• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method for positioning an object by an electromagnetic motor which, in use, produces a plurality of primary forces and a pitch torque associated with the primary forces. The method includes a cycle which includes: determining the desired forces and torques for positioning the object, determining the primary forces to be generated by the motor, determine the pitch torque from either the primary forces or from the desired forces and torques, determine the desired signals for the motor to generate the primary forces. In a next cycle, prior to the determination of the primary forces, the desired forces and torques for positioning the object are modified using the pitch torque determined in the previous cycle of steps.
    公开号:NL1035987A1
    申请号:NL1035987
    申请日:2008-09-26
    公开日:2009-04-03
    发明作者:Henrikus Herman Marie Cox；Thomas Augustus Mattaar
    申请人:Asml Netherlands Bv；
    IPC主号:
    专利说明:

    METHOD FOR POSITIONING AN OBJECT BY AN ELECTROMAGNETIC ENGINE, INTERNSHIP EQUIPMENT AND LITHOGRAPHIC EQUIPMENT
    BACKGROUND
    Field of the Invention
    The present invention relates to a method for positioning an object, a stage apparatus and a lithographic apparatus.
    Description of the Related Art A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., including part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the "scanning" direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
    In order to accurately position the patterning device relative to the substrate, stage apparatuses equipped with one ore more electromagnetic motors are often applied.
    In general, such an electromagnetic motor comprises a first part including one or more coils which can be supplied with an electrical current and a second part co-operating with the first part to generate, in use, a force between both parts. The second part may e.g. comprise a 1D or 2D array of permanent magnets which generates an alternating magnetic field in a given direction or a given plane, the magnetic field interacting with the current carrying coils or the first part to generate the force between both parts.
    It is known that an electromagnetic motor which is used to position an object, eg a substrate table in a lithographic apparatus, may generate both a primary force, ie a force in a given direction to position the object, and, at the same time, produce a parasitic effect such as a pitch torque. Such a phenomenon is adequately described for a planar engine in e.g. EP 1 357 434 which is incorporated by reference in its entirety.
    Due to the pitch torque, the accurate positioning or the object can be compromised; the occurrence of the pitch torque may affect the positioning of the object that is to be positioned, even when the object is not directly coupled to the electromagnetic motor, eg by cross-talk between the electromagnetic motor and a fine positioning stage mounted between the object and the electromagnetic motor. Although the cross-talk to such a fine positioning stage can be low, there will always be, to some extend, a transmission of forces due to eg cables or hoses from the motor to the fine positioning stage, expect affection the positioning of the object .
    Due to the pitch torque, the relative position between both parts that constitute the electromagnetic motor may change. In general, both parts are kept separately by either a child or bearing such as an air bearing or, the engine itself may generate the required forces for maintaining a predetermined or preferred or minimum distance between both engine parts. The occurrence of the pitch torque may disturb this to such extend that both engine parts may come in contact with each other. This may, apart from resulting in a positioning error for the object, result in damaging either or both parts of the engine or result in contamination of the area in which the motor operates. An obvious solution to avoid such a collision between both engine parts is to increase the distance between both parts. However, the skilled person will appreciate that this would result in a reduced efficiency of the motor, since an increased distance between both parts will diminish the magnetic coupling between both parts. Apart from the reduction in efficiency, it will be clear that this approach will not satisfactorily solve the occurrence of the positioning error due to the pitch torque. It is therefore suggested in EP 1 357 434 to use a modified controller to generate the required motor forces, the modified controller to be arranged such that the effect of the pitch torque is substantially reduced. A drawback of the methods described in EP 1 357 434 is that they require an important amount of calculating power. The methods as suggested may be difficult to implement in a digital controller because the required calculations would be difficult to implement within one sample of the controller. Delaying the output of the controller, i.e. using several samples to conduct the calculations, may affect the stability or the control loop or the positional accuracy obtained.
    SUMMARY
    It is an object of the present invention to provide a solution which allows, at least partly, the compensation of the pitch torque or an electromagnetic motor but requires less computational effort than using known methods.
