Positioning system, lithography tool and method for positioning a movable object using the positioning system - Patents.com

Abstract

The present invention provides a positioning system for positioning a movable object, comprising: a plurality of actuators configured to move the movable object in one or more degrees of freedom, the plurality of actuators comprising actuators with more than the one or more degrees of freedom, a control system comprising a controller providing control signals based on a set point and / or a control error, and a transformation matrix for transforming the control signals into actuator inputs of the plurality of actuators, the transformation matrix comprising a transformation value for each relationship between one of the control signals and one of the actuator inputs, the transformation value being selected in response to a desired trajectory of the movable object and / or the transformation value being adjustable in use in response to one or more actual performance-related parameters of the positioning system.

Description

[Technical Field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to European Application No. 22205478.5, filed November 4, 2022, which is incorporated herein by reference in its entirety.

[0002] [Technical field] The present invention relates to a positioning system for positioning a movable object. The present invention further relates to a method for positioning a movable object using a positioning system. [Background technology]

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

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually decreased, while the number of functional elements, such as transistors, per device has steadily increased for decades, following a trend commonly referred to as "Moore's Law." To keep up with Moore's Law, the semiconductor industry is pursuing technologies capable of producing increasingly smaller features. To project patterns onto a substrate, lithography equipment may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features 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 ranging from 4 nm to 20 nm, such as 6.7 nm and 13.5 nm, can form smaller features on a substrate than lithography equipment using radiation with a wavelength of, for example, 193 nm.

[0005] In a lithographic apparatus, a positioning system may be used to move a movable object along a trajectory. Such a positioning system, used for example to move a substrate support or a patterning device support, comprises an actuator that applies a driving force to the movable object in a driving direction, and a control system that provides an actuator input to the actuator.

[0006] The control system may include a controller, such as a feedback controller and / or a feedforward controller, that provides a control signal based on a set point and / or a control error (i.e., the difference between the set point and an actual position-related value of the movable object). The control system may further include a transformation matrix that transforms the control signal in the control coordinate system into a drive signal in the drive coordinate system. Such a transformation is required, for example, when the drive direction of the actuator does not have a one-to-one correspondence with the movement direction of the movable object in the control coordinate system.

[0007] In some embodiments of the positioning system, the positioning system is over-actuated. In an over-actuated positioning system, a plurality of actuators may be configured to move the movable object in one or more degrees of freedom, where the number of actuators is greater than the number of degrees of freedom. In practice, the positioning system may have, for example, 12 actuators to control the position of the movable object in six degrees of freedom, meaning that for each degree of freedom, at least two actuators are available to apply actuation forces for movement in that degree of freedom, for a total of at least 12 actuators.

[0008] Thus, in an overdriven positioning system, the drive force to be applied by an actuator in a single degree of freedom may be distributed to at least two actuators, resulting in a degree of freedom in the distribution of these drive forces, which may be used to limit the peak temperature of each actuator and / or to limit another performance-related parameter of the positioning system.

[0009] As the demands on throughput and overlay performance of lithographic apparatus increase, it becomes necessary to use more diverse trajectories for the substrate support, especially during the alignment phase when measuring multiple alignment marks provided on the substrate, which causes different loads on the positioning system and makes it difficult to keep performance-related parameters, such as peak temperatures of actuators, below safe thresholds. Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide a positioning system for positioning a moveable object that can be used for a wider variety of trajectories of the moveable object without exceeding a safety threshold of one or more performance-related parameters, such as the peak temperature of the actuators of the positioning system. [Means for solving the problem]

[0011] According to an aspect of the present invention, there is provided a positioning system for positioning a movable object, the positioning system comprising: a plurality of actuators configured to move the moveable object in one or more degrees of freedom, the actuators comprising more than the one or more degrees of freedom; a control system comprising: a controller that provides a control signal based on a set point and / or a control error; and a transformation matrix that transforms the control signal into actuator inputs for a plurality of actuators; The transformation matrix comprises a transformation value for each relationship between one of the control signals and one of the actuator inputs, the transformation value being selected depending on the intended trajectory of the movable object and / or the transformation value being adjustable depending on one or more actual performance related parameters of the positioning system in use.

