Electromagnetic coil

Abstract

The present invention relates to an electromagnetic coil comprising an electrically conductive wire wound with N number of windings about a central axis, wherein N is an integer and at least 3, the wire having a rectangular cross-section with a first width measured along the central axis from a left side surface to a right side surface, and a first thickness measured perpendicular to the first width from an upper surface to a lower surface, wherein, when seen in a cross-sectional plane extending parallel to the central axis, at least one channel is formed between the upper surface of an inner winding of the electrically conductive wire, at least one of the left side surface and right side surface of a first outer winding located on top of the inner winding, and the lower surface of a second outer winding located on top of the first outer winding.

Description

ELECTROMAGNETIC COILCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 24191005.8 which was filed on 25 July 2024 and which is incorporated herein in its entirety by reference.FIELD

[0002] The present invention relates to an electromagnetic coil and to a coil assembly. The present invention further relates to an actuator and an apparatus comprising the electromagnetic coil or coil assembly. The present invention yet further relates to an electromagnetic coil manufacturing system and a method for manufacturing an electromagnetic coil.BACKGROUND

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004] In a lithographic apparatus, but also in other apparatus, one or more actuators are used. An actuator may comprise one or more electromagnetic coils. For example linear actuators, typically Lorentz actuators, comprise a coil assembly with flat wire copper coils. A flat wire copper coil is an electromagnetic coil and is often manufactured by winding a single copper wire on and around a core with multiple windings, or turns. Generally copper wire coils are made with the intention to maximize the copper density or achieving high tolerance. A disadvantage of these high density copper wire coils is a limited power capability.SUMMARY

[0005] It is desirable to provide an electromagnetic coil or coil assembly with improved powercapabilities.

[0006] It is further desirable to provide an improved electromagnetic coil or coil assembly that is easier to manufacture.

[0007] In order to achieve at least one object, the invention provides in a first aspect an electromagnetic coil comprising- an electrically conductive wire wound with N number of windings about a central axis, wherein N is an integer and at least 3, the wire having a rectangular crosssection with a first width measured along the central axis from a left side surface to a right side surface, and a first thickness measured perpendicular to the first width from an upper surface to a lower surface, wherein, when seen in a cross-sectional plane extending parallel to the central axis, at least one channel is formed between o the upper surface of an inner winding of the electrically conductive wire, o at least one of the left side surface and right side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding.

[0008] In an embodiment of the electromagnetic coil, the electrically conductive wire comprises a first wire part and a second wire part that are connected to each other at a respective first wire part first end and a second wire part first end to form an electrically conductive connection, wherein the first wire part and second wire part are wound around each other, thereby forming an alternating pattern when seen in cross-section.

[0009] In an embodiment of the electromagnetic coil, the first wire part has the first width and the first thickness, and wherein the second wire part has a second width and a second thickness, when seen in cross-section, wherein the first width and second width are different and / or wherein the first thickness and second thickness are different.

[0010] In an embodiment of the electromagnetic coil, the electrically conductive connection is located in an inner space enclosed by the innermost winding.

[0011] In an embodiment of the electromagnetic coil, the at least one channel is formed between o the upper surface of an inner winding of the wire, o the left side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding, and wherein at least one opposite channel is formed between o the upper surface of an inner winding of the wire, o the right side surface of a first outer winding located on top of the innerwinding, and o the lower surface of a second outer winding located on top of the first outer winding.

[0012] In an embodiment of the electromagnetic coil, wherein the at least one channel has a U-shape with right-angled comers.

[0013] In an embodiment the electromagnetic coil comprises a cover member for closing off the at least one channel.

[0014] In an embodiment of the electromagnetic coil, the second wire part comprises two parallel wires that are located at a distance from each other along the central axis, wherein the at least one channel is formed between o the upper surface of an inner winding of the first wire part, o an inner left side surface of one of the two parallel wires and an inner right side surface of the other of the two parallel wires of a first outer winding of the second wire part located on top of the inner winding of the first wire part, and o the lower surface of a second outer winding of the first wire part located on top of the first outer winding of the second wire part,

[0015] In an embodiment of the electromagnetic coil, the first wire part has a first length and the second wire part has a second length, wherein the electrically conductive wire has a total wire length substantially equal to the sum of the first length and second length, wherein the at least one channel winds around the central axis and has a channel length that is substantially equal to the shorter of the first length and second length.

[0016] In a second aspect the invention provides a coil assembly comprising at least two electromagnetic coils according to the first aspect of the invention, wherein the at least two electromagnetic coils are placed adjacent to each other with coinciding central axes, wherein an electrically conductive connection located in an inner space enclosed by the innermost winding of an electromagnetic coil is connected to an electrically conductive connection located in an inner space enclosed by the innermost winding of an adjacent electromagnetic coil.

[0017] In an embodiment of the coil assembly, an open side of the at least one channel of one of the electromagnetic coils is closed off by one or more adjacent windings of the adjacent electromagnetic coil.

[0018] In an embodiment of the coil assembly, an open side of a channel not closed off by an adjacent electromagnetic coil is closed off by a cover member.

[0019] In a third aspect the invention provides an actuator comprising an electromagnetic coil according to the first aspect of the invention or a coil assembly according to the second aspect of the invention.

[0020] The invention further provides a use of an actuator according to the third aspect, wherein a coolant fluid is led through the at least one channel for cooling at least one electromagnetic coil.

