TW202519997A - Reluctance actuator, positioning device, stage apparatus, lithographic apparatus - Google Patents

Abstract

The invention provides a reluctance actuator configured to exert a substantially upward force on an object, that is displaceable by a mover of a positioning device in a horizontal direction, the reluctance actuator comprising: a first member configured to be connected to the object, a second member configured to be connected to the mover, the first and second member forming a magnetic flux path comprising a gap between the first member and the second member, a permanent magnet arranged in the magnetic flux path to generate a bias magnetic flux in the magnetic flux path, the bias magnetic flux causing a bias upward force on the first member and a coil configured to engage with either the first member or the second member and configured to, when energized, generate a variable magnetic flux in the magnetic flux path, the variable magnetic flux causing a variable force on the first member.

Description

Magnetoresistive actuator, positioning device, stage equipment, lithography equipment

The present invention relates to a magnetoresistive actuator and a positioning device used in lithography equipment.

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

As semiconductor manufacturing processes continue to advance, the size of circuit components has been decreasing steadily over the past few decades, while the number of functional components such as transistors per device has been increasing steadily, following a trend often referred to as "Moore's law." To keep up with Moore's law, the semiconductor industry is pursuing technologies that enable the creation of smaller and smaller features. To project a pattern onto a substrate, lithography equipment may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of a feature that can be patterned onto a substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Lithography equipment using extreme ultraviolet (EUV) radiation having a wavelength in the range of 4 nm to 20 nm (eg, 6.7 nm or 13.5 nm) may be used to form smaller features on a substrate compared to lithography equipment using radiation having a wavelength of, for example, 193 nm.

In order to ensure accurate positioning of the pattern on the substrate, it is important to ensure that the patterning device holding the pattern and the substrate are accurately positioned relative to each other. To achieve this, positioning devices are often used that combine one or more electromagnetic motors and one or more electromagnetic actuators, wherein the one or more electromagnetic motors are used to displace the patterning device or substrate over a relatively large distance and the one or more electromagnetic actuators are used to displace the patterning device or substrate over a relatively small distance and with high accuracy.

At the same time, there is a need to continuously increase the output of lithography equipment, which generally requires an increase in the power of both the electromagnetic motors and the actuators. It has been found difficult to achieve an increase in output using known positioning devices, especially with respect to the applied electromagnetic motors for relatively large displacements. This difficulty is at least partly caused by the applied electromagnetic actuators. The actuators currently used have been optimized primarily for accurate positioning and high efficiency. As a result, such actuators generally operate with a very small operating range. It has been observed that such small operating ranges impose restrictions on the design freedom of the positioning device, thereby limiting the options for achieving a higher output. Therefore, there is a need for different types of actuators that allow for a greater design freedom for the positioning device.

An object of the present invention is to provide an actuator which enables a greater degree of design freedom when the actuator is applied to a positioning device of a lithography apparatus.

According to one aspect of the present invention, a reluctance actuator is provided, which is configured to apply a substantially upward force to an object, and the object can be displaced in a horizontal direction by a mover of a positioning device, and the reluctance actuator includes: A first component, which is configured to be connected to the object; A second component, which is configured to be connected to the mover; The first component and the second component form a magnetic flux path, including a gap between the first component and the second component; A permanent magnet, which is arranged in the magnetic flux path to generate a bias magnetic flux in the magnetic flux path, and the bias magnetic flux generates a bias upward force on the first component; A coil configured to engage with the first component or the second component and configured to generate a variable magnetic flux in the magnetic flux path when energized, the variable magnetic flux generating a variable force on the first component; A first surface of the first component and a first surface of the second component facing each other across the gap are configured to maintain a magnetic flux resistance of the magnetic flux path substantially constant for a displacement of the first component relative to the second component in the horizontal direction by a predetermined distance D.

According to another aspect of the present invention, a positioning device for positioning an object stage is provided, the positioning device comprising: A linear or planar motor for positioning the object stage at a relatively large distance, the linear or planar motor comprising: A stator; A mover configured to displace the object stage relative to the stator; Wherein the positioning device further comprises one or more reluctance actuators according to the present invention, whereby the first part of the one or more reluctance actuators is configured to be connected to the object stage as the object, and whereby the second part of the one or more reluctance actuators is connected to the mover.

The positioning device according to the present invention can be advantageously used in a stage apparatus, which can be used, for example, in an exposure apparatus or a lithography apparatus.

In this invention document, the terms "radiation" and "beam" are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm or 126 nm) and extreme ultraviolet radiation (EUV, e.g., having a wavelength in the range of about 5 nm to 100 nm).

As used herein, the term "reduction mask", "mask" or "patterning device" may be broadly interpreted as referring to a general patterning device that can be used to impart a patterned cross-section to an incident radiation beam, the patterned cross-section corresponding to the pattern to be produced in a target portion of a substrate. In this context, the term "light valve" may also be used. In addition to classical masks (transmissive or reflective; binary, phase-shifting, hybrid, etc.), other examples of such patterning devices include programmable mirror arrays and programmable LCD arrays.

FIG1 schematically depicts a lithography apparatus LA. The lithography apparatus LA comprises an illumination system (also referred to as an illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a mask support (e.g., a mask stage) 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 according to certain parameters; a substrate support (e.g., a wafer stage) 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 according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS is configured to project the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (eg, comprising one or more dies).

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

The term "projection system" PS as used herein should be interpreted broadly to cover various types of projection systems appropriate to the exposure radiation used and/or to other factors such as the use of an immersion liquid or the use of a vacuum, including refractive, reflective, catadioptric, synthetic, magnetic, electromagnetic and/or electro-optical systems, or any combination thereof. Any use of the term "projection lens" herein should be considered synonymous with the more general term "projection system" PS.

The lithography apparatus LA may be of a type in which at least a portion of the substrate may be covered by a liquid with a relatively high refractive index, such as water, so as to fill the space between the projection system PS and the substrate W - this is also known as immersion lithography. More information on immersion technology is given in US6952253, incorporated herein by reference.

The lithography apparatus LA may also be of a type having two or more substrate supports WT (also referred to as a "dual stage"). In such a "multi-stage" machine, the substrate supports WT may be used in parallel, and/or a step of preparing the substrate W for subsequent exposure may be performed on a substrate W on one of the substrate supports WT while another substrate W on another substrate support WT is being used to expose a pattern on the other substrate W.

In addition to the substrate support WT, the lithography apparatus LA may also comprise a measurement stage. The measurement stage is configured to hold sensors and/or cleaning devices. The sensors may be configured to measure properties of the projection system PS or of the radiation beam B. The measurement stage may hold a plurality of sensors. The cleaning device may be configured to clean parts of the lithography apparatus, such as parts of the projection system PS or parts of a system for providing an immersion liquid. The measurement stage may be moved under the projection system PS when the substrate support WT is away from the projection system PS.

In operation, a radiation beam B is incident on a patterning device (e.g. a mask) MA held on a mask support MT and is patterned by a pattern (design layout) present on the patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of the substrate W. By means of a second positioner PW and a position measurement system IF, the substrate support WT can be accurately moved, for example so that different target portions C are positioned at focused and aligned positions in the path of the radiation beam B. Similarly, a first positioner PM and possibly a further position sensor (which is not explicitly depicted in FIG. 1 ) can be used to accurately position the patterning device MA relative to the path of the radiation beam B. The mask alignment marks M1, M2 and substrate alignment marks P1, P2 may be used to align the patterning device MA and the substrate W. Although the substrate alignment marks P1, P2 are shown occupying dedicated target portions, the marks may be located in spaces between target portions. When the substrate alignment marks P1, P2 are located between target portions C, the substrate alignment marks P1, P2 are referred to as scribe line alignment marks.

