Module for a lithographic apparatus, lithographic apparatus and method for clamping a sensor member

Abstract

Disclosed herein is a module for a lithographic apparatus comprising: a component table configured to hold a component; a sensor member; and a sensor clamping mechanism configured to exert an active clamping force for clamping the sensor member relative to the component table. The sensor clamping mechanism may e.g. be configured to exert a vacuum clamping force or an electrostatic clamping force for clamping the sensor member.

Description

MODULE FOR A LITHOGRAPHIC APPARATUS, LITHOGRAPHIC APPARATUS AND METHOD FOR CLAMPING A SENSOR MEMBERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 24170510.2 which was filed on April 16, 2024 and which is incorporated herein in its entirety by reference.FIELD

[0002] The present invention relates to a module for a lithographic apparatus, a lithographic apparatus and a method for clamping a sensor member.BACKGROUND

[0003] 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.

[0004] An illumination system may condition a radiation beam of UV radiation, DUV radiation or EUV radiation. The point of this is to enable imaging of smaller features since the exposure radiation has a short wavelength.

[0005] In a conventional lithography apparatus, one or more sensors may be provided for measurements. Such a sensor may need to be mounted in such a way that allows the sensor to be replaced.

[0006] There is a need to improve the mounting of a sensor. More particularly, it is desirable to improve the position stability of the sensor during a scan.SUMMARY

[0007] According to a first aspect of the invention, there is provided a module for a lithographic apparatus comprising: a component table configured to hold a component; a sensor member; and a sensor clamping mechanism configured to exert an active clamping force for clamping the sensor member relative to the component table.

[0008] According to a second aspect of the invention, there is provided a method for clamping a sensor member relative to a component table of a lithographic apparatus, the method comprising: holding a component with a component table; and exerting an active clamping force for clamping the sensor member relative to the component table.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:

[0010] Figure 1 depicts a lithographic apparatus;

[0011] Figure 2 depicts a lithographic apparatus;

[0012] Figure 3 is a more detailed view of the apparatus of Figure 2;

[0013] Figure 4 is a schematic view, in cross-section, of a module for a lithographic apparatus;

[0014] Figure 5 is a schematic view, in cross-section of another module for a lithographic apparatus;

[0015] Figure 6 is a schematic view, in cross-section, of an alternative module for a lithographic apparatus;

[0016] Figure 7 is a schematic plan view of a module for a lithographic apparatus; and

[0017] Figure 8 is a schematic plan view of an alternative module for a lithographic apparatus.

[0018] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.DETAILED DESCRIPTION

[0019] Figures 1 and 2 schematically depict lithographic apparatuses that may use an electrostatic clamp according to an embodiment of the invention. Each apparatus may comprise:

[0020] - an illumination system (illuminator) IL configured to condition a radiation beam B (e.g.UV radiation, DUV radiation or EUV radiation);

[0021] - a support structure (e.g. a mask table) MT constructed to hold (e.g. 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;

[0022] - a substrate table (e.g. a wafer table) WT constructed to hold a substrate holder, the substrate holder being arranged 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. A substrate holder as described herein can be used to hold the substrate W on the substrate table WT; and

[0023] - a projection system (e.g. a refractive or reflective 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.

[0024] 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.

[0025] 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."

[0026] 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.

[0027] 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 phaseshift, 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 anincoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.

[0028] The term "projection system" used herein, like the term "illumination system", should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems or other types of optical components, 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". The projection system, like 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, as appropriate for the exposure radiation being used, or for other factors such as the use of a vacuum. It may be desired to use a vacuum for EUV radiation since other gases may absorb too much radiation. A vacuum environment may therefore be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps.

[0029] As depicted in Figure 1, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, as depicted in Figure 2, the lithographic apparatus 100 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).

[0030] The lithographic apparatus 100 may be of a type having two or more tables (or stage(s) or holder(s)) which may be referred to as dual stage, e.g., two or more substrate tables or a combination of one or more substrate tables and one or more sensor or measurement 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. The lithographic apparatus 100 may have two or more patterning device tables (or stage(s) or holder(s)) which may be used in parallel in a similar manner to substrate, sensor and measurement tables.

[0031] Referring to Figures 1 and 2, the illuminator IL receives a radiation beam from a radiation source SO in Figure 1 or a source collector apparatus SO in Figure 2. 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.