[0021] In a fourth aspect the invention provides an apparatus comprising an electromagnetic coil according to the first aspect of the invention or a coil assembly according to the second aspect of the invention.

[0022] In an embodiment the apparatus is a lithographic apparatus.

[0023] In a fifth aspect the invention provides an electromagnetic coil manufacturing system,- a winding core device comprising a winding core, the winding core being configured to receive an electrically conductive wire, the winding core having a core axis,- a first wire part supply device for supplying an electrically conductive first wire part to the winding core,- a second wire part supply device for supplying an electrically conductive second wire part to the winding core,- a driving device for rotating the winding core about its core axis and / or for orbiting the first wire part supply device and second wire part supply device around the winding core, wherein the winding core is configured to rotate about its core axis for winding the electrically conductive wire on and around the winding core and / or wherein the first wire part supply device and second wire part supply device are configured to orbit around the core for winding the electrically conductive wire around the winding core, wherein the winding core device comprises a first guiding unit for guiding the electrically conductive wire around the winding core during winding thereof, the first wire part supply device, second wire part supply device and first guiding unit being configured to wind the electrically conductive wire on the winding core in order to form at least one channel between o an upper surface of an inner winding of the electrically conductive wire, o at least one of the left side surface and right side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding.

[0024] In an embodiment of the electromagnetic coil manufacturing system, the winding core device comprises a second guiding unit, wherein the first guiding unit is configured to guide the first wire part around the winding core during winding thereof, and wherein the second guiding unit is configured to guide the second wire part around the winding core during winding thereof.

[0025] In an embodiment of the electromagnetic coil manufacturing system, the first guiding unit comprises a first planar abutment surface for abutting a left side surface of the first wire part, wherein the second guiding unit comprises a second planar abutment surface for abutting a right side surface of the second wire part, wherein the first planar abutment surface and the second planar abutment surface extend parallel to each other, perpendicular to the core axis and around the core axis.

[0026] In an embodiment of the electromagnetic coil manufacturing system, the winding core device comprises an adjusting member for adjusting a distance along the core axis between the first planarabutment surface and the second planar abutment surface.

[0027] In an embodiment of the electromagnetic coil manufacturing system, the second wire part supply device comprises a first supply unit and a second supply unit, the second wire part supply device being configured to supply two parallel wires that are located at a distance from each other along the core axis to the winding core, wherein the first supply unit is configured to supply one of the parallel wires to the winding core, and wherein the second supply unit is configured to supply the other of the parallel wires to the winding core.

[0028] The invention further provides a method for manufacturing an electromagnetic coil according to the first aspect of the invention, the method comprising the steps: a. providing an electromagnetic coil manufacturing system according to the fifth aspect of the invention, b. supplying a first wire part and a second wire part to the winding core while winding the first wire part and second wire part on and around the winding core and around each other a plurality of times, wherein by winding at least one channel is formed between o an upper surface of an inner winding of the first wire part or second wire part, o at least one of a left side surface and a right side surface of a first outer winding located on top of the inner winding, and o a lower surface of a second outer winding located on top of the first outer winding.

[0029] In an embodiment the method comprises winding the first wire part and second wire part at an offset relative to each other with respect to the core axis, thereby forming a channel on a left side and an opposite channel on a right side of the electromagnetic coil.

[0030] In an embodiment of the method, the first wire part and second wire part have the same first thickness and first width.

[0031] In an embodiment of the method, the first wire part has a first width and a first thickness, and wherein the second wire part has a second width and a second thickness, when seen in cross-section, wherein the first width and second width are different and / or wherein the first thickness and second thickness are different, wherein the method comprises connecting a respective first wire part first end of the first wire part and a second wire part first end of the second wire part to form an electrically conductive connection.BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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:Figure 1 depicts a lithographic apparatus according to an embodiment of the invention;Figures 2 to 5 schematically show different views of an embodiment of an electromagnetic coil according to a first aspect of the invention.Figure 6 schematically shows a cross-sectional front view of the embodiment shown in figure 2.Figure 7 schematically shows a cross-sectional front view of the coil shown in figure 6, further comprising a cover member.Figure 8 schematically shows another embodiment of an electromagnetic coil according to the first aspect of the invention.Figure 9 schematically shows a cross-sectional front view of yet another embodiment of an electromagnetic coil according to the first aspect of the invention.Figures 10 to 13 schematically show different views of an embodiment of a coil assembly according to a second aspect of the invention.Figure 14 schematically shows schematically shows a cross-sectional front view of the embodiment shown in figure 10, further comprising a cover member.Figure 15 schematically shows a cross-sectional front view of another embodiment of a coil assembly according to the second aspect of the invention, further comprising a cover member.Figure 16 schematically shows a cross-sectional front view of yet another embodiment of a coil assembly according to the second aspect of the invention, further comprising a cover member.Figure 17 schematically shows an embodiment of an electromagnetic coil manufacturing system according to another aspect of the invention.Figures 18 to 20 schematically show different embodiments of a winding core device comprising a winding core on and around which an electrically conductive wire is wound.Figure 21 schematically shows a top view of an embodiment of another embodiment of an electromagnetic coil manufacturing system according to the invention.Figures 22A-22K schematically show an embodiment of a method for manufacturing an electromagnetic coil according to the invention, in particular using an electromagnetic coil manufacturing system as shown in figure 21.DETAILED DESCRIPTION

[0033] Figure 1 schematically depicts a lithographic apparatus 41 according to one embodiment of the invention. The apparatus includes an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or any other suitable radiation), a mask support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioning device PM configured to accurately position the patterning device in accordance with certain parameters. The apparatus also includes a substrate table (e.g. a wafer table) WT or "substrate support" constructed to hold a substrate (e.g. a resist-coated wafer) W and connected to a secondpositioning device PW configured to accurately position the substrate in accordance with certain parameters. The apparatus further includes a projection system (e.g. a refractive 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. including one or more dies) of the substrate W.

