Pellicle for use in a lithographic apparatus and method of forming a pellicle - Patent application

Abstract

A pellicle for use in a lithographic apparatus, the pellicle comprising a membrane having a first portion and a second portion, and a protective portion in the second portion on at least one side of the membrane.A method of forming a pellicle for use in a lithographic apparatus, the method comprising providing a membrane having a first portion and a second portion, and providing a protective portion in the second portion on at least one side of the membrane.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to European Application No. 22195223.7, filed September 12, 2022, and U.S. Application No. 63 / 451,809, filed March 13, 2023, both of which are incorporated by reference in their entireties.

[0002] This description relates to pellicles for use in lithographic apparatus and related methods for forming such pellicles. This description also relates to lithographic apparatus including a pellicle positioned in the path of a radiation beam of the lithographic apparatus (used to form an image on a substrate). [Background technology]

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can, for example, project a pattern in a patterning device (e.g. a mask) onto a layer of radiation-sensitive material (resist) provided on the substrate.

[0004]

[0004] To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. Lithographic apparatus using extreme ultraviolet (EUV) radiation having a wavelength in the range of 4 to 20 nm, e.g., 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than lithographic apparatus using radiation having a wavelength of, e.g., 193 nm.

[0005]

[0005] A patterning device (e.g. a mask) is used in a lithographic apparatus to impart a pattern to a radiation beam. The patterning device may be protected from particle contamination by a pellicle. The pellicle may be supported by a pellicle frame.

[0006]

[0006] A typical pellicle is a membrane that is positioned away from the patterning device and out of the focal plane of the lithography apparatus in use. Because the pellicle is out of the focal plane of the lithography apparatus, contaminant particles that adhere to the pellicle will be out of focus within the lithography apparatus. As a result, images of the contaminant particles will not be projected onto the substrate. Without the pellicle, contaminant particles that adhere to the patterning device will be projected onto the substrate, causing defects in the projected pattern.

[0007] It may be desirable to provide an apparatus and / or method that avoids or mitigates one or more problems associated with the prior art. Summary of the Invention

[0008] According to a first aspect, there is provided a pellicle for use in a lithographic apparatus, the pellicle comprising a membrane comprising a first portion and a second portion, and a protective portion on at least one side of the membrane in the second portion. For example, the pellicle for use in a lithographic apparatus may comprise a membrane comprising carbon nanotubes, the membrane comprising a first portion and a second portion, and a protective portion on at least one side of the membrane in the second portion, the protective portion comprising a material suitable for protecting the second portion of the membrane from etching.

[0009]

[0009] The film may, for example, include a layer having the same type of carbon nanotubes in both the first and second portions, and the material of the protective portion covering the second portion of the film is transparent to at least a portion of the EUV imaging radiation received by the first portion.

[0010]

[0010] An advantage is that the life of the pellicle can be extended without affecting the performance of the lithographic apparatus.

[0011] The protective portion may be present only on or above the second portion. The protective portion may not be present on or above the first portion. The protective portion may be present on or above the first portion to a lesser extent than the second portion. The protective portion may be directly on the film, in contact with the film, and / or supported by the film. The protective portion may be, for example, a layer thick enough to chemically protect the second portion from the (e.g., plasma) etching environment, yet thin enough so that the second portion remains substantially transparent to EUV radiation. The protective portion may be a layer of material deposited in direct contact with the film, or may be thicker because it is etched to a lesser extent than the first portion in the film manufacturing process. In other words, if the first and second portions are the same, the difference between the first and second portions is that the second portion is thicker than the first portion of the film. The material of the protective portion may alternatively be different from the material of the second portion of the film and / or the entire film. Hereinafter, the material of the protective portion will be collectively referred to as the "capping material." For example, if the membrane core is made from carbon nanotubes with certain properties (such as dimensions), the capping material forming the protective portion can either comprise a different material than the membrane or carbon nanotubes with different properties than the membrane, but can also have the same carbon nanotube composition as the membrane (core), provided the second portion is thicker than the first portion (the protective portion is a layer of carbon nanotubes with a thickness equal to the difference in thickness between the first and second portions).

[0012] Alternatively, the protection may be a free-standing element separated from the membrane (e.g., by a gap). The free-standing element may be, for example, a plate, a rigid membrane, or a protruding element. In this case, the protection can still be considered to be adjacent to / on at least one side of the membrane.

[0013] At least one side of the membrane may be the front side of the membrane, i.e. the side on which EUV radiation (EUV radiation beam B) is incident from the radiation source SO and / or illumination system. The front side may be opposite the back side (second side), i.e. the side facing the patterning device in use. The front side may be opposite the side attached to the pellicle frame.

[0014] In use, the second portion may not receive EUV imaging radiation, or may receive only a portion of the EUV imaging radiation received by the first portion. However, for clarity, the second portion is transparent to EUV imaging radiation, so that when, in use, the second portion receives EUV imaging radiation or a portion of the EUV imaging radiation received by the first portion, at least a portion of the received EUV radiation is transmitted through the membrane.

[0015] The second portion may be, for example, an unexposed region that etches faster during exposure. The faster etch rate of the second unexposed region is believed to be due to its lower temperature than the exposed region, in a context where the etch rate of the carbon-based film is faster.

[0016] The first portion may substantially correspond to a predetermined exposure area of ​​a patterning device for use with the pellicle.

[0017] The first portion may be substantially the same size as a predetermined exposure area of ​​the patterning device.

[0018]

[0018] The second portion may be located at the periphery of the membrane. The pellicle may have a boundary at the periphery of the membrane, and the second portion may coincide with the boundary. However, it should be understood that the boundary is not usually part of the second portion, and the boundary is not considered to be a protective region here. The boundary is usually not transparent to EUV radiation, and its function is only to support the membrane at the periphery from buckling or breaking due to contact with the frame. Only in exceptional cases can the boundary be considered a protective region, as it is very thin and transmits at least 10% of EUV radiation and can be illuminated with exposure radiation. For example, the pellicle may have a boundary at the periphery of the membrane, and the size of the second portion may coincide with the boundary, and the boundary may be located on the side of the membrane opposite the protective portion.

[0019] The protective portion may comprise a material suitable for protecting the second portion of the membrane from hydrogen etching.

[0020]

[0020] The protective portion may be on at least one of a first side and an opposite second side of the membrane, and an edge of the membrane.

[0021]

[0021] The protection may be on only one side of the membrane (eg the front side of the membrane).

[0022]

[0022] The first side of the membrane may be the front side of the membrane. The second side of the membrane may be the back side of the membrane.

[0023] The protective portion may include a material that covers the second portion (also called a capping material).

[0024]

[0024] The capping material may be carbon nanotubes, graphene, amorphous carbon, (low melting point metal), molybdenum (Mo), yttrium (Y), yttrium oxide (Y a O b), aluminum oxide (Al2O3) (AlO2), hafnium oxide (HfO2), zirconium oxide (ZrO2), ruthenium (Ru), platinum (Pt), gold (Au), zirconium nitride (ZrN), aluminum (Al), zirconium (Zr), silicon (Si), silicon carbide (SiC), silicon oxide (SiO a ), boron (B), boron carbide (BC), boron nitride (BN), titanium (Ti), and titanium nitride (TiN).

[0025]

[0025] The membrane may include a protective portion, and the protective portion may include the same material as the first and second portions.

[0026]

[0026] The pellicle may include a pellicle frame, the protective portion may include a shield, and the shield may be supported by the pellicle frame.

[0027] The shield may be separated from the membrane by a gap, which is preferably less than 1000 μm or less than 2000 μm.

[0028] The shield may be at least one of substantially transparent to heater radiation, substantially transparent to IR radiation, substantially transparent to DUV radiation, and inert to the plasma.

[0029]

[0029] The shield may include at least one of aluminum oxide (Al2O3), sapphire, aluminum oxide (Al2O3) coated glass, and sapphire coated glass.

[0030]

[0030] The guard may include multiple shields, a first shield on a first side of the membrane and a second shield on an opposite second side of the membrane.

[0031] The first portion may correspond substantially to an extended area that is larger than a predetermined exposure area of ​​a patterning device for use with the pellicle.

[0032]

[0032] The extension region may extend a predetermined distance outward from the predetermined exposure region of the patterning device.

[0033] The extension region may extend outside the predetermined exposure region of the patterning device by at least one of 1000 μm, a range of 1000-2000 μm, and a range of 1000-4000 μm.

[0034]

[0034] The second portion may extend a predetermined distance inward relative to the inner edge of the pellicle frame and / or the boundary of the peripheral portion of the membrane.

[0035]

[0035] The second portion may extend inward relative to the inner edge and / or boundary of the pellicle frame at least 1300 μm, at least 1500 μm, at least 2300 μm, in the range of 1300 μm to 2300 μm.

[0036]

[0036] The membrane may comprise a carbon-based material such as carbon nanotubes.

[0037]

[0037] According to a second aspect, there is provided a lithographic apparatus operable to form an image of a patterning device on a substrate using a radiation beam, the lithographic apparatus comprising a pellicle positioned in the path of the radiation beam, the pellicle being as described above.

[0038] According to a third aspect, there is provided a method of forming a pellicle for use in a lithographic apparatus, the method comprising providing a membrane comprising a first portion and a second portion, and providing a protective portion on the second portion on at least one side of the membrane. For example, a method of forming a pellicle for use in a lithographic apparatus may comprise providing a membrane comprising carbon nanotubes, the membrane comprising a first portion and a second portion, and providing a protective portion on the second portion on at least one side of the membrane, the protective portion comprising a material suitable for protecting the second portion of the membrane from etching.

[0039]

[0039] The method may further include providing the protective portion using an additive or subtractive process.

[0040]

[0040] The method may further include providing a protective portion using an additive process, where the protective portion may include a capping material, and depositing the capping material on the second portion to cover the second portion.

[0041]

[0041] The method may further include masking the first portion using a masking element.

[0042]

[0042] The masking element may substantially correspond to a predetermined exposure area of ​​a patterning device for use with a pellicle.

[0043]

[0043] The method may further include depositing the capping material using at least one of thermal evaporation, electron beam evaporation, electron beam deposition, pulsed laser deposition, atomic layer deposition, and remote plasma sputtering.