[0032] 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 ormore emission lines in the EUV range. In one such method, often termed laser produced plasma ("LPP") the plasma can be produced by irradiating a fuel, such as a droplet, stream or cluster of material having the desired line-emitting element, with a laser beam. The source collector apparatus SO may be part of an EUV radiation system including a laser, not shown in Figure 2, to provide the laser beam exciting the fuel. The resulting plasma emits output radiation, e.g. , EUV radiation, which is collected using a radiation collector, disposed in the source collector apparatus. The laser and the source collector apparatus may be separate entities, for example when a CO2 laser is used to provide the laser beam for fuel excitation. In such cases, the laser is not considered to form part of the lithographic apparatus and the radiation beam is passed from the laser to the source collector apparatus with the aid of a beam delivery system comprising, for example, suitable directing mirrors and / or a beam expander. In other cases the source may be an integral part of the source collector apparatus, for example when the source is a discharge produced plasma EUV generator, often termed as a DPP source.

[0033] The illuminator IL may comprise an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as G-O liter and o-inncr, 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, a condenser CO, a facetted field mirror device and / or a pupil mirror device. 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).

[0034] 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. With the aid of the second positioner PW and position sensor PSI (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 realizedusing 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.

[0035] The depicted apparatus could be used in at least one of the following modes:

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be employed.

[0040] Figure 3 shows the lithographic apparatus 100 in more detail, including the source collector apparatus SO, the illumination system IL, 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 very hot plasma 4210 is createdto emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 4210 is created by, for example, an electrical discharge causing an at least partially ionized plasma. Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapor or any other suitable gas or vapor may be required for efficient generation of the radiation. A plasma of excited tin (Sn) may be provided to produce EUV radiation.

[0041] The radiation emitted by the hot plasma 4210 is passed from a source chamber 4211 into a collector chamber 4212 via an optional gas barrier 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. The contaminant trap 4230 may include a channel structure. Contaminant trap 4230 may include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 4230 further indicated herein at least includes a channel structure, as known in the art.

[0042] 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 off 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.

[0043] 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 table WT.

[0044] More elements than shown may generally be present in illumination optics unit IL and projection system PS. The grating spectral filter 4240 may optionally be present, depending upon the type of lithographic apparatus 100. There may be more mirrors present than those shown in the Figures, for example there may be 1- 6 additional reflective elements present in the projection system PS than shown in Figure 3.

[0045] Collector optic CO, as illustrated in Figure 3, 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.

[0046] Alternatively, the source collector apparatus SO may be part of an LPP radiation system. A laser is arranged to deposit laser energy into a fuel, such as xenon (Xe), tin (Sn) or lithium (Li), creating the highly ionized plasma with electron temperatures of several ten'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 and focused onto an opening in an enclosing structure.

[0047] In many lithographic apparatus a fluid, in particular a liquid for example an immersion lithographic apparatus, is provided between the final element of the projection system using a liquid supply system IH to enable imaging of smaller features and / or increase the effective NA of the apparatus. Many types of liquid supply system are possible. The present invention is neither limited to any particular type of liquid supply system, nor to immersion lithography. The invention may be applied equally in any lithography. In an EUV lithography apparatus, the beam path is substantially evacuated and immersion arrangements are not used.

[0048] A controller 500 shown in Figure 1 controls the overall operations of the lithographic apparatus and in particular performs an optimization process described further below. Controller 500 can be embodied as a suitably -programmed general purpose computer comprising a central processing unit, volatile and non-volatile storage means, one or more input and output devices such as a keyboard and screen, one or more network connections and 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 implementation one computer can control multiple lithographic apparatuses. In an implementation, 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 substrate handling devices in a lithocell or cluster of which the lithographic apparatus forms a part. The controller 500 can also be configured to be subordinate to a supervisory controller of a lithocell or cluster and / or an overall controller of a fab.

[0049] Figure 4 is a schematic view of a module 10. The module 10 is for a lithographic apparatus 100, such as the lithographic apparatus 100 shown in any of Figures 1-3, for example.

[0050] In an embodiment the module 10 is replaceable within a lithographic apparatus 100. Alternatively, the module 10 may be integrated into the lithographic apparatus 100.

[0051] As shown in Figure 4, in an embodiment the module 10 comprises a component table. In the arrangement shown in Figure 4, the component table is the substrate table WT. However, it is not essential for the component table to be the substrate table WT. For example, in an alternative arrangement the component table may be a support structure MT for holding a patterning device MA.

[0052] The component table is configured to hold (e.g. support) a component. For example when the component table is a substrate table WT, then the substrate table WT is configured to hold asubstrate W. When the component table is a support structure MT, then the support structure MT is configured to hold a patterning device MA.

[0053] Embodiments of the invention are described primarily in the context of the component table being a substrate table WT and the component being a substrate W. However, it will be understood that the component table and the component are not required to be the substrate table WT and the substrate W.