[0034] The lithographic apparatus may be of a type having one (single stage), two (dual stage) or more substrate tables or "substrate supports" (and / or two or more mask tables or "mask supports"). In such “multiple stage” machines the additional tables or supports may be used in parallel, or preparatory steps may be carried out on one or more tables or supports while one or more other tables or supports are being used for exposure.

[0035] The lithographic apparatus may also 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 and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques can be used to increase the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that a liquid is located between the projection system and the substrate during exposure.

[0036] Referring to figure 1, the illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD including, for example, suitable directing mirrors and / or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0037] The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as <j-outcr and o-inncr. respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

[0038] The radiation beam B is incident on the patterning device (e.g., mask MA), which is held on the mask support structure (e.g., mask table MT), and is patterned by the patterning device. Having traversed the mask 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 positioning device PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in thepath of the radiation beam B. Similarly, the first positioning device PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the mask MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the mask table MT may be realized with the aid of a long- stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioning device PM. Similarly, movement of the substrate table WT or "substrate support" may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the mask table MT may be connected to a short-stroke actuator only, or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

[0039] The first positioner PM and the second positioner PW each are provided with an actuator to move respectively the mask support MT and the substrate support WT. The actuator 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 axis. The actuator may be a planar actuator to provide a driving force along multiple axis. For example, the planar actuator may be arranged to move the substrate support WT in 6 degrees of freedom. The actuator may be an electromagnetic actuator comprising at least one coil and at least one magnet. The actuator is arranged to move the at least one coil relative to the at least one magnet by applying an electrical current 65 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 substrate support WT respectively to the mask support MT. The actuator may be a moving-coil type actuator which has the at least one coil coupled to the substrate support WT respectively to the mask support MT. The actuator may be a voice-coil actuator, a reluctance actuator, a Lorentz-actuator or a piezo-actuator, or any other suitable actuator.

[0040] Turning to figures 2 to 9, different embodiments are shown of an electromagnetic coil 1. The electromagnetic coil 1 can be used for one or more of the above described actuators. A plurality of the electromagnetic coils 1 may be provided as a coil assembly 35 for the actuator. Embodiments of a coil assembly 35 will be described later in relation to figures 10 to 16.

[0041] The electromagnetic coil 1 comprises an electrically conductive wire 2 wound with N number of windings 3 (first shown in Figure 6) about a central axis 4 (first shown in Figure 4), wherein N is an integer and at least 3. The wire has a rectangular cross-section with a first width 5 (first shown in Figure 6) measured along the central axis 4 from a left side surface 6 to a right side surface 7, and a first thickness 8 measured perpendicular to the first width 5 from an upper surface 9 to a lower surface 10. The electrically conductive wire 2 is typically a flat copper wire. Other materials are also suitable,e.g. aluminum. The top view of figure 4 schematically shows the direction of current 65 through the coil.

[0042] The terms left, right, upper and lower are used to indicate relative locations or orientations of features. The terms left and right relate to a location along the central axis 4, see for example the left side 70 and left side surface 6 in figure 6, compared to the right side 71 and right side surface 7. The terms upper and lower relate to a relative location perpendicular to the central axis 4, i.e. radially away from the central axis 4. See for example the upper surface 9 and lower surface 10 in figure 6. The first wire part 16 and second wire part 17 have a lower surface 10 that faces the central axis, and an upper surface 9 that faces away from the central axis.

[0043] In the perspective view of figure 2 and the top view of figure 3 the discrete windings are not shown in detail. When seen in a cross-sectional plane extending parallel to the central axis 4, as shown in the cross-sectional view of figure 6 corresponding to section A-A in the perspective view of figure 2, at least one channel 12 is formed between the upper surface 9 of an inner winding 13 of the electrically conductive wire 2, at least one of the left side surface 6 and right side surface 7 of a first outer winding 14 located on top of the inner winding 13, and the lower surface 10 of a second outer winding 15 located on top of the first outer winding 14.

[0044] The terms inner winding 13, first outer winding 14 and second outer winding 15 are chosen in order to indicate a location relative to each other. Referring to figure 6, the inner winding 13 can for example be an innermost winding or an ‘in between’ winding, as long as the first outer winding 14 is located directly on top of or radially outwardly on the inner winding 13, and the second outer winding 15 is located directly on top of or radially outwardly on the first outer winding 14.

[0045] The at least one channel 12 allows for cooling of the electromagnetic coil 1 during operation. A fluid 40, e.g. a liquid such as water, can flow through the at least one channel 12 and provide efficient cooling to the electromagnetic coil 1. The cooling improves the thermal behavior of the electromagnetic coil 1, such that the current through the coil can be increased. Hence, the present invention also relates to the use of the electromagnetic coil 1, wherein a cooling fluid is passed through the at least one channel.

