NL2010465A - Lithographic apparatus and device manufacturing method. - Google Patents

Description

LITHOGRAPHIC 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] It has been proposed to immerse the substrate in the lithographic projection apparatus in a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the final element of the projection system and the substrate. In an embodiment, the liquid is distilled water, although another liquid can be used. An embodiment of the present invention will be described with reference to liquid. However, another fluid may be suitable, particularly a wetting fluid, an incompressible fluid and/or a fluid with higher refractive index than air, desirably a higher refractive index than water. Fluids excluding gases are particularly desirable. The point of this is to enable imaging of smaller features since the exposure radiation will have a shorter wavelength in the liquid. (The effect of the liquid may also be regarded as increasing the effective numerical aperture (NA) of the system and also increasing the depth of focus.) Other immersion liquids have been proposed, including water with solid particles (e.g. quartz) suspended therein, or a liquid with a nano-particle suspension (e.g. particles with a maximum dimension of up to 10 nm). The suspended particles may or may not have a similar or the same refractive index as the liquid in which they are suspended. Other liquids which may be suitable include a hydrocarbon, such as an aromatic, a fluorohydrocarbon, and/or an aqueous solution.

SUMMARY

[0004] A type of positional measurement device used in a lithographic apparatus, and in particular in an immersion lithographic apparatus (of any type) comprises a grating, a radiation source and a sensor. The grating and sensor are mounted on different objects between which there is relative movement. A relative position of at least one of the objects is measured using the sensor and grating. For example, the grating may be attached to a substrate table or a reference frame of a lithographic apparatus and the sensor may be attached to the other of the substrate table or the reference frame. The sensor senses radiation reflected and/or diffracted by the grating so as to measure a relative position between the substrate table and the reference frame.

[0005] Such a positional measurement device may require quite a large grating, particularly if used in conjunction with a substrate table configured to hold a substrate of a large width (e.g., diameter, such as a 450 mm diameter). Even a relatively small thermal variation within the grating can result in an error in the positional measurement and so an overlay error.

[0006] It is desirable, for example, to provide a lithographic apparatus in which positional measurements are made using a grating and a sensor in which one or more measures are taken to improve the thermal stability and/or uniformity of the grating.

[0007] According to an aspect of the invention, there is provided a lithographic apparatus comprising: a table to hold an object; a reference frame; a grating member attached to the table or to the reference frame and having a recess; a sensor, attached to the other of the table or the reference frame, configured to detect radiation diffracted and/or reflected by the grating member so as to measure a relative position between the table and the reference frame; and a heat transfer member positioned in the recess and mechanically isolated from the grating member.

[0008] According to an aspect of the present invention, there is provided a device manufacturing method using a lithographic apparatus, the method comprising: projecting a patterned beam onto a substrate while holding the substrate in or on a substrate holder, wherein a position of the substrate holder relative to a reference frame is measured by using a sensor attached to the substrate holder or to the reference frame to detect radiation diffracted and/or reflected by a grating member attached to the other of the substrate holder or the reference frame; and thermally conditioning the grating member using a heat transfer member in a recess of the grating member, the heat transfer member being mechanically isolated from the grating member..

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] 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:

[0010] - Figure 1 depicts a lithographic apparatus according to an embodiment of the invention;

[0011] - Figures 2 and 3 depict a liquid supply system for use in a lithographic projection apparatus;

[0012] - Figure 4 depicts a further liquid supply system for use in a lithographic projection apparatus;

[0013] - Figure 5 depicts, in cross-section, a barrier member which may be used in an embodiment of the present invention as an immersion liquid supply system;

[0014] - Figure 6 depicts a lithographic apparatus according to an embodiment of the invention;

[0015] - Figure 7 is a more detailed view of the apparatus 4100;

[0016] - Figure 8 is a more detailed view of the source collector apparatus SO of the apparatus of Figures 6 and 7;

[0017] - Figure 9 is a schematic illustration, in cross-section, of a grating and sensor positional measurement device of a lithographic apparatus according to an embodiment of the present invention;

[0018] - Figure 10 depicts a detail of the embodiment of Figure 9 as a cross-section through line X-X;

[0019] - Figure 11 is a schematic illustration, in cross-section, of a grating and sensor positional measurement device of a lithographic apparatus according to an embodiment of the present invention;

[0020] - Figure 12 shows the results of a simulation as a temperature profile in a grating member through line X-X of Figure 9;

[0021] - Figure 13 illustrates, in plan, one arrangement of heat transfer members in a grating member; and

[0022] - Figure 14 is a schematic illustration of a grating and sensor positional measurement device of a lithographic apparatus.

DETAILED DESCRIPTION

[0023] Figure 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus comprises:

[0024] - an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation, DUV radiation or EUV radiation);

[0025] - 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;

[0026] - 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

[0027] - 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.

[0028] 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.

[0029] The support structure MT holds the patterning device. The support structure MT 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 MT can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure MT may be a frame or a table, for example, which may be fixed or movable as required. The support structure MT 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”.

[0030] 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.

[0031] 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.

[0032] The terms “projection system” used herein should be broadly interpreted as encompassing any type of 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”.

[0033] 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).

