An arrangement for a lithographic apparatus

Abstract

An arrangement for a lithographic apparatus, comprising: a patterning device (MA) configured to impart a pattern to a beam of radiation, the patterning device (MA) comprising a patterning surface (110) with a pattern thereon; a support structure (100) configured to support the patterning device (MA); and a protective membrane (131) disposed in front of the patterning surface (110); wherein the protective membrane (131) is electrically connected to the support structure (100). Further, a method of applying a bias voltage to a patterning device (MA) in a lithographic apparatus, comprising: determining whether a protective membrane (131) is disposed in front of a patterning surface (110); in a case that the lithographic apparatus is in the production state and the protective membrane (131) is determined to be disposed in front of the patterning surface (110), applying a first bias voltage to the patterning surface (110); and in a case that the protective membrane (131) is determined not disposed, applying a second bias voltage to the patterning surface (110).

Description

AN ARRANGEMENT FOR A LITHOGRAPHIC APPARATUSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 24183295.5 which was filed on 20 June 2024 and which is incorporated herein in its entirety by reference.FIELD

[0002] The present invention relates to an arrangement for a lithographic apparatus, a lithographic apparatus, a method of supporting a patterning device on a support structure, a method of applying a bias voltage to a patterning device, a controller for a lithographic apparatus, and a method of manufacturing device.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.

[0004] Lithography is widely recognized as one of the key steps in the manufacture of ICs and other devices and / or structures. However, as the dimensions of features made using lithography become smaller, lithography is becoming a more critical factor for enabling miniature IC or other devices and / or structures to be manufactured.

[0005] A theoretical estimate of the limits of pattern printing can be given by the Rayleigh criterion for resolution as shown in equation (1):where is the wavelength of the radiation used, NA is the numerical aperture of the projection system used to print the pattern, kl is a process-dependent adjustment factor, also called the Rayleigh constant, and CD is the feature size (or critical dimension) of the printed feature. It follows from Equation (1) that reduction of the minimum printable size of features can be obtained in three ways: by shortening the exposure wavelength X, by increasing the numerical aperture NA or by decreasing the value of kl.

[0006] In order to shorten the exposure wavelength and, thus, reduce the minimum printable size, it has been proposed to use an extreme ultraviolet (EUV) radiation source. EUV radiation is electromagnetic radiation having a wavelength within the range of 10-20 nm, for example within the range of 13-14 nm. It has further been proposed that EUV radiation with a wavelength of less than 10 nm could be used, for example within the range of 5-10 nm such as 6.7 nm or 6.8 nm. Such radiation is termed extreme ultraviolet radiation or soft x-ray radiation. Possible sources include, for example, laser-produced plasma sources, discharge plasma sources, or sources based on synchrotron radiation provided by an electron storage ring.

[0007] Once a beam of EUV radiation has been generated, it is directed through the lithographic apparatus by one or more optical elements to a patterning surface of a patterning device. The patterning surface of the patterning device imparts a desired pattern to the beam of EUV radiation. The patterned beam of radiation is then directed to the substrate by one or more optical elements.

[0008] As a result of the photoelectric effect, the EUV radiation incident on the patterning surface may cause electrons to be ejected from the patterning surface and into the environment surrounding the patterning device. This may cause the patterning surface to become positively charged. The EUV radiation may excite hydrogen molecules within the environment surrounding the patterning device to form a plasma. The electrons ejected from the patterning surface may also contribute to this plasma.

[0009] Free negative charges in the plasma may cause contaminant particles in the environment surrounding the patterning device to become negatively charged. The negatively charged contaminant particles may be attracted to the positively charged patterning surface. Consequently, contaminant particles may be deposited onto the patterning surface. The contaminant particles deposited on the patterning surface may absorb and / or scatter EUV radiation incident on the patterning surface. Consequently, the contaminant particles may lead to the presence of imperfections in the pattern projected onto the substrate, which may cause defectivity in the substrate, and reduce yield of ICs.

[0010] In some lithographic apparatuses, a protective membrane (e.g. a pellicle) is disposed in front of the patterning surface to prevent contaminant particles from being deposited on the patterning surface. Particles deposited on the protective membrane remain far from the focal plane of lithographic system, and thus do not lead to imperfections in the pattern projected onto the substrate. When a protective membrane is disposed in front of the patterning surface, hydrogen ions (H+) in the plasma generated by the EUV radiation may be implanted into the protective membrane. Additionally or alternatively, hydrogen ions (H+) can cause physical / chemical sputtering of the material of the protective membrane. The implantation of hydrogen ions into the protective membrane and / or the physical sputtering of the material of the protective membrane can cause degradation (e.g. mechanical weakening) of the protective membrane. Thus, the interaction of hydrogen ions with the protective membrane may decrease the lifetime of the protective membrane.SUMMARY OF THE INVENTION

[0011] An aim of the present invention is to reduce degradation of the protective membrane during exposure of the patterning surface to extend the lifetime of the protective membrane. A particular aim of the present invention is to reduce degradation of the protective membrane while also reducing the amount of contaminant particles that are deposited on the patterning surface.

[0012] According to the present disclosure, there is provided an arrangement for a lithographic apparatus, the arrangement comprising: a patterning device configured to impart a pattern to a beam of radiation, the patterning device comprising a patterning surface with a pattern thereon; a support structure configured to support the patterning device; and a protective membrane disposed in front of the patterning surface; wherein the protective membrane is electrically connected to the support structure.

[0013] Also according to the present disclosure, there is provided a method of applying a bias voltage to a patterning device in a lithographic apparatus, the method comprising: determining whether a protective membrane is disposed in front of a patterning surface of the patterning device; in a case that the lithographic apparatus is in the production state and the protective membrane is determined to be disposed in front of the patterning surface, applying a first bias voltage to the patterning surface; and in a case that the lithographic apparatus is in the production state and the protective membrane is determined not to be disposed in front of the patterning device, applying a second bias voltage to the patterning surface.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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.

[0015] Figure 1 schematically depicts a lithographic apparatus.Figure 2 schematically depicts a more detailed view of the lithographic apparatus.Figure 3 schematically depicts a support structure and a patterning device in a lithographic apparatus.Figure 4 schematically depicts a support structure, a patterning device and a protective membrane in a lithographic apparatus.Figure 5A schematically depicts a section view of an arrangement comprising a support structure and a patterning device.Figure 5B schematically depicts a bottom view of the arrangement depicted in Figure 5A.Figure 5C schematically depicts a non-patterning surface of the patterning device of the arrangement depicted in Figures 5A and 5B.Figure 6 schematically depicts a support surface of a support structure.Figure 7 A schematically depicts a section view of an arrangement comprising a support structure and a patterning device.Figure 7B schematically depicts a bottom view of the arrangement depicted in Figure 7A.Figure 7C schematically depicts a non-patterning surface of the patterning device of the arrangement depicted in Figures 7 A and 7B.Figure 8A schematically depicts a section view of an arrangement comprising a support structure, a patterning device, and a protective membrane disposed in front of a patterning surface of the patterning device.Figure 8B schematically depicts a bottom view of the patterning device from the arrangement depicted in Figure 8A.Figure 8C schematically depicts a non-patterning surface 111 of the patterning device of the arrangement depicted in Figures 8A and 8B.Figure 9A schematically depicts a section view of a patterning device and a protective membrane disposed in front of a patterning surface of the patterning device, wherein the protective membrane is electrically connected to the patterning device.Figure 9B schematically depicts a bottom view of the protective membrane from the arrangement depicted in Figure 9A.Figure 10A schematically depicts a section view of a patterning device and a protective membrane disposed in front of a patterning surface of the patterning device, wherein the protective membrane is electrically connected to the patterning device.Figure 10B schematically depicts a bottom view of the protective membrane from the arrangement depicted in Figure 10A.Figure 11 A schematically depicts a section view of a patterning device and a protective membrane disposed in front of a patterning surface of the patterning device, wherein the protective membrane is electrically connected to the patterning device.Figure 1 IB schematically depicts a bottom view of the protective membrane from the arrangement depicted in Figure 11 A.Figure 12A schematically depicts a section view of a patterning device and a protective membrane disposed in front of a patterning surface of the patterning device, wherein the protective membrane is electrically connected to the patterning device.Figure 12B schematically depicts a bottom view of the protective membrane from the arrangement depicted in Figure 12 A.Figure 13 schematically depicts conductive support protrusions in contact with a non-patterning surface of a patterning device.Figure 14 schematically depicts conductive support protrusions, a non-patterning surface of a patterning device, and a layer of conductive material disposed between the conductive support protrusions and the non-patterning surface.Figure 15A schematically depicts an arrangement comprising a support structure, a patterning device, a protective membrane disposed in front of a patterning surface of the patterning device, and a connecting element, wherein the patterning device is to be loaded onto the support structure.Figure 15B schematically depicts the arrangement of Figure 15 A, wherein the patterning device is supported by the support structure.Figure 16 schematically depicts an arrangement comprising a support structure, a patterning device, a protective membrane disposed in front of a patterning surface of the patterning device, and a connecting element, wherein the patterning device is supported by the support structure.Figure 17 depicts a method of applying a bias voltage to a patterning surface and / or protective membrane.The features shown in the Figures are not necessarily to scale, and the size and / or arrangement depicted is not limiting. It will be understood that the Figures include optional features which may not be essential to the invention. Furthermore, not all of the features of the apparatus are depicted in each of the figures, and the Figures may only show some of the components relevant for describing a particular feature.DETAILED DESCRIPTION

[0016] Figure 1 schematically depicts a lithographic apparatus 100 including a radiation source SO according to one embodiment of the invention. The apparatus 100 comprises: an illumination system (or illuminator) IL configured to condition a radiation beam B (e.g., EUV radiation). 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; 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 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.

[0017] The illumination system IL 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.

[0018] The support structure MT holds the patterning device MA 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 MA. The support structure MT may be a frame or a table, for example, which may befixed or movable as required. The support structure MT may ensure that the patterning device MA is at a desired position, for example with respect to the projection system PS.

[0019] The term “patterning device” should be broadly interpreted as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section such as to create a pattern in a target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a particular functional layer in a device being created in the target portion C, such as an integrated circuit.

[0020] Examples of patterning devices include masks, programmable mirror arrays, and programmable liquid-crystal display (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.

[0021] The projection system PS, like the illumination system IL, 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.

[0022] As here depicted, the lithographic apparatus 100 is of a reflective type (e.g., employing a reflective mask).

[0023] The lithographic apparatus 100 may be of a type having two (dual stage) or more substrate tables WT (and / or two or more support structures MT). In such a “multiple stage” lithographic apparatus the additional substrate tables WT (and / or the additional support structures MT) may be used in parallel, or preparatory steps may be carried out on one or more substrate tables WT (and / or one or more support structures MT) while one or more other substrate tables WT (and / or one or more other support structures MT) are being used for exposure.

[0024] Referring to Figure 1, the illumination system IL receives an extreme ultraviolet radiation beam from the radiation source SO. The radiation source SO may be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL) or any other radiation source that is capable of generating EUV radiation. Methods to produce EUV light 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. In laser produced plasma (“LPP”), the required plasma can be produced by irradiating a fuel, such as a droplet, stream or cluster of material having the required line-emitting element, with a laser beam. The radiation source SO may be part of an EUV radiation system including a laser, not shown in Figure 1 , for providing the laser beam exciting the fuel. The resulting plasma emits output radiation, e.g., EUV radiation, which is collected using aradiation collector, disposed in the radiation source SO. The laser and the radiation source SO may be separate entities, for example when a CO2 laser is used to provide the laser beam for fuel excitation.

[0025] In such cases, the laser is not considered to form part of the lithographic apparatus 100 and the radiation beam B is passed from the laser to the radiation source SO 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 radiation source SO, for example when the source is a discharge produced plasma EUV generator, often termed as a DPP source.

[0026] The illumination system IL may comprise an adjuster for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as o-outer and o-inner, respectively) of the intensity distribution in a pupil plane of the illumination system IL can be adjusted. In addition, the illumination system IL may comprise various other components, such as facetted field and pupil mirror devices. The illumination system IL may be used to condition the radiation beam B, to have a desired uniformity and intensity distribution in its cross-section.

[0027] 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 MA. After being reflected from the patterning device (e.g., mask) MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam B 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 B. Similarly, the first positioner PM and another position sensor PSI can be used to accurately position the patterning device (e.g., mask) MA with respect to the path of the radiation beam B. The patterning device (e.g., mask) MA and the substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2.

[0028] A controller 500 controls the overall operations of the lithographic apparatus 100 and in particular performs an operation process described further below. Controller 500 can be embodied as a suitably-programmed general purpose computer comprising a central processing unit, volatile and nonvolatile 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 100. It will be appreciated that a one-to-one relationship between controlling computer and lithographic apparatus 100 is not necessary. In an embodiment of the invention one computer can control multiple lithographic apparatuses 100. In an embodiment of the invention, multiple networked computers can be used to control one lithographic apparatus 100. 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 100 forms a part. The controller 500 can also be configured to be subordinate to a supervisory control system of a lithocell or cluster and / or an overall control system of a fab.

[0029] Figure 2 shows the lithographic apparatus 100 in more detail, including the radiation source SO, the illumination system IL, and the projection system PS. The radiation source SO is configured to generate an EUV radiation beam B and to supply the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS and a substrate table WT configured to support a substrate W.

[0030] The illumination system IL is configured to condition the EUV radiation beam B before the EUV radiation beam B is incident upon the patterning device MA. Thereto, the illumination system IL may include a facetted field mirror device 10 and a facetted pupil mirror device 11. The faceted field mirror device 10 and faceted pupil mirror device 11 together provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The illumination system IL may include other mirrors or devices in addition to, or instead of, the faceted field mirror device 10 and faceted pupil mirror device 11.