[0046] The at least one channel 12 is formed between adjacent windings. This allows for easy manufacturing, because the channels can be made directly during the winding process of the coil. There is for example no need for machining the channels after the winding process.

[0047] The electrically conductive wire 2 comprises a first wire part 16 and a second wire part 17 that are connected to each other at a respective first wire part first end 18 and a second wire part first end 19 to form an electrically conductive connection 20, as indicated in figures 2, 3 and 22B. The first wire part 16 and second wire part 17 are wound around each other, thereby forming an alternating pattern when seen in cross-section. The first wire part 16 and second wire part 17 may together be a single continuous wire of constant dimensions, but may also be different wires having different dimensions.

[0048] The electrically conductive connection 20 is located in an inner space 23 enclosed by the innermost winding (as shown in e.g. figure 3).

[0049] A first wire part second end 63 and a second wire part second end 64 function as a double outer lead, as can be best seen in the front view of figure 5. The front view of figure 5 is indicated in figure 4 with arrow FV.

[0050] Three examples of the alternating pattern are shown in the cross-sections of figures 6 to 8 at a corresponding section A-A as indicated in figure 2.

[0051] Figures 6 and 7 show an embodiment of the electromagnetic coil 1 wherein the first wire part 16 and second wire part 17 have the same first thickness 8 and first width 5, and wherein on both the left side 70 and the right side 71 a channel 12, 24 is formed by and between windings. One channel 12 is formed between the upper surface 9 of an inner winding 13 of the wire, the left side surface 6 of a first outer winding 14 located on top of the inner winding 13, and the lower surface 10 of a second outer winding 15 located on top of the first outer winding 14. An opposite channel 24 is formed between the upper surface 9 of an inner winding 13 of the wire, the right side surface 7 of a first outer winding 14 located on top of the inner winding 13, and the lower surface 10 of a second outer winding 15 located on top of the first outer winding 14. Here both channels 12, 24 have a U-shape with right-angled comers. Figure 7 shows the electromagnetic coil 1 of figure 6 being provided with a cover member 26. The cover member 26 closes the side of the electromagnetic coil 1, thereby closing the at least one channel 12 such that a closed channel is formed for a fluid 40 to pass through.

[0052] Figure 8 schematically shows an embodiment wherein the first wire part 16 and second wire part 17 have different dimensions. The first wire part 16 has the first width 5 and the first thickness 8. The second wire part 17 has a second width 21 and a second thickness 22, when seen in cross-section. The first width 5 and second width 21 are different and the first thickness 8 and second thickness 22 are different. The channel 12 here also has a U-shape with right-angled comers. One side, here the left side 70, of the electromagnetic coil 1 may be substantially flush, i.e. no channel is provided on that side.

[0053] Figure 9 schematically shows an embodiment wherein the second wire part 17 comprises two parallel wires 27 that are located at a distance 28 from each other along the central axis 4. Here the channel is formed between the upper surface 9 of an inner winding 13 of the first wire part 16, an inner left side surface 29 of one of the two parallel wires 27 and an inner right side surface 30 of the other of the two parallel wires 27 of a first outer winding 14 of the second wire part 17 located on top of the inner winding 13 of the first wire part 16, and the lower surface 10 of a second outer winding 15 of the first wire part 16 located on top of the first outer winding 14 of the second wire part 17. The channel here has a rectangular shape, e.g. a square.

[0054] The first wire part 16 has a first length and the second wire part 17 has a second length. The electrically conductive wire 2 has a total wire length substantially equal to the sum of the first length and second length. The first length and second length may be the same, but may also be different. Theat least one channel 12 winds around the central axis 4 and has a channel length that is substantially equal to the shorter of the first length and second length. The at least one channel 12 in particular extends from the innermost winding to the outermost winding.

[0055] Turning to figures 10 to 16 different embodiments are schematically shown of a coil assembly 35. The coil assembly 35 comprises at least two electromagnetic coils 1, e.g. at least two electromagnetic coils 1 as shown in figures 2 to 9. The at least two electromagnetic coils 1 are placed adjacent to each other with their respective central axis 4 coinciding. They can be connected to each other with an adhesive via their respective coil cores. An electrically conductive connection 20 located in an inner space 23 enclosed by the innermost winding of an electromagnetic coil 1 is connected to an electrically conductive connection 20 located in an inner space 23 enclosed by the innermost winding of an adjacent electromagnetic coil 1. The conductive wires 2, e.g. made of copper, of adjacent coils can be connected by means of soldering, welding or crimping, or by using some kind of electrical connector attached to each copper lead using any of above mentioned method. An advantage of soldering is that the risk of damaging the at least one channel 12 is lower compared to the other connection methods.

[0056] The electrical conductive connection 68 between adjacent coils may be provided in the respective coil cores 69. Also, a fluid connection 67 may be provided in the respective coil cores 69. See figure 10.

[0057] Figure 14 shows an embodiment, wherein an open side 36 of the at least one channel 12 of one of the electromagnetic coils 1 is closed off by one or more adjacent windings of the adjacent electromagnetic coil 1. In the shown embodiments the open side 36 of a channel of one of the electromagnetic coils 1 is in fact closed off by an adjacent channel of the adjacent electromagnetic coil l.The two electromagnetic coils 1 in figure 14 are the same as the coil shown in figure 6.

[0058] An open side 38 of a channel not closed off by an adjacent electromagnetic coil 1 can be closed off by a cover member 26, as shown for example in the embodiment of figure 15. The two electromagnetic coils 1 in figure 15 are the same as the coil shown in figure 8.

