Method for determining electromagnetic motors and position-dependent motor constants of electromagnetic motors

Abstract

The present invention provides a method for determining the position-dependent motor constants of an electromagnetic motor comprising a magnet assembly and a coil assembly configured to be displaced relative to each other in the direction of motion, the method comprising: displacing the magnet assembly relative to the coil assembly along a predetermined trajectory of interest at a substantially constant speed in the direction of motion; applying a disturbance having a predetermined frequency to the electromagnetic motor during the displacement of the magnet assembly relative to the coil assembly; determining the position error of the magnet assembly relative to the coil assembly and the electromagnetic motor force along the predetermined trajectory of interest; and determining the position-dependent motor constants of the electromagnetic motor along the predetermined trajectory of interest based on the determined position error and electromagnetic motor force.

Description

[Technical Field]

[0001] (Cross-reference of related applications)

[0001] This application claims priority to EP application 23166250.3, filed on 31 March 2023, which is incorporated herein by reference in its entirety.

[0002]

[0002] The present invention relates to an electromagnetic motor, and more specifically to an electromagnetic motor applicable to a lithography apparatus, for example, to displace or position a patterning device or a substrate. [Background technology]

[0003]

[0003] A lithography apparatus is a machine built to apply a desired pattern onto a substrate. A lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithography apparatus may, for example, project a pattern (often called a "design layout" or "design") of a patterning device (e.g., a mask) onto a radiative-sensitive material (resist) layer provided on a substrate (e.g., a wafer).

[0004]

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continuously decreased, while the number of functional elements such as transistors per device has steadily increased over several decades, following a trend generally known as Moore's Law. To keep up with Moore's Law, the semiconductor industry is pursuing technologies that enable the creation of increasingly smaller features. To project patterns onto a substrate, lithography equipment sometimes uses electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be patterned on the 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 with wavelengths in the range of 4 nm to 20 nm, for example 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than lithography equipment using radiation with a wavelength of, for example, 193 nm.

[0005]

[0005] To form a pattern on a substrate using a patterning device, a scanning process is typically applied, which displaces both the patterning device and the substrate relative to the irradiated beam. Electromagnetic motors and actuators are typically used to enable this displacement. Precise control of the motors and actuators involved in positioning is crucial for accurately positioning the pattern of the patterning device on the substrate. Generally, for various reasons, the response of a known actuator or motor to a specific control signal can be somewhat uncertain. In particular, motor constants, which represent the force generated per unit current, are known to be non-constant across the displacement range of the motor or actuator. To predict this and improve the positioning of the motor or actuator, methods have been developed to determine motor constants. Known methods for determining motor constants have proven to be either quite time-consuming or have insufficient resolution. [Overview of the Initiative]

[0006]

[0006] An object of the present invention is to provide a method for determining the position-dependent motor constant of an electromagnetic motor that alleviates the aforementioned problems of at least known methods.

[0007]

[0007] According to one aspect of the present invention, an electromagnetic motor, A magnet assembly configured to generate a magnetic field, A coil assembly comprising at least one coil, wherein the coil assembly is configured to cooperate with the magnet assembly in order to move the magnet assembly relative to the coil assembly in a direction of motion, A power supply configured to provide power to the coil assembly during use, It is a control unit, To displace the magnet assembly relative to the coil assembly along a predetermined orbit of interest at a substantially constant speed, the power supply is controlled to supply current to the coil assembly. During the displacement of the magnet assembly relative to the coil assembly, a disturbance having a predetermined frequency is applied to the electromagnetic motor. The position of the magnet assembly relative to the coil assembly and the electromagnetic motor force are determined along a predetermined orbit of interest. A control unit configured to determine the position-dependent motor constants of an electromagnetic motor along a predetermined trajectory of interest, based on the determined position and electromagnetic motor force, An electromagnetic motor equipped with [a specific feature] is provided.

[0008]

[0008] In another embodiment, a stage device for use in a lithography apparatus is provided, the stage being equipped with an electromagnetic motor according to the present invention. The stage device may be configured, for example, to hold a patterning device or a substrate.

[0009]

[0009] In yet another embodiment, a lithography apparatus equipped with a stage device according to the present invention is provided.

[0010]

[0010] According to yet another aspect of the present invention, a method for determining the position-dependent motor constant of an electromagnetic motor comprising a magnet assembly and a coil assembly configured to be displaced relative to each other in the direction of movement, Displacing the magnet assembly relative to the coil assembly in a direction of movement along a predetermined trajectory of interest at a substantially constant speed, Applying a disturbance having a predetermined frequency to an electromagnetic motor during the displacement of the magnet assembly relative to the coil assembly, To determine the positional error of the magnet assembly relative to the coil assembly and the electromagnetic motor force along a predetermined orbit of interest, and Based on the determined position error and electromagnetic motor force, determine the position-dependent motor constants of the electromagnetic motor along a predetermined trajectory of interest. A method including this is provided. [Brief explanation of the drawing]

[0011]

[0011] Hereinafter, embodiments of the present invention will be described as merely one example with reference to the attached schematic diagram.

[0012] [Figure 1] This provides a general overview of lithography equipment. [Figure 2] Figure 1 shows a detailed view of a part of the lithography apparatus. [Figure 3] A schematic diagram of the position control system is shown. [Figure 4] The first electromagnetic motor according to the present invention is shown. [Figure 5] The second electromagnetic motor according to the present invention is shown. [Figure 6] The change in motor constants along the trajectory Y1-Y2 is schematically shown. [Figure 7] A schematic diagram of a position control system applicable to the present invention is shown. [Figure 8] A schematic flowchart of the method according to the present invention is shown below. [Figure 9] A schematic diagram of a position control system applicable to the present invention, including a position where disturbances can be inserted, is shown. [Figure 10] Schematically shows various methods for determining the amplitude of an alternating current signal.

Embodiments of the Invention

[0013]

[0012] As used herein, the terms "radiation" and "beam" are used to encompass any type of electromagnetic radiation, including ultraviolet light (e.g., having a wavelength of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultraviolet light, e.g., having a wavelength of about 5 - 100 nm).