To illustrate the present invention, a Cartesian coordinate system is used. A Cartesian coordinate system has three axes, namely, an x-axis, a y-axis, and a z-axis. Each of the three axes is orthogonal to the other two axes. A rotation about the x-axis is called an Rx rotation. A rotation about the y-axis is called an Ry rotation. A rotation about the z-axis is called an Rz rotation. The x-axis and the y-axis define a horizontal plane, while the z-axis is in the vertical direction. The Cartesian coordinate system does not limit the present invention and is only used for illustration. Alternatively, another coordinate system, such as a cylindrical coordinate system, may be used to illustrate the present invention. The orientation of the Cartesian coordinate system may be different, for example, so that the z-axis has a component along the horizontal plane.

FIG2 shows a more detailed view of part of the lithography apparatus LA of FIG1 . The lithography apparatus LA may have a base frame BF, a counterweight 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 parts of the position measurement system PMS. The metrology frame MF is supported by the base frame BF via a vibration isolation system IS. The vibration isolation system IS is configured to prevent or reduce vibrations from the base frame BF being propagated to the metrology frame MF.

The second positioner PW is configured to accelerate the substrate support WT by providing a driving force between the substrate support WT and the balancing mass BM. The driving force accelerates the substrate support WT in the desired direction. Due to conservation of momentum, a driving force is also applied to the balancing mass BM with an equal magnitude but in the opposite direction to the desired direction. Typically, the mass of the balancing mass BM is significantly greater than the mass of the second positioner PW and the moving parts of the substrate support WT.

In one embodiment, the second positioner PW is supported by a balancing block BM. For example, the second positioner PW includes a planar motor for suspending the substrate support WT above the balancing block BM. In another embodiment, the second positioner PW is supported by a base frame BF. For example, the second positioner PW includes a linear motor and the second positioner PW includes a bearing, such as a gas bearing, for suspending the substrate support WT above the base frame BF.

The position measurement system PMS may comprise any type of sensor suitable for determining the position of the substrate support WT. The position measurement system PMS may comprise any type of sensor suitable for determining the position of the mask 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, such as a metrology frame MF or a projection system PS. The position measurement system PMS may determine the position of the substrate table WT and/or the mask support MT by measuring the position or by measuring the time derivative of the position, such as velocity or acceleration.

The position measurement system PMS may comprise an encoder system. For example, the encoder system is known from US patent application US2007/0058173A1 filed on September 7, 2006, which is hereby incorporated 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 and the secondary radiation beam originate from the same radiation beam, i.e. the original radiation beam. At least one of the primary radiation beam and the secondary radiation beam is generated by diffusing the original radiation beam using a grating. If both a primary radiation beam and a secondary radiation beam are generated by diffracting an original radiation beam using a grating, the primary radiation beam needs to have a different diffraction order compared to the secondary radiation beam. For example, the different diffraction orders are + ^1st order, ^-1st order, + ^2nd order and ^-2nd order. The encoder system optically combines the primary radiation beam and the secondary radiation beam into a combined radiation beam. The sensor in the encoder head determines the phase or phase difference of the combined radiation beam. The sensor generates a signal based on the phase or phase difference. The signal indicates the position of the encoder head relative to the grating. One of the encoder head and the grating can be configured 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, a plurality of encoder heads are arranged on the metrology frame MF, and the grating is arranged on the top surface of the substrate support WT. In another example, the grating is arranged on the bottom surface of the substrate support WT, and the encoder head is arranged below the substrate support WT.

The position measurement system PMS may comprise an interferometer system. For example, an interferometer system is known from US patent US6,020,964 filed on July 13, 1998, which is hereby incorporated by reference. The interferometer system may comprise a beam splitter, a mirror, a reference mirror and a sensor. The radiation beam is split by the beam splitter into a reference beam 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 the phase or frequency of the combined radiation beam. The sensor generates a signal based on the phase or the frequency. The signal represents the displacement of the mirror. In one embodiment, the mirror is connected to a substrate support WT. The reference mirror can be connected to a metrology frame MF. In one embodiment, the measuring beam and the reference beam are combined into a combined radiation beam by an additional optical component instead of a beam splitter.

The first positioner PM may include a long-stroke module and a short-stroke module. The short-stroke module is configured to move the mask support MT with high accuracy over a small range of motion relative to the long-stroke module. The short-stroke module may, for example, include a set of actuators for positioning the mask support MT in multiple degrees of freedom, such as 6 degrees of freedom. In one embodiment, the present invention provides a positioning device, which can act as a first positioner PM and includes a set of magnetoresistive actuators according to the present invention for positioning the mask support MT. The set of magnetoresistive actuators can, for example, be applied to position the mask support MT in a vertical direction. The long-stroke module is configured to move the short-stroke module with relatively low accuracy over a large range of motion relative to the projection system PS. To do this, the long-stroke module may, for example, have a mover that supports or holds the short-stroke module, and a stator that cooperates with the mover to displace the mover over a large range of motion. The large range of motion is, for example, oriented in a substantially horizontal direction. Note that in such a configuration, the stator does not need to remain stationary during operation, but may also be mounted on a balancing block. By means of the combination of the long-stroke module and the short-stroke module, the first positioner PM is able to move the mask support MT relative to the projection system PS over a large range of motion with high accuracy.

Similarly, the second positioner PW may include a long-stroke module and a short-stroke module. The short-stroke module is configured to move the substrate support WT with high accuracy relative to the long-stroke module over a small range of motion. The short-stroke module may, for example, include a set of actuators for positioning the substrate support WT in multiple degrees of freedom, such as 6 degrees of freedom. In one embodiment, the present invention provides a positioning device, which can act as a second positioner PW and includes a set of magnetoresistive actuators according to the present invention for positioning the substrate support WT. The set of magnetoresistive actuators can, for example, be applied to position the substrate support WT in a vertical direction. The long-stroke module is configured to move the short-stroke module with relatively low accuracy relative to the projection system PS over a large range of motion. To do this, the long-stroke module may, for example, have a mover that supports or holds the short-stroke module, and a stator that cooperates with the mover to displace the mover over a large range of motion. The large range of motion is, for example, oriented in a substantially horizontal plane. Note that in such a configuration, the stator does not need to remain stationary during operation, but may also be mounted on a balancing block. By means of 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 over a large range of motion with high accuracy.

The first positioner PM and the second positioner PW each have an actuator to move the mask support MT and the substrate support WT, respectively. The actuator may be a linear actuator that provides a driving force along a single axis (e.g., the y-axis). Multiple linear actuators may be applied to provide a driving force along multiple axes. The actuator may be a planar actuator that provides a driving force along multiple axes. For example, the planar actuator may be configured 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 configured to move the at least one coil relative to the at least one magnet by applying a current to the at least one coil. The actuator may be a moving magnet type actuator having at least one magnet coupled to the substrate support WT and to the mask support MT, respectively. The actuator may be a moving coil type actuator having at least one coil coupled to the substrate support WT and to the mask support MT, respectively. The actuator may be a voice coil actuator, a magnetoresistive actuator, a Lorentz actuator or a piezoelectric actuator, or any other suitable actuator.

