WO2025201833A1

WO2025201833A1 - Film, film assembly, and lithographic apparatus

Info

Publication number: WO2025201833A1
Application number: PCT/EP2025/056171
Authority: WO
Inventors: Marcus Adrianus Van De Kerkhof
Original assignee: ASML Netherlands BV
Current assignee: ASML Netherlands BV
Priority date: 2024-03-28
Filing date: 2025-03-06
Publication date: 2025-10-02
Anticipated expiration: 2026-09-28

Abstract

Disclosed herein is a film for a lithographic apparatus, the film comprising a plurality of nanotubes, wherein the plurality of nanotubes comprises silicon-based nanotubes for filtering undesired radiation. Further disclosed is a film assembly comprising such a film and a structure configured to support the film. Also disclosed is a method of manufacturing the film comprising fabricating a plurality of nanotubes and arranging the nanotubes to form the film.

Description

FILM, FILM ASSEMBLY, AND LITHOGRAPHIC APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 24167525.5 which was filed on March 28, 2024 and EP application 24197628.1 which was filed on August 30, 2024 which is incorporated herein in its entirety by reference.

FIELD

[0002] The present invention relates to a film, a film assembly, a lithographic component comprising the film or the film assembly, a lithographic apparatus comprising the lithographic component, and method of manufacturing the film.

BACKGROUND

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

[0004] To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which can be formed on the substrate. A lithographic apparatus, which uses extreme ultraviolet (EUV) radiation, having a wavelength within the range 4-20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm.

[0005] In a lithographic apparatus such as this, it is desirable that the EUV radiation is readily transmitted to the substrate for effective and efficient formation of features on the substrate. However, radiation outside the desired, EUV, wavelength range may also be projected towards the substrate from the projection system of the lithographic apparatus. Certain wavelengths of radiation may be undesired, for example due to their potential to cause harm to the substrate or interfere with the formation of features on the substrate by the EUV radiation. For this reason, it can be desirable to provide a spectral filter within the lithographic apparatus to suppress transmission of undesired wavelengths of radiation towards the substrate, while allowing transmission of the desired, EUV, wavelengths of radiation.

[0006] A spectral filter membrane, sometimes referred to as a dynamic gas lock (DGL) membrane, can be provided to perform the spectral filtering function in the lithographic apparatus. However, the spectral filter membrane is sensitive to uncontrollable events like dropping micro-particles and small pressure differences between the compartment housing the projection system and the compartment housing the substrate table. Such events, which may occur within a lithographic apparatus, can cause the spectral filter membrane to fail. [0007] The thickness of the spectral filter membrane may be in the order of 10 to 20 nm. Furthermore, the spectral filter membrane is commonly pre-stressed to avoid wrinkling and fatigue during EUV exposure cycles. However, due to the pre-stressed nature of the spectral filter membrane, the spectral filter can fail in an undesirable manner. In particular, failure of the spectral filter membrane can cause small fragments of the spectral filter membrane to be blown across the interior of the lithographic apparatus. In particular, due to pressure differences within the lithographic apparatus, it is most likely for fragments of the failed spectral filter membrane to be blown into the projection system of the lithographic apparatus. These fragments can cause contamination of optical components of the projection system. This contamination may have an undesirable influence on the performance of the optical components, may cause them to suffer localised overheating and/or may cause them to become damaged.

[0008] Replacing a failed spectral filter membrane, cleaning any contaminated components, and/or fixing any damaged components may be associated with significant cost and extended periods of downtime of the lithographic apparatus.

[0009] It is therefore desirable to provide a means of spectral filtering which is effective at transmitting desired wavelengths of radiation and suppressing undesired wavelengths of radiation, while also being more robust. In particular, there is a desire to provide a means of spectral filtering which is less prone to failure the environment of the lithographic apparatus, and/or which fails in a less damaging manner which is less likely to result in contamination of other components of the lithographic apparatus. Such a means of spectral filtering may then be beneficial for use in other applications beyond that of lithography.

SUMMARY

[00010] The present invention is directed to providing a film, a film assembly, a lithographic component comprising the film or the film assembly, a lithographic apparatus comprising the lithographic component, and method of manufacturing the film.