[0031] After being thus conditioned, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B’ is generated. The projection system PS is configured to project the patterned EUV radiation beam B’ onto the substrate W. For that purpose, the projection system PS may comprise a plurality of mirrors 13,14 which are configured to project the patterned EUV radiation beam B ’ onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B’, thus forming an image with features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is illustrated as having only two mirrors 13,14 in Figure 1, the projection system PS may include a different number of mirrors (e.g. six or eight mirrors).

[0032] The substrate W may include previously formed patterns. Where this is the case, the lithographic apparatus LA aligns the image, formed by the patterned EUV radiation beam B’, with a pattern previously formed on the substrate W.

[0033] A relative vacuum, i.e. a small amount of gas (e.g. hydrogen) at a pressure well below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL, and / or in the projection system PS.

[0034] The radiation source SO may be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL) or any other radiation source that is capable of generating EUV radiation.

[0035] Figure 3 schematically depicts, in cross-section, a portion of a support structure 100 and a patterning device MA. The support structure 100 is an example of the support structure MT described above. The cross-section extends in a vertical plane (i.e., parallel to the z-direction). The support structure MT supports the patterning device MA during lithographic operations. The support structure100 may be considered to be part of a lithographic apparatus or may be considered to be part of an apparatus that is separate to the lithographic apparatus.

[0036] The patterning device MA to be supported by the support structure 100 may comprise a patterning surface 110 and a non-patterning surface 111. The patterning surface 110 and the nonpatterning surface 111 may be substantially parallel. The patterning surface 110 may comprise a patterning region. The patterning region may be configured to impart a pattern to a beam of radiation that is to be projected onto a substrate W. The patterning region may be configured to reflect a beam of radiation such that the reflected beam of radiation is a patterned beam of radiation. The nonpatterning surface 111 is opposite the patterning surface 110.

[0037] Both the support structure 100 and the patterning device MA may be contained within a patterning device environment 90. The patterning device environment 90 may be separated from an external environment surrounding the lithographic apparatus and / or other components within the lithographic apparatus such that gases and contaminant particles are substantially prevented from entering the patterning device environment 90. The patterning device environment 90 may be partially evacuated of gas. That is, the pressure within the patterning device environment 90 may be less than ambient pressure. This is to limit the attenuation of EUV radiation as it travels through the patterning device environment 90. Even though the pressure within the patterning device 90 is less than ambient pressure, it is not a perfect vacuum, so gas particles are present in the patterning device environment 90.

[0038] The support structure 100 may comprise a support surface 102. When the patterning device MA is clamped to the support structure 100, the support surface 102 may face the non-patterning surface 111 of the patterning device MA. When the patterning device MA is clamped to the support structure 100, the patterning surface 110 of the patterning device MA may face away from the support surface 102. The support surface 102 may be generally planar. The support structure 100 may be configured such that, when the patterning device MA is clamped to the support structure 100, the support surface 102 of the support structure 100 is substantially parallel to the non -patterning surface 111 of the patterning device MA. In some embodiments, a dielectric layer is provided to the support structure 100, and the dielectric layer forms the support surface 102.

[0039] The support structure 100 may comprise a plurality of electrodes 104A, 104B. The plurality of electrodes 104A, 104B may be buried within the body of the support structure 100. For instance, the plurality of electrodes 104 A, 104B may be buried beneath the support surface 102 of the support structure 100. Each of the plurality of electrodes 104A, 104B may be connected to a power supply such that a potential can be applied to each of the plurality of electrodes 104A, 104B.

[0040] The support structure 100 may comprise a plurality of support protrusions 106. The plurality of support protrusions 106 will henceforth be referred to as burls 106. The plurality of burls 106 may protrude from the support surface 102 of the support structure 100. The portion of the support surface 102 from which the plurality of burls protrude may be referred to as a clamping surface.

[0041] The support structure 100 may be configured such that distal ends (that is, ends furthest from the support surface 102 of the support structure 100) of the plurality of burls 106 form a planar surface. When the patterning device MA is clamped to the support structure 100, the non-patterning surface 111 of the patterning device MA may be in contact with the distal ends of the plurality of burls 106. Consequently, the support surface 102 of the support structure 100, and the electrodes 104A, 104B that may be buried beneath the support surface 102 of the support structure, may be separated from the nonpatterning surface 111 of the patterning device MA.

[0042] The plurality of electrodes 104A, 104B may each be rectangular in shape. However, this is not essential to the present invention, and the shape of the plurality of electrodes 104A, 104B is not particularly limited. The plurality of electrodes 104 A, 104B may be distributed uniformly over the support surface 102 of the support structure 100. However, the particular arrangement of the plurality of electrodes 104A, 104B over the support surface 102 of the support structure is not particularly limited. As depicted in Figure 3, two electrodes 104A, 104B are present the support structure 100. However, the number of electrodes 104 A, 104B in the support structure is not particularly limited, and could be any number such as 2, 3, 4, 5, 10, 20 or more.

[0043] The patterning device MA to be clamped by the support structure 100 may be provided with a conductive coating 112 which forms the patterning surface 110 and a conductive coating 113 which forms the non-patterning surface 111. In the patterning device MA depicted in Figure 3, the conductive coating 112 and the conductive coating 113 are substantially electrically isolated. That is, the conductive coating 112 may be electrically isolated from the conductive coating 113, and both the conductive coating 112 and the conductive coating 113 may each be substantially electrically isolated from other components within the lithographic apparatus. Consequently, electric charge may build up on the patterning surface 110 and the non-patterning surface 111.

[0044] When a potential is applied to the plurality of electrodes 104A, 104B, a high electric field is established between the plurality of electrodes 104A, 104B and the second conductive coating 113 of the patterning device MA, causing the patterning device MA to be attracted to the plurality of electrodes 104A, 104B. In particular, the potential applied to the plurality of electrodes 104A, 104B causes charge separation to occur within the second conductive coating 113. The displacement of charges within the second conductive coating 113 means that an attractive force may be established between the plurality of electrodes 104A, 104B and the second conductive coating 113. Consequently, the support structure 100 may exert a clamping force on the patterning device MA.

[0045] The potential applied to the plurality of electrodes 104A, 104B may be large enough for the clamping force exerted on the patterning device MA by the support structure to overcome the gravitational force exerted on the patterning device MA. The required potential may be dependent on the mass of the patterning device MA and the separation between the plurality of electrodes 104A, 104B and the second conductive coating 113. The magnitude of the potential applied to the plurality of electrodes 104A, 104B may be in the order of several kV. For example, the magnitude of the potentialapplied to the plurality of electrodes 104A, 104B may be greater than 100 V, preferably greater than 300 V, and further preferably greater than 1 kV. The magnitude of the potential applied to the plurality of electrodes 104A, 104B may be less than 100 kV, preferably less than 50 kV, and further preferably less than 25 kV.

[0046] The electrodes 104A, 104B may be controlled by a control system. The control system may be configured to control the electrodes 104A, 104B to be in one of two or more states. The two or more states may comprise a first state and a second state.

[0047] In the first state, the magnitude of the voltages applied to the electrodes 104A, 104B may be greater than 100 V or even greater than 1 kV. In the first state, the voltage applied to a portion (e.g. one half) of the electrodes 104A may have the opposite polarity to the voltage applied to another portion (e.g. the other half) of the electrodes 104B. The magnitude of the voltage applied to the portion of electrodes 104A may be substantially the same as the magnitude of the voltage applied to the another portion of electrodes 104B.

[0048] In the second state, the magnitude of the voltages applied to the electrodes 104A, 104B may be less 100 V, or even less than 10 V. For example, the electrodes 104A, 104B may be grounded in the second state.

[0049] The conductive coating on the non-patterning surface 111 of the patterning device AM may be capacitively coupled to the electrodes 104A, 104B when the patterning device MA is close to or supported by the support structure. Thus, the voltage of the non-patterning surface 111 can be affected by the voltages of the electrodes 104A and 104B. Additionally or alternatively, the voltage of the nonpatterning surface surface 111 can be affected by a charge present on the support surface 111 , or by a charge present on a patterning surface 110.

[0050] In some embodiments, the support structure 100 may not comprise clamping electrodes 104A, 104B, and may instead use alternative clamping means to clamp the patterning device MA to the support structure MT. For example, the support structure 100 may generate an under-pressure between the patterning device MA and the support structure 100 such that the patterning device MA is clamped to the support structure 100.

[0051] Masking blades 120 may be provided within the lithographic apparatus adjacent to the patterning surface 110 of the patterning device MA. For example, the masking blades 120 may be provided such that they are displaced from the patterning surface 110 in the z-direction. The masking blades 120 may be configured to selectively mask the patterning device MA from the beam of radiation during exposure. The lithographic apparatus may be configured such that the masking blades 120 can be moved in the horizontal plane to provide different levels of masking for the patterning device MA.

[0052] Figure 4 schematically depicts a support structure 100, and a patterning device covered by a protective membrane 131. The protective membrane 131 may be a thin film. The protective membrane 131 may be referred to as a pellicle. The protective membrane 131 may be provided opposite the patterning surface 110. For example, the protective membrane 131 may be provided such that it isdisplaced from the patterning surface 110 in the z-direction. The protective membrane 131 may be configured to protect the patterning device MA from contaminant particles within the patterning device environment 90.

[0053] In order to minimize the absorption of EUV radiation by the protective membrane 131, the protective membrane 131 is very thin and consequently very fragile. The protective membrane 131 may absorb less than 15% of radiation passing therethrough, preferably less than 10% of EUV radiation passing through, and further preferably less than 5% of EUV radiation passing therethrough.

[0054] The protective membrane 131 may be supported by a protective membrane frame 132. The protective membrane 131 may be stretched across the protective membrane frame 132. The protective membrane 131 may be under tension.

[0055] The protective membrane frame 132 may be coupled to the patterning surface 110. For example, the protective membrane frame 132 may be coupled to a perimeter region of the patterning surface 110, radially outward of a region of the patterning surface 110 on which the pattern which is to be projected onto the substrate W is formed.

[0056] The protective membrane may be formed from a material comprising carbon nanotubes. Such a protective membrane may be formed of a bundle of carbon nanotubes. The bundle of carbon nanotubes may form a gas-permeable membrane. Further detail on protective membranes formed from a material comprising carbon nanotubes is provided in WO 2021037662 Al and WO 2024056548 Al, the entirety of which are hereby incorporated by reference. Alternatively, the protective membrane may be formed of a material comprising a compound comprising molybdenum, silicon and nitrogen. The compound comprising molybdenum, silicon and nitrogen may be MoSiN. Further detail on protective membranes formed of a material comprising MoSiN is provided in WO 2019086643 Al , the entirety of which is hereby incorporated by reference.

[0057] In the arrangement depicted in Figure 4, the protective membrane 131 is substantially electrically isolated. That is, the protective membrane 131 is substantially electrically isolated from the patterning device MA and substantially electrically isolated from other components within the lithographic apparatus. The protective membrane may comprise a free-standing film and a solid frame that supports the free-standing film. Generally (i.e. in pre-existing arrangements), the free-standing film is electrically conducting and the solid frame is electrically insulating.

[0058] Contaminant particles P may be present in the patterning device environment 90. Despite the separation of the patterning device environment 90 from the external environment and / or other components within the lithographic apparatus, it is possible that some contaminant particles may enter the patterning device environment 90 from the external environment and / or other locations in the lithographic apparatus. Also, contaminant particles may be generated within the patterning device environment 90 by mechanisms such as abrasive wear, which occurs when there is relative motion between contacting surfaces.

[0059] As explained above, the lithographic apparatus may be an EUV lithographic apparatus. That is, the lithographic apparatus may be configured to project a beam of EUV radiation onto the substrate W. EUV radiation is electromagnetic radiation having a wavelength within the range of 10-20 nm, for example within the range of 13-14 nm, for example 13.5 nm. During exposure, the beam of EUV radiation may be incident on the patterning region of the patterning surface 110 of the patterning device MA. This may cause the release of electrons from the patterning surface 110, as a result of the photoelectric effect, as shown in Figure 3. Consequently, the patterning surface 110 may become positively charged.

[0060] The EUV radiation within the patterning device environment 90 may also cause the contaminant particles P to become negatively charged. This may be because the presence of EUV radiation within the patterning device environment 90 results in the formation of plasma from gas molecules within the patterning device environment 90. Plasma may be formed in the patterning device environment 90 because photons within the beam of EUV radiation ionize hydrogen molecules, generating free electrons. In an example using 13.5 nmEUV radiation, each photon may have an energy of around 92 eV, with the ionization energy of molecular hydrogen being around 15 eV. Thus, the generated free electrons may have sufficient energy (e.g. >75 eV) and range to create a secondary plasma relatively far from the initial ionization event. An electron released in this way (i.e. having an energy of around 75 eV) may ionize one, two, or even three further hydrogen molecules. Thus, even if the primary plasma is created only where EUV photons are incident, a secondary plasma may be created throughout the clamping environment 90, e.g., in the vicinity of the patterning device MA. Further, electrons that have been ejected from the patterning surface 110 as a result of the photoelectric effect may contribute to the plasma within the patterning device environment 90. Electrons may be ejected from other surfaces on which EUV radiation is incident. Grounded surfaces on which EUV radiation is incident may continue to supply the plasma with electrons throughout the period that the time that the pulse of EUV radiation is generated. Free electrons within the plasma may be absorbed by the contaminant particles, resulting in those particles becoming negatively charged.