[0034] The lithographic apparatus may be of a type having two or more substrate support structures, such as substrate stages or substrate tables, and/or two or more support structures for patterning devices. In an apparatus with multiple substrate stages, all the substrate stages can be equivalent and interchangeable. In an embodiment, at least one of the multiple substrate stages is particularly adapted for exposure steps and at least one of the multiple substrate stages is particularly adapted for measurement or preparatory steps. In an embodiment of the invention one or more of the multiple substrate stages is replaced by a measurement stage. A measurement stage includes at least part one or more sensor systems such as a sensor detector and/or target of the sensor system but does not support a substrate. The measurement stage is positionable in the projection beam in place of a substrate stage or a support structure for a patterning device. In such apparatus the additional stages may be used in parallel, or preparatory steps may be carried out on one or more stages while one or more other stages are being used for exposure.

[0035] 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.

[0036] The illuminator IL may comprise an adjuster AM 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) 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. Similar to the source SO, the illuminator IL may or may not be considered to form part of the lithographic apparatus. For example, the illuminator IL may be an integral part of the lithographic apparatus or may be a separate entity from the lithographic apparatus. In the latter case, the lithographic apparatus may be configured to allow the illuminator IL to be mounted thereon. Optionally, the illuminator IL is detachable and may be separately provided (for example, by the lithographic apparatus manufacturer or another supplier).

[0037] 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 MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. Substrate W is held on the substrate table WT by a substrate holder according to an embodiment of the present invention and described further below. 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 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 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 MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device 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 MA, the patterning device alignment marks may be located between the dies.

[0038] The depicted apparatus could be used in at least one of the following modes:

[0039] 1. In step mode, the support structure 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.

[0040] 2. In scan mode, the support structure 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 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.

[0041] 3. In another mode, the support structure 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] 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 in manufacturing components with microscale, or even nanoscale, features, 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.

[0044] Arrangements for providing liquid between a final element of the projection system PS and the substrate can be classed into three general categories. These are the bath type arrangement, the so-called localized immersion system and the all-wet immersion system. In a bath type arrangement substantially the whole of the substrate W and optionally part of the substrate table WT is submersed in a bath of liquid.

[0045] A localized immersion system uses a liquid supply system in which liquid is only provided to a localized area of the substrate. The space fdled by liquid is smaller in plan than the top surface of the substrate and the volume filled with liquid remains substantially stationary relative to the projection system PS while the substrate W moves underneath that volume. Figures 2-5 show different supply devices which can be used in such a system. A sealing feature is present to seal liquid to the localized area. One way which has been proposed to arrange for this is disclosed in PCT patent application publication no. WO 99/49504.

[0046] In an all wet arrangement the liquid is unconfined. The whole top surface of the substrate and all or part of the substrate table is covered in immersion liquid. The depth of the liquid covering at least the substrate is small. The liquid may be a film, such as a thin film, of liquid on the substrate. Immersion liquid may be supplied to or in the region of a projection system and a facing surface facing the projection system (such a facing surface may be the surface of a substrate and/or a substrate table). Any of the liquid supply devices of Figures 2-5 can also be used in such a system. However, a sealing feature is not present, not activated, not as efficient as normal or otherwise ineffective to seal liquid to only the localized area.

[0047] As illustrated in Figures 2 and 3, liquid is supplied by at least one inlet onto the substrate, preferably along the direction of movement of the substrate relative to the final element. Liquid is removed by at least one outlet after having passed under the projection system. As the substrate is scanned beneath the element in a -X direction, liquid is supplied at the +X side of the element and taken up at the -X side. Various orientations and numbers of in- and outlets positioned around the final element are possible; one example is illustrated in Figure 3 in which four sets of an inlet with an outlet on either side arc provided in a regular pattern around the final element. Note that the direction of flow of the liquid is shown by arrows in Figures 2 and 3.

[0048] A further immersion lithography solution with a localized liquid supply system is shown in Figure 4. Liquid is supplied by two groove inlets on either side of the projection system PS and is removed by a plurality of discrete outlets arranged radially outwardly of the inlets. Note that the direction of flow of fluid and of the substrate is shown by arrows in Figure 4.

[0049] Another arrangement which has been proposed is to provide the liquid supply system with a liquid confinement structure which extends along at least a part of a boundary of the space between the final element of the projection system and the substrate, substrate table or both. Such an arrangement is illustrated in Figure 5.

[0050] Figure 5 schematically depicts a localized liquid supply system or fluid handling system with a liquid confinement structure 12, which extends along at least a part of a boundary of the space between the final element of the projection system and the substrate table WT or substrate W. (Please note that reference in the following text to surface of the substrate W also refers in addition or in the alternative to a surface of the substrate table, unless expressly stated otherwise.) In an embodiment, a seal is formed between the liquid confinement structure 12 and the surface of the substrate W and which may be a contactless seal such as a gas seal (such a system with a gas seal is disclosed in European patent application publication no. EP-A-1,420,298) or a liquid seal.

[0051] The liquid confinement structure 12 at least partly contains liquid in the space 11 between a final element of the projection system PS and the substrate W. The space 11 is at least partly formed by the liquid confinement structure 12 positioned below and surrounding the final element of the projection system PS. Liquid is brought into the space below the projection system PS and within the liquid confinement structure 12 by liquid inlet 13. The liquid may be removed by liquid outlet 13.