[0054] As shown in Figure 4, in an embodiment the module 10 comprises a sensor member 13. As shown in Figure 4, in an embodiment the module 10 comprises a plurality of sensors 13. Alternatively, the module 10 may comprise a single sensor member 13.

[0055] In an embodiment the sensor member 13 is configured to sense a property relating to the component. For example, the sensor member 13 may be configured to measure a property of the component.

[0056] For example, a sensor member 13 may be configured to sense a position of the substrate W. The sensor member 13 may be configured to measure the position of the substrate W in the XY plane. A sensor member 13 may be configured to measure a position of the substrate W in the Z direction. A sensor member 13 may be configured to measure a shape of the substrate W.

[0057] A sensor member 13 may be configured to measure a property of a radiation beam B. For example the sensor member 13 may be configured to measure an energy level of radiation of the radiation beam B. The sensor member 13 may be configured to measure an aberration of the radiation beam B. The sensor member 13 may be configured to measure a shape of the radiation beam B. The sensor member 13 may be configured to measure a focus of the radiation beam B.

[0058] In an embodiment the sensor member 13 is part of a sensor system. The sensor system may comprise one or more marks and one or more detectors. The sensor member 13 may be a mark. The sensor member 13 may be a detector.

[0059] In an embodiment the sensor system is an interferometric sensor system. For example the interferometric sensor system may be an Integrated Fens Interferometry At Scanner “ILIAS” sensor system. Alternatively, the interferometric sensor system may be a Parallel ILIAS “PARIS” sensor system. Alternatively the sensor system may be a Transmission Image Sensor “ITS” system.

[0060] In an embodiment the sensor member 13 comprises a fiducial. The fiducial may comprise a reference mark.

[0061] The sensor member 13 may be configured to measure other properties relating to the substrate W or one or more properties relating to other components of the lithographic apparatus 100.

[0062] When the module 10 comprises a plurality of sensors 13, in an embodiment the sensors 13 are of the same type. This means that the sensors 13 are configured to measure the same property. Alternatively, the module 10 may comprise a plurality of different types of sensor member 13. That isthe module 10 may comprise sensors 13 configured to measure respective properties, for example of the substrate W.

[0063] As shown in Figure 4, in an embodiment the module 10 comprises a sensor clamping mechanism. In an embodiment the sensor clamping mechanism is configured to exert an active clamping force. The active clamping force for clamping the sensor member 13 is shown by the downward arrows 15 shown in Figure 4.

[0064] The active clamping force is for clamping the sensor member 13 relative to the component table (e.g. the substrate table WT). The sensor clamping mechanism is configured to exert an active clamping force rather than a passive clamping force. For example, in an embodiment the sensor clamping mechanism is configured to exert a vacuum clamping force for clamping the sensor member 13. In vacuum clamping, a space between the sensor member 13 and the substrate table WT may be partially evacuated so that the sensor member 13 is held in place by the higher pressure of gas or liquid above it.

[0065] However, it is not essential for the active clamping to be vacuum clamping. In an embodiment the sensor clamping mechanism is configured to exert an electrostatic clamping force for clamping the sensor member 13. In electrostatic clamping, a potential difference is established between the sensor member 13, or an electrode plated on its surface (or embedded within it), and an electrode provided on, or in the substrate table WT (and / or substrate holder). The two electrodes behave as a large capacitor and substantial clamping force can be generated with a reasonable potential difference. An electrostatic arrangement can be such that a single pair of electrodes clamp the sensor member 13. One or more electrodes may be provided on, or in, the substrate table WT (and / or a substrate holder).

[0066] An alternative to an active clamping force is a passive clamping force. For example, a sensor could be mounted to the substrate table WT via an intermediate body on kinematic mounts. This may provide a passive clamping force.

[0067] By providing the sensor clamping mechanism that is configured to exert an active clamping force for clamping the sensor member 13 relative to the substrate table WT, table positioning stability of the sensor member 13 may be improved. In particular, high accelerations are experienced by the sensor member 13 in use of a high-throughput lithographic apparatus 100. An embodiment of the invention is expected to achieve improved stability positioning accuracy during measurements and exposures of substrates W.

[0068] By providing that the sensor clamping mechanism is configured to exert an active clamping force, it may not be necessary to provide a glue bond for holding the sensor member 13 in place. Such a glue bond can undesirably vary over time. For example, the glue bond can be sensitive to moisture, which can vary as the pressure is varied during the use of the lithographic apparatus 100.By not requiring such a glue bond, the stability of the position of the sensor member 13 may be improved.