[0061] As a result of the patterning surface 110 becoming positively charged and the contaminant particles P becoming negatively charged, an attractive electrostatic force may be exerted between the patterning surface 110 and the contaminant particles. This may cause the contaminant particles to accelerate towards the patterning surface 110. Consequently, contaminant particles within the lithographic apparatus may be deposited onto the patterning surface 110. The contaminant particles deposited on the patterning surface 110 may absorb and / or scatter EUV radiation incident on the patterning region of the patterning surface 110. Consequently, the contaminant particles may lead to the presence of imperfections in the pattern projected onto the substrate W, which may cause to defectivity on the substrate W.

[0062] To reduce the extent to which contaminant particles accelerate towards the patterning surface 110 as a result of electrostatic attraction, a voltage biasing system may be used, in which a bias voltageis applied to the patterning surface 110 of the patterning device. This bias voltage may be negative. When a negative bias voltage is applied to the patterning surface 110, an electric field may be established between the patterning surface 110 and surrounding grounded components of the lithographic apparatus, e.g. the masking blades 120. As a result of this electric field, negatively charged contaminant particles in the patterning device environment 90 may be repelled from the patterning surface 110. Details of voltage biasing systems are described in WO2024056552A1 and PCT / EP2024 / 056459, the entirety of which are incorporated by reference herein.

[0063] In the present application, the terms “voltage” and “bias voltage” may also be referred to as a “potential” or a “bias potential”. Unless otherwise stated, voltages may be relative to the ground. Voltages may be relative to a local ground, such as a grounded frame of the lithographic apparatus, grounded masking blades 120, or other grounded components of the lithographic apparatus.

[0064] In one example, a masking blade 120 can be grounded, and an electric field established between a negatively biased patterning surface 110 and the grounded masking blade 120 can accelerate negatively charged contaminant particles away from the patterning surface 110.

[0065] The magnitude of the bias voltage applied to the patterning surface 40 may be greater than 1 V. This is because a voltage of this magnitude may be necessary to ensure that the distance between the patterning surface 110 and negatively charged contaminant particles increases over time (i.e. that the contaminant particles accelerate away from the patterning surface 110). The magnitude of the bias voltage applied to the patterning surface 110 may also be less than 30 V, and preferably less than 10 V. Voltages in excess of these values may result in an excessively large current being drawn through the patterning surface 110. This can cause the patterning surface 110 to heat up and deform, which can reduce the quality of the pattern projected from the patterning surface 110 to the substrate W.

[0066] A bias voltage may be applied to the patterning surface 110 in various ways. For instance, as described in WO2024056552A1, a bias voltage may be applied to the patterning surface 110 via a conductive member which is connected to a voltage source. The conductive member may apply the bias voltage to the patterning surface 110 by contacting the patterning surface 110, e.g. by contacting a peripheral portion of the patterning surface 110. As is also described in WO2024056552A1, a bias voltage may be applied to the patterning device MA via one or more of the burls 106 on the support structure 100. As described in PCT / EP2024 / 056459, a bias voltage may be capacitively induced in the patterning surface 110, e.g. by controlling an average voltage of the electrodes 104A, 104B in the support structure 100.

[0067] The application of a bias voltage to the patterning device via the burls will now be described with reference to Figures 5A to 7C.

[0068] Figure 5A schematically depicts a section view of an arrangement comprising a support structure 100 and a patterning device MA. Figure 5B schematically depicts a bottom view of the arrangement depicted in Figure 5 A. Figure 5C schematically depicts a non-patterning surface 111 of the patterning device MA of the arrangement depicted in Figures 5 A and 5B. The patterning deviceMA and the support structure 100 in the arrangement depicted in Figures 5A to 5C may be similar to, or the same as, the patterning device MA and the support structure 100 described in relation to Figure 3, except as discussed below.

[0069] The arrangement depicted in Figures 5A to 5C is configured to apply a bias voltage to the non-patterning surface 111 of the patterning device MA. The bias voltage applied to the non-patterning surface is applied from a voltage source 250a, 250b via one or more burls 106 on the support structure 100. The bias voltage is applied to the one or more burls 106 from the voltage source 250a, 250b by a conductive portion 240a, 240b on the support structure 100.

[0070] In the arrangement depicted in Figures 5A to 5C, it may be possible to apply different bias voltages to different parts of the non-patterning surface 111. As best shown in Figure 5C, the conductive coating 113 which forms the non-patterning surface 111 of the patterning device MA is partitioned into two segments such that the non-patterning surface 111 comprises a first conductive portion 113a and a second conductive portion 113b. The first conductive portion 113a and the second conductive portion 113b are substantially electrically isolated from one another. The first conductive portion 113a and the second conductive portion 113b may be formed by removing a strip of material from the conductive coating 113 which forms the non-patterning surface 111 to form a discontinuity 213 in the conductive coating 113 which forms the non-patterning surface 111. The discontinuity 213 may electrically isolate the first conductive portion 113a of the non-patterning surface 111 from the second conductive portion 113b of the non-patterning surface 111.

[0071] The support structure 100 depicted in Figures 5A and 5B comprises two conductive portions: a first conductive portion 240a and a second conductive portion 240b. The first conductive portion 240a of the support structure 100 and the second conductive portion 240b of the support structure 100 may be formed on the support surface 102 of the support structure 100. The first conductive portion 240a of the support structure 100 and the second conductive portion 240b of the support structure 100 may be electrically isolated from one another. The first conductive portion 240a of the support structure 100 and the second conductive portion 240b of the support structure 100 may be formed on a peripheral region of the support surface 102 (i.e. a region radially outward of the clamping surface, from which the plurality of burls 106 protrude). The first conductive portion 240a of the support structure 100 and the second conductive portion 240b of the support structure 100 may be provided on opposite sides of the support surface 102. The first conductive portion 240a of the support structure 100 and the second conductive portion 240b of the support structure 100 may be referred to as clamp ears.

[0072] The first conductive portion 240a of the support structure 100 may be electrically connected to a first voltage source 250a. The second conductive portion 240b of the support structure 100 may be electrically connected to a second voltage source 240b.

[0073] The support structure 100 may comprise one or more conductive burls 207a, 207b. The one or more conductive burls 207a, 207b may be burls to which a conductive coating has been provided. The conductive coating may be formed of any suitable conductive material, e.g. TiN. The supportstructure 100 depicted in Figure 5 A comprises first conductive burls 207a and second conductive burls 207b. The first conductive burls 207a may be electrically connected to the first conductive portion 240a of the support structure 100. The second conductive burls 207b may be electrically connected to the second conductive portion 240b of the support structure 100. The first conductive burls 207a may be electrically isolated from the second conductive burls 207b.

[0074] The first conductive burls 207a may be electrically connected to the first conductive portion 113a of the non-patterning surface 111. That is, distal ends of the first conductive burls 207a may contact the first conductive portion 113a of the non-patterning surface 111. Consequently, an electrical connection between the first voltage source 250a and the first conductive portion 113a of the nonpatterning surface 111 may be as follows: (i) first voltage source 250a; (ii) first conductive portion 240a of the support structure; (iii) first conductive burls 207a; and (iv) first conductive portion 113a of the non-patterning surface 111. In this way, a bias voltage can be applied from the first voltage source 250a to the fist conductive portion 113a of the non-patterning surface 111.

[0075] The second conductive burls 207b may be electrically connected to the second conductive portion 113b of the non-patterning surface 111. That is, distal ends of the second conductive burls 207b may contact the second conductive portion 113b of the non-patterning surface 111. Consequently, an electrical connection between the second voltage source 250b and the second conductive portion 113b of the non-patterning surface 111 may be as follows: (i) second voltage source 250b; (ii) second conductive portion 240b of the support structure; (iii) second conductive burls 207b; and (iv) second conductive portion 113b of the non-patterning surface 111. In this way, a bias voltage can be applied from the second voltage source 250b to the fist conductive portion 113b of the non-patterning surface 111.

[0076] The bias voltage that is applied to the first conductive portion 113a of the non-patterning surface 111 may be different to the bias voltage which is applied to the second conductive portion 11 b of the non-patterning surface 111.

[0077] In the arrangement depicted in Figures 5A-5C, the patterning surface 110 is substantially electrically isolated from the non-patterning surface 111. Thus, it is not possible to apply a bias voltage to the patterning surface 110 via the non-patterning surface 111.

[0078] Figure 6 depicts a plan view of a support structure 100. The surface of the support structure 100 which is visible is the support surface 102. The support structure 100 may be the support structure 100 of the arrangement depicted in Figures 5A to 5C.

[0079] As depicted in Figure 6, the support structure 100 is rectangular, but the present invention is not limited thereto. As described above, a first conductive portion 240a and a second conductive portion 240b are formed on the support surface 102 of the support structure. The support structure MT further comprises conductive tracks formed on the support surface 102. A conductive track electrically connects the first conductive portion 240a to the first conductive burls 207a. A conductive track electrically connects the second conductive portion 240b to the second conductive burls 207b. Theconductive tracks may be formed outward of the burls 106. Some or most of the burls 207 on the clamping surface 102 may remain electrically isolated from one or both of the conducting portions 240a, 240b.

[0080] The first conductive portion 240a and the second conductive portion 240b of the support structure may be formed of any suitable conductive material. For example, the first conductive portion 240a and the second conductive portion 240b of the support structure may formed of titanium nitride (TiN). The conductive tracks may be formed of the same material as the first conductive portion 240a and the second conductive portion 240b of the support structure 100. To form the first conductive portion 240a of the support structure 100, the second conductive portion 240b of the support structure 100, and the conductive tracks, conductive material may be deposited onto the support surface 102 using any suitable technique. After deposition of the conductive material, the conductive material may be patterned to form the shape of the first conductive portion 240a of the support structure 100, the second conductive portion 240b of the support structure 100, and the conductive tracks. The same technique may be used to apply the conductive coating to the conductive burls 207a, 207b. The distal ends of the burls 207 that are isolated from the conducting portions can be provided with a similar coating to that of the conductive burls. This may be such that a coefficient of friction between the burls 207 and the non-patterning surface 111 of the patterning device is similar or substantially the same for the conductive burls and the non-conductive burls. This leads to constant and / or uniform wear profiles.

[0081] Two voltage sources 250a, 250b, two conductive portions 240a, 240b of the support structure 100, two sets of conductive burls 207a, 207b and two conductive portions 113a, 113b may not be present in all embodiments. To apply one bias voltage to the whole of the non-patterning surface 111, a single voltage source, a single conductive portion of the support structure 100 and a single set of conductive burls may be provided, and the conductive coating 113 which forms the non-patterning surface 11 may not comprise a discontinuity (i.e. may be continuous). In this case, a bias voltage may be applied to the non-patterning surface from a voltage source as follows: (i) the voltage source; (ii) the conductive portion of the support structure 100; (iii) the conductive burls; and (iv) the conductive coating 113 which forms the non-patterning surface. Alternatively, the discontinuity in the 111 may be present, and both the conductive portions 240a, 240b may be electrically connected to a common voltage source (or two different voltage sources set to the same voltage).

[0082] Figures 7 A to 7C depict an arrangement comprising a support structure 100 and a patterning device MA. Figure 7A schematically depicts a side view of the arrangement. Figure 7B schematically depicts a bottom view of the arrangement depicted in Figure 7A. Figure 7C schematically depicts a non-patterning surface of the patterning device of the arrangement depicted in Figures 7A and 7B.

[0083] The arrangement depicted in Figures 7A to 7C may be substantially the same as the arrangement depicted in Figures 5A to 5C, except for the fact that the non-patterning surface 111 is electrically connected to the patterning surface 110. The non-patterning surface 111 is electrically connected to the patterning surface 110 via an edge surface of the patternign device MA other than thenon-patterning surface and the patterning surface. Specifically, in the arrangement depicted in Figures 7A to 7C, the first portion 113a of the non-patterning surface 111 is electrically connected to the patterning surface 110. The first portion 113a of the non-patterning surface 111 may be electrically connected to the patterning surface 110 by a conductive edge 260. The conductive edge 260 may be a conductive coating applied to a side surface of the patterning device MA (i.e. a surface of the patterning device MA which is substantially perpendicular to the patterning surface 110 and the non-patterning surface 111 and which extends between the patterning surface 110 and the non-patterning surface 111).

[0084] In the arrangement depicted in Figures 7A to 7C, a bias voltage can be applied to the patterning surface 110 via an electrical connection comprising: (i) the first voltage source 250a; (ii) the first conductive portion 240a of the support structure; (iii) the first conductive burls 207a; (iv) the first conductive portion 113a of the non-patterning surface 111; (v) the conductive edge 260; and (vi) the patterning surface 110. Separately, a bias voltage can be applied to the second conductive portion 113b of the non-patterning surface 111 as described in relation to Figures 5A to 5C. The second conductive portion 113b of the non-patterning surface 111 may be larger than the first conductive portion 113a of the non-patterning surface 111. That is, the second conductive portion 113b of the non-patterning surface may make up the majority of the non-patterning surface 111. Thus, with the arrangement depicted in Figures 7A to 7C, one bias voltage can be applied to the patterning surface 110 and another (different) bias voltage can be applied to the majority of the non-patterning surface 111.

[0085] Two voltage sources 250a, 250b, two conductive portions 240a, 240b of the support structure 100, two sets of conductive burls 207a, 207b and two conductive portions 113a, 113b may not be provided in all embodiments. To apply the same bias voltage to the whole of the non-patterning surface 111 and the whole of the patterning surface 110, a single voltage source, a single conductive portion of the support structure 100 and a single set of conductive burls may be provided, and the conductive coating 113 which forms the non-patterning surface 11 may not comprise a discontinuity 213 (i.e. may be continuous). In this case, a bias voltage may be applied from one voltage source to the patterning surface 110 and the non-patterning surface 111 via an electrical connection comprising: (i) a voltage source; (ii) a conductive portion of the support structure; (iii) a conductive burls; (iv) the non-patterning surface 111 ; (v) a conductive edge 260; and (vi) the patterning surface 110.

