Coated free-standing film of carbon nanostructures

Abstract

To improve printing defects, which are a major constraint on EUV lithography uptake.SOLUTION: There is disclosed a structure including a coated free-standing film attached to a support. The free-standing film is a free-standing film of carbon nanostructures and a parylene-coating having a thickness of 5 to 200 nm is provided on the free-standing film. There is also disclosed use of the parylene-coating for allowing transmittance of ionizing radiation, while reducing gas permeability of the structure by providing the structure comprising the free-standing film of carbon nanostructures attached to the support and the metal-based coating with the parylene-coating having a thickness of 5 to 200 nm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a structure comprising a coated free-standing film attached to a support. The present disclosure relates to a method and use for reducing gas permeability while allowing transmission of ionizing radiation through a structure comprising a free-standing film of carbon nanostructures attached to a support and a metal-based coating. Further, uses of the structure are disclosed. [Background technology]

[0002] Extreme ultraviolet lithography (EUV or EUVL) is an optical lithography technique that uses the extreme ultraviolet wavelength range. EUV pellicle films are used to protect photomasks on wafers from defects, improve accuracy, shorten processing times, and increase production efficiency. However, printing defects remain a major limitation to the uptake of EUV lithography. Therefore, sophisticated particle filters similar to EUV pellicle films are needed. Summary of the Invention [Means for solving the problem]

[0003] A structure is disclosed that includes a coated, free-standing film attached to a support. The free-standing film is a free-standing film of carbon nanostructures. A parylene coating having a thickness of 5 to 200 nm is provided on the free-standing film.

[0004] Further disclosed is a method for reducing gas permeability while allowing transmission of ionizing radiation through a structure including a free-standing film of carbon nanostructures attached to a support and a metal-based coating, the method comprising providing the structure with a parylene coating having a thickness of 5 to 200 nm.

[0005] Further disclosed is the use of a parylene coating to reduce gas permeability while allowing transmission of ionizing radiation by providing a parylene coating having a thickness of 5 to 200 nm to a structure including a free-standing film of carbon nanostructures attached to a support and a metal-based coating.

[0006] Further disclosed is the use of the structures disclosed in the current disclosure as a sensor, an optical filter, a debris filter, a pellicle, a membrane filter, an electron blocking window, or any combination of at least two of these.

[0007] The accompanying drawings provide a further understanding of the embodiments, are included in and constitute a part of this specification, illustrate one embodiment, and together with the description, serve to explain the principles of the invention. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows a scanning electron microscope (SEM) micrograph of a structure according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present disclosure relates to a structure including a coated free-standing film attached to a support, the free-standing film being a free-standing film of carbon nanostructures, and a parylene coating having a thickness of 5 to 200 nm provided on the free-standing film.

[0010] The present disclosure further relates to a method for reducing gas permeability while allowing transmission of ionizing radiation through a structure including a free-standing film of carbon nanostructures attached to a support and a metal-based coating, the method comprising providing the structure with a parylene coating having a thickness of 5 to 200 nm.

[0011] The present disclosure further relates to the use of a parylene coating having a thickness of 5 to 200 nm on a structure including a free-standing film of carbon nanostructures attached to a support and a metal-based coating, thereby reducing the gas permeability of the structure while allowing transmission of ionizing radiation.

[0012] The ability of a structure to transmit and / or block electromagnetic radiation may be determined by high spectral resolution transmittance measurements using a synchrotron, which may be performed to establish the suitability of the structure for use in further applications, such as EUV applications.

[0013] In this manner, the structure is configured to be transparent to ionizing radiation. That is, the structure may be transparent to "high energy radiation," such as, for example, X-radiation and extreme ultraviolet radiation. In one embodiment, the structure is configured to be transparent to X-radiation and extreme ultraviolet radiation. In one embodiment, the structure is configured to be transparent to X-rays or extreme ultraviolet radiation.

[0014] The structure may be a sensor, a filter, a pellicle, an electron blocking window, or any combination of at least two of these.

[0015] The structure may be a sensor, an optical filter, a debris filter, a pellicle, a membrane filter, an electron blocking window, or any combination of at least two of these.

[0016] The present disclosure further relates to the use of the structures disclosed in the current disclosure as sensors, optical filters, debris filters, pellicles, membrane filters, electron blocking windows, or any combination thereof.

[0017] An optical filter is a filter or device that selectively transmits different wavelengths of light or radiation. Thus, an X-ray optical filter may transmit X-rays but reject radiation of some different wavelengths. Similarly, an EUV (extreme ultraviolet) optical filter may transmit EUV radiation but reject radiation of some different wavelengths. Another example of a filter is a debris filter, which is sometimes called a particle filter. An example of a debris filter is an EUV debris filter, which may transmit EUV radiation but block the passage of debris and particles.

[0018] An electron-blocking window is a device that blocks the transmission of electrons. An example of an electron-blocking window is an electron-blocking x-ray window. An electron-blocking x-ray window is a device that is transparent to x-rays and blocks the transmission of electrons.

[0019] In one embodiment, the optical filter is an X-ray optical filter, an extreme ultraviolet (EUV) optical filter, or a combination thereof. In one embodiment, the optical filter is an X-ray optical filter and an extreme ultraviolet (EUV) optical filter. In one embodiment, the optical filter is an X-ray optical filter or an extreme ultