Electronic circuits, positioning systems, processing equipment, and methods for stopping the movement of moving objects.

Abstract

The invention proposes an electronic circuit for supplying power to a winding or assembly of windings of an electromagnetic motor. The electronic circuit comprises a normal operating circuit used in normal operating mode, a braking circuit used in emergency mode, and a switching device for switching between normal and emergency operating modes. In normal operating mode, the electronic circuit is configured to supply power to the winding or assembly of windings. In emergency mode, the electronic circuit is configured to short-circuit the winding or assembly of windings through the braking circuit. The braking circuit is arranged to create negative resistance or negative impedance to increase the braking force.

Description

ELECTRONIC CIRCUIT, POSITIONING SYSTEM, SUBSTRATE HANDLING APPARATUS AND METHOD FOR BRAKING MOVEMENT OF A MOVABLE OBJECTCROSS-REFERENCE TO RELATED APPLICATION

[0001] The application claims priority of EP application 23207124.1 which was filed on 31 October, 2023; and which is incorporated herein in their entirety by reference.FIELD

[0002] The invention relates to an electronic circuit for powering a coil or coil set of an electromagnetic motor. The invention further relates to a positioning system, a substrate handling apparatus, and a method for braking movement of a movable object.BACKGROUND

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

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

[0005] In a lithographic apparatus positioning systems may be used to position movable objects, for example to move a movable object along a trajectory. Such positioning systems comprise actuators to exert a force on the movable object. Electromagnetic motors may be used as actuators to exert an actuation force on the movable object.

[0006] In an emergency situation, it may be desired to make an emergency stop with a movable object, for example when it has been determined that some safety requirements are not met. When such an emergency stop is required, an electromagnetic motor may be short-circuited to cause a braking forcein the electromagnetic motor as a result of the back-emf (back-electromotive force) of the coil or coil set of the electromagnetic motor due to the movement of the movable object.

[0007] With an increasing demand on the throughput and overlay performance of a lithographic apparatus, the required accelerations and velocities of the movable objects also increase. These increased accelerations and velocities also increase the collision risk when an emergency situation occurs.SUMMARY

[0008] It is an aim of the invention to provide an electronic circuit that can be used to provide an improved braking of movable objects in emergency situations in order to reduce braking distance and / or braking time.

[0009] According to an aspect of the invention, there is provided an electronic circuit for powering a coil or coil set of an electromagnetic motor, wherein the electronic circuit comprises: a normal operating circuit to be used during a normal operating mode, a braking circuit to be used during an emergency mode, and a switch device for switching between the normal operating mode and the emergency mode, wherein in the normal operating mode, the electronic circuit is configured to supply a power to the coil or coil set, and in the emergency mode, the electronic circuit is configured to short-circuit the coil or coil set across the braking circuit, wherein the braking circuit is arranged to create a negative resistance or negative impedance.

[0010] According to an aspect of the invention, there is provided a positioning system for positioning a movable object, wherein the positioning system comprises an electromagnetic motor and the electronic circuit of any of the claims 1-9 for powering a coil or coil set of the electromagnetic motor.

[0011] According to an aspect of the invention, there is provided a substrate handling apparatus, for example a lithographic apparatus, comprising the positioning system of claim 10 or 11.

[0012] According to an aspect of the invention, there is provided a substrate handling apparatus, for example a lithographic apparatus, comprising the positioning system of claim 10 or 11.