[0086] WO2024056552A1 provides further detail on electrical connections between the support structure 100, the non-patterning surface 111 and the patterning surface 110, including on the incorporation of current-limiting components (e.g. resistors and inductors) into the conductive coating 113 which forms the non-patterning surface 111. The disclosure of WO2024056552A1 in regard to electrical connections between the support structure 100, the non-patterning surface 111 and the patterning surface 110 is incorporated by reference herein.

[0087] During loading of the patterning device MA onto the support structure 100 and during unloading of the patterning device MA from the support structure 100, there may be a risk ofelectrostatic discharge between various surfaces. This risk of electrostatic discharge, and techniques for reducing the risk of electrostatic discharge, are discussed below.

[0088] Capacitances exist between several of the components in the lithographic apparatus. In particular the capacitance between the support surface 102 and the non-patterning surface 111 of the patterning device MA may be considered to be a variable capacitance, which varies as a function of a gap between the clamping surface 102 and the non-patterning surface 111.

[0089] Charge can accumulate at isolated surfaces of the patterning device MA, e.g., the patterning surface 110 and the non-patterning surface 111 (in the case that the patterning surface 110 and the nonpatterning surface 111 are electrically isolated). Residual charge can remain on a clamped patterning device MA once it has been released from the support structure 100. As the unclamped patterning device MA is moved away from the support surface 102, the increasing separation between the support surface 102 and the non-patterning surface 111 can lead to a decrease in capacitance, and an amplification of the potential. That is, given the proportional relationship between charge and potential (i.e. Q = C*V) in a closed system, when the capacitance changes (in inverse proportion to the separation between parallel plates), any reduction in capacitance will result in a proportional increase in potential. Thus, as the patterning device MA and support structure 100 are separated, it is possible that the potential of the patterning device (i.e. of the patterning surface 110 and / or the non-patterning surface 111) will rise sufficiently to cause electrical breakdown of the hydrogen gas to occur. Such discharge can result in damage to the patterning device MA, the support structure 100 and / or particle generation, which can lead to subsequent defects. Consequently, it is preferable that the residual charge on the patterning device MA is small or non-existent before the patterning device is unclamped from the support structure 100.

[0090] In view of the above, it has been proposed to discharge the patterning device MA (i.e. the patterning surface 110 and / or the non-patterning surface 111) during loading of the patterning device MA onto the support structure 100 and during unloading of the patterning device MA from the support structure 100. Discharging of the patterning device MA may be achieved by electrically connecting the patterning device MA to the ground. In this context, “ground” refers to an electric charge sink which is able to absorb a very large amount of electric charge relative to the amount of charge that may be built up on the patterning device MA during operation of the lithographic apparatus. The patterning device MA may be electrically connected to the ground in the same way that the patterning device MA is electrically connected to a voltage source. For example, the patterning device MA be electrically connected to the ground via one or more conductive burls of the support structure 100 and / or by a conductive member which is configured to contact the patterning surface 110. Further detail on grounding of the patterning device is provided in WO2024056552A1 and PCT / EP2024 / 056459 , the entirety of which are hereby incorporated by reference.

[0091] Additionally or alternatively, during loading of the patterning device, voltages may be applied to the first conductive burls 207a and / or the second conductive burls 207b to reduce the likelihood ofelectrostatic discharge between the first conductive burls 207a and the non-patterning surface and / or between the second conductive burls 207b and the non-patterning surface. As the patterning device MA approaches the support structure MT during loading, a potential of the non-patterning surface may not be 0 V relative to the ground. This may be because, for example, charge has accumulated on the non-patterning surface, or because a non-zero average potential of the electrodes 104A, 104B has resulted in a non-zero potential being capacitively induced in the non-patterning surface. Thus, to reduce the risk of electrostatic discharge (i.e. sparks), voltages may be applied to the first conductive burls 207a and / or the second conductive burls 207b which are substantially similar to the voltages of the non-patterning surface. Further detail on this is provided in PCT / EP2024 / 056459, the entirety of which is hereby incorporated by reference.

[0092] Additionally or alternatively, before unloading the patterning device MA from the support structure MT, a bias voltage may be applied to the non-patterning surface 111 of the patterning device MA via the first conductive burls 207a and / or the second conductive burls 207b to reduce a charge on the non-patterning surface. This may reduce the risk of electrostatic discharge (i.e. sparks) as the patterning device is unloaded from the support structure. Further detail on this is provided in PCT / EP2024 / 056459, the entirety of which is hereby incorporated by reference.

[0093] Figures 8A to 8C depict an arrangement comprising a support structure 100, a patterning device MA and a protective membrane 131 disposed in front of the patterning surface 110. Figure 8 A schematically depicts a section view of the arrangement. Figure 8B schematically depicts a bottom view of the arrangement. Figure 8C schematically depicts a non-patterning surface 111 of the patterning device MA of the arrangement. The arrangement depicted in Figures 8A to 8C may be substantially the same as the arrangement depicted in Figures 7A to 7C, except for the provision of the protective membrane 131 and associated support structures. The protective membrane 131 may be similar to the protective membrane 131 described in relation to Figure 4.

[0094] As explained above, the protective membrane 131 may be supported by a protective membrane frame 132. The protective membrane 131 may be stretched across the protective membrane frame 132. The protective membrane frame 132 may be coupled to (e.g. mounted on) the patterning surface 110 of the patterning device 110 via one or more mounting portions 133. The protective membrane 131 may be substantially electrically isolated (e.g. isolated from the patterning surface 110). This may be because the mounting portions 133 and / or the protective membrane frame 132 are formed of an insulating material.

[0095] During exposure of the patterning device MA with EUV radiation, hydrogen ions (H+) in the plasma formed in the patterning device environment 90 may be implanted into the protective membrane 131 or cause chemical sputtering of the material of the protective membrane 131. The implantation of hydrogen ions into the protective membrane 131 or chemical sputtering of the material of the protective membrane 131 may degrade the protective membrane 131 and may decrease the lifetime of the protective membrane. The implantation of hydrogen ions into the protective membrane 131 or thechemical sputtering of the material of the protective membrane 131 may be accelerated by the application of a negative bias voltage to the patterning surface 110. This is because the positively charged hydrogen ions are attracted to the patterning surface 110 when a negative bias voltage is applied thereto.

[0096] In some protective membranes 131 (e.g. protective membranes 131 formed of MoSiN), the implantation of hydrogen ions may cause a reduction in the tension of the protective membrane 131. A reduction in the tension of the protective membrane 131 may mean that external forces (e.g. electrostatic forces and / or gravity and / or pressure difference between the different sides of the protective membrane 131) are able to deflect the protective membrane 131 to the extent that the protective membrane 131 contacts neighboring surfaces (e.g. the patterning surface 110 or the masking blades 120). An electrostatic force may be exerted on the protective membrane 131 as a result of a potential difference between the protective membrane 131 and the neighboring surfaces (e.g. the patterning surface 110 or the masking blades 120).

[0097] For some types of protective membranes 131 (e.g. protective membranes 131 formed of carbon nanotubes), the lifetime of the protective membranes 131 may be reduced by the chemical sputtering of carbon of the protective membrane 131 by hydrogen ions and radicals. Such sputtering may worsen the structural integrity of the protective membrane. This may be to the extent that electrostatic forces exerted on the protective membrane 131 or pressure difference between the different sides of the protective membrane 131 can cause the protective membrane 131 to fail.

[0098] The implantation of hydrogen ions into the protective membrane 131 may be reduced by applying a positive bias voltage to the protective membrane 131 (e.g. a bias voltage which is positive relative to the ground, e.g. a bias voltage which is positive relative to the masking blades 120). This is because applying a positive bias voltage to the protective membrane 131 may mean that hydrogen ions are repelled from the protective membrane 131. By reducing the implantation of hydrogen ions into the protective membrane 131, degradation of the protective membrane can be reduced, and the lifetime of the protective membrane 131 can be extended. Similarly, chemical sputtering by hydrogen ions can be reduced by applying a positive bias to the protective membrane 131. Thus the lifetime of the protective membrane 131 can be extended.

[0099] The positive bias voltage applied to the protective membrane 131 may be greater than 1 V. By applying a positive bias voltage to the protective membrane 131 that is greater than 1 V, hydrogen ions can be effectively repelled from the protective membrane 131. The positive bias voltage applied to the protective membrane 131 may be less than 30 V, and preferably less than 10 V. Increasing the bias voltage applied to the protective membrane 131 may increase a current flowing through the protective membrane 131. If the current in the protective membrane 131 becomes too high, the protective membrane may heat up and deform. Thus, by providing a bias voltage that is less than 30 V and preferably less than 10 V, a likelihood that the protective membrane 131 heats up and deforms is reduced.

[0100] The protective membrane 131 is most likely to experience large electrostatic forces during loading of the patterning device MA (with the protective membrane 131 coupled thereto) onto the support structure 100, and during unloading of the patterning device MA (with the protective membrane coupled thereto) from the support structure 100. During loading and unloading, the electrostatic forces exerted on the protective membrane may arise as a result of charge accumulation on the protective membrane 131. Charge may be able to accumulate on the protective membrane 131 because the protective membrane 131 is floating. The charge accumulated on the protective membrane may bring the protective membrane to a large potential relative to the neighboring surfaces (e.g. the patterning surface 110 and the masking blades 120), resulting in a large electrostatic force being exerted on the protective membrane 131.

[0101] In addition to resulting in the exertion of a large electrostatic force on the protective membrane 131, the fact that there is a large potential difference between the protective membrane 131 and neighboring surfaces (e.g. the patterning surface 110 and the masking blades 120) means that there is a risk of electrostatic discharge (i.e. a spark) between the protective membrane 131 and the neighboring surfaces (e.g. the patterning surface 110 and the masking blades 120). Such electrostatic discharge may result in failure of the protective membrane 131. Thus, in general, the accumulation of charge on the protective membrane 131 may lead to failure of the protective membrane 131 during loading and / or unloading operations.

[0102] The likelihood of failure of the protective membrane 131 during loading and / or unloading operations may be reduced by discharging the protective membrane 131 before and / or during loading and / or unloading operations. The protective membrane 131 may be discharged by electrically connecting the protective membrane 131 to the ground.

[0103] One aspect of the present disclosure is directed to providing an electrical connection to the protective membrane 131. The electrical connection to the protective membrane 131 may be used to apply a bias voltage to the protective membrane 131. In this case, the electrical connection may electrically connect the protective membrane 131 to a voltage source. Additionally or alternatively, the electrical connection to the protective membrane 131 may be used to ground the protective membrane, such that the protective membrane can be discharged during loading and / or unloading operations. In this case, the electrical connection may electrically connect the protective membrane 131 to a grounded component, e.g. a voltage source set to 0 V or the grounded frame of the lithographic apparatus.

[0104] The electrical connection to the protective membrane 131 may comprise the support structure 100. Thus, the protective membrane 131 may be electrically connected to the support structure 100. The following description is mainly directed to the case that the protective membrane 131 is electrically connected to a voltage source such that a bias voltage can be applied to the protective membrane 131. However, it will be appreciated that the protective membrane may be electrically connected to the ground using the same techniques.

[0105] In the case that the protective membrane 131 is electrically connected to a voltage source, the protective membrane 131 may be electrically connected to the voltage source via the support structure 100. For example, the support structure 100 may be electrically connected to the protective membrane frame 132, and the protective membrane may be electrically connected to the voltage source via the protective membrane frame 132 and the support structure 100. For this purpose, at least a portion of the protective membrane frame 132 may be conductive, and the protective membrane 131 may be electrically connected to the support structure via the conductive portion of the protective membrane frame 132.

[0106] In some embodiments, the protective membrane 131 is electrically connected to a conductive portion on the support surface 102 of the support structure, e.g. the protective membrane 131 may be electrically connected to the first conductive portion 240a of the support structure 100 depicted in Figure 8A.

[0107] In some embodiments, the protective membrane 131 is electrically connected to the voltage source (e.g. the first voltage source 250a) via the patterning device MA. Figures 9A to 12B depict various configurations of a patterning device MA and a protective membrane 131 in which the protective membrane 131 is electrically connected to the patterning device MA. The patterning device MA may then be electrically connected to the support structure 100 as described above. That is, the configurations of a patterning device MA and a protective membrane 131 depicted in Figures 9 A to 12B could be implemented in the arrangement depicted in Figures 8A to 8C to result in an arrangement in which the protective membrane 131 is electrically connected to the first voltage source 250a.

[0108] In some embodiments in which the protective membrane 131 is electrically connected to the voltage source (e.g. the first voltage source 250a) via the patterning device MA, the protective membrane frame 132 may be electrically connected to a conductive edge 260 of the patterning device MA. This conductive edge 260 may, or may not, be electrically connected to the patterning surface. If the conductive edge 260 is electrically isolated from the patterning surface 110 and the protective membrane 131 is electrically connected to the conductive edge, the protective membrane 131 may be substantially electrically isolated from the patterning surface 110.

[0109] In some embodiments in which the protective membrane 131 is electrically connected to the voltage source via the patterning device MA, the protective membrane 131 may be electrically connected to the patterning surface 110 via the protective membrane frame 132 and / or the one or more mounting portions 133. The one or more mounting portions 133 may be conductive. The conductive portion of the protective membrane frame 132 may be electrically connected to the patterning surface 110 via the one or more mounting portions 133.

