down to about 20 K. The second cryogen may thereafter maintain the temperature of the thermal conditioning plate 25.

[0142] Where two cryogens are used, the internal passage network 26 of the thermal conditioning plate 25 may comprise first and second sub-networks (not shown) which are fluidly isolated from eachother. The actuator system 1 may be configured to supply the first cryogen to the first subnetwork, and to supply the second cryogen to the second subnetwork. The actuator system 1 may be configured to supply one, but not both, of the first and second cryogens to their respective sub-networks at any given time. As above, the switch between the first and second cryogens may be dependent on the temperature of the thermal conditioning plate 25. By fluidly isolating the first and second sub-networks, the first and second cryogens may be prevented from mixing. Furthermore, the actuator system 1 may switch between the first and second cryogens without first having to flush the cryogen supply line 61 and / or the cryogen return line 62. It should be noted that, where more than one cryogen is used, a separate set of cryogen supply and return lines 61, 62 and / or buffer tank 72 and / or cryocooler 73 may be provided for each cryogen.

[0143] Figure 13a depicts an actuator system 1 in accordance with an embodiment. The actuator system 1 comprises a thermal conditioning plate 25 and one or more superconducting coils 2 (e.g., desirably a plurality of superconducting coils). The one or more superconducting coils 2 are for magnetically levitating and linearly displacing stage 29 thereon. The actuator system 1 and the stage 29 may be any positioner and support within, for example, a lithographic apparatus. For example, the stage 29 may be a patterning device support MT for the patterning device MA and the actuator system 1 may be part of the first positioner PM. Alternatively or additionally, the stage 29 may be the substrate support WT, and the actuator system 1 may be the second positioner PW. The stage 29 may include a long- stroke component, which supports a short-stroke actuator as described herein. The stage 29 has one or more coils or one or more magnets, as applicable, to interact with one or more superconducting coils 2.

[0144] In an embodiment, the thermal conditioning plate 25 may comprise an internal passage (the same as or similar to internal passage network 26 described herein) for flowing a cryogen therein. As a result, the thermal conditioning plate 25 may be thermally conditioned, e.g., cooled, by the cryogen flowing therewithin. As shown, one or more superconducting coils 2 is in thermal contact with an external surface of the thermal conditioning plate 25. More specifically, the one or more superconducting coils 2 may be disposed on the external surface of the thermal conditioning plate 25. The one or more superconducting coils 2 may be directly disposed on the external surface. The one or more superconducting coils 2 may be in thermal contact with the external surface of the thermal conditioning plate 25 without coming into direct contact with (e.g., being submerged in) the cryogen. Alternatively, the one or more superconducting coils 2 may be embedded in the thermal conditioning plate 25 and may be in direct contact with (e.g., being submerged in) the cryogen.

[0145] In order for the thermal conditioning plate 25 to reach and remain at cryogenic temperatures without using excessive cooling power, it may be beneficial to thermally insulate the thermal conditioning plate 25 and the one or more superconducting coils 2 from the outside environment. For example, as shown in Figure 13a, the actuator system 1 may further comprise a vacuum / low pressure vessel 28. The vessel 28 may enclose the thermal conditioning plate 25 and the one or more superconducting coils 2.

[0146] Low pressure (e.g., pressure at or below 20 Pa, pressure at or below 10 Pa, pressure at or below 5 Pa, pressure at or below 1 Pa, pressure at or below 0.1 Pa, pressure at or below 0.01 Pa, pressure at or below 0.001 Pa, or pressure at or below 0.0001 Pa) may be applied to the space within the vessel 28. A vacuum / low pressure source (e.g., pump) 69 may be connected to the volume of space within the vessel 28 for this purpose via line 68. Although vacuum is an effective means of heat insulation, other means of heat ventilation may be used instead.

[0147] The actuator system 1 may alternatively or additionally comprise a thermal shield 30 to improve thermal insulation. As shown in Figure 13a, the thermal shield 30 may enclose the thermal conditioning plate 25 and the one or more superconducting coils 2. Where a vessel 28 is present, the thermal shield 30 may also be enclosed within the vessel 28.

[0148] With this arrangement, by way of a non-limiting example, it may be possible to maintain the thermal conditioning plate 25 and the one or more superconducting coils 2 at around 44 K or less, desirably 10 to 35 K, desirably 20 K or less. The thermal shield 30 may be maintained at around 50 to 90 K. The vessel 28 may be maintained at room temperature, i.e. around 295 K. It should be understood that the low pressure applied within the vessel 28 need not be a perfect vacuum. For example, the pressure within the vessel 28 may be maintained at around 10 Pa or less.

[0149] To further improve thermal insulation for the thermal conditioning plate 25, the thermal shield 30 may also comprise an internal passage (e.g., the same as or similar to internal passage network 32) for flowing a cryogen therein. This may further reduce the temperature within the thermal shield 30, which may help ensure that the thermal conditioning plate 25 and the one or more superconducting coils 2 can be maintained at a desired cryogenic temperature. To further improve thermal insulation, additional thermal shields similar to thermal shield 30 may be provided, subject to the availability of space.

[0150] As shown in Figure 13a, the vessel 28 may comprise a penetration 43 through which the cryogen is supplied to the thermal conditioning plate 25. For example, as shown in Figure 13a, a cryogen supply line 61 configured to supply cryogen to the thermal conditioning plate 25 may be provided from cryogen unit 81 through the penetration 43, and may be connected to the internal passage of the thermal conditioning plate 25. Where there is a thermal shield 30, the thermal shield may be provided with a penetration 33 to allow the cryogen supply line 61 therethrough to reach the thermal conditioning plate 25. Cryogen for the internal passage of the thermal shield 30 may similarly be supplied through the penetration 43 of the vessel 28. More generally, any required number of cryogen supplies may be provided through the penetration 43 of the vessel 28 (and optionally the penetration 33 of the thermal shield 30).

[0151] The thermal conditioning plate 25 may move as much as 10 to 100 mm, e.g. 50 mm. This may be caused by movements during movement operation of the actuator system 1, e.g., during scanning operation of a lithographic apparatus. Alternatively or additionally, the thermal conditioning plate 25 may move due to thermal shrinkage. In order to accommodate such movements, one or moreselected from: the thermal conditioning plate 25, the thermal shield 30, and / or the vessel 28 may be mechanically suspended rather than rigidly fixed. For example, one or more flexible mechanical supports 80 may mechanically connect the thermal conditioning plate 25 to the frame 15. These one or more mechanical supports may be provided through clearance holes in the vessel 28 and / or thermal shield 30. In an embodiment, thermal conditioning plate 25 may be attached to the vessel 28 and / or thermal shield 30 and the vessel 28 and / or thermal shield, in turn, may also be similarly attached to the frame 15 using one or more flexible mechanical supports 80. Generally, it may be desirable for these one or more mechanical supports to have low thermal conduction so as to reduce the amount of heat from the external environment reaching into the thermal conditioning plate 25. For example, the one or more mechanical supports may comprise a material having low thermal conductivity. The one or more mechanical support may have a small cross-sectional area. In an embodiment, the one or more mechanical supports enable the thermal conditioning plate 25 alone or in combination with the vessel 28 and / or thermal shield 30 to act as a balance mass, i.e., to absorb a reaction force and move in response thereto (in an embodiment, move relatively a small distance compared to the stage 29 due to a difference in mass between the stage 29 and the thermal conditioning plate 25 (or in combination with the vessel 28 and / or thermal shield 30)).

[0152] In the simplest case, the cryogen supplied to at least the thermal conditioning plate 25 to provide the cooling after it has passed through the internal passage may be vented. However, as this may be wasteful, the supplied cryogen may be recycled. For example, as shown in Figure 13a, a cryogen return line 62 can be provided through which the cryogen flows away from the thermal conditioning plate 25 to the cryogen unit 71 (which can have a recycling function, for example, as discussed above with respect to Figure 9). As shown in Figure 13a, both the cryogen supply line 61 and the cryogen return line 62 may be provided through the same penetration 43; however, it need not.

[0153] In order to provide electrical power to the one or more superconducting coils 2, one or more power supply leads 63 may be used to provide current from a power supply 82. As shown in Figure 13 a, the one or more power supply leads 63 may be provided separate from the cryogen supply line 61 and the cryogen return line 62; however, it need not and may be combined in a common conduit as shown in, for example, Figure 9. The one or more power supply leads 63 may generally be required to carry a large amount of electric current, e.g., 1 kA to 5 kA, or at least 2 kA. In view of the large electric current carried by the one or more power supply leads 63, it may be beneficial to cool the one or more power supply leads, so as to reduce resistive losses. For this purpose, the one or more power supply leads 63 may be surrounded by cryogen. In particular, the one or more power supply leads 63 may be surrounded by the same cryogen as that supplied to the thermal conditioning plate 25. The one or more power supply leads 63 may be superconducting.

[0154] In an embodiment, one or more power supply leads 63, cryogen supply line 61, cryogen return line 62 and / or line 68 is flexible. Such flexibility can allow movement of the thermal conditioning plate 25, vessel 28 and / or thermal shield 30 to occur without causing the respective one or more power supplyleads 63, cryogen supply line 61, the cryogen return line 62 and / or line 68 to fail, become disconnected, etc.

[0155] In an embodiment, as shown in Figure 13a, the cryogen unit 81, power supply 82 and / or the vacuum / low pressure source (e.g., pump) 69 is located in a floor 83 of the fabrication plant (fab), e.g., the sub-fab, and connected with flexures 80, in general mechanical supports, to the thermal conditioning plate 25, vessel 28 and / or thermal shield 30.

[0156] In case the thermal conditioning plate 25 alone or in combination with the vessel 28 and / or thermal shield 30 would act as a balance mass, the power leads 63, carrying the comparatively large current for powering the superconducting coils 2, need to have some flexibility. In order to reduce the resistive losses in the power leads 63, they may be cryogenically cooled. As a result of the application of comparatively thick conductors for the power leads 63 and the cryogenic cooling of said leads, it may be difficult to obtain a low flexibility for said power lead connection between the power supply 82 and the superconductive coils 2.

[0157] In an embodiment, it is therefore proposed to mount the power supply 82 to the vessel 28, when said vessel serves as a balance mass. By doing so, a desired flexibility of the power leads connection between the stationary world, e.g. the floor 83 and the superconductive coils 2 is achieved.

[0158] Figure 13b schematically shows a power supply 82 as can be applied in an embodiment of the present invention. The power supply 82 as schematically shown comprises an input terminal 82.1 which is configured to be connected to a main power supply 800, e.g. a three-phase AC power supply. The power supply 82 as applied to power one or more coils such as superconductive coils 2 will typically comprise a power converter 82.3 which converts the AC input power as received from the input terminal to a suitable output power for powering the one or more coils. In order to power one or more superconductive coils, a low voltage / high current DC output power is typically required. As mentioned above, the powering of the coils may require a current of 1 kA to 5 kA. As such, the power leads 86 exiting the output terminal 82.2 will typically have a comparative large cross-section and will thus be rather rigid, compared to the power leads 88 which connect the mains supply 800 to the input terminal 82.1 of the power supply 82.

[0159] Figure 13c schematically shows an embodiment of an actuator system 1 whereby the power supply 82 for powering the superconductive coils 2 is mounted to the vessel 28. Compared to the embodiment of Figure 13a, the vessel 28 is displaceable mounted on mechanical supports 80, thus allowing the vessel and its components to act as a balance mass for the stage 29. By mounting the power supply 82 to the vessel 28, the power lead connection 88 connecting the power supply 82 to the mains supply 800 may comprises comparatively thin electrical connectors or wires, thus resulting in a dynamic connection between the actuator assembly 1 and the frame 15 having a comparatively low stiffness. In the embodiment as shown, the power supply 82 is mounted adjacent to a penetration 44, to enable a transfer of power leads towards the superconductive coils 2. In the embodiment as shown, the power converter 82 is mounted to an external surface of the vessel 28. It can be pointed out that alternativearrangements can be considered as well. In particular, the power supply 82 can e.g. be mounted to an internal surface of the vessel 28. In an embodiment, the power supply 82 can e.g. be integrated in the space available between the vessel 28 and the thermal shield 30.

[0160] Figure 13d schematically shows an embodiment of an actuator assembly including a power supply 82 for powering a superconductive coil array 2. For clarity reasons, various components of an actuator assembly as e.g. shown in Figure 13c have been omitted in Figure 13d. In the embodiment as shown, a frame 16 is mounted to a bottom surface of the vessel 28, the power supply 82 being arranged in a cavity of the frame 16. Figure 13d further shows power supply leads 88 connecting the power supply 82, in particular the first terminal 82.1 of the power supply 82, to the mains supply 800, e.g. a three-phase AC power supply. In the embodiment as shown, the output terminal 82.2 of the power supply is provided in a penetration of the vessel 28, the power leads 86 being provided via a penetration of the thermal shield 30 to the array of superconductive coils 2, which are mounted to the thermal conditioning plate 25. In the embodiment as shown, the vessel 28 is supported on a frame 15, which can be a vibrationally isolated frame or a floor member, via the frame 16 and mechanical supports 80. Note that, in an embodiment, the vessel 28 can be directly supported on the frame 15 by means of the mechanical supports 80. In such embodiment, the mechanic supports 80 would be connected directly to the bottom surface of the vessel 28.

[0161] In an embodiment, a shuttle 84 is provided that effectively follows the stage 29 in at least one direction. For example, in an embodiment as depicted in Figure 13c, the shuttle 84 follows the stage in the Y-direction, whereas the stage 29 can move within at least the X-Y plane. Of course, the shuttle 84 can move in a different direction and may move in more than one direction. In an embodiment, the shuttle 84 can have an arm 85 relative to which the stage 29 can move, e.g., the stage 29 can move primarily in the X-direction with respect to the arm 85. Desirably, the stage 29 is in a primarily noncontact arrangement with respect to the arm 85. In an embodiment, the shuttle 84 is displaced by an actuator having at least part thereof on actuator structure 86. For example, actuator may comprises a linear motor (e.g., a coil and magnet linear motor) configured to actively suspend and displace the shuttle 84, wherein, for example, the coil or magnet is located in or on the actuator structure 86 and the other of the magnet or coil is located in or on the shuttle 84 (e.g., the bottom part of shuttle 84 extending across the actuator structure 86). In an embodiment, the actuator structure 86 may comprise a guide member to guide the motion of the shuttle 84 and to limit uncontrolled movement of the shuttle 84.