The lithography apparatus LA comprises a position control system PCS as schematically depicted in FIG3 . The position control system PCS comprises a set point generator SP, a feedforward controller FF and a feedback controller FB. The position control system PCS provides a drive signal to an actuator ACT. The actuator ACT may be an actuator of a first positioner PM or a second positioner PW. The actuator ACT drives a plant P, which may include a substrate support WT or a mask support MT. The output of the plant P is a position quantity, such as position or velocity or acceleration. The position quantity is measured using a position measurement system PMS. The position measurement system PMS generates a signal, which is a position signal representing the position quantity of the plant P. The set point generator SP generates a signal, which is a reference signal representing the desired position quantity of the plant P. For example, the reference signal represents the desired trajectory of the substrate support WT. The difference between the reference signal and the position signal forms an input for a feedback controller FB. Based on the input, the feedback controller FB provides at least a portion of the drive signal to the actuator ACT. The reference signal may form an input for a feedforward controller FF. Based on the input, the feedforward controller FF provides at least a portion of the drive signal to the actuator ACT. The feedforward FF may utilize information about the dynamic characteristics of the device P, such as mass, stiffness, resonant modes and natural frequencies.

FIG. 4 schematically shows a magnetoresistive actuator 400 according to the present invention. Such an actuator can be applied, for example, to the aforementioned first positioner or second positioner, in particular as part of the mentioned short-stroke module. In particular, the magnetoresistive actuator according to the present invention can be applied to support an object, such as an object stage such as a mask support MT or a substrate support WT, and to control the position of the object in the vertical direction. The actuator 400 shown comprises a first component 410 and a second component 420. The first component and the second component of the magnetoresistive actuator according to the present invention can also be referred to as magnetic components, i.e. components made of or comprising magnetically conductive material. The first component 410 is configured to be connected to the supported object. In the illustrated embodiment, the first member 410 includes a C-shaped core structure 412 and a connecting member 414 for connecting to a supported object. In the illustrated embodiment, the connecting member 414 has a bottom end 414.1 connected to the C-shaped core structure 412 of the first member 410 and a top end 414.2 configured to connect to the object. In the illustrated embodiment, the top end 414.2 is disposed above a top surface 420.1 of the second member 420 during use.

According to the present invention, the second component 420 is configured to be connected to a mover of a positioning device, which is used to shift the object in the horizontal direction. Such a positioning device can be, for example, the aforementioned first positioner PM or the second positioner PW.

According to the present invention, the first component 410 and the second component 420 form a magnetic flux path, indicated by dotted line 440, which includes a gap 450 between the first component 410 and the second component 420. The reluctance actuator 400 according to the present invention further includes a permanent magnet 460, which is arranged in the magnetic flux path 440 and is configured to generate a bias magnetic flux in the magnetic flux path, which bias magnetic flux generates a bias upward force on the first component 410. In the embodiment shown, the permanent magnet or magnets 460 are arranged in the magnetic flux path of the second component 420. It should be noted that in an alternative embodiment, the permanent magnet or magnets can also be arranged in the magnetic flux path of the first component 410. In one embodiment, the bias upward force of the actuator can be configured to offset a majority of the weight of the object.

The reluctance actuator 400 further includes a coil 470 configured to engage with either the first member 410 or the second member 420 and configured to generate a variable magnetic flux in the magnetic flux path when energized, the variable magnetic flux generating a variable force on the first member 410. In the illustrated embodiment, the coil 470 is wound around a portion of the second member 420. During use, the generated variable force can be applied, for example, to accurately position an object to which the first member 410 is connected.

According to the present invention, a first surface of the first component 410 and a first surface of the second component 420 facing each other across the gap 450 are configured to maintain a flux resistance of the flux path 440 substantially constant for displacement of the first component relative to the second component in a horizontal direction (e.g., in the indicated X direction or Y direction) by a predetermined distance. This is illustrated in more detail below. To ensure that the flux resistance remains substantially constant for displacement across a predetermined distance in the horizontal direction, one may choose to have facing first surfaces of different sizes.

Due to the design characteristics mentioned above, the magnetoresistive actuator according to the present invention provides an additional degree of operating freedom for positioning devices that move objects in the horizontal direction. This situation can be understood as follows. When a magnetoresistive actuator (such as actuator 400) is applied for the precise positioning of an object, for example as part of a short-stroke module as mentioned above, the object is usually controlled to follow a specific trajectory, such as a trajectory in an XY plane, during which the object can undergo different programs. In known positioning devices, it is necessary that the mover of the positioning device (such as part of the long-stroke module mentioned above) essentially follows the same trajectory in the XY plane. This is due to the fact that known vertical actuators, such as those used in short-stroke modules, are not designed to allow displacements in the horizontal plane. However, the use of a magnetoresistive actuator according to the invention enables or allows a horizontal displacement of the mover of the positioning device relative to the object. This is due to the specific design of the magnetoresistive actuator according to the invention, whereby this mover is connected to the second part of the magnetoresistive actuator, the object is connected to the first part of the magnetoresistive actuator, and the actuator is designed to allow displacement over a predetermined distance in the horizontal direction. This provides an additional degree of operating freedom for the positioning device, since the mover of the positioning device does not need to follow the object exactly. This additional degree of operating freedom can, for example, allow the mover to lag behind the object instead of following it. As a result, less power is required to operate the positioning device. In this regard, reference can be made, for example, to US 2004/0257548, which is incorporated herein by reference in its entirety.

FIG. 5 schematically shows two views of the actuator of FIG. 4 in the YZ plane, wherein the first component and the second component are in two different relative positions.

Fig. 5 (a) schematically shows the first component 410 and the second component 420 of the reluctance actuator 400 of Fig. 4, wherein the first component 410 is located at the rightmost position. It should be noted that the connecting component of the first component has been omitted in Fig. 5.

FIG5(b) schematically shows the first component 410 and the second component 420 of the reluctance actuator 400 of FIG4 , wherein the first component 410 is at the leftmost position.

In the embodiment shown, the surfaces of the first and second components that face each other across the gap 450 are selected so that the magnetic flux resistance remains substantially the same regardless of the relative position of the first and second components. In the embodiment shown, the first component 410 has a first surface 410.1 facing the first surface 420.1 of the second component. The surface 410.1 of the first component 410 has a width W1 that is less than the width W2 of the surface 420.1 of the second component 420 in the Y direction.

In FIG. 5(a), surfaces 410.1 and 420.1 are aligned on the right side, and in FIG. 5(b), they are aligned on the left side. As will be appreciated by those skilled in the art, the flux resistance will be substantially the same in both positions and in any position between the positions of FIG. 5(a) and FIG. 5(b). Thus, in the embodiment shown in FIG. 5(a) and (b), the first component 410 and the second component 420 can be displaced relative to each other by a distance D without a significant change in the resulting vertical force, whereby D satisfies the following requirement: W2 - W1 = D                          (1)

As will be appreciated by those skilled in the art, the requirement according to equation (1) is merely a rule of thumb for obtaining a substantially constant flux resistance for a displacement over a distance D. For example, W2-W1 may be greater than D so that the flux resistance remains substantially constant for a displacement over a distance D. The actual distance or displacement that can be produced for a given expected force variation limit will depend on various parameters, such as the actual dimensions of the surfaces 410.1 and 420.1, the size of the gap 450, the degree of saturation, etc. By means of simulation, such as finite element simulation, one can determine, for example, for a given design of the first part 410 and the second part 420, a distance, also referred to as a predetermined distance D, which allows the first part 410 to be horizontally displaced relative to the second part 420. As mentioned, due to the possibility of displacing the first part 410 relative to the second part 420, an additional degree of freedom of operation is obtained for the positioning device, in particular for the long stroke modules of this positioning device. With reference to FIG. 5 , it can be understood that the position of the object to be displaced and connected to the first part 410 can be at a distance D or less from the position of the mover of the positioning device configured to be connected to the second part 420 in the X direction. In other words, due to the design properties of the first surface of the first component and the second component in the X direction, the mover of the positioning device does not need to follow the set point of the object exactly in the X direction. This degree of operational freedom allows, for example, the positioning device to be operated with lower power requirements.