[0110] The patterning surface 110 may be electrically connected to the non-patterning surface via a conductive edge 260, as discussed above. Thus, by electrically connecting the protective membrane 131 to the patterning surface 110 via the protective membrane frame 132 and / or the one or more mounting portions 133, the protective membrane 131 is electrically connected to the non-patterningsurface 111. The non-patterning surface 111 may be electrically connected to the voltage source in the manner described in relation to the arrangements depicted in Figures 5A to 8C.

[0111] In summary, an electrical connection between the protective membrane 131 and a voltage source (e.g. the voltage source 250a) may comprise: (i) a voltage source (e.g. the voltage source 250a);(ii) a conductive portion of the support structure 100 (e.g. the first conductive portion 113a of the support structure 100); (iii) one or more conductive burls (e.g. the first conductive burl 207a); (iv) the non-patterning surface 111 of the patterning device MA (e.g. the first conductive portion 113a of the non-patterning surface 111); (v) the conductive edge 260; (vi) the patterning surface 110 of the patterning device MA; (vii) the one or more mounting portions 133; (viii) the protective membrane frame 132; and (ix) the protective membrane 131. It will be appreciated that some of components (ii) to (viii) may be omitted, as long as the protective membrane 131 remains electrically connected to the voltage source. For instance, in some embodiments, the one or more mounting portions 133 may not be provided, and the protective membrane frame 132 may be coupled to the patterning surface 110 directly. In such embodiments, the mounting portions 133 would not form part of the conductive path between the voltage source and the protective membrane 131.

[0112] In an arrangement configured to apply a bias voltage to a protective membrane 131, there may be a single voltage source. In cases where there is a single voltage source, the same bias voltage may be applied to the non-patterning surface 111, the patterning surface 110 and the protective membrane 131. To apply one bias voltage to the whole of the non-patterning surface 111, the whole of the patterning surface 110, and the protective membrane 131, a single voltage source, a single conductive portion of the support structure 100 and a single set of conductive burls may be provided, and the conductive coating 113 which forms the non-patterning surface 111 may not comprise a discontinuity 213 (i.e. may be continuous). Such an arrangement is more simple, and thus easier to manufacture.

[0113] In other arrangements configured to apply a bias voltage to a protective membrane 131, there may be two or more voltage sources 250a, 250b, as depicted in Figures 8A to 8C. In this case, the protective membrane 131 may be electrically connected to the first voltage source 250a. An electrical connection between the first voltage source 250a and the protective membrane 131 may comprise the following: (i) the voltage source 250a; (ii) the first conductive portion 113a of the support structure 100;(iii) the first conductive burls 207a; (iv) the first conductive portion 113a of the non-patterning surface 111 ; (v) the conductive edge 260; (vi) the patterning surface 110 of the patterning device MA; (vii) the one or more mounting portions 133; (viii) the protective membrane frame 132; and (ix) the protective membrane 131. Separately, the second conductive portion 113b of the non-patterning surface may be electrically connected to the second voltage source 250b, as described in relation to Figures 5A to 5C. As explained above, the area of the second conductive portion 113b of the non-patterning surface 111 is greater than an area of the first conductive portion 113a of the non-patterning surface 111. For example, the area of the second conductive portion 113b of the non-patterning surface 111 may be greater than twice the area of the first conductive portion 113a of the non-patterning surface 111. Thus,one bias voltage can be applied to the patterning surface 110 and the protective membrane 131, and another (different) bias voltage can be applied to the majority of the non-patterning surface 111.

[0114] As explained above, to provide the electrical connection between the protective membrane 131 and the patterning device MA, at least a portion of the protective membrane frame 132 is conductive. In some embodiments, the membrane frame 132 itself (i.e. a main body of the membrane frame 132) is conductive. In this case, substantially all of the membrane frame 132 may be conductive. For example, the membrane frame may be formed of a metal. The metal may comprise one or more of chromium, ruthenium and molybdenum.

[0115] In other embodiments, the membrane frame 132 may comprise a conductive coating 234 which is provided on at least a portion of the membrane frame (i.e. provided on a main body of the membrane frame) to form the conductive portion of the membrane frame 132. The conductive coating 234 of the membrane frame 132 may be a metal coating, i.e. a metallization. The metal coating may comprise one or more of chromium, ruthenium and molybdenum. The conductive coating 234 of the membrane frame 132 may alternatively comprise a conductive ceramic. The conductive ceramic may be, for example, chromium nitride or tantalum nitride. In such embodiments, only the portions of the membrane frame 132 to which the conductive coating is provided may be conductive.

[0116] In embodiments where the conductive coating 234 is provided on at least a portion of the membrane frame to form the conductive portion of the membrane frame 132, the membrane frame 1 2 itself (i.e. a main body of the membrane frame 132) may be formed of an insulating material or of a semiconductor material. For example, the membrane frame 132 may be formed from a material comprising silicon. In such embodiments, the conductive coating 234 of the membrane frame 132 may be deposited onto the material comprising silicon.

[0117] A portion of the conductive coating 234 of the membrane frame 132 which contacts the protective membrane 131 may be referred to as a contact portion. Figures 9 A and 9B depict an embodiment in which the conductive coating 234 of the membrane frame 132 extends (e.g. wraps) around the protective membrane 131 such that the protective membrane 131 is interposed between the contact portion and the protective membrane frame 132. In other words, a portion of the conductive coating 234 of the membrane frame coats the protective membrane 131.

[0118] Figures 10A and 10B an embodiment in which the contact portion is interposed between the membrane frame 132 and the protective membrane 131. As shown in Figure 10A, a portion of the protective membrane 131 may be bent out of the plane of the protective membrane 131 (away from the protective membrane frame 132) in the region of the contact portion so that the conductive coating 234 can be accommodated between the protective membrane 131 and the protective membrane frame 132.

[0119] In the embodiments depicted in Figures 9 A to 10B, the conductive coating 234 of the membrane frame 132 does not extend all around the membrane frame 132 in the azimuthal direction. Rather, the conductive coating 234 of the membrane frame is provided to only a portion of one side ofthe protective membrane frame 132. Thus, the contact portion only extends along a portion of one side of the protective membrane 131. Such configurations may be relatively easy to manufacture.

[0120] Figure 11A to 12B depict embodiments in which the contact portion extends around substantially all of the perimeter of the protective membrane 131. This is because the conductive coating 234 extends around substantially all of the perimeter of the protective membrane frame 132 (i.e. extends all around the protective membrane frame in the azimuthal direction). This increases the size of the contact area, which reduces the current density in the protective membrane 131. Further, by providing the contact area all around the perimeter of the protective membrane 231, current density over the protective membrane is made to be more uniform. Consequently, the risk of the protective membrane heating up and deforming as a result of current passing therethrough is decreased.

[0121] Figures 11A and 11B depict an embodiment which is similar to the embodiment depicted in Figures 9 A and 9B in that the conductive coating 234 of the membrane frame 132 extends around the protective membrane 131 such that the protective membrane 131 is interposed between the contact portion and the protective membrane frame 132. In other words, a portion of the conductive coating 234 of the membrane frame coats the protective membrane 131.

[0122] Figures 12A and 12B depict an embodiment which is similar to the embodiment depicted in Figures 10A and 10B in that the contact portion is interposed between the membrane frame 132 and the protective membrane 131. However, in the embodiment depicted in Figures 12A and 12B, the contact portion extends around substantially all of the perimeter of the protective membrane. This means that the protective membrane may remain substantially planar. That is, the protective membrane 131 does not need to bend out of the plane of the protective membrane 131 (away from the protective membrane frame 132) in the region of the contact portion so that the conductive coating 234 can be accommodated between the protective membrane 131 and the protective membrane frame 132.

[0123] Figure 13 schematically depicts conductive burls 207 (e.g. first conductive burls 207a) in contact with a non-patterning surface 111 of a patterning device MA. As shown in Figure 13, the burls 207 comprise a main body, which may be integral to the support structure 100, and a conductive coating 208.

[0124] At the distal ends of the burls 207, the surface of the conductive coating 208 which contacts the non-patterning surface 111 of the patterning device comprises asperities. The conductive coating 113 which forms the non-patterning surface 111 may be relatively hard, and so may not deform when the distal ends of the burls 207 contact the non-patterning surface 111. Thus, the area over which the conductive coating 208 of the conductive burls 207 is in contact with the non-patterning surface 111 of the patterning device MA may be less than the area of the distal ends of the conductive burls 207. Current may flow through the peaks of the asperities (which are in contact with the non-patterning surface 111), but not through the troughs (which are not in contact with the non-patterning surface). Thus, current density through the peaks of the asperities may be relatively high (e.g. compared to thecase where substantially all of the area of the distal ends of the burls is in contact with the non-patterning surface 111 of the patterning device).

[0125] In the case that a positive bias voltage is applied to the protective membrane 131 via the conductive burls 207, a current through the conductive burls may be relatively high (e.g. compared to the case that a negative bias voltage is applied to the patterning surface 110). Thus, where a positive bias voltage is applied to the protective membrane 131 via the conductive burls, the current density through the peaks of the asperities may become unacceptably high.

[0126] To reduce the concentration of current at the peaks of asperities on the coating 208 of conductive burls 207, a layer of conductive material 270 may be provided on a portion of the nonpatterning surface 111, such that the layer of conductive material 270 is disposed between the one or more conductive burls 207 and the non-patterning surface 111. Figure 14 schematically depicts such an arrangement. The layer of conductive material 270 may comprise (or consist essentially of) a material that is softer than the material of the conductive coating 113 which forms the non-patterning surface 111. In some embodiments, the layer of conductive material 270 comprises carbon. For example, the layer of conductive material 270 may comprise graphite, may substantially comprise graphite, or may consist essentially of graphite.

[0127] By providing a soft layer of conductive material 270 on the non-patterning surface 111 where the conductive burls 207 contact the non-patterning surface 111, current density through the peaks of asperities in the conductive coating 208 of the conductive burls can be reduced. This is because the distal ends of the burls 207 sink into the layer of conductive material 270, which means that substantially all of the conductive coating 208 at the distal ends of the burls 207 is in contact with the layer of conductive material. Consequently, current is not concentrated at the peaks of the asperities.

[0128] It may be preferable for a thickness of the layer of conductive material 270 to be small. This is so that the presence of the layer of conductive material 270 does not have a significant effect on the flatness of the patterning surface 110 of the patterning device MA and / or the direction in which the patterning surface 110 faces. If the presence of the layer of conductive material 270 worsens the flatness of the patterning surface 110 or changes the direction in which the patterning surface 110 faces, the presence of the layer of conductive material 270 may lead to imaging errors, e.g. focusing errors.

[0129] The layer of conductive material may be deposited onto the non-patterning surface 111 by a method comprising electron-beam induced deposition, chemical vapor deposition (CVD), and / or physical vapor deposition (PVD). It may be possible to remove and / or repair the layer of conductive material 270 on the non-patterning surface 111. If conductive material is transferred from the layer of conductive material 270 onto the support structure 100 (e.g. onto the burls 207), it may be possible to etch the conductive material off the support structure 100.

[0130] In some embodiments, the protective membrane 131 may be electrically connected to a voltage source via the membrane frame 132, a connecting element 280 and the support structure 100.In such embodiments, a bias voltage may be applied to the protective membrane 131 via the connecting element 280.

[0131] Figures 15 A, 15B and 16 depict an arrangement in which a voltage source (the second voltage source 250b) is electrically connected to the protective membrane via the connecting element 280. The arrangements depicted in Figures 15A and 15B may be similar to the arrangements depicted Figures 8A to 8C, except as described below.

[0132] As shown in Figures 15A and 15B, the support structure 100 comprises a conductive portion (e.g. second conductive portion 240b) on the support surface 102 thereof. The connecting element 280 may be configured to electrically connect the conductive portion (e.g. the second conductive portion 240b) on the support surface 102 to a conductive portion of the protective membrane frame 132. As explained above, the conductive portion of the membrane frame 132 may be the protective membrane frame 132 itself (if the protective membrane frame 132 is formed of a conductive material) or a conductive coating applied to the protective membrane frame 132. In this case, the patterning device MA may not form part of the conductive path between the voltage source which is used for the application of the bias voltage and the protective membrane 131.

[0133] The connecting element 280 may comprise a compliant portion 281. The compliant portion 281 may be configured to deform upon the application of an external force thereto. Specifically, the compliant portion 281 may be configured to undergo elastic deformation as the patterning device MA is brought into contact with the support structure 100. In the embodiments depicted in Figures 15A, 15B and 16, the compliant portion 281 is a spring. However, the compliant portion 281 is not limited thereto.

[0134] The connecting element may further comprise an upper pad 283 and a lower pad 282. In this context, “upper” and “lower” are used merely as labels, and do not carry meaning regarding the relative positions of the upper pad and lower pad in the gravitational direction. The upper pad 283 and the lower pad 282 may each be electrically connected to the compliant portion 281. The upper pad 283 and the lower pad 282 may be disposed at opposing ends of the compliant portion 281. The lower pad 282 may be configured to (and arranged within the arrangement to) contact the membrane frame 132. The upper pad 283 may be configured to (and arranged within the arrangement to) contact a conductive portion (e.g. the second conductive portion 240b) of the support structure 100.

[0135] The upper pad 283 may be coupled to the conductive portion (e.g. the second conductive portion 240b) of the support structure 100 or the lower pad 282 may be coupled to the membrane frame 132.