[0069] By providing that the sensor clamping mechanism is configured to exert an active clamping force, it may be relatively easy to replace the sensor member 13 when the sensor member 13 is required to be replaced. For example, the sensor clamping mechanism may be controlled so as to temporarily stop exerting the active clamping force. When the active clamping force is not being exerted, the sensor member 13 may be replaced. The active clamping force may then be switched on again so as to clamp the new sensor member 13. An embodiment of the invention is expected to facilitate replacement of a sensor member 13.

[0070] By providing the active clamping force, the sensor part that is replaced may be kept relatively lightweight. In particular, it may not be necessary to attach the sensor member 13 to an intermediate body to form a unit that can be readily replaced in the lithographic apparatus 100. By avoiding use of such an intermediate body which is attached to the sensor member 13, the mass of the sensor part to be replaced may be reduced. By reducing the mass of the sensor part to be replaced, the interface forces may be desirably reduced.

[0071] As shown in Figure 4, in an embodiment the sensor member 13 is clamped to the substrate table WT indirectly. An intermediate body may be provided between the substrate table WT and the sensor member 13. However, it is not necessary for the intermediate body to be permanently attached to the sensor member 13. Instead, the sensor member 13 may be clamped in a stack with the intermediate body and the substrate table WT by the active clamping force.

[0072] For example, as shown in Figure 4 the module 10 may comprise a sensor holder 14 (which may also be referred to as a sensor support). The sensor holder 14 is configured to hold (e.g. support) the sensor member 13. For example, the sensor holder 14 may be configured to hold the sensor member 13. As shown in Figure 4, in an embodiment the substrate table WT is configured to support the sensor holder 14. The sensor holder 14 may be located between the sensor member 13 and the substrate table WT.

[0073] In an embodiment, the sensor clamping mechanism is configured to exert the active clamping force for clamping the sensor member 13 relative to the sensor holder 14. For example, a space between the sensor member 13 and the sensor holder 14 may be partially evacuated so as to provide a vacuum clamping force. Additionally or alternatively, electrodes may be provided to the sensor member 13 and the sensor holder 14 so as to electrostatically clamp the sensor member 13 to the sensor holder 14.

[0074] In an embodiment, a space between the sensor holder 14 and the substrate table WT may be partially evacuated so as to provide a vacuum clamping force for clamping the sensor holder 14 to the substrate table WT. Additionally or alternatively, electrodes may be provided to the sensor holder14 and the substrate table WT so as to electrostatically clamp the sensor holder 14 to the substrate table WT.

[0075] In an embodiment, the sensor holder 14 may not be provided with electrodes. Electrodes may be provided to the sensor member 13 and / or the substrate table WT. The active electrostatic clamping force between the sensor member 13 and the substrate table WT may be sufficient to hold the sensor holder 14 between the sensor member 13 and the substrate table WT.

[0076] However, it is not essential for the sensor holder 14 to be provided. In an alternative arrangement, the sensor holder 14 may be omitted. For example, the sensor member 13 may be clamped directly to the substrate table WT. For example, a space between the sensor member 13 and the substrate table WT may be partially evacuated so as to provide a vacuum clamping force between the substrate table WT and the sensor member 13. Additionally or alternatively, electrodes may be provided to the sensor member 13 and the substrate table WT so as to electrostatically clamp the sensor member 13 to the substrate table WT.

[0077] As shown in Figure 4, in an embodiment the module 10 comprises a component holder (e.g. a substrate holder) 11. The component holder may be referred to as a component support. The component holder 11 is configured to hold (e.g. support) the substrate W. For example, the component holder 11 may be configured to hold the substrate W. As shown in Figure 4, in an embodiment the substrate table WT is configured to support the component holder 11. The component holder 11 may be located between the substrate W and the substrate table WT.

[0078] As shown in Figure 4, in an embodiment the module comprises a component clamping mechanism. For example, when the component is the substrate W, as shown in the arrangement of Figure 4, the component clamping mechanism may be referred to as a substrate clamping mechanism. As shown in Figure 4, in an embodiment the substrate clamping mechanism is configured to exert an active clamping force for clamping the substrate W to the component holder 11. For example, the active clamping force exerted by the substrate clamping mechanism is shown by the downward arrows 12 shown in Figure 4. The active clamping force may be, for example, a vacuum clamping force and / or an electrostatic clamping force. When the lithographic apparatus 100 is an EUV lithographic apparatus, the active clamping force may be an electrostatic clamping force.