With regard to maintaining the flux resistance substantially constant for a predetermined displacement in the indicated Y direction, it can be pointed out that a similar effect can be obtained by designing the surface 410.1 of the first part 410 to have a width W1 that is greater than the width W2 of the surface 410.2 of the second part 420 in the Y direction. In this case, the first part 410 and the second part 420 can be displaced relative to each other by a distance D without a significant change in the resulting vertical force, whereby D satisfies the following requirement: W1 - W2 = D                      (2)

As will be appreciated by those skilled in the art, the requirement according to equation (2) is merely an empirical rule for obtaining a substantially constant flux resistance for a displacement over a distance D. For example, W1-W2 may also be greater than D, so that the flux resistance remains substantially constant for a displacement over a distance D.

FIG5 schematically illustrates a possible relative displacement of the first component 410 and the second component 420 in the Y direction. A similar displacement in the X direction, i.e. a displacement that does not substantially affect the flux resistance and therefore the vertical force generated, is also possible. This is illustrated in FIG6 for the reluctance actuator shown in FIG4.

FIG. 6 schematically shows two views of the actuator of FIG. 4 in the XZ plane, wherein the first component and the second component are in two different relative positions.

FIG6(a) schematically shows the first component 410 and the second component of the reluctance actuator 400 of FIG4 , wherein the first component 410 is in a first position.

Fig. 6(b) schematically shows the first component 410 and the second component of the magnetoresistive actuator 400 of Fig. 4, wherein the first component 410 is in a second position, further to the right than the position in Fig. 6(a). Similar observations can be made for displacement along the X direction as for displacement along the Y direction; the width W3 of the first surface 410.1 of the first component 410 in the X direction and the width W4 of the first surface 420.1 of the second component 420 in the X direction can be constructed in such a way that the displacement of the first component 410 relative to the second component 420 in the X direction has no or little effect on the magnetic flux resistance and therefore has no or little effect on the generated upward force.

As a result, similar additional operating freedom as discussed with reference to FIG. 5 is also obtained in the X direction.

In an embodiment of a magnetoresistive actuator according to the present invention as shown in FIGS. 4 to 6 , the actuator 400 comprises: a first component 410 comprising a C-shaped core structure 412 arranged in a substantially vertical plane; and a second component 420 comprising a C-shaped core arranged in a substantially horizontal plane.

FIG7 schematically illustrates an alternative embodiment of a magnetoresistive actuator according to the present invention. FIG7 schematically shows a YZ view of an embodiment of a magnetoresistive actuator 700 according to the present invention, which can also be applied in the aforementioned first positioner or second positioner, in particular as part of the mentioned short-stroke module. In particular, the magnetoresistive actuator according to the present invention can be applied to support an object, such as an object stage such as a mask support MT or a substrate support WT, and control the position of the object in the vertical direction. The actuator 700 shown comprises a first part 710 and a second part 720. The first part 710 is configured to be connected to the supported object, which is indicated by the dotted line 702. In the illustrated embodiment, the first member 710 includes a C-shaped core structure 712 and a connecting member 714 for connecting to the supported object 702.

According to the present invention, the second component 720 is configured to be connected to a mover of a positioning device, which is used to shift the object in the horizontal direction. Such a positioning device can be, for example, the aforementioned first positioner PM or the second positioner PW.

According to the present invention, the first member 710 and the second member 720 form a magnetic flux path, indicated by dotted line 740, which includes a gap 750 between the first member 710 and the second member 720. The reluctance actuator 700 further includes a permanent magnet 760, which is disposed in the magnetic flux path 740 and is configured to generate a bias magnetic flux in the magnetic flux path, which bias magnetic flux generates a bias upward force on the first member 710. In the embodiment shown, one or more permanent magnets 760 are disposed in the magnetic flux path of the second member 720. It should be noted that in alternative embodiments, one or more permanent magnets can also be disposed in the magnetic flux path of the first member 710. In one embodiment, the bias upward force of the actuator can be configured to offset a majority of the weight of the object 702.

The reluctance actuator 700 further includes a coil 770 configured to engage with either the first member 710 or the second member 720 and configured to generate a variable magnetic flux in the magnetic flux path when energized, the variable magnetic flux generating a variable force on the first member 710. In the embodiment shown, the coil 770 is wound around a portion of the second member 720. During use, the generated variable force can be applied, for example, to accurately position an object to which the first member 710 is connected.

According to the present invention, the first surface 710.1 of the first component 710 and the first surface 720.1 of the second component 720 facing each other across the gap 750 are configured to maintain the flux resistance of the flux path 740 substantially constant for a displacement of the first component 710 relative to the second component 720 by a predetermined distance in the horizontal direction (i.e., the Y direction in FIG. 7 ). This is achieved by selecting the width W1 of the first surface 710.1 of the first component 710 to be smaller than the width W2 of the first surface 720.1 of the second component 720 in a similar manner as discussed with reference to FIG. 5 . Thereby, the aforementioned additional degree of freedom of operation of the mover for the positioning device is obtained. Compared to the magnetoresistive actuator 400 shown in Figures 4 to 6, the magnetoresistive actuator 700 has: a first component 710, which includes a C-shaped core structure 712 arranged in a substantially vertical plane; and a second component 720, which includes a C-shaped core arranged in the same substantially vertical plane, whereby the C-shaped core of the second component 720 substantially encloses the C-shaped core structure 712 of the first component 710.

It can be pointed out that the first component and/or the second component of the reluctance actuator according to the present invention can also include other structures besides the C-shaped core structure. Such structures include, for example, E-shaped core or I-shaped core structures or structures with circular symmetry, as shown below.

To obtain similar additional operational freedom in the X direction perpendicular to the YZ plane shown in Figure 7, the width of the first surface 710.1 of the first component 710 in the X direction can be selected to be smaller or larger than the width of the first surface 720.1 of the second component 720 in the X direction.

FIG8 schematically shows another example of a reluctance actuator according to the present invention.