[0014]

[0013] As used herein, the terms "reticle", "mask" or "patterning device" may be broadly construed to refer to a general patterning device that can be used to impart a patterned cross-section corresponding to a pattern to be created in a target portion of a substrate by an incident radiation beam. The term "light valve" can also be used in this context. In addition to standard masks (transmission or reflection, binary, phase shift, hybrid, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0015]

[0014] Figure 1 schematically shows a lithography apparatus LA. The lithography apparatus LA includes an illumination system (also called an illuminator) IL configured to adjust a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation), a mask support (e.g., a mask table) MT constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to precisely position the patterning device MA according to specific parameters, a substrate support (e.g., a wafer table) WT constructed to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to precisely position the substrate support according to specific parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project the pattern applied to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (e.g., including one or more dies).

[0016]

[0015] During operation, the illumination system IL receives the radiated beam from the radiation source SO, for example, via the beam delivery system BD. The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for inducing, shaping, and / or controlling the radiation. The illuminator IL may be used to adjust the radiated beam B in the plane of the patterning device MA so that the cross-section of the radiated beam B has a desired spatial and angular intensity distribution.

[0017]

[0016] As used herein, the term “projection system” PS should be interpreted broadly to encompass a variety of projection systems, including refractive optical systems, reflective optical systems, reflective refractive optical systems, anamorphic optical systems, magneto-optical systems, electromagnetic optical systems, and / or electrostatic optical systems, or any combination thereof, as appropriate in accordance with the exposure radiation used and / or other factors such as the use of immersion liquid or vacuum. Any use of the term “projection lens” herein may be considered synonymous with the more general term “projection system” PS.

[0018]

[0017] The lithography apparatus LA may be of a type in which at least a portion of the substrate can be covered with a liquid having a relatively high refractive index, such as water, to fill the space between the projection system PS and the substrate W, and is also called immersion lithography. More information relating to immersion technology is given in US6952253, which is incorporated herein by reference.

[0019]

[0018] The lithography apparatus LA may also be of the type having two or more substrate support WTs (also called a “dual stage”). In such a “multistage” machine, the substrate support WTs may be used in parallel, and / or the preparation steps for subsequent exposure of substrate W may be performed on substrate W located on one substrate support WT, while another substrate W on the other substrate support WT is used to expose a pattern on the other substrate W.

[0020]

[0019] In addition to the substrate support WT, the lithography apparatus LA may include a measurement stage. The measurement stage is configured to hold sensors and / or cleaning devices. The sensors may be configured to measure the characteristics of the projection system PS or the characteristics of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning devices may be configured to clean parts of the lithography apparatus, such as parts of the projection system PS or parts of the system that provides the immersion fluid. The measurement stage may move below the projection system PS when the substrate support WT is away from the projection system PS.

[0021]

[0020] During operation, the radiating beam B is incident on a patterning device, such as a mask MA, held on a mask support MT, and is patterned by the pattern (design layout) present on the patterning device MA. The radiating beam B, having crossed the patterning device MA, passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. A second positioner PW and a position measuring system IF can be used to precisely move the substrate support WT to position various target portions C at focused and aligned positions within the path of the radiating beam B, for example. Similarly, a first positioner PM and, optionally, another position sensor (not explicitly shown in Figure 1) may be used to precisely position the patterning device MA relative to the path of the radiating beam B. The patterning device MA and the substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. The illustrated substrate alignment marks P1, P2 occupy dedicated target portions but may be located in the space between target portions. When substrate alignment marks P1 and P2 are located between target portions C, they are known as scribe line alignment marks.

[0022]

[0021] To clarify the present invention, the Cartesian coordinate system is used. The Cartesian coordinate system has three axes, namely the x-axis, y-axis, and 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 a Ry rotation. A rotation about the z-axis is called an Rz rotation. The x-axis and y-axis define the horizontal plane, with the z-axis perpendicular to it. The Cartesian coordinate system is not limiting to the present invention, but is used merely for clarity. Alternatively, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the present invention. The orientation of the Cartesian coordinate system may differ, for example, such that the z-axis has a component along the horizontal plane.

[0023]

[0022] Figure 2 shows a more detailed view of a part of the lithography apparatus LA of Figure 1. The lithography apparatus LA may include a base frame BF, a balance mass BM, a metronome frame MF, and a vibration isolation system IS. The metronome frame MF supports the projection system PS. The metronome frame MF may also support a part of the position measurement system PMS of Figure 1. The metronome frame MF is supported by the base frame BF via the vibration isolation system IS. The vibration isolation system IS is configured to prevent or reduce the propagation of vibrations from the base frame BF to the metronome frame MF.

[0024]

[0023] The second positioner PW is configured to accelerate the substrate support WT by providing a driving force between the substrate support WT and the balance mass BM. The driving force accelerates the substrate support WT in the desired direction. Due to the conservation of momentum, the driving force is also applied to the balance mass BM with the same magnitude, but in the opposite direction to the desired direction. Typically, the mass of the balance mass BM is significantly larger than the mass of the movable part of the second positioner PW and the substrate support WT.

[0025]

[0024] In one embodiment, the second positioner PW is supported by a balance mass BM. For example, the second positioner PW includes a planar motor for levitating the substrate support WT above the balance mass 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 a bearing, such as a gas bearing, for levitating the substrate support WT above the base frame BF.

[0026]

[0025] The position measurement system PMS may include any type of sensor suitable for determining the position of the substrate support WT. The position measurement system PMS may include 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 encoder. The position measurement system PMS may include a combined system of an interferometer and an encoder. The sensor may be another type of sensor such as a magnetic sensor, a capacitive sensor or an inductive sensor. The position measurement system PMS may determine the position relative to a reference, for example, 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 mask support MT by measuring the position or by measuring the time derivative of the position, such as velocity or acceleration.

