NL2010565A - Lithography apparatus and device manufacturing method. - Google Patents

Description

LITHOGRAPHY APPARATUS AND DEVICE MANUFACTURING METHOD

Field

[0001] The present invention relates to a lithographic apparatus and a device manufacturing method.

Background

[0002] 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 that instance, 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. comprising 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. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, 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.

[0003] In a measurement phase, during which the substrate surface is characterized, and an exposure phase, during which the desired pattern is imaged onto the substrate by the patterned radiation beam, the substrate is supported on a substrate table that is moveable relative to the projection system. A drive system is provided for driving the movement of the substrate table.

[0004] In order to minimize the distance travelled by the substrate table when switching between the measurement phase and the exposure phase, and when unloading and loading a substrate to/from the substrate table, it has been found convenient in prior art systems to use so-called planar motors to drive movement of the substrate table. These planar motors are implemented by attaching coils to the substrate table and permanent magnets to a body beneath the substrate table. The coils are driven in such a way as to cause the required accelerations and decelerations associated with the intended movement of the substrate table.

The coils and permanent magnets can also be configured to cause levitation of the substrate table above the permanent magnets.

[0005] The planar motor configuration provides for movement that is relatively unconstrained spatially, and any connections between the substrate table and other parts of the lithography apparatus can stay constant during transfer of the substrate table from the measurement phase to the exposure phase; there is no need for the substrate table to be transferred from one drive system to another drive system, for example.

[0006] However, such planar motors are relatively inefficient, requiring a large amount of power to achieve the movement required. This increases cost and may limit the extent to which such systems can be used for processing larger substrates, such as 450mm diameter substrates and/or increasing throughput. Larger substrates will require larger substrate tables and therefore larger forces. Increasing throughput will require larger accelerations and therefore larger forces.

[0007] Larger substrate tables may need to be made thicker to achieve satisfactory stiffness. Increasing the height of the substrate table will tend to increase the size of torques applied to the substrate table during acceleration or deceleration of the substrate table. The increased size of the substrate table will also increase the weight of the substrate table, further increasing the size of torques applied to the substrate table. Where such torques are resisted by the planar motors, higher driving currents may be needed, leading to greater losses and/or higher heat loads.

Summary

[0008] It is desirable to provide a more efficient way of driving movement of the substrate table.

[0009] According to an embodiment, there is provided a lithographic apparatus comprising: a carrier for supporting a substrate, a metrology element or a patterning device; a projection system arranged to transfer a pattern from the patterning device onto the substrate; a drive system for moving the carrier relative to the projection system in a plane defined by reference to orthogonal axes X and Y within the plane and axis Z perpendicular to the plane, wherein the drive system comprises: a short-stroke stage for supporting the carrier; and a long-stroke stage for supporting the short-stroke stage, wherein: the largest cross-section of the long-stroke stage perpendicular to Z has a larger area than the largest cross-section of the short-stroke stage perpendicular to Z.

[0010] According to an embodiment, there is provided a lithographic apparatus comprising: a carrier for supporting a substrate, a metrology element, or a patterning device; a projection system arranged to transfer a pattern from the patterning device onto the substrate; a drive system for moving the carrier relative to the projection system in a plane defined by reference to orthogonal axes X and Y within the plane and axis Z perpendicular to the plane, wherein: the drive system comprises: a plurality of first driver modules configured to apply forces to the carrier within the X-Y plane and in the Z direction; and one or more second driver modules configured to apply forces to the carrier within the X-Y plane only.

[0011] According to an embodiment, there is provided a device manufacturing method comprising: providing a carrier for supporting a substrate, a metrology element, or a patterning device; transferring a pattern onto a substrate using a projection system; and using a drive system to move the carrier relative to the projection system in a plane defined by reference to orthogonal axes X and Y within the plane and axis Z perpendicular to the plane, wherein: the drive system comprises: a short-stroke stage for supporting the carrier; and a long-stroke stage for supporting the short-stroke stage, wherein: the largest cross-section of the long-stroke stage perpendicular to Z has a larger area than the largest cross-section of the short-stroke stage perpendicular to Z.

[0012] According to an embodiment, there is provided a device manufacturing method comprising: providing a carrier for supporting a substrate, a metrology element, or a patterning device; transferring a pattern onto a substrate using a projection system; and using a drive system to move the carrier relative to the projection system in a plane defined by reference to orthogonal axes X and Y within the plane and axis Z perpendicular to the plane, wherein: a plurality of first driver modules of the drive system are used to apply forces to the carrier within the X-Y plane and in the Z direction; and one or more second driver modules of the drive system are used to apply forces to the carrier within the X-Y plane only.