[0012] One aspect of the present invention is a method of positioning a movable object using a positioning system, the method comprising: providing a control signal based on the set point and / or control error; - transforming the control signals into actuator inputs using a transformation matrix, the transformation matrix comprising a transformation value for each relationship between one of the control signals and one of the actuator inputs, the transformation value being selected in response to a planned trajectory of the movable object and / or the transformation value being adjusted in use in response to one or more actual performance related parameters of the positioning system; and driving a plurality of actuators of a positioning system using the actuator input to move the movable object in one or more degrees of freedom, the plurality of actuators comprising actuators for more than the one or more degrees of freedom. [Brief explanation of the drawings]

[0013] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: [Figure 1] 1 depicts a schematic diagram of a lithographic apparatus; [Figure 2] 2 shows a detailed view of a part of the lithographic apparatus of FIG. 1; [Figure 3] 1 shows a schematic diagram of a position control system. [Figure 4] 1 illustrates the trajectory of a substrate support during an exposure phase of a lithography process. [Figure 5] 1 shows the trajectory of a substrate support with balanced x and y motion during the alignment phase of a lithography process. [Figure 6] 1 shows the trajectory of a substrate support with predominant x-motion during the alignment phase of a lithography process. [Figure 7] 1 shows a schematic representation of a position control system with data storage; [Figure 8] 1 illustrates a schematic of a position control system with an adjustable transformation matrix. DETAILED DESCRIPTION OF THE INVENTION

[0014] In this document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g., having wavelengths of 365, 248, 193, 157, or 126 nm), and EUV (extreme ultraviolet radiation, e.g., having wavelengths in the range of about 5-100 nm).

[0015] The terms "reticle," "mask," or "patterning device," as used herein, may be broadly interpreted to refer to any general patterning device that can be used to impart an incident radiation beam with a patterned cross-section that corresponds to the pattern to be created in a target portion of a substrate. The term "light valve" may also be used in this context. In addition to traditional masks (transmissive or reflective; binary, phase-shifting, hybrid, etc.), examples of such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0016] Figure 1 schematically shows a lithographic apparatus LA, comprising: an illumination system (also called an illuminator) IL configured to condition a radiation beam B (e.g. UV radiation, DUV radiation or EUV radiation), a mask support (e.g. a mask table) MT configured 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 certain parameters, a substrate support (e.g. a wafer table) WT configured 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 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 the patterning device MA onto a target portion C (e.g. comprising one or more dies) on the substrate W.

[0017] In operation, the illumination system IL receives a radiation 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 directing, shaping and / or controlling the radiation beam. The illuminator IL may be used to condition the radiation beam B so that it has a desired spatial and angular intensity distribution in its cross-section in the plane of the patterning device MA.

[0018] The term "projection system" PS as used herein should be interpreted broadly as encompassing various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, where appropriate for the exposure radiation used and / or other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term "projection lens" as used herein may be considered synonymous with the more general term "projection system" PS.

[0019] The lithographic apparatus LA may be of a type in which 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 known as immersion lithography. More details about immersion techniques are found in US6952253, which is incorporated herein by reference.

[0020] The lithographic apparatus LA may be of a type having two or more substrate supports WT (also known as "dual stage") In such a "multi-stage" machine, the substrate supports WT may be used in parallel, and / or a substrate W placed on one substrate support WT may be undergoing preparation steps for a subsequent exposure of the substrate W, while another substrate W on another substrate support WT is being used to expose a pattern for the other substrate W.

[0021] In addition to the substrate support WT, the lithographic apparatus LA may comprise a measurement stage. The measurement stage is configured to hold a sensor and / or a cleaning device. The sensor may be configured 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 configured to clean part of the lithographic apparatus, for example part of the projection system PS or part of a system for supplying immersion liquid. The measurement stage may move below the projection system PS when the substrate support WT is spaced apart from the projection system PS.

[0022] In operation, a radiation beam B is incident on a patterning device (e.g., mask MA) held on a mask support MT and is patterned according to a pattern (design layout) present on the patterning device MA. Having passed through 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 the position measurement system PMS, the substrate support WT can be precisely moved, for example, so that different target portions C are positioned at focused and aligned positions in the path of the radiation beam B. Similarly, the first positioner PM, and possibly further position sensors (not explicitly shown in Figure 1), can be used to precisely position the patterning device MA with respect to the path of the radiation beam B. The patterning device MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 are illustrated as occupying dedicated target portions, they may also be located in spaces between the target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are known as scribe-lane alignment marks.

[0023] For clarity of the present invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes: x, y, and z. Each of the three axes is orthogonal to the other two. Rotation about the x-axis is called Rx rotation, rotation about the y-axis is called Ry rotation, and rotation about the z-axis is called Rz rotation. The x- and y-axes define a horizontal plane, and the z-axis is vertical. The Cartesian coordinate system is not a limitation of the present invention and is used for clarity only. Alternatively, another coordinate system, such as a cylindrical coordinate system, may be used for clarity of the present invention. The orientation of the Cartesian coordinate system may be different, for example, the z-axis may have a component along the horizontal plane.

[0024] Figure 2 shows part of the lithographic apparatus LA of Figure 1 in more detail. The lithographic apparatus LA may comprise 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. In addition, the metrology frame MF may support part of the position measurement system PMS. The metrology frame MF is supported on the base frame BF via the vibration isolation system IS. The vibration isolation system IS is configured to prevent or reduce the transmission of vibrations from the base frame BF to the metrology frame MF.

[0025] The second positioner PW is configured to accelerate the substrate support WT by applying 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 of movement. Due to conservation of momentum, the driving force is also applied to the balance mass BM with an equal magnitude but in a direction opposite to the desired direction. Typically, the mass of the balance mass BM is significantly greater than the mass of the movable part of the second positioner PW and the substrate support WT.

[0026] In one embodiment, the second positioner PW is supported by the 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 the 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.

[0027] The position measurement system PMS may comprise any type of sensor suitable for determining the position of the substrate support WT. The position measurement system PMS may comprise any type of sensor suitable for determining the position of the mask support MT. The sensors may be optical sensors, such as interferometers or encoders. The position measurement system PMS may also comprise a combined interferometer and encoder system. The sensors may also be other types of sensors, such as magnetic, capacitive or inductive sensors. 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 a time derivative of the position, such as velocity or acceleration.

[0028] The position measurement system PMS may include an encoder system. Such an encoder system is known, for example, from U.S. Patent Application No. US2007 / 0058173A1, filed September 7, 2006, and incorporated herein by reference. The encoder system includes an encoder head, a grating, and a sensor. The encoder system may receive a primary radiation beam and a secondary radiation beam. Both the primary radiation beam and the secondary radiation beam are generated from the same radiation beam, i.e., the original radiation beam. At least one of the primary radiation beam and the secondary radiation beam is generated by diffracting the original radiation beam with a grating. When both the primary radiation beam and the secondary radiation beam are generated by diffracting the original radiation beam with a grating, the primary radiation beam must have a different diffraction order from the secondary radiation beam. The different diffraction orders are, for example, +1st order, −1st order, +2nd order, and −2nd order. The encoder system optically combines the primary radiation beam and the secondary radiation beam to generate 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 the phase or phase difference. The signal represents the position of the encoder head relative to the grating. One of the encoder head and the grating may be disposed on the substrate structure WT. The other of the encoder head and the grating may be disposed on the metrology frame MF or the base frame BF. For example, multiple encoder heads may be disposed on the metrology frame MF, while the grating is disposed on the upper surface of the substrate support WT. In another example, the grating is disposed on the lower surface of the substrate support WT, and the encoder head is disposed below the substrate support WT.

[0029] The position measurement system PMS may comprise an interferometer system. Interferometer systems are known, for example, from U.S. Pat. No. 6,020,964, filed July 13, 1998, which is incorporated herein by reference. The interferometer system may comprise a beam splitter, a mirror, a reference mirror, and a sensor. A beam of radiation is split into a reference beam and a measurement beam by the beam splitter. 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 combine into 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 one embodiment, the mirror is connected to the substrate support WT. The reference mirror may be connected to the metrology frame MF. In an embodiment, the measurement beam and the reference beam are combined into a combined radiation beam by an additional optical component instead of a beam splitter.

[0030] 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 relative to the long-stroke module with high accuracy over a narrow range of movement. The long-stroke module is configured to move the short-stroke module relative to the projection system PS with relatively low accuracy over a wide range of movement. By combining 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 high accuracy over a wide range of movement. 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 relative to the long-stroke module with high accuracy over a narrow range of movement. The long-stroke module is configured to move the short-stroke module relative to the projection system PS with relatively low accuracy over a wide range of movement. By combining 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 high accuracy over a wide range of movement.

[0031] As shown in FIG. 2, the second positioning device PW may be provided with multiple actuators ACT for accelerating the substrate support WT in the movement direction. These actuators ACT may be linear actuators that provide a driving force along a single axis, such as the X-axis. Alternatively, multiple linear actuators may be applied to provide driving forces along multiple axes. The actuators ACT may include planar actuators that provide driving forces along multiple axes. For example, the planar actuators may be configured to move the substrate support WT with six degrees of freedom.