FIG8 schematically shows a magnetoresistive actuator 800 having circular symmetry. The magnetoresistive actuator 800 includes a first member 810 having a top plate 812 and a bottom plate 814, the top plate 812 and the bottom plate 814 being substantially parallel to each other and separated by a holder 816. The first member is configured to be connected to an object indicated by dotted line 802. A second member 820 of the magnetoresistive actuator 800 is disposed between the top plate 812 and the bottom plate 814. The second member 820 includes an inner cylinder 822, a radially magnetized permanent magnet 824 disposed concentrically around the inner cylinder 822, a cylindrical coil 826 disposed around the inner magnetic cylinder 822, and an outer cylinder 828 disposed concentrically around the radially magnetized permanent magnet 824. In the embodiment shown, two cylindrical coils 826 are applied, one above the permanent magnet 824 and one below the permanent magnet 824. In one embodiment, a single coil 826 may also be applied. In the embodiment shown, the top surfaces of the inner cylinder 822 and the outer cylinder 828 are spaced apart from the bottom surface 812.1 of the top plate 812 by a distance D1, thereby forming a first gap between the first member 810 and the second member 820. The bottom surfaces of the inner cylinder 822 and the outer cylinder 828 are spaced apart from the top surface 814.1 of the bottom plate 814 by a distance D2, thereby forming a second gap.

The mentioned components of the first part 810, the second part 820 and the first gap and the second gap form a magnetic flux path. In FIG. 8, dotted line 840 shows the magnetic flux path of the bias magnetic flux caused by the permanent magnet 824. This bias magnetic flux will cause a vertically directed force between the first part 810 and the second part 820. In the case where the second gap D2 is smaller than the first gap D1, as shown, the resulting force acting on the first part 810 will be an upward force. In this case, the bias magnetic flux caused by the permanent magnet 824 thus generates an upward bias force on the first part 810. When the coil 826 is energized (i.e., supplied with current), this can cause a variable magnetic flux in the magnetic flux path. In FIG. 8, dotted line 842 shows the magnetic flux path of the variable magnetic flux caused by the coil 826. Depending on the orientation of the current applied to the coil 826, the variable magnetic flux will cause an increase or decrease in the magnetic flux across the first gap and the second gap, and therefore cause an increase or decrease in the resulting upward force acting on the first member 810. Thus, the current applied to the coil 826 can produce a variable force on the first member 810 and therefore on the object 802 during use.

According to the present invention, the reluctance actuator 800 is configured in such a way that the first part 810 can be displaced in the horizontal direction relative to the second part 820 while substantially maintaining the flux resistance of the flux path. In the embodiment shown in FIG8 , this is achieved by selecting the diameter D3 of the top plate and the bottom plate to be larger than the outer diameter D4 of the outer cylinder 828. Compared to the embodiment of FIGS. 4 to 7 , the top surface and the bottom surface of the inner cylinder 822 and the outer cylinder 828 can be considered as the first surface of the first part 810, while the bottom surface 812.1 of the top plate 812 and the top surface 814.1 of the bottom plate 814 can be considered as the first surface of the second part 820. The surfaces face each other across a gap having a distance D1 and a distance D2 and are configured to maintain a flux resistance of the flux path substantially constant for a displacement of the first component relative to the second component in a horizontal direction over a predetermined distance.

In one embodiment, a reluctance actuator according to the present invention, such as actuator 400, 700 or 800, may include one or more sensors, such as Hall sensors, configured to measure the magnetic flux in the magnetic flux path. Such one or more sensors or magnetic sensors may, for example, be applied at or near the surfaces of the first part and/or the second part of the actuator facing each other across the gap of the actuator. Based on the signals obtained from such one or more sensors, a more accurate control of the generated force and or position of the actuator may be obtained.

8 , such sensors may be disposed, for example, at or near the top and bottom surfaces of the inner cylinder 822 and the outer cylinder 828.

5 and 7 , such a sensor may be disposed, for example, at or near the surface 410 . 1 or 710 . 1 of the first component of the actuator 400 or 700 .

Referring to FIG. 8 , such sensors may be arranged, for example, at or near the top and bottom surfaces of the inner cylinder 822 and the outer cylinder 828. In one embodiment of the present invention, the surfaces of the inner cylinder 822 and/or the outer cylinder 828 where the sensors are located may be provided with teeth. Such teeth will cause the magnetic flux crossing the gap to be concentrated at the location of the teeth. By arranging the sensors on the teeth, an improved signal-to-noise ratio of the sensor signal may be obtained. It may be noted that such tooth structures may also be applied to the surfaces 410.1 and 420.1 of the first component 410 and the second component 420 of the actuator 400 shown in FIGS. 4 to 6 .

FIG9 schematically shows another embodiment of a magnetoresistive actuator 900 according to the present invention.

FIG. 9 schematically shows a magnetoresistive actuator 900 having circular symmetry, similar to the actuator 800 according to the present invention. The magnetoresistive actuator 900 comprises a first component 910 having a circular plate 912 and a first connecting component 914, which can be used, for example, to be connected to an object to be positioned. The circular plate 912 can be made, for example, of a magnetically conductive material. The magnetoresistive actuator 900 further comprises a second component 920. The second component 920 comprises a magnetic component 922, a permanent magnet 924 and a coil 926. In the embodiment shown, a gap 950 is formed between the first component 910 and the second component 920. The actuator 900 further comprises a second connecting component 928, which can be used, for example, to connect the second component 920 to a mover of a positioning device, which mover is used to displace the object in a horizontal direction.

The circular plate 912 of the first component 910, the magnetic component 922, the permanent magnet 924, and the gap 950 form a magnetic flux path, as indicated by the dotted line 940. In FIG. 9, the dotted line 940 illustrates the magnetic flux path of the bias magnetic flux caused by the permanent magnet 924. Such bias magnetic flux can generate a bias upward force on the first component 910. In the embodiment shown, the permanent magnet 924 is arranged in the magnetic flux path of the second component 920. It should be noted that in an alternative embodiment, the permanent magnet can also be arranged in the magnetic flux path of the first component 910, especially in the plate 912. In one embodiment, the bias upward force of the actuator can be configured to offset most of the weight of the object.

The reluctance actuator 900 further includes a coil 926 configured to engage with either the first member 910 or the second member 920 and configured to generate a variable magnetic flux in the magnetic flux path when energized, the variable magnetic flux generating a variable force on the first member 910. In the embodiment shown, the coil 926 is wound around a portion of the magnetic member 922 of the second member 920. During use, the generated variable force can be applied, for example, to accurately position an object to which the first member 910 is connected.

According to the present invention, the surfaces of the first member 910 and the second member 920 facing each other across the gap 950 are configured to maintain the magnetic flux resistance of the magnetic flux path 940 substantially constant for displacement of the first member relative to the second member in the horizontal direction. Specifically, as will be understood by those skilled in the art, displacement of the first member 910 relative to the second member 920 in the radial direction indicated by arrow 960 will have no or little effect on the magnetic flux resistance along the magnetic flux path 940.

As a result, due to the design characteristics mentioned above, the reluctance actuator 900 according to the present invention provides additional operating freedom for a positioning device for moving an object in a horizontal direction.

With regard to the application of one or more permanent magnets to generate a biasing magnetic flux along the magnetic flux path of the reluctance actuator according to the invention, it may be mentioned that these permanent magnets may be located in the first part and/or the second part. It may also be pointed out that one or more permanent magnets may be applied at substantially various locations in the first part and/or the second part without affecting the operation of the actuator. As an illustration only, FIG9 b schematically shows a variant 900 ′ of the actuator 900 shown in FIG9 a . The reluctance actuator 900' schematically shown in FIG. 9b is identical to the actuator 900 shown in FIG. 9a except that, compared to the actuator 900, the permanent magnet 924 of the actuator 900, which may be, for example, an axially magnetized ring magnet, has been replaced by a magnet 924', which may be, for example, a radially magnetized ring magnet. The magnet 924' has been repositioned compared to the position of the magnet 924 of FIG. 9a. In particular, the magnetic part 922 of the reluctance actuator 900 has been replaced by a magnetic part 922' comprising a pair of concentric cylinders, the permanent magnet 924' being located in the radial gap between the two cylinders. Apart from these modifications, the operation and characteristics of the actuator 900' correspond substantially to the operation and characteristics of the actuator 900 shown in FIG. 9a.