[0079] As shown in Figure 4, in an embodiment the sensor member 13 is electrically connected to the substrate table WT. For example, the substrate table WT may comprise an electrical circuit 16. The electrical circuit 16 may be provided on a circuit board such as a printed circuit board. As shown in Figure 4, in an embodiment the sensor member 13 is electrically connected to the circuit 16. For example, the module 10 may comprise an electrical connector 17 configured to connect the sensor member 13 to the circuit 16. In an embodiment the electrical connector 17 is configured to transfer power and / or control signals to the sensor member 13. For example, the controller 500 may be configured to control the sensor member 13 via the electrical connector 17. In an embodiment theelectrical connector 17 is configured to transfer data from the sensor member 13. For example, the sensor member 13 may be configured to output measurement results via the electrical connector 17. The sensor member 13 may output the measurement results to the controller 500. In an embodiment the controller 500 is configured to control the lithographic apparatus 100 based on the measurement results from the sensor member 13.

[0080] In an embodiment the sensor clamping mechanism and the substrate clamping mechanism are controllable independently of each other. For example, the active clamping force exerted by the sensor clamping mechanism may be switched on, switched off, increased and / or decreased independently of the substrate clamping mechanism. Similarly, the active clamping force exerted by the substrate clamping mechanism may be switched on, switched off, increased and / or decreased independently of the sensor clamping mechanism.

[0081] In an embodiment the sensor member 13 may be clamped and unclamped without affecting the clamping state of the substrate W. For example, when the sensor member 13 is to be replaced, the sensor member 13 may be unclamped and replaced with another sensor member 13 while the substrate W remains clamped. However, it may be that the substrate W is required to be replaced more frequently than the sensor member 13. In an embodiment the substrate W may be unclamped, replaced and the replacement substrate W clamped, while the sensor member 13 remains clamped by the active clamping force exerted by the sensor clamping mechanism.

[0082] In an embodiment the sensor clamping mechanism and the substrate clamping mechanism are configured to exert the same type of clamping force. For example, in an embodiment both the sensor clamping mechanism and the substrate clamping mechanism are configured to exert a vacuum clamping force. In a further alternative embodiment, both the sensor clamping mechanism and the substrate clamping mechanism are configured to exert both a vacuum clamping force and an electrostatic clamping force.

[0083] However, it is not essential for the sensor clamping mechanism and the component clamping mechanism to exert the same type of clamping force. In an alternative embodiment the sensor clamping mechanism and the component clamping mechanism are configured to exert different types of clamping force. For example, in an embodiment the substrate clamping mechanism may be configured to exert a vacuum clamping force, while the sensor clamping mechanism is configured to exert an electrostatic clamping force. A clamping mechanism that exerts a vacuum clamping force may have associated with it one or more channels (e.g. provided by hoses) for evacuating gas from a space between the two parts to be clamped together. Meanwhile, a clamping mechanism configured to exert an electrostatic clamping force may be associated with electrical connectors for applying the potentials to the electrodes. An electrical connection may be preferable to a vacuum channel connection for providing less restriction to movement during a scanning process. For an EUVlithographic apparatus in which the substrate W is vacuum clamped, the sensor member 13 may be electrostatically clamped.

[0084] In an EUV lithographic apparatus, both the substrate W and the sensor member 13 may be electrostatically clamped.

[0085] As shown in Figure 4, in an embodiment the sensor holder 14 is formed integrally with the component holder 11. The component holder 11 of the lithographic apparatus 100 may be effectively extended so as to provide additional space for the sensor member 13 to be clamped onto the component holder 11. An embodiment of the invention is expected to improve clamping of the sensor member 13 without unduly increasing the number of parts of the lithographic apparatus 100.

[0086] However, it is not essential for the sensor holder 14 to be formed integrally with the component support. Figure 5 schematically depicts an alternative. Figure 5 schematically shows a module 10 in which the component is a patterning device MA. As shown in Figure 5, in an embodiment the sensor holder 14 is separate from the component holder 11. The sensor holder 14 may be manufactured and provided as a separate body from the component holder 11. The sensor holder 14 and the component holder 11 may be connected to each other via the support structure MT. However, a gap may be formed between the sensor holder 14 and the component holder 11 as shown in Figure 5. The sensor holder 14 may be provided as a dedicated support for the sensor member 13. The sensor holder 14 may be optimised for the sensor member 13.

[0087] As shown in Figure 4, in an embodiment the component and the sensor member are above the component table. Alternatively, as shown in Figure 5, the component and the sensor member may be below the component table. As a further alternative the component and the sensor member may clamped to a side of the component table.

[0088] Figure 5 schematically shows the sensor clamping mechanism exerting a vacuum clamping force. As shown in Figure 5, in an embodiment the sensor holder 14 comprises burls 19. The burls allow a space 25 to be provided between the sensor member 13 and the facing surface of the sensor holder 14. The space 25 may be partially evacuated. For example, an extraction opening 26 may be provided at the surface of the sensor holder 14 facing the space 25. The vacuum opening 26 may be in fluid communication with an under pressure 28 via a channel 27.