[0013] According to an aspect of the invention, there is provided a method for braking movement of a movable object actuated by an electromagnetic motor, wherein the method comprises the step of: switching from a normal operating mode, in which an electronic circuit is configured to supply a power to a coil or coil set of the electromagnetic motor, to an emergency mode, in which the electronic circuit is configured to short-circuit the coil or coil set across a braking circuit, wherein the braking circuit is arranged to create a negative resistance or negative impedance.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:Figure 1 depicts a schematic overview of a lithographic apparatus;Figure 2 depicts a detailed view of a part of the lithographic apparatus of Figure 1;Figure 3 schematically depicts a control scheme to control a position of a movable object;Figure 4a schematically depicts a first embodiment of an electronic circuit for powering a coil or coil set of an electromagnetic motor in normal operating mode;Figure 4b schematically depicts the electronic circuit of Figure 4a in emergency mode;Figure 5 a schematically depicts a second embodiment of an electronic circuit for powering a coil or coil set of an electromagnetic motor in normal operating mode;Figure 5b schematically depicts the electronic circuit of Figure 5a in emergency mode;Figure 6a schematically depicts a third embodiment of an electronic circuit for powering a coil or coil set of an electromagnetic motor in normal operating mode; andFigure 6b schematically depicts the electronic circuit of Figure 6a in emergency mode.DETAILED DESCRIPTION

[0015] In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g. with a wavelength of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultra-violet radiation, e.g. having a wavelength in the range of about 5- 100 nm).

[0016] The term “reticle”, “mask” or “patterning device” as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term “light valve” can also be used in this context. Besides the classic mask (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable LCD array.

[0017] Figure 1 schematically depicts a lithographic apparatus LA. The lithographic apparatus LA includes an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation or EUV radiation), a 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 accurately position the patterning device MA in accordance with certain 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 accurately position the substrate support in accordance with certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0018] In operation, the illumination system IL receives a radiation beam from a radiation source SO, e.g. via a beam delivery system BD. The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for directing, shaping, and / or controlling radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross section at a plane of the patterning device MA.

[0019] The term “projection system” PS used herein should be broadly interpreted as encompassing various types of projection system, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, and / or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system” PS.

[0020] The lithographic apparatus LA may be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system PS and the substrate W - which is also referred to as immersion lithography. More information on immersion techniques is given in US6952253, which is incorporated herein by reference.

[0021] The lithographic apparatus LA may also be of a type having two or more substrate supports WT (also named “dual stage”). In such “multiple stage” machine, the substrate supports WT may be used in parallel, and / or steps in preparation of a subsequent exposure of the substrate W may be carried out on the substrate W located on one of the substrate support WT while another substrate W on the other substrate support WT is being used for exposing a pattern on the other substrate W.

[0022] In addition to the substrate support WT, the lithographic apparatus LA may comprise a measurement stage. The measurement stage is arranged to hold a sensor and / or a cleaning device. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning device may be arranged to clean part of the lithographic apparatus, for example a part of the projection system PS or a part of a system that provides the immersion liquid. The measurement stage may move beneath the projection system PS when the substrate support WT is away from the projection system PS.

[0023] In operation, the radiation beam B is incident on the patterning device, e.g. mask, MA which is held on the mask support MT, and is patterned by the pattern (design layout) present on patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and a position measurement system PMS, the substrate support WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B at a focused and aligned position. Similarly, the first positioner PM and possibly another position sensor (which is not explicitly depicted in Figure 1) may be used to accurately position the patterningdevice MA with respect to the path of the radiation beam B. Patterning device MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks Pl, P2 as illustrated occupy dedicated target portions, they may be located in spaces between target portions. Substrate alignment marks Pl, P2 are known as scribe-lane alignment marks when these are located between the target portions C.

[0024] To clarify the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axis, i.e., an x-axis, a y-axis and a z-axis. Each of the three axis is orthogonal to the other two axis. A rotation around the x-axis is referred to as an Rx-rotation. A rotation around the y- axis is referred to as an Ry-rotation. A rotation around about the z-axis is referred to as an Rz-rotation. The x-axis and the y-axis define a horizontal plane, whereas the z-axis is in a vertical direction. The Cartesian coordinate system is not limiting the invention and is used for clarification only. Instead, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example, such that the z-axis has a component along the horizontal plane.

[0025] Figure 2 shows a more detailed view of a part of the lithographic apparatus LA of Figure 1. The lithographic apparatus LA may be provided with a base frame BF, a balance mass BM, a metrology frame MF and a vibration isolation system IS. The metrology frame MF supports the projection system PS. Additionally, the metrology frame MF may support a part of the position measurement system PMS. The metrology frame MF is supported by the base frame BF via the vibration isolation system IS. The vibration isolation system IS is arranged to prevent or reduce vibrations from propagating from the base frame BF to the metrology frame MF.