[0052] The liquid may be contained in the space 11 by a gas seal 16 which, during use, is formed between the bottom of the barrier member 12 and the surface of the substrate W. The gas in the gas seal is provided under pressure via inlet 15 to the gap between barrier member 12 and substrate W. The gas is extracted via outlet 14. The overpressure on the gas inlet 15, vacuum level on the outlet 14 and geometry of the gap are arranged so that there is a high-velocity gas flow 16 inwardly that confines the liquid. The force of the gas on the liquid between the barrier member 12 and the substrate W contains the liquid in a space 11. Such a system is disclosed in United States patent application publication no. US 2004-0207824, which is hereby incorporated by reference in its entirety. In an embodiment, the liquid confinement structure 12 does not have a gas seal.

[0053] An embodiment of the present invention may be applied to any fluid handling structure including those disclosed, for example, in United States patent application publication nos. US 2006-0158627, US 2006-0038968, US 2008-0212046, US 2009-0279060, US 2009-0279062, US 2004-0207824, US 2010-0313974 and US Serial No. 61/394,184 filed on 18 October 2010 the contents of all of which are hereby incorporated in their entirety by reference.

[0054] Many other types of liquid supply system are possible. An embodiment of the present invention is neither limited to any particular type of liquid supply system, nor to immersion lithography. An embodiment of the invention may be applied equally in any lithography. In an EUV lithography apparatus, the beam path is substantially evacuated and immersion arrangements described above are not used.

[0055] A controller 500 as shown in Figure 1 controls the overall operations of the lithographic apparatus and in particular performs an operation process described further below. Controller 500 can be embodied as a suitably-programmed computer comprising a central processing unit and volatile and/or non-volatile storage. Optionally, the computer may comprise one or more input and output devices such as a keyboard and screen, one or more network connections and/or one or more interfaces to the various parts of the lithographic apparatus. It will be appreciated that a one-to-one relationship between controlling computer and lithographic apparatus is not necessary. In an embodiment of the invention one computer can control multiple lithographic apparatuses. In an embodiment of the invention, multiple networked computers can be used to control one lithographic apparatus. The controller 500 may also be configured to control one or more associated process devices and/or substrate handling devices in a lithocell or cluster of which the lithographic apparatus forms a part. The controller 500 can be configured to be subordinate to a supervisory control system of a lithocell or cluster and/or an overall control system of a fab. In an embodiment the controller operates the apparatus to perform an embodiment of the present invention. In an embodiment the controller 500 has a memory to store the results of a method step described below for later use in a further method step.

[0056] Figure 6 schematically depicts an EUV lithographic apparatus 4100 including a source collector apparatus SO. The apparatus comprises:

[0057] - an illumination system (illuminator) EIL configured to condition a radiation beam B (e.g. EUV radiation);

[0058] - a support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask or a reticle) MA and connected to a first positioner PM configured to accurately position the patterning device;

[0059] - 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; and

[0060] - a projection system (e.g. a reflective projection 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.

[0061] These basic components of the EUV lithographic apparatus are similar in function to the corresponding components of the lithographic apparatus of Figure 1. The description below mainly covers areas of difference and duplicative description of aspects of the components that are the same is omitted.

[0062] In an EUV lithographic apparatus, it is desirable to use a vacuum or low pressure environment since gases can absorb too much radiation. A vacuum environment can therefore be provided to the whole beam path with the aid of a vacuum wall and one or more vacuum pumps.

[0063] Referring to Figure 6, the EUV illuminator EIL receives an extreme ultra violet radiation beam from the source collector apparatus SO. Methods to produce EUV radiation include, but are not necessarily limited to, converting a material into a plasma state that has at least one element, e.g., xenon, lithium or tin, with one or more emission lines in the EUV range.

[0064] The radiation beam EB 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. After being reflected from the patterning device (e.g. mask) MA, the radiation beam EB 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 PS2 (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 EB. Similarly, the first positioner PM and another position sensor PS1 can be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam EB. Patterning device (e.g. mask) MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks PI, P2.

[0065] The depicted apparatus could be used the same modes as the apparatus of Figure 1.

[0066] Figure 7 shows the EUV apparatus 4100 in more detail, including the source collector apparatus SO, the EUV illumination system EIL, and the projection system PS. The source collector apparatus SO is constructed and arranged such that a vacuum environment can be maintained in an enclosing structure 4220 of the source collector apparatus SO. An EUV radiation emitting plasma 4210 may be formed by a discharge produced plasma source. EUV radiation may be produced by a gas or vapor, for example Xe gas, Li vapor or Sn vapor in which the plasma 4210 is created to emit radiation in the EUV range of the electromagnetic spectrum.

[0067] The radiation emitted by the plasma 4210 is passed from a source chamber 4211 into a collector chamber 4212 via an optional gas barrier and/or contaminant trap 4230 (in some cases also referred to as contaminant barrier or foil trap) which is positioned in or behind an opening in source chamber 4211.

[0068] The collector chamber 4212 may include a radiation collector CO which may be a so-called grazing incidence collector. Radiation collector CO has an upstream radiation collector side 4251 and a downstream radiation collector side 4252. Radiation that traverses collector CO can be reflected by a grating spectral filter 4240 to be focused in a virtual source point IF. The virtual source point IF is commonly referred to as the intermediate focus, and the source collector apparatus is arranged such that the intermediate focus IF is located at or near an opening 4221 in the enclosing structure 4220. The virtual source point IF is an image of the radiation emitting plasma 4210.

[0069] Subsequently the radiation traverses the illumination system IL, which may include a facetted field mirror device 422 and a facetted pupil mirror device 424 arranged to provide a desired angular distribution of the radiation beam 421, at the patterning device MA, as well as a desired uniformity of radiation intensity at the patterning device MA. Upon reflection of the beam of radiation 421 at the patterning device MA, held by the support structure MT, a patterned beam 426 is formed and the patterned beam 426 is imaged by the projection system PS via reflective elements 428, 430 onto a substrate W held by the substrate stage or substrate table WT.

[0070] Collector optic CO, as illustrated in Figure 7, is depicted as a nested collector with grazing incidence reflectors 4253, 4254 and 4255, just as an example of a collector (or collector mirror). The grazing incidence reflectors 4253,4254 and 4255 are disposed axially symmetric around an optical axis O and a collector optic CO of this type is preferably used in combination with a discharge produced plasma source, often called a DPP source.

[0071] Alternatively, the source collector apparatus SO may be part of an LPP radiation system as shown in Figure 8. A laser LA is arranged to deposit laser energy into a fuel, such as xenon (Xe), tin (Sn) or lithium (Li), creating the highly ionized plasma 4210 with electron temperatures of several 10's of eV. The energetic radiation generated during de-excitation and recombination of these ions is emitted from the plasma, collected by a near normal incidence collector optic CO and focused onto the opening 4221 in the enclosing structure 4220.

[0072] An embodiment of the present invention can be applied to any type of lithographic apparatus. However, an embodiment of the present invention may be particularly suited to applications where the substrate table is held in a gaseous atmosphere (i.e. not EUV). In particular, an embodiment of the present invention may be applied to an immersion apparatus.

[0073] Figure 9 shows in part, in cross-section, an immersion lithographic apparatus which uses a grating and sensor positional measurement device.

[0074] Figure 9 illustrates schematically, in cross-section, a substrate table WT and a liquid supply system 12 as well as a projection system PS. As can be seen, the apparatus depicted is a so called localized immersion system in which a film of liquid covers only part of the top surface of the substrate/substrate table WT at any one time. However, an embodiment of the invention is equally applicable to other types of apparatus, such as an all wet system in which a film of liquid covers the whole of the top surface of the substrate table WT.

[0075] In order to determine, e.g., the position of the substrate table WT relative to the projection system PS, a grating and sensor positional measurement device is used. In the embodiment of Figure 9 the sensor 20 is attached to the substrate table WT and the grating 50 is attached to a reference frame RF, which may be a so called metrology frame. The relative position of the grating 50 to the projection system PS is known and remains substantially constant because the position of the projection system PS relative to the reference frame RF is known. The reference frame RF of a lithographic apparatus may be mounted with one or more passive or active gas mounts on a base frame BF (shown also in Figure 1) to filter an external disturbance such as vibration in the factory floor. In this way, the optical column of the projection system PS may be held in a substantially stationary position. During a scanning movement of the substrate table WT, it is desired to know the position of the substrate table WT with respect to the optical column. Therefore, the positional measurement device is provided with which the position of the substrate table WT with respect to the reference frame RF can be determined. In one embodiment, the sensor 20 is attached to the reference or metrology frame RF while the grating 50 is on or attached to the substrate table WT. Such an embodiment is described with reference to Figure 14 below.

[0076] The grating 50 comprises a plurality of lines or spots, for example chromium lines or spots, on a surface. The surface could be the surface of a plate 55, for example. Together the plate 55 and grating 50 form a grating member 60.

[0077] The plate 55 is desirably made of a low coefficient of thermal expansion material. For example, a low coefficient of thermal expansion glass, glass ceramic or ceramic may be used such as Zerodur (RTM). Such a material undesirably has a low thermal conductivity which can result in a temperature gradient developing in the plate 55 which can lead to a positional measurement error. Because of the thickness of the plate 55, a heat load on the bottom of the plate 55 cannot easily be corrected from the top side.

[0078] The lines of the grating 50 are, for example, a plurality of parallel lines (1-D). However, other forms of grating 50 could be used. For example, the grating 50 could be a plurality of lines in a first direction as well as a plurality of lines in a second direction wherein the first and second directions are substantially perpendicular, for example (2-D).

[0079] A beam of radiation is directed towards the grating 50, for example, by a radiation source 30. In one embodiment the radiation source 30 produces radiation of a wavelength of about 600 nm, for example. In one embodiment the radiation source 30 produces radiation of a wavelength of about 780 nm. The exact wavelength may be another value. The radiation source may be attached to the reference frame RF. The radiation source 30 may be attached to the substrate tabic WT, as illustrated. The beam of radiation directed to the grating 50 by the radiation source 30 is reflected and/or diffracted by the grating 50 and this radiation is then detected by the sensor 20. Together the sensor 20 and radiation source 30 form an encoder 40.