[0136] In the embodiment depicted in Figures 15A and 15B, the lower pad 282 is coupled to the membrane frame 132. Figure 15A depicts the arrangement at a time at which the patterning device is not supported by the support structure 100 (e.g. before loading of the patterning device MA onto the support structure 100). During loading of the patterning device MA onto the support structure 100, the patterning device MA may be moved towards the support structure 100. As the patterning device MAis moved towards the support structure 100, the upper pad 283 may come into contact with a conductive portion (e.g. the second conductive portion 250b) of the support structure 100 to establish an electrical connection between the conductive portion (e.g. the second conductive portion 250b) of the support structure 100 and the protective membrane frame 132 (see Figure 15B). After the upper pad 283 has come into contact with the conductive portion (e.g. the second conductive portion 250b) of the support structure 100, the patterning device MA may continue to move towards the support structure 100, causing the compliant portion 281 of the connecting member 280 to be compressed. The compression of the compliant portion 281 may comprise elastic deformation. The compression of the compliant portion 281 may mean that a force is exerted on the conductive portion (e.g. the second conductive portion 250b) of the support structure 100 by the connecting member 280, and thus the electrical connection between the connecting member 280 and the conductive portion (e.g. the second conductive portion 250b) of the support structure 100 is reliable. The compression of the compliant portion 281 also reduces the likelihood of damage when the connecting member 280 comes into contact with the support structure.

[0137] As will be appreciated, in other embodiments, the upper pad 283 may be coupled to the conductive portion (e.g. the second conductive portion 250b) of the support structure 100, and the lower pad 282 may come into contact with the protective membrane frame 132 during loading of the patterning device MA onto the support structure 100.

[0138] As shown in Figures 15 A to 16, the protective membrane frame 132 may extend beyond the perimeter of the patterning device MA in a horizontal plane such that the connecting member 280 is able to electrically connect a conductive portion (e.g. the second conductive portion 250b) of the support structure 100 to the protective membrane frame 132.

[0139] In some embodiments, an actuator (not shown) is provided to move the connecting element 280 between a first position and a second position. In the first position, the connecting element 280 may be in contact with the membrane frame 132. In the second position, the connecting element 280 may be separated from the membrane frame 232 (i.e. not in contact with the membrane frame 132). The actuator may be configured to rotate the connecting element 280 between the first position and the second position. In embodiments where an actuator is configured to move the connecting element between the first position and the second position, the connecting element may or may not comprise a compliant portion. More details on a connecting element that is movable between a first position and a second position to selectively apply a bias voltage are described in WO2024056552A1.

[0140] The upper pad 283 may be configured to contact conductive portion (e.g. the second conductive portion 250b) of the support structure 100 which is arranged outside of the clamping surface (i.e. radially outward of the area from which the burls 206 protrude). Consequently, the provision of the connecting element 280 may not affect the flatness of the patterning device (or the patterning surface 111 thereof).

[0141] In some embodiments in which the membrane frame 132 is electrically connected to the support structure 100 via a connecting element 280, the protective membrane 131 may be electrically isolated from the patterning surface 110. For example, the membrane frame 131 may be coupled to the patterning surface 110 via one or more mounting portions 133, and the one or more mounting portions 133 may electrically isolate the protective membrane 131 from the patterning surface 110. To electrically isolate the protective membrane 131 from the patterning surface 110, the one or more mounting portions may be formed form an electrically insulating material.

[0142] In the arrangement depicted in Figures 15 A and 15B, the non-patterning surface 111 is electrically isolated from the patterning surface 110. Where the patterning surface 110 is electrically isolated from the non-patterning surface 111, and electrically isolated from the protective membrane 131, the patterning surface 110 may be electrically floating.

[0143] In the arrangement depicted in Figures 15 A and 15B, the support surface 102 comprises a first conductive portion 240a electrically connected to a first voltage source 250a and a second conductive portion 240b electrically connected to a second voltage source 250b. The first and second conductive portions 240a, 240b and the first and second voltage sources 250a, 250b may be as described above. In the arrangement depicted in Figures 15A and 15B, the protective membrane 131 is electrically connected to the second voltage source 250b via the connecting element 280 and the second conductive portion 240b of the support surface. The non-patterning surface 111 is electrically connected to the first voltage source 250a via the first conductive portion 240a of the support structure 100. Specifically, the non-patterning surface 111 is electrically connected to the first voltage source 250a via conductive burls 207a and the first conductive portion 240a of the support structure 100. In this way, the nonpatterning surface 111 of the patterning device MA can be brought to one bias voltage, and the protective membrane 131 can be brought to another (different) voltage.

[0144] The conductive burls 207a may be the same as, or similar to, the conductive burls 207 described above. For example, the conductive burls 207 may comprise a conductive coating applied thereto. It is noted that, in the present context, the terms “first”, “second” and suchlike are merely labels used to distinguish different features of the arrangement.

[0145] In some embodiments, the patterning surface 110 is electrically connected to the nonpatterning surface 111. For example, the patterning surface 110 may be electrically connected to the non-patterning surface by a conductive edge 260, as has been described above. If, in the embodiment depicted in Figures 15A and 15B, the patterning surface 110 were to be connected to the non-patterning surface 111 (while the protective membrane 131 is electrically isolated from the patterning surface 110), the non-patterning surface 111 and the patterning surface 110 of the patterning device MA may be brought to one bias voltage (from the first voltage source 250a), and the protective membrane 131 may be brought to another (different) bias voltage (from the second voltage source 250b).

[0146] Figure 16 depicts another variant of the embodiment, different from the embodiments depicted in Figures 15 A and 15B. In the embodiment depicted in Figure 16, the protective membrane131 is electrically connected to the second voltage source 250b via the connecting element 280 and the second conductive portion 240b on the support structure 100. The patterning surface 110 is electrically isolated from the protective membrane 131. The non-patterning surface is partitioned into a first conductive portion 113a and a second conductive portion 113b. The patterning surface 110 is electrically connected to the first voltage source 250a via the conductive edge 260, the first conductive portion 113a of the non-patterning surface 111, first conductive burls 207a, and the first conductive portion 240a of the support structure 100. The second conductive portion 113b of the non-patterning surface 111 (which is electrically isolated from the patterning surface 110) is electrically connected to a third voltage source (not shown) via second conductive burls 207b and a third conductive portion on the support structure (not shown). As described above, the second conductive portion 113b of the nonpatterning surface 111 may be much larger than the first conductive portionl 33a of the non-patterning surface. Thus, with the embodiment depicted in Figure 16, one bias voltage can be applied to the majority of the non-patterning surface 111 (i.e. the second conductive portion 113b of the nonpatterning surface 111), another (different) bias voltage can be applied to the patterning surface 110, and another (different) bias voltage can be applied to the protective membrane 131.

[0147] In some of the variations described above, the patterning surface 110 can be brought to one bias voltage and the protective membrane 131 can be brought to another (different) bias voltage. That is, a potential difference between the patterning surface 110 and the protective membrane 131 can be established. The electric field arising from such a potential difference can be used to repel contaminant particles that are disposed between the protective membrane 131 and the patterning surface 110 away from the patterning surface 110. Contaminant particles that are between the protective membrane 131 and the patterning surface 110 may originate from the protective membrane 131. Alternatively, an opposite bias can repel positive ions from the protective membrane to the patterning surface 110 and reduce implantation or chemical sputtering.

[0148] In some embodiments in which the protective membrane 131 is electrically connected to a voltage source (e.g. the second voltage source 250b) via a connecting element 280, as described above, the patterning surface 110 may be electrically connected to the protective membrane 131 (e.g. through conductive mounting portions 133). In such embodiments, when a bias voltage is applied to the protective membrane 131, the same bias voltage is also applied to the patterning surface 110.

[0149] The bias voltage and / or grounding that should be applied to a patterning device MA and / or protective membrane 113 may depend on various factors. Thus, one aspect of the present disclosure relates to a method of applying a bias voltage to a patterning device which considers the various factors to apply a desirable bias voltage and / or grounding. The method of applying a bias voltage to a patterning device described below may be implemented using the hardware (i.e. the arrangements comprising a support structure 100, patterning device MA and protective membrane 131) described above. For example, the method of applying a bias voltage to a patterning device described below may comprise applying a bias voltage to the patterning device MA and / or the protective membrane 131 viathe support structure 100. Certain configurations of the hardware described above may be more appropriate for particular variants of the method of applying a bias voltage to the patterning device.

[0150] An exemplary method of applying a bias voltage to a patterning device is depicted in Figure 17. It will be recognized that certain steps and / or combinations of steps in the method depicted in Figure 17 may be isolated and implemented successfully without the other steps included in Figure 17.

[0151] The method may comprise a step S2 of determining a state of the lithographic apparatus. The step S2 of determining a state of the lithographic apparatus may comprise determining whether the lithographic apparatus is in a production state (i.e. a period in which the patterning device is being used for the manufacture of ICs, and / or is being exposed to EUV radiation), a “loading” state, or an “unloading” state. The exposure state, the loading state and the unloading state may alternatively be referred to as an exposure period, a loading period and an unloading period. In some examples, the lithographic apparatus may be in the production state when the lithographic apparatus is not in the loading state or the unloading state.

[0152] The lithographic apparatus may be in the loading state for the duration of a loading period. The loading period may be a period in which the patterning device is being loaded onto the support structure 100. The loading period may extend to a predetermined amount of time before the patterning device MA is loaded onto a support structure 100 and / or extend to a predetermined amount of time after the patterning device has been loaded onto the support structure. The predetermined amount of time may be greater than 1 s, optionally greater than 5 s, and optionally greater than 9 s. The predetermined amount of time may be less than 30 s, optionally less than 20 s, and optionally less than I l s. The loading period may include a time in which the voltage of the clamp electrodes 104A, 104B changes from low (below 100 V or even below 10 V) to high (above 100 V or even above 1 kV).

[0153] The lithographic apparatus may be in the unloading state for the duration of a unloading period. The unloading period may be a period in which the patterning device MA is being unloaded from the support structure. The unloading period may extend to a predetermined amount of time before the patterning device MA is unloaded from a support structure 100 and / or a predetermined amount of time after the patterning device MA has been unloaded from the support structure 100. The predetermined amount of time may be greater than 1 s, optionally greater than 5 s, and optionally greater than 9 s. The predetermined amount of time may be less than 30 s, optionally less than 20 s, and optionally less than Il s. The unloading period may include a time in which the voltage of the clamp electrodes 104A, 104B changes from high (above 100 V or even above 1 kV) to low (below 100 V or even below 10 V).

[0154] The determination in the step S2 of determining a state of the lithographic apparatus may be based on information received from the operating software of the lithographic apparatus and / or from data recorded by one or more sensors in the lithographic apparatus and / or from a user input.

[0155] When it is determined that the lithographic apparatus is in the production state, the method comprises a step S3 of determining whether a protective membrane 131 is disposed in front of thepatterning surface 110 of the patterning device MA (i.e. determining the presence or absence of the protective membrane 131).

[0156] The determination in the step S3 of determining whether the protective membrane 131 is disposed in front of a patterning surface 110 may be based on information received from the operating software of the lithographic apparatus and / or from data recorded by one or more sensors in the lithographic apparatus and / or from a user input. For example, the determination the step S3 of determining whether the protective membrane 131 is disposed in front of a patterning surface 110 may be based on data recorded by an optical sensor. The optical sensor may be used in the lithographic apparatus for functions other than determining whether the protective membrane 131 is disposed in front of the patterning surface 110. For example, the optical sensor may be used during alignment operations (e.g. operations in which the patterning device MA or support structure 100 are aligned with the substrate or a structure for supporting the substrate).

[0157] In a case that the protective membrane 131 is determined to be disposed in front of the patterning device MA, the method comprises a step S5 of applying a first bias voltage to the patterning surface 110. In a case that the protective membrane 131 is determined not to be disposed in front of the patterning device MA, the method comprises a step S4 of applying a second bias voltage to the patterning surface 110. The first voltage may be different to the second voltage. Thus, the bias voltage applied to the patterning surface 110 is dependent on whether or not a protective membrane 131 is disposed in front of the patterning device MA.

[0158] The second bias voltage may be negative. That is, when it is determined that a protective membrane 131 is not disposed in front of the patterning device, a negative bias voltage may be applied to the patterning surface. The application of a negative bias voltage to the patterning surface 110 repels negatively charged contaminant particles form the patterning surface 110, thus reducing defectivity of the patterning surface 110 (as described above). This is very advantageous when a protective membrane 131 is not disposed in front of the patterning surface 110.

[0159] A magnitude of the second bias voltage may be greater than 1 V. A magnitude of the second bias voltage may be less than 30V, and optionally less than 10 V. As explained above, by applying a negative bias voltage to the patterning surface 110 in this range, contaminant particles can be effectively repelled from the patterning’s surface 110 without excessively increasing the current within the patterning surface 110.

[0160] In some embodiments, the second bias voltage may be a bias voltage with a polarity which alternates in synchronization with pulses of EUV generated by the lithographic apparatus. When a pulse of EUV is present, the second bias voltage is positive to inhibit photoemission from the patterning surface 110. When the pulse of EUV is not present, the second bias voltage is negative to repel negatively charged contaminant particles. Further details regarding the application of a bias voltage with a polarity which alternates in synchronization with pulses of EUV are provided in PCT / EP2024 / 056459, the entirety of which is incorporated by reference herein.

[0161] The first bias voltage may be positive or negative. A magnitude of the first bias voltage may be less than 30 V and optionally less than 10 V. The magnitude of the first bias voltage may be greater than 1 V.

[0162] The step S5 of applying the first bias voltage to the patterning surface 110 may further comprise applying a third bias voltage to the protective membrane 131. That is, in the case that the protective membrane 131 is determined to be disposed in front of the patterning surface 110, the third bias voltage is applied to the protective membrane 131. The third bias voltage may be positive. As explained above, by applying a positive bias voltage to the protective membrane 131, hydrogen ions in the EUV plasma are repelled, and thus degradation of the protective membrane 131 is reduced.