[0059] The two electromagnetic coils 1 in figure 16 are the same as the coil shown in figure 9.

[0060] Although not shown in the figures, an actuator can comprise one or more electromagnetic coils 1, e.g. as shown in figures 2 to 9, or one or more coil assemblies, e.g. as shown in figures 10 to 16. During use of the actuator, a coolant fluid 40 is led through the at least one channel 12 for cooling at least one electromagnetic coil 1. This provides an effective way of cooling the electromagnetic coil 1, thereby improving the power properties thereof.

[0061] In figures 14 to 16 flowpaths of a cooling fluid 40 are indicated with arrows. The cooling fluid 40 enters the electromagnetic coil 1, or coil assembly 35 in a central part thereof, in particular in a direction substantially parallel to the central axis 4. The cooling fluid 40 enters a channel in a radial direction, i.e. transverse to the central axis 4, and subsequently passes through that channel towards a channel exit 66. The cooling fluid 40 flows around the central axis 4, guided by the channel thatextends from the innermost winding to the outermost winding. The cooling fluid 40 in a sense also winds around and away from the central axis 4.

[0062] An apparatus 41, e.g. a lithographic apparatus 42 shown in figure 1, may comprise one or more electromagnetic coils 1 according to the invention. The one or more electromagnetic coils 1 can be provided in an actuator, for example as a coil assembly 35.

[0063] Turning to figures 17 and 21, embodiments of an electromagnetic coil manufacturing system 43 are shown schematically. The manufacturing system 43 comprises a winding core device 44 comprising a winding core 45, the winding core 45 having a core axis 46. The winding core 45 is configured to receive an electrically conductive wire 2.

[0064] The manufacturing system 43 comprises a first wire part supply device 47 for supplying an electrically conductive first wire part 16 to the winding core 45, and a second wire part supply device 48 for supplying an electrically conductive second wire part 17 to the winding core 45. The first wire part supply device 47 and second wire part supply device 48 typically comprise a bobbin comprising the respective first wire part 16 and second wire part 17.

[0065] A driving device 49 (not shown for figure 17) is configured for rotating the winding core 45 about its core axis 46 and / or for orbiting the first wire part supply device 47 and second wire part supply device 48 around the winding core 45. Hence, the winding core 45 is configured to rotate about its core axis 46 for winding the electrically conductive wire 2 on and around the winding core 45 and / or the first wire part supply device 47 and second wire part supply device 48 are configured to orbit around the winding core 45 for winding the electrically conductive wire 2 around the winding core 45. Only rotating the winding core 45 about its core axis 46 allows for the use of a simpler manufacturing system 43. Orbiting the wire supply devices about the winding core 45 requires a more complex manufacturing system 43.

[0066] The winding core device 44 comprises a first guiding unit 50 for guiding the electrically conductive wire 2 around the winding core 45 during winding thereof. Exemplary embodiments of the winding core device 44 are shown in figures 18 to 20. Figures 18 and 20 schematically show a winding core device 44 comprising the winding core 45, the first guiding unit 50 and a second guiding unit 51. Here the first guiding unit 50 is a first flange 72 configured to guide the first wire part 16 around the winding core 45 during winding thereof, and the second guiding unit 51 is a second flange 73 configured to guide the second wire part 17 around the winding core 45 during winding thereof. Figure 19 schematically shows a winding core device 44 comprising the winding core 45 and the first guiding unit 50.

[0067] The first wire part supply device 47, second wire part supply device 48 and first guiding unit 50, and if provided the second guiding unit 51, are configured to wind the electrically conductive wire 2 on the winding core 45 in order to form at least one channel 12 between an upper surface 9 of an inner winding 13 of the electrically conductive wire 2, at least one of the left side surface 6 and right side surface 7 of a first outer winding 14 located on top of the inner winding 13, and the lower surface10 of a second outer winding 15 located on top of the first outer winding 14.

[0068] The first guiding unit 50 comprises a first planar abutment surface 52 for abutting a left side surface 6 of the first wire part 16. The second guiding unit 51, if provided, comprises a second planar abutment surface 53 for abutting a right side surface 7 of the second wire part 17. The first planar abutment surface 52 and the second planar abutment surface 53 extend parallel to each other, perpendicular to the core axis 46 and around the core axis 46. The first planar abutment surface 52 and second planar abutment surface 53 are straight.

[0069] The winding core device 44 may comprise an adjusting member (not shown) for adjusting a distance 55 (see Figure 21) along the core axis 46 between the first planar abutment surface 52 and the second planar abutment surface 53.

[0070] The second wire part supply device 48 may comprise a first supply unit and a second supply unit, e.g. a first bobbin 59 and a second bobbin 60. The second wire part supply device 48 being configured to supply two parallel wires 27 that are located at a distance 28 from each other along the core axis 46 to the winding core 45. The first supply unit is configured to supply one of the parallel wires 27 to the winding core 45. The second supply unit is configured to supply the other of the parallel wires 27 to the winding core 45. The two parallel wires 27 supplied by the first supply unit and second supply unit (not shown) are shown in figure 20.