[0026] The second positioner PW is arranged to accelerate the substrate support WT by providing a driving force between the substrate support WT and the balance mass BM. The driving force accelerates the substrate support WT in a desired direction of movement. Due to the conservation of momentum, the driving force is also applied to the balance mass BM with equal magnitude, but at a direction opposite to the desired direction. Typically, the mass of the balance mass BM is significantly larger than the masses of the moving part of the second positioner PW and the substrate support WT.

[0027] In an embodiment, the second positioner PW is supported by the balance mass BM. For example, wherein the second positioner PW comprises a planar motor to levitate the substrate support WT above the balance mass BM. In another embodiment, the second positioner PW is supported by the base frame BF. For example, wherein the second positioner PW comprises a linear motor and wherein the second positioner PW comprises a bearing, like a gas bearing, to levitate the substrate support WT above the base frame BF.

[0028] The position measurement system PMS may comprise any type of sensor that is suitable to determine a position of the substrate support WT. The position measurement system PMS may comprise any type of sensor that is suitable to determine a position of the mask support MT. The sensor may be an optical sensor such as an interferometer or an encoder. The position measurement system PMS maycomprise a combined system of an interferometer and an encoder. The sensor may be another type of sensor, such as a magnetic sensor, a capacitive sensor or an inductive sensor. The position measurement system PMS may determine the position relative to a reference, for example the metrology frame MF or the projection system PS. The position measurement system PMS may determine the position of the substrate table WT and / or the mask support MT by measuring the position or by measuring a time derivative of the position, such as velocity or acceleration.

[0029] The position measurement system PMS may comprise an encoder system. An encoder system is known from for example, United States patent application US2007 / 0058173A1, filed on September 7, 2006, 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 as well as 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 created by diffracting the original radiation beam with the grating. If both the primary radiation beam and the secondary radiation beam are created by diffracting the original radiation beam with the grating, the primary radiation beam needs to have a different diffraction order than the secondary radiation beam. Different diffraction orders are, for example, + 1storder, -1storder, +2ndorder and -2ndorder. The encoder system optically combines the primary radiation beam and the secondary radiation beam into a combined radiation beam. A sensor in the encoder head determines a phase or phase difference of the combined radiation beam. The sensor generates a signal based on the phase or phase difference. The signal is representative of a position of the encoder head relative to the grating. One of the encoder head and the grating may be arranged on the substrate structure WT. The other of the encoder head and the grating may be arranged on the metrology frame MF or the base frame BF. For example, a plurality of encoder heads are arranged on the metrology frame MF, whereas a grating is arranged on a top surface of the substrate support WT. In another example, a grating is arranged on a bottom surface of the substrate support WT, and an encoder head is arranged below the substrate support WT.

[0030] The position measurement system PMS may comprise an interferometer system. An interferometer system is known from, for example, United States patent US 6,020,964, filed on July 13, 1998, hereby incorporated by reference. The interferometer system may comprise a beam splitter, a mirror, a reference mirror and a sensor. A beam of radiation is split by the beam splitter into a 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 a phase or a frequency of the combined radiation beam. The sensor generates a signal based on the phase or the frequency. The signal is representative of a displacement of the mirror. In an embodiment, the mirror is connected to the substrate support WT. Thereference mirror may be connected to the metrology frame MF. In an embodiment, the measurement beam and the reference beam are combined into a combined radiation beam by an additional optical component instead of the beam splitter.

[0031] The first positioner PM may comprise a long-stroke module and a short-stroke module. The short-stroke module is arranged to move the mask support MT relative to the long-stroke module with a high accuracy over a small range of movement. The long-stroke module is arranged to move the shortstroke module relative to the projection system PS with a relatively low accuracy over a large range of movement. With the combination of the long-stroke module and the short-stroke module, the first positioner PM is able to move the mask support MT relative to the projection system PS with a high accuracy over a large range of movement. Similarly, the second positioner PW may comprise a long- stroke module and a short-stroke module. The short-stroke module is arranged to move the substrate support WT relative to the long-stroke module with a high accuracy over a small range of movement. The long-stroke module is arranged to move the short-stroke module relative to the projection system PS with a relatively low accuracy over a large range of movement. With the combination of the long- stroke module and the short- stroke module, the second positioner PW is able to move the substrate support WT relative to the projection system PS with a high accuracy over a large range of movement.