[0032] The actuator ACT may be an electromagnetic actuator including at least one coil and at least one magnet. Each of these actuators may be configured to move the at least one coil relative to the at least one magnet by passing a current through the at least one coil. The actuator ACT may be a moving magnet type actuator having at least one magnet coupled to the substrate support WT. The actuator ACT may be a moving coil type actuator having at least one coil coupled to the substrate support WT. The actuator ACT may be a voice coil actuator, a reluctance actuator, a Lorentz actuator, a piezoelectric actuator, or any other suitable actuator.

[0033] The lithographic apparatus LA comprises a position control system that controls the position of the substrate support WT.

[0034] 3 shows a control scheme for a movable object O (e.g., a substrate support WT) with a position control system PCS. The position control system PCS is configured to provide actuator inputs a as input signals to actuators ACT. The actuators ACT apply driving forces corresponding to each actuator input a to the movable object O, resulting in the movable object O being accelerated to a position-related value x, such as a position, velocity, and / or acceleration.

[0035] The position control system PCS comprises a setpoint generator SP, a feedforward controller FF, a feedback controller FB, and a transformation matrix Tf. The setpoint generator SP is configured to provide a series of setpoints to be followed by a controlled object (e.g., the substrate support WT or the mask support MT). These series of setpoints comprise, for example, a series of positions, velocities, and / or accelerations that represent a predetermined (intended) trajectory of the movable object O.

[0036] The feedforward controller FF may provide a feedforward control signal fff based on a setpoint r provided by the setpoint generator SP. The feedback controller FB may provide a feedback control signal ffb based on a control error e, i.e., the difference between the setpoint r and the actual position-related value xm measured by the position measurement system PMS. The feedforward signal fff and the feedback control signal ffb are combined into a control signal f that is input to a transformation matrix Tf.

[0037] The transformation matrix Tf is configured to transform the control signal f into a drive signal a to be supplied to the actuator ACT in order to apply a drive force in each drive direction to the movable object O. The transformation matrix Tf may be part of a gain balancing and gain scheduling device configured to perform a gain balancing and gain scheduling step and to transform the control signal f into an actuator input a.

[0038] The gain balancing and gain scheduling steps may convert a control signal (e.g., a desired actuator force) into an actuator input (e.g., a current setpoint for the actuator ACT) using, for example, a non-linear function of the required force and the actual actuator position.

[0039] The gain balancing and gain scheduling step may apply a series of linear controllers, each configured to provide specific control for a different operating point of the system, e.g., the position of the electromagnetic actuator ACT. Based on one or more scheduling variables, the actual operating region of the electromagnetic actuator ACT may be determined, and an associated linear controller may be selected to provide each actuator input.

[0040] For example, in a positioning system that controls the position of a movable object O with six degrees of freedom, the driving direction of the actuator and the six degrees of freedom with which the position of the movable object O is controlled do not necessarily correspond one-to-one.

[0041] The transformation matrix Tf comprises a transformation value for each relationship between one of the control signals f and one of the actuator inputs a. The transformation values ​​may have a value of zero. The transformation matrix Tf may be provided in a classical matrix format with columns and rows, but may also be provided in any other format for defining the relationship between the control signals f and the actuator inputs a using the transformation values.

[0042] The actuators ACT may form an overdriven positioning system having a plurality of actuators configured to move the movable object in one or more degrees of freedom, where the plurality of actuators comprises actuators with more than one degree of freedom, in other words, the overdriven positioning system comprises M actuators to move the movable object in N degrees of freedom, where M and N are natural numbers and M>N.

[0043] In such an overdriven system, at least two actuators ACT may be configured to apply a drive force to the movable object O in one drive direction, the drive directions of the at least two actuators extending at least partially in the same direction, such that at least one degree of freedom can be independently driven by the at least two actuators. In one embodiment, the positioning system may be overdriven in six degrees of freedom, meaning that in each degree of freedom, at least two actuators are available to independently move the movable object O in each degree of freedom, resulting in at least 12 actuators in the overall positioning system. Thus, in an overdriven positioning system, a drive force to be applied in a single degree of freedom may be distributed to at least two actuators. Thus, there is freedom to distribute these drive forces to the actuators.