    According to an aspect of the present invention, there is provided a method for positioning an object by an electromagnetic motor which, in use, produces a variety of primary forces and a pitch torque associated with the primary forces, the method comprises a cycle of steps including - determining the desired forces and torques for positioning the object, - determining the primary forces to be generated by the motor, - determining the pitch torque from either the primary forces or the required forces, - determining the required signals for the motor to generate the primary forces, in, in a next cycle prior to the determination of the primary forces, the desired forces and torques for positioning the object are modified based on the pitch torque determined in the previous cycle of steps.
    According to a further aspect of the present invention, there is provided a stage apparatus for positioning an object including an electromagnetic motor for positioning the object which, in use, produces a variety of primary forces and a pitch torque associated with the primary forces, a control unit for controlling the electromagnetic motor, the control unit being arranged to perform the following cycle of steps: determining the required forces and torques to effect the positioning of the object, determining the primary forces to be provided by the electromagnetic motor based on the required forces and torques. determining the pitch torque that results from either the primary forces or the required forces and torques, determining the required signals for generating the primary forces, in a next cycle of steps, prior to the determination of the primary forces, the desired forces and torques for positioning the object are modified based on the pitch torque determined in the previous cycle of steps.
    According to yet another aspect of the present invention, there is provided a lithographic apparatus including an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate, the lithographic apparatus further comprising a stage apparatus for positioning the patterning device or the substrate, the stage apparatus including an electromagnetic motor for positioning the patterning device or the substrate which, in use, produces a variety of primary forces and a pitch torque associated with the primary forces, a control unit for controlling the electromagnetic motor, the control unit being arranged to perform the following cycle of steps: determining the required forces and torques to effect the positioning of the object, determining the primary forces to be provided by the electromagnetic motor based on the required forces and torques. determining the pitch torque that results from either the primary forces or the required forces and torques, determining the required signals for generating the primary forces, in a next cycle of steps, prior to the determination of the primary forces, the desired forces and torques for positioning the object are modified based on the pitch torque determined in the previous cycle of steps.
    LETTER DESCRIPTION OF THE DRAWINGS
    Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:
    Figure 1 depicts a lithographic apparatus according to an embodiment of the invention. Figure 2a schematically depicts a first flow chart or an embodiment of the present invention. Figure 2b schematically depicts a second flow chart or an embodiment of the present invention.
    Figure 3 schematically depicts an electromagnetic motor that can be applied in an embodiment of the present invention.
    Figure 4a schematically depicts a 2D permanent magnet array that can be applied in a planar motor that can be applied in a stage apparatus according to the present invention.
    Figure 4b schematically depicts a further 2D permanent magnet array that can be applied in a planar motor that can be applied in a stage apparatus according to the present invention.
    Figure 5a schematically depicts a top view of a planar engine that can be applied in an embodiment of the present invention.
    Figure 5b schematically depicts a possible layout of a forcer that can be applied in a planar motor that can be applied in an embodiment of the present invention.
    Figure 6 schematically depicts a stage apparatus according to an embodiment of the invention
    Figure 7 schematically depicts a further stage apparatus according to an embodiment of the invention
    Figure 8 schematically depicts a third flow chart or an embodiment of the present invention. DETAILED DESCRIPTION
    Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus includes an illumination system (illuminator) IL configured to condition a radiation beam B (eg UV radiation or any other suitable radiation), a mask support structure (eg a mask table) MT constructed to support a patterning device (eg a mask) MA and connected to a first positioning device PM configured to accurately position the patterning device in accordance with certain parameters. The apparatus also includes a substrate table (eg a wafer table) WT or "substrate support" constructed to hold a substrate (eg a resist-coated wafer) W and connected to a second positioning device PW configured to accurately position the substrate in accordance with certain parameters. The apparatus further includes a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. including one or more dies) or the substrate W.
    The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination of, for directing, shaping, or controlling radiation.
    The mask support structure supports, i.e. bears the weight of, the patterning device. It holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is a hero in a vacuum environment. The mask support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The mask support structure may be a frame or a table, for example, which may be fixed or movable as required. The mask support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms "reticle" or "mask" may be considered synonymous with the more general term "patterning device."
    The term "patterning device" used should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section so as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.
    The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift, and attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.
    The term "projection system" used should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, 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" may also be considered as synonymous with the more general term "projection system".
    As here depicted, the apparatus is of a transmissive type (e.g., employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g., employing a programmable mirror array or a type referred to above, or employing a reflective mask).