Brief Description of the Drawings

[0013] 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:

[0014] Figure 1 depicts a lithographic apparatus according to an embodiment of the invention;

[0015] Figure 2 is a schematic top view of a lithographic apparatus having first and second carriers each mounted on long- and short-stroke stages according to an embodiment of the invention;

[0016] Figure 3 is a schematic side sectional view of a substrate table comprising a long-stroke stage extending laterally around a short-stroke stage according to an embodiment of the invention;

[0017] Figure 4 is a schematic side sectional view of a substrate table comprising a long-stroke stage extending beyond the short-stroke table along X or Y according to an embodiment of the invention;

[0018] Figure 5 is a schematic side sectional view of a substrate table comprising a long-stroke stage having peripheral regions extending towards the projection system according to an embodiment of the invention;

[0019] Figure 6 is a schematic side sectional view of a substrate table comprising a long-stroke stage having a center of mass that is closer to the projection system than the center of mass of the short-stroke stage according to an embodiment of the invention;

[0020] Figure 7 depicts a first arrangement of X- and Y-driver modules according to an embodiment of the invention;

[0021] Figure 8 depicts a second arrangement of X- and Y-driver modules according to an embodiment of the invention;

[0022] Figure 9 depicts a third arrangement of X- and Y-driver modules according to an embodiment of the invention;

[0023] Figure 10 illustrates the distribution of forces along Z during diagonal acceleration along (+X,+Y) according to an embodiment of the invention;

[0024] Figure 11 illustrates the distribution of forces along Z during diagonal acceleration along (+X,-Y) according to an embodiment of the invention;

[0025] Figure 12 illustrates the distribution of forces along Z during diagonal acceleration along (-X,-Y) according to an embodiment of the invention;

[0026] Figure 13 illustrates the distribution of forces along Z during diagonal acceleration along (-X,+Y) according to an embodiment of the invention;

[0027] Figure 14 depicts a fourth arrangement of X- and Y-driver modules according to an embodiment of the invention;

[0028] Figure 15 is a schematic illustration of a system for controlling the shape of the long-stroke stage using X- and Y-driver modules according to an embodiment of the invention.

Detailed Description

[0029] Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus comprises: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or DUV radiation).

a support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters; a substrate table (e.g. a wafer table) WT constructed to hold a substrate (e.g. a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate in accordance with certain parameters; and a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies) of the substrate W.

[0030] 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 thereof, for directing, shaping, or controlling radiation.

[0031] The 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 held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The 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” herein may be considered synonymous with the more general term “patterning device.”

[0032] The term “patterning device” used herein 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 such 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.

[0(133] 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.

[0034] The term “projection system” used herein 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” herein may be considered as synonymous with the more general term “projection system”.

[0035] 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 of a type as referred to above, or employing a reflective mask).

[0036] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more mask tables). In such “multiple stage” machines the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure.

[0037] The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0038] 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 form 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 comprising, 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.

[0039] The illuminator IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as -outer and -inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may comprise 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.

[0040] The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. Having traversed the patterning device (e.g. mask) 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 position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in Figure 1) can be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure (e.g. 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 positioner PM. Similarly, movement of the substrate table WT 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 support structure (e.g. mask table) MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device (e.g. mask) MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks PI, 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 die is provided on the patterning device (e.g. mask) MA, the patterning device alignment marks may be located between the dies.

[0041] The depicted apparatus could be used in at least one of the following modes: 1. In step mode, the support structure (e.g. mask table) MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C 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 support structure (e.g. mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (e.g. mask table) MT 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) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion.

3. In another mode, the support structure (e.g. mask table) MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto 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 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 of a type as referred to above.

[0042] Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

[0043] In the following description, motion of the substrate table WT (or carrier, long-stroke stage, short-stroke stage, etc.) is described relative to a Cartesian coordinate system in which the X- and Y-axes lie in a plane parallel to that of the substrate W and upper surface of the substrate table WT, and the Z-axis is aligned with the final element of the projection system PS (perpendicular to the X- and Y-axes) and approximately parallel to the direction of incidence of the patterned radiation beam on the substrate W.

[0044] As mentioned above, during exposure of the substrate W by the patterned radiation beam (the exposure phase), it is necessary to move the substrate W relative to the projection system PS.

[0045] Figure 2 is a schematic top view of two substrate tables WT configured to move relative to a balance mass 5. Figure 3 is a side sectional view of one of the substrate tables WT along line A-A.

[0046] In the embodiment shown, each of the two substrate tables WT is capable of supporting a different substrate W. The substrate tables WT can be moved independently of each other within the X-Y plane. In an embodiment the two substrate tables WT are configured to allow a first substrate to be exposed while metrology is performed on a second substrate prior to exposure of the second substrate.