[0071] A method for manufacturing an electromagnetic coil 1 may comprise the steps of providing an electromagnetic coil manufacturing system 43 according to the invention, e.g. as schematically shown in figure 17 or 21. The method further comprises supplying a first wire part 16 and a second wire part 17 to the winding core 45 while winding the first wire part 16 and second wire part 17 on and around the winding core 45 and around each other a plurality of times, see for example figures 22B to 22G. By winding of the first wire part 16 and second wire part 17 at least one channel 12 is formed between an upper surface 9 of an inner winding 13 of the first wire part 16 or second wire part 17, at least one of a left side surface 6 and a right side surface 7 of a first outer winding 14 located on top of the inner winding 13, and a lower surface 10 of a second outer winding 15 located on top of the first outer winding 14.

[0072] Using a winding core device 44 comprising the first guiding unit 50 and second guiding unit 51, e.g. as shown in figure 18, the method comprises winding the first wire part 16 and second wire part 17 at an offset relative to each other with respect to the core axis 46, thereby forming a channel on a left side and an opposite channel 24 on a right side of the electromagnetic coil 1. This way an electromagnetic coil 1 as shown in figure 6 can be manufactured, wherein the first wire part 16 and second wire part 17 may have the same first thickness 8 and first width 5. The method may comprise connecting a respective first wire part first end 18 of the first wire part 16 and a second wire part first end 19 of the second wire part 17 to form an electrically conductive connection 20. Connecting the first wire part 16 to the second wire part 17 may for this embodiment not be necessary in case a single continuous wire is provided. In the latter case the first wire part 16 and second wire part 17 are thesame wire, but provided on separate supply devices, here two bobbins.

[0073] In order to make an embodiment of the electromagnetic coil 1 as shown in figure 8, the first wire part 16 has a first width 5 and a first thickness 8, and the second wire part 17 has a second width 21 and a second thickness 22, when seen in cross-section. The first width 5 and second width 21 are different and / or the first thickness 8 and second thickness 22 can be different. The method comprises connecting a respective first wire part first end 18 of the first wire part 16 and a second wire part first end 19 of the second wire part 17 to form an electrically conductive connection 20.

[0074] After the winding is complete the wound electrically conductive wire 2 is removed from the manufacturing system 43. This can be done by removing the wound electrically conductive wire 2 from the winding core 45. It may also be possible to remove the wound electrically conductive wire 2 together with the winding core 45 from the manufacturing system 43, wherein the winding core 45 forms part of the electromagnetic coil 1.

[0075] Figures 22A-22K schematically show an embodiment of the method for manufacturing an electromagnetic coil 1. Figures 22A-22J show a front view of the manufacturing system 43 of figure 21. Compared to the system shown in figure 17, the figure 21 embodiment comprises a plurality of tensioners 61 configured to control the tension in the respective wire parts 16, 17.

[0076] In figure 22A the first wire part 16 is shown on the first wire part supply device 47 and the second wire part 17 is shown on the second wire part supply device 48. The first wire part first end 18 and second wire part first end 19 are not yet connected to each other. The connection 20 step is shown in figure 22B, wherein the first wire part first end 18 and second wire part first end 19 are connected to each other on the winding core 45 of the winding core device 44.

[0077] Figures 22C to 22F show the winding of the first wire part 16 and second wire part 17 on the winding core 45 by rotating the winding core 45 while supplying the first wire part 16 and second wire part 17 thereto.

[0078] In figure 22G the first wire part 16 is cut off from the first wire part supply device 47. The last section of the first wire part 16 is then wound around the most outer winding and towards an additional tensioner, see figure 22H. In figure 221 a step is shown, wherein current is applied to the coil for heating up the coil via a positively charged clamp 74 and a negatively charged clamp 75. Figure 22 J shows both the first wire part 16 and second wire part 17 being cut off. The manufactured electromagnetic coil 1 can then be removed from the winding core device 44, with or without the winding core 45. Figure 22K shows an embodiment wherein the manufactured electromagnetic coil 1 comprises the winding core 45 as coil core 69.

[0079] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternativeapplications, 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 multiple processed layers.

[0080] 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 other apparatus. Embodiments of the invention may form part of a mask or wafer inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions or ambient (non-vacuum) conditions.

[0081] 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 the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0082] The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5- 20 nm), as well as particle beams, such as ion beams or electron beams.

[0083] The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

[0084] 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 an incoming 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.