[0027]

[0026] A position measurement system (PMS) may include an encoder system. As an encoder system, for example, U.S. Patent Application US2007 / 0058173A1, filed on September 7, 2006, is known and is incorporated herein by reference. The encoder system comprises an encoder head, a diffraction grating, and a sensor. The encoder system may receive a primary radiation beam and a secondary radiation beam. Both the primary and secondary radiation beams originate from the same radiation beam, i.e., the original radiation beam. At least one of the primary and secondary radiation beams is created by diffracting the original radiation beam with a diffraction grating. When both the primary and secondary radiation beams are created by diffracting the original radiation beam with a diffraction grating, the primary radiation beam must have a different diffraction order than the secondary radiation beam. Different diffraction orders are, for example, +1st order, -1st order, +2nd order, and -2nd order. The encoder system optically couples the primary and secondary radiation beams to form a combined radiation beam. A sensor in the encoder head determines the phase or phase difference of the combined radiation beam. The sensor generates a signal based on phase or phase difference. The signal represents the position of the encoder head relative to the diffraction grating. One of the encoder head and the diffraction grating may be located on a substrate structure WT. The other of the encoder head and the diffraction grating may be located on a metrology frame MF or a base frame BF. For example, multiple encoder heads may be located on a metrology frame MF, while the diffraction grating is located on the top surface of the substrate support WT. In another example, the diffraction grating may be located on the bottom surface of the substrate support WT, and the encoder head may be located below the substrate support WT.

[0028]

[0027] The position measurement system (PMS) may include an interferometer system. An interferometer system is known, for example, U.S. Patent US6,020,964, filed on July 13, 1998, which is incorporated herein by reference. The interferometer system may include a beam splitter, mirrors, a reference mirror, and a sensor. The beam of radiation is split by the beam splitter into a reference beam and a measurement beam. The measurement beam propagates to the mirror, is reflected by the mirror and returns to the beam splitter. The reference beam propagates to the reference mirror, is reflected by the reference mirror and returns to the beam splitter. At the beam splitter, the measurement beam and the reference beam are combined to form a combined radiation beam. The combined radiation beam is incident on a sensor. The sensor determines the phase or frequency of the combined radiation beam. The sensor generates a signal based on the phase or frequency. The signal represents the displacement of the mirror. In some embodiments, the mirror is connected to a substrate support WT. The reference mirror may be connected to a metrology frame MF. In one embodiment, the measurement beam and the reference beam are coupled to a combined radiation beam by an additional optical component rather than a beam splitter.

[0029]

[0028] 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 precision over a narrow range of movement relative to the long-stroke module. The long-stroke module is configured to move the short-stroke module with relatively low precision over a wide range of movement relative to the projection system PS. The combination of the long-stroke module and the short-stroke module allows the first positioner PM to move the mask support MT with high precision over a wide range of movement relative to the projection system PS. 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 precision over a narrow range of movement relative to the long-stroke module. The long-stroke module is configured to move the short-stroke module with relatively low precision over a wide range of movement relative to the projection system PS. The combination of the long-stroke module and the short-stroke module allows the second positioner PW to move the substrate support WT with high precision over a wide range of movement relative to the projection system PS.

[0030]

[0029] The first positioner PM and the second positioner PW are each provided with an electromagnetic motor for moving the mask support MT and the substrate support WT, respectively. The electromagnetic motor may be a linear motor for providing driving force along a single axis, for example, the Y-axis. Multiple linear motors may be applied to provide driving force along multiple axes. The motor may be a planar motor for providing driving force along multiple axes. For example, a planar motor may be configured to move the substrate support WT with 6 degrees of freedom. The electromagnetic motor may be an electromagnetic actuator having at least one coil and at least one magnet. The actuator is configured to move at least one coil relative to at least one magnet by applying current to at least one coil. The actuator may be a movable magnet type actuator having at least one magnet coupled to the substrate support WT and the mask support MT, respectively. The actuator may be a movable coil type actuator having at least one coil coupled to the substrate support WT and the mask support MT, respectively. The electromagnetic actuator may be a voice coil actuator, a reluctance actuator, a Lorentz actuator, a piezo actuator, or any other suitable actuator.

[0031]

[0030] The lithography apparatus LA includes a position control system PCS, as schematically shown in Figure 3. The position control system PCS includes a setpoint generator SP, a feedforward controller FF, and a feedback controller FB. The position control system PCS supplies a drive signal to the plant / motor combination P-EM. The plant / motor combination includes an electromagnetic motor EM, which may be the motor of a first positioner PM or a second positioner PW. The motor EM of the plant / motor combination P-EM drives the plant P, which may include a substrate support WT or a mask support MT. The plant P is sometimes called a motor-driven load. The output of the plant / motor combination P-EM is a position quantity such as the position, velocity, or acceleration of the plant. The position quantity is measured by a position measuring system PMS. The position measuring system PMS generates a signal, which is a position signal representing the position quantity of the plant P. The setpoint generator SP generates a signal, which is a reference signal representing a desired position quantity of the plant P. For example, the reference signal represents a desired trajectory of the substrate support WT. The difference between the reference signal and the position signal constitutes the input to the feedback controller FB. Based on this input, the feedback controller FB supplies at least a portion of the drive signal to the electromagnetic motor EM of the plant / motor combination P-EM. The reference signal may constitute the input to the feedforward controller FF. Based on this input, the feedforward controller FF supplies at least a portion of the drive signal to the motor EM of the plant / motor combination. The feedforward FF may utilize information regarding the dynamic characteristics of the plant P, such as its mass, stiffness, resonant mode, and natural frequency.

[0032]

[0031] The present invention aims to improve the performance of an electromagnetic motor or actuator applied to a lithography apparatus, for example, a motor applied to the long-stroke module or short-stroke module described above.