[0044]

[0044] The method may further include providing a protective portion using a subtractive method, where the protective portion may include a capping material, applying the capping material onto the first portion and the second portion, and removing the capping material from the first portion.

[0045]

[0045] The method may further include removing the capping material from the first portion using at least one of laser annealing, laser ablation, reactive ion etching, and lift-off.

[0046] The capping material may be a volatile or thermally unstable material that is desorbed by EUV radiation.

[0047]

[0047] The method may further include providing a protective portion using a subtractive method including providing a thickness to the film and partially removing the first portion to reduce the thickness of the first portion, and the film may include the protective portion, and the protective portion may comprise the same material as the first portion and the second portion.

[0048] The method may further include etching the first portion with a hydrogen plasma.

[0049]

[0049] The method may include providing protection to at least one of the first side and the opposite second side of the membrane and an edge of the membrane.

[0050] The method may further include providing a first portion substantially corresponding to a predetermined exposure area of ​​a patterning device for use with the pellicle.

[0051]

[0051] The method may further comprise providing the protection during at least one of pellicle manufacturing, patterning device manufacturing, and substrate manufacturing.

[0052]

[0052] The method may further include providing a pellicle frame, and the protective portion may include a shield, and the pellicle frame may support the shield.

[0053]

[0053] The method may further include separating the shield from the membrane by a gap.

[0054]

[0054] The method may further include providing a plurality of shields, such as a first shield on a first side of the membrane and a second shield on an opposite second side of the membrane.

[0055] The method may further comprise providing the first portion to substantially correspond to an extended area that is larger than the predetermined exposure area of ​​the patterning device for use with the pellicle. [Brief explanation of the drawings]

[0056]

[0056] Some embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings.

[0057]

[0057] [Figure 1] FIG. 1 depicts a lithography system comprising a lithographic apparatus and a radiation source.

[0058] [Figure 2] FIG. 2 shows a schematic cross-section of a pellicle and patterning device according to an embodiment of the present disclosure.

[0059] [Figure 3] FIG. 3 shows a schematic plan view of the pellicle of FIG.

[0060] [Figure 4] Figure 4 shows the predicted etch rate for hydrogen etching of carbon as a function of temperature for a hydrogen ion flux of 1.5·1019 m-2·s-1 for four different ion energies: 5 eV, 10 eV, 20 eV, and 30 eV. Figure 4 also shows the sp3 carbon concentration as a function of temperature.

[0061] [Figure 5] FIG. 5 is a schematic diagram of a method of forming a pellicle according to an embodiment of the present disclosure.

[0062] [Figure 6] FIG. 6 shows a schematic cross-section of a pellicle and patterning device according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0058]

[0063] Figure 1 shows a lithography system including a pellicle 15. The lithography system comprises a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate a beam of EUV radiation B and to provide this beam of EUV radiation B to the lithography apparatus LA. The lithography 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.

[0059]

[0064] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA, which is held by the support structure MT. To that end, the illumination system IL may include a facetted field mirror device 10 and a facetted pupil mirror device 11. Together, the facetted field mirror device 10 and the facetted pupil mirror device 11 impart a desired cross-sectional shape and a desired intensity distribution to the EUV radiation beam B. The illumination system IL may include other mirrors or devices in addition to or instead of the facetted field mirror device 10 and the facetted pupil mirror device 11. The patterning device MA is protected by a pellicle 15. The pellicle 15 includes a film 19 held in place by a pellicle frame 17. The film 19 and the pellicle frame 17 together form the pellicle 15.

[0060]

[0065] After being conditioned in this way, the EUV radiation beam B interacts with the patterning device MA. This interaction results in a patterned EUV radiation beam B'. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. To this end, the projection system PS may comprise a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by a substrate table WT. The projection system PS may apply a demagnification factor to the patterned EUV radiation beam B' to form images of features that are smaller than corresponding features on the patterning device MA. For example, a demagnification factor of 4 or 8 may be applied. Although the projection system PS is shown in Figure 1 as having only two mirrors 13, 14, the projection system PS may include a different number of mirrors (for example 6 or 8 mirrors).

[0061]

[0066] The substrate W may include a pre-formed pattern, in which case the lithographic apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pre-formed pattern on the substrate W.

[0062]

[0067] A relative vacuum, ie a small amount of gas (eg hydrogen) at a pressure significantly below atmospheric pressure, may be provided within the source SO, illumination system IL, and / or projection system PS.

[0063]

[0068] The radiation source SO shown in FIG. 1 is of a type that may be referred to as a laser-produced plasma (LPP) source. A laser system 1, which may include, for example, a CO laser, is configured to impart energy via a laser beam 2 to a fuel, such as tin (Sn), provided from a fuel emitter 3. While the following description refers to tin, any suitable fuel may be used. The fuel may be, for example, in liquid form or may be, for example, a metal or alloy. The fuel emitter 3 may include a nozzle configured to direct the tin, for example, in the form of droplets, along a trajectory toward a plasma formation region 4. The laser beam 2 is incident on the tin in the plasma formation region 4. The application of laser energy to the tin generates a tin plasma 7 in the plasma formation region 4. Radiation, including EUV radiation, is emitted from the plasma 7 during de-excitation and recombination of electrons with the ions of the plasma.

[0064]

[0069] EUV radiation from the plasma is collected and focused by a collector 5. Collector 5 may include, for example, a near-normal incidence radiation collector 5 (which may more commonly be referred to as a normal incidence radiation collector). Collector 5 may have a multi-layer mirror structure configured to reflect EUV radiation (e.g., EUV radiation having a desired wavelength, such as 13.5 nm). Collector 5 may have an elliptical configuration with two foci. As discussed below, the first focus may be the plasma formation region 4 and the second focus may be an intermediate focus 6.

[0065]

[0070] The laser system 1 may be spatially separated from the radiation source SO, in which case the laser beam 2 may be routed from the laser system 1 to the radiation source SO using a beam delivery system (not shown), which may comprise, for example, suitable directing mirrors and / or beam expanders and / or other optics. The laser system 1, the radiation source SO and the beam delivery system together may be considered as a radiation system.

[0066]

[0071] Radiation reflected by collector 5 forms EUV radiation beam B. EUV radiation beam B is focused at intermediate focus 6 to form an image at intermediate focus 6 of the plasma present in plasma formation region 4. The image at intermediate focus 6 acts as a virtual radiation source for the illumination system IL. The radiation source SO is configured such that intermediate focus 6 is located at or near an aperture 8 in an enclosure 9 of the radiation source SO.

[0067]

[0072] Although FIG. 1 illustrates the source SO as a laser-produced plasma (LPP) source, any suitable source, such as a discharge-produced plasma (DPP) source or a free-electron laser (FEL), may be used to generate EUV radiation.

[0068]

[0073] As briefly described above, pellicle 15 includes a film 19 provided adjacent to patterning device MA. Film 19 is provided in the path of radiation beam B such that radiation beam B passes through film 19 both when approaching patterning device MA from illumination system IL and when reflected by patterning device MA towards projection system PS. Film (or thin film) 19 is substantially transparent to EUV radiation (although it will absorb small amounts of EUV radiation). As used herein, an EUV-transmitting film or a thin film substantially transparent to EUV radiation means that film 19 transmits at least 65% of EUV radiation, preferably at least 80%, and more preferably at least 90% of EUV radiation. Film 19 serves to protect patterning device MA from particle contamination. As used herein, film 19 may be referred to as an EUV-transmitting film.

[0069]

[0074] While efforts can be made to maintain a clean environment within the lithographic apparatus LA, particles may still be present within the lithographic apparatus LA. In the absence of the film 19, particles may accumulate on the patterning device MA. Particles on the patterning device MA may adversely affect the pattern imparted to the radiation beam B, and therefore the pattern transferred to the substrate W. The film 19 advantageously provides a barrier between the patterning device MA and the environment within the lithographic apparatus LA to prevent particles from accumulating on the patterning device MA.

[0070]

[0075] In use, the membrane 19 is positioned a sufficient distance from the patterning device MA so that any particles incident on the surface of the membrane 19 are not in the focal plane of the radiation beam B. This separation between the membrane 19 and the patterning device MA serves to reduce the extent to which any particles on the surface of the membrane 19 will impart a pattern to the radiation beam B. It will be appreciated that if a particle is present in the radiation beam B but not in a position in the focal plane of the radiation beam B (i.e., not at the surface of the patterning device MA), any image of the particle will not be focused on the surface of the substrate W. Absent other considerations, it may be desirable to position the membrane 19 a significant distance from the patterning device MA. However, in practice, the space available within the lithographic apparatus LA to accommodate the pellicle 15 is limited due to the presence of other components. In some embodiments, the separation between the membrane 19 and the patterning device MA may be, for example, between approximately 1 mm and 10 mm, for example between 1 mm and 5 mm, for example between 2 mm and 3 mm (e.g., approximately 2.5 mm), for example between 2 mm and 2.5 mm. In some embodiments, the separation between membrane 19 and patterning device MA may be adjustable.

[0071]

[0076] Pellicle 15 may include a boundary. The boundary of pellicle 15 may be hollow and generally rectangular, and membrane 19 may be surrounded by the boundary. As is known in the art, one type of pellicle can be formed by depositing one or more thin layers of material onto a generally rectangular silicon substrate. The silicon substrate supports the one or more thin layers during this build stage of the pellicle. Once the desired or target thickness and composition of the layers has been applied, the center of the silicon substrate is etched away (this is sometimes called back-etching). The periphery of the rectangular silicon substrate is not etched (or alternatively, is etched less than the center). This periphery forms the boundary of the final pellicle, while the one or more thin layers form the membrane (bounded by the boundary) of the pellicle. The pellicle's boundary can be formed from silicon.

[0072]

[0077] Some embodiments of the present disclosure relate to new types of pellicles and methods of forming such pellicles.

[0073]

[0078] Pellicle 15 (e.g., including its border) may require some support from a more rigid pellicle frame 17. Pellicle frame 17 can serve two functions. First, pellicle frame 17 can support and tension membrane 19. Second, pellicle frame 17 can facilitate connection of pellicle 15 with a patterning device (reticle or photomask) MA. In one known configuration, pellicle frame 17 may comprise a generally rectangular body that is bonded to the border of pellicle 15 and titanium mounting mechanisms bonded to the sides of the body. Intermediate fixation members (known as studs) are secured to the patterning device (reticle) MA. The intermediate fixation members (studs) on the patterning device (reticle) MA can engage (e.g., releasably engage) with mounting members on pellicle frame 17.