    The lithographic apparatus may be of a type having two (dual stage) or more substrate tables or "substrate supports" (and / or two or more mask tables or "mask supports"). In such "multiple stage" machines the additional tables or supports may be used in parallel, or preparatory steps may be carried out on one or more tables or supports while one or more other tables or supports are being used for exposure.
    The lithographic apparatus may also be a type of at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system and the substrate. Liquid immersion may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques can be used to increase the numerical aperture of projection systems. The term "immersion" as used does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that a liquid is located between the projection system and the substrate during exposure.
    Referring to figure 1, the illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to be part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD including, for example, suitable directing mirrors and / or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.
    The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) or the intensity distribution in a pupil plane or the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.
    The radiation beam B is an incident on the patterning device (e.g., mask MA), which is a hero on the mask support structure (e.g., mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which is the beam onto a target portion C or the substrate W. With the aid of the second positioning device PW and position sensor IF (eg an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, eg so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioning device PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the mask MA with respect to the path of the radiation beam B, eg after mechanical retrieval from a mask library, or during a scan. In general, movement of the mask table MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioning device PM. Similarly, movement of the substrate table WT or "substrate support" may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the mask table MT may be connected to a short-stroke actuator only, or may be fixed. Mask MA and substrate May be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one that is provided on the mask MA, the mask alignment marks may be located between the dies.
    The depicted apparatus could be used in at least one of the following modes: 1. In step mode, the mask table MT or "mask support" and the substrate table WT or "substrate support" are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (ie a single static exposure). The substrate table WT or "substrate support" is then shifted in the X and / or Y direction so that a different target portion can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. 2. In scan mode, the mask table MT or "mask support" and the substrate table WT or "substrate support" are scanned synchronously while a pattern is imparted to the radiation beam is projected onto a target portion C (ie a single dynamic exposure) . The velocity and direction of the substrate table WT or "substrate support" relative to the mask table MT or "mask support" may be determined by the (de-) magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) or the target portion in a single dynamic exposure, whereas the length of the scanning motion has the height (in the scanning direction) of the target portion. 3. In another mode, the mask table MT or "mask support" is kept essentially stationary holding a programmable patterning device, and the substrate table WT or "substrate support" is moved or scanned while a pattern is projected onto the radiation beam a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or "substrate support" or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array or a type as referred to above.
    Combinations and / or variations on the modes described above or use or entirely different modes or use may also be employed.
    Figure 1 further depicts a control unit CU arranged to control either one or both of the positioning devices PM and PW. The positioning devices PM and PW may comprise one or more electromagnetic motors to enable the positioning of the patterning device MA resp. the substrate W. As an example, the positioning device PM may include a linear motor as further described in figure 3 for positioning the mask table, the positioning device PW may eg include a planar motor as further described in figures 4a, 4b and 5a, 5b. The control unit CU is further arranged to perform the following cycle of steps: - determining the desired forces and torques for positioning the object (ie either the mask table or the substrate table), - determining the primary forces to be generated by the electromagnetic motor (ie either the motor or the positioning device PM or the motor or the positioning device PW or both), - determining a pitch torque that is, in use, generated by the electromagnetic motor from either the primary forces or the required forces, - determining the required signals for the motor to generate the primary forces, in a next cycle prior to the determination of the primary forces, the desired forces and torques for positioning the object are modified using the pitch torque determined in the previous cycle of steps. By doing so, a simple way of addressing the effect of a pitch torque or an electromagnetic motor in a positioning device is obtained.
    According to an aspect of the present invention, there is provided a method of controlling the position of an object by an electromagnetic motor. The method can both be applied for controlling linear motors or planar motors, examples of which are described below. The control method can be described by the flow chart as shown in figure 2a or 2b.
    Figure 2a schematically depicts a first step 100 or determining the desired (or required) forces and torques for positioning an object. This step 100 can e.g. include a comparison between a measured position and a desired position. Alternatively, or in addition, this step can also take an account for an output signal or a controller (see further on). The step of determining the desired forces and torques for positioning the object can further take into account the physical parameters of the object to be displaced, such parameter can eg be the weight of inertia of the object, but also parameters of the environment of the object can be tasks in to account. As a result, or this step, the desired forces and torques are obtained which, when applied to the object, would result in the required positioning or the object or would result in a correction of the position. In a next step 110, the desired forces are transformed into the primary forces that need to be generated by the electromagnetic motor. This transformation takes into account the current position and layout of the electromagnetic motor in relation to the object that is displaced.