[0085] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, theinvention may take the form of a computer program containing one or more sequences of machine- readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein. Other aspects of the invention are set-out as in the following numbered clauses.1. An electromagnetic coil comprising- an electrically conductive wire wound with N number of windings about a central axis, wherein N is an integer and at least 3, the wire having a rectangular crosssection with a first width measured along the central axis from a left side surface to a right side surface, and a first thickness measured perpendicular to the first width from an upper surface to a lower surface, wherein, when seen in a cross-sectional plane extending parallel to the central axis, at least one channel is formed between o the upper surface of an inner winding of the electrically conductive wire, o at least one of the left side surface and right side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding.2. Electromagnetic coil according to clause 1, wherein the electrically conductive wire comprises a first wire part and a second wire part that are connected to each other at a respective first wire part first end and a second wire part first end to form an electrically conductive connection, wherein the first wire part and second wire part are wound around each other, thereby forming an alternating pattern when seen in cross-section.3. Electromagnetic coil according to clause 2, wherein the first wire part has the first width and the first thickness, and wherein the second wire part has a second width and a second thickness, when seen in cross-section, wherein the first width and second width are different and / or wherein the first thickness and second thickness are different.4. Electromagnetic coil according to clause 2 or 3, wherein the electrically conductive connection is located in an inner space enclosed by the innermost winding.5. Electromagnetic coil according to any one of the preceding clauses, wherein the at least one channel is formed between o the upper surface of an inner winding of the wire, o the left side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding, and wherein at least one opposite channel is formed between o the upper surface of an inner winding of the wire,o the right side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding.6. Electromagnetic coil according to any one of the preceding clauses, wherein the at least one channel has a U-shape with right-angled comers.7. Electromagnetic coil according to any one of the preceding clauses, comprising a cover member for closing off the at least one channel.8. Electromagnetic coil according to any one of clauses 2-4, wherein the second wire part comprises two parallel wires that are located at a distance from each other along the central axis, wherein the at least one channel is formed between o the upper surface of an inner winding of the first wire part, o an inner left side surface of one of the two parallel wires and an inner right side surface of the other of the two parallel wires of a first outer winding of the second wire part located on top of the inner winding of the first wire part, and o the lower surface of a second outer winding of the first wire part located on top of the first outer winding of the second wire part,9. Electromagnetic coil according to any one of clauses 2-8, wherein the first wire part has a first length and the second wire part has a second length, wherein the electrically conductive wire has a total wire length substantially equal to the sum of the first length and second length, wherein the at least one channel winds around the central axis and has a channel length that is substantially equal to the shorter of the first length and second length.10. A coil assembly comprising at least two electromagnetic coils according to any one of the preceding clauses, wherein the at least two electromagnetic coils are placed adjacent to each other with coinciding central axes, wherein an electrically conductive connection located in an inner space enclosed by the innermost winding of an electromagnetic coil is connected to an electrically conductive connection located in an inner space enclosed by the innermost winding of an adjacent electromagnetic coil.11. Coil assembly according to clause 10, wherein an open side of the at least one channel of one of the electromagnetic coils is closed off by one or more adjacent windings of the adjacent electromagnetic coil.12. Coil assembly according to clause 10 or 11, wherein an open side of a channel not closed off by an adjacent electromagnetic coil is closed off by a cover member.13. An actuator comprising an electromagnetic coil according to any one of clauses 1-9 or a coil assembly according to any one of clauses 10 - 12.14. Use of an actuator according to the preceding clause, wherein a coolant fluid is led throughthe at least one channel for cooling at least one electromagnetic coil.15. An apparatus comprising an electromagnetic coil according any one of clauses 1 - 9 or a coil assembly according to any one of clauses 10 -12.16. Apparatus according to clause 15, wherein the apparatus is a lithographic apparatus.17. An electromagnetic coil manufacturing system,- a winding core device comprising a winding core, the winding core being configured to receive an electrically conductive wire, the winding core having a core axis,- a first wire part supply device for supplying an electrically conductive first wire part to the winding core,- a second wire part supply device for supplying an electrically conductive second wire part to the winding core,- a driving device for rotating the winding core about its core axis and / or for orbiting the first wire part supply device and second wire part supply device around the winding core, wherein the winding core is configured to rotate about its core axis for winding the electrically conductive wire on and around the winding core and / or wherein the first wire part supply device and second wire part supply device are configured to orbit around the core for winding the electrically conductive wire around the winding core, wherein the winding core device comprises a first guiding unit for guiding the electrically conductive wire around the winding core during winding thereof, the first wire part supply device, second wire part supply device and first guiding unit being configured to wind the electrically conductive wire on the winding core in order to form at least one channel between o an upper surface of an inner winding of the electrically conductive wire, o at least one of the left side surface and right side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding.18. Electromagnetic coil manufacturing system according to the preceding clause, wherein the winding core device comprises a second guiding unit, wherein the first guiding unit is configured to guide the first wire part around the winding core during winding thereof, and wherein the second guiding unit is configured to guide the second wire part around the winding core during winding thereof.19. Electromagnetic coil manufacturing system according to the preceding clause, wherein the first guiding unit comprises a first planar abutment surface for abutting a left side surface of the first wire part, wherein the second guiding unit comprises a second planar abutmentsurface for abuting a right side surface of the second wire part, wherein the first planar abutment surface and the second planar abutment surface extend parallel to each other, perpendicular to the core axis and around the core axis. Electromagnetic coil manufacturing system according to the preceding clause, wherein the winding core device comprises an adjusting member for adjusting a distance along the core axis between the first planar abutment surface and the second planar abutment surface. Electromagnetic coil manufacturing system according to any one of clauses 17-20, wherein the second wire part supply device comprises a first supply unit and a second supply unit, the second wire part supply device being configured to supply two parallel wires that are located at a distance from each other along the core axis to the winding core, wherein the first supply unit is configured to supply one of the parallel wires to the winding core, and wherein the second supply unit is configured to supply the other of the parallel wires to the winding core. A method for manufacturing an electromagnetic coil according to clause 1, the method comprising the steps: a. providing an electromagnetic coil manufacturing system according to any one of clauses 17 - 21, b. supplying a first wire part and a second wire part to the winding core while winding the first wire part and second wire part on and around the winding core and around each other a plurality of times, wherein by winding at least one channel is formed between o an upper surface of an inner winding of the first wire part or second wire part, o at least one of a left side surface and a right side surface of a first outer winding located on top of the inner winding, and o a lower surface of a second outer winding located on top of the first outer winding. Method according to clause 22, comprising winding the first wire part and second wire part at an offset relative to each other with respect to the core axis, thereby forming a channel on a left side and an opposite channel on a right side of the electromagnetic coil. Method according to clause 22 or 23, wherein the first wire part and second wire part have the same first thickness and first width. Method according to any one of the preceding method clauses, wherein the first wire part has a first width and a first thickness, and wherein the second wire part has a second width and a second thickness, when seen in cross-section, wherein the first width and second width are different and / or wherein the first thickness and second thickness are different, wherein the method comprises connecting a respective first wire part first end of the first wire part and a second wire part first end of the second wire part to form an electrically conductiveconnection.