[0074]

[0079] FIG. 2 is a more detailed schematic diagram of the pellicle 15 and patterning device MA shown in FIG. 1 . Pellicle 15 includes a pellicle frame 17 (hereafter referred to as the frame) and membrane 19. Although not shown in FIG. 1 , pellicle 15 includes a pellicle boundary 20. Boundary 20 can optionally be integral with, included within, or physically separate from membrane 19. Boundary 20 may be significantly thicker than the main portion of membrane 19 and disposed around the outer periphery (periphery) of membrane 19. It is this boundary 20 that is attached to frame 17. Frame 17 supports pellicle 15 around the peripheral portion of membrane 19 via boundary 20. Boundary 20 may be glued or otherwise attached to frame 17. In embodiments, membrane 19 and boundary 20 are fabricated together (i.e., simultaneously). In some embodiments, boundary 20 may be integral with frame 17. It will be appreciated that in other embodiments, the pellicle 15 may not include a boundary, i.e., the membrane 19 may be formed directly on the frame 17 .

[0075]

[0080] Frame 17 may include engagement features 22 configured to allow frame 17 to be removably attached to (i.e., allow frame 17 to be attached to and detached from) the patterning device MA. Engagement features 22 are configured to engage with mounting members 24 provided on the patterning device MA. Mounting members 24 may be, for example, protrusions or studs extending from the patterning device MA. Engagement features 22 may include, for example, locking members (not shown) that engage with mounting members 24 and secure frame 17 to the patterning device MA.

[0076]

[0081] There may be a plurality of engagement features 22 and associated mounting members 24. The engagement features 22 may be distributed around the periphery of the frame 17. The associated mounting members may be distributed around the periphery of the patterning device MA.

[0077]

[0082] The patterning device MA has a patterned surface 25. A contaminant particle 26 is shown schematically. The contaminant particle 26 is incident on and retained by the membrane 19. The membrane 19 retains the contaminant particle 26 a sufficient distance from the patterned surface 21 of the mask MA to prevent it from being projected onto a substrate by the lithographic apparatus LA. The pellicle 15 provides a mask pattern (on the patterning device MA) that is protected from contamination by the pellicle 15, such that patterns generated using the mask will be substantially defect-free during use.

[0078]

[0083] Pellicle 15 can be constructed by depositing membrane 19 directly onto a substrate that provides boundary 20. After depositing membrane 19 of pellicle 15, the substrate can be selectively back-etched to remove a central portion of the substrate, leaving only the periphery to form boundary 20 that supports membrane 19. Alternatively, the material for boundary 20 can be deposited, which can be advantageous in some cases, as it avoids the challenges and stresses of selective removal.

[0079]

[0084] The pellicle 15 may be suitable for use adjacent to a reticle MA in an EUV lithography apparatus LA. During use, such a (reflective) MA is illuminated with EUV radiation, for example from an illumination system IL. It will be appreciated that the reticle MA is configured to impart a radiation beam received from the illumination system IL with a pattern in its cross-section to form a patterned radiation beam. A projection system collects the (reflected) patterned radiation beam and forms a (diffraction-limited) image of the reticle MA on a substrate (e.g. a resist-coated silicon wafer). Typically, any contamination on the reticle MA will alter the image formed on the substrate, leading to printing errors.

[0080]

[0085] To avoid particle contamination of the reticle MA, a pellicle 15 is used to protect the reticle MA. As previously mentioned, the pellicle 15 is positioned in front of the reticle MA to prevent particles 26 from landing on the reticle MA. The film 19 of the pellicle 15 is positioned so that it is not sharply imaged by the projection system, so that particles on the film 19 do not interfere with the imaging process. It is desirable for the film 19 to be as thin as possible to reduce absorption of EUV radiation by the film 19, while still being strong enough to prevent particles 26 from impinging on the reticle MA and causing unacceptable printing errors.

[0081]

[0086] The pellicle 15 includes a protective portion 28. In this embodiment, the protective portion 28 is provided on the periphery of the film 19 and on a first side 30A. The first side 30A can be considered the front side, i.e., the side on which EUV radiation (EUV radiation beam B) is incident from the radiation source SO and / or illumination system IL. The first side 30A is opposite the side of the film 19 that faces the patterning device MA in use. The first side 30A is opposite the side of the film 19 that is attached to the pellicle frame 17. A boundary 20 is provided on the periphery of the film 19 and on a second side 30B. The second side 30B can be considered the back side, which faces the patterning device MA in use. The second side 30B is attached to the pellicle frame 17 (i.e., via the boundary 20). In other embodiments, a protective portion may alternatively or additionally be provided on the back side of the film. For example, there may be a protection on a portion of the surface on both sides (front [first] and back [second]) of the membrane. Furthermore, alternatively or additionally, a protection may be provided on the edge 30C of the membrane (i.e., the edge extending in the Z direction). Furthermore, in embodiments (e.g., using CNT membranes), the protection may be conformal (i.e., coated around the CNT tubes) or interstitial (i.e., interior space within the membrane). In general, a protection may be provided on any portion of the membrane that may need to be protected, for example, from etching. In embodiments, the protection on the front side of the membrane may cover a different area than the protection on the back side of the membrane. The protection on the back side of the membrane may also cover a boundary.

[0082]

[0087] The patterning device MA comprises an exposure region 32 and a non-exposure region 34 (separated as shown by dotted line 35). That is, during imaging, the exposure region 32 receives EUV radiation, and the non-exposure region 34 does not. The exposure region 32 has an area (in the xy plane) that forms at least a portion of the patterned surface 25. The exposure region 32 can be predetermined based on a particular selected or desired field size. The exposure region 32 can be a selected mask exposure field. The exposure region 32 can also be referred to as a mask imaging field. The exposure region 32 can be continuous, i.e., a single area. The exposure region 32 can include multiple dies (not shown), separated for cleavage or metrology, or can include a single die. The dies can be clustered. Where exposure regions are considered to be on separate dies, the exposure region can be continuous.

[0083]

[0088] The membrane 19 includes a first portion 36 and a second portion 38 (separated as shown by dotted line 39). The first portion 36 has a first area, and the second portion 38 has a second area (i.e., in the x-y plane). In an embodiment, the first portion 36 corresponds to a predetermined exposure region 32 of the patterning device MA. That is, the first portion 36 is substantially the same size (i.e., has the same area) as the exposure region 32. Similarly, the second portion 38 therefore extends inward (toward the center in the x-direction) to the same extent as the non-exposed region 34. It will be appreciated that because the patterning device MA may be larger in the x-direction than the membrane 19, the non-exposed region 34 may extend further outward (away from the center in the x-direction) than the second portion 38.

[0084]

[0089] It will also be appreciated that the first portion 36 can be considered an exposed region, and the second portion 38 can be considered an unexposed region, since only the first portion receives EUV radiation during imaging. However, in some embodiments, the distinction between the first portion 36 and the second portion 38 can relate to the amount of EUV imaging radiation incident thereon. For example, the first portion 36 can receive all (100%) of the maximum EUV power density, while the second portion 38 can receive only a portion (e.g., 50%) of the maximum EUV power density. In general, the second portion 38 can receive EUV imaging radiation during use, but may only receive a portion of the EUV imaging radiation (compared to the amount received by the first portion 36).

[0085]

[0090] As shown, the protective portion 28 is on the second portion 38 on the side of the film 19 (i.e., the front surface of the film 19). The protective portion 28 is not on the first portion 36. In other words, the protective portion 28 is only on the second portion 38, not on the first portion 36. The protective portion 28 covers the second portion 38, but not the first portion 36. The protective portion 28 can be considered to only partially cover the film 19. Furthermore, the protective portion 28 only covers the non-image area (i.e., the area of ​​the second portion 38).

[0086]

[0091] FIG. 3 is a plan view (front view) of pellicle 15 shown in FIG. 2. For clarity, frame 17 and patterning device MA are not included. First portion 36 of membrane 19 forms a rectangular shape substantially in the center of membrane 19. Second portion 38 is not visible in this view because it is underneath protective portion 28 in FIG. 2. However, it will be understood that second portion 38 surrounds first portion 36 on each side (with respect to the xy plane). Protective portion 28 is shown covering (i.e., covering the same area as) second portion 38. It will be understood that this is merely an example, and that other sizes and / or shapes of first portion, second portion, and / or protective portion may be provided.

[0087]

[0092] The pellicle 15 shown in Figures 2 and 3 is particularly advantageous as will be explained below.

[0088]

[0093] One particularly promising carbon-based material for use as a pellicle membrane in EUV lithography tools is a fabric or membrane formed from carbon nanotubes (CNTs). Because such CNT pellicles are porous, they can provide very high EUV transmittance (>98%). Furthermore, CNT pellicles also offer exceptional mechanical stability, allowing them to be fabricated at thin thicknesses while remaining robust against mechanical failure. However, low-pressure hydrogen gas is typically supplied within the lithography tool, and a hydrogen plasma is formed in the presence of EUV radiation (during exposure). The plasma is present in the lithography tool LA to remove carbon deposited on mirror surfaces, particularly in vacuum. However, this can lead to etching of the CNT membrane itself. It has been shown that hydrogen ions and hydrogen free radicals from the hydrogen plasma can etch pellicles formed from CNTs, potentially limiting the pellicle's potential lifetime and hindering commercial implementation of CNT pellicles.

[0089]

[0094] To mitigate etching of such CNT pellicles, it has previously been proposed to provide such CNT pellicles with a protective capping layer (coating). However, minimizing the absorption of EUV radiation by the pellicle is desirable, and including a capping layer increases EUV transmission loss. Furthermore, CNT film coatings are temperature sensitive and do not last (at least for the required time) in high-power lithography tools. Furthermore, the refractive index difference between carbon and a suitable capping layer is typically greater than the refractive index difference between carbon and vacuum. Therefore, such capping layers are undesirable because they increase EUV flare (scattered light), degrading image quality. The hydrogen plasma in lithography tools ultimately limits the lifetime of CNT pellicles, or any carbon-based pellicle.