[0047] In an embodiment, each substrate table WT comprises a short-stroke module 7 and a long-stroke module 11. The short-stroke module 7 comprises a short-stroke stage 8 for supporting the substrate W. A short-stroke stage driver 9 drives movement of the stage 8 relative to the long-stroke module 11. The short-stroke module 7 provides for fine positioning of the substrate W. The long-stroke module 11 comprises a long-stroke stage 6 for supporting the short-stroke module 7. A long-stroke stage driver 16,18 drives movement of the stage 6 relative to an external reference frame, such as the projection system. The long-stroke module 11 drives movement over longer distances than the short-stroke module 7 but with relatively coarse position control. In an embodiment, the long-stroke stage driver 16,18 is configured to interact electromagnetically with a balance mass 5 to drive movement of the long-stroke stage 6. In an embodiment, the balance mass 5 is fixedly connected to and/or comprises a permanent magnet. In an embodiment, the electromagnetic interaction is contactless.

[0048] In an embodiment, a shuttle 4 is provided that can move linearly along a track 2. The shuttle 4 may be configured to carry cables for making electrical connections with actuators or sensors on one of the substrate tables WT. In an embodiment, an Rz-limiter 12 is attached to the shuttle 4 and configured to counterbalance torques acting on the substrate table WT about an axis parallel to Z.

[0049] In an embodiment, the shuttle 4 and Rz-limiter 12 are configured to drive movement of the substrate table WT, for example along the Y-direction (via the shuttle) and/or X- direction (via the Rz limiter). In an embodiment, the shuttle 4 and Rz-limiter 12 work in parallel with planar motors to drive the movement of the substrate table WT. In an embodiment, the shuttle 4 and/or Rz-limiter 12 are configured to provide at least 10% of the Y-component of forces applied to the substrate table WT. In an embodiment, the shuttle 4 and/or Rz-limiter 12 are configured to provide at least 10% of the X-component forces applied to the substrate table WT.

[0050] In an embodiment, a crash pole 15 is provided for mechanically preventing collisions between the two substrate tables WT. The crash pole 15 lowers the strength requirements of the Rz-limiter. In an embodiment the crash pole 15 comprises a projection 15 that allows one of the two substrate tables WT to pass the projection 15 in the Y-direction exclusively to a first side of the projection 15 (e.g. “above” in the orientation of the page of Figure 2) and the other of the two substrate tables WT to pass the projection 15 in the Y-direction exclusively to a second side of the projection 15 (e.g. “below” in the orientation of the page of Figure 2), the first side being opposite to the second side.

[0051] In an embodiment, a swap bridge 10 is provided for enabling transfer of the substrate W from one of the substrate tables WT to the other substrate table WT. In an embodiment, the swap bridge 10 is provided on the long-stroke stage 6. In an embodiment, the swap bridge 10 is configured selectively to couple the two short-stroke stages 8 together for the purposes of enabled substrate transfer. In an embodiment, the two short-stroke stages 8 are coupled together by the swap bridge 10 when substrate transfer is to be carried out and are released by the swap bridge 10 at other times. In an embodiment, the swap bridge coupling is such that the stages are both held stationary and/or are both held together to move as a single unit. In an embodiment, when the swap bridge releases the coupling the two short-stroke stages 8 can move independently of each other. In an embodiment, the swap bridge 10 is fixedly connected to the long-stroke stage 6 both when the swap bridge 10 couples together the short-stroke stages 8 and when the swap bridge 10 does not couple together the short-stroke stages 8. In an embodiment the swap bridge is provided to couple the short-stroke stages 8 together in a direction parallel to the X direction, thus reducing space requirements for the long-stroke stage parallel to the Y direction.

[0052] Larger substrates (e.g. 450mm diameter substrates rather than 300mm diameter substrates) will require larger substrate tables WT. Where a short-stroke module is provided, the short-stroke stage will be larger. Where a long-stroke module is provided, the long-stroke stage will need to be larger to support the short-stroke stage.

[0053] To avoid excessive deformation of the substrate table WT, a certain stiffness will need to be maintained. In an embodiment, stiffness is maintained by increasing the thickness of the substrate table (e.g. the thicknesses of the long- and/or short-strokes stages). However, increasing the thickness of the substrate table WT increases the separation in the Z direction between the center of mass of the substrate table WT and the position in Z in which forces are applied to the substrate table WT by driving of the long-stroke stage driver 16,18. This increased separation will tend to increase the size of torques acting about axes parallel to the X-Y plane caused by accelerations and decelerations of the substrate table WT during scanning of the substrate table WT. Resisting these forces, for example by applying Z forces using planar motors, may increase power requirements (e.g. increasing peak current levels to coils of the planar motors). Increasing power requirements places greater demands on the power supply, tends to increase the weight of the substrate table, and tends to increase thermal loads on various elements of the lithographic apparatus, potentially causing deformations and imaging errors such as overlay errors.

[0054] In an embodiment, the above matters are addressed by arranging for the largest cross-section of the long-stroke stage perpendicular to Z to have a larger area than the largest cross-section of the short-stroke stage perpendicular to Z. The long-stroke stage 6 thus protrudes laterally beyond the short-stroke stage 8. In an embodiment, the long-stroke stage 6 extends beyond the short-stroke stage 8 in the X direction, in the Y direction, or in both the X and Y directions. Arranging for the long-stroke stage 6 to protrude in this manner facilitates the application of forces to the long-stroke stage 6 by the long-stroke stage driver 16,18 at positions that are further from the center of mass of the substrate table WT (when viewed along Z). Driver modules 16 are examples of modules that are configured to apply such forces. The larger separation from the center of mass means that a given magnitude of force can produce a larger torque. The peak forces and therefore currents needed to counter the torques generated by acceleration and deceleration of the substrate table WT during scanning can therefore be reduced.

[0055] Arranging for the long-stroke stage 6 to protrude in this manner also facilitates mounting of elements of the long-stage driver 16,18, such as driving electronics 14 (Figure 3), laterally outside of the short-stroke stage 8 rather than underneath the short-stroke stage 8. The height of the center of mass of the substrate table WT can therefore be reduced, reducing the size of torques applied to the substrate table WT during acceleration and deceleration.

[0056] Figure 4 is a schematic illustration of a long-stroke stage 6 that is configured to extend laterally beyond the short-stroke stage 8. In the embodiment shown the long-stroke stage 6 extends on both of opposite sides (e.g. in the +X direction and the -X direction and/or in the +Y direction and the -Y direction) of the short-stroke stage 8. Where the short-stroke stage 8 is rectangular, the long-stroke stage 6 thus extends on two or four sides of the short-stroke stage 8. In an alternative embodiment, the long-stroke stage 6 extends on one side of the short-stroke stage 8 only or on three sides of the short-stroke stage 8 only.

[0057] Figure 5 shows an example embodiment in which a portion of long-stroke stage 6 overlaps with a portion of the short-stroke stage 8 along Z. Here, extending portions 17 of the long-stroke stage 6 (i.e. portions extending laterally beyond the short-stroke stage 8) extend also along Z to a position (broken line 24) that is closer to the projection system than a portion of the short-stroke stage between the lowest part (parallel to broken line 26) and the broken line 24. The extending portions 17 may be used to strengthen the long-stroke stage 6 or to house elements (such as electronics 14) of the long-stroke stage driver 16,18 for example.

[0058] In an embodiment, the center of mass of the long-stroke stage 6 is closer to the projection system than a portion of the short-stroke stage 8. In the embodiment of Figure 5 for example the center of mass of the long-stroke stage 6 is positioned between the broken lines 24 and 26.

[0059] In an embodiment, the extending portions 17 are configured (e.g. are made wide enough and/or to overlap sufficiently) so that the center of mass 32 of the long-stroke stage 6 is closer to the projection system than the center of mass 34 of the short-stroke stage 8.

Figure 6 illustrates an example embodiment of this type. The separation between broken lines 28 and 30 represents the difference in height between the two centers of mass. In an alternative embodiment the center of masses 32 and 34 are at the same height.

[0060] Figures 7-13 illustrate example configurations for the long-stroke stage driver 16,18. In an embodiment, the driver 16,18 comprises one or more X-driver modules 36,48,56 for applying forces to the long-stroke stage 6 parallel to the X direction. In an embodiment, the driver 16,18 comprises one or more Y-driver modules 38,50,58 for applying forces to the long-stroke stage 6 parallel to the Y-direction.

[0061] In an embodiment, at least one of the X-driver modules or Y-driver modules extends (or is positioned completely) beyond the short-stroke stage 8 in a direction parallel to X or parallel to Y or both. In an embodiment, at least one of the X-driver modules or Y-driver modules is configured to apply a force to the long-stroke stage 6 at a position that is beyond the short-stroke stage 8 in a direction parallel to X or parallel to Y or both. The driver 16 shown in Figure 3 (which in an embodiment comprises an X-driver module or a Y-driver module) is an example of such a configuration. Configuring driver modules to apply forces at positions that are further from the center of mass of the substrate table WT facilitates application of torque by these driver modules, reducing the power required by the driver modules for a given level of torque. Positioning the driver modules beyond the short-stroke stage 8 also facilitates a reduction in the overall height of the substrate table WT. For example, such positioning reduces the number of components that need to be provided directly underneath the short-stroke stage 8. Where all or part of the driver electronics 14 (see Figure 3) are also provided laterally outside of the short-stroke stage 8, connection to the driver modules is also facilitated. For example, connecting wires can be made shorter, reducing the weight of the substrate table WT. Reducing the weight of the substrate table WT improves dynamical performance.

[0062] Figures 7 and 8 illustrate embodiments in which X-driver modules 36,48 are provided in pairs either side of the center of mass 42 of the substrate table WT (when viewed along Z, perpendicular to the page as shown). The pairs are arranged so that the force 40 applied along X (shown explicitly in Figure 7 only) will act at the same perpendicular distance 44 from the center of mass 42. Thus, when the forces 40 applied by each X-driver module 36,48 in the pair are equal, the resulting torque about the Z axis on the long-stroke stage 6 is zero. Similarly, the Y-driver modules 38,50 are arranged in pairs either side of the center of mass 42. The pairs of Y-driver modules are arranged analogously to the pairs of X-driver modules so that the force 46 applied along Y (shown explicitly in Figure 8 only) will act at the same perpendicular distance 52 from the center of mass 42. Thus, when the forces 46 applied by each Y-driver module 38,50 in the pair are equal, the resulting torque about the Z axis on the long-stroke stage 6 is zero.

[0063] The arrangements of Figures 7 and 8 compensate well for torques applied about the Z-axis. However, driving of the modules also causes torques to be applied about axes lying within the X-Y plane, which are less well compensated. For example, during scanning the net acceleration/deceleration force acting on the long-stroke stage 6 below its center of mass will cause a torque to be applied about an axis that is perpendicular to Z and to the direction of acceleration/deceleration. This torque may be referred to as a "diving torque". The diving torque will cause a trailing edge of the long-stroke stage 6 to be pushed in a downwards direction and the leading edge of the long-stroke stage 6 to be pushed in an upwards direction. These forces change the effective weight distribution during scanning. In an embodiment, the long-stroke stage 6 is levitated by the X-driver modules and/or the Y-driver modules. In such an embodiment, variations in the effective weight to be supported means that different X-driver and/or Y-driver modules will need different amounts of power even when the force parallel to X or Y, respectively, is the same. This can lead to further imbalances in the torque applied about axes within the X-Y plane, further increasing the power requirements associated with compensating such torques.

[0064] For example, in an embodiment the X-driver modules and/or Y-driver modules are implemented using 3-coil sets driven by a three-phase power supply. In such an arrangement, driving of each module will result in a torque My (about the Y-axis for the X-driver modules) or Mx (about the X-axis for the Y-driver modules). The magnitude of the torque will depend on the magnitude of the force applied along X (for the X-driver modules) or Y (for the Y-driver modules), the force applied along Z, and the commutation angle. As discussed above, the diving torque will cause the force required along Z to be different for different driver modules in a given pair in an arrangement such as that shown in Figure 7 or 8, even when the forces along X or Y are equal. The resulting difference in My or Mx increases the difference in the forces required along Z, and increases peak power requirements.

[0065] Furthermore, it is difficult to position the driver modules sufficiently accurately that, when viewed along Z, the center of force passes exactly through the center of mass. Thus, it is even difficult to avoid net torques along Z using driver modules configured in the way shown in Figures 7 and 8.

[0066] In an embodiment, the above-described matters with the arrangements of Figure 7 and 8 are addressed by providing a drive system that comprises a plurality of first driver modules configured to apply forces to the substrate table having both components that are parallel to the X-Y plane and components that are parallel to the Z direction and one or more second driver modules configured to apply forces having components only in the the X-Y plane (i.e. forces having no component parallel to Z). The second driver modules thus do not contribute to compensating components of torque about axes parallel to the X-Y plane (such as diving torques). Operation of the second driver modules is therefore unaffected by accelerations or decelerations of the substrate table in the X-Y plane. Torques arising due to driving of the second driver modules themselves can thus be balanced more easily and the balance will not be disrupted by scanning of the substrate table.

[0067] An example of such an arrangement is shown in Figure 9. Here, the first driver modules comprise a plurality of X-driver modules 56 and the one or more second driver modules comprise one or more Y-driver modules 58.

[0068] In an embodiment, the plurality of X-driver modules 56 comprises at least two X-driver modules 56 that are configured to apply forces along X at positions that are spaced apart along Y. In the example shown, four pairs of X-driver modules 56 are provided. The two uppermost X-driver modules 56 (in the orientation of the page as shown) are configured to apply forces along X at positions that are spaced apart along Y from the positions at which the two lowermost X-driver modules 56 are configured to apply forces along X. In the embodiment shown, the perpendicular spacing 64 of the forces 60 from the center of mass for the two uppermost X-driver modules 56 is the same as the perpendicular spacing 64 of the forces 60 from the center of mass for the two lowermost X-driver modules 56. In other embodiments, fewer than four or more than four X-driver modules 56 may be provided.

[0069] In the arrangement shown, three Y-driver modules 58 are provided. The Y-driver modules 58 are configured relative to each other so that the net Mx torque arising where each Y-driver module 58 produces an equal force 62 is zero.

[0070] In an embodiment, only the X-driver modules 56 are configured to provide forces along Z. Forces along Z are required for supporting the weight of the substrate table WT and/or for compensating diving torques. The Y-driver modules 58 are configured to provide forces only along Y (not along Z). According to this arrangement, variations in the effective weight (i.e. variations in the Z forces needed to keep the substrate table level) will not affect the operation of the Y-driver modules 58. The net Mx torque associated with the Y-modules 58 can be maintained at or near zero even during periods of high acceleration/deceleration.

[0071] In an embodiment, the plurality of X-driver modules are configured such that when the carrier is being accelerated by the same magnitude in the X and Y directions (i.e. diagonal movement) the resulting torque on the substrate table can be fully corrected by applying forces with components parallel to Z by a subset of the X-driver modules containing fewer than all of the X-driver modules. Such diagonal acceleration is relatively common during scanning of different dies in an exposure phase for example. By avoiding involving all of the X-driver modules in the torque compensation, the peak power requirements of the drive system as a whole can be reduced. For accelerations along directions other than diagonal directions, a larger number of the X-driver modules may be required for effective compensation. However, even in this case the required forces along Z for a subset of the X-driver modules will be significantly reduced relative to other X-driver modules, thereby reducing the overall peak power requirements. Reducing peak power requirements reduces the expense and weight of the power supply for the drive system and/or reduces the heat load associated with running the drive system.

[0072] Figures 10 to 13 illustrate schematically how the Z force requirements for compensated diving torques due to the four possible diagonal accelerations is distributed between the different driver modules in an arrangement of the type illustrated in Figure 9.

[0073] Figure 10 illustrates changes in the required Z forces caused by acceleration of the substrate table WT along the diagonal +X,+Y direction. The diving torque in this case pushes the trailing edge of the substrate table downwards, which requires a corresponding upwards force to be provided by the X-driver module 56 (cross-hatched) that is positioned under the trailing edge of the substrate table. Similarly, the diving torque pushes the leading edge of the substrate table upwards, which causes a corresponding reduction in the upwards force required to support the weight of the substrate table by the X-driver module 56 (single hatched) that is positioned under the leading edge of the substrate table.

[0074] Figure 11 illustrates changes in the required Z forces caused by acceleration of the substrate table WT along the diagonal +X,-Y direction.

[0075] Figure 12 illustrates changes in the required Z forces caused by acceleration of the substrate table WT along the diagonal -X,+Y direction.

[0076] Figure 13 illustrates changes in the required Z forces caused by acceleration of the substrate table WT along the diagonal -X,-Y direction.

[0077] In each case illustrated, only two out of the four X-driver modules 56 are involved with compensating the diving torque. The operation of the two other X-driver modules 56 (depicted as non-filled rectangles) is unchanged. The peak power requirements, and therefore heat loads, can therefore be reduced.

[0078] In an embodiment, the Y direction corresponds to (is parallel to) the main scanning direction during exposure. In an alternative embodiment the X direction corresponds to (is parallel to) the main scanning direction during exposure.

[0079] Figure 14 depicts an example alternative drive system in which the first driver modules comprise a plurality of X-driver modules 56 and the second driver modules comprise a plurality of Y-driver modules 58. The X-driver modules 56 are each configured to apply a force component 60 parallel to X and a force component parallel to Z. The Y-driver modules 58 are each configured to apply a force 62 parallel to Y only. In this embodiment, a total of nine driver modules are provided: five X-driver modules 56 and four Y-driver modules 58. The Y-driver modules 58 are configured relative to each other so that the net Mx torque arising where each Y-driver module 58 produces an equal force 62 is zero. The plurality of X-driver modules 56 apply forces along X at positions that are spaced apart along Y (as in the arrangement of Figure 9). The plurality of Y-driver modules 58 apply forces along Y at positions that are spaced apart along X (in contrast to the arrangement of Figure 9 where the three Y-driver modules are all aligned along Y).

[0080] Figure 15 depicts an embodiment in which driver modules 72 in the long-stroke stage 6 are used to actively control the shape of the long-stroke stage 6. In this embodiment, a sensor system 76 is provided for measuring the shape of the long-stroke stage 6. For example, the sensor system 76 may comprise a plurality of sensors that measure the positions of a plurality of reference points on the surface of the long-stroke stage 6 relative to a reference frame or relative to other positions on the surface of the long-stroke stage 6. In an embodiment, the reference frame is the balance mass 5 or a magnet plate associated with or attached to the balance mass 5. In an embodiment, the reference frame is the short-stroke stage 8. In an embodiment, the reference frame is a metroframe or grid plate. In an embodiment, the sensor system 76 comprises an acceleration sensor for measuring the acceleration of the long-stroke stage 6. Calculations and/or calibration measurements can be used to estimate changes in the shape of the long-stroke stage 6 due to the measured accelerations.