[0163] A magnitude of the third bias voltage may be less than 30 V and optionally less than 10 V. As explained above, by applying a positive bias voltage to the protective membrane 131 in this range, hydrogen ions can be effectively repelled from the protective membrane 131 without excessively increasing the current within the protective membrane 131.

[0164] In some embodiments, the patterning surface 110 may remain electrically isolated from voltage sources, then only the third bias voltage is applied. In some embodiments, the patterning surface 110 may be electrically connected to the protective membrane, then the first bias voltage is same as the third bias voltage.

[0165] In a case that the lithographic apparatus is determined to be in a loading state or an unloading state, the method may comprise grounding the patterning surface 110 and / or the protective membrane 131. The grounding of the patterning surface 110 and / or the protective membrane 113 in the case that the lithographic apparatus is determined to be in the loading state or the unloading state may be instead of applying the first bias voltage and / or the second bias voltage and / or the third bias voltage.

[0166] The grounding of the patterning surface and / or the protective membrane 131 may comprise a step S6 of determining the presence or absence of a protective membrane 131. The step S6 of determining the presence or absence of a protective membrane may be substantially similar to the step S3 of determining the presence or absence of a protective membrane 131. In the case that the protective membrane 131 is determined to be present, the method may comprise a step S8 of grounding the patterning surface 110 and the protective membrane 131. In the case that the protective membrane 131 is determined to be absent (i.e. not present), the method comprises a step S7 of grounding the patterning surface.

[0167] As explained above, grounding the patterning device MA and / or the protective membrane 131 during loading and unloading operations reduces the risk of damage to the patterning device MA and / or the protective membrane, which may occur through several mechanisms.

[0168] In some embodiments, the step S7 may comprise applying a bias voltage to the patterning surface of the patterning device (i.e. instead of grounding). In some embodiments, the step S8 may comprise applying a bias voltage to the patterning surface of the patterning device and / or to the protective membrane (i.e. instead of grounding). This may be to reduce the accumulation of charge onthe patterning surface and / or on the protective membrane. Reducing the accumulation of charge on the patterning surface and / or on the protective membrane may reduce the risk of electrostatic discharge (i.e. sparks) during loading and unloading. The voltages applied to the patterning surface and / or on the protective membrane in steps S7 and S8 (i.e. during the loading and / or unloading periods) may differ from the first, second and third bias voltages). The voltages applied to the patterning surface and / or on the protective membrane in steps S7 and S8 may be less than 100 V and optionally less than 10 V. The magnitude and polarity of voltages applied to the patterning surface and / or on the protective membrane in steps S7 and S8 can be selected to compensate capacitive coupling of the non-patterning surface of the patterning device to the clamp electrodes, or to compensate for residual charge on the non-patterning surface of the patterning device. Thus, applying voltages to the patterning surface and / or on the protective membrane in steps S7 and S8 can prevent high current flowing through the conducive burls before, during or after the significant change in the voltages applied to the clamp electrodes 104A, 104B.

[0169] The method may further comprise grounding the non-patterning surface of the patterning device. In the case that the non-patterning surface comprises more than one conductive portion, a larger portion of the non-patterning surface may be grounded, or a bias voltage may be applied to the larger portion of the non-patterning surface. For instance, a larger portion of the non-patterning surface may be grounded via the support surface of the support structure while the patterning device is supported by the support structure. This may be during the loading period, the unloading period, and / or the production period.

[0170] The method may further comprise applying a bias voltage to the non-patterning surface of the patterning device. In the case that the non-patterning surface comprises more than one conductive portion, a bias voltage may be applied to the larger portion of the non-patterning surface. For instance, in a case that the lithographic apparatus is in the loading state or the unloading state, a fourth bias voltage may be applied to the non-patterning surface. A magnitude of the fourth bias voltage may be less than 100 V, and further optionally wherein the magnitude of the fourth bias voltage is less than 10 V.

[0171] It will be recognized that applying a bias during the loading and unloading periods to any of the surfaces of the patterning device or the protective membrane may comprise (a) applying a voltage to the conducting elements (e.g. conductive burls) positioned on the support structure that are in electrical contact with the patterning device or the protective membrane, while the patterning device is in mechanical contact with the support structure, or (b) applying similar voltages to the same conducting elements (e.g. the conductive burls) when the masking device is within 1 mm, or within 1 cm from the support structure. The option (b) allows to eliminate high currents through the conducting elements of the support structure, as is explained in further detail below.

[0172] During loading of the patterning device, the fourth bias voltage may be applied to the first conductive burls 207a and / or the second conductive burls 207b to reduce the likelihood of electrostaticdischarge between the first conductive burls 207a and the non-patterning surface and / or between the second conductive burls 207b and the non-patterning surface. As the patterning device MA approaches the support structure MT during loading, a potential of the non-patterning surface may not be 0 V relative to the ground. This may be because, for example, charge has accumulated on the non-patterning surface, or because a non-zero average potential of the electrodes 104A, 104B has resulted in a nonzero potential being capacitively induced in the non-patterning surface. Thus, to reduce the risk of electrostatic discharge (i.e. sparks), the fourth voltage may be substantially similar to the voltages of the non-patterning surface. Further detail on this is provided in PCT / EP2024 / 056459, the entirety of which is hereby incorporated by reference.

[0173] Additionally or alternatively, before unloading the patterning device MA from the support structure MT, the fourth bias voltage may be applied to the non-patterning surface 111 of the patterning device MA via the first conductive burls 207a and / or the second conductive burls 207b to reduce a charge on the non-patterning surface. This may reduce the risk of electrostatic discharge (i.e. sparks) as the patterning device is unloaded from the support structure.

[0174] In a case that the lithographic apparatus is in the production state, a fifth bias voltage may be applied to the non-patterning surface. A magnitude of the fifth bias voltage may be less than 30 V, and further optionally wherein the magnitude of the fourth bias voltage is less than 10 V.

[0175] In some embodiments, the third bias voltage is applied to the protective membrane 131 via a connecting element 180 and the support structure 100. In such embodiments, the method described herein may be performed using the hardware depicted in Figures 15A to 16.

[0176] In some embodiments, the third bias voltage may be applied to the protective membrane via the patterning device MA and the support structure 100. In such embodiments, the method described herein may be performed using the hardware depicted in Figures 9 A to 12B.

[0177] In some embodiments, the third bias voltage may different to the first bias voltage. That is, when a protective membrane 131 is determined to be disposed in front of the patterning device and the lithographic apparatus is in the exposure state, the bias voltage applied to the protective membrane 131 may be different to the bias voltage applied to the patterning surface 110. To implement the method in this way, hardware in which the patterning surface 110 is electrically isolated from the protective membrane 131 may be used. Examples of such hardware are described above. Where the third bias voltage is different to the first bias voltage, a difference between the third bias voltage and the first bias voltage (i.e. a potential difference between the patterning surface 110 and the protective membrane 131) may be less than 10 V.

[0178] In some embodiments, the third bias voltage may be substantially the same as the first bias voltage. This may be the case where the patterning surface 110 is electrically connected to the protective membrane 131, e.g. where the patterning surface 110 forms part of the conductive path between the protective membrane 131 and the voltage source which is configured to apply a bias voltage to the protective membrane.

[0179] Generally, current within components such as the patterning device, support structure and protective membrane should not exceed 1 mA. Current-limiting components (e.g. resistors and inductors) may be incorporated into the configurations described herein to ensure that the current does not exceed 1 mA during the operation of the lithographic apparatus.

[0180] A lithographic apparatus in accordance with the present invention may be used for the manufacture of ICs.

[0181] Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquidcrystal displays (LCDs), thin-film magnetic heads, etc.

[0182] 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 be implemented by 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.

[0183] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools.

[0184] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention, where the context allows, is not limited to optical lithography.