[0090]

[0095] The interaction of hydrogen ions with carbon materials has been quantitatively described in two published articles, the contents of which are incorporated herein by reference: (1) J. Roth, C. Garcia-Rosales, "Analytic description of the chemical erosion of graphite by hydrogen ions," Nucl. Fusion 1996, 36 / 12, 1647-1659, and (2) J. Roth, C. Garcia-Rosales, "Corrigendum - Analytic description of the chemical erosion of graphite by hydrogen ions," Nucl. Fusion 1997, 37, 897. This quantitative description of the interaction of hydrogen ions with carbon materials is sometimes referred to as the Roth-Garcia-Rosales (RGR) model. The RGR model can be used to predict the etch yield of carbon materials as a function of temperature for typical hydrogen ion energies encountered in lithography tools, such as those forming ion energies between 1 and 30 eV. In an EUV lithography tool, a typical hydrogen ion flux incident on a pellicle can be on the order of 1·1019 m-2·s-1. In an EUV lithography tool, a typical hydrogen ion flux incident on a pellicle can be within several orders of magnitude of 1·1019 m-2·s-1 (e.g., 1018 m-2·s-1 to 1020 m-2·s-1).

[0091]

[0096] Figure 4 shows the expected hydrogen etch rate of carbon as a function of temperature for a hydrogen ion flux of 1.5·1019 m-2·s-1 for four different ion energies: 5 eV, 10 eV, 20 eV, and 30 eV. The figure shows the sp3 carbon concentration as a function of temperature. It can be seen that, under these typical ambient conditions within a lithography tool LA, for a pellicle formed purely from CNTs, the hydrogen etch rate of the pellicle is expected to drop to negligible levels at a temperature of approximately 1050 K. However, one skilled in the art will recognize that different minimum temperatures may be desirable under different conditions.

[0092]

[0097] Etching of carbon by hydrogen ions and free radicals can be temperature dependent. In particular, the carbon etch rate can be high at low and intermediate temperatures, but at sufficiently high temperatures, the carbon etch rate drops to negligible levels. Also, while the central portion of the film 19 in the EUV lithography scanner LA can reach a temperature high enough to make hydrogen etching negligible (at least part of the time), the periphery of the film 19 typically remains cooler and more susceptible to hydrogen etching. In other words, the CNT film heats up to a temperature that effectively limits the hydrogen plasma etch rate. This essentially creates multiple zones in the film 19, referred to as first portion 36 and second portion 38. In this embodiment, first portion 36 and second portion 38 are relatively hot (exposed) and relatively cold (unexposed) areas, respectively. However, it will be understood that in other embodiments, first portion 36 and second portion 38 (different zones) may be defined by other characteristics. Furthermore, the different zones (i.e., first portion 36 and second portion 38) may have different sizes and shapes as desired. In an embodiment, there may be multiple first portions 36 and / or multiple second portions 38. These may be separated, for example, two first portions 36 may be separated by a second portion 38, or vice versa.

[0093]

[0098] To maximize scanner life and performance, it is important to tailor each CNT pellicle zone (or section) to the application. The most exposed area of ​​the film (first section 36) is over the reticle exposure field. The least exposed area (second section 38) is over the frame area, where the optical requirements are less stringent.

[0094]

[0099] 2 and 3 provides an additional protection 28 on the second portion 38 (front surface 30A) of membrane 19 that (a) is most at risk of hydrogen etching and (b) is not exposed to EUV radiation during use, thereby extending the lifetime of pellicle 15 without affecting the performance of lithography apparatus LA.

[0095]

[0100] In some embodiments, the protection 28 is provided on a portion of the membrane 19 that will not be exposed to EUV radiation during use (during imaging [exposure]). The first portion 36 is exposed to EUV radiation (during imaging) and will heat up. The second portion 38 is not exposed to EUV radiation (during imaging) and will not heat up as a result. Therefore, the second portion 38 needs to be protected to enhance lifetime. It will be appreciated that the second portion 38 does not necessarily need to be precisely aligned with the exposure region 32 of the patterning device MA, i.e., it may be substantially coincident. For example, due to heat transfer from the EUV imaging radiation, a portion of the membrane 19 may be located (e.g., 0.25-2 mm) away from the portion that is (fully) exposed to EUV imaging radiation and will not be affected by etching (or at least not affected to an extent that is inconsequential for lifetime considerations). It will be appreciated that if second portion 38 does not receive (the full EUV imaging radiation) or first portion 36 corresponds to a predetermined exposure area 32 of the patterning device MA, the position of second portion 38, and therefore the position of protection portion 28, can take these distances into account, i.e. second portion 38 may start exactly where the exposure area ends, or may start a distance away from the exposure area (e.g. 0.25-2 mm) to take this heat transfer into account (i.e. towards the edge of film 19).

[0096]

[0101] The protective portion 28 may be provided on the film 19 so as to coincide in size with the boundary 20. That is, the protective portion 28 overlaps the boundary 20, but the boundary 20 is provided on the opposite side 30B of the film 19. For clarity, the boundary 20 serves to support the film 19, while the protective portion 28 serves to prevent a second portion of the film 19 (the portion not illuminated or only partially illuminated by EUV radiation) from being etched in the plasma environment generated around the film 19 during EUV exposure. However, the protective portion 28 may have a different size than the boundary, and may or may not coincide with the boundary, yet still cover the second film region outside the exposed first region. Thus, the material of the protective portion 28 can be selected to not only provide resistance to etching but also to be partially transparent to EUV radiation.

[0097]

[0102] If the size of protective portion 28 does not match boundary 20, protective portion 28 covers all of second portion 38, and because boundary 20 does not cover all of second portion 38 (the opposite side), protective portion 28 extends into the portion of membrane 19 that does not match boundary 20. That is, protective portion 28 extends partially inward into the area of ​​membrane 19 that is not attached to boundary 20. In some embodiments, protective portion 28 may be provided during pellicle manufacturing rather than during mask manufacturing. During pellicle manufacturing, the pellicle may not yet match the reticle or field. However, during pellicle manufacturing, the pellicle may be manufactured to a certain standard field size, and the periphery may be coated with protective portion 100%, 80%, etc. accordingly.

[0098]

[0103] In some embodiments, the protective portion 28 may be formed from a material suitable for protecting the portion of the membrane 19 to which it is attached from hydrogen etching. In such embodiments, the protective portion 28 may include a capping material (sometimes referred to as a coating). The capping material may be considered to cover the second portion 38. The capping material may cover only the second portion 38, i.e., not the first portion 36. The coating may be considered to only partially cover the membrane 19. The coating may cover only the non-imaged area of ​​the membrane 19 (i.e., the second area of ​​the second portion 38). The coating is applied only outside the image field. The coating may not cover the imaged area of ​​the membrane 19 (i.e., the first area of ​​the first portion 36). In embodiments, the protective portion 28 may be provided on both sides (all sides) of the membrane 19, i.e., around the first side 30A and the second side 30B (and edge 30C). This may provide enhanced protection compared to when the protective portion 28 is only on the first side surface 30A of the membrane 19.

[0099]

[0104] The capping material may be any of the following materials: carbon nanotubes, graphene, amorphous carbon, low melting point metals (e.g., temperatures below 600°C), molybdenum (Mo), yttrium (Y), yttrium oxide (Y a O b The capping material may include any of the following, alone or in combination: aluminum oxide (Al2O3) (AlO2), hafnium oxide (HfO2), zirconium oxide (ZrO2), ruthenium (Ru), platinum (Pt), gold (Au), zirconium nitride (ZrN), aluminum (Al), zirconium (Zr), silicon (Si), silicon carbide (SiC), silicon oxide (SiOa), boron (B), boron carbide (BC), boron nitride (BN), titanium (Ti), and titanium nitride (TiN). Note that these are merely examples, and other materials may be used. The capping material may include multiple sub-layers formed from different materials.

[0100]

[0105] It will be appreciated that such capping material may be provided at a greater thickness on the protective portion 28 (i.e., on the second portion 38) than on the first portion 36 in the center of the film 19. That is, in some embodiments, there may be some capping material on the first portion 36. In some embodiments, there may be a thicker or thinner coating in the exposed area and a thicker coating at the periphery. Generally, coverage may vary, and gradients may be possible. More generally, in embodiments, the first protective portion may be at or on the first portion, but to a lesser extent than at or on the second portion.

[0101]

[0106] In some embodiments, the protective portion 28 may be formed from the same material as the majority of the membrane 19. In such embodiments, the protective portion 28 may be an increased thickness of the bulk material (e.g., a CNT membrane), which may act as a sacrificial portion that increases the thickness to be etched by hydrogen. In this embodiment, the membrane 19 may be considered to include the protective portion 28, which includes the same material (e.g., carbon nanotubes) as the first portion 36 and the second portion 38.

[0102]

[0107] In some embodiments, membrane 19 may comprise a porous membrane. In some embodiments, membrane 19 comprises nanotubes. For example, membrane 19 may be a woven fabric formed from CNTs, which may be referred to as a carbon nanotube membrane. This is a particularly promising material for use as a pellicle membrane in EUV lithography devices.

[0103]

[0108] The first portion 36 may need to provide >90% EUV transmittance, while the second portion 38 may only need to provide >80% EUV transmittance. Furthermore, the first portion 36 may need to be able to withstand high temperatures (>700°C), while the second portion 38 may only need to be able to withstand low temperatures (>500°C). The frame of the patterning device MA may have structures that need to be visible to metrology sensors, e.g., used for correction, alignment, etc., and therefore the second portion 38 may need to be somewhat transparent to EUV radiation, but not as transparent as the first portion 36. Furthermore, the EUV radiation that may be incident on the second portion 38 may be different from the EUV radiation used for imaging (i.e., the EUV imaging radiation). For example, it may not be of the same high power as the imaging EUV radiation, or it may have a different wavelength and lower dose compared to the EUV imaging radiation, so as not to damage (or destroy) the protective portion 28 (capping material).

[0104]

[0109] Some embodiments of the present disclosure relate to methods of forming a pellicle 15 for use in a lithographic apparatus, such as the lithographic apparatus LA shown in Figure 1. Such a method 100 is shown schematically in Figure 5.

[0105]

[0110] The method 100 includes a step 102 of providing a membrane 19 including a first portion 36 and a second portion 38 .