[0081] In an embodiment, the control system or controller 70 is configured to increase the effective stiffness of the long-stroke stage 6. In this way, the long-stroke stage 6 can be made lighter and/or thinner (particularly in the region underneath the short-stroke stage 8). Making the long-stroke stage 6 lighter improves the dynamical properties of the stage and reduces demands on the drive system. Making the long-stroke stage 6 thinner underneath the short-stroke stage facilitates lowering of the center of mass of the substrate table, thus reducing the size of diving torques and further reducing the demands on the drive system.

[0082] Although the detailed examples refer to driving of a substrate table (i.e. a table capable of supporting a substrate), the drive system is not limited to driving movement of a substrate table and can be applied for driving movement of any carrier, for example a carrier used for measurement purposes, for example to calibrate the lithography apparatus, for example a carrier to measure and/or calibrate the position of the substrate table, for example a metrology element, such as a grid plate, used for measurement purposes, or a carrier for supporting a patterning device.

[0083] 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 herein 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 “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein 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 that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0084] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0085] The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 355, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0086] 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.

[0087] While specific embodiments of 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 (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.

[0088] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the clauses set out below. Other aspects of the invention are set out as in the following numbered clauses: 1. A lithographic apparatus comprising: a carrier for supporting a substrate, a metrology element or a patterning device; a projection system arranged to transfer a pattern from the patterning device onto the substrate; a drive system for moving the carrier relative to the projection system in a plane defined by reference to orthogonal axes X and Y within the plane and axis Z perpendicular to the plane, wherein: the drive system comprises: a short-stroke stage for supporting the carrier; and a long-stroke stage for supporting the short-stroke stage, wherein: the largest cross-section of the long-stroke stage perpendicular to Z has a larger area than the largest cross-section of the short-stroke stage perpendicular to Z.

2. An apparatus according to clause 1, wherein: an extending portion of the long-stroke stage extends along Z to a position closer to the projection system than a portion of the short-stroke stage.

3. An apparatus according to clause 1 or 2, wherein: the center of mass of the long-stroke stage is closer to the projection system than a portion of the short-stroke stage.

4. An apparatus according to any of clauses 1-3, wherein: the center of mass of the long-stroke stage is at the same position along Z as the center of mass of the short-stroke stage.

5. An apparatus according to any of clauses 1-3, wherein: the center of mass of the long-stroke stage is closer to the projection system than the center of mass of the short-stroke stage.

6. An apparatus according to any of the preceding clauses, further comprising: a short-stroke stage driver for driving movement of the short-stroke stage relative to the long-stroke stage.

7. An apparatus according to any of the preceding clauses, further comprising: a long-stroke stage driver for driving movement of the long-stroke stage relative to the projection system.

8. An apparatus according to clause 7, wherein: the long-stroke stage driver comprises one or more X-driver modules for applying forces to the long-stroke stage parallel to the X direction, and one or more Y-driver modules for applying forces to the long-stroke stage parallel to the Y-direction.

9. An apparatus according to clause 8, wherein: at least one of the X-driver modules or Y-driver modules extends or is positioned beyond the short-stroke stage in a direction parallel to X or parallel to Y or both.

10. An apparatus according to clause 8 or 9, wherein: at least one of the X-driver modules or Y-driver modules is configured to apply forces to the long-stroke stage in a direction parallel to Z.

11. An apparatus according to any of clauses 8-9, wherein: at least one of the X-driver modules or Y-driver modules is configured to apply a force to the long-stroke stage at a position that is beyond the short-stroke stage in a direction parallel to X or parallel to Y or both.

12. An apparatus according to any of the preceding clauses, further comprising: a sensor system for measuring the shape of the long-stroke stage.

13. An apparatus according to clause 12, comprising a long-stroke stage driver for driving movement of the long-stroke stage relative to the projection system, wherein: the long-stroke stage driver is configured to control the shape of the long-stroke stage by reference to the output from the sensor system.

14. An apparatus according to clause 12 or 13, wherein: the shape of long-stroke stage is controlled to increase the effective stiffness of the long-stroke stage.

15. An apparatus according to clause 13 or 14, wherein: the long-stroke stage driver is configured to control the shape of the long-stroke stage using at least one driver module that is also used to control the position of the long-stroke stage.

16. An apparatus according to any of clauses 12-15, wherein: the sensor system is configured to measure the shape of the long-stroke stage using at least one sensor element that is also used to measure the position of the long-stroke stage.