[0089] Figure 5 shows the patterning device clamping mechanism exerting a vacuum clamping force for clamping the patterning device MA. The component holder 11 may comprise burls 19 for providing a space 21 between the patterning device MA and the component holder 11. A vacuum opening 22 may be provided at the surface of the component holder 11 facing the space 21. The vacuum opening 22 may be in fluid communication with an under pressure 24 via a channel 23.

[0090] As shown in Figure 4, in an embodiment the module 10 comprises a thermal conditioner. The thermal conditioner is configured to thermally condition the sensor member 13 and the component (e.g. substrate W). For example, as shown in Figure 4, the thermal conditioner maycomprise at least one channel 18. The channel 18 may be defined in the substrate table WT. The channel 18 may be configured for passage of thermal conditioning fluid. The thermal conditioning fluid may be a liquid such as water or a gas, for example. As shown in Figure 4, in an embodiment the thermal conditioner comprises at least one channel 18 defined in the sensor holder 14 configured for passage of thermal conditioning fluid. In an embodiment the thermal conditioner comprises at least one channel 18 defined in the component holder 11 for passage of thermal conditioning fluid. In an embodiment the channels 18 defined in the component holder 11 and the sensor holder 14 may be in fluid communication with each other. Alternatively, they may be provided as separate circuits.

[0091] By providing the thermal conditioner, the temperature of the substrate W, the component holder 11, the sensor holder 14 and / or the sensor member 13 may be controlled more accurately. By controlling the temperature of the components, the possibility of undesirable deformations, for example, may be reduced.

[0092] As shown in Figure 4, in an embodiment the sensor member 13 may effectively share the same thermal conditioner as the substrate W. An embodiment of the invention is expected to improve thermal control of the sensor member 13 without unduly increasing the number of parts of the lithographic apparatus 100.

[0093] As shown in Figure 4, in an embodiment a plurality of sensors 13 are provided. In an embodiment the same sensor clamping mechanism is configured to exert an active clamping force for clamping the plurality of sensors 13 relative to the substrate table WT. Alternatively, a plurality of sensor clamping mechanisms may be provided. For example, a sensor clamping mechanism may be provided for each sensor member 13 individually. Separate clamping mechanisms may be controlled independently of each other. Alternatively, a plurality of sensor clamping mechanisms may be provided, with each sensor clamping mechanism configured to exert an active clamping force for clamping a group of sensors 13 relative to the substrate table WT.

[0094] Figure 6 is a schematic view, in cross-section, of an alternative module 10. As shown in Figure 6, the substrate W may be clamped via a vacuum clamping mechanism. The sensors 13 may be clamped via an electrostatic clamping mechanism. For example, as shown in Figure 6 in an embodiment one or more electrodes 20 are provided in the sensor holder 14. The electrodes 20 may be configured to exert an electrostatic clamping force for clamping the sensor member 13 relative to the sensor holder 14. Although not shown in Figure 6, electrodes may be provided for the substrate table WT and / or the sensor member 13.

[0095] As shown in Figure 6, in an embodiment the sensor holder 14 and the component holder 11 are arranged such that the substrate W and the sensor member 13 are supported at different positions along the Z direction. For example, Figure 6 shows the sensor holder 14 integrated with the component holder 11. The integrated support comprises a thinner portion where the sensor is to be supported. The integrated support comprises a thicker portion where the substrate W is to besupported. The sensor member 13 may be supported lower than the substrate W. In an alternative arrangement, one or more sensors 13 may be supported higher than the substrate W. In an arrangement, different sensors 13 may be supported at different heights.

[0096] Figure 6 shows an integrated support. In an alternative arrangement, the sensor holder 14 may be provided be provided separately from the component holder 11. The substrate W and the sensor member 13 may be supported at different heights by the respective component holder 11 and sensor holder 14.

[0097] Figure 7 is a plan view of a module 10 comprising four sensors 13. As shown in Figure7, in an embodiment the sensors 13 may be located radially outward of the substrate W. Figure 7 shows an arrangement in which the component holder 11 is provided separately from the sensor holder 14.

[0098] As shown in Figure 7, in an embodiment the module 10 comprises a plurality of sensor supports 14. For example, as shown in Figure 7, a separate sensor holder 14 may be provided for each respective sensor member 13. For example Figure 7 shows four sensor supports 14 for the four sensors 13. In an alternative arrangement, one or more of the sensor supports 14 may be configured to support a plurality of the sensors 13.