[0033]

[0032] Figure 4 schematically shows a first example of an electromagnetic motor 400 according to the present invention. In the embodiment shown in the figure, the electromagnetic motor 400 comprises a magnet assembly 410 and a coil assembly 420. The magnet assembly 410 shown in the figure comprises two magnetic yokes 410.1 on which permanent magnets 410.2 are provided. The coil assembly 420 shown in the figure comprises a single coil capable of conducting current in a direction perpendicular to the plane of the drawing. When such current is supplied, a force is generated between the magnet assembly 410 and the coil assembly 420, and this force acts in the X direction shown in the figure. The force can move the coil assembly 410 in a direction relative to the magnet assembly 420, and this direction is therefore also called the direction of movement of the electromagnetic actuator 400. Generally, the coil assembly 420 may have multiple coils.

[0034]

[0033] According to the present invention, the electromagnetic motor 400 further comprises a power supply 430 for supplying power to a coil assembly. The power supply 430 may be configured to supply, for example, a current shown by the dotted line 430.1 to the coil(s) of the coil assembly 410 of the electromagnetic motor 400. The electromagnetic motor 400 further comprises a control unit 440 configured to control the power supply 430 of the electromagnetic motor 400. In particular, according to the present invention, the control unit is configured to control the electromagnetic motor in a particular manner in order to determine the position-dependent motor constants of the electromagnetic motor along a trajectory of interest in the direction of movement. The trajectory of interest may correspond to, for example, a constant stroke of the electromagnetic motor as shown in the figure.

[0035]

[0034] In one embodiment, the control unit for the electromagnetic motor according to the present invention may include a position control system as shown in Figure 3. Generally, the control unit 440 for the electromagnetic motor according to the present invention may be configured to receive one or more input signals, such as position measurement signals and setpoint signals, and may also be configured to output one or more control signals for controlling the electromagnetic motor. In order to determine the position-dependent motor constants, the control unit 440 for the electromagnetic motor according to the present invention is configured to perform the following operations.

[0036]

[0035] In the first step, the control unit 440 of the electromagnetic motor 400 is configured to supply current to the coil assembly 410 so as to control the power supply 430 as indicated by the control signal 440.1, displacing the magnet assembly relative to the coil assembly at a substantially constant speed in the direction of movement along a predetermined trajectory of interest. To this end, the control unit 440 may be configured to generate position setpoints necessary to achieve the displacement. Thus, the control unit 440 may include a setpoint generator similar to the setpoint generator SP described above. Alternatively, the control unit 440 may receive a setpoint signal 440.2 from an external setpoint generator.

[0037]

[0036] In the second step, the control unit 440 is configured to apply a disturbance having a predetermined frequency to the electromagnetic motor 400 during the displacement of the magnet assembly relative to the coil assembly. There are various ways to apply a disturbance to the electromagnetic motor, as will be described in more detail below, such as injecting a disturbance force into the control scheme applied by the control unit or applying an actual disturbance force to the electromagnetic actuator.

[0038]

[0037] In the third step, the control unit 440 is configured to determine the position of the magnet assembly relative to the coil assembly and the electromagnetic motor force along the trajectory of interest. In one embodiment, the control unit 440 may be connected to a position measuring system such as the System PMS shown in Figure 3, which may be configured to measure the positions of the coil assembly 420 and / or the magnet assembly 410 in order to obtain position measuring signals for the coil assembly and / or the magnet assembly.

[0039]

[0038] In the fourth step, the control unit is configured to determine the position-dependent motor constants of the electromagnetic motor along a predetermined trajectory of interest, based on the determined position and electromagnetic motor force.

[0040]

[0039] As a result, the motor constants of the electromagnetic motor along a predetermined trajectory of interest are obtained. Subsequently, when these position-dependent motor constants are implemented in the control unit of the electromagnetic motor, more accurate position control of the load driven by the motor can be obtained.

[0041]

[0040] The exemplary electromagnetic motor 400 shown in Figure 4 may also be called an electromagnetic actuator, linear actuator, or Lorentz actuator. Such electromagnetic motors or actuators typically have a relatively small stroke. When it is necessary to displace a load or plant over a relatively long distance, for example, an electromagnetic motor can be used that has a coil assembly with a coil array and a magnet assembly with a magnet array.

[0042]

[0041] Figure 5 schematically shows an electromagnetic motor 500 according to the present invention that allows for relatively large displacement of the coil assembly relative to the magnet assembly. Figure 5(a) schematically shows a cross-section of the motor 500 showing a magnet assembly 510 having an array of magnets 510.1, such as permanent magnets, positioned on a magnetic yoke 510.2, such as a ferromagnetic yoke. The motor 500 further includes a coil assembly 520 having an array of coils 520.2 positioned in the Y direction shown in the figure and mounted on a holder 520.1. In the configuration shown in the figure, the array of magnets 510.1 is configured to generate a spatially alternating magnetic field along the Y direction shown in the figure, which may also be called the direction of movement, during use. This is because, during use, when the array of coils 520.2 of the coil assembly 520 is supplied with an appropriate set of current, the movement of the coil assembly 520 relative to the magnet assembly 510 can be established. As discussed with respect to Figure 4, the electromagnetic motor 500 further includes a power supply and control unit for supplying power to and controlling the coil assembly 520 of the electromagnetic motor 500. These components are not shown in Figure 5. Figures 5(b) and 5(c) schematically show the electromagnetic motor 500 at two different positions of the coil assembly 520 relative to the motor's magnet assembly 510. In Figure 5(b), the coil assembly 520 is at its leftmost position relative to the magnet assembly 510 along the direction of movement, while in Figure 5(c), the coil assembly 520 is at its rightmost position relative to the magnet assembly 510 along the direction of movement. Therefore, the range or stroke Y1-Y2 can be considered a trajectory of interest in the effective operating range or direction of movement of the motor. Note that positioning the coil assembly beyond the range Y1-Y2 relative to the magnet assembly reduces the interaction between the coil assembly and the magnet assembly, resulting in a significant decrease in the motor constant, i.e., the amount of force generated per unit current supplied to the coil assembly.