[0086] 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.

Claims

CLAIMS1. An electromagnetic coil comprising an electrically conductive wire wound with N number of windings about a central axis, wherein N is an integer and at least 3, the wire having a rectangular crosssection with a first width measured along the central axis from a left side surface to a right side surface, and a first thickness measured perpendicular to the first width from an upper surface to a lower surface, wherein, when seen in a cross-sectional plane extending parallel to the central axis, at least one channel is formed between o the upper surface of an inner winding of the electrically conductive wire, o at least one of the left side surface and right side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding.

2. Electromagnetic coil according to claim 1, wherein the electrically conductive wire comprises a first wire part and a second wire part that are connected to each other at a respective first wire part first end and a second wire part first end to form an electrically conductive connection, wherein the first wire part and second wire part are wound around each other, thereby forming an alternating pattern when seen in cross-section.

3. Electromagnetic coil according to any one of the preceding claims, wherein the at least one channel is formed between o the upper surface of an inner winding of the wire, o the left side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding, and wherein at least one opposite channel is formed between o the upper surface of an inner winding of the wire, o the right side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding.

4. Electromagnetic coil according to any one of the preceding claims, wherein the at least onechannel has a U-shape with right-angled comers.

5. Electromagnetic coil according to any one of the preceding claims, comprising a cover member for closing off the at least one channel.

6. A coil assembly comprising at least two electromagnetic coils according to any one of the preceding claims, wherein the at least two electromagnetic coils are placed adjacent to each other with coinciding central axes, wherein an electrically conductive connection located in an inner space enclosed by the innermost winding of an electromagnetic coil is connected to an electrically conductive connection located in an inner space enclosed by the innermost winding of an adjacent electromagnetic coil.

7. Coil assembly according to claim 6, wherein an open side of the at least one channel of one of the electromagnetic coils is closed off by one or more adjacent windings of the adjacent electromagnetic coil.

8. Coil assembly according to claim 6 or 7, wherein an open side of a channel not closed off by an adjacent electromagnetic coil is closed off by a cover member.

9. An actuator comprising an electromagnetic coil according to any one of claims 1-5 or a coil assembly according to any one of claims 6-8.

10. An apparatus comprising an electromagnetic coil according any one of claims 1-5 or a coil assembly according to any one of claims 6-8.

11. An electromagnetic coil manufacturing system, a winding core device comprising a winding core, the winding core being configured to receive an electrically conductive wire, the winding core having a core axis, a first wire part supply device for supplying an electrically conductive first wire part to the winding core, a second wire part supply device for supplying an electrically conductive second wire part to the winding core, a driving device for rotating the winding core about its core axis and / or for orbiting the first wire part supply device and second wire part supply device around the winding core, wherein the winding core is configured to rotate about its core axis for winding theelectrically conductive wire on and around the winding core and / or wherein the first wire part supply device and second wire part supply device are configured to orbit around the core for winding the electrically conductive wire around the winding core, wherein the winding core device comprises a first guiding unit for guiding the electrically conductive wire around the winding core during winding thereof, the first wire part supply device, second wire part supply device and first guiding unit being configured to wind the electrically conductive wire on the winding core in order to form at least one channel between o an upper surface of an inner winding of the electrically conductive wire, o at least one of the left side surface and right side surface of a first outer winding located on top of the inner winding, and o the lower surface of a second outer winding located on top of the first outer winding.

12. Electromagnetic coil manufacturing system according to the preceding claim, wherein the winding core device comprises a second guiding unit, wherein the first guiding unit is configured to guide the first wire part around the winding core during winding thereof, and wherein the second guiding unit is configured to guide the second wire part around the winding core during winding thereof.

13. Electromagnetic coil manufacturing system according to claim 11 or 12, wherein the second wire part supply device comprises a first supply unit and a second supply unit, the second wire part supply device being configured to supply two parallel wires that are located at a distance from each other along the core axis to the winding core, wherein the first supply unit is configured to supply one of the parallel wires to the winding core, and wherein the second supply unit is configured to supply the other of the parallel wires to the winding core.

14. A method for manufacturing an electromagnetic coil according to claim 1, the method comprising the steps: a. providing an electromagnetic coil manufacturing system according to any one of claims 11-13, b. supplying a first wire part and a second wire part to the winding core while winding the first wire part and second wire part on and around the winding core and around each other a plurality of times, wherein by winding at least one channel is formed between o an upper surface of an inner winding of the first wire part or second wire part,o at least one of a left side surface and a right side surface of a first outer winding located on top of the inner winding, and o a lower surface of a second outer winding located on top of the first outer winding.

15. Method according to claim 14, comprising winding the first wire part and second wire part at an offset relative to each other with respect to the core axis, thereby forming a channel on a left side and an opposite channel on a right side of the electromagnetic coil.

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