[0044] The freedom to distribute actuator forces among the actuators can be used to limit and / or optimize one or more performance-related parameters of the positioning system, which may comprise, for example, peak temperature, actuator current in at least two actuators, peak actuator current, peak actuator voltage, actuator availability, and / or tracking performance of the positioning system.

[0045] A transformation matrix Tf, which provides the relationship between the control signals f and the actuator inputs a, can be used for this distribution of the actuator inputs across the actuators ACT.

[0046] The transformation values ​​of the transformation matrix Tf may be adjusted to the trajectory frequently followed by the movable object O, such as for a scanning movement of the substrate support WT during the exposure phase of a lithographic process. This means that the transformation values ​​are determined taking into account that the substrate support WT typically follows a predetermined trajectory. Such an optimized transformation matrix Tf may be effectively used in the exposure phase of a lithographic apparatus, in which the substrate support WT follows a trajectory that is repeatedly scanned in the y direction.

[0047] FIG. 4 shows an example of a trajectory of an exposure phase of the substrate support WT, where the scanning motion in the y direction is dominant.

[0048] However, as the demand for scanning a large number of alignment marks during the measurement phase of the lithography process increases, the variety of trajectories that the substrate support WT must follow also increases. For example, some trajectories that the substrate support WT must follow to scan alignment marks may be relatively dominant in the x direction, while others may be relatively dominant in the y direction, or may be balanced in the x and y directions. Balancing the x and y directions means that such trajectories require similar driving forces in the x and y directions.

[0049] As an example, Figure 5 shows a trajectory for scanning an alignment mark on a substrate where the x- and y-motions are balanced, and Figure 6 shows another trajectory for scanning an alignment mark on a substrate where the x-motion is dominant.

[0050] For these different types of trajectories, a transformation matrix Tf tuned for the most frequently followed trajectories may not be well suited: the transformation matrix Tf may be optimized for certain types of trajectories but not for others, or the transformation matrix Tf may be optimized for all possible trajectories, resulting in poor overall performance.

[0051] According to an embodiment of the invention, it is proposed to select the transformation values ​​of the transformation matrix Tf depending on the intended trajectory of the movable object O. In such an embodiment, the transformation values ​​are optimized depending on the intended trajectory rather than being optimized for one or more typical trajectories, and the transformation values ​​of the transformation matrix Tf are selected for a particular intended trajectory or type of trajectory.

[0052] Figure 7 shows an embodiment of a positioning system comprising a position control system PCS configured to select transformation values ​​based on a planned trajectory of the movable object O. In addition to the position control system PCS of Figure 3, the position control system PCS of Figure 7 comprises a data store DS in which a number of transformation matrices Tf1, Tf2, Tf3 with different transformation values ​​are stored, each of which is optimized for a particular trajectory or type of particular trajectory that the movable object O should follow.

[0053] For example, the data storage unit DS comprises a first transformation matrix Tf1 associated with a first predetermined trajectory of the movable object O in which the x-direction motion is dominant, a second transformation matrix Tf2 associated with a second predetermined trajectory of the movable object O in which the y-direction motion is dominant, and a third transformation matrix Tf3 associated with a third predetermined trajectory of the movable object O in which the x- and y-direction motions are balanced.

[0054] In use, one of the three transformation matrices Tf1, Tf2, Tf3 is selected in consideration of the planned trajectory. The planned trajectory may be matched to a particular type of trajectory corresponding to the transformation matrices Tf1, Tf2, Tf3 available in the data store DS. For example, the first transformation matrix Tf1 may be selected if the planned trajectory is a trajectory with dominant motion in the x-direction shown in FIG. 6. This transformation matrix Tf1 is used as the transformation matrix Tf in the position control system PCS.

[0055] In practice, the number of transformation matrices Tf1, Tf2, Tf3 that can be selected depending on the type of particular trajectory that the movable object O should follow may vary based on the type of trajectory to be followed and the desired performance of the transformation matrices.

[0056] In another embodiment, for each trajectory to be followed by the movable object O, a transformation matrix may be determined having transformation values ​​optimized for that particular trajectory. This transformation matrix could be calculated each time the movable object O follows a trajectory, but it may be more efficient to store the transformation matrix calculated once for a particular trajectory in the data store DS and select this transformation matrix from the data store DS each time the movable object O follows that particular trajectory. In this embodiment, the data store DS will contain, for each trajectory followed by the movable object O, a transformation matrix having transformation values ​​optimized specifically for that trajectory.