FIG10 schematically shows another embodiment of a magnetoresistive actuator 1000 according to the present invention.

FIG. 10 schematically shows a magnetoresistive actuator 1000 having circular symmetry, similar to the actuator 900 according to the present invention. The magnetoresistive actuator 1000 comprises a first part 1010, which can, for example, be connected to an object to be positioned. The first part 1010 can, for example, be made of a magnetically conductive material. The magnetoresistive actuator 1000 further comprises a second part 1020. The second part 1020 comprises a magnetic part 1022, a permanent magnet 1024 and a coil 1026. In the embodiment shown, a gap 1050 is formed between the first part 1010 and the second part 1020. The second part 1020 can, for example, be connected to a mover of a positioning device, which is used to displace the object in a horizontal direction. The first part 1010 can form a circular plate or a shape suitable for forming the gap 1050.

The first component 1010, the magnetic component 1022, the permanent magnet 1024, and the gap 1050 form a magnetic flux path, as indicated by the dotted line 1040. In FIG. 10, the dotted line 1040 depicts the magnetic flux path of the biasing magnetic flux caused by the permanent magnet 1024. Such biasing magnetic flux can generate a biasing upward force on the first component 1010. In the embodiment as shown, the permanent magnet 1024 is disposed in the magnetic flux path of the second component 1020. It should be noted that in alternative embodiments, the permanent magnet can also be disposed in the magnetic flux path of the first component 1010. In one embodiment, the biasing upward force of the actuator can be configured to offset a majority of the weight of the object.

The reluctance actuator 1000 further includes a coil 1026 configured to engage with either the first component 1010 or the second component 1020 and configured to generate a variable magnetic flux in the magnetic flux path when energized, the variable magnetic flux generating a variable force on the first component 1010. In the embodiment shown, the coil 1026 is wound around a portion of the magnetic component 1022 of the second component 1020. During use, the generated variable force can be applied, for example, to accurately position an object to which the first component 1010 is connected.

According to the present invention, the surfaces of the first component 1010 and the second component 1020 facing each other across the gap 1050 are configured to maintain the magnetic flux resistance of the magnetic flux path 1040 substantially constant for displacement of the first component relative to the second component in the horizontal direction. In particular, as will be understood by those skilled in the art, displacement of the first component 1010 relative to the second component 1020 over a distance D in the radial direction indicated by arrow 1060 will have no or little effect on the magnetic flux resistance along the magnetic flux path 1040.

As a result, due to the design characteristics mentioned above, the reluctance actuator 1000 according to the present invention provides additional operating freedom for a positioning device that moves an object in a horizontal direction.

FIG11 schematically shows another embodiment of a magnetoresistive actuator 1100 according to the present invention.

FIG. 11 schematically shows a magnetoresistive actuator 1100 having circular symmetry, similar to the actuator 1000 according to the invention. The magnetoresistive actuator 1100 comprises a first part 1110, which can, for example, be connected to an object to be positioned. The first part 1110 can, for example, be made of a magnetically conductive material. The magnetoresistive actuator 1100 further comprises a second part 1120. The second part 1120 comprises a magnetic part 1122, a permanent magnet 1124 and a coil 1126. In the embodiment shown, a gap 1150 is formed between the first part 1110 and the second part 1120. The second part 1120 can, for example, be connected to a mover of a positioning device, which is used to displace the object in a horizontal direction. The first component 1110 is configured to have structures, such as 1111.1 and 1111.2, facing the second component 1120, thereby forming gaps 1150.1 and 1150.2.

The first component 1110, the magnetic component 1122, the permanent magnet 1124, and the gaps 1150.1, 1150.2 form a magnetic flux path, as indicated by the dotted line 1140. In FIG. 11, the dotted line 1140 depicts the magnetic flux path of the bias magnetic flux caused by the permanent magnet 1124. Such a bias magnetic flux can produce a bias upward force on the first component 1110. In the embodiment as shown, the permanent magnet 1124 is arranged in the magnetic flux path of the second component 1120. It should be noted that in an alternative embodiment, the permanent magnet can also be arranged in the magnetic flux path of the first component 1110. In one embodiment, the bias upward force of the actuator can be configured to offset a majority of the weight of the object.

The reluctance actuator 1100 further includes a coil 1126 configured to engage with either the first member 1110 or the second member 1120 and configured to generate a variable magnetic flux in the magnetic flux path when energized, the variable magnetic flux generating a variable force on the first member 1110. In the illustrated embodiment, the coil 1126 is wound around a portion of the magnetic member 1122 of the second member 1120. During use, the generated variable force can be applied, for example, to accurately position an object to which the first member 1110 is connected.

According to the present invention, the surfaces of the first component 1110 and the second component 1120 that face each other across the gap 1150.1 and 1150.2 are configured to maintain a flux resistance of the flux path 1140 substantially constant for a displacement of the first component relative to the second component in a horizontal direction. Specifically, as will be understood by one skilled in the art, a displacement of the first component 1110 relative to the second component 1120 over a distance D in a radial direction indicated by arrow 1160 will have no or little effect on the flux resistance along the flux path 1140.

As a result, due to the design characteristics mentioned above, the magnetoresistive actuator 1100 according to the present invention provides an additional degree of operating freedom for a positioning device that moves an object in the horizontal direction.

With regard to the application of one or more permanent magnets to generate a bias flux along the flux path of the reluctance actuator according to the invention, it can be mentioned that these permanent magnets can be located in the first part and/or the second part. It can also be pointed out that one or more permanent magnets can be applied at substantially any position in the first part and/or the second part without affecting the operation of the actuator.

With respect to the magnetic flux paths and magnetic fluxes caused by the permanent magnets and coils of the actuator according to the present invention, it can be pointed out that the magnetic flux path of the bias magnetic flux generated by the permanent magnets need not be the same as the magnetic flux path of the variable magnetic flux generated by the coils. The reluctance actuator 800 according to the present invention has been illustrated in this case; the magnetic flux path 840 of the bias magnetic flux generated by the permanent magnets 824 is different from the magnetic flux path 842 of the variable magnetic flux generated by the coils 826. In general, the magnetic flux paths of the reluctance actuator according to the present invention may include a first magnetic flux path followed by the bias magnetic flux and a second magnetic flux path followed by the variable magnetic flux. These first magnetic flux paths and second magnetic flux paths may be separate paths, may partially overlap, or may completely overlap with each other.

The first and second components of the reluctance actuator according to the invention as described above form a magnetic flux path. Thus, it can be manufactured, for example, using ferromagnetic material or the like in order to provide a path with relatively low magnetic flux resistance.

In one embodiment of the present invention, a positioning device for positioning an object or an object stage is provided, the positioning device comprising: - a linear or planar motor for positioning the object or the object stage over a relatively large distance, the linear or planar motor comprising: a stator; a mover configured to displace the object stage relative to the stator; - one or more reluctance actuators according to the present invention, whereby the first part of the one or more reluctance actuators is configured to be connected to the object or the object stage, and whereby the second part of the one or more reluctance actuators is connected to the mover.