[0162] The shuttle 84 can have one or more functions. For example, the shuttle 84 can carry one or more lines / cables 87 (e.g., one or more electrical power lines, a fluid supply for, e.g., cooling, etc.) for stage 29. This can help reduce forces acting on the stage 29 as a result of such one or more lines / cables. In an embodiment, the lines / cables 87 are flexible or displaceable so as to be able to move with the stage 29. Thus, while the shuttle 84 supports the lines / cables 87, the lines / cables 87 can move relative to the shuttle 84 at least in part to follow the stage 29. In an embodiment, the shuttle 84 can include one or more sensors to enable position measurement system for the stage 29 (and optionally the shuttle 84itself). In an embodiment, the shuttle 84 can provide a crash interface for the stage 29. For example, if the positioning of the stage 29 becomes uncontrolled, the shuttle 84 can act to limit at least some further movement of the stage 29. As an example, the shuttle 84 can limit movement in one or more selected from: X direction, Y direction, Z direction, Rx direction, Ry direction and / or Rz direction. This limitation can occur through physical contact between a part of the stage 29 and the arm 85 of the shuttle 84. That is, for example, a part of the stage 29 can be configured to interact with a rail of the arm 85 in a crash situation. When the stage 29 is controlled, there is no contact between the part of the stage 29 and the rail of the arm but when the movement of the stage 29 becomes uncontrolled, the part of the stage 29 contacts the rail in such a way to limit undesired uncontrolled movement. Preventing or limiting such uncontrolled movement can, for example, help prevent damage to the one or more lines / cables. Preventing or limiting such uncontrolled movement can, for example, help limit forces, such as forces against one or more lines / cables. Preventing or limiting such uncontrolled movement can, for example, help prevent or reduce damage. In Figure 13c, the arm 85 is depicted as being relatively short merely as a convenience and to enable better depiction of all the components; in an embodiment, the arm 85 can be long enough to enable the stage 29 to reach as far across the coil layer 2 as desired (e.g., to or near one or more edges of the coil layer). In an embodiment, the shuttle 84 can dampen balance mass motions and / or vibrations. For example, the mass of an actively suspended shuttle 84 can act as tuned mass damper on one or more modes of the balance (e.g., a Ry mode).

[0163] In an embodiment, one or more other stages besides stage 29 can be provided to interact with coil layer 2. In an embodiment, that other stage could be an effective duplicate of the stage 29. In an embodiment, that other stage could comprise a utility support as described above that, for example, is arranged to hold a sensor and / or a cleaning device but not configured to hold a substrate. That other stage could primarily move at the right side of coil layer 2 shown in Figure 13. That other stage could have its own shuttle like shuttle 84. It could be, for example, located at the right side of the coil layer 2 shown in Figure 13. Of course, that other shuttle could have an actuator with a comparable actuator structure 86.

[0164] As schematically shown in Figure 13a above, the coil layer 2 can be an integrated structure. That is, while individual coils of the coil layer 2 may be individually manufactured, they are schematically depicted as assembled into a single, fairly rigid structure wherein the coils of the coil layer 2 are connected to each other. However there may be one or more disadvantages with this design. For example, in an embodiment, the coils of the coil layer 2 are mounted in series and so a possible failure can damage all the coils and / or a failure of one coil could require replacement of the whole coil layer 2 or complex, costly and time-consuming removal or repair of the failed coil. As another example, if a quench occurs, all the coils and the surrounding materials may be damaged. As discussed herein, quench in a superconductor is a sudden, unexpected and unrecoverable transition to a normal (nonenergized) state of a superconductor which result in the conversion of the stored energy into mostly heat, which can lead to destruction of the superconductor when not properly controlled. So, replacementor repair of all or part of the coil layer 2 after an uncontrolled quench event could be complex, costly and time-consuming. As another example, an integrated coil layer 2 may bend or warp in case it is not supported properly. So, fixing such a bend or warp can be complex, costly and time-consuming. As another example, an uncontrolled movement and / or stopping of the stage 29 may result in a crash on the coil layer 2, which may damage the coil layer 2 and / or its neighboring structure. Fixing the damage of such a crash can be complex, costly and time-consuming.

[0165] So, in an embodiment, the coil layer 2 is subdivided into a plurality of separable and discrete modules, each module having one or more coils of the coil layer 2 (desirably a plurality of coils, which are, for example, connected in series). In an embodiment, each module has an interface to allow at least electrical supply into the module. So, with the coil layer 2 subdivided into modules, repair and / or replacement can be, for example, easier, less time-consuming and less costly. For example, if there occurs an unplanned quench event, one can easily remove only the one or more modules that are affected by the quench, while leaving the unaffected modules in place. Then, the removed one or more modules can be repaired or simply replaced.

[0166] Referring to Figure 14, a highly schematic embodiment of a modular implementation of the coil layer is depicted. In Figure 14, a bottom view of the modular implementation of the coil layer 2 is depicted to be able to see an embodiment of the interface to allow electrical supply into the module. So, for example, the modular implementation of the coil layer 2 would be rotated 180 degrees for adding to the embodiment of Figure 13.

[0167] In Figure 14, six modules 88 are shown assembled together to form a coil layer 2. Of course, there may be fewer or more modules. In an embodiment, there are 4 or more modules, 6 or more modules, 10 or more modules, 20 or more modules, 50 or more modules, 100 or more modules or 500 or more modules. The assembled modules 88 can be considered comparable to at least the coil layer 2 of thermal conditioning plate 25. If there is supply of cooling into the modules for providing superconductivity in the modules as discussed below, then the assembled modules 88 can be considered comparable to the combination of the coil layer 2 and the thermal conditioning plate 25.

[0168] In an embodiment, each module 88 comprises an external structure 89 referred to herein, merely for convenience, as a superconducting coil block. Effectively, the superconducting coil block 89 is a box-like structure to contain one or more coils of the coil layer 2 therein, preferably a plurality of coils therein. For example, there can be 10 or more coils, 20 or more coils, 40 or more coil or 100 or more coil packaged in a superconducting coil block. The superconducting coil blocks introduce modularity which will help increase the ease of serviceability, manufacturability and assembly of the coil layer 2. In case of a failure of something inside a superconducting coil block, that superconducting coil block can be replaced directly by a new one instead of replacing the whole coil layer 2. So, service and maintenance cost and time can be decreased and desirably reliability and testability can be improved by doing discretizing coil arrangements within the coil layer 2. In an embodiment, the superconducting coil block can enclose the one or more coils therein; that is, the superconducting coil block can haveone or more walls to cover the top, bottom and one or more sides of the one or more coils of the associated module. In an embodiment, the superconducting coil block can have one or more walls to cover the bottom and one or more sides of the one or more coils therein and thus be open at the top. In an embodiment, the superconducting coil block can have a wall to cover just the bottom of the one or more coils, desirably extending out past the one or more sides of the one or more coils so as to provide a surface of the wall for mating with a surface of a wall of an adjacent module. In an embodiment, the superconducting coil block is made of non-conductive material.

[0169] In an embodiment, each module 88 comprise one or more interfaces 92 to allow admission of a service into the module, wherein the service comprises at least electrical supply for the coils in the module. In an embodiment, the service can have multiple components. For example, one of the components of the services may be cooling to provide for superconductivity of the coils in the module. In an embodiment, one of the components of services may be a one-way or two-way transmission of electrical signals from one or more sensors in a module. So, for example, in an embodiment, the one or more interfaces 92 allow supply of cooling in the module to provide for superconductivity of the coils in the module and / or the one or more interfaces 92 allow one-way or two-way transmission of electrical signals from one or more sensors in a module. In an embodiment, there can be a separate interface for component of the service or there can be a single interface for all of the components of the service.