[0185] Aspects of the invention are described in the following numbered clauses.1. An arrangement for a lithographic apparatus, the arrangement comprising: a patterning device configured to impart a pattern to a beam of radiation, the patterning device comprising a patterning surface with a pattern thereon; a support structure configured to support the patterning device; anda protective membrane disposed in front of the patterning surface; wherein the protective membrane is electrically connected to the support structure.2. The arrangement of clause 1, wherein: the support structure comprises a support surface which faces a non-patterning surface of the patterning device; the support structure comprises a plurality of support protrusions extending from the support surface; the non-patterning surface of the patterning device is supported on distal ends of the plurality of support protrusions; and a portion of the support surface from which the support protrusions extend is a clamping surface.3. The arrangement of clause 1 or 2, further comprising a voltage source, wherein the protective membrane is electrically connected to the voltage source via the support structure.4. The arrangement of any of clauses 1 to 3, further comprising a membrane frame configured to hold the protective membrane, wherein the protective membrane is electrically connected to the voltage source via the membrane frame and the support structure.5. The arrangement of clause 4, wherein the membrane frame comprises a conductive portion, and wherein the conductive portion of the membrane frame is electrically connected to the protective membrane, and the conductive portion of the membrane frame is electrically connected the support structure.6. The arrangement of clause 4 or 5, wherein the protective membrane is electrically connected to the voltage source via the membrane frame, a connecting element and the support structure.7. The arrangement of clause 6, wherein: a conductive portion is provided on the support surface of the support structure, and the conductive portion is electrically connected to the voltage source; and the connecting element is configured to electrically connect the conductive portion on the support surface of the support structure to the conductive portion on the membrane frame, optionally wherein the conductive portion is provided radially outward of the clamping surface.8. The arrangement of clause 6 or 7, wherein the connecting element comprises a compliant portion, optionally wherein the compliant portion is configured to undergo elastic deformation as the patterning device is brought into contact with the support structure.9. The arrangement of clause 8, wherein the compliant portion comprises a spring.10. The arrangement of any of clauses 6 to 9, further comprising an actuator configured to move the connecting element between a first position and a second position, wherein in the first position, the connecting element is in contact with the membrane frame, and in the second position, the connecting element is separated from the membrane frame.11. The arrangement of any of clauses 4 to 10, wherein the membrane frame is coupled to the patterning surface via one or more mounting portions, wherein the one or more mounting portions electrically isolate the protective membrane from the patterning surface.12. The arrangement of any of clauses 4 to 10, wherein the membrane frame is coupled to the patterning surface via one or more mounting portions, wherein the one or more mounting portions electrically connect the protective membrane and the patterning surface.13. The arrangement of any of clauses 6 to 12, wherein: the support surface comprises a first conductive portion and a second conductive portion; the first conductive portion of the support surface and the second conductive portion of the support surface are substantially electrically isolated from one another; the first conductive portion of the support surface is electrically connected to a first voltage source and the second conductive portion of the support surface is electrically connected to a second voltage source; the protective membrane is electrically connected to the first voltage source via the connecting element and the first conductive portion of the support surface; and the non-patterning surface of the patterning device is electrically connected to the second voltage source via the second conductive portion of the support surface.14. The arrangement of clause 13, wherein the non-patterning surface of the patterning device is electrically connected to the second conductive portion of the support surface via one or more conductive support protrusions.15. The arrangement of clause 14, wherein the one or more conductive support protrusions comprise a conductive coating.16. The arrangement of any of the preceding clauses, wherein the patterning surface is electrically isolated from the non-patterning surface.17. The arrangement of any of clauses 1 to 16, wherein the patterning surface is electrically connected to the non-patterning surface.18. The arrangement of clause 17, wherein the patterning surface is electrically connected to the nonpatterning surface via a conductive edge, optionally wherein the conductive edge comprises a conductive coating applied to a side of the patterning device extending between the patterning surface and the non-patterning surface.19. The arrangement of any of clauses 1 to 12, wherein: the support surface comprises a first conductive portion, a second conductive portion and a third conductive portion; the first conductive portion of the support surface, the second conductive portion of the support surface and the third conductive portion of the support surface are substantially electrically isolated from each another;the non-patterning surface of the patterning device comprises a first conductive portion and a second conductive portion, wherein the first conductive portion of the non-patterning surface is substantially electrically isolated from the second conductive portion of the non-patterning surface; the first conductive portion of the support surface is electrically connected to a first voltage source, the second conductive portion of the support surface is electrically connected to a second voltage source, and the third conductive portion of the support surface is electrically connected to a third voltage source; the protective membrane is electrically connected to the first voltage source via the connecting element and the first conductive portion of the support surface; the first conductive portion of the non-patterning surface of the patterning device is electrically connected to the second voltage source via the second conductive portion of the support surface; and the second conductive portion of the non-patterning surface of the patterning device is electrically connected to the third voltage source via the third conductive portion of the support surface; and the patterning surface of the patterning device is electrically connected to at least one of the conducting portions on the non-patterning surface.20. The arrangement of clause 18, wherein the second conductive portion of the non-patterning surface is larger than the first conductive portion of the non -patterning surface.21. The arrangement of clause 18 or 19, wherein the first conductive portion of the non-patterning surface is electrically connected to the patterning surface, such that the patterning surface is electrically connected to the second voltage source via the first conductive portion of the non-patterning surface and the second conductive portion of the support surface.22. The arrangement of any of clauses 18 to 21, wherein the first conductive portion of the nonpatterning surface is electrically connected to the second conductive portion of the support surface via one or more first conductive support protrusions, and the second conductive portion of the nonpatterning surface is electrically connected to the third conductive portion of the support surface via one or more second conductive support protrusions.23. The arrangement of any of clauses 3 to 5, wherein the protective membrane is electrically connected to the voltage source via the membrane frame, the patterning device, and the support structure.24. The arrangement of clause 23, wherein the protective membrane is electrically connected to a conductive edge of the patterning device.25. The arrangement of clause 23, wherein the membrane frame is coupled to the patterning surface via one or more mounting portions, wherein the one or more mounting portions are conductive, and the conductive portion of the membrane frame is electrically connected to the patterning surface via the one or more mounting portions.26. The arrangement of any of clauses 23 to 25, wherein the patterning surface is electrically connected to the non-patterning surface.27. The arrangement of clause 26, wherein the patterning surface is electrically connected to the nonpatterning surface via a conductive edge, optionally wherein the conductive edge comprises aconductive coating applied to a side of the patterning device extending between the patterning surface and the non-patterning surface.28. The arrangement of any of clauses 23 to 27, wherein: a conductive portion is provided on at least a portion of the support surface of the support structure; and the non-patterning surface of the patterning device is electrically connected to the conductive portion of the support surface via one or more conductive support protrusions.29. The arrangement of clause 28, wherein the one or more conductive support protrusions comprise a conductive coating.30. The arrangement of any of clauses 22 to 28, wherein: the support surface comprises a first conductive portion electrically connected to a first voltage source and one or more first conductive support protrusions; the support surface comprises a second conductive portion electrically connected to a second voltage source and one or more second conductive support protrusions; the first conductive portion of the support surface and the second conductive portion of the support surface are substantially electrically isolated from one another; the non-patterning surface comprises a first conductive portion and a second conductive portion; the first conductive portion of the non-patterning surface and the second conductive portion of the nonpatterning surface are substantially electrically isolated from one another; the first conductive portion of the non-patterning surface is electrically connected to the patterning surface; the second conductive portion of the non-patterning surface is substantially electrically isolated from the patterning surface; the protective membrane is electrically connected to the first voltage source via the patterning surface, the first conductive portion of the non-patterning surface, the one or more first conductive support protrusions and the first conductive portion of the support structure; and the second conductive portion of the non-patterning surface is electrically connected to the second voltage source via the one or more second conductive support protrusions and the second conductive portion of the support surface.31. The arrangement of clause 30, wherein an area of the second conductive portion of the nonpatterning surface is greater than an area of the first conductive portion of the non-patterning surface, optionally wherein the area of the second conductive portion of the non-patterning surface is greater than twice the area of the first conductive portion of the non-patterning surface, optionally wherein the area of the second conductive portion of the non-patterning surface is greater than five times the area of the first conductive portion of the non-patterning surface, optionally wherein the area of the second conductive portion of the non-patterning surface is greater than nine times the area of the first conductive portion of the non-patterning surface.32. The arrangement of any of clauses 3 to 31, wherein the membrane frame is formed from a material comprising metal, optionally wherein the metal comprises one or more of chromium, ruthenium and molybdenum.33. The arrangement of any of clauses 3 to 31, wherein a conductive coating is provided on at least a portion of the membrane frame to form the conductive portion of the membrane frame.34. The arrangement of clause 33, wherein: the conductive coating of the membrane frame is a metallisation, optionally wherein the metallisation comprises one or more of chromium, ruthenium and molybdenum; or the conductive coating of the membrane frame comprises a conductive ceramic, optionally wherein the conductive ceramic comprises chromium nitride or tantalum nitride.35. The arrangement of clause 33 or 34, wherein the membrane frame is formed from a material comprising silicon, and the conductive coating of the membrane frame is deposited on the material comprising silicon.36. The arrangement of any of clauses 33 to 35, wherein a portion of the conductive coating of the membrane frame which contacts the protective membrane is a contact portion, and wherein: the contact portion is interposed between the membrane frame and the protective membrane; or the conductive coating of the membrane frame extends around the protective membrane such that the protective membrane is interposed between the contact portion and the frame.37. The arrangement of any of clauses 33 to 36, wherein a portion of the conductive coating of the membrane frame which contacts the protective membrane is a contact portion, and wherein the contact portion extends around substantially all of the perimeter of the protective membrane.38. The arrangement of any of the preceding clauses, wherein a layer of conductive material is provided on a portion of the non-patterning surface, such that the layer of conductive material is disposed between the one or more conductive support protrusions and the non-patterning surface when the patterning device is supported by the support structure.39. The arrangement of clause 38, wherein the layer of conductive material comprises a material that is softer than a material which forms the non-patterning surface.40. The arrangement of clause 38 or 39, wherein the layer of conductive material comprises carbon, optionally wherein the layer of conductive material comprises graphite.41. The arrangement of any of the preceding clauses, wherein the patterning device comprises a conductive coating which forms the patterning surface and another conductive coating which forms the non-patterning surface.42. The arrangement of any of the preceding clauses, wherein the protective membrane is a pellicle.43. The arrangement of any of the preceding clauses, wherein the protective membrane is formed from a material comprising carbon nanotubes.44. The arrangement of any of the preceding clauses, wherein the protective membrane is formed of a material comprising a compound comprising at least two of molybdenum, silicon and nitrogen, optionally wherein the compound is MoSiN.45. A lithographic apparatus comprising the arrangement of any of the preceding clauses.46. A method of supporting a patterning device on a support structure, the method comprising use of the arrangement of any of clauses 1 to 44.47. A method of manufacturing a device, the method comprising use of the arrangement of any of clauses 1 to 44.48. A method of applying a bias voltage to a patterning device in a lithographic apparatus, the method comprising: determining whether a protective membrane is disposed in front of a patterning surface of the patterning device; in a case that the lithographic apparatus is in the production state and the protective membrane is determined to be disposed in front of the patterning surface, applying a first bias voltage to the patterning surface; and in a case that the lithographic apparatus is in the production state and the protective membrane is determined not to be disposed in front of the patterning device, applying a second bias voltage to the patterning surface.49. The method of clause 48, wherein the second bias voltage is negative.50. The method of clause 48 or 49, wherein a magnitude of the second bias voltage is greater than 1 V.51. The method of any of clauses 48 to 50, wherein a magnitude of the second bias voltage is less than 30V, optionally less than 10 V.52. The method of any of clauses 48 to 51 , further comprising, in the case that the lithographic apparatus is in the production state and the protective membrane is determined to be disposed in front of the patterning surface, applying a third bias voltage to the protective membrane.53. The method of clause 52, wherein the third bias voltage is positive.54. The method of clause 53, wherein a magnitude of the third bias voltage is less than 30V, optionally less than 10 V.55. The method of any of clauses 48 to 54, further comprising, in a case that the lithographic apparatus is in a loading state or an unloading state, grounding at least one of the patterning surface and the protective membrane.56. The method of any of clauses 48 to 55, further comprising determining a state of the lithographic apparatus from a plurality of possible states, the plurality of possible states including the production state, the loading state and the unloading state.57. The method of clause 55 or 56, wherein the grounding of the patterning surface and / or the protective membrane in the case that the lithographic apparatus is in the loading state or the unloading state is instead of applying the first bias voltage and / or the second bias voltage and / or the third bias voltage.58. The method of any of clauses 55 to 57, wherein the lithographic apparatus is in the unloading state for the duration of an unloading period, wherein the unloading period is a period comprising a predetermined time before the patterning device is unloaded from a support structure and / or a predetermined time after the patterning device has been unloaded from the support structure, optionally wherein the predetermined time is greater than 1 s, optionally greater than 5 s, and optionally greater than 9 s, less than 30 s, optionally less than 20 s, and optionally less than I l s.59. The method of any of clauses 49 to 51, wherein the lithographic apparatus is in the loading state for the duration of a loading period, wherein the loading period is a period comprising a predetermined time before the patterning device is loaded onto a support structure and / or a predetermined time after the patterning device has been loaded onto the support structure, optionally wherein the predetermined time is greater than 1 s, optionally greater than 5 s, and optionally greater than 9 s, less than 30 s, optionally less than 20 s, and optionally less than I l s.60. The method of any of clauses 48 to 59, wherein the third bias voltage is applied to the protective membrane via a support structure.61. The method of any of clauses 48 to 60, wherein the third bias voltage is applied to the protective membrane via a connecting element and the support surface of the support structure.62. The method of clause 61, wherein the patterning device, the support structure and the protective membrane form part of the arrangement of any of clauses 6 to 22.63. The method of clause 61 or 62, wherein the third bias voltage is different to the first bias voltage.64. The method of clause 63, wherein a difference between the third bias voltage and the first bias voltage is less than 10 V.65. The method of clause 48 to 60, wherein the third bias voltage is applied to the protective membrane via the patterning device and the support structure.66. The method of clause 65, wherein the patterning device, the support structure and the protective membrane form part of the arrangement of any of clauses 22 to 31.67. The method of clause 65 or 66, wherein the third bias voltage is substantially the same as the first bias voltage.68. The method of any of clauses 48 to 67, further comprising grounding at least a larger portion of a non-patterning surface of the patterning device while the patterning device is supported by the support structure.69. The method of any of clauses 48 to 68, wherein the at least a larger portion of the non-patterning surface is grounded via the support surface of the support structure while the patterning device is supported by the support structure.70. The method of any of clauses 48 to 69, further comprising, in a case that the lithographic apparatus is in the loading state or the unloading state, applying a fourth bias voltage to the non-patterning surface, optionally wherein a magnitude of the fourth bias voltage is less than 100 V, and further optionally wherein the magnitude of the fourth bias voltage is less than 10 V.71. The method of any of clauses 48 to 70, further comprising, in a case that the lithographic apparatus is in the production state, applying a fifth bias voltage to the non-patterning surface, optionally wherein a magnitude of the fifth bias voltage is less than 30 V, and further optionally wherein the magnitude of the fourth bias voltage is less than 10 V. 72. A method of manufacturing a device, the method comprising the method of clause any of clauses48 to 71.73. A controller for a lithographic apparatus, the controller comprising a computer-readable storage medium comprising instructions which, when executed by the controller, cause the lithographic apparatus to carry out the method of any of clauses 48 to 71. 74. A lithographic apparatus comprising the controller of clause 73.While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described.

[0186] 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. An arrangement for a lithographic apparatus, the arrangement comprising: a patterning device configured to impart a pattern to a beam of radiation, the patterning device5 comprising a patterning surface with a pattern thereon; a support structure configured to support the patterning device; and a protective membrane disposed in front of the patterning surface; wherein the protective membrane is electrically connected to the support structure. 0 2. The arrangement of claim 1 , wherein: the support structure comprises a support surface which faces a non-patterning surface of the patterning device; the support structure comprises a plurality of support protrusions extending from the support surface; 5 the non-patterning surface of the patterning device is supported on distal ends of the plurality of support protrusions; and a portion of the support surface from which the support protrusions extend is a clamping surface. 0 3. The arrangement of claim 1 or 2, further comprising a voltage source, wherein the protective membrane is electrically connected to the voltage source via the support structure.

4. The arrangement of any of the preceding claims, wherein the patterning surface is electrically isolated from the non-patterning surface.

55. The arrangement of any of claims 1 to 4, wherein the patterning surface is electrically connected to the non-patterning surface.

6. The arrangement of claim 5, wherein the patterning surface is electrically connected to the non-0 patterning surface via a conductive edge, optionally wherein the conductive edge comprises a conductive coating applied to a side of the patterning device extending between the patterning surface and the non-patterning surface.

7. The arrangement of claim 6, wherein the first conductive portion of the non-patterning surface5 is electrically connected to the patterning surface, such that the patterning surface is electrically connected to the second voltage source via the first conductive portion of the non-patterning surface and the second conductive portion of the support surface.

8. The arrangement of any of claims 6 and 7, wherein the first conductive portion of the nonpatterning surface is electrically connected to the second conductive portion of the support surface via one or more first conductive support protrusions, and the second conductive portion of the nonpatterning surface is electrically connected to the third conductive portion of the support surface via one or more second conductive support protrusions.

9. The arrangement according to claim 3, wherein the protective membrane is electrically connected to the voltage source via the membrane frame, the patterning device, and the support structure.

10. The arrangement of claim 9, wherein: a conductive portion is provided on at least a portion of the support surface of the support structure; and the non-patterning surface of the patterning device is electrically connected to the conductive portion of the support surface via one or more conductive support protrusions.

11. The arrangement of any of the preceding claims, wherein the protective membrane is formed from a material comprising carbon nanotubes.

12. The arrangement of any of the preceding claims, wherein the protective membrane is formed of a material comprising a compound comprising at least two of molybdenum, silicon and nitrogen, optionally wherein the compound is MoSiN.

13. A lithographic apparatus comprising the arrangement of any of the preceding claims.

14. A method of supporting a patterning device on a support structure, the method comprising use of the arrangement of any of claims 1 to 13.

15. A method of applying a bias voltage to a patterning device in a lithographic apparatus, the method comprising: determining whether a protective membrane is disposed in front of a patterning surface of the patterning device; in a case that the lithographic apparatus is in the production state and the protective membrane is determined to be disposed in front of the patterning surface, applying a first bias voltage to the patterning surface; andin a case that the lithographic apparatus is in the production state and the protective membrane is determined not to be disposed in front of the patterning device, applying a second bias voltage to the patterning surface.

16. The method of claim 15, wherein the second bias voltage is negative.

17. The method of any of claims 15 to 16, further comprising, in the case that the lithographic apparatus is in the production state and the protective membrane is determined to be disposed in front of the patterning surface, applying a third bias voltage to the protective membrane.

18. The method of claim 17, wherein the third bias voltage is positive.

19. The method of any of claims 15 to 18, further comprising, in a case that the lithographic apparatus is in a loading state or an unloading state, grounding at least one of the patterning surface and the protective membrane.

20. The method of claim 19, wherein the grounding of the patterning surface and / or the protective membrane in the case that the lithographic apparatus is in the loading state or the unloading state is instead of applying the first bias voltage and / or the second bias voltage and / or the third bias voltage.

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