[0080] Positional measurement is carried out by measuring the position of the sensor 20 with respect to the grating 50 in one or more degrees of freedom. As is illustrated in Figure 13, which is a plan view of the system of Figure 9, a plurality of sensors 20 and radiation sources 30 are attached to the substrate table WT. Each encoder 40 is capable of measuring a position of the substrate table WT in two degrees of freedom, making position measurement in six degrees of freedom possible. Using the encoder-type measurement system a position measurement with high accuracy is possible. Any other suitable configuration of encoder heads may be applied. In the embodiment of Figure 13 there are at least three encoders on the substrate table WT and desirably four. This allows positional and rotational movement of the substrate table WT to be detected. Also, as illustrated in Figure 13, the grating 50 is split into four separate gratings 50a, 50b, 50c, 50d. The lines of each grating 50a, 50b, 50c, 50d may have any orientation with respect to each other. In one embodiment the lines of each grating 50a, 50b, 50c, 50d are non parallel and non orthogonal with respect to each other.

[0081] In an embodiment, the grating 50 comprises a central hole for part of the optical column of the projection system PS and is mounted on the reference frame RF with a number of mounting devices.

[0082] In the embodiment of Figure 9 one or more measures are taken to improve the thermal stability and/or thermal uniformity of the grating member 60. For this purpose the grating member 60 is provided with a recess 120. A heat transfer member 100 is positioned in the recess 120. The heat transfer member 100 is mechanically isolated from the grating member 60. In an embodiment the recess is formed in the plate 55 of the grating member 60.

[0083] In an embodiment, the heat transfer member 100 may be an active heat transfer element 100 and may be controlled by a controller 400 in a feedback loop based on a sensed temperature sensed by one or more temperature sensors 410 and a certain (e.g. predefined) target temperature. If a plurality of heat transfer members 100 are present, each heat transfer member 100 may have an associated temperature sensor 410 and controller 400.

[0084] Because the heat transfer member 100 is mechanically isolated from the grating member 60, deleterious vibrations which might otherwise be transmitted from the heat transfer member 100 to the grating member 60 can be avoided. Thus, a disadvantage of using a heat transfer fluid in a passageway in the grating member 60 in order thermally to condition the grating member 60 can be avoided.

[0085] In the embodiment of Figure 9 there is no contact between the heat transfer member 100 and the grating member 60. That is, the heat transfer member 100 is positioned in the recess 120 in a contactless way. A gap 110 exists between the heat transfer member 100 and the grating member 60. In an embodiment the gap 110 is at least large as a tolerance of movement between the grating member 60 and the heat transfer member 100. This helps ensure no contact between the heat transfer member 100 and the grating member 60.

[0086] In an embodiment the gap is less than 3 mm wide. The width of the gap 110 is indicated by reference numeral 134 in Figure 10. If the gap is more than 3 mm wide heat transfer between the heat transfer member 100 and the grating member 60 may not be great enough. In an embodiment the gap is less than 2.5 mm wide or less than 2 mm wide. The smaller the gap the greater the heat transfer between the grating member 60 and the heat transfer member 100. The gap 110 should desirably not become too small so as to risk contact between the heat transfer member 100 and the grating member 60. Therefore, in an embodiment the gap 110 is at least 0.5 mm. In an embodiment the gap 110 is at least 1.0 mm wide. In an embodiment, the gap 110 is 1.5 mm wide.

[0087] In an embodiment the heat transfer member 100 is attached to a further frame other than the reference frame. The further frame may be mechanically isolated from the reference frame RF. In an embodiment the heat transfer member is attached (e.g. stiffly) to the base frame BF which is mechanically isolated from the reference frame RF. In the embodiment of Figure 9 a tolerance of movement between the reference frame RF and the base frame BF is at least as large as a tolerance of movement between the grating member 60 and the heat transfer member 100.

[0088] The recess 120 in the plate 55 may be an open recess (in the sense that it is open along its length to an outer surface of the plate 55) or may be in the form of a hole. In an embodiment, the recess 120 is open to the atmosphere surrounding the grating member 60. An advantage of the recess 120 being in the form of a hole is that the area of thermal transfer between the plate 55 and the heat transfer member 100 is maximized in that way. In an embodiment the hole is a throughhole. This allows, as illustrated in Figure 9, the heat transfer member 100 to be supported at opposite ends. This has an advantage in that it is then easier to make the gap 110 smaller without risking contact, during use, between the heat transfer member 100 and the grating member 60.

[0089] In an embodiment the recess 120 is formed by drilling. Other suitable means may be used.

[0090] Heat transfer between the heat transfer member 100 and the grating member 60 occurs through a combination of conduction and/or convection (through gas (e.g. air) present in a gap 110 between the grating member 60 and the heat transfer member 100 (illustrated more clearly in Figure 10)), and/or radiation. In the case that the apparatus is an EUV apparatus, no gas may be present in the gap 110. In such an embodiment heat transfer between the heat transfer member 100 and the grating member 60 may be slower. In an embodiment, in an EUV apparatus, gas is provided in the gap 110. The gas may be confined to the gap 110 using a seal between the plate 55 and the heat transfer member 100. So as to avoid the transfer of forces between the heat transfer member 100 and the plate 55, the seal may be in the form of a bellows, for example.

[0091] In an embodiment the gas in the gap 110 between the heat transfer member 100 and the grating member 60 is helium or at least helium rich. This is advantageous as helium has a high thermal conductivity. Another suitable high thermally conductive gas may be H2 (hydrogen), a mixture of He and H2, a gas comprising water vapor, another gas or any combination selected from the above. In an embodiment, the gas may comprise any of the above and/or at least one of the following: air, argon and/or nitrogen. Using a gas with a high thermal conductivity encourages the transfer of heat between the heat transfer member 100 and the grating member 60.

[0092] In an embodiment the gap 110 may be at least partly filled with a liquid. This may be advantageous in that heat transfer through a liquid may be greater than through a gas. In an embodiment the liquid is not constrained. This may be advantageous as this will reduce transfer of forces between the heat transfer member 100 and the plate 55.

[0093] In an embodiment, such as that illustrated in Figure 9, and on the left hand side of Figure 10, the heat transfer member 100 is an active heat transfer member. That is, active measures are taken to transfer heat, rather than just relying on heat conduction as in a passive system. In the embodiment illustrated in Figure 9 and on the left hand side of Figure 10, the heat transfer member 100 is hollow and has a passageway 102 through it to allow the flow of a thermal conditioning fluid therethrough. For this purpose a thermal conditioning fluid source 200 is provided which is connected via a (flexible) conduit 210 to the heat transfer member 100. In an embodiment the thermal conditioning fluid is a liquid. This is advantageous as the thermal capacity of a liquid is greater than that of a gas. In an embodiment, the thermal conditioning fluid source 200 may also be a source for thermal conditioning fluid of a projection system PS cooling system.

[0094] One or more other types of active heat transfer member may be used. For example, an electrical heater and/or cooler (for example a Peltier module) could be attached on or provided in a member inserted into the recess 120. The controller 400 could provide current to the electrical heater and/or cooler to provide a heat load.

[0095] Figure 10 shows two embodiments of heat transfer member 100. Figure 10 is a cross section through line X-X of Figures 9 and 11. On the left hand side of Figure 10 is an active heat transfer member 100b such as that shown in the embodiment of Figure 9. On the right hand side of Figure 10 is a passive heat transfer member such as that described below with reference to Figure 11.

[0096] In an embodiment the heat transfer member 100 is made of a material with a high thermal conductivity. This is advantageous in that it aids in heat transfer. In an embodiment the thermal conductivity of the heat transfer member 100 is greater than 10 Wm'1 K'1 at 25°C. In an embodiment, the thermal conductivity is greater than 40 Wm'1 K'1 at 25°C or greater than 200 Wm'1 K'1 at 25°C. Example materials are aluminum or an aluminum alloy (a thermal conductivity of 250 Wm"1 K"1) or steel (a thermal conductivity of about 16 Wm"1 K"1 in the case of stainless steel or about 50 Wm"1 K"1 in the case of plane carbon steel). Other materials, e.g. nickel or nickel alloy or magnesium or magnesium alloy, may be suitable.

[0097] In an embodiment more than one recess and associated heat transfer member 100 is provided in the grating member 60. In order to achieve good thermal uniformity of the plate 55, it may be necessary to adjust the spacing and/or position of the recesses 120. In an embodiment the plural recesses 120 extend in substantially parallel directions. This advantageously helps keep heat extraction/application uniform.

[0098] As illustrated in Figure 9, in an embodiment the recess 120 (and corresponding heat transfer member 100) is elongate. In an embodiment the recess 120 is elongate in a direction substantially parallel to a plane in which the grating 50 of the grating member 60 lies. This means that the effect of the heat transfer member 100 can be felt by the grating substantially equally along the length of the heat transfer member 100. The distance between the recess 120 and the grating 50 (distance 131) is desirably less than 80 mm or less than 60 mm. The shorter the distance the greater the effect of the heat transfer member 100 on the thermal stability of the plate 55 next to the grating 50 (where the largest deviation of positional measurement occurs in the presence of a thermal gradient). It is desirable that the recess 120 is not too close to the grating 50 as this might result in mechanical distortion of the grating 50. Therefore, it is desirable that the recess 120 is at least 20 mm or at least 40 mm from the grating 50.

[0099] In the case of a plurality of recesses 120 being present, desirably the pitch of the recesses (distance 132) is substantially constant. A suitable pitch may be between 50 nun and 150 mm or between 75 mm and 125 mm, for the case of a recess 120 of a width (e.g., diameter) 133 of about 40 mm (between say 30 and 50 mm).

[00100] The right hand side of Figure 10 and Figure 11 show an embodiment in which a passive heat transfer member 100a is used. Otherwise the embodiment of Figure 11 is the same as that of Figure 9.

[00101] A passive heat transfer member 100a may be desirable in that no flow of fluid or flow of electricity into the heat transfer member 100 is necessary. As illustrated in Figure 10, a passive heat transfer member may be formed of a solid material. A heat exchanger 300 may be positioned outside the recess 120 (for example at one or both ends of the heat transfer member 100) to extract heat from, or apply heat to, the heat transfer member 100 for onward transfer to/from the grating member 60.