[0170] In an embodiment, the one or more interfaces 92 can include one or more connectors to allow for relatively easy connection and disconnection of the service. In an embodiment, as shown in Figure 14, the one or more interfaces 92 are at a surface opposite from the surface across which the stage 29 moves, e.g., the bottom surface. Accordingly, there can be provided a connection structure (not shown) that provides one or more mating connectors for the one or more connectors of the one or more interfaces 92 of a module so that the connection structure provides the service to the module and in an embodiment, the structure can be integrated to provide the connectors for all, or a majority, of the modules 88. The connection structure could be, for example, a wall of vessel 28 and / or thermal shield 30 and / or frame 15. Desirably, the one or more service connections of all, or a majority, of the modules 88 are similar to bring commonality and simplicity to the design.

[0171] In an embodiment, additionally or alternatively, one or more modules 88 can have one or more interfaces 92 on one or more different surfaces, e.g., on one or more side surfaces. In that case, one or more modules 88 can connect to one or more other modules 88. So, in an embodiment, one or more modules 88 can be connected in a series arrangement with one or more other modules 88. For example, electrical connections can be at an inner side between two adjacent superconducting coil blocks 89 to make the coils in one module 88 in series with coils in another module 88.

[0172] In an embodiment, the service for each module 88 is controlled and optionally monitored in order to control the service for each module 88 separately and individually. Thus, for example, different electrical supply amounts can be provided to different modules 88 and where there is supply of cooling to the modules 88, different cooling amounts can be provided to different modules 88. This can helpprevent or response to a failure like quench, coil failure, etc.

[0173] In an embodiment, a control system of electronic hardware and / or software can be provided to provide the various service amounts and can optionally monitor for significant electrical variation and / or heat variation (e.g., using a signal from a sensor in a module 88) to provide an appropriate control signal to cut off service to a module 88, to change an amount of service to a module 88, etc. In an embodiment, where the modules 88 combine to form, for example, a magnet array, the control system can provide a tuning or calibration routine to tune and / or account for, for example, the magnetic field once the modules 88 are assembled. Such tuning can include, for example, adjusting current to one or more of the modules 88 to adjust the overall magnetic field of the modules 88. Such calibration can include, for example, adjusting the electrical supply to the stage 29 in accordance with a determined magnetic field of the assembled modules 88. Such tuning and / or calibration can be performed using measurements results from one or more sensors, such as one or more sensors in or attached to the modules 88 and / or one or more external sensors (such as a sensor temporarily used to measure the magnetic field of the assembled modules 88).

[0174] In an embodiment, each superconducting coil block has a substantially same configuration and construction to enable mass production and relative easy replacement. In an embodiment, one or more superconducting coil blocks can have a different configuration and construction than a majority of the superconducting coil blocks.

[0175] In an embodiment, one or more mechanical connections 93 are provided to connect a module to an adjacent module when the modules 88 are assembled together to form coil layer 2. In an embodiment, the one or more mechanical connections 93 can be separate from the superconducting coil block of a module 88, e.g., a fastener of any type. In an embodiment, the one or more mechanical connections 93 can be part of or integral with the superconducting coil block of a module, e.g., a protruding element to engage into, and desirably lock, with an opening of an adjacent module. In an embodiment, the mechanical connections 93 are placed at an inner side of a module between two adjacent superconducting coil block to make the assembled superconducting coil blocks relatively at least in the X and Y directions so, for example, a torsion or bending mode of the assembled modules, and thus assembled layer 2, can be improved. In an embodiment, the one or more mechanical connections 93 have a same, or similar, design so as to bring commonality and simplicity to the design.

[0176] In an embodiment, one or more struts 94 are provided at the periphery of the assembled modules to provide stiffness, e.g., in the Z direction, and / or provide crash protection, when the modules 88 are assembled together to form coil layer 2. In an embodiment, the one or more struts 94 are at the joint between adjacent superconducting coil blocks. In an embodiment, the one or more struts 93 can be separate from the superconducting coil block of a module 88, e.g., a solid body or fastener of any type. In an embodiment, the one or more struts 93 can be part of or integral with the superconducting coil block of a module, e.g., a solid element to engage into, and desirably lock, with a solid element of an adjacent module. In an embodiment, the one or more struts 93 have a same, or similar, design so asto bring commonality and simplicity to the design.

[0177] In an embodiment, one or more exterior connections 95 are provided at the periphery of the assembled modules 88 to fix the assembled modules to another body such as a thermal conditioning plate 25 and / or vessel 28 and / or thermal shield 30 and / or frame 15. In an embodiment, a structure 95 can be provided to which the assembled modules 88 are connected via the one or more exterior connections 95. This structure 95 can in turn be fixed to thermal conditioning plate 25 and / or vessel 28 and / or thermal shield 30 and / or frame 15. In an embodiment, the one or more exterior connections 95 can be any other location than shown in Figure 14.

[0178] In an embodiment, the superconducting coil block 89 of a module 88 has an exterior wall that is non-planar or comprises multiple surfaces (multi-surface), to match with an exterior wall of another module 88. In an embodiment, the matching comprises mating such that one surface of the exterior wall of the superconducting coil block 89 of one module contacts a surface of another module. In an embodiment, the matching comprises an interlock wherein the exterior wall of the superconducting coil block 89 of one module overlaps at least part of a wall of the other module, wherein the interlock does not require contact between the modules but can comprises contact. As will be appreciated, various types of configurations of a non-planar or multi-surface exterior wall can be provided. Several nonlimiting examples of such configurations are described below.

[0179] Referring to Figure 15A, an example configuration of a multi-surface exterior wall 97 of a superconducting coil block 89 is depicted. In this case, the multi-surface wall 97 comprises at least two surfaces, at least one of which matches (e.g., mates, interlocks, etc.) with a surface of an exterior wall of another module 88. In an embodiment, two or more surfaces of a multi-surface wall 97 match with one or more surfaces of an exterior wall of another module 88. In the example of Figure 15 A, the wall 97 of one module overlaps in the X-direction at least part of the wall of the adjacent module.

[0180] Figure 15B shows another example configuration of a multi-surface exterior wall 97 of a superconducting coil block 89. This wall 97 has a sawtooth-type configuration which, in this embodiment, interlocks with a wall of another module, which wall of the other module also has a multisurface wall with a sawtooth-type configuration. In the example of Figure 15B, the wall 97 of one module overlaps in the X-direction at least part of the wall of the adjacent module on at least two occasions.

[0181] Figure 15C shows an example configuration of a non-planar exterior wall 98 of a superconducting coil block 89. This wall 98 has a wave-type configuration which, in this embodiment, interlocks with a wall of another module, which wall of the other module also has a non-planar wall with a wave-type configuration. In the example of Figure 15C, the wall 98 of one module overlaps in the X-direction at least part of the wall of the adjacent module.

[0182] In an embodiment, a cross-section of the superconducting coil block 89 in a plane parallel to a layout of the plurality of superconductive coils, e.g., coil layer 2 is non-rectangular. For example, as seen in each of Figures 15A, 15B and 15C, there is shown a non-rectangular cross-section of thesuperconducting coil block 89 (which differs from the rectangular cross-section of each module 88 shown in Figure 14). As will be appreciated, the cross-section may have a shape different from those depicted.