Such a positioning device may, for example, be applied in a lithography apparatus or an exposure apparatus, for example to position a mask table MT or a substrate table WT as indicated above. Therefore, in one embodiment of the invention, a stage apparatus is provided comprising an object table and a positioning device according to the invention. The object table of the stage apparatus may, for example, be a mask table or a substrate table.

Although specific reference may be made herein to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection for magnetic resonance memory, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

Although specific reference may be made herein to embodiments of the invention in the context of lithography apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or a mask (or other patterned device). Such apparatus may generally be referred to as a lithography tool. The lithography tool may use vacuum conditions or ambient (non-vacuum) conditions.

Although the foregoing may specifically refer to the use of embodiments of the present invention in the context of optical lithography, it should be understood that the present invention is not limited to optical lithography and may be used in other applications (such as imprint lithography) where the context permits.

Where the context permits, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored on a machine-readable medium that can 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 that can be read 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; propagated signals in electrical, optical, acoustic, or other forms (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Additionally, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only and that such actions in fact result from a computing device, processor, controller, or other device that executes the firmware, software, routines, instructions, etc. and that, when performing such operations, enables an actuator or other device to interact with the physical world. Although specific embodiments of the present invention have been described above, it should be understood that the present invention may be practiced in other ways than those described. The above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that the present invention as described may be modified without departing from the scope of the claims set forth below. Other aspects of the invention are described in the following numbered clauses. 1. A reluctance actuator configured to apply a substantially upward force to an object that can be displaced in a horizontal direction by a mover of a positioning device, the reluctance actuator comprising: A first component configured to be connected to the object; A second component configured to be connected to the mover; The first component and the second component form a magnetic flux path, including a gap between the first component and the second component; A permanent magnet disposed in the magnetic flux path to generate a bias magnetic flux in the magnetic flux path, the bias magnetic flux generating a bias upward force on the first component; a coil configured to engage with the first member or the second member and configured to generate a variable magnetic flux in the magnetic flux path when energized, the variable magnetic flux generating a variable force on the first member; A first surface of the first member and a first surface of the second member facing each other across the gap are configured to maintain a magnetic flux resistance of the magnetic flux path substantially constant for a displacement of the first member relative to the second member in the horizontal direction at a predetermined distance D. 2.    A reluctance actuator as in clause 1, wherein the first member comprises a C-shaped core disposed in a substantially vertical plane and the second member comprises a C-shaped core disposed in a substantially horizontal plane. 3.    A magnetoresistive actuator as in clause 1, wherein the first component comprises a C-shaped core disposed in a substantially vertical plane, the second component comprises a C-shaped core disposed in the substantially vertical plane, the C-shaped core of the second component substantially enclosing the C-shaped core of the first component. 4.    A magnetoresistive actuator as in any of the preceding clauses, further comprising a connecting component having a bottom end connected to the first component and configured to be connected to a top end of the object, whereby the top end is disposed above a top surface of the second component during use. 5.    A magnetoresistive actuator as in clause 4, wherein the connecting component is a non-magnetic component. 6.    The magnetoresistive actuator of clause 1, wherein a width W1 of the first surface of the first component in the horizontal direction is less than a width W2 of the first surface of the second component in the horizontal direction. 7.    The magnetoresistive actuator of clause 6, wherein the width W1, the width W2 and the predetermined distance D satisfy: W2 - W1 = D. 8.    The magnetoresistive actuator of clause 6, wherein the width W1, the width W2 and the predetermined distance D satisfy: W2 - W1 ＞ D. 9.    The magnetoresistive actuator of clause 1, wherein a width W1 of the first surface of the first component in the horizontal direction is greater than a width W2 of the first surface of the second component in the horizontal direction. 10.  The magnetoresistive actuator of clause 9, wherein the width W1, the width W2 and the predetermined distance D satisfy: W1 - W2 =  D. 11.  The magnetoresistive actuator of clause 9, wherein the width W1, the width W2 and the predetermined distance D satisfy: W1 - W2 ＞  D. 12.  The magnetoresistive actuator of any of the preceding clauses, wherein the horizontal direction includes a first horizontal direction and a second horizontal direction, the second horizontal direction being perpendicular to the first horizontal direction. 13.  The magnetoresistive actuator of any of the preceding clauses, wherein the first surface of the first component and the first surface of the second component are substantially horizontal surfaces. 14.  A reluctance actuator as in any of the preceding clauses, further comprising a sensor, such as a Hall sensor, configured to measure a magnetic flux in the magnetic flux path. 15.  A reluctance actuator as in item 1, wherein the first component comprises a top plate and a bottom plate, the top plate being parallel to the bottom plate and separated by a holder; the second component is disposed between the top plate and the bottom plate and comprises: an inner magnetic cylinder; a radially magnetized permanent magnet disposed concentrically around the inner magnetic cylinder as the permanent magnet; a cylindrical coil disposed around the inner magnetic cylinder as the coil; an outer magnetic cylinder disposed concentrically around the radially magnetized permanent magnet; whereby the top surfaces of the inner magnetic cylinder and the outer magnetic cylinder are separated by a distance D1 from a bottom surface of the top plate, thereby forming a first gap of the gap; Thereby, the bottom surfaces of the inner magnetic cylinder and the outer magnetic cylinder are separated from a top surface of the bottom plate by a distance D2, thereby forming a second gap of the gap. 16. The magnetoresistive actuator of clause 15, wherein during use, the first gap is larger than the second gap to generate the biasing upward force. 17. The magnetoresistive actuator of clause 15 or 16, further comprising a sensor configured to measure a magnetic flux in the magnetic flux path, such as a Hall sensor. 18. The magnetoresistive actuator of clause 17, comprising a first set of Hall sensors configured on the top surface of the inner magnetic cylinder or the outer magnetic cylinder, and a second set of Hall sensors configured on the bottom surface of the inner magnetic cylinder or the outer magnetic cylinder. 19.  A reluctance actuator as in any of the preceding clauses, wherein the bias magnetic flux follows a first magnetic flux path of the magnetic flux path, and wherein the variable magnetic flux follows a second magnetic flux path of the magnetic flux path. 20. A positioning device for positioning an object table, the positioning device comprising: A linear or planar motor for positioning the object table over a relatively large distance, the linear or planar motor comprising: A stator; A mover configured to displace the object table relative to the stator; Wherein the positioning device further comprises one or more reluctance actuators as in any of the preceding clauses, whereby the first part of the one or more reluctance actuators is configured to be connected to the object table as the object, and whereby the second part of the one or more reluctance actuators is connected to the mover. 21. A storage table device, comprising an object table and a positioning device as in clause 20 for positioning the object table. 22.  A stage apparatus as in item 21, wherein the stage is configured to hold a patterned device or a substrate. 23.  A lithography apparatus, comprising the stage apparatus as in item 21 or 22. 24.  An exposure apparatus, comprising the stage apparatus as in item 21 or 22.