[0106]

[0111] The method further includes providing a protective portion 28 on a second portion 38 on one or both sides of the membrane 19, which can be done in several different ways as described below.

[0107]

[0112] The protective portion 28 may be applied by additive or subtractive methods, as will be described in more detail below.

[0108]

[0113] In general, the method may include providing a first portion 36 of the patterning device MA that corresponds to a predetermined exposure area 32 (ie, to be used with the pellicle 15).

[0109]

[0114] An important aspect is that the pellicle 15 can be modified (i.e., by providing protective portions 28) at the point of use (e.g., during manufacture of the patterning device MA and / or during manufacture of the substrate W). This allows for the reticle field size associated with the mask (patterning device MA) (e.g., up to 104×132 mm 2 After the desired design (or less than full field size) is identified, pellicle 15 can be selected and processed to the desired design (specific field) size. This processing can be thought of as providing pellicle 15 with protection 28 at second portion 38.

[0110]

[0115] Mask manufacturing may include, for example, qualification of the patterning device by CD measurement, defect inspection, etc., and attachment of a pellicle onto the patterning device, which may include re-qualification of the mask. Substrate (wafer) manufacturing may include, for example, qualification of the patterning device by inspection and / or substrate exposure, etc. Pellicle processing (i.e., selection and processing of the desired design size) may be performed during manufacturing of the substrate W, when a pellicle 15 is attached to the patterning device MA thereat.

[0111]

[0116] In other embodiments, the protection 28 may be provided to the pellicle 15 during the manufacture of the pellicle 15. This may be when the membrane 19 is manufactured and the membrane 19 is attached to the frame 17. The membrane 19 may be manufactured or sourced on the boundary 20.

[0112]

[0117] For additive processes, the protective portion 28 can include a capping material (e.g., formed from a material such as those described above), which may also be referred to as a coating. In some embodiments, the method 100 can include a step 104 of masking the first portion 36 using a masking element. This means that the second portion 38 can be covered with the capping material without covering the first portion 36. The masking element can be a shadow mask. The field size is mask-specific, so the shadow mask is adapted to a selected mask field size. In embodiments, the masking element corresponds to a predetermined exposure area 32 of the patterning device MA (i.e., one to be used with the pellicle 15).

[0113]

[0118] The method 100 can include step 106 of depositing a capping material over the second portion 38 (and the masking element) to cover the second portion 38. As a result, the first portion 36 is masked in step 104, resulting in the protective portion 28 being located on the second portion 38.

[0114]

[0119] The capping material may be deposited using at least one of thermal evaporation, electron beam evaporation, electron beam deposition, pulsed laser deposition, atomic layer deposition, and remote plasma sputtering.

[0115]

[0120] For subtractive processes, the protective portion 28 can include a capping material (e.g., formed from a material such as those described above), sometimes referred to as a coating. This process can include applying the capping material over the first portion 36 and the second portion 38, and then removing the capping material from the first portion 36. Thus, the capping material remains only on the second portion 38 (the cooler area). This results in the protective portion 28 being located on the second portion 38. That is, the film 19 is completely coated, and then a portion of the coating (on the first portion 36) is selectively removed, leaving only a partial coating.

[0116]

[0121] The method may further include laser annealing, laser ablation, reactive ion etching, and / or lift-off of the capping material from the first portion 36. This may involve high temperatures (e.g., at least 500°C, 600°C, or more practically 900°C). It will be understood that these are merely examples and other temperatures may be applicable.

[0117]

[0122] The capping material may be a volatile or thermally unstable material suitable for desorption by EUV radiation (e.g., EUV source power in the range of 200 W to several kW, greater than 200 W, greater than 600 W, or greater than 1 kW). For example, this may be during imaging (e.g., during exposure of the first field in an EUV lithography tool). In embodiments, this may be during the "pre-sweep" because the actual image is printed and requires very stable conditions. Materials such as amorphous carbon (thick layers) or low-melting-point metals (e.g., boron) may be suitable for use as capping materials when using this method, as they exhibit dewetting behavior above a certain temperature, at which the compound desorbs. For example, the temperature at which the compound desorbs may be 500°C, 600°C, 700°C, 800°C, 900°C, or lower or higher, depending on the material.

[0118]

[0123] For subtractive processes, the protective portion 28 may comprise the same material (e.g., carbon nanotubes) as the first portion 36 and the second portion 38. In this case, the film 19 may be considered to comprise the protective portion 28.

[0119]

[0124] The method may include providing a thickness (in the Z direction) to film 19 and then partially removing first portion 36 to reduce the thickness of first portion 36. The thickness of protective portion 28 may be considered to be equal to the thickness removed from first portion 36. That is, after removal, the thickness of first portion 36 is reduced and the thickness of protective portion 28 may be considered to be equal to the thickness removed from first portion 36. Second portion 38 may be considered to include protective portion 28 (i.e., the total thickness of second portion 38 (including protective portion 28) is equal to the thickness of film 19 before the portion of first portion 36 was removed).

[0120]

[0125] The method may include etching the first portion 36 with a hydrogen plasma, for example, an RF plasma etch.

[0121]

[0126] The protective portion 28 may be considered a sacrificial portion, i.e., it increases the thickness that is etched by hydrogen and prevents the second portion 38 from being etched by hydrogen.

[0122]

[0127] Providing the protection 28 only on the second portion 38 outside the imaging area has the advantage that the protection 28 protects the film 19 from plasma etching while not increasing EUV transmission loss in the imaging area. The protection 28 is not necessary in the imaging area because the high-power EUV beam heats the film 19 to a sufficiently high temperature that no or very little (CNT) etching occurs in the imaging area. Outside the imaging area, the film is relatively cool compared to the imaging area, so EUV transmission is not relevant, or at least less important than within the imaging area. By protecting from the plasma, the partial coating on the film 19 (protection 28 on the second portion 38) allows for a longer lifetime for parts of the (CNT) film 19 that are not heated during lithography operations, thereby extending the lifetime of the film 19 as a whole.

[0123]

[0128] Figure 6 shows schematically a cross-sectional view of a pellicle 15 and patterning device MA according to another embodiment. For clarity, the same reference numerals are used for parts that are the same and correspond to those shown in Figure 2, and for the sake of brevity, these parts will not be discussed in further detail.

[0124]

[0129] The pellicle 15 of FIG. 6 differs from the pellicle of FIG. 2 at least in that the protective portion includes multiple shields, namely, a front shield 40 and a back shield 42. Additionally, the pellicle frame 17 includes one or more shield mounting members 44 (e.g., protrusions or studs) attached or attachable to the front shield 40 around its periphery. The shield mounting members 44 may be located at the X-edge of the pellicle 15. The shield mounting members 44 may be aligned with or offset from the mounting members 24 (see FIG. 6). It will be understood that the precise arrangement shown is merely exemplary, and that other suitable arrangements may be used to support the front shield. Thus, more generally, the pellicle frame 17 supports the front shield 40 on the first side 30A (i.e., the front) of the membrane 19. In other embodiments, the shield may be supported by a separate, different component.

[0125]

[0130] Additionally, pellicle frame 17 supports a back shield 42 on a second side 30B (i.e., the back surface) opposite membrane 19. In this embodiment, back shield 42 is attached or attachable to pellicle frame 17 at inner edge 17A of pellicle frame 17. In other embodiments, back shield 42 may be supported by shield mounting member 44, similar to front shield 40. For example, back shield 42 may be disposed between boundary 20 and pellicle frame 17, with the periphery of back shield 42 attached or attachable to shield mounting member 44.

[0126]

[0131] The front shield 40 is supported such that there is a front gap between the first side 30A (i.e., the front) of the membrane 19 and the front shield 40. In embodiments, the front gap may be less than 1000 μm. In other embodiments, the front gap may be less than 2000 μm. Generally, the front gap may be a distance such that plasma flux is sufficiently suppressed. Having a front gap allows for flex space for the membrane 19, and the size of the front gap can be selected to maximize the flex space for the membrane while remaining within the allowable volume available in front of the membrane 19. Additionally, the thickness of the front shield 40 can be selected to be a commercially available thickness (e.g., 200 μm), but can also be selected to be less than (or greater than) 200 μm, for example, if a different sized front gap is desired. As will be appreciated, in some embodiments,

[0127]

[0132] Similarly, the rear shield 42 is supported such that there is a backside gap between the second side 30B (i.e., the backside) of the membrane 19 and the rear shield 42. In embodiments, the backside gap may be less than 1000 μm. The backside gap may be less than 2000 μm. In general, the backside gap may be a distance such that the plasma flux is sufficiently suppressed. In embodiments where a boundary 20 is between the rear shield 42 and the membrane 19, the size of the backside gap may be determined by the thickness of the boundary 20. In other cases, the backside gap may be a similar size to the front gap. The most critical dimension may be the front gap, as there may be little or no tolerance for positioning the shield. Therefore, a thinner shield (<1000 μm) may be preferred. There may be sufficient space between the membrane and the X-direction reticle masking blade, Y-nozzle, and / or EUV inner pod to fit the front shield 40.

[0128]

[0133] It will be appreciated that in some embodiments, there may be substantially no, or at least a very small, front gap between the first side 30A (i.e., the front side) of the membrane 19 and the front shield 40. Similarly, in some embodiments, there may be substantially no, or at least a very small, back gap between the second side 30B (i.e., the back side) of the membrane 19 and the back shield 42. Thus, in some embodiments, the front shield 40 and / or the back shield 42 may be disposed directly on, in contact with, and / or supported by the membrane 19. That is, the front gap and / or the back gap may be optional. This may be the case in embodiments where there is no boundary 20 for the back shield 42 and the membrane 19 is disposed directly on the pellicle frame 17.

[0129]

[0134] It will be understood that although there are front and back gaps between the respective front and back shields 40 and 42 and the membrane 19, the front and back shields can still be considered to be on the front and back sides of the membrane. In other words, a protective portion "on at least one side of the membrane" does not necessarily mean that the protective portion (e.g., shield) is directly on the membrane, in contact with the membrane, or supported by the membrane. Thus, this also covers, for example, a case where the protective portion (e.g., shield) is on the membrane side, separated by a distance (gap) from the membrane, and the protective portion may be supported by another component (e.g., a pellicle frame). Similarly, a protective portion "on a first side and an opposite second side of the membrane" covers, for example, a protective portion (e.g., first shield) on the first side (e.g., front) of the membrane separated by a distance (e.g., front gap) from the membrane, and a protective portion (e.g., second shield) on the opposite second side (e.g., back) of the membrane separated by a distance (e.g., back gap) from the membrane, and the protective portions (e.g., first shield and second shield) are supported by another component (e.g., a pellicle frame).