[0043]

[0042] As a mere example, Figure 6 schematically shows the motor constant K as a function of the relative position (Y) between the coil assembly and the magnet assembly of a motor such as the electromagnetic motor 500. Note that the motor constant K(y) may vary between the values ​​Kmin and Kmax along the range Y1-Y2, which may be a range similar to that shown in Figure 5. In general, there may be various causes for the perceived change in the motor constant, such as the magnet assembly, the magnets applied, the coils of the coil array, and the manufacturing tolerances of the coil assembly. The perceived change in the motor constant will also usually include a periodic component, which may be related to, for example, the magnet pitch of the magnet array in the motor's magnet assembly.

[0044]

[0043] The method for obtaining position-dependent motor constants according to the present invention will be described in more detail with reference to Figures 7 and 8.

[0045]

[0044] Figure 7 schematically shows a more detailed position control scheme that can be applied to control an electromagnetic motor according to the present invention, for example, to control a stage device of a lithography apparatus. This control scheme, specifically the position control scheme PCS, can be implemented, for example, in a control unit for an electromagnetic motor according to the present invention. The control scheme shown in Figure 7 is the same as the control scheme in Figure 3, except for the following points. In the control scheme in Figure 7, the plant motor combination P-EM(y) is further described and it is shown that the electromagnetic motor applied to the plant motor combination may have a position-dependent motor constant, i.e., a motor constant that depends on the y position of the plant motor combination. From a control point of view, the plant motor combination can be considered as a system or component that converts force into acceleration, which causes displacement along the direction of movement. In such a case, the plant motor combination has a singular nominal motor constant Km nomIt can be characterized by the following: Due to the aforementioned effects, the actual motor constant is not constant but a function of position y in the direction of movement. This is shown as Km(y) in the detailed plant / motor combination P-EM in Figure 7. Therefore, the output of block Km(y) in Figure 7 represents the actual force generated by the motor and is used to accelerate a load represented by mass m. Thus, the output of block P-EM(y) corresponds to the displacement y of the driven plant or load.

[0046]

[0045] The output of the position control system PCS corresponds to the drive signal of the P-EM(y) combination, as described above. In the PCS system shown in the figure, the drive signal is a combination of the outputs of the feedforward controller FF and the feedback controller FB. Typically, the drive signal indicated by reference no. 710 would be considered the desired drive force or desired motor force to drive the plant to the desired position indicated by the setpoint generator. Position-dependent motor constant K m Considering (y), this drive signal does not produce the desired acceleration or displacement of the plant. If the position-dependent motor constant Km(y) is known in advance, a correction may be applied to the drive signal to obtain the desired control of the plant. In Figure 7, the correction is K rcp (y) is denoted as such and is a position-dependent correction or adjustment that can be applied to the generated drive signal 710. As a result of this correction or adjustment, an adjusted drive signal 720 that takes into account the position-dependent motor constant Km(y) can be obtained. In this invention, the position-dependent motor constant K m (y), and consequently, any necessary modifications or adjustments K to account for positional dependence. rcp A method for determining (y) is disclosed. This method for determining position-dependent motor constants, which can also be considered a type of electromagnetic motor calibration method, is schematically shown in the flowchart of Figure 8.

[0047]

[0046] The method for determining position-dependent motor constants according to the present invention, shown in Figure 8, includes a first step 810 of displacing the magnet assembly of an electromagnetic motor at a substantially constant speed in the direction of movement along a predetermined trajectory of interest relative to the coil assembly of the electromagnetic motor. In some embodiments, the first step can be actually carried out by, for example, a control unit of the electromagnetic motor, which is configured to control the power supply of the electromagnetic motor, as described above with reference to Figure 4, for example. The trajectory of interest may be, for example, the range of motion of the electromagnetic motor, for example, the range Y1-Y2 shown in Figures 5 and 6.

[0048]

[0047] The method for determining position-dependent motor constants according to the present invention further includes a second step 820 of applying a disturbance having a predetermined frequency that exposes the mass behavior of the plant to the electromagnetic motor during the displacement of the magnet assembly relative to the coil assembly. In other words, the frequency of the disturbance is such that the mass behavior of the plant or load has a slope of magnitude -2, i.e., 1 / ms 2 It should be within the range indicated. Various methods for implementing such disturbances are described in detail below.

[0049]

[0048] The method for determining position-dependent motor constants according to the present invention further includes a third step 830 of determining the position of the magnet assembly relative to the coil assembly and the electromagnetic motor force along a predetermined trajectory of interest. Referring to the control scheme of Figure 7, for example, the position of the magnet assembly relative to the coil assembly may be determined using a position measurement system such as the PMS system shown in the figure.

[0050]

[0049] The method for determining position-dependent motor constants according to the present invention further includes a fourth step 840 of determining position-dependent motor constants of an electromagnetic motor along a predetermined trajectory of interest based on the determined position error and electromagnetic motor force. Referring to the control scheme of Figure 7, in one embodiment of the present invention, the electromagnetic motor force may be equal to a drive signal 710 generated by a position control system PCS.

[0051]

[0050] The following methods can be applied to carry out step 820 of the method according to the present invention.

[0052]

[0051] In the first embodiment, the disturbance described in step 820 of the method for determining position-dependent motor constants according to the present invention can be implemented in a position control system or control unit applied to control an electromagnetic motor for which motor constants are to be determined. This is shown in Figure 9. Figure 9 shows the position-dependent correction or adjustment K that needs to be determined. rcp Aside from (y), the position control method is schematically similar to that shown in Figure 7.

[0053]

[0052] As a first example, the disturbance in step 820 of the method according to the present invention can be injected into or superimposed on the drive signal generated by the position control system PCS. In Figure 9, this is indicated by arrow 910. In the embodiment shown in the figure, the drive signal, i.e., the combination of the outputs of the feedforward controller FF and the feedback controller FB representing the desired drive force or desired motor force, is combined with the disturbance indicated by arrow 910. Thus, in this example, the disturbance can be considered as a disturbance force or force component added to the drive signal output by the PCS. Such a disturbance force will henceforth be denoted as disturbance force F_dist(y).

[0054]

[0053] As a second example, the disturbance in step 820 of the method according to the present invention can be injected into or superimposed on the setpoint used by the PCS. In Figure 9, the setpoint generator SP may be configured to generate a setpoint for performing a displacement along a predetermined trajectory of interest as described in step 810 of the method according to the present invention. Thus, the disturbance indicated by arrow 920 is applied to the setpoint. Thus, in this example, the disturbance can be considered a positional disturbance applied to the setpoint.

[0055]

[0054] As a third example, the disturbance in step 820 of the method according to the present invention can be injected or superimposed on the position error determined by the PCS. In Figure 9, the position error is obtained by the difference between the setpoint of the setpoint generator SP and the y position determined by the position measurement system PMS. The position error is input to the feedback controller FB. The disturbance indicated by arrow 930 may be injected or superimposed on the position error. Thus, in this example, the disturbance can be considered as a position disturbance added to the position error. The position error will henceforth be denoted as e(y).

[0056]

[0055] In a second embodiment, the disturbance in step 820 of the method according to the present invention may be carried out as an actual disturbance force applied to the electromagnetic motor being calibrated. This can be done, for example, by applying a disturbance force to either the stator or the movable part of the electromagnetic motor when both are displaceable. If the stator is mounted on a rigid structure, the disturbance force may be applied to the movable part. In connection with a lithography apparatus, an electromagnetic motor such as the motor shown in Figure 5 may be applied to a long-stroke module, for example, as discussed above. Such a long-stroke module may also include a short-stroke module with one or more actuators configured to position an object table, for example. In one embodiment, one or more actuators of the short-stroke module may be used to generate a disturbance force on the electromagnetic motor of the long-stroke module.

[0057]

[0056] In one embodiment of the present invention, the disturbance to be applied is a substantially sinusoidal disturbance having a predetermined frequency.

[0058]

[0057] The method for determining position-dependent motor constants according to the present invention, specifically step 840 of the method, can be carried out as follows.

[0059] As shown in FIG. 9, an electromagnetic motor used to drive a plant or an object such as an object table is K m will have a position-dependent motor constant that can be described by K(y). Alternatively, Km(y) may be expressed as follows.

[0060]

Number

[0061]

[0059] In order to compensate for the position-dependent effect of the motor constant, the correction Krcp(y) needs to be as follows.

[0062]

Number

[0063] where c is a constant. Therefore, [1 + k(y)] or K m (y) is known and K rcp (y) can be easily derived. Apart from a constant gain, by determining the transfer function P-EM(y) shown in FIGS. 7 and 9, the position-dependent motor constant, and thus the compensation amount, can also be determined.

[0064]

[0060] According to the method of the present invention, this is done as follows: An electromagnetic motor is displaced along a predetermined trajectory of interest at a substantially constant speed in order to determine position-dependent motor constants. During the displacement, a disturbance having a predetermined frequency, for example, a sinusoidally changing disturbance, is applied to the motor. Various characteristics can be tracked during the displacement. Specifically, the position of the magnet assembly relative to the coil assembly and the electromagnetic motor force F_act(y) can be tracked as a function of displacement, i.e., along the trajectory of interest. Other variables that can be tracked during the displacement along the trajectory of interest are the position error e and the applied disturbance, for example, the disturbance force F_dist(y). Depending on the nature of the applied disturbance, the electromagnetic motor force, error e, and disturbance force are AC signals or traces. Only the amplitudes of the tracked variables are needed to determine the transfer function P-EM(y).

[0065]

[0061] Using this tracking data, the transfer function P-EM(y) may be determined as follows: The transfer function P-EM(y) is determined based on the process sensitivity PS(y) and the process sensitivity S(y). Specifically,

[0066]

number

[0067] Here,

[0068]

number

[0069] This is the amplitude of the position error e along a predetermined trajectory.

number

[0070] This is the amplitude of the disturbance force applied during the displacement along a predetermined trajectory.

number

[0071] This is the amplitude of the actuator force applied during displacement along a predetermined trajectory.

[0072]

number

[0073] Considering equation (5), the transfer function P-EM(y), and by extension the position-dependent motor constant given by equation (1), for example, is determined by the position error e and the actuator force.

number

[0074] It can be derived from this.

[0075]

[0062] Note that the position error e can be easily obtained as the difference between the actual position y measured by the PMS system shown in Figures 7 and 9 and the set point obtained from the set point generator SP.

[0076]

[0063] Furthermore, as described above, electromagnetic motor force

[0077]

number

[0078] It should be noted that this can be equal to the drive signal 710 generated by the position control system PCS shown in Figures 7 and 9.

[0079]

[0064] As shown above, position errors, disturbance forces, and electromagnetic motor forces are typically AC signals. The amplitude of such signals can be determined, for example, using a fitting algorithm or a similar method. Such a method is schematically illustrated with reference to Figure 10.

[0080]

[0065] Figure 10 schematically shows signals S that may correspond to, for example, the actual position y, position error e, disturbance force, or electromagnetic motor force along the trajectory of interest. It is assumed that the displacement along the trajectory of interest is a displacement at substantially a constant rate, and the illustrated signals S also correspond to signals obtained over time, i.e., during a displacement at a constant rate.

[0081]

[0066] A first method for deriving the amplitude of signal S is to fit the signal to a sinusoidal signal that spans one or more periods of signal S. The period of signal S is known because it corresponds to the period of a disturbance force having a predetermined frequency. In Figure 10, the window 1000 spans three periods of signal S. To determine the amplitude of signal S in the window, signal S can be fitted to a sinusoidal signal M(y) that spans the same period as window 1000.

[0082]

[0067] The signal M(y) can be considered as a sinusoidal signal with unknown amplitude and phase, and optionally unknown offset and slope. Therefore, the general formula for M(y) is as follows:

[0083]

number

[0084]

[0068] Parameters A1 to A4 can be obtained using known fitting techniques, such as least-squares fitting, so that A1 can be considered to correspond to the amplitude of signal S in window 1000. This process can be repeated for adjacent windows until the amplitude of signal S over the desired trajectory of interest is obtained. Note that the first method described above will yield one value for the amplitude of signal S in window 1000. To obtain a higher density or more detailed dataset of the amplitude of signal S, window 1000 can be made narrower, for example, to only one period. Alternatively or additionally, the series of windows applied may overlap.