400: Reluctance actuator 410: First component 410.1: First surface 412: C-shaped core structure 414: Connecting component 414.1: Bottom end 414.2: Top end 420: Second component 420.1: Top surface/first surface 440: Magnetic flux path 450: Gap 460: Permanent magnet 470: Coil 700: Reluctance actuator 702: Object 710: First component 710.1: First surface 712: C-shaped core structure 714: Connecting component 720: Second component 720.1: First surface 740: Magnetic flux path Diameter 750: Gap 760: Permanent magnet 770: Coil 800: Reluctance actuator 802: Object 810: First component 812: Top plate 812.1: Bottom surface 814: Bottom plate 814.1: Top surface 816: Holder 820: Second component 822: Inner cylinder/inner magnetic cylinder 824: Radially magnetized permanent magnet 826: Cylindrical coil 828: Outer cylinder 840: Magnetic flux path 842: Magnetic flux path 900: Reluctance actuator 900': Variant/Reluctance actuator 910: First component 912: Circular plate 91 4: first connecting member 920: second member 922: magnetic member 922': magnetic member 924: permanent magnet 924': magnet 926: coil 928: second connecting member 940: magnetic flux path 950: gap 960: radial direction 1000: magnetoresistive actuator 1010: first member 1020: second member 1022: magnetic member 1024: permanent magnet 1026: coil 1040: magnetic flux path 1050: gap 1060: radial direction 1100: magnetoresistive actuator 1110: first member 111 1.1: Structure 1111.2: Structure 1120: Second component 1122: Magnetic component 1124: Permanent magnet 1126: Coil 1140: Magnetic flux path 1150.1: Gap 1150.2: Gap 1160: Radial direction B: Radiation beam BD: Beam delivery system BF: Base frame BM: Balance block C: Target part D: Distance D1: Distance D2: Distance D3: Diameter D4: Outer diameter FB: Feedback controller FF: Feedforward controller IL: Illumination system/illuminator IS: Vibration isolation system LA: Lithography equipment M ₁ : Mask alignment mark M ₂ : Mask alignment mark MA: Patterning device MF: Metrology frame MT: Mask support/mask stage P ₁ : Substrate alignment mark P ₂ : Substrate alignment mark PCS: Position control system PM: First positioner PMS: Position measurement system PS: Projection system PW: Second positioner SO: Radiation source SP: Set point generator W: Substrate W1: Width W2: Width W3: Width W4: Width WT: Substrate support/substrate stage/substrate structure

Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings, in which: - FIG. 1 depicts a schematic overview of a lithography apparatus; - FIG. 2 depicts a detailed view of a portion of the lithography apparatus of FIG. 1; - FIG. 3 schematically depicts a position control system; - FIG. 4 depicts a first embodiment of a magnetoresistive actuator according to the present invention; - FIG. 5(a) and FIG. 5(b) depict YZ views of the magnetoresistive actuator of FIG. 4; - FIG. 6(a) and FIG. 6(b) depict XZ views of the magnetoresistive actuator of FIG. 4; - FIG. 7 depicts a second embodiment of a magnetoresistive actuator according to the present invention; - FIG. 8 depicts a third embodiment of a magnetoresistive actuator according to the present invention; - Figures 9a and 9b illustrate the fourth and fifth embodiments of the magnetoresistive actuator according to the present invention; - Figure 10 illustrates the sixth embodiment of the magnetoresistive actuator according to the present invention; - Figure 11 illustrates the seventh embodiment of the magnetoresistive actuator according to the present invention.

400: Reluctance actuator

410: First component

412: C-shaped core structure

414: Connecting parts

414.1: Bottom

414.2: Top

420: Second part

420.1: Top surface/first surface

440: Magnetic flux path

450: Gap

460:Permanent magnet

470: Coil

Claims (15)

A reluctance actuator configured to apply a substantially upward force to an object that can be displaced in a horizontal direction by a mover of a positioning device, the reluctance actuator comprising: a first component configured to be connected to the object; a second component configured to be connected to the mover; the first component and the second component form a magnetic flux path including a gap between the first component and the second component; a permanent magnet disposed in the magnetic flux path to generate a bias magnetic flux in the magnetic flux path, the bias magnetic flux generating a bias upward force on the first component; A coil configured to engage with the first component or the second component and configured to generate a variable magnetic flux in the magnetic flux path when energized, the variable magnetic flux generating a variable force on the first component; A first surface of the first component and a first surface of the second component facing each other across the gap are configured to maintain a magnetic flux resistance of the magnetic flux path substantially constant for a displacement of the first component relative to the second component in the horizontal direction at a predetermined distance D. A magnetoresistive actuator as claimed in claim 1, wherein the first component comprises a C-shaped core arranged in a substantially vertical plane, and the second component comprises a C-shaped core arranged in a substantially horizontal plane. A magnetoresistive actuator as claimed in claim 1, wherein the first component includes a C-shaped core arranged in a substantially vertical plane, the second component includes a C-shaped core arranged in the substantially vertical plane, and the C-shaped core of the second component substantially encloses the C-shaped core of the first component. A magnetoresistive actuator as in any one of claims 1 to 3, further comprising a connecting component having a bottom end connected to the first component and configured to be connected to a top end of the object, whereby the top end is configured above a top surface of the second component during use. A magnetoresistive actuator as claimed in claim 1, wherein a width W1 of the first surface of the first component in the horizontal direction is smaller than a width W2 of the first surface of the second component in the horizontal direction. A magnetoresistive actuator as claimed in claim 1, wherein a width W1 of the first surface of the first component in the horizontal direction is greater than a width W2 of the first surface of the second component in the horizontal direction. A magnetoresistive actuator as claimed in any one of claims 1 to 3, wherein the horizontal direction includes a first horizontal direction and a second horizontal direction, the second horizontal direction being perpendicular to the first horizontal direction. A magnetoresistive actuator as claimed in any one of claims 1 to 3, wherein the first surface of the first component and the first surface of the second component are substantially horizontal surfaces. A reluctance actuator as in any one of claims 1 to 3, further comprising a sensor, such as a Hall sensor, configured to measure a magnetic flux in the flux path. A magnetoresistive actuator as claimed in claim 1, wherein the first component comprises a top plate and a bottom plate, the top plate being parallel to the bottom plate and separated by a holder; the second component is disposed between the top plate and the bottom plate and comprises: an inner magnetic cylinder; a radially magnetized permanent magnet disposed concentrically around the inner magnetic cylinder as the permanent magnet; a cylindrical coil disposed around the inner magnetic cylinder as the coil; an outer magnetic cylinder disposed concentrically around the radially magnetized permanent magnet; whereby the top surfaces of the inner magnetic cylinder and the outer magnetic cylinder are separated by a distance D1 from a bottom surface of the top plate, thereby forming a first gap of the gap; Thereby, the bottom surfaces of the inner magnetic cylinder and the outer magnetic cylinder are separated from a top surface of the bottom plate by a distance D2, thereby forming a second gap of the gap. A reluctance actuator as in any one of claims 1 to 3, wherein the bias flux follows a first flux path of the flux path, and wherein the variable flux follows a second flux path of the flux path. A positioning device for positioning an object stage, the positioning device comprising: A linear or planar motor for positioning the object stage over a relatively large distance, the linear or planar motor comprising: A stator; A mover configured to displace the object stage relative to the stator; Wherein the positioning device further comprises one or more reluctance actuators as in any of the preceding claims, whereby the first part of the one or more reluctance actuators is configured to be connected to the object stage as the object, and whereby the second part of the one or more reluctance actuators is connected to the mover. A storage table device comprises an object table and a positioning device as claimed in claim 12 for positioning the object table. A lithography device comprising a stage device as claimed in claim 13. An exposure device comprising a stage device as claimed in claim 13.