[0183] In an embodiment, the exterior non-planar or multi-surface wall 97 has a portion thereof that protrudes at the exterior from the module and at least one coil 99 is arranged to extend at the interior at least partly within the portion. As seen in each of Figures 15A, 15B and 15C, examples of coils 99 are identified that extend at least partly into a protrusion formed by the exterior non-planar or multi-surface wall 97. This configuration allows for, for example, a hexagonal array or lattice arrangement of coils that spans across the modules. Of course, this configuration could also allow for types of array or lattice arrangements, such as coils aligned in an array or lattice other than a square array or lattice. In an embodiment, the array or lattice has substantially equal periods in the X and Y directions.

[0184] So, in an embodiment, there is provided a superconductive assembly for an actuator, the assembly comprising, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils are grouped in a plurality of separable and discrete modules 88 which, when assembled, form the assembly, each module comprising a subset of one or more coils 2 of the plurality of coils and comprising an electrical interface 92 to provide electricity to the subset of one or more coils. In an embodiment, each module comprises a cooling interface to provide cooling for the superconductivity of the subset of one or more coils. In an embodiment, at one least module has an exterior non-planar or multi-surface wall, such as wall 97, 98. In an embodiment, adjacent modules of the modules each have the exterior non-planar or multi-surface wall and the exterior non-planar or multi-surface walls are designed so as to interlock with each other. In an embodiment, the exterior non-planar or multi-surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at the interior at least partly within the portion. In an embodiment, the exterior non-planar or multi-surface wall is an exterior multisurface wall that comprises two substantially planar sub-walls that meet to form a line (e.g., a straight line, a curved line, a zig zag line, etc.). In an embodiment, the superconductive coils are configured to generate, during use, a 2D spatially alternating magnetic field. In an embodiment, the electrical interface is located at a wall other than the one or more walls arranged to interface with one or more adjacent modules. In an embodiment, the plurality of superconductive coils are configured to cooperate with a mover of the actuator, and the assembly further comprises one or more further superconductive coils configured to cooperate with a separate body from the mover, the plurality of superconductive coils and the one or more further superconductive coils having a common cooling arrangement to provide cooling for the superconductivity.

[0185] In an embodiment, there is provided a magnet body for a planar motor, the magnet body comprising, during use, a plurality of superconductive coils that are configured to, during use, generate a 2D spatially alternating magnetic field, wherein the plurality of superconductive coils are grouped in a set of separable and discrete modules 88 which, when assembled, form the magnet body, each modulecomprising a subset of the plurality of coils. In an embodiment, at one least module has an exterior non- planar or multi-surface wall. In an embodiment, adjacent modules of the modules each have the exterior non-planar or multi-surface wall and the exterior non-planar or multi-surface walls are designed so as to interlock with each other. In an embodiment, the exterior non-planar or multi- surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at the interior at least partly within the portion. In an embodiment, the exterior non-planar or multisurface wall is an exterior multi-surface wall that comprises two substantially planar sub-walls that meet to form a line. In an embodiment, the superconductive coils are configured to generate, during use, a 2D spatially alternating magnetic field. In an embodiment, at least one module has an electrical interface to provide electricity to the subset of one or more coils and / or a cooling interface to provide cooling for the superconductivity of the subset of one or more coils, the electrical and / or cooling interface located at a wall other than the one or more walls arranged to interface with one or more adjacent modules.

[0186] In an embodiment, there is provided a module 88 for a superconductive assembly for an actuator, the module comprising one or more superconductive coils of a plurality of superconductive coils of the assembly, the module having an exterior or multi-surface non-planar wall, such as wall 97, 98. In an embodiment, the exterior non-planar or multi-surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at least partly within the portion at the interior. In an embodiment, the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises two substantially planar sub-walls that meet to form a line. In an embodiment, the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises a sawtooth-type configuration. In an embodiment, a cross-section of the module in a plane parallel to a layout of the plurality of superconductive coils is non-rectangular.

[0187] In an embodiment, since the shuttle 84 follows the movement of the stage 29 in at least one direction, the acceleration and velocity of the shuttle 84 should be the same as, or quite close to the same as, the acceleration and velocity of the stage 29 in that at least one direction. So, there is desired an actuator for the shuttle 29 that is capable of providing increased acceleration and / or velocity compared to a conventional linear motor but that can fit within the tight volume and physical constraints of the actuator system 1 as described herein. For example, a significant increase in size of the actuator structure 86 of the shuttle 84 to provide support for increased acceleration and / or velocity of the stage 29 would imply an undesired increase of, e.g., the thermal conditioning plate 25 volume requirement. So, in an embodiment, there is provided a superconductive actuator for the shuttle 84 that can fit within the tight volume and physical constraints of the actuator system 1.

[0188] Referring to Figure 16, an actuator system 1 comparable to that depicted, and described with respect to, Figure 13a is shown. For the sake of brevity only, the differences from the Figure 13a embodiment are described. In particular, in Figure 16, a superconductive actuator is provided that enables movement of a body other than the stage 29. In the embodiment of Figure 16, the body other than the stage 29 is the shuttle 84. In an embodiment, the body other than the stage 29 can be thermalconditioning plate 25 (and optionally vessel 28 and / or thermal shield 30). In that case, the movement might be to “re-center” thermal conditioning plate 25 (and optionally vessel 28 and / or thermal shield 30) where it acts a balance mass. For example, a balance mass might not return to an original position and / or orientation after absorbing various reaction forces arising during the movement of the stage 29. That is, the balance mass might become displaced to a location in the X, Y or Z direction other than where expected due to the reaction forces or oriented (rotated) around the X, Y or Z direction (e.g., drift from an expected position). So, the balance mass might need to be moved back to, or close to, a central or original position and / or orientation (e.g., correct the drift). The superconductor actuator can be used to implement that. In an embodiment, the body other than the stage 29 can be a body to counteract a torque exerted on thermal conditioning plate 25 (and optionally vessel 28 and / or thermal shield 30) arising from the movements of the stage 29. That is, a body to create a torque in an opposite, and preferably equal, manner as a torque exerted on the thermal conditioning plate 25, which torque can be applied dynamically as different torques are exerted on the thermal conditioning plate 25.

[0189] In an embodiment, a component of the superconductive actuator for the body other than the stage 29 can be arranged in the same cryostat arrangement in which the coil array 2 for the stage 29 is located. Referring to Figure 16, one or more superconductive coils 90 (desirably a plurality of superconductive coils 90 arranged, for example, in an array) configured to cooperate with a separate body from the stage 29 are provided. Further, the coil layer 2 and the one or more superconductive coils 90 have a common cooling arrangement to provide cooling for the superconductivity, namely at least thermal conditioning plate 25. In an embodiment, the one or more superconductive coils form a superconductive magnet assembly. So, in an embodiment, the one or more superconductive coils 90 are arranged in the same cryostat arrangement as used to harbor the coil array 2 for stage 29. So, the cryogenic refrigeration of, for example, up to 20K that is already present in, e.g., Figure 13a for superconductive actuation of the stage 29 is used. Therefore, no additional volume may be needed for cryogenic cooling of the actuator for the body other than the stage 29.

[0190] In an embodiment, the one or more superconductive coils 90 are used in conjunction with shuttle 84 (a second mover where the stage 29 is a first mover). Accordingly, in an embodiment, the shuttle 84 has an actuator component to cooperate with the one or more superconductive coils 90 to enable the displacement of the shuttle 84. For example, where the one or more superconductive coils 90 form a magnet assembly, the shuttle 84 can comprise one or more coils that are provided electrical current to enable displacement of the shuttle 84 when the one or more coils interact with the magnetic field of the one or more superconductive coils 90 in the form of a magnet assembly. Of course, this arrangement can be reversed where the magnet assembly is on the shuttle 84.