[00011] According to an aspect of the invention, there is provided a film for a lithographic apparatus. The film comprising a plurality of nanotubes. The plurality of nanotubes comprises silicon-based nanotubes for filtering undesired radiation.

[00012] According to another aspect of the invention, there is provided a film for a lithographic apparatus. The film comprising a plurality of nanotubes. The plurality of nanotubes comprises carbonbased nanotubes coated with a silicon-based cap layer for filtering undesired radiation.

[00013] According to another aspect of the invention, there is provided a film assembly comprising the film described above and a structure configured to support the film.

[00014] According to another aspect of the invention, there is provided a lithographic component for a lithographic apparatus. The lithographic component comprising the film described above or the film assembly described above. [00015] According to another aspect of the invention, there is provided a lithographic apparatus comprising the lithographic component described above.

[00016] According to another aspect of the invention, there is provided a method of manufacturing the film described above.

[00017] According to another aspect of the invention, there is provided a method of manufacturing the film assembly described above.

[00018] Further embodiments, features and advantages of the present invention, as well as the structure and operation of the various embodiments, features and advantages of the present invention are described in detail below with reference to the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[00019] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

Figure 1 depicts a lithographic system comprising a lithographic apparatus and a radiation source;

Figure 2A and B depict a plan view of a film assembly comprising a film and a support structure, and a cross-sectional view of the same film assembly;

Figure 3 depicts a cross-sectional view of a nanotube;

Figure 4A-C depict films having an irregular mesh structure comprising nanotubes of respective diameters;

Figure 5 depicts a cross-sectional view of a nanotube having a cap layer;

Figure 6 depicts a film comprising outer layers of carbon nanotubes and a layer of silicon nanotubes disposed therebetween.

[00020] The features shown in the Figures are not necessarily to scale, and the size and/or arrangement depicted is not limiting. It will be understood that the Figures include optional features which may not be essential to the invention. Furthermore, not all of the features of the apparatus are depicted in each of the figures, and the Figures may only show some of the components relevant for describing a particular feature.

DETAILED DESCRIPTION

[00021] Figure 1 shows a lithographic system comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and to supply the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS and a substrate table WT configured to support a substrate W.

[00022] The illumination system IL is configured to condition the EUV radiation beam B before the EUV radiation beam B is incident upon the patterning device MA. Thereto, the illumination system IL may include a facetted field mirror device 10 and a facetted pupil mirror device 11. The faceted field mirror device 10 and faceted pupil mirror device 11 together provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The illumination system IL may include other mirrors or devices in addition to, or instead of, the faceted field mirror device 10 and faceted pupil mirror device 11.

[00023] After being thus conditioned, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B’ is generated. The projection system PS is configured to project the patterned EUV radiation beam B’ onto the substrate W. For that purpose, the projection system PS may comprise a plurality of mirrors 13,14 which are configured to project the patterned EUV radiation beam B’ onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B’, thus forming an image with features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is illustrated as having only two mirrors 13,14 in Figure 1, the projection system PS may include a different number of mirrors (e.g. six or eight mirrors).

[00024] The substrate W may include previously formed patterns. Where this is the case, the lithographic apparatus LA aligns the image, formed by the patterned EUV radiation beam B’, with a pattern previously formed on the substrate W.

[00025] A relative vacuum, i.e. a small amount of gas (e.g. hydrogen) at a pressure well below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL, and/or in the projection system PS.

[00026] The radiation source SO may be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL) or any other radiation source that is capable of generating EUV radiation.

[00027] In a lithographic apparatus, for example that of Figure 1 as described above, it is desirable that the EUV radiation is readily transmitted to the substrate for effective and efficient formation of features on the substrate. However, radiation outside the desired, EUV, wavelength range may also be projected towards the substrate from the projection system of the lithographic apparatus. Certain wavelength ranges of radiation may be undesired, for example due to their potential to cause harm to the substrate or interfere with the formation of features on the substrate by the EUV radiation. For this reason, it can be desirable to provide a spectral filter within the lithographic apparatus to suppress transmission of undesired wavelengths of radiation towards the substrate, while allowing transmission of the desired, EUV, wavelengths of radiation.