[0032] As shown in Figure 2, for the second positioner PW, multiple actuators ACT may be provided to accelerate the substrate support WT in a direction of movement. These actuators ACT may be linear actuators to provide a driving force along a single axis, for example the x-axis. Multiple linear actuators may be applied to provide driving forces along multiple axes. The actuators ACT may comprise a planar actuator to provide a driving force along multiple axes. For example, the planar actuator may be arranged to move the substrate support WT in 6 degrees of freedom.

[0033] The actuators ACT may be electro-magnetic actuators comprising at least one coil and at least one magnet. Each of these actuators may be arranged to move the at least one coil relative to the at least one magnet by applying an electrical current to the at least one coil. The actuators ACT may be a moving-magnet type actuator, which have the at least one magnet coupled to the substrate support WT. The actuators ACT may be a moving-coil type actuator which has the at least one coil coupled to the substrate support WT. The actuators ACT may be a voice-coil actuator, a reluctance actuator, a Lorentz - actuator or a piezo- actuator, or any other suitable actuator.

[0034] The lithographic apparatus LA comprises a position control system to control the position of the substrate support W.

[0035] Figure 3 shows a control scheme for controlling a position of a movable object O, for example a substrate support WT. The control scheme comprises a position control system PCS. The position control system PCS is arranged to provide actuator inputs a; as input signals for the actuators ACT. The actuators ACT will exert an actuation force on the movable object O corresponding to the respective actuator inputs a; resulting in a movement of the movable object O to a position related value x, such as position, velocity and / or acceleration.

[0036] The position control system PCS comprises a set-point generator SP, a feedforward controller FF, a feedback controller FB, and a transformation matrix Tf. The set-point generator SP is arranged to provide a series of set-points to be followed by the controlled object, for example the substrate support WT or the mask support MT. The series of set-points may for instance comprise a series of positions, velocities and / or accelerations that represent an intended trajectory of the movable object O.

[0037] The feedforward controller FF may provide a feedforward control signal fff on the basis of the set-point r provided by the set-point generator SP. The feedback controller FB may provide a feedback control signal fa, on the basis of a control error e, i.e. the difference between the set-point r and the actual position related value xm as measured by a position measurement system PMS. The feedforward signal fff and the feedback control fa, may be combined into a control signal f which is fed into the transformation matrix Tf.

[0038] The transformation matrix Tf is arranged to transform the control signal f into actuation signals a; that are fed into the actuators ACT in order to exert actuation forces on the movable object O in the respective actuation directions. The transformation matrix Tf may be part of gain balancing and gain scheduling device that is arranged to carry out gain balancing and gain scheduling steps to provide the transformation of the control signal f into the actuator inputs a;.

[0039] The gain balancing and gain scheduling steps may for instance provide a transformation of the control signal, e.g. the desired actuator forces, into the actuator input, e.g. current setpoints for the actuators ACT, using a nonlinear function of required force and actual actuator position.

[0040] The position control system PCS of Figure 3 is configured to position a movable object O. This movable object may be the substrate support WT shown in Figure 2 or another movable object O, for example a movable object O of a substrate handling apparatus. The substrate handling apparatus may be a lithographic apparatus. The movable object O may be a substrate handler, e.g. a substrate handling robot, or a component of a patterning device masking device, e.g. a rema (reticle masking) blade, or any other movable object of a lithographic apparatus.

[0041] Figure 4a shows schematically an electronic circuit 1 for powering a coil or coil set of an electromagnetic motor. The electronic circuit 1 transforms the actuator input signal a;, as provided by the position control system PCS, into a corresponding input power for the coil or coil set 2 of the electromagnetic motor, indicated in the electronic circuit 1 as a resistor. For this transformation the electronic circuit 1 comprises an operational amplifier 3, that amplifies the actuator input signal a; to the corresponding input power for the coil or coil set 2.