[0191] In an embodiment, the one or more superconductive coils 90 are located at an opposite position of the thermal conditioning plate 25 to the coil array 2 as shown in Figure 16. However, the one or more superconductive coils 90 do not need to be located there. The one or more superconductive coils 90 could be located, for example, a side of the thermal conditioning plate 25. Or, for example, theone or more superconductive coils 90 could be located at a central location of the thermal conditioning plate 2 depending on the application of the one or more superconductive coils 90 (e.g., to be used to re- center a balance mass as described above).

[0192] In an embodiment, the one or more superconductive coils 90 can configured in a structural arrangement as shown in Figures 14 and 15. For example, the one or more superconductive coils 90 can be divided into modules similar to those for coils 2. In an embodiment, the modules for the one or more superconductive coils 90 can be combined with the modules for the coils 2. In an embodiment, the modules for the one or more superconductive coils 90 can integrated into one (or more than one) module for the coils 2. Of course, if the one or more superconductive coils 90 are not segmented into modules, those one or more superconductive coils 90 may be located in one or more structures of modules for coils 2.

[0193] Further, Figure 16 shows one or more superconductive coils 90 located at the left side and one or more superconductive coils 90 located at the right side. In the embodiment of Figure 16, the one or more superconductive coils 90 located at the left are configured to enable movement of shuttle 84. In an embodiment, the one or more superconductive coils 90 located at the right can be used with another shuttle (not shown) of the same or similar construction as shuttle 84. That other shuttle (not shown) can be used with another stage (not shown) of the same or similar construction as stage 29 (or a stage having a utility support as described herein) and thus have a dual stage configuration. In an embodiment, the one or more superconductive coils 90 located at the right could be used to re-center a balance mass as described above (e.g., by having a cooperating coil in a body relative to which the balance mass can move, such as in the frame 15, in the vessel 28 if the thermal conditioning plate 25 can move relative to the vessel 28, or in the thermal shield 30 if the thermal conditioning plate 25 can move relative to the vessel 28).

[0194] In an embodiment, the one or more superconductive coils 90 are energized with a large amount of electric current, e.g., 1 kA to 5 kA, or at least 2 kA. Accordingly, one or more current leads as shown from the supply line 63 are provided to enable the current supply to the one or more superconductive coils 90.

[0195] In an embodiment, a guide beam structure can be provided comparable to the guide beam structure of actuator structure 86. For example, the guide beam structure can be located between the one or more superconductive coils 90 and shuttle 84. Like the guide beam for actuator structure 86, the guide beam structure in association with the one or more superconductive coils 90 would provide, for example, a crash interface in case shuttle 84 become uncontrolled. It would, for example, have no physical contact with the shuttle 84 during relative movement between the shuttle 84 and the guide beam structure but then creates physical contact with the shuttle 84 when it is movement becomes uncontrolled or otherwise out of specification so as to limit the range of movement of the shuttle 84. In an embodiment, due to the use of the one or more superconductive coils 90, a guide beam as provided with actuator structure 86 may not be needed. Therefore, the volume needed for the one or moresuperconductive coils 90 coils in the Z direction may not require additional volume in the Z direction since the guide beam volume occupied can be used.

[0196] So, by introduction of the one or more superconductive coils 90, a benefit, such as minimal thermal dissipation, may be achieved to move a body other than the stage 29 compared to a conventional solution since the acceleration of the other body can be achieved by, for example, increasing the magnetic field density compared to increasing current in a conventional solution.

[0197] In accordance with an embodiment, ‘cryogenic cooling’ or ‘cooling the coil layer to a cryogenic temperature’ refers to a process of cooling the coil layer to such a temperature that the coils exhibit a superconductive behavior and keeping the coils at such a temperature. As such, when cooled to such a temperature, the coils may be supplied with an electrical current, substantially without generating Ohmic losses. As will be appreciated by the skilled person, the required temperature or cooling may depend on the material or composition of the applied coils and / or the pressure conditions prevailing. Accordingly, a “cryostat” or “cryostat environment” refers to a device used to maintain low cryogenic temperatures of one or more components (e.g., one or more coils) within the cryostat. So, for example, “cryostat” or “cryostat environment” can be an insulated environment that is cooled by cryogenic cooling, e.g., a vacuum insulated environment.

[0198] In accordance with an embodiment, a positioner or actuator refers to a device that moves and / or levitates an object. A positioner or actuator can be a linear positioner or actuator that moves an object primarily in a particular one direction. A positioner or actuator can be a planar positioner or actuator that moves an object primarily in two or more directions, e.g., in a plane defined by the two or more directions. In an embodiment, a positioner or actuator comprises a combination of two or more linear actuators or positioners, e.g., a short stroke and long stroke arrangement. In an embodiment, a positioner or actuator comprises a combination of one or more planar motors and one or more linear actuators or positioners, e.g., a short stroke and long stroke arrangement. In an embodiment, a positioner or actuator comprises a combination of two or more planar actuators or positioners, e.g., a short stroke and long stroke arrangement.,

[0199] In an embodiment, the positioner or actuator system is provided with a module, assembly, magnet body, etc. as described herein. Thus, the positioner or actuator system can be a cryogenic positioner or actuator.

[0200] In an embodiment, the coil layer may be wired for alternating current operation. In an embodiment, the coil layer may be wired for direct current operation (e.g., as an array of electromagnets).

[0201] In an embodiment, there is provided a materials processing or metrology apparatus comprising a module, assembly, magnet body, a positioner or actuator, etc. as described herein. The material processing apparatus can be, for example, a lithographic apparatus, an etching tool, a resist application tool, a polishing apparatus, etc. The metrology apparatus can be, for example, an electron beam based measurement tool (such as a scanning electron microscope), an electromagnetic radiation based optical or scatterometry measurement tool, an alignment measurement tool, an overlay measurement tool, etc.

[0202] In an embodiment, there is provided a lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises a module, assembly, magnet body, a positioner or actuator, etc. as described herein.

[0203] Embodiments herein have focused on the positioner PW. However, all the concepts herein can be applied to other supports and positioners. For example, all the concepts herein could be applied to positioner PM, e.g., it could have its own balance mass, its own position measurement system (e.g., comparable to measurement system PMS), etc.

[0204] Each of the embodiments may be combined with one or more of the other embodiments as appropriate. Moreover, one or more aspects of one embodiment may be combined with one or more aspects of another embodiment.

[0205] Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquidcrystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion,” respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and / or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains one or multiple processed layers.

[0206] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in another apparatus or different applications. Embodiments may be part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or inspects an object (such as a wafer (or other substrate) or mask (or other patterning device)). Embodiments may be part of an etching apparatus, a resist application apparatus, a resist development apparatus, a substrate polishing apparatus (e.g., a CMP apparatus) or other apparatus that performs materials processing of an object. More generally, embodiments may be part of an apparatus that moves an object. These various apparatuses may be generally referred to as object processing tools. Such an object processing tool may use vacuum conditions or ambient (nonvacuum) conditions.

[0207] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that an embodiment of the invention, where the context allows, is not limited to optical lithography and may be used in other applications, for example imprint lithography (and hence in an imprint apparatus).

[0208] Where the context allows, 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. A machine -readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine -readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions.

[0209] However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.

[0210] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below. Other aspects of the invention are set-out as in the following numbered clauses.1. A lithographic apparatus assembly comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils are grouped in a plurality of separable and discrete modules which, when assembled, form the assembly, each module comprising a subset of one or more coils of the plurality of coils and comprising an electrical interface to provide electricity to the subset of one or more coils.2. A superconductive assembly for an actuator, the assembly comprising, during use, a pluralityof superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils are grouped in a plurality of separable and discrete modules which, when assembled, form the assembly, each module comprising a subset of one or more coils of the plurality of coils and comprising an electrical interface to provide electricity to the subset of one or more coils.3. The assembly of clause 1 or clause 2, wherein each module comprises a cooling interface to provide cooling for the superconductivity of the subset of one or more coils.4. The assembly of any of clauses 1-3, wherein at one least module has an exterior non-planar or multi-surface wall.5. The assembly of clause 4, wherein adjacent modules of the modules each have the exterior non-planar or multi-surface wall and the exterior non-planar or multi-surface walls are designed so as to interlock with each other.6. The assembly of clause 4 or clause 5, wherein the exterior non-planar or multi-surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at the interior at least partly within the portion.7. The assembly of any of clauses 4-6, wherein the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises two substantially planar sub-walls that meet to form a line.8. The assembly of any of clauses 1-7, wherein the superconductive coils are configured to generate, during use, a 2D spatially alternating magnetic field.9. The assembly of any of clauses 1-8, wherein the electrical interface is located at a wall other than the one or more walls arranged to interface with one or more adjacent modules.10. The assembly of any of clauses 1-9, wherein the plurality of superconductive coils are configured to cooperate with a mover of the actuator, and further comprising one or more further superconductive coils configured to cooperate with a separate body from the mover, the plurality of superconductive coils and the one or more further superconductive coils having a common cooling arrangement to provide cooling for the superconductivity.11. A materials processing or metrology apparatus comprising the assembly of any of clauses 2- 10.12. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the assembly of any of clauses 2-10.13. A magnet body for a planar motor, the magnet body comprising, during use, a plurality of superconductive coils that are configured to, during use, generate a 2D spatially alternating magnetic field, wherein the plurality of superconductive coils are grouped in a set of separable and discrete modules which, when assembled, form the magnet body, each module comprising a subset of the plurality of coils.14. The magnet body of clause 13, wherein at one least module has an exterior non-planar or multi-surface wall.15. The magnet body of clause 14, wherein adjacent modules of the modules each have the exterior non-planar or multi-surface wall and the exterior non-planar or multi-surface walls are designed so as to interlock with each other.16. The magnet body of clause 14 or clause 15, wherein the exterior non-planar or multi-surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at the interior at least partly within the portion.17. The magnet body of any of clauses 14-16, wherein the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises two substantially planar sub-walls that meet to form a line.18. The magnet body of any of clauses 13-17, wherein the superconductive coils are configured to generate, during use, a 2D spatially alternating magnetic field.19. The magnet body of any of clauses 13-18, wherein at least one module has an electrical interface to provide electricity to the subset of one or more coils and / or a cooling interface to provide cooling for the superconductivity of the subset of one or more coils, the electrical and / or cooling interface located at a wall other than the one or more walls arranged to interface with one or more adjacent modules.20. A materials processing or metrology apparatus comprising the magnet body of any of clauses 13-19.21. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the magnet body of any of clauses 13-19.22. A module for a superconductive assembly for an actuator, the module comprising one or more superconductive coils of a plurality of superconductive coils of the assembly, the module having an exterior or multi-surface non-planar wall.23. The module of clause 22, wherein the exterior non-planar or multi-surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at least partly within the portion at the interior.24. The module of clause 22 or clause 23, wherein the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises two substantially planar sub-walls that meet to form a line.25. The module of any of clauses 22-24, wherein the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises a sawtooth-type configuration.26. The module of any of clauses 22-25, wherein a cross-section of the module in a plane parallel to a layout of the plurality of superconductive coils is non-rectangular.27. A materials processing or metrology apparatus comprising the module of any of clauses 22- 26.28. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the module of any of clauses 22-26.29. A lithographic apparatus assembly comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises a superconductive coil array configured to cooperate with a mover, and one or more superconductive coils configured to cooperate with a separate body from the mover, the superconductive coil array and the one or more superconductive coils having a common cooling arrangement to provide cooling for the superconductivity.30. A superconductive assembly for an actuator, the assembly comprising a superconductive coil array configured to cooperate with a mover of the actuator, and one or more superconductive coils configured to cooperate with a separate body from the mover, the superconductive coil array and the one or more superconductive coils having a common cooling arrangement to provide cooling for thesuperconductivity .31. The assembly of clause 29 or clause 30, wherein the common cooling arrangement is arranged to provide a common cryostat environment of the superconductive coil array and the one or more superconductive coils.32. The assembly of any of clauses 29-31, wherein the separate body comprises a second mover and the one or more superconductive coils form a superconductive magnet array configured to cooperate with the second mover.33. The assembly of clause 32, wherein the second mover forms part of a drive system configured to displace one or more current carrying cables of the first mover.34. The assembly of clause 30 or clause 31, wherein the separate body cooperates with the one or more superconductive coils to apply a force and / or torque to the assembly.35. The assembly of any of clauses 30-34, wherein the actuator is a moving coil planar actuator and the superconductive coil array is configured to generate a 2D spatially alternating magnetic field.36. The assembly of any of clauses 30-35, wherein the superconductive coil array comprises, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils of the superconductive coil array are grouped in a plurality of separable and discrete modules which, when assembled, form the superconductive coil array, each module comprising a subset of one or more coils of the plurality of coils of the superconductive coil array.37. The assembly of any of clauses 30-36, wherein at one least module has an exterior non-planar or multi-surface wall.38. A materials processing or metrology apparatus comprising the assembly of any of clauses 30- 37.39. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the assembly of any of clauses 30-37.40. A superconductive assembly for an actuator, the assembly comprising: a vessel, and a superconductive coil array configured to cooperate with a mover of the actuator, the superconductive coil array being arranged inside the vessel; a power supply for powering one or more coils of the superconductive coil array;wherein the superconductive assembly is configured to, during use, act as a balance mass, and wherein the power supply is mounted to the vessel of the superconductive assembly.41. The superconductive assembly according to clause 40, wherein the superconductive coils are configured to generate, during use, a 2D spatially alternating magnetic field.42. The superconductive assembly according to clause 40 or 41, wherein the superconductive coil array is mounted to a thermal conductive plate of the assembly.43. The superconductive assembly according to any of the clauses 40-42, wherein the vessel comprises a thermal shield.44. The superconductive assembly according to any of the clauses 40-43, wherein the power supply comprises an input terminal configured to receive power leads from a mains power supply.45. The superconductive assembly according to any of the clauses 40-44, wherein the power supply comprises an output terminal configured to receive power leads for powering the one or more coils of the superconductive coil array.46. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the assembly of any of clauses 40-45.47. A materials processing or metrology apparatus comprising the superconductive assembly of any of clauses 40 - 45.

Claims

CLAIMS1. A lithographic apparatus assembly comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils are grouped in a plurality of separable and discrete modules which, when assembled, form the assembly, each module comprising a subset of one or more coils of the plurality of coils and comprising an electrical interface to provide electricity to the subset of one or more coils.