[00028] A spectral filter membrane, sometimes referred to as a dynamic gas lock (DGL) membrane, can be provided to perform the spectral filtering function in the lithographic apparatus. However, the spectral filter membrane is sensitive to uncontrollable events like dropping micro-particles and small pressure differences between the compartment housing the projection system PS and the compartment housing of the substrate table WT. Such events, which may occur within a lithographic apparatus, can cause the spectral filter membrane to fail.

[00029] The thickness of the spectral filter membrane may be in the order of from 5 to 40 nm, preferably from 8 to 30 nm, more preferably fromlO to 20 nm. Furthermore, the spectral filter membrane is commonly pre-stressed to avoid wrinkling and fatigue during EUV exposure cycles. However, due to the pre-stressed nature of the spectral filter membrane, the spectral filter membrane can fail in an undesirable manner. In particular, failure of the spectral filter membrane can cause small fragments of the spectral filter membrane to be blown across the interior of the lithographic apparatus. In particular, due to pressure differences within the lithographic apparatus, it is most likely for fragments of the failed spectral filter membrane to be blown into the projection system of the lithographic apparatus. These fragments can cause contamination of optical components of the projection system. This contamination may have an undesirable influence on the performance of the optical components, may cause them to suffer localised overheating and/or may cause them to become damaged.

[00030] Replacing a failed spectral filter membrane, cleaning any contaminated components, and/or fixing any damaged components may be associated with significant cost and extended periods of downtime of the lithographic apparatus.

[00031] It is therefore desirable to provide a means of spectral filtering which is effective at transmitting desired wavelengths of radiation and suppressing undesired wavelengths of radiation, while also being more robust. In particular, there is a desire to provide a means of spectral filtering which is less prone to failure the environment of the lithographic apparatus, and/or which fails in a less damaging manner which is less likely to result in contamination of other components of the lithographic apparatus. In particular, it is desirable the means of spectral filtering is not pre-stressed, as pre-stressing the filter results in a higher risk of the filter failing in a manner resulting in the expulsion of many fragments.

[00032] A more robust means of spectral filtering may then be beneficial for use in other applications beyond that of lithography.

[00033] Figures 2A and 2B show a film assembly comprising a film 1000 and a structure 500 configured to support the film 1000. Figure 2A provides a plan view and Figure 2B provides a cross- sectional view, through line A-A as shown in Figure 2A.

[00034] The film 1000 is suitable for use in a lithographic apparatus, such as described above with reference to Figure 1. The film 1000 comprises a plurality of nanotubes. According to one arrangement, the plurality of nanotubes comprises silicon-based nanotubes. Alternatively, or additionally, the plurality of nanotubes may comprise carbon-based nanotubes coated with a silicon-based cap layer. The silicon-based cap layer may consist of silicon. Carbon-based nanotubes are predominantly comprised of carbon and may consist only of carbon. Similarly, silicon-based nanotubes are predominantly comprised of silicon and may consist only of silicon. [00035] Such a film, which is composed predominantly or entirely of carbon-based and/or silicon- based nanotubes, is a porous material. Therefore, the film has potential to provide very high EUV transmission. Furthermore, the film may also desirably provide very good mechanical stability and can therefore be manufactured at small thicknesses, whilst remaining robust against mechanical failure.

[00036] In some embodiments, the film 1000 may transparent for at least 70% of EUV radiation, desirably at least 80% EUV radiation, more desirably at least 90% EUV radiation. In other words, the film 1000 may enable transmission of EUV radiation through the film 1000. In a lithographic apparatus, this may enable the desired EUV radiation to be transmitted towards the substrate.

[00037] The film 1000 is suitable for filtering undesired radiation in the lithographic apparatus. For example, in some lithographic apparatus applications, deep ultraviolet (DUV) radiation, may be undesirable. In other words, there may be a desire to suppress DUV radiation, where DUV radiation has wavelengths within the range of 100 nm to 300 nm. In some applications, it may undesired radiation may be radiation of a different wavelength. For example, infrared (IR) radiation, which has wavelengths within the range 750 nm and 1 mm may be undesired radiation.