[0057] Figure 8 shows an alternative embodiment of a positioning system comprising a position control system PCS configured to adjust the transformation values ​​of the transformation matrix Tf, in use, based on one or more actual performance related parameters of the positioning system.

[0058] In addition to the control scheme of the positioning system shown in Fig. 3, the positioning system of Fig. 8 comprises a sensor SEN and a conversion value adjustment device TAD. The sensor SEN is configured to measure one or more actual performance-related parameters of the positioning system. The one or more performance-related parameters may comprise, for example, peak temperature, actual actuator currents in at least two actuators, peak actuator currents, peak actuator voltages, actuator availability, and / or tracking performance.

[0059] The measured performance-related parameters are input to a conversion value adjustment device TAD. The conversion value adjustment device TAD may adjust the conversion values, for example, to keep each of the measured performance-related parameters below a safety threshold and / or to keep the performance-related parameters at a desired level. For example, a sensor SEN may be provided to measure the peak temperature of all actuators ACT, and the conversion value adjustment device TAD may be configured to adjust the conversion values ​​to keep the actuators ACT at the same temperature.

[0060] The conversion value adjustment device TAD may be configured to adjust the conversion value periodically, for example every 1 or 2 seconds, or alternatively, the conversion value adjustment device TAD may be configured to adjust the conversion value when the measured performance-related parameter reaches a particular value.

[0061] By adjusting the transformation values ​​to the measured performance-related parameters, the transformation matrix Tf may automatically adapt to the behavior of the substrate support at different trajectories of the substrate support WT. This in-line adjustment of the transformation values ​​of the transformation matrix Tf may therefore be effectively used to provide optimal control for different trajectories of the substrate support WT, which may typically be used during an alignment phase of a lithographic apparatus.

[0062] In-line adjustment of the transformation values ​​of the transformation matrix Tf based on measured performance-related parameters during the exposure phase of the lithographic apparatus may be undesirable because adjusting the transformation values ​​may affect imaging quality. Therefore, to maintain constant imaging quality, the transformation value adjustment device TAD may be configured not to adjust the transformation values ​​during the exposure phase. Furthermore, the trajectory of the substrate support WT during the exposure phase is typically relatively similar, so there is little need to adjust the transformation values ​​during the exposure phase.

[0063] Additionally, adjusting the transformations during the alignment phase can result in performance variations over time until the positioning control system settles on the adjusted transformations, an effect that can be reduced by appropriately selecting the update rate of the transformations and / or by limiting the bandwidth of the transformation adjustment device TAD.

[0064] In the above-described position control system, the transformation values ​​of the transformation matrix are selected depending on the intended trajectory of the movable object and / or the transformation values ​​are adjusted in use depending on one or more actual performance-related parameters of the positioning system. The position control system may also be applied to any other over-actuated positioning system for movable objects, such as patterning device supports, movable objects in projection systems, and substrate supports applied in other processes, such as substrate measurement processes.

[0065] It should be noted that although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, the lithographic apparatus described herein may have other applications, including the manufacture of integrated optical systems, induction and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0066] Although embodiments of the invention are specifically referred to herein in the context of lithography apparatus, embodiments of the invention may also be applied to other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatus may be generally referred to as lithography tools. Such lithography tools may use vacuum conditions or atmospheric (non-vacuum) conditions.

[0067] 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, where the context permits, the invention is not limited to optical lithography and may also be used in other applications, such as imprint lithography.

[0068] Where the context allows, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Also, embodiments of the present invention may 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, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and the like. Furthermore, firmware, software, routines, and instructions may be described herein as performing certain actions. However, it should be understood that such description is merely for convenience, and that such actions actually occur when a computing device, processor, controller, or other device executes the firmware, software, routines, instructions, etc., which may cause actuators or other devices to interact with the physical world.

[0069] While specific embodiments of the present invention have been described above, it will be understood that the invention may be practiced otherwise than as described. The foregoing description is intended to be illustrative and not limiting. Thus, it will be apparent to those skilled in the art that changes may be made to the invention as described without departing from the scope of the claims that follow.

Claims

1. 1. A positioning system for positioning a movable object, comprising: a plurality of actuators configured to move the movable object in one or more degrees of freedom, the plurality of actuators comprising more actuators than the one or more degrees of freedom; a control system comprising: a controller that provides a control signal based on a set point and / or a control error; and a transformation matrix that transforms the control signal into actuator inputs for the plurality of actuators; the transformation matrix comprises a transformation value for each relationship between one of the control signals and one of the actuator inputs, the transformation value being selected in response to a planned trajectory of the movable object and / or the transformation value being adjustable in use in response to one or more actual performance related parameters of the positioning system. Positioning system.