17. An apparatus according to clause 16, wherein: the sensor system is configured to measure the position of one or more reference points on the long-stroke stage relative to one or more other positions on the long-stroke stage or relative to a reference frame comprising one or more of the following: a balance mass and/or a magnet plate optionally integral with or attached to the balance mass, the short-stroke stage, a metroframe and/gridplate associated therewith for use in measuring the position and/or orientation of the substrate or substrate table.

18. An apparatus according to clause 16 or 17, wherein: the sensor system comprises an acceleration sensor for measuring the acceleration of the long-stroke stage.

19. An apparatus according to any of the preceding clauses, further comprising: an additional short-stroke stage; and a swap bridge for selectively coupling the short-stroke stage to the additional short-stroke stage, wherein: the swap bridge is fixedly mounted on the long-stroke stage.

20. An apparatus according to any of the preceding clauses, further comprising: an additional short-stroke stage; and a crash pole comprising a projection that prevents collisions by allowing one of the two short-stroke stages to pass the projection in the Y-direction exclusively to a first side of the projection and the other of the two short-stroke stages to pass the projection in the Y-direction exclusively to a second side of the projection, the first side being opposite to the second side.

21. A lithographic apparatus comprising: a carrier for supporting a substrate, a metrology element, or a patterning device; a projection system arranged to transfer a pattern from the patterning device onto the substrate; a drive system for moving the carrier relative to the projection system in a plane defined by reference to orthogonal axes X and Y within the plane and axis Z perpendicular to the plane, wherein: the drive system comprises: a plurality of first driver modules configured to apply forces to the carrier within the X-Y plane and in the Z direction; and one or more second driver modules configured to apply forces to the carrier within the X-Y plane only.

22. An apparatus according to clause 21, wherein: the first driver modules comprise X-driver modules configured to apply forces having components parallel to the X and Z directions but not the Y direction.

23. An apparatus according to clause 22, wherein: the second driver modules comprise one or more Y-driver modules configured to apply forces that are parallel to the Y direction only.

24. An apparatus according to clause 23, wherein: the plurality of X-driver modules are configured such that when the carrier is being accelerated by the same magnitude in the X and Y directions the resulting torque on the carrier can be fully corrected by applying forces parallel to Z by a subset of the X-driver modules containing fewer than all of the X-driver modules.

25. An apparatus according to clause 24, wherein: the subset of X-driver modules is different for accelerations along +X,+Y or -X,-Y relative to accelerations along +X,-Y or -X,+Y.

26. An apparatus according to any of clauses 23-25, wherein: the plurality of X-driver modules comprises at least two X-driver modules that are configured to apply forces along X at positions that are spaced apart along Y.

27. An apparatus according to any of clauses 23-26, wherein: the one or more Y-driver modules are configured to apply forces along Y at the same position along X.

28. An apparatus according to any of clauses 23-26, wherein: the plurality of Y-driver modules comprises at least two Y-driver modules that are configured to apply forces along Y at positions that are spaced apart along X.

29. An apparatus according to any of clauses 21-28, wherein: one or more of the driver modules comprises a coil system and is configured to apply the forces to the carrier by driving an electrical current through the coil system.

30. An apparatus according to clause 29, wherein: the coil system comprises three coils configured to be driven by a three-phase supply.

31. An apparatus according to any of the preceding clauses, wherein: the main scanning direction during exposure of the substrate is parallel to the Y-direction.

32. An apparatus according to any of the preceding clauses, wherein: the drive system is configured to apply forces to the carrier by driving an electrical current through a coil system positioned in a magnetic field.

33. A device manufacturing method comprising: providing a carrier for supporting a substrate, a metrology element, or a patterning device; transferring a pattern onto a substrate using a projection system; and using a drive system to move the carrier relative to the projection system in a plane defined by reference to orthogonal axes X and Y within the plane and axis Z perpendicular to the plane, wherein: the drive system comprises: a short-stroke stage for supporting the carrier; and a long-stroke stage for supporting the short-stroke stage, wherein: the largest cross-section of the long-stroke stage perpendicular to Z has a larger area than the largest cross-section of the short-stroke stage perpendicular to Z.

34. A device manufacturing method comprising: providing a carrier for supporting a substrate, a metrology element, or a patterning device; transferring a pattern onto a substrate using a projection system; and using a drive system to move the carrier relative to the projection system in a plane defined by reference to orthogonal axes X and Y within the plane and axis Z perpendicular to the plane, wherein: a plurality of first driver modules of the drive system are used to apply forces to the carrier within the X-Y plane and in the Z direction; and one or more second driver modules of the drive system are used to apply forces to the carrier within the X-Y plane only.

Claims (1)

A lithography device comprising: an illumination device adapted to provide a radiation beam; a carrier constructed to support a patterning device, the patterning device being capable of applying a pattern in a section of the radiation beam to form a patterned radiation beam; a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto a target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.