[00038] In some embodiments, the film 1000 may be configured to filter out at least 70% of DUV radiation, desirably at least 80% DUV radiation, more desirably at least 90% DUV radiation. In other words, the film 1000 may prevent the majority of DUV radiation from being transmitted through the film 1000. In a lithographic apparatus, this may prevent the majority of undesired DUV radiation from being transmitted towards the substrate.

[00039] Figure 3 provides a cross-sectional view of a nanotube 10. In the film 100, the majority of the nanotubes 10 desirably have a diameter within a preferred diameter range. The preferred diameter range may be between 5 nm and 30 nm, desirably between 10 nm and 30 nm, more desirably 15 to 25 nm, yet more desirably 20 nm. Desirably, at least 65% of the nanotubes in the film have a diameter within the preferred diameter range. More desirably at least 80% of the nanotubes in the film have a diameter within the preferred diameter range.

[00040] The film may be manufactured by fabricating a plurality of nanotubes and arranging the nanotubes to form the film 100. As shown in the arrangements of Figures 4A-C, the nanotubes may be arranged to form a mesh. In other words, the film may comprise a plurality of nanotubes which are disposed to overlap each other to form an entangled collection of nanotubes. The mesh may have an irregular structure, such as the mesh structures shown in Figures 4A-C. For example, the nanotubes may be interlaced to form an interconnected structure composed of discrete nanotubes. Furthermore, the orientation of the nanotubes within the mesh may be random.

[00041] In the mesh 101 of Figure 4A, each nanotube 10 has a diameter of approximately 10 nm. In the mesh 102 of Figure 4B, each nanotube 10 has a diameter of approximately 20 nm. In the mesh 103 of Figure 4C, each nanotube 10 has a diameter of approximately 30 nm. The density of nanotubes, or number of nanotubes within a given volume, may be greater in the mesh 101 of Figure 4A than in the mesh 103 of Figure 4C. In other words, thinner nanotubes may be more densely arranged than thicker nanotubes. A thickness of nanotubes and density of the mesh of nanotubes may be selected based on the desired properties of the film 1000 which may depend on the application.

[00042] The film 1000 optionally comprises a plurality of nanotubes coated with a cap layer. In this way, the material of the nanotube and of the cap layer may be selected to provide complimentary properties. The cap layer may comprise any of the following materials either alone or in combination: yttrium (Y), yttrium oxide (Y_aOb), aluminium oxide (AI2O3), hafnium oxide (HfOz), zirconium oxide (ZrCh), ruthenium (Ru), platinum (Pt), gold (Au), zirconium nitride (ZrN), aluminium (Al) or zirconium (Zr). The material of the cap layer may comprise a plurality of sublayers formed from different materials.

[00043] In some arrangements, the cap layer may be of a material with properties enabling transmission of a desirable radiation and/or suppression of an undesirable radiation. In this way, the cap layer may aid the film in providing the desired filtering function. For example, the cap layer may comprise, or consist of, a metal or semimetal. For example, the cap layer optionally comprises, or consists of, one or more of comprises one or more of: aluminium, zirconium, yttrium, niobium, ruthenium or molybdenum. In a preferred arrangement, the cap layer may comprise, or consist of, silicon. For example, the cap layer may comprise or consist of polycrystalline silicon. The cap layer optionally comprises a compound comprising silicon. The compound may optionally comprise one or more of: a metal and oxygen. The cap layer optionally comprises silicon oxynitride. For example, the cap layer may comprise a silicon oxide (SiO) a silicon nitride (SiN) or an SiNO, wherein each of these may be provided in any ratio of component elements, for example the silicon oxide may be silicon dioxide. In a preferred arrangement, the cap layer comprise a yttrium silicate (YSiO). Silicon has properties enabling suppression of deep ultraviolet radiation and transmission of extreme ultraviolet radiation. As such, the use of silicon-based nanotubes and/or a silicon-based cap layer may be desirable in applications, such as lithographic apparatus, where suppression of deep ultraviolet radiation and transmission of extreme ultraviolet radiation is desirable.