2. the control system comprises a data store comprising a plurality of transformation matrices having different transformation values, the control system being configured to use one of the plurality of transformation matrices depending on a predetermined trajectory of the movable object. The positioning system of claim 1 .

3. The plurality of transformation matrices are a first transformation matrix associated with a first predetermined trajectory of the movable object having predominantly x-direction motion; a second transformation matrix associated with a second predetermined trajectory of the movable object having predominantly y-direction motion; a third transformation matrix associated with a third predetermined trajectory of the movable object that balances motion in the x and y directions; The positioning system of claim 2 .

4. the positioning system comprises one or more sensors for measuring the one or more actual performance-related parameters, and the control system is configured to adjust the conversion value based on the measured one or more actual performance-related parameters. The positioning system of claim 1 .

5. the transformation value is determined to optimize one or more performance-related parameters of the positioning system. A positioning system according to any one of claims 1 to 4.

6. the one or more performance-related parameters comprise actual actuator current, peak actuator current, peak actuator voltage, actuator availability, and / or tracking performance for each actuator; A positioning system according to any one of claims 1 to 5.

7. a predetermined trajectory of the movable object is represented by a series of set points for movement of the movable object; A positioning system according to any one of claims 1 to 6.

8. the positioning system comprises at least seven actuators for actuating the movable object in six degrees of freedom. A positioning system according to any one of claims 1 to 7.

9. the positioning system is configured to actuate the movable object in six degrees of freedom, and for each degree of freedom, at least two actuators of the plurality of actuators are configured to individually move the movable object in that degree of freedom. A positioning system according to any one of claims 1 to 8.

10. the movable object is an optical element in a projection system of a lithographic apparatus, a stage supporting a substrate, or a stage supporting a patterning device. A positioning system according to any one of claims 1 to 9.

11. 1. A method of positioning a movable object using a positioning system, comprising: providing a control signal based on the set point and / or control error; - transforming said control signals into actuator inputs using a transformation matrix, said transformation matrix comprising a transformation value for each relationship between one of said control signals and one of said actuator inputs, said transformation value being selected in response to a planned trajectory of said movable object and / or said transformation value being adjusted in use in response to one or more actual performance related parameters of said positioning system; using the actuator input to drive a plurality of actuators of the positioning system to move the movable object in one or more degrees of freedom, the plurality of actuators comprising more actuators than the one or more degrees of freedom. method.

12. the control system comprises a data store comprising a plurality of transformation matrices having different transformation values, the method comprising using one of the plurality of transformation matrices in response to a predetermined trajectory of the movable object. The method of claim 11.

13. The plurality of transformation matrices are a first transformation matrix associated with a first predetermined trajectory of the movable object having predominantly x-direction motion; a second transformation matrix associated with a second predetermined trajectory of the movable object having predominantly y-direction motion; a third transformation matrix associated with a third predetermined trajectory of the movable object that balances motion in the x and y directions; The method of claim 12.

14. measuring said one or more actual performance-related parameters; and adjusting the conversion value based on the measured one or more actual performance-related parameters. The method of claim 11.

15. determining the transformation value to optimize one or more performance-related parameters of the positioning system.

15. The method according to any one of claims 11 to 14. Positioning system.

16. the one or more performance-related parameters comprise actual actuator current, peak actuator current, peak actuator voltage, actuator availability, and / or tracking performance for at least two actuators; 16. The method according to any one of claims 11 to 15.

17. a predetermined trajectory of the movable object is represented by a series of set points for movement of the movable object; 17. The method of any one of claims 11 to 16.

18. the positioning system is configured to actuate the movable object in six degrees of freedom, and for each degree of freedom at least two actuators are configured to move the movable object individually in that degree of freedom.

18. The method of any one of claims 11 to 17.

19. the movable object is an optical element in a projection system of a lithographic apparatus, a stage supporting a substrate, or a stage supporting a patterning device.

19. The method of any one of claims 11 to 18.

20. the method is used in a lithography process comprising an exposure phase, and the transformation matrix and its transformation values ​​are not changed during the exposure phase.

20. The method of any one of claims 11 to 19.

Images