[0130]

[0135] Both the front shield 40 and the back shield 42 extend inward (parallel to the x-axis) toward the center of the membrane 19 relative to the inner edge 17A of the pellicle frame 17. In embodiments, the front shield 40 and the back shield 42 may extend inward (e.g., in the X-direction) relative to the inner edge 17A of the pellicle frame 17. In some embodiments, the front shield 40 and the back shield 42 may additionally or alternatively extend inward (e.g., at least 1500 μm, e.g., in the X-direction) toward the center of the membrane 19 relative to the inner edge 20A of the boundary 20. For the former option, this may be the case when the inner edge 17A of the pellicle frame 17 and the inner edge 20A of the boundary 20 coincide (align) with each other. In the embodiment of FIG. 6, the front shield 40 and the back shield 42 extend inwardly to the same extent (i.e., the same distance from each other from the pellicle frame 17 (and the same distance from each other from the boundary 20, although the distances to the pellicle frame 17 and the boundary 20 are different and their inner edges 17A, 20A are not aligned with each other)). However, it will be understood that in other embodiments, the front shield 40 and the back shield 42 may extend different distances from the pellicle frame 17 and / or boundary 20. Furthermore, the front shield 40 and the back shield 42 may extend different distances in the X direction (relative to the X boundary) and the Y direction (relative to the Y boundary).

[0131]

[0136] In the embodiment of Figure 2, the first and second portions 36 and 38 of the film 19 correspond to the predetermined exposure and non-exposure regions 32 and 34 of the patterning device MA, respectively. However, in the embodiment of Figure 6, the first portion 36 corresponds to an extended region 46 of the patterning device MA, which is larger than the exposure region 32 of the patterning device MA. The dotted line 35 still separates the exposure region 32 and the non-exposure region 34 of the patterning device MA, and the extended region 46 of the patterning device MA is shown separated by a dotted line 48. It will be understood that the extended region 46 of the patterning device MA includes the exposure region 32 of the patterning device MA and the portion between the dotted lines 35 and 48. The exposure region 32 of the patterning device MA is sometimes referred to as the quality area. Other definitions of the quality area may be used, such as the area where an optical property is measured, the area for inspection capabilities, the area for clamping capabilities, etc.

[0132]

[0137] 6 corresponds to (aligns with) the dotted line 48 separating the extended region 46 of the patterning device MA, rather than the dotted line 35 separating the exposed and non-exposed regions 32, 34 of the patterning device MA. Instead, the portion of the film 19 that may be considered the exposed region (because it is the only portion that receives EUV radiation during imaging) and the portion of the film 19 that may be considered the non-exposed region (because it does not receive EUV radiation during imaging) are separated by the dotted line 49. It will be appreciated that the inner extents of the front shield 40 (i.e., inner edge 40A) and the back shield 42 (i.e., inner edge 42A) correspond to (aligns with) the dotted line 39 separating the first and second portions 36, 38 of the film 19, and correspond to (aligns with) the dotted line 48 of the extended region 46 of the patterning device MA. It will be appreciated that in some embodiments the first and second portions 36, 38 of membrane 19 may be the same as in Figure 2 (i.e. the front and / or back shield extend all the way inward to correspond to the exposure region 32 of the patterning device MA). It is important that the shield does not extend so far that it encroaches on the EUV radiation beam path on the imaging area (e.g. unless the shield is as thin as a pellicle) as this would result in the shield being printed onto the wafer, which is undesirable.

[0133]

[0138] In an embodiment, the extension region 46 of the patterning device MA extends a predetermined distance outward from the exposure region 32 of the patterning device MA. For example, the extension region 46 may extend up to 1000 μm outward from the exposure region 32. This may be to prevent the shields 40, 42 from interfering with the EUV radiation (the EUV light cone).

[0134]

[0139] In embodiments, second portion 38 of membrane 19 extends a predetermined distance (parallel to the x-axis) inward relative to inner edge 17A of pellicle frame 17 (and also extends a predetermined distance (parallel to the x-axis) inward relative to inner edge 20A of boundary 20). In embodiments, inner edge 17A of pellicle frame 17 and inner edge 20A of boundary 20 correspond (align) with each other, and the predetermined distance may be the same. In embodiments, second portion 38 of membrane 19 may extend at least 1500 μm inward relative to inner edge 17A of pellicle frame 17. In embodiments, second portion 38 of membrane 19 may extend at least 1500 μm inward relative to inner edge 20A of boundary 20.

[0135]

[0140] The outer extent of extension region 46 of patterning device MA (i.e., indicated by dotted line 48) is within the black border of patterning device MA. Shields 40, 42 extend (inward) beyond boundary 20 (and frame 17) of pellicle 15, but remain outside the quality area (exposure region 32) of patterning device MA. Because shields 40, 42 extend inward relative to boundary 20 (and frame 17) of pellicle 15, they advantageously protect the pellicle from plasma (i.e., damage from hydrogen plasma etching).

[0136]

[0141] A film (e.g., a CNT film) can be protected from damage by hydrogen plasma etching in the lithography apparatus LA using (periodic) heater pulses. Heat 50 from a pellicle heater (not shown) is shown in FIG. 6 to be incident on a region of the film substantially outside the exposed region of the film 19 (i.e., outside the dotted line 49). Heating the region outside the exposed region of the film 19 is important because it is not heated by EUV radiation during imaging and is therefore more susceptible to hydrogen etching (as explained above). It will be understood that the area covered by heat 50 may differ from that shown in FIG. 6 and may, for example, extend to the boundary 20 or pellicle frame 17, or may extend further to cover part or all of the boundary 20 and pellicle frame 17. Due to the large thermal mass of the boundary 20, it may prove pointless to irradiate the boundary 20.

[0137]

[0142] However, the pellicle heater only heats the thin film 19. The boundary 20 of the pellicle 15 remains relatively cool due to its much thicker body having a higher heat capacity and thermal conductivity. It is recognized, therefore, that there is a finite-sized area of ​​the film 19 near the boundary 20 that cannot be adequately heated by a heating device (e.g., to the extent necessary to satisfactorily mitigate hydrogen etching) because that area is connected to the relatively cool boundary 20. It will be understood that this is also applicable to embodiments in which there is no boundary, i.e., in which the film 19 is formed directly on the frame 17. That is, the frame 17 of the pellicle 15 remains relatively cool due to its thermal mass, and there will be a finite-sized area of ​​the film 19 near the frame 17 that cannot be adequately heated by a heating device (e.g., to the extent necessary to satisfactorily mitigate hydrogen etching) because that area is connected to the relatively cool frame 17.

[0138]

[0143] This area of ​​film 19 near boundary 20 is problematic because the margin between the exposed area of ​​film 19 and boundary 20 is only a few millimeters in the + / -X direction. (The + / -Y direction may be somewhat more tolerant because the distance between the exposed area of ​​film 19 and boundary 20 may be larger in the Y direction than in the X direction, so that the cooler parts of film 19 (closer to boundary 20) are farther away from the plasma and therefore receive less plasma and are less susceptible to etching.) This small distance means that a non-negligible amount of plasma will be received by film 19 on or near boundary 20, which may cause film 19 to break down due to etching damage.

[0139]

[0144] It can be shown that the most etched region on the CNT film is not within the field, but rather outside the exposure area, i.e., under the reticle masking blade. The reticle masking blade is too far from the film to provide any shielding function (in either the X or Y direction), and there is significant leakage of plasma flux under the reticle masking blade (in both the X and Y directions).

[0140]

[0145] The shields 40, 42 protect the pellicle from etching damage by suppressing plasma flux to areas of the film 19 close to the boundary 20. That is, a relatively small gap (front gap and back gap) between the shields 40, 42 and the film 19 prevents a portion of the plasma flux from reaching the problem area. The closer the shields 40, 42 are to the film 19, the more effective they are at preventing plasma diffusion beneath the shields. Furthermore, the shields 40, 42 are transparent to wavelengths of radiation (e.g., IR and / or DUV radiation) from the pellicle heater, which heats the film 19 between the shields 40, 42. The shields 40, 42 may comprise aluminum oxide (Al2O3), sapphire, aluminum oxide (Al2O3)-coated glass, or sapphire-coated glass. Front and back gaps of less than 1000 μm may be sufficient to suppress plasma flux to desirable levels. Furthermore, the shields 40, 42 are inert in the plasma. The shields 40, 42 are irradiated by the intense plasma, which can cause erosion of the shields (detrimental to the function of the shields) and the erosion products can be deposited on the mask (reticle) or other parts of the lithography apparatus LA (detrimental to the function of the lithography apparatus LA). Therefore, all parts (including the shields) in the lithography apparatus LA, especially those close to the light (EUV radiation) beam, must have non-outgassing requirements.

[0141]

[0146] Etch damage to the CNT pellicle after exposure may be evident, such as a ring (also called a "ring of fire") around the most affected (i.e., most etched) exposed area. This "ring of fire" may coincide with the black border of the reticle, making it difficult to image in the lithography apparatus LA. The "ring of fire" exists along the x-axis between the exposed area of ​​the film 19 and the boundary 20 (and frame 17). Therefore, the shields 40, 42 must be positioned to cover the "ring of fire" or the expected location of the "ring of fire." For example, the second portion 38 of the film 19, and thus the shields 40, 42, may extend at least 1500 μm (e.g., in the x-direction) inward relative to the inner edge 17A of the pellicle frame 17 (and / or the inner edge 20A of the boundary 20) to cover the location of the "ring of fire." For example, the "ring of fire" may be located 1000-2000 μm in the X direction and / or 1000-4000 μm in the Y direction from the exposure area 32 (i.e., the defined image field) of the patterning device MA. Accordingly, the second portion 38 of the membrane 19, and thus the shields 40, 42, may extend to cover at least these exemplary locations of the "ring of fire." For example, the first portion 36 of the membrane 19 may correspond to an extension region 46 that extends 1000 μm outward from the predetermined exposure area 32 of the patterning device MA. The extension region 46 may extend outward from the predetermined exposure area 32 of the patterning device MA in at least one of a range of 1000 μm-2000 μm (e.g., in the X direction) and a range of 1000-4000 μm (e.g., in the Y direction). For example, if the "ring of fire" is located 1800 μm in the X direction from the predetermined exposure area 32 of the patterning device MA, the first portion 36 of the film 19 may extend 1700 μm from the predetermined exposure area 32, such that the "ring of fire" is covered by the front shield 40 and / or the back shield 42 (because the second portion 38 of the film 19 extends a corresponding distance).For example, the second portion 38 (and thus the front and / or back shields 40, 42) may extend inwardly (e.g., in the X direction) from the inner edge of the pellicle frame and / or boundary by at least 1300 μm, at least 1500 μm, at least 2300 μm, or in the range of 1300 μm to 2300 μm.