[0099] Figure 8 shows an alternative module 10 in plan view. The module 10 shown in Figure 8 comprises four sensors 13. As shown in Figure 8, in an embodiment the module 10 comprises a sensor holder 14 configured to support a plurality of sensors 13. In the arrangement shown in Figure8, the component holder 11 is provided separately from the sensor holder 14. Both the component holder 11 and the sensor holder 14 are supported by the substrate table WT.[000100] In an embodiment a method is provided for clamping a sensor member 13 relative to a component table of a lithographic apparatus 100. The method may comprise supporting the component (e.g. substrate W) with a component table (e.g. substrate table WT).[000101] In an embodiment the method comprises exerting an active clamping force for clamping the sensor member 13 relative to the component table. In an embodiment the method further comprises exerting an active clamping force (which may be the same or different clamping force) for clamping the component relative to the component table.[000102] In an embodiment the module 10 comprises a mechanical position limitation device. The mechanical position limitation device is configured to mechanically limit the position of the sensor member 13 relative to the component table (e.g. substrate table WT). The mechanical position limitation device is configured to exert a passive force for holding the sensor member 13 relative to the substrate table WT.[000103] For example, the active clamping force exerted by the sensor clamping mechanism may sometimes be not present. For example, when the module 10 is being transported (separately from the lithographic apparatus 100 or together with the lithographic apparatus 100), the clamping functionmay not be present. Similarly, when the module 10 is undergoing a service, the clamping function may not be present. The mechanical position limitation device may help to reduce the possibility of significant undesirable movement of the sensor member 13 relative to the substrate table WT. [000104] In an embodiment the mechanical position limitation device is controllable. For example, the mechanical position limitation device may be controlled so as to mechanically limit the position of the sensor member 13 when the clamping function is not present. The mechanical position limitation device may be controlled to not mechanically limit the position of the sensor member 13 when the lithographic apparatus 100 is being used. Alternatively, the mechanical position limitation device may be configured to always mechanically limit the position of the sensor member 13 relative to the substrate table WT. However, the mechanical position limitation device limits the position of the sensor member 13 to less type tolerances than the sensor clamping mechanism.[000105] Embodiments include the module being used in any lithographic apparatus. The lithographic apparatus may include any apparatus used in substrate manufacture, testing and inspection, such as an electron-beam inspection apparatus.[000106] The various embodiments may also be described by the following clauses:1. A module for a lithographic apparatus comprising: a component table configured to hold a component; a sensor member; and a sensor clamping mechanism configured to exert an active clamping force for clamping the sensor member relative to the component table.2. The module of clause 1, comprising: a sensor holder configured to hold the sensor member, wherein the component table is configured to hold the sensor holder, wherein the sensor clamping mechanism is configured to exert the active clamping force for clamping the sensor member relative to the sensor holder.3. The module of clause 1 or 2, wherein the sensor clamping mechanism is configured to exert a vacuum clamping force for clamping the sensor member.4. The module of clause 1 or 2, wherein the sensor clamping mechanism is configured to exert an electrostatic clamping force for clamping the sensor member.5. The module of any preceding clause, comprising: a component holder configured to hold the component, wherein the component table is configured to hold the component holder.6. The module of clause 5, comprising: a component clamping mechanism configured to exert an active clamping force for clamping the component to the component holder.7. The module of clause 6, wherein the component clamping mechanism configured to exert a vacuum clamping force for clamping the component.8. The module of clause 6, wherein the component clamping mechanism configured to exert an electrostatic clamping force for clamping the component. . The module of any of clauses 6-8, wherein the sensor clamping mechanism and the component clamping mechanism are controllable independently of each other.10. The module of any of clauses 6-9, wherein a vacuum clamping force is a type of clamping force and an electrostatic clamping force is a different type of clamping force, wherein the sensor clamping mechanism and the component clamping mechanism are configured to exert the same type of clamping force.11. The module of any of clauses 5-10 when dependent on clause 2, wherein the sensor holder is formed integrally with the component holder.12. The module of any of clauses 5-10 when dependent on clause 2, wherein the sensor holder is separate from the component holder.13. The module of any preceding clause, comprising: a thermal conditioner configured to thermally condition the sensor member and the component.14. The module of clause 13, wherein the thermal conditioner comprises at least one channel defined in the component table configured for passage of thermal conditioning fluid.15. The module of clause 13 or 14, wherein the thermal conditioner comprises at least one channel defined in the sensor holder configured for passage of thermal conditioning fluid.16. The module of any preceding clause, wherein the sensor member is configured to measure a property of the component.17. The module of clause 16, wherein the sensor member is configured to measure a shape of the component.18. The module of clause 16 or 17, wherein the sensor member is configured to measure a position of the component.19. The module of any preceding clause, wherein the sensor member is configured to measure a property of a radiation beam.20. The module of clause 19, wherein the sensor member is configured to measure an aberration of the radiation beam.21. The module of clause 19 or 20, wherein the sensor member is configured to measure a focus of the radiation beam.22. The module of any of clauses 19-21, wherein the sensor member is configured to measure an energy level of the radiation beam.23. The module of any preceding clause, wherein the sensor member is part of an interferometric sensor system.24. The module of clause 23, wherein the interferometric sensor system is an Integrated Lens Interferometry At Scanner sensor system.25. The module of clause 23, wherein the interferometric sensor system is a Parallel Integrated Lens Interferometry At Scanner sensor system.26. The module of any of clauses 1-22, wherein the sensor member is part of a Transmission Image Sensor system.27. The module of any preceding clause, wherein the sensor member comprises a fiducial.28. The module of clause 27, wherein the fiducial comprises a reference mark.29. The module of any preceding clause, comprising a plurality of sensor members.30. The module of clause 29, wherein the sensor clamping mechanism is configured to exert an active clamping force for clamping the plurality of sensor members relative to the component table.31. The module of clause 29, comprising a plurality of sensor clamping mechanisms configured to exert an active clamping force for clamping respective sensor members relative to the component table.32. The module of any preceding clause, wherein the component table is a substrate table and the component is a substrate to be patterned by the lithographic apparatus.33. The module of any preceding clause, wherein the component table is a patterning device table and the component is a patterning device.34. A lithographic apparatus comprising: the module of any preceding clause.35. A method for clamping a sensor member relative to a component table of a lithographic apparatus, the method comprising: holding a component with a component table; and exerting an active clamping force for clamping the sensor member relative to the component table.36. The method of clause 35, comprising: exerting an active clamping force for clamping the component relative to the component table.37. The method of clause 36, comprising: reducing or stopping the active clamping force clamping the component, so as to replace the component, while maintaining the active clamping force for clamping the sensor member.[000107] Although specific reference may have been made above to the use of embodiments of the invention in the context of object inspection and optical lithography, it will be appreciated that the invention, where the context allows, is not limited to these contexts and may be used in other applications, for example imprint lithography.[000108] Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also beimplemented as instructions stored on a machine -readable medium, which may be read and executed by one or more processors. A machine -readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine -readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.[000109] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. A module for a lithographic apparatus comprising: a component table configured to hold a component; a sensor member; and a sensor clamping mechanism configured to exert an active clamping force for clamping the sensor member relative to the component table.