    In case an electromagnetic motor is supplied with an electric current or a set of electric currents (eg a two or three phase current system) it may generate a force in a given direction which can be maintained substantially constant when the motor is displaced in said given direction by a proper commutation or the supplied current. This force is referred to as the primary force or the electromagnetic motor. The transformation that is done in the second step 110 therefore transforms the required forces and torques to position the object into forces which can be generated by the motor or motors as applied. This process is also referred to as Gain Balancing, a more detailed description of this process, e.g. found in EP 1 357 434, incorporated by reference. It is important to note in the method as described by the present invention, the Gain Balancing does not take into account any spurious effects of the motor such as an occurring pitch torque. The Gain Balancing as conducted in step 110 or figure 2a only takes into account the primary forces that can be generated by the electromagnetic motor. The occurring spurious torques (parasitic torques which would occur when the primary forces are generated by the engine) are not incorporated in the Gain Balancing step. It can be noted that it would be possible to take the parasitic torques into account during the Gain Balancing step (e.g., the second embodiment as described in EP 1 357 434), but this has the following drawback:
    The computational effort for performing the Gain Balancing step increases: It can be shown that the parasitic torques (ie the pitch torque) that occur when a linear or planar motor displaces in a given direction do not remain constant but depend on the relative position of both co-operating parts of the motor (ie the first part including one or more coils which can be supplied with an electrical current and the second part co-operating with the first part which, in general, will include an array or altematingly polarized permanent magnets As a consequence, since the parasitic torque depends on the relative position of both engine parts, this relative position needs to be known and tasks into account in the Gain Balancing process. controller.
    It is therefore advantageous not to incorporate the effect of the pitch torque during the Gain Balancing process.
    In a next step or an embodiment of the method according to the invention, the primary forces as determined by the Gain Balancing process are used to determine the pitch torque that is associated with these forces. This calculation can e.g. be based on the relative position between both engine parts, this relative position can be determined in different ways, examples of which are described below. At the same time as the pitch torque is determined, the signals for powering the electromagnetic motor can be determined based on the required primary forces, 130. This process may involve the determination of the required commutation angle for the current supplied to the coil or coils of the motor. This process can also be based on the relative position between both engine parts. The relative position between both engine parts need not actually measured by a position measurement system arranged between both parts, the relative position can also be derived from a position measurement or one of the engine parts, in case the other engine part remains stationary.
    In order to take account of the pitch torque that is calculated from the primary forces, the control method according to the present invention uses the calculated pitch torque to modify the required forces and torques for positioning the object, prior to the calculation of the primary forces . This is depicted in figure 2a by the feedback loop 140.
    It can be further mentioned that the present invention advantageously provides a possibility to assess the calculated pitch torque for diagnostic purposes, as the calculated pitch torque is available as a signal in the controller. Using data-tracing, this signal can be visualized and analyzed, unlike in the second embodiment or EP 1 357 434.
    In order for this modification not to delay the process to obtain the required signals to generate the primary forces, the pitch torque as calculated in a previous step is used rather than combining the calculated pitch torque with an earlier set of primary forces, as eg done in the first embodiment as described in EP 1 357 434. The method as described can be surprisingly good results in compensation for the pitch torque while being easy to implement in a digital controller. Compared to known methods, the described method required less computational power.
    In an embodiment of the present invention, the modification consists of subtracting the calculated pitch torque from the required forces and torques, prior to the calculation of the primary forces.
    The Gain Balancing case is performed without taking into account the parasitic effects such as the pitch torque, the Gain Balancing process can be expressed as a matrix multiplication in which the matrix elements can be constant. So, by performing a matrix multiplication on the desired forces and torques, the primary forces for the electromagnetic motor can be obtained. In such a situation, it will be clear to the skilled person that the pitch torque associated with the primary forces (or forces) can be equally obtained from the desired forces, as the primary forces can be expressed as a function of the desired forces. Figure 2b describes the flow chart for this situation. Based on the calculated desired forces for positioning the object, the. pitch torque associated with these forces is calculated, 200. The calculated pitch torque can then, as in the process of figure 2a be used, in a next sample, to modify the desired forces and torques, prior to the determination of the primary forces of the motor, as indicated by the arrow 210.
    The method as described can e.g. be applied in a stage apparatus arranged to position an object in e.g. a lithographic apparatus. In such an apparatus, both the patterning device and the substrate (on which a pattern of the patterning device is projected or printed) need accurate positioning.
    The following figures show, by way of example, some electromagnetic motor for which the control method can be applied.
    Figure 3 shows schematically a cross-sectional view of an electromagnetic motor including a first part 300, said part including a first coil set (or forcer) 310 and a second coil set (or forcer) 320. the first part is further arranged to co-operate with a second part 330 including an array of permanent magnets 340 (or which the polarization is indicated by the arrows inside the magnets), the array of magnets being mounted to a member 350 which, preferably, comprises a magnetically conductive material such as Iron. In order to generate a force between both parts, the coil sets (or forcers) can be supplied with an electric current or currents. In the arrangement as depicted, each coil set comprises three coils which can be supplied from e.g. a three-phase power supply. When the appropriate commutation angle is applied for the currents, one can ensure that both parts displace relative to each other in the Y-direction a constant force in the Y-direction can be generated. This Y-force is therefore considered a primary force of the motor. It can be further noted that the motor as shown can also be applied when the appropriate commutation is applied, generate a force in the Z direction which can be maintained substantially constant when the first part 300 displays relative to the second part 330 in the Y- direction. This force therefore also includes a primary force of the motor. The primary forces of the motor as shown, are actually the resulting forces of the individual forces generated by the different coils in each coil set. As these individual forces are not constant when both engine parts displace relative to each other (since both the current in the individual coils and the interaction with the magnetic field changes due to the displacement), a position dependent torque component can also be generated in addition to the resulting force in the Y-direction or Z-direction. This torque is schematically depicted in figure 3 by the arrow 360 and is a torque about the X-axis, which is perpendicular to the YZ plane of the figure. As can be shown, the torque can be expressed as a function of the generated primary force and the relative position between both engine parts.
    In case the electromagnetic motor comprises more that one forcer, as is the case in figure 3, it will be clear that each forcer may generate, during operation, such a parasitic torque. The resulting torque or all forcers is actually the pitch torque that can, at least partly, be corrected by the process as shown in figures 2a or 2b.
    The method of controlling the position of an object may also be applied in a planar motor as described in EP 1 357 434. Such a planar motor can be viewed as a 2D version of the motor as depicted in figure 3. In addition to forcers arranged to generate forces in the Y-direction, such a planar motor comprises one or more forcers arranged to generate forces in the X-direction, which, in general, is perpendicular to the Y-direction. In order to generate the force (or forces) in the X-direction, the permanent magnet array or the planar motor is arranged in such a manner that an alternating magnetic field is generated both in the X- and Y-direction. This can be obtained by a checkerboard pattern of permanent magnets 400 as shown in figure 4. References N and S inside the magnets indicate the polarization (North or South) or the different magnets 410. As will be appreciated by the skilled person, the efficiency of the planar motor can be improved by using a so-called 2D Halbach array for the permanent magnet assembly. Such a magnet configuration is shown in Figure 4b with magnets 450, 452, 454 and 456 permanent magnets which are polarized as indicated by the arrows inside the magnets. Figure 5a schematically shows a top view of a planar engine that can be applied in the present invention. Figure 5a shows the 2D array of permanent magnets 500 together with the forcer 510 of the motor. The forcer of the planar motor as shown comprises a variety of coil sets 520 arranged to generate a primary force in the direction as indicated by the arrows 530. Figure 5a further indicates the magnetic pole pitch τ describing the magnetic period of the permanent magnet array . Figure 5b shows an alternative arrangement or coil sets 550 for a forcer 560 or a planar motor.
    As already mentioned above, the pitch torque as generated by the forcer or forcers of the electromagnetic motor depends on the relative position of both motor parts and can be expressed as a function of the primary force (or forces) or the motor and the relative position or both motor parts. One way to obtain this information is to provide a measurement system between both parts of the engine to measure the relative position. As an example or such a measurement system, the forcer part of the motor (including the coil set or coil sets) can be provided with one or more Hall sensors arranged to measure the magnetic field or the permanent magnet array (or assembly) . The output signal of the Hall Sensor (s) can provide the required position information to allow the determination of the pitch torque which needs to be corrected or tasks into account. Alternative measurement systems such as encoder based measurement systems may be equally applied.
    In case the motor is applied in a stage apparatus for positioning an object, a position measurement system may already be present for measuring the position of the object. Such a measurement system can e.g. include an interferometer system or an encoder based system and can e.g. allow measuring the position of the object relative to a reference of the apparatus. Combined with positional information relative to the forcer part of the motor and positional information regarding the position of the permanent magnet part relative to the reference, the relative position of both motor parts can be obtained. Such a set-up is illustrated in figure 6. Figure 6 schematically depicts a stage apparatus 600 mounted to a base 610. The stage apparatus comprises an electromagnetic motor 620 including a first part 630 (eg a forcer such as depicted in figures 3, 5a or 5b), arranged to co-operate with a second part 640 (which is mounted to the base 610 and which can be a permanent magnet array as shown in figures 3, 4a, 4b or 5a)) to displace an object 650 ( eg a substrate table or a lithographic apparatus) in the Y-direction relative to a reference 660 of the apparatus. In addition, the apparatus comprises a position measurement system 670 for measuring the position of the object 650 relative to the reference 660. In case the position of the second part 640 or the electromagnetic relative to the reference 660 is fixed, the position measurement of the object table can be applied to determine the position of the first part of the electromagnetic motor relative to the second part, which position information may be required to determine the pitch torque generated by the electromagnetic motor.
    In apparatus requiring a high positioning accuracy of an object (such as the positioning of a mask table or substrate table) in a lithographic apparatus, a balance mass arrangement is often applied to mitigate or avoid excitation or critical parts by the reaction forces or stage positioning devices. Such a balance mass arrangement is schematically depicted in figure 7. Corresponding reference numbers as applied in figure 6 are used to indicate corresponding part of the stage apparatus. In contrast to figure 6, however, the second part 640 of the electromagnetic motor 620 is not mounted to the base 610 but is arranged in such a manner that it is displaceable (indicated by the arrow 690), substantially without friction relative to the base 610, at least in a direction corresponding to the direction of a primary force of the motor. By doing so, the reaction force or the primary force, which acts on this part 640 will cause this part to displace in the opposite direction as the first part 630 of the motor. By such an arrangement, excitation or critical machine parts by the reaction force can be avoided or mitigated.
    In order to determine the position of the first motor relative to the second part in such a balance mass arrangement, a second measurement system 680 can be applied which is eg arranged to determine the position of the second part 640 of the electromagnetic motor 620 relative to the reference 660. Combined with the position information obtained from the position measurement system 670, the position of the first motor part relative to the second can be obtained and used to determine the pitch torque of the motor.
    Figure 8 schematically depicts a more detailed flow chart of the method according to the present invention in which the use of the position measurement to calculate the pitch torque is indicated by the arrow 150. In addition, figure 8 schematically shows a controller 160 which can include a feedback loop 170 and a feedforward loop 180. The controller can use a set-point 185 of the object to be combined with a feedback of the position measurement 190 of the object. Note that this position measurement of the object may also be used in the calculation of the pitch torque (as described in figure 7), as indicated by the dotted line 188.
    The method for taking into account the effect of a pitch torque or an electromagnetic motor, by eg figures 2a, 2b or 8 can be further improved as follows: As described above, the calculated pitch torque is used in the described method to modify the desired forces and torques. The pitch torque that is used for this is however calculated in a previous sample. As such, the calculated pitch torque does not take into the actual displacement account or the motor that may occur. This displacement can be tasks into account as follows: rather than calculating the pitch torque based on the current relative position of both motor parts, the pitch torque can be calculated based on an estimate of the relative position of both motors in the next sample. This estimate can be obtained from the current relative position of both parts combined with e.g. information on the actual velocity of the motor. Based on the current velocity and knowing the time interval between two samples, one can estimate the position of the motor in the next sample and use this position to calculate the pitch torque. Instead of using the actual velocity, which can be obtained from a measurement, the velocity can be obtained from two or more position measurements. Alternatively, in case the set-point for the positioning also includes a velocity setpoint, this velocity set-point can be applied to obtain an estimate of the relative position of both motor parts in the next sample. In addition to using the velocity to obtain an improved position reference for calculating the pitch torque, the acceleration of the motor can be used to provide a further improvement.
    Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms "wafer" or " those "may be considered as synonymous with the more general terms" substrate "or" target portion ", respectively. The substrate referred to may be processed, before or after exposure, in for example a track (a tool that typically applies to a layer of resist to a substrate and develops the exposed resist), a metrology tool and / or an inspection tool. Where applicable, the disclosure may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so the term substrate used may also refer to a substrate that already contains multiple processed layers.
    The terms "radiation" and "beam" used include and compass all types of electromagnetic radiation, including ultraviolet (UV) radiation (eg having a wavelength of or about 365,248,193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (eg having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.
    The term "lens", where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.
    While specific expired or the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (eg semiconductor memory, magnetic or optical disk) having such a computer program stored therein. Other aspects of the invention are set out as in the following numbered clauses: 1. Method for positioning an object by an electromagnetic motor which, in use, produces a variety of primary forces and a pitch torque associated with the primary forces, the method comprises a cycle of steps - determining the desired forces and torques for positioning the object, - determining the primary forces to be generated by the motor, - determining the pitch torque from either the primary forces or from the desired forces and torques, - determining the required signals for the motor to generate the primary forces, in a next cycle prior to the determination of the primary forces, the desired forces and torques for positioning the object are modified using the pitch torque determined in the previous cycle of steps. 2. Method according to clause 1 prior to the determination of the primary forces, the desired forces and torques are modified by subtracting the pitch torque determined in the previous cycle of steps. 3. Method according to clause 1 or 2 regarding the pitch torque is further determined on the basis of a position measurement of the electromagnetic motor. 4. Method according to clause 3 according to the pitch torque is further determined on the basis of a velocity measurement or a velocity set-point of the object. 5. stage apparatus for positioning an object including an electromagnetic motor for positioning the object which, in use, produces a variety of primary forces and a pitch torque associated with the primary forces, a control unit for controlling the electromagnetic motor, the control unit being arranged to perform the following cycle of steps: determining the required forces and torques to effect the positioning of the object, determining the primary forces to be provided by the electromagnetic motor based on the required forces and torques. determining the pitch torque that results from either the primary forces or the required forces and torques, determining the required signals for generating the primary forces, in a next cycle of steps, the primary forces are determined based on the required forces and torques minus the calculated pitch torque. 6. Stage apparatus according to clause 5 according to the various forces of primary forces, in use, generated by a respective various or coil sets, each producing at least one primary force in a given direction and a pitch torque associated with the primary force. 7 Stage apparatus according to clause 6 The electromagnetic motor comprises a planar motor arranged to position the object in a first direction and a second direction. 8 Stage apparatus according to clause 7 is a permanent magnet array or the planar motor, in use, displaceable substantially without friction in both the first and the second direction. 9 Stage apparatus according to clause 8 where a position of the permanent magnet array is used to determine the desired motor signals and the pitch torque. 10 Stage apparatus according to any of clauses 6 to 9 regarding the pitch torque is further determined on the basis of a position measurement of the electromagnetic motor. 11 Stage apparatus according to clause according to clause 10 regarding the pitch torque is further determined on the basis of a velocity measurement or a velocity set-point of the object. 12. A lithographic apparatus including: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate, the lithographic apparatus further comprising a stage apparatus according to any of the clauses 5 to 11 for positioning the support or the substrate table.
    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 or the clause set out herehere.
    权利要求:
    Claims (1)
    [1]
    Method for positioning an object by means of an electromagnetic motor which is adapted to generate a plurality of primary forces and a pitch torque related to the primary forces, the method comprising a cycle with the following steps: determining desired forces and couples for positioning the object; - determining primary forces to be generated by the engine; - determining the pitch torque based on the primary forces or the desired forces and couples; and - determining desired signals for the motor for generating the primary forces, wherein, in a later cycle, before the primary forces are determined, the desired forces and couples for positioning the object are adjusted on the basis of the a pitch torque determined in an earlier cycle.