[0142]

[0147] While FIG. 6 shows shields 40, 42 along the X-edge (i.e., extending into the page in the Y-direction and shielding the X-boundary), it will be understood that these shields also extend to the Y-edge (i.e., shielding the Y-boundary). That is, these shields can be considered continuous, and therefore there can be a single front shield and a single back shield. For full-field exposures where the entire available quality area is used, the shields 40, 42 can prevent the appearance of a "ring of fire" at both the X-edge and the Y-edge. In some embodiments, shields may be present only along the X-edge and / or the Y-edge. The front or back shields may not be continuous but may be separated (e.g., there may be shields only along the X-edge). Furthermore, in some embodiments, shields may be present along both the X-edge and the Y-edge, but they may be separated (i.e., not continuous), such as at a corner. In either case, it may be preferable to have shields (e.g., front and / or back shields) on all four edges of the film 19 (i.e., both the X-edge and the Y-edge).

[0143]

[0148] The use of shields 40, 42 can extend the life of pellicles (e.g., CNT pellicles) within the lithography tool LA, at least due to reduced plasma etching effects. Using shields 40, 42 can be advantageous over coating the boundaries and film edges because the coating may not be stable to thermal stress and may require careful alignment of the deposition to the exposure field. Furthermore, the coating may only function to protect the boundaries. Furthermore, using shields 40, 42 can be advantageous over thicker CNT layers outside the exposure area of ​​the reticle because difficult process control may be required to align the thicker boundary layer over the thin film. Furthermore, thicker films closer to the boundaries may still be etched away, which means a shorter lifespan than using shields and increased carbon etch products within the lithography tool LA.

[0144]

[0149] 6 shows two shields, it will be understood that in some embodiments there may be a single shield (i.e., a front shield or a back shield) as this may be sufficient to provide at least some protection and / or prevent etching to the extent required. In the case of a single shield, it may be preferable to use a front shield as the front shield provides more protection than the back shield.

[0145]

[0150] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it will be appreciated that the lithographic apparatus described herein have other possible applications, such as in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0146]

[0151] Although specific reference is made herein to embodiments of the invention in relation to lithography apparatus, embodiments of the invention may also 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 objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatus are sometimes referred to generically as lithography tools. Such lithography tools may use vacuum or ambient (non-vacuum) conditions.

[0147]

[0152] Although specific reference has been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention is not limited to optical lithography and may be used in other applications, for example imprint lithography, where circumstances permit.

[0148]

[0153] Where circumstances permit, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium that 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 disk storage media, optical storage media, flash memory devices, or electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.). Also, firmware, software, routines, or instructions may be described herein as performing certain actions. However, it should be understood that such description is for convenience only, and that such actions are in fact due to computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc., and that in doing so, actuators or other devices may interact with the physical world.

[0149]

[0154] While specific embodiments of the present invention have been described above, it will be apparent that the present invention may be practiced otherwise than as described. The foregoing description is intended to be illustrative and not limiting. Accordingly, it will be apparent to those skilled in the art that modifications may be made to the invention as described without departing from the scope and provisions of the following claims. 1. A pellicle for use in a lithographic apparatus, the pellicle comprising: a membrane comprising a first portion and a second portion; a protective portion in a second portion on at least one side of the membrane; A pellicle comprising: 2. A pellicle as described in clause 1, wherein the second portion, in use, is not subjected to EUV imaging radiation or is subjected to only a portion of the EUV imaging radiation received by the first portion. 3. A pellicle according to clause 1 or 2, wherein the first portion substantially corresponds to a predetermined exposure area of ​​a patterning device for use with the pellicle. 4. A pellicle according to clause 3, wherein the first portion is substantially the same size as a predetermined exposure area of ​​the patterning device. 5. A pellicle according to any one of clauses 1 to 4, wherein the second portion is at the periphery of the membrane. 6. A pellicle as described in clause 5, wherein the pellicle comprises a boundary at the periphery of the membrane, and the second portion coincides with the boundary. 7. A pellicle according to any one of clauses 1 to 6, wherein the protective portion comprises a material suitable for protecting the second portion of the membrane from hydrogen etching. 8. A pellicle according to any one of clauses 1 to 7, wherein the protective portion is on at least one of the first side and the opposite second side of the membrane and the edge of the membrane. 9. A pellicle according to any one of clauses 1 to 8, wherein the protective portion includes a capping material covering the second portion. 10. Capping materials include carbon nanotubes, graphene, amorphous carbon, (low melting point metals), molybdenum (Mo), yttrium (Y), yttrium oxide (Y a O b), aluminum oxide (Al2O3) (AlO2), hafnium oxide (HfO2), zirconium oxide (ZrO2), ruthenium (Ru), platinum (Pt), gold (Au), zirconium nitride (ZrN), aluminum (Al), zirconium (Zr), silicon (Si), silicon carbide (SiC), silicon oxide (SiO a 10. The pellicle of clause 9, comprising at least one of SiO2 (SiO4), boron (B), boron carbide (BC), boron nitride (BN), titanium (Ti), and titanium nitride (TiN). 11. A pellicle according to any one of clauses 1 to 8, wherein the membrane comprises a protective portion, the protective portion comprising the same material as the first and second portions. 12. A pellicle as described in any one of clauses 1 to 8, wherein the pellicle includes a pellicle frame, the protective portion includes a shield, and the shield is supported by the pellicle frame. 13. A pellicle according to clause 12, wherein the shield is separated from the membrane by a gap, preferably the gap is less than 1000 μm or less than 2000 μm. 14. A pellicle according to clause 12 or 13, wherein the shield is at least one of substantially transparent to heater radiation, substantially transparent to IR radiation, substantially transparent to DUV radiation, and inert in the plasma. 15. The pellicle of clause 14, wherein the shield comprises at least one of aluminum oxide (Al2O3), sapphire, aluminum oxide (Al2O3) coated glass, and sapphire coated glass. 16. A pellicle according to any one of clauses 12 to 15, wherein the protective portion includes a plurality of shields, a first shield on a first side of the membrane and a second shield on a second opposite side of the membrane. 17. A pellicle as described in any of clauses 1-2 and clauses 5-16 when not subject to clauses 3 and 4, wherein the first portion substantially corresponds to an extended area that is larger than the predetermined exposure area of ​​a patterning device for use with the pellicle. 18. A pellicle according to clause 17, wherein the extended region extends a predetermined distance outward from the predetermined exposure region of the patterning device. 19. A pellicle according to clause 18, wherein the extended region extends outward from the predetermined exposure area of ​​the patterning device by at least one of 1000 μm, a range of 1000-2000 μm, and a range of 1000-4000 μm. 20. A pellicle according to any of clauses 1-19, wherein the second portion extends a predetermined distance inward relative to the inner edge of the pellicle frame and / or boundary at the periphery of the membrane. 21. A pellicle as described in clause 20, wherein the second portion extends inward relative to the inner edge and / or boundary of the pellicle frame by at least one of at least 1300 μm, at least 1500 μm, at least 2300 μm, and in the range of 1300 μm to 2300 μm. 22. A pellicle according to any one of clauses 1 to 21, wherein the membrane comprises carbon nanotubes. 23. A lithographic apparatus operable to form an image of a patterning device on a substrate using a radiation beam, the lithographic apparatus comprising a pellicle positioned in the path of the radiation beam, the pellicle being as defined in any of clauses 1 to 22. 24. A method of forming a pellicle for use in a lithographic apparatus, the method comprising: providing a membrane comprising a first portion and a second portion; providing a protective portion on a second portion of at least one side of the membrane; A method comprising: 25. The method of clause 24, further comprising providing the protective portion using an additive or subtractive process. 26. Providing a protective portion using an additive process, the protective portion including a capping material; depositing a capping material over the second portion to cover the second portion; 26. The method of clause 25, further comprising: 27. The method of clause 26, further comprising masking the first portion using a masking element. 28. The method of clause 27, wherein the masking element substantially corresponds to a predetermined exposure area of ​​a patterning device for use with the pellicle. 29. The method of any of clauses 26-28, further comprising depositing the capping material using at least one of thermal evaporation, electron beam evaporation, electron beam deposition, pulsed laser deposition, atomic layer deposition, and remote plasma sputtering. 30. Providing a protective portion using a subtractive method, the protective portion including a capping material; applying a capping material over the first portion and the second portion; removing the capping material from the first portion; 26. The method of clause 25, further comprising: 31. The method of clause 30, wherein the method further comprises removing the capping material from the first portion using at least one of laser annealing, laser ablation, reactive ion etching, and lift-off. 32. The method of clause 30 or 31, wherein the capping material is a volatile or thermally unstable material that is desorbed by EUV radiation. 33. The method of clause 25, further comprising providing the protective portion using a subtractive process comprising providing a thickness to the membrane and partially removing the first portion to reduce the thickness of the first portion, wherein the membrane comprises the protective portion, and the protective portion comprises the same material as the first portion and the second portion. 34. The method of clause 33, further comprising etching the first portion with a hydrogen plasma. 35. The method of any of clauses 24-34, further comprising providing protection to at least one of the first and second opposite sides of the membrane and an edge of the membrane. 36. The method of any of clauses 24-35, further comprising providing a first portion to substantially correspond to a predetermined exposure area of ​​a patterning device for use with a pellicle. 37. The method of any of clauses 24-36, further comprising providing protection during at least one of pellicle fabrication, patterning device fabrication, and substrate fabrication. 38. The method of clause 24, further comprising providing a pellicle frame, wherein the protective portion includes a shield, and wherein the pellicle frame supports the shield. 39. The method of clause 38, further comprising separating the shield from the membrane by a gap. 40. The method of clause 38 or 39, further comprising providing a plurality of shields, such as a first shield on a first side of the membrane and a second shield on an opposite second side of the membrane. 41. The method of any of clauses 38-40, further comprising providing a first portion to substantially correspond to an extended area that is larger than a predetermined exposure area of ​​a patterning device for use with a pellicle. 42. A pellicle for use in a lithography apparatus, the pellicle comprising: a membrane comprising a first portion and a second portion; a protective portion in a second portion on at least one side of the membrane; A pellicle comprising: 43. A pellicle according to clause 42, wherein the second portion, in use, is not subjected to EUV imaging radiation or is subjected to only a portion of the EUV imaging radiation received by the first portion. 44. A pellicle according to clause 42 or 43, wherein the first portion substantially corresponds to a predetermined exposure area of ​​a patterning device for use with the pellicle. 45. The pellicle of clause 44, wherein the first portion is substantially the same size as a predetermined exposure area of ​​the patterning device. 46. ​​A pellicle according to any one of clauses 1 to 45, wherein the second portion is at the periphery of the membrane. 47. A pellicle according to clause 46, wherein the pellicle comprises a boundary at the periphery of the membrane, and the second portion coincides with the boundary. 48. A pellicle according to any one of clauses 1 to 47, wherein the protective portion comprises a material suitable for protecting the second portion of the membrane from hydrogen etching. 49. A pellicle according to any one of clauses 1 to 48, wherein the protective portion is on at least one of the first side and the opposite second side of the membrane and the edge of the membrane. 50. A pellicle according to any one of clauses 1 to 49, wherein the protective portion includes a capping material covering the second portion. 51. Capping materials include carbon nanotubes, graphene, amorphous carbon, (low melting point metals), molybdenum (Mo), yttrium (Y), yttrium oxide (Y a O b ), aluminum oxide (Al2O3) (AlO2), hafnium oxide (HfO2), zirconium oxide (ZrO2), ruthenium (Ru), platinum (Pt), gold (Au), zirconium nitride (ZrN), aluminum (Al), zirconium (Zr), silicon (Si), silicon carbide (SiC), silicon oxide (SiO a 51. The pellicle of clause 50, comprising at least one of SiO2 (SiO4), boron (B), boron carbide (BC), boron nitride (BN), titanium (Ti), and titanium nitride (TiN). 52. A pellicle according to any one of clauses 42 to 49, wherein the membrane includes a protective portion, the protective portion comprising the same material as the first and second portions. 53. A pellicle according to any one of clauses 1 to 52, wherein the membrane comprises carbon nanotubes. 54. A lithographic apparatus operable to form an image of a patterning device on a substrate using a radiation beam, the lithographic apparatus comprising a pellicle positioned in a path of the radiation beam, the pellicle being as defined in any of clauses 1 to 53. 55. A method of forming a pellicle for use in a lithographic apparatus, the method comprising: providing a membrane comprising a first portion and a second portion; providing a protective portion on a second portion of at least one side of the membrane; A method comprising: 56. The method of clause 55, further comprising providing the protective portion using an additive or subtractive process. 57. Providing a protective portion using an additive process, the protective portion including a capping material; depositing a capping material over the second portion to cover the second portion; 57. The method of clause 56, further comprising: 58. The method of clause 57, further comprising masking the first portion using a masking element. 59. The method of clause 58, wherein the masking element substantially corresponds to a predetermined exposure area of ​​a patterning device for use with the pellicle. 60. The method of any of clauses 57-59, further comprising depositing the capping material using at least one of thermal evaporation, electron beam evaporation, electron beam deposition, pulsed laser deposition, atomic layer deposition, and remote plasma sputtering. 61. Providing a protective portion using a subtractive method, the protective portion including a capping material; applying a capping material over the first portion and the second portion; removing the capping material from the first portion; 57. The method of clause 56, further comprising: 62. The method of clause 61, wherein the method further comprises removing the capping material from the first portion using at least one of laser annealing, laser ablation, reactive ion etching, and lift-off. 63. The method of clause 61 or 62, wherein the capping material is a volatile or thermally unstable material that is desorbed by EUV radiation. 64. The method of clause 56, further comprising providing the protective portion using a subtractive process comprising providing a thickness to the membrane and partially removing the first portion to reduce the thickness of the first portion, wherein the membrane comprises the protective portion, and the protective portion comprises the same material as the first portion and the second portion. 65. The method of clause 64, further comprising etching the first portion with a hydrogen plasma. 66. The method of any of clauses 55-65, further comprising providing protection to at least one of the first and second opposite sides of the membrane and an edge of the membrane. 67. The method of any of clauses 55-66, further comprising providing a first portion to substantially correspond to a predetermined exposure area of ​​a patterning device for use with a pellicle. 68. The method of any of clauses 55-67, further comprising providing protection during at least one of pellicle fabrication, patterning device fabrication, and substrate fabrication.