[00102] Another form of passive heat transfer member is a heat pipe. Tn a heat pipe a liquid in a pipe evaporates at one (hot) end of the pipe (to provide a cooling) load. The gas then travels to the other (cooler) end of the pipe where the gas condenses back to a liquid. The liquid returns to the hot end of the pipe via a wick. In an embodiment, the cold end of the heat pipe is in the recess 120 and the hot end of the heat pipe is outside the recess 120 and is being cooled by the heat exchanger 300. Another form of passive heat transfer member is one incorporating a phase change material which changes phase at the ends of a pipe and absorbs/gives out heat as a result of the phase transformation.

[00103] Figure 12 illustrates the results of a simulation in which a heat load is provided to the bottom surface of a plate 55 (it is assumed to be held at air temperature i.e. 23°C) and a plurality of recesses 120 with heat transfer members 100 therein. The top surface of the plate 55 is assumed to be at 22°C, as are the heat transfer members 100. The heat transfer members 100 are present to reduce the thermal gradient within the grating member 60 and to extract heat from the bottom surface of the plate 55. As can be seen, heat transfer members 100 are successfully transferring heat. In practice the difference in temperature between the top and bottom of the plate 55 is less, so the simulation of Figure 12 over estimates the temperature gradient. Comparing simulations similar to that shown in Figure 12 to the same simulations without heat transfer members 100, shows that the grating member 60 deformed by a factor of 2 less, for the same heat loads applied to the bottom of the grid member, in the case of the presence of heat transfer members 100 than for the case where no heat transfer members 100 are provided.

[00104] Figure 13 shows, in plan, an arrangement of gratings 50a-50d and an arrangement of heat transfer members lOOd, 100e within the grating members 60. In an embodiment, where possible, heat transfer members 1 OOd are supported at each end and pass right through a throughholc recess 120 in the grating member 60. In certain locations, for example, in the vicinity of the projection system PS, this may not be possible. In this case heat transfer members 100e may only be supported at one end by the base frame BF. Of course other arrangements of heat transfer element 100 are possible.

[00105] Figure 14 shows a further embodiment which is the same as Figure 9 except as described below. In Figure 14 the encoders 40 (comprising the sensor 20 and source 30) are attached to the reference frame RF and the grating member 60 comprising the grating 50 and plate 55 are provided on the substrate table WT. In this situation, instead of being attached to a frame, the one or more heat transfer members 100 are attached to the substrate table WT as well as the grating member 60. However, the heat transfer member 100 may still be mechanically isolated from the grating member 60, for example by use of a mechanical isolation mechanism, such as a gas bearing or other damper. In an embodiment the heat transfer member 100 is conditioned with thermal conditioning fluid used to thermally condition the substrate table. Such thermal conditioning fluid or a thermal conditioning fluid for conditioning the projection system PS may be provided through one or more flexible conduits. A passive heat transfer element 100 such as a heat pipe and/or a phase change heat exchanger is particularly suited to this embodiment as no power or fluid needs to be provided to the moving substrate table WT.

[00106] An embodiment of the present invention has been described above in relation to a measurement system measuring the position of a substrate table WT. However, an embodiment of the present invention can be applied to a system to measure the position between any two objects, for example measuring the position of a patterning device table MT relative to a reference frame RF.

[00107] As will be appreciated, any of the above described features can be used with any other feature and it is not only those combinations explicitly described which are covered in this application.

[00108] 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 in manufacturing components with microscale, or even nanoscale features, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-fdm 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 1C, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[00109] 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, 248, 193, 157 or 126 nm).

[00110] The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive and reflective optical components.

[00111] While specific embodiments of the invention have been described above, it will be appreciated that the invention, at least in the form of a method of operation of an apparatus as herein described, may be practiced otherwise than as described. For example, the embodiments of the invention, at least in the form of a method of operation of an apparatus, may take the form of one or more computer programs containing one or more sequences of machine-readable instructions describing a method of operating an apparatus as discussed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein. Further, the machine readable instruction may be embodied in two or more computer programs. The two or more computer programs may be stored on one or more different memories and/or data storage media.

[00112] Any controllers described herein may each or in combination be operable when the one or more computer programs are read by one or more computer processors located within at least one component of the lithographic apparatus. The controllers may each or in combination have any suitable configuration for receiving, processing and sending signals. One or more multiple processors are configured to communicate with at least one of the controllers. For example, each controller may include one or more processors for executing the computer programs that include machine-readable instructions for the methods of operating an apparatus as described above. The controllers may include data storage media for storing such computer programs, and/or hardware to receive such media. So the controller(s) may operate according to the machine readable instructions of one or more computer programs.

[00113] An embodiment of the invention may be applied to substrates with a width (e.g., diameter) of 300 mm or 450 mm or any other size.

[00114] One or more embodiments of the invention may be applied to any immersion lithography apparatus, in particular, but not exclusively, those types mentioned above, whether the immersion liquid is provided in the form of a bath, only on a localized surface area of the substrate, or is unconfined on the substrate and/or substrate table. In an unconfined arrangement, the immersion liquid may flow over the surface of the substrate and/or substrate table so that substantially the entire uncovered surface of the substrate table and/or substrate is wetted. Tn such an unconfined immersion system, the liquid supply system may not confine the immersion liquid or it may provide a proportion of immersion liquid confinement, but not substantially complete confinement of the immersion liquid.