[00044] Additionally, or alternatively, the cap layer may be of a material with properties intended to provide strength and resistance to wear. In this way the useful life of the film may be extended, which may desirably reduce the cost and downtime associated with frequent replacement of the film. The cap layer may comprise, or consist of, carbon. For example, the cap layer may comprise or consist of amorphous carbon. Carbon has properties enabling greater thermal and mechanical resistance than silicon. In other words, carbon may be able to withstand mechanical and thermal loads longer than silicon. As such, the use of carbon-based nanotubes and/or a carbon-based cap layer may be desirable in applications having potentially harsh mechanical and/or thermal environments.

[00045] In a preferred embodiment, the film may comprise a combination of carbon and a metal or semimetal, such as silicon. In this way, the metal or semimetal may be selected based on the desired radiation transmission and suppression properties. Carbon may be provided to aid the film in withstanding the thermal and mechanical loads provided in the given application. For example, the film 1000 may comprise carbon-based nanotubes coated with a metal-based or semimetal-based cap layer, such as a silicon cap layer 11. Alternatively, or additionally, the film 1000 may comprise silicon-based nanotubes coated with a carbon cap layer 11. It may be preferable to have a carbon-based cap layer such that the outer layer, which is most directly exposed to the environment and associated mechanical and thermal loads, is resilient.

[00046] Figure 5 provides a cross-sectional view through a nanotube 10 individually coated with a cap layer 11. In one arrangement, the at least some of the nanotubes 10 of the film 1000 may be individually coated with the cap layer 11, as shown in Figure 5. The cap layer 11, such as that of Figure 5, on an individual nanotube may have a thickness of between 0.3 nm and 3 nm, desirably the thickness may be between 0.5 and 2 nm, more desirably the thickness may be 1 nm.

[00047] Additionally, or alternatively, at least some of the nanotubes, optionally all of the nanotubes, may be collectively coated with a cap layer. A cap layer collectively coating a plurality of nanotubes is referred to herein as a protective cap layer. In other words, a protective cap layer may be provided to surround an exterior of a plurality of nanotubes. For example, in one arrangement all of the nanotubes may be collectively coated with the protective cap layer such that the protective cap layer is provided over an entire exterior of the film. In another arrangement, such as that described below with respect to Figure 6, the film may comprise a plurality of layers, wherein each layer is comprised of a plurality of nanotubes. In an arrangement comprised of layers, one or more of the layers may be coated in a protective cap layer. Each protective cap layer coating a collective plurality of nanotubes may have a thickness of from 0.5 nm to 100 nm, desirably the thickness may be from 1 nm and 10 nm, more desirably the thickness may be 5 nm.

[00048] The film 1000 may optionally comprise both silicon-based nanotubes and carbon-based nanotubes. As explained above with respect to the cap layer, such a combination may enable the beneficial properties of silicon and carbon to be utilized effectively.

[00049] The silicon-based nanotubes may be arranged to form a layer of silicon-based nanotubes. Additionally, or alternatively, the carbon-based nanotubes may be arranged to form a layer of carbonbased nanotubes.

[00050] Figure 6 shows a film 1000 including a layer of carbon-based nanotubes 100 and a layer of silicon-based nanotubes 200. In particular, the arrangement of figure 6 includes two layers of carbonbased nanotubes 100. In this arrangement, the layer of silicon-based nanotubes 200 is disposed between layers of carbon-based nanotubes 100. In particular, it is desirably that the outermost layers of the film 100 are layers of carbon-based nanotubes 200. In this way, the layers of carbon-based nanotubes 200 may be more exposed to the environment around the film 1000 than the layer of silicon-based nanotubes 100. With this arrangement, the layers of carbon-based nanotubes 200 may protect the layer of silicon- based nanotubes 100. [00051] In another arrangement, the film may further comprise at least one additional layer of silicon- based nanotubes and/or carbon-based nanotubes. Additionally, or alternatively, the film may comprise at least one layer formed of a combination of both silicon-based nanotubes and carbon-based nanotubes. [00052] In the arrangement of Figures 2A and 2B, the film 1000 is part of a film assembly also comprising a structure 500 to support the film 1000. In particular, the structure 500 may aid in maintaining the shape of the film 100. In other words, the structure 500 may desirably be configured to mitigate bending or distortion of the film 1000. Furthermore, the structure 500 may aid in maintaining the film 1000 in the desired location and orientation for use within an apparatus. The structure 500 may be a frame.

[00053] The structure 500 may support the film 1000 at towards a periphery of the film 1000. In other words, towards an outside of the film 1000 and away from a central region of the film 1000 (in plan view, as seen in Figure 2A). In this way, the structure 500 may avoid a location towards a center of the film (in plan view). The center of the film may therefore be unobscured such that the film may perform a function of allowing desirable radiation to pass through the film while filtering out undesirable radiation.

[00054] In the arrangement of Figures 2A and 2B, the structure 500 supports the film 1000 at a peripheral surface 1001 of the film 1000. The structure 500 is optionally continuous, and the structure 500 may optionally surround the film 1000. In the arrangement of Figures 2A and 2B, the structure 500 is a border supporting the peripheral surface 1001 of the film 1000. The film 1000 may cover the border. [00055] In an alternative arrangement, the structure may be discontinuous. The structure may be arranged to support the film at discrete locations. If the film has a non-circular shape (in plan view), for example a square or rectangular shape, the structure may be configured to support the corners of the film.

[00056] Alternatively, in another arrangement, the structure may be a net or mesh arranged to support the film. In this way, there may be sufficient open areas of the net which enable transmission of radiation through the net.

[00057] In an alternative arrangement, not shown in Figure 2A and 2B, the film may be self- supporting. In other words, the film may have a strength and stiffness which is sufficient for the film to perform its function without a structure being provided to support the film. This may be a desirable arrangement due to the reduced manufacturing cost and complexity comparted to an arrangement in which a structure is provided to support the film.

[00058] In some circumstances, it may be desirable to provide a structure to support the film, even if the film itself has sufficient structural integrity to be self-supporting. For example, a structure, such as a frame, may aid in arranging the film at the desired location and orientation within an apparatus. In particular, the structure may include attachment points which may be used to connect the film assembly to other components of the apparatus. [00059] The film assembly may be manufactured by depositing the film on a support substrate. The film may be deposited in layers. For example, one layer of nanotubes may be deposited followed by another layer of nanotubes until the film is complete. In other words, the film may be manufactured by sequentially depositing layers of nanotubes. Once the film has been made, selected regions of the support substrate may be removed such that the remaining regions of the support substrate form the structure configured to support the film. Any suitable method, for example etching, may be used to remove the selected regions of the support substrate. Alternatively, the film may be separated from the support substrate and the film may be attached to a, pre-made, structure to support the film.

[00060] The film or the film assembly, such as that of Figure 2A and 2B, may be comprised in a lithographic component of a lithographic apparatus. The film or the film assembly may be a lithographic component of a lithographic apparatus. The film is desirably disposed within a radiation path in the lithographic apparatus. In this way, the film may perform a spectral filtering function. The structure configured to support the film is desirably disposed outside the radiation path. In other words, the structure desirably is arranged such that desired radiation is able to pass the film assembly without being blocked or overly suppressed.

[00061] The lithographic apparatus may an optical compartment and a substrate compartment. The optical compartment may house optical components configured to direct radiation at a substrate undergoing lithography. The substrate compartment may house a substrate table (WT) configured to support the substrate undergoing lithography. The lithographic component, which comprises the film, is desirably configured to functions as a spectral filter. For example, the film may be configured to transmit desired radiation and to suppress undesired radiation within the lithographic apparatus.

[00062] The lithographic component is desirably arranged within the lithographic apparatus such that the film is disposed between the optical compartment and the substrate compartment. In other words, the lithographic apparatus is desirably configured such that the film acts as a spectral filter for radiation emitted from the optical components towards the substrate. For example, in the lithographic apparatus of Figure 1, the lithographic component may be disposed between the projection system PS and the substrate table WT.

[00063] Alternatively, or additionally, a lithographic component comprising the film may be disposed within the projection system PS. The lithographic component may be disposed closer to the substrate table than any other components of the projection system PS.