[0085]

[0069] A second method for obtaining the amplitude of signal S is to determine the maximum and minimum values ​​of signal S. For a portion of signal S, these maximum and minimum values ​​are shown as MAX and MIN in Figure 10, respectively. To obtain the amplitude of signal S, we can consider a polynomial that passes through the maximum and minimum values ​​and obtain the polynomials Pmax and Pmin. Then, by subtracting Pmin from Pmax, we can obtain the amplitude of signal S.

[0086]

[0070] A third method for obtaining the amplitude of signal S can be considered a simplified version of the second method, and is shown on the right side of Figure 10. To obtain the amplitude value of signal S, a straight line L is drawn between two adjacent maximum values ​​of the signal. The amplitude of signal S at the minimum value between two adjacent maximum values ​​can be interpreted as the distance D between the minimum value and the straight line L.

[0087]

[0071] Regardless of the method applied, it can be noted that it is preferable to select disturbance frequencies that are sufficiently high and / or substantially constant displacement speeds that are sufficiently low so that the available amplitude data are sufficient to accurately evaluate the changes in the motor constants of the electromagnetic motor. In this regard, it is desirable to ensure that at least five data points are available within the magnet pitch of the electromagnetic motor.

[0088]

[0072] Once the required signal amplitude is obtained, the transfer function P-EM(y) and correction K are obtained. rcp (y) can be determined. Correction K rcp When (y) is subsequently implemented in an electromagnetic motor position control system or control unit, more precise positioning or displacement of the load or plant driven by the motor can be obtained.

[0089]

[0073] As described above, the electromagnetic motor according to the present invention may be advantageously applied to drive the stage of a lithography apparatus. As will be understood by those skilled in the art, the electromagnetic motor according to the present invention may also be applied to drive other components in a lithography apparatus, such as a reticle masking device. Advantageously, the electromagnetic motor according to the present invention may also be applied outside the field of lithography.

[0090]

[0074] Although this text specifically refers to the use of lithography equipment in the manufacture of ICs, it should be understood that the lithography equipment described herein has other applications. Other possible applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, and the like.

[0091]

[0075] Although the text specifically refers to embodiments of the present invention in relation to lithography apparatus, embodiments of the present invention may be used in other apparatuses. Embodiments of the present invention may constitute part of a mask inspection apparatus, a metrology apparatus, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses are sometimes commonly referred to as lithography tools. Such lithography tools may operate under vacuum conditions or ambient (non-vacuum) conditions.

[0092]

[0076] While the above has specifically referred to the use of embodiments of the present invention in relation to photolithography, it will be understood that, where the context allows, the present invention is not limited to photolithography and may be used in other applications, such as imprint lithography.

[0093]

[0077] Where permitted by context, 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 in 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 readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM), random access memory (RAM), magnetic storage media, optical storage media, flash memory devices, propagating signals of electrical, optical, acoustic or other forms (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Furthermore, firmware, software, routines, and instructions may be described herein as performing specific actions. However, such descriptions are merely for convenience, and it should be understood that such actions actually originate from a computing device, processor, controller, or other device that performs the firmware, software, routines, instructions, etc., and that in performing them, actuators or other devices may interact with the material world.

[0094]

[0078] Although specific embodiments of the present invention have been described above, it will be understood that the present invention can be practiced in ways other than those described. The above description is illustrative and not limiting. Accordingly, it will be obvious to those skilled in the art that modifications to the above invention can be made without departing from the following claims. Other aspects of the present invention are described in the following numbered clauses. 1. An electromagnetic motor, A magnet assembly configured to generate a magnetic field, A coil assembly comprising at least one coil, wherein the coil assembly is configured to cooperate with the magnet assembly in order to move the magnet assembly relative to the coil assembly in a direction of motion, A power supply configured to provide power to the coil assembly during use, It is a control unit, To displace the magnet assembly relative to the coil assembly along a predetermined orbit of interest at a substantially constant speed, the power supply is controlled to supply current to the coil assembly. During the displacement of the magnet assembly relative to the coil assembly, a disturbance having a predetermined frequency is applied to the electromagnetic motor. The position of the magnet assembly relative to the coil assembly and the electromagnetic motor force are determined along a predetermined orbit of interest. A control unit configured to determine the position-dependent motor constant of an electromagnetic motor along a predetermined trajectory of interest, based on the determined position and electromagnetic motor force, An electromagnetic motor equipped with [a specific feature]. 2. The electromagnetic motor according to Clause 1, wherein the magnet assembly comprises a magnet array for generating a spatially alternating magnetic field in the direction of movement during use, and the coil assembly comprises a coil array arranged in the direction of movement. 3. An electromagnetic motor as described in Clause 1 or 2, wherein the disturbance is substantially sinusoidal. 4. An electromagnetic motor according to any one of clauses 1 to 3, wherein the control unit is configured to receive or generate position setpoints that cause displacement by the electromagnetic motor and to receive position signals representing the position of the electromagnetic motor. 5. The electromagnetic motor according to Clause 4, wherein the control unit is configured to determine a position error along a trajectory of interest based on a position signal and a position setpoint, and to determine a position-dependent motor constant of the electromagnetic motor along a predetermined trajectory of interest based on the determined position error and the electromagnetic motor force. 6. An electromagnetic motor according to Clause 4 or 5, wherein the control unit is configured to determine a desired motor force during displacement based on a position setpoint and a position signal. 7. An electromagnetic motor as described in Clause 6, wherein the disturbance is a disturbance force, and the control unit is configured to superimpose the disturbance force onto the desired motor force. 8. An electromagnetic motor according to any one of clauses 4 to 7, wherein the disturbance is a position disturbance, and the control unit is configured to superimpose the position disturbance on a position setpoint, or the difference between the position setpoint and a position signal. 9. An electromagnetic motor according to any one of the clauses 4 to 7, wherein the electromagnetic motor further comprises an actuator, and a control unit is configured to control the operation of the actuator to cause a disturbance. 10. An electromagnetic motor according to any one of the clauses 1 to 9, wherein determining the position of the magnet assembly relative to the coil assembly and the electromagnetic motor force includes determining the position and amplitude of the electromagnetic motor force along a predetermined trajectory of interest. 11. An electromagnetic motor according to any of the clauses 1 to 9, citing Clause 2, wherein a predetermined frequency and substantially constant speed are selected such that there are multiple periods of disturbance between the displacement of the magnet assembly relative to the coil assembly over the magnet pitch of the magnet array. 12. A stage device used in a lithography apparatus, comprising an electromagnetic motor as described in any of the clauses 1 to 11. 13. The stage apparatus according to Clause 12, wherein the stage is configured to hold a patterning device or substrate. 14. A lithography apparatus equipped with a stage device as described in Clause 12 or 13. 15. A method for determining the position-dependent motor constant of an electromagnetic motor comprising a magnet assembly and a coil assembly configured to be displaced relative to each other in the direction of movement, Displacing the magnet assembly relative to the coil assembly in a direction of movement along a predetermined trajectory of interest at a substantially constant speed, Applying a disturbance having a predetermined frequency to an electromagnetic motor during the displacement of the magnet assembly relative to the coil assembly, To determine the positional error of the magnet assembly relative to the coil assembly and the electromagnetic motor force along a predetermined orbit of interest, and Based on the determined position error and electromagnetic motor force, determine the position-dependent motor constants of the electromagnetic motor along a predetermined trajectory of interest. Methods that include... 16. The method according to clause 15, further comprising receiving or generating a position setpoint that causes displacement of the electromagnetic motor, and receiving a position signal representing the position of the electromagnetic motor. 17. The method according to clause 16, further comprising determining a desired motor force during displacement based on a position setpoint and a position signal. 18. The method according to Clause 17, wherein the disturbance is a disturbance force, and the application of the disturbance includes superimposing the disturbance force on a desired motor force.

Claims

1. It is an electromagnetic motor, A magnet assembly configured to generate a magnetic field, A coil assembly comprising at least one coil, wherein the coil assembly is configured to cooperate with the magnet assembly in order to move the magnet assembly in a direction relative to the coil assembly, A power supply configured to supply power to the coil assembly during use, It is a control unit, To displace the magnet assembly relative to the coil assembly along a predetermined trajectory of interest in the direction of movement at a substantially constant speed, the power supply is controlled to supply current to the coil assembly. During the displacement of the magnet assembly relative to the coil assembly, a disturbance having a predetermined frequency is applied to the electromagnetic motor. The position of the magnet assembly relative to the coil assembly and the electromagnetic motor force are determined along the predetermined trajectory of interest. A control unit configured to determine the position-dependent motor constant of the electromagnetic motor along the predetermined trajectory of interest based on the determined position and the electromagnetic motor force, An electromagnetic motor equipped with [a specific feature].

2. The magnet assembly comprises a magnet array for generating a spatially alternating magnetic field in the direction of movement during use, The electromagnetic motor according to claim 1, wherein the coil assembly comprises a coil array arranged in the direction of movement.

3. The electromagnetic motor according to claim 1 or 2, wherein the disturbance is substantially a sinusoidal disturbance.

4. The electromagnetic motor according to any one of claims 1 to 3, wherein the control unit is configured to receive or generate a position setpoint that causes the electromagnetic motor to cause the displacement, and to receive a position signal representing the position of the electromagnetic motor.

5. The electromagnetic motor according to claim 4, wherein the control unit is configured to determine a position error along the trajectory of interest based on the position signal and the position setpoint, and to determine the position-dependent motor constant of the electromagnetic motor along the predetermined trajectory of interest based on the determined position error and the electromagnetic motor force.

6. The electromagnetic motor according to claim 4 or 5, wherein the control unit is configured to determine a desired motor force during the displacement based on the position setpoint and the position signal.

7. The aforementioned disturbance is a positional disturbance, The electromagnetic motor according to any one of claims 4 to 6, wherein the control unit is configured to superimpose the position disturbance on the position setpoint, or the difference between the position setpoint and the position signal.

8. The electromagnetic motor further comprises an actuator, The electromagnetic motor according to any one of claims 4 to 6, wherein the control unit is configured to control the operation of the actuator in order to cause the disturbance.

9. The electromagnetic motor according to any one of claims 1 to 8, wherein determining the position of the magnet assembly relative to the coil assembly and the electromagnetic motor force includes determining the position and the amplitude of the electromagnetic motor force along a predetermined trajectory of interest.

10. The electromagnetic motor according to any one of claims 1 to 9, referencing claim 2, wherein the predetermined frequency and substantially constant speed are selected such that the disturbance has multiple periods between the displacement of the magnet assembly relative to the coil assembly over the magnet pitch of the magnet array.

11. A stage device used in a lithography apparatus, A stage comprising an electromagnetic motor according to any one of claims 1 to 10.

12. The stage apparatus according to claim 11, wherein the stage is configured to hold a patterning device or a substrate.

13. A lithography apparatus comprising the stage device described in claim 11 or 12.

14. A method for determining the position-dependent motor constants of an electromagnetic motor comprising a magnet assembly and a coil assembly configured to be displaced relative to each other in the direction of movement, Displace the magnet assembly relative to the coil assembly along a predetermined trajectory of interest in the direction of movement at a substantially constant speed. During the displacement of the magnet assembly relative to the coil assembly, a disturbance having a predetermined frequency is applied to the electromagnetic motor. To determine the positional error of the magnet assembly relative to the coil assembly and the electromagnetic motor force along the predetermined trajectory of interest, and, Based on the determined position error and the electromagnetic motor force, determine the position-dependent motor constant of the electromagnetic motor along the predetermined trajectory of interest. Methods that include...

15. The electromagnetic motor receives or generates a position setpoint that causes the displacement, and Receiving a position signal representing the position of the electromagnetic motor, The method according to claim 14, further comprising:

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