2. A superconductive assembly for an actuator, the assembly comprising, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils are grouped in a plurality of separable and discrete modules which, when assembled, form the assembly, each module comprising a subset of one or more coils of the plurality of coils and comprising an electrical interface to provide electricity to the subset of one or more coils.

3. The assembly of claim 1 or claim 2, wherein each module comprises a cooling interface to provide cooling for the superconductivity of the subset of one or more coils.

4. The assembly of any of claims 1-3, wherein at one least module has an exterior non-planar or multi-surface wall.

5. The assembly of claim 4, wherein adjacent modules of the modules each have the exterior non-planar or multi-surface wall and the exterior non-planar or multi-surface walls are designed so as to interlock with each other.

6. The assembly of claim 4 or claim 5, wherein the exterior non-planar or multi-surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at the interior at least partly within the portion.

7. The assembly of any of claims 4-6, wherein the exterior non-planar or multi-surface wall is anexterior multi-surface wall that comprises two substantially planar sub- walls that meet to form a line.

8. The assembly of any of claims 1-7, wherein the superconductive coils are configured to generate, during use, a 2D spatially alternating magnetic field.

9. The assembly of any of claims 1-8, wherein the electrical interface is located at a wall other than the one or more walls arranged to interface with one or more adjacent modules.

10. The assembly of any of claims 1-9, wherein the plurality of superconductive coils are configured to cooperate with a mover of the actuator, and further comprising one or more further superconductive coils configured to cooperate with a separate body from the mover, the plurality of superconductive coils and the one or more further superconductive coils having a common cooling arrangement to provide cooling for the superconductivity.

11. A materials processing or metrology apparatus comprising the assembly of any of claims 2- 10.

12. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the assembly of any of claims 2-10.

13. A magnet body for a planar motor, the magnet body comprising, during use, a plurality of superconductive coils that are configured to, during use, generate a 2D spatially alternating magnetic field, wherein the plurality of superconductive coils are grouped in a set of separable and discrete modules which, when assembled, form the magnet body, each module comprising a subset of the plurality of coils.

14. The magnet body of claim 13, wherein at one least module has an exterior non-planar or multi-surface wall.

15. The magnet body of claim 14, wherein adjacent modules of the modules each have theexterior non-planar or multi-surface wall and the exterior non-planar or multi-surface walls are designed so as to interlock with each other.

16. The magnet body of claim 14 or claim 15, wherein the exterior non-planar or multi-surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at the interior at least partly within the portion.

17. The magnet body of any of claims 14-16, wherein the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises two substantially planar sub-walls that meet to form a line.

18. The magnet body of any of claims 13-17, wherein the superconductive coils are configured to generate, during use, a 2D spatially alternating magnetic field.

19. The magnet body of any of claims 13-18, wherein at least one module has an electrical interface to provide electricity to the subset of one or more coils and / or a cooling interface to provide cooling for the superconductivity of the subset of one or more coils, the electrical and / or cooling interface located at a wall other than the one or more walls arranged to interface with one or more adjacent modules.

20. A materials processing or metrology apparatus comprising the magnet body of any of claims 13-19.

21. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the magnet body of any of claims 13-19.

22. A module for a superconductive assembly for an actuator, the module comprising one or more superconductive coils of a plurality of superconductive coils of the assembly, the module having an exterior or multi-surface non-planar wall.

23. The module of claim 22, wherein the exterior non-planar or multi-surface wall has a portion thereof that protrudes at the exterior from the module and at least one coil is arranged to extend at least partly within the portion at the interior.

24. The module of claim 22 or claim 23, wherein the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises two substantially planar sub-walls that meet to form a line.

25. The module of any of claims 22-24, wherein the exterior non-planar or multi-surface wall is an exterior multi-surface wall that comprises a sawtooth-type configuration.

26. The module of any of claims 22-25, wherein a cross-section of the module in a plane parallel to a layout of the plurality of superconductive coils is non-rectangular.

27. A materials processing or metrology apparatus comprising the module of any of claims 22-26.

28. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the module of any of claims 22-26.

29. A lithographic apparatus assembly comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises a superconductive coil array configured to cooperate with a mover, and one or more superconductive coils configured to cooperate with a separate body from the mover, the superconductive coil array and the one or more superconductivecoils having a common cooling arrangement to provide cooling for the superconductivity.

30. A superconductive assembly for an actuator, the assembly comprising a superconductive coil array configured to cooperate with a mover of the actuator, and one or more superconductive coils configured to cooperate with a separate body from the mover, the superconductive coil array and the one or more superconductive coils having a common cooling arrangement to provide cooling for the superconductivity .

31. The assembly of claim 29 or claim 30, wherein the common cooling arrangement is arranged to provide a common cryostat environment of the superconductive coil array and the one or more superconductive coils.

32. The assembly of any of claims 29-31, wherein the separate body comprises a second mover and the one or more superconductive coils form a superconductive magnet array configured to cooperate with the second mover.

33. The assembly of claim 32, wherein the second mover forms part of a drive system configured to displace one or more current carrying cables of the first mover.

34. The assembly of claim 30 or claim 31, wherein the separate body cooperates with the one or more superconductive coils to apply a force and / or torque to the assembly.

35. The assembly of any of claims 30-34, wherein the actuator is a moving coil planar actuator and the superconductive coil array is configured to generate a 2D spatially alternating magnetic field.

36. The assembly of any of claims 30-35, wherein the superconductive coil array comprises, during use, a plurality of superconductive coils that are configured to generate a magnetic field, wherein the plurality of superconductive coils of the superconductive coil array are grouped in a plurality of separable and discrete modules which, when assembled, form the superconductive coil array, each module comprising a subset of one or more coils of the plurality of coils of the superconductive coil array.

37. The assembly of any of claims 30-36, wherein at one least module has an exterior non-planar or multi-surface wall.

38. A materials processing or metrology apparatus comprising the assembly of any of claims 30- 37.

39. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device; a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the assembly of any of claims 30-37.

40. A superconductive assembly for an actuator, the assembly comprising: a vessel, and a superconductive coil array configured to cooperate with a mover of the actuator, the superconductive coil array being arranged inside the vessel; a power supply for powering one or more coils of the superconductive coil array; wherein the superconductive assembly is configured to, during use, act as a balance mass, and wherein the power supply is mounted to the vessel of the superconductive assembly.

41. The superconductive assembly according to claim 40, wherein the superconductive coils are configured to generate, during use, a 2D spatially alternating magnetic field.

42. The superconductive assembly according to claim 40 or 41, wherein the superconductive coil array is mounted to a thermal conductive plate of the assembly.

43. The superconductive assembly according to any of the claims 40-42, wherein the vessel comprises a thermal shield.

44. The superconductive assembly according to any of the claims 40-43, wherein the power supply comprises an input terminal configured to receive power leads from a mains power supply.

45. The superconductive assembly according to any of the claims 40-44, wherein the power supply comprises an output terminal configured to receive power leads for powering the one or more coils of the superconductive coil array.

46. A lithographic apparatus comprising: a patterning device support constructed to support a patterning device;a first positioner configured to position the patterning device support; a substrate support constructed to hold a substrate; a second positioner configured to position the substrate support; and a projection system configured to project a radiation beam from the patterning device onto the substrate, wherein one or more selected from: the patterning device support, the first positioner, the substrate support, and / or the second positioner comprises the assembly of any of claims 40-45.

47. A materials processing or metrology apparatus comprising the superconductive assembly of any of claims 40 - 45.

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