[0042] In an emergency situation, for example during a glitch of the position measurement system PMS, the movable object O needs to be stopped as quickly as possible, to avoid any damage. In such a case, the coil or coil set 2 may be short-circuited to create damping in the electromagnetic motor by the back-emf (back-electromotive force), also known as counter-electromotive force. The short-circuit leads to a current in the coil or coil set 2 of the electromagnetic motor that creates a force in a directionopposite to the velocity of the movable object O. This damping force therefore reduces the velocity of the movable object O.

[0043] For short-circuiting of the coil or coil set 2 a switch device 4 may be provided. The switch device 4 can be switched between normal operating mode and an emergency mode. During normal operation, the switch device 4 will be arranged in the normal operating mode. When an emergency situation occurs, the switch device 4 may switch to emergency mode in order to brake and stop the movable object O.

[0044] The switch device 4 has a switch 5 that can be switched between a normal operating position in which the operational amplifier 3 is connected to the coil or coil set 2 to provide the input power to the coil or coil set 2, and an emergency position in which the coil or coil set 2 is connected to ground 6 to short-circuit the coil or coil set 2.

[0045] Figure 4a shows the electronic circuit 1 in normal operating mode in which switch 5 is arranged in the normal operating position. In this normal operating mode power is provided to the coil or coil set 2 based on the actuator input a;, for example to move the movable object O to along a desired trajectory.

[0046] Figure 4b shows the electronic circuit 1 in emergency mode in which switch 5 is arranged in the emergency position. In this emergency position a damping force may be created in the electromagnetic motor 2 due to the back-EMF in the coil or coil set 2 in dependence of the velocity of the movable object O. The back-EMF current is proportional to the velocity of the movable object O by the motor constant and the inverse of the motor coil resistance. The damping force is proportional to the current. The amount of damping force by the short-circuit of the coil or coil set 2 is thus limited by the internal electrical resistance of the coil or coil set 2.

[0047] Although the damping force actually provides an effective braking force on the movable object, this braking force may be insufficient in some situations.

[0048] For example, when a movable object O has relatively high speed or has a relatively small range of movement, the braking force created by short-circuiting the coil or coil set 2 may not be large enough to stop movement of the movable object O within a relatively small braking distance. In some embodiments of a lithographic apparatus, components of the patterning device masking device, such as a rema blade, may move at a high speed very close to the patterning device and optical components. In case of an emergency, that moving component may still hit an end stop with a risk of damage even when the braking force created by back-EMF is used to brake the movement of the respective component.

[0049] More generally, it may be desirable to stop, in an emergency situation, movable objects O as quickly as possible and / or with a minimum braking path distance to reduce the risk of damage due to a collision of the movable object O with another part of the respective apparatus.

[0050] Figures 5a and 5b show a first embodiment of an electronic circuit 10 that is configured to provide an increased braking force in an emergency mode compared to the electronic circuit 1 of Figures4a and 4b. Figure 5a shows the electronic circuit 10 in normal operating mode. Figure 5b show the electronic circuit 10 in emergency mode.

[0051] In the normal operating mode, a normal operating circuit 11 is used to feed an input signal a;, e.g. provided by the position control system PCS of Figure 3, to an amplifier, for example a first operational amplifier 13. The first operational amplifier 13 amplifies the actuator input signal a; to the corresponding input power for the coil or coil set 12 of the electromagnetic motor. In the normal operating mode, the electronic circuit 10 functions generally the same as in the embodiment of Figure 4a.

[0052] The electronic circuit 10 further comprises a switch device 14 and a braking circuit 16.

[0053] The switch device 14 can be switched between the normal operating mode shown in Figure 5 a and an emergency mode as shown in Figure 5b. During normal operation, the switch device 14 will be arranged in the normal operating mode. When an emergency situation occurs, the switch device 14 may switch to emergency mode in order to brake and stop the movable object O as quickly as possible and / or with minimum braking path distance.