2. The module of claim 1, comprising: a sensor holder configured to hold the sensor member, wherein the component table is configured to hold the sensor holder, wherein the sensor clamping mechanism is configured to exert the active clamping force for clamping the sensor member relative to the sensor holder.

3. The module of claim 1 or 2, wherein the sensor clamping mechanism is configured to exert a vacuum clamping force or an electrostatic clamping force for clamping the sensor member.

4. The module of any preceding claim, comprising: a component holder configured to hold the component, wherein the component table is configured to hold the component holder.

5. The module of claim 4, comprising: a component clamping mechanism configured to exert an active clamping force for clamping the component to the component holder.

6. The module of claim 5, wherein the component clamping mechanism configured to exert a vacuum clamping force or an electrostatic clamping force for clamping the component.

7. The module of any of claims 5-6, wherein the sensor clamping mechanism and the component clamping mechanism are controllable independently of each other.

8. The module of any of claims 4-7 when dependent on claim 2, wherein the sensor holder is formed integrally with the component holder.

9. The module of any preceding claim, comprising: a thermal conditioner configured to thermally condition the sensor member and thecomponent.

10. The module of any preceding claim, wherein the sensor member is configured to measure a property of the component, a shape of the component, or a position of the component.

11. The module of any preceding claim, wherein the sensor member is configured to measure a property of a radiation beam, an aberration of the radiation beam, a focus of the radiation beam or an energy level of the radiation beam.

12. The module of any preceding claim, wherein the sensor member is part of an interferometric sensor system, is an Integrated Lens Interferometry At Scanner sensor system, is a Parallel Integrated Lens Interferometry At Scanner sensor system or is part of a Transmission Image Sensor system.

13. The module of any preceding claim, wherein the component table is a substrate table and the component is a substrate to be patterned by the lithographic apparatus.

14. A lithographic apparatus comprising: the module of any preceding claim.

15. A method for clamping a sensor member relative to a component table of a lithographic apparatus, the method comprising: holding a component with a component table; and exerting an active clamping force for clamping the sensor member relative to the component table.

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