[00064] Alternatively, or additionally, a lithographic component comprising the film may be configured to be provided on or adjacent the patterning device MA (e.g., a mask) to act as a support structure MT, such as described above with reference to Figure 1. In other words, the lithographic component may act as a pellicle. In this context, a pellicle is a component, such as a film, configured to protect the patterning device MA (e.g., a mask) from undesired radiation. The lithographic component may be configured to be attached to the patterning device MA. [00065] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquidcrystal displays (LCDs), thin-film magnetic heads, etc.

[00066] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate) or mask (or other patterning device). These apparatuses may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions or ambient (non- vacuum) conditions.

[00067] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

[00068] Embodiments include the following numbered clauses:

1. A film for a lithographic apparatus, the film comprising a plurality of nanotubes, wherein the plurality of nanotubes comprises silicon-based nanotubes for filtering undesired radiation.

2. A film for a lithographic apparatus, the film comprising a plurality of nanotubes, wherein the plurality of nanotubes comprises carbon-based nanotubes coated with a silicon-based cap layer for filtering undesired radiation.

3. The film according to either of clauses 1 and 2, wherein the film is transparent for at least 80% extreme ultraviolet radiation.

4. The film according to any preceding clause, wherein the film is configured to filter out at least 70% of deep ultraviolet radiation.

5. The film according to any preceding clause, wherein at least 80% of the nanotubes have a diameter of between 5 nm and 30 nm.

6. The film according to any of the preceding clauses, wherein a plurality of the nanotubes are coated with a cap layer.

7. The film according to clause 6, wherein at least some of the nanotubes are individually coated with the cap layer.

8. The film according to either of clauses 6 and 7, wherein each cap layer has a thickness of between 0.5 nm and 2 nm.

9. The film according to clause 6, wherein at least some of the nanotubes are collectively coated with a protective cap layer. 10. The film according to clause 9, wherein the protective cap layer has a thickness of from 1 nm to 10 nm.

11. The film according to any one of clauses 6 to 10, wherein the cap layer comprises carbon.

12. The film according to any one of clauses 6 to 10, wherein the cap layer comprises a metal or a semimetal.

13. The film according to clause 12, wherein the cap layer comprises one or more of: aluminium, zirconium, yttrium, niobium, ruthenium or molybdenum.

14. The film according to clause 12, wherein the cap layer comprises silicon.

15. The film according to clause 14, wherein the cap layer comprises a compound comprising silicon.

16. The film according to clause 15, wherein the compound comprises a metal and/or oxygen.

17. The film according to clause 14, wherein the cap layer is silicon.

18. The film according to any preceding clause, comprising both silicon-based nanotubes and carbonbased nanotubes.

19. The film according to clause 18, wherein the silicon-based nanotubes are arranged to form a layer of silicon-based nanotubes and wherein the carbon-based nanotubes are arranged to form a layer of carbon-based nanotubes.

20. The film according to clause 19, wherein the layer of silicon-based nanotubes is disposed between layers of carbon-based nanotubes.

21. The film according to either of clauses 19 and 20, wherein the outermost layers of the film are layers of carbon-based nanotubes.

22. The film according to any of clauses 19 to 21, further comprising at least one additional layer of silicon-based nanotubes and/or carbon-based nanotubes.

23. The film according to any of clauses 18 to 22, further comprising at least one layer formed of a combination of both silicon-based nanotubes and carbon-based nanotubes.

24. The film according to any preceding clause, wherein the nanotubes are arranged to form a mesh.

25. The film according to clause 24, wherein the mesh has an irregular structure.

26. The film according to any of the preceding clauses, wherein the film is self-supporting.

27. A film assembly comprising: a film according to any of clauses 1 to 26, and a structure configured to support the film.

28. The film assembly of clause 27, wherein the structure supports the film at towards a periphery of the film.

29. The film assembly of clause 28, wherein the structure supports the film at a peripheral surface of the film.

30. The film assembly of clause 29, wherein the structure is a border supporting a peripheral surface of the film, and wherein the film covers the border.