[0054] The switch device 14 has a switch 15 that can be switched between a normal operating position in which the operational amplifier 13 is connected to the coil or coil set 12 to provide, based on the actuator input signal a;, the input power to the coil or coil set 2 and an emergency position in which the coil or coil set 12 is connected to the braking circuit 16.

[0055] The switch device 14 is configured to be arranged in the normal operating mode or the emergency mode in dependence of a switch device control signal provided by a controller, for example a controller of the position control system PCS shown in Figure 3 or any other suitable controller. The switch device 14 is configured to switch from the normal operating mode to the emergency mode and / or to remain in the emergency mode when the switch device control signal has a value corresponding to a value indicating an emergency. Correspondingly, the switch device 14 is configured to switch from the emergency mode to the normal operating mode and / or to remain in the normal operating mode when the switch device control signal has a value corresponding to a value indicating normal operating mode.

[0056] The switch device 14 may be arranged to have the emergency mode as default mode. This means that if the switch device control signal has any other value than a value corresponding to the normal operating mode, the switch device 14 will switch to and / or remain in the emergency mode.

[0057] The switch 15 of the switch device 14 may be any suitable switch, such as an electromechanical switch, e.g. a relay, or an active switch, such as a field-effect transistor (FET) or another type of transistor.

[0058] The braking circuit 16 is arranged to create a negative resistance when the switch device 14 is arranged in the emergency mode. The braking circuit 16 comprises a second operational amplifier 17 and three resistors 18a, 18b, 18c. The three resistors 18a, 18b, 18c may have an equal resistance. The first resistor 18a is arranged between ground 19 and the non-inverting input of the second operational amplifier 17, the second resistor 18b is arranged between the non-inverting input of the secondoperational amplifier 17 and the output of the second operational amplifier 17, and the third resistor 18c is arranged between the inverting input of the second operational amplifier 17 and the output of the second operational amplifier 17. The inverting input of the second operational amplifier 17 is also connected to the switch device 14. When this braking circuit 16 is connected to the coil or coil set 12, as shown in Figure 5b, the electronic circuit 10 forms a negative impedance converter. Additionally, the braking circuit 16 may comprise a coil arranged between the inverting input of the second operational amplifier 17 and the third resistor 18c. This braking circuit is arranged to create a negative impedance when the switch device 14 is arranged in the emergency mode. In the emergency mode, the inductance of the coil or coil set 12 may create an out-of-phase current when braking. The negative impedance created by the braking circuit 16 may counter the inductance of the coil or coil set 12. Alternatively, the coil arranged between the inverting input of the second operational amplifier 17 and the third resistor 18c may be replaced by a capacitor in at least one of the first resistor 18a and the second resistor 18b.

[0059] A negative impedance converter is an active circuit which injects energy into circuits in contrast to an ordinary load that consumes energy from them. This may be achieved by adding or subtracting excessive varying voltage in series to the voltage drop across an equivalent positive impedance. This reverses the voltage polarity or the current direction of the port and introduces a phase shift of 180° between the voltage and the current for any signal generator. The negative impedance converter may for example be a negative impedance converter with voltage inversion or a negative impedance converter with current inversion.

[0060] In an emergency situation, for example during a glitch of the position measurement system PMS, the switching device 14 will switch the switch 15 from the normal operating position to the emergency position. Due to the negative impedance converter being formed by switching to the emergency mode, a substantially larger braking force and hence a much faster stop can be obtained than the braking force created in the embodiment of Figures 4a and 4b.

[0061] The main reason for this larger braking force is that the resistance or negative impedance in the electronic circuit 10 in emergency mode becomes the resistance or negative impedance of the coil or coil set 12 plus the negative resistance or negative impedance created by the negative impedance converter. This combined resistance or impedance may be much smaller than the resistance or impedance of the coil or coil set 12 itself. Hence, the damping force due to back-EMF that causes braking of the movable object O may be increased significantly.

[0062] For example, for a three-phase motor, in the electronic circuit 1 in the emergency mode, as shown in Figure 4b, the braking force (without a negative resistance) is equal to:wherein kmis a motor constant, Rmis the resistance of the coil or coil set 2 and v is the velocity of the movable object O.

[0063] For this three-phase motor, the braking force with a negative resistance, as shown in the electronic circuit 10 in the emergency mode of Figure 5b, is equal to:wherein kmis a motor constant, Rmis the resistance of the coil or coil set 12 and Rnis the resistance of each of the three resistors 18a, 18b, 18c, and v is the velocity of the movable object O.

[0064] It will be clear that by selecting a suitable resistance of the three resistors 18a, 18b, 18c, the braking force may be increased substantially.

[0065] The actual braking force that is created in emergency mode will also depend on the velocity of the movable object O. If the velocity is zero, the braking force will automatically also become zero. This is advantageous as there is no active actuation and control of the electromagnetic motor required to create the increased braking force. The braking force will only come into existence when needed, i.e. when the movable object O is moving.

[0066] In the embodiment of Figures 5a and 5b two operational amplifiers are provided. The first operational amplifier 13 is arranged in the normal operating circuit 11 to provide, during normal operating mode, an input power for the coil or coil set 12 on the basis of the actuator input signal a;. The second operational amplifier 17 is used in the braking circuit 16 to create a negative resistance or negative impedance in the emergency mode to increase the braking force on the movable object O. This configuration thus requires two operational amplifiers.

[0067] Figures 6a and 6b show an alternative embodiment of an electronic circuit 10 for powering a coil or coil set of the electromagnetic motor, wherein use is made of a negative resistance or negative impedance to increase a braking force in an emergency mode.

[0068] The main difference between the embodiment of Figures 5 a and 5b and the embodiment of Figures 6a and 6b is that in the embodiment of Figures 6a and 6b the same operational amplifier 20 is used in the normal operating mode and the emergency mode.

[0069] Further, the switching device 14 comprises a first switch 15a and a second switch 15b. The first switch 15a and the second switch 15b of the switch device 14 may be any suitable switch, such as an electro- mechanical switch, e.g. a relay, or an active switch, such as a field-effect transistor (FET) or another type of transistor.

[0070] The first switch 15a can be arranged in a normal operating position (Figure 6a) and an emergency position (Figure 6b) and, correspondingly, the second switch 15b can be arranged in a normal operating position (Figure 6a) and an emergency position (Figure 6b). The switching device 14 is configured to arrange both the first switch 15a and the second switch 15b in either the normaloperating position, when in normal operating mode, or in the emergency position, when in emergency mode.

[0071] In the normal operating mode, the first switch 15a connects the operational amplifier 20 to an input device, for example the position control system PCS of Figure 3, to receive the actuator input signal a; and the second switch 15b is arranged to bypass the third resistor 18c of the braking circuit 16. In the emergency mode, the first switch 15a and the second switch 15b are arranged to create a negative impedance converter configuration similar to the configuration of Figure 5b.

[0072] The advantage of this configuration of Figures 6a and 6b is that only one operational amplifier 20 is needed. However, if a failure in the operational amplifier 20 results in an emergency situation, the failure in the operational amplifier 20 may also prevent that a negative resistance or negative impedance can be created in the emergency mode. In such situation, there may be relied on the ‘normal’ braking force created by the back-emf of the electromagnetic motor due to movement of the movable object O. A further disadvantage of the embodiment of Figures 6a and 6b is that a relatively more complex switching device is needed.

[0073] In both embodiments, a negative impedance converter is effectively used to increase, in an emergency situation, a braking force on a movable object due to back-EMF in order to substantially decrease braking time and / or braking path distance.

[0074] Hereinabove, the use of operational amplifiers is described for powering a coil or coil set in normal operating mode and / or to create a negative resistance or negative impedance in emergency mode. In alternative embodiments other types of amplifiers may also be applied. The amplifier may for example be based on discrete components or an amplifier created by a bridge configuration.