Claims

1. 1. A pellicle for use in a lithographic apparatus, said pellicle comprising: a membrane comprising carbon nanotubes, the membrane comprising a first portion and a second portion; a protective portion in the second portion on at least one side of the membrane; Equipped with The protective portion comprises a material suitable for protecting the second portion of the membrane from etching.

2. 2. The pellicle of claim 1, wherein the second portion, in use, receives no EUV imaging radiation or only a portion of the EUV imaging radiation received by the first portion.

3. 3. The pellicle of claim 1, wherein the first portion substantially corresponds to a predetermined exposure area of ​​a patterning device for use with the pellicle.

4. The pellicle of claim 3 , wherein the first portion is substantially the same size as the predetermined exposure area of ​​the patterning device.

5. The pellicle of any one of claims 1 to 4, wherein the second portion is located at the periphery of the membrane.

6. 6. The pellicle of claim 5, wherein the pellicle comprises a boundary around the periphery of the membrane, the second portion being sized to match the boundary, and the boundary being located on the membrane opposite the protective portion.

7. The pellicle of any one of claims 1 to 6, wherein the protective portion comprises a material suitable for protecting the second portion of the membrane from hydrogen etching.

8. The pellicle according to any one of claims 1 to 7, wherein the protective portion is on at least one of a first side surface and an opposite second side surface of the film, and an edge of the film.

9. The pellicle according to any one of claims 1 to 8, wherein the protective portion includes a capping material that covers the second portion.

10. The capping material may be carbon nanotubes, graphene, amorphous carbon, (low melting point metal), molybdenum (Mo), yttrium (Y), yttrium oxide (Y), or the like. ａ O ｂ ), aluminum oxide (Al ２ O ３ ) (AlO ２ ), hafnium oxide (HfO ２ ), zirconium oxide (ZrO ２ ), ruthenium (Ru), platinum (Pt), gold (Au), zirconium nitride (ZrN), aluminum (Al), zirconium (Zr), silicon (Si), silicon carbide (SiC), silicon oxide (SiO ａ ), boron (B), boron carbide (B ４ 10. The pellicle of claim 9, comprising at least one of: C), boron nitride (BN), titanium (Ti), and titanium nitride (TiN).

11. The pellicle according to any one of claims 1 to 8, wherein the membrane includes the protective portion, and the protective portion includes the same material as the first portion and the second portion.

12. A pellicle as described in any one of claims 1 to 11, wherein the membrane comprises a layer having the same type of carbon nanotubes in both the first portion and the second portion, and the material of the protective portion covering the second portion of the membrane is transparent to at least a portion of the EUV imaging radiation received by the first portion.

13. 13. A lithographic apparatus operable to form an image of a patterning device on a substrate using a radiation beam, the lithographic apparatus comprising a pellicle positioned in a path of the radiation beam, the pellicle being according to any one of claims 1 to 12.

14. 1. A method of forming a pellicle for use in a lithographic apparatus, the method comprising: providing a film comprising carbon nanotubes, the film comprising a first portion and a second portion; providing a protection to the second portion on at least one side of the membrane; wherein the protective portion comprises a material suitable for protecting the second portion of the membrane from etching.

15. 15. The method of claim 14, further comprising providing the protective portion using an additive or subtractive process.

16. providing the protective portion using the additive process, the protective portion comprising a capping material; depositing the capping material over the second portion to cover the second portion; 16. The method of claim 15, further comprising:

17. The method of claim 16 , further comprising masking the first portion using a masking element.

18. 20. The method of claim 17, wherein the masking element substantially corresponds to a predetermined exposure area of ​​a patterning device for use with a pellicle.

19. 19. The method of any of claims 16 to 18, further comprising depositing the capping material using at least one of thermal evaporation, e-beam evaporation, e-beam deposition, pulsed laser deposition, atomic layer deposition, and remote plasma sputtering.

20. providing the protective portion using a subtractive process, the protective portion comprising a capping material; applying the capping material over the first portion and the second portion; removing the capping material from the first portion; 16. The method of claim 15, further comprising:

21. 21. The method of claim 20, wherein the method further comprises removing the capping material from the first portion using at least one of laser annealing, laser ablation, reactive ion etching, and lift-off.

22. 22. The method of claim 20 or 21, wherein the capping material is a volatile or thermally unstable material that is desorbed by EUV radiation.

23. 16. The method of claim 15, further comprising providing the protective portion using a subtractive method including providing a thickness to the film and partially removing the first portion to reduce a thickness of the first portion, wherein the film includes the protective portion, and the protective portion comprises the same material as the first portion and the second portion.

24. 24. The method of claim 23, further comprising etching the first portion with a hydrogen plasma.

25. a first side and an opposite second side of the membrane; an edge of the membrane; The method of any of claims 14 to 24, further comprising providing said protection to at least one of:

26. The method of any of claims 14 to 25, further comprising providing the first portion to substantially correspond to a predetermined exposure area of ​​a patterning device for use with the pellicle.

27. The method of any of claims 14 to 26, further comprising providing said protection during at least one of a manufacturing of said pellicle, a manufacturing of a patterning device, and a manufacturing of a substrate.

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