    类似技术:
    公开号 | 公开日 | 专利标题
    US8982327B2|2015-03-17|Method for positioning an object by an electromagnetic motor, stage apparatus and lithographic apparatus
    US7468589B2|2008-12-23|Lithographic apparatus having a controlled motor, and motor control system and method
    US9261799B2|2016-02-16|Movable support, position control system, lithographic apparatus and method of controlling a position of an exchangeable object
    US7348752B1|2008-03-25|Stage apparatus and lithographic apparatus
    US8885147B2|2014-11-11|Lithographic apparatus and device manufacturing method
    JP4425256B2|2010-03-03|Lithographic apparatus and motor
    US8553199B2|2013-10-08|Lithographic apparatus and device manufacturing method
    JP6576964B2|2019-09-18|Linear reluctance actuator and lithographic apparatus
    US8355115B2|2013-01-15|Positioning system, method, and lithographic apparatus
    US20130314684A1|2013-11-28|Lithographic Apparatus and Device Manufacturing Method
    US10437160B2|2019-10-08|Lorentz actuator, object positioning system, lithographic apparatus and Lorentz actuator operating method
    NL2010529A|2013-09-30|Substrate table system, lithographic apparatus and substrate table swapping method.
    US9293951B2|2016-03-22|Lithographic apparatus and lorentz actuator
    NL2006149A|2011-09-13|Lithographic apparatus and method for correcting.
    同族专利:
    公开号 | 公开日
    JP2009089595A|2009-04-23|
    US8982327B2|2015-03-17|
    JP4990864B2|2012-08-01|
    US8102513B2|2012-01-24|
    US20090097003A1|2009-04-16|
    US20120092641A1|2012-04-19|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    JPH10201272A|1997-01-17|1998-07-31|Toshiba Mach Co Ltd|Method for suppressing resonance at motor servo system|
    JP4182311B2|1999-11-11|2008-11-19|株式会社安川電機|Linear motor control method and apparatus|
    EP1357429A1|2002-04-23|2003-10-29|ASML Netherlands B.V.|Lithographic apparatus and device manufacturing method|
    EP1357434A1|2002-04-23|2003-10-29|ASML Netherlands B.V.|Lithographic apparatus and device manufacturing method|
    US6998737B2|2003-10-09|2006-02-14|Asml Netherlands B.V.|Lithographic apparatus and device manufacturing method|NL2007279A|2010-09-28|2012-03-29|Asml Netherlands Bv|Method for calibrating a target surface of a position measurement system, position measurement system, and lithographic apparatus.|
    US8593016B2|2010-12-03|2013-11-26|Sri International|Levitated micro-manipulator system|
    CN103703523B|2011-04-13|2015-08-26|巨石风力股份有限公司|For permanent magnet flux concentration structure, manufacture the method for this structure and comprise the machine of this structure|
    NL2008696A|2011-05-25|2012-11-27|Asml Netherlands Bv|A multi-stage system, a control method therefor, and a lithographic apparatus.|
    CN102607391B|2012-03-01|2014-06-18|清华大学|Method for measuring displacement of planar motor rotor|
    CN105723179B|2013-10-18|2019-05-31|上海交通大学|Active position coder and its operating method|
    US20150241525A1|2013-12-10|2015-08-27|Nikon Corporation|Dynamic Correction to Remove the Influence of Motor Coil Flux on Hall Sensor Measurement|
    US9899886B2|2014-04-29|2018-02-20|Boulder Wind Power, Inc.|Devices and methods for magnetic flux return optimization in electromagnetic machines|
    CN108350976A|2015-11-05|2018-07-31|Asml荷兰有限公司|Magnet array, electric wire coil apparatus, shift system, lithographic equipment and device making method|
    KR102070756B1|2018-03-15|2020-01-29|이노6 주식회사|Multi axis stage|
    US11223249B2|2020-05-13|2022-01-11|Kobe Steel, Ltd.|Electric motor|
    JP2020202746A|2020-09-18|2020-12-17|株式会社神戸製鋼所|Electric motor|
    法律状态:
    2009-06-02| AD1A| A request for search or an international type search has been filed|
    优先权:
    申请号 | 申请日 | 专利标题
    US96051507P| true| 2007-10-02|2007-10-02|
    US96051507|2007-10-02|
    [返回顶部]