[0075] Hereinabove, an electronic circuit for powering a coil or coil set of an electromagnetic motor is described, wherein, in an emergency mode, the electronic circuit is configured to short circuit the coil or coil set of the electromagnetic across a braking circuit, wherein the braking circuit is arranged to create a negative resistance or negative impedance using a negative impedance converter configuration. The negative resistance or negative impedance created by the negative impedance converter configuration increases the braking force exerted in the electromagnetic motor. In other embodiments, other configurations creating a negative resistance or negative impedance may be applied to create an increased braking force in the electromagnetic motor of a positioning system.

[0076] Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquidcrystal displays (LCDs), thin-film magnetic heads, etc.

[0077] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, orany apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions or ambient (non-vacuum) conditions.

[0078] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention, where the context allows, is not limited to optical lithography and may be used in other applications, for example imprint lithography.

[0079] Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine -readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine -readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.

[0080] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. An electronic circuit for powering a coil or coil set of an electromagnetic motor, wherein the electronic circuit comprises: a normal operating circuit to be used during a normal operating mode, a braking circuit to be used during an emergency mode, and a switch device for switching between the normal operating mode and the emergency mode, wherein in the normal operating mode, the electronic circuit is configured to supply a power to the coil or coil set, and in the emergency mode, the electronic circuit is configured to short circuit the coil or coil set across the braking circuit, wherein the braking circuit is arranged to create a negative resistance or negative impedance.

2. The electronic circuit of claim 1, wherein in the emergency mode the electronic circuit is configured as a negative impedance converter.

3. The electronic circuit of claim 1 or 2, wherein the normal operating circuit comprises a first amplifier to provide the power to the coil or coil set based on an input signal fed into an input of the first amplifier.

4. The electronic circuit of claim 3, wherein the switch device comprises a switch arranged to connect in the normal operating mode the first amplifier to the coil or coil set and to connect in the emergency mode the braking circuit to the coil or coil set.

5. The electronic circuit of claim 4, wherein the braking circuit comprises a second amplifier.

6. The electronic circuit of claim 2, wherein the electronic circuit comprises an amplifier configured to provide, in the normal operating mode, the power to the coil or coil set based on an input signal fed into an input of the amplifier, and to function, in the emergency mode, as amplifier of the negative impedance converter.

7. The electronic circuit of claim 6, wherein the switch device comprises a first switch and a second switch, wherein, in the normal operating mode, the first switch is arranged to connect the amplifier to an input device configured to provide the input signal to the input of the amplifier and the second switch is arranged to bypass a resistor of the negative impedance converter, andwherein, in the emergency mode, the first switch and second switch are arranged to create a negative impedance converter configuration.

8. The electronic circuit of any of the claims 1-7, wherein the switch device is configured to be arranged in the normal operating mode or the emergency mode in dependence of a switch device control signal provided by a controller, wherein the switch device is configured to switch from the normal operating mode to the emergency mode when the switch device control signal indicates an emergency.

9. The electronic circuit of any of the claims 1-8, wherein the switch device is arranged to have the emergency mode as default mode.

10. A positioning system for positioning a movable object, wherein the positioning system comprises an electromagnetic motor and the electronic circuit of any of the preceding claims for powering a coil or coil set of the electromagnetic motor.

11. The positioning system of claim 10, wherein the positioning system comprises a controller configured to provide a switch device control signal to control the switch device to switch between the normal operating mode and the emergency mode.

12. A substrate handling apparatus, for example a lithographic apparatus, comprising the positioning system of claim 10 or 11.

13. The substrate handling apparatus of claim 12, wherein the movable object is a substrate support, a patterning device support, a patterning device masking blade, or a substrate handler.

14. A method for braking movement of a movable object actuated by an electromagnetic motor, wherein the method comprises the step of: switching from a normal operating mode, in which an electronic circuit is configured to supply a power to a coil or coil set of the electromagnetic motor, to an emergency mode, in which the electronic circuit is configured to short circuit the coil or coil set across a braking circuit, wherein the braking circuit is arranged to create a negative resistance or negative impedance.

15. The method of claim 14, wherein the step of switching from the normal operating mode to the emergency mode is carried out in an emergency situation.

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