[00115] A liquid supply system as contemplated herein should be broadly construed. In certain embodiments, it may be a mechanism or combination of structures that provides a liquid to a space between the projection system and the substrate and/or substrate table. It may comprise a combination of one or more structures, one or more liquid inlets, one or more gas inlets, one or more gas outlets, and/or one or more liquid outlets that provide liquid to the space. In an embodiment, a surface of the space may be a portion of the substrate and/or substrate table, or a surface of the space may completely cover a surface of the substrate and/or substrate table, or the space may envelop the substrate and/or substrate table. The liquid supply system may optionally further include one or more elements to control the position, quantity, quality, shape, flow rate or any other features of the liquid.

[00116] 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 arc set out as in the following numbered clauses: 1. A lithographic apparatus comprising: a table to hold an object; a reference frame; a grating member attached to the table or to the reference frame and having a recess; a sensor, attached to the other of the table or the reference frame, configured to detect radiation diffracted and/or reflected by the grating member so as to measure a relative position between the table and the reference frame; and a heat transfer member positioned in the recess and mechanically isolated from the grating member.

2. The lithographic apparatus of clause 1, wherein the heat transfer member is attached to a further frame mechanically isolated from the reference frame.

3. The lithographic apparatus of clause 1 or clause 2, further comprising a gap between the heat transfer member and the reference frame.

4. The lithographic apparatus of clause 3, wherein the gap is a gas filled space.

5. The lithographic apparatus of clause 4, wherein the gas is air or is helium rich.

6. The lithographic apparatus of any of clauses 3-5, wherein the gap is at least as large as a tolerance of movement between the grating member and the heat transfer member.

7. The lithographic apparatus of any of clauses 3-6, wherein the gap is less than 3 mm wide, less than 2.5 mm wide or less than 2 mm wide.

8. The lithographic apparatus of any of clauses 3-7, wherein the gap is at least 0.5 mm wide or at least 1.0 mm wide.

9. The lithographic apparatus of any of clauses 1-8, wherein the heat transfer member is positioned in the recess in a contactless manner with respect to the grating member.

10. The lithographic apparatus of any of clauses 1-9, wherein the recess is a hole.

11. The lithographic apparatus of clause 10, wherein the hole is a through hole.

12. The lithographic apparatus of any of clauses 1-11, wherein the recess is elongate and is elongate in a direction substantially parallel to a plane in which a grating of the grating member lies and/or wherein the recess is spaced from a grating of the grating member by between 20 mm and 80 mm or by between 40 mm and 60 mm.

13. The lithographic apparatus of any of clauses 1-12, wherein the grating member has a plurality of recesses and each recess has an associated heat transfer member.

14. The lithographic apparatus of clause 13, wherein the plurality of recesses are elongate in substantially parallel directions.

15. The lithographic apparatus of clause 13 or clause 14, wherein the plurality of recesses are spaced between 50 mm and 150 mm apart or between 75 mm and 125 mm apart.

16. The lithographic apparatus of any of clauses 1-15, wherein the heat transfer member is an active heat transfer member.

17. The lithographic apparatus of any of clauses 1-15, wherein the heat transfer member is a passive heat transfer member.

18. The lithographic apparatus of any of clauses 1-16, wherein the heat transfer member has a channel through it for the passage therethrough of a thermal conditioning fluid.

19. The lithographic apparatus of clause 18, wherein the thermal conducting fluid is a liquid.

20. The lithographic apparatus of clause 18 or clause 19, further comprising a source of the thermal conditioning fluid.

21. The lithographic apparatus of clause 20, wherein the source is used as a source for thermal conditioning fluid for a thermal conditioning system to thermally condition a lens of a projection system of the apparatus.

22. The lithographic apparatus of any of clauses 1-21, wherein the heat transfer member is made of a material with a thermal conductivity of greater than 10 Wm^K"1 at 25°C, greater than 40 Wm^K'1 or greater than 200 Wm"1 K"1.

23. The lithographic apparatus of any of clauses 1-22, wherein the heat transfer member is made of a metal, preferably steel, aluminum or an aluminum alloy.

24. A device manufacturing method using a lithographic apparatus, the method comprising: projecting a patterned beam onto a substrate while holding the substrate in or on a substrate holder, wherein a position of the substrate holder relative to a reference frame is measured by using a sensor attached to the substrate holder or to the reference frame to detect radiation diffracted and/or reflected by a grating member attached to the other of the substrate holder or the reference frame; and thermally conditioning the grating member using a heat transfer member in a recess of the grating member, the heat transfer member being mechanically isolated from the grating member.

Claims (1)

1. Een lithografieinrichting omvattende: een belichtinginrichting ingericht voor het leveren van een stralingsbundel; een drager geconstrueerd voor het dragen van een patroneerinrichting, welke patroneerinrichting in staat is een patroon aan te brengen in een doorsnede van de stralingsbundel ter vorming van een gepatroneerde stralingsbundel; een substraattafel geconstrueerd om een substraat te dragen; en een projectieinrichting ingericht voor het projecteren van de gepatroneerde stralingsbundel op een doelgebied van het substraat, met het kenmerk, dat de substraattafel is ingericht voor het positioneren van het doelgebied van het substraat in een brandpuntsvlak van de proj ectieinrichting.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.