31. The film assembly of any of clauses 27 to 29, wherein the structure is a frame. 32. A lithographic component for a lithographic apparatus, the lithographic component comprising the film of any of clauses 1 to 26 or the film assembly of any of clauses 27 to 31.

33. The lithographic component according to clause 32, wherein the lithographic component functions as a spectral filter.

34. The lithographic component according to either of clauses 32 and 33, wherein the lithographic component functions as a pellicle.

35. The lithographic component according to any of clauses 32 to 34, wherein the lithographic component is configured to be attached to a patterning device.

36. A lithographic apparatus comprising a lithographic component according to any of clauses 32 to 35.

37. The lithographic apparatus of clause 36, comprising: an optical compartment housing optical components configured to direct radiation at a substrate undergoing lithography; and a substrate compartment housing a substrate table configured to support the substrate undergoing lithography; wherein the lithographic component is arranged such that the film is disposed between the optical compartment and the substrate compartment.

38. The lithographic apparatus of clause 36, wherein the lithographic component is attached to a patterning device.

39. The lithographic apparatus of any of clauses 36 to 38, wherein the film is disposed in a radiation path.

40. The lithographic apparatus of any of clauses 36 to 39, wherein the lithographic component comprises a film assembly according to any of clauses 27 to 31 , wherein the structure is disposed outside a radiation path.

41. A method of manufacturing the film according to any of clauses 1 to 26, comprising fabricating a plurality of nanotubes and arranging the nanotubes to form the film.

42. A method of manufacturing the film assembly according to any of clauses 27 to 31 , comprising depositing the film on a support substrate.

43. The method of clause 42, further comprising removing selected regions of the support substrate such that the remaining regions of the support substrate form the structure configured to support the film.

44. The method of clause 43, wherein the removing selected regions of the support substrate comprises etching the selected regions of the support substrate.

45. The method of clause 42, further comprising separating the film from the support substrate and attaching the film to the structure.

46. The method of any of clauses 42 to 45, wherein depositing the film comprises sequentially depositing layers of nanotubes.

Claims

3. The film according to either of claims 1 and 2, wherein the film is transparent for at least 80% extreme ultraviolet radiation.

4. The film according to any preceding claim, wherein the film is configured to filter out at least 70% of deep ultraviolet radiation.

5. The film according to any preceding claim, wherein at least 80% of the nanotubes have a diameter of between 5 nm and 30 nm.

6. The film according to any of the preceding claims, wherein a plurality of the nanotubes are coated with a cap layer.

7. The film according to claim 6, wherein at least some of the nanotubes are individually coated with the cap layer.

8. The film according to either of claims 6 and 7, wherein each cap layer has a thickness of between 0.5 nm and 2 nm.

9. The film according to claim 6, wherein at least some of the nanotubes are collectively coated with a protective cap layer.

10. The film according to claim 9, wherein the protective cap layer has a thickness of from 1 nm to 10 nm.

11. The film according to any one of claims 6 to 10, wherein the cap layer comprises carbon.

12. The film according to any one of claims 6 to 10, wherein the cap layer comprises a metal or a semimetal.

13. The film according to any preceding claim, comprising both silicon-based nanotubes and carbon-based nanotubes.

14. The film according to claim 13, wherein the silicon-based nanotubes are arranged to form a layer of silicon-based nanotubes and wherein the carbon-based nanotubes are arranged to form a layer of carbon-based nanotubes.

15. The film according to claim 14, wherein the layer of silicon-based nanotubes is disposed between layers of carbon-based nanotubes.

16. The film according to either of claims 14 and 15, wherein the outermost layers of the film are layers of carbon-based nanotubes.

17. The film according to any of claims 14 to 16, further comprising at least one additional layer of silicon-based nanotubes and/or carbon-based nanotubes.

18. The film according to any of claims 13 to 17, further comprising at least one layer formed of a combination of both silicon-based nanotubes and carbon-based nanotubes.

19. A film assembly comprising: a film according to any of claims 1 to 18, and a structure configured to support the film.

20. A lithographic component for a lithographic apparatus, the lithographic component comprising the film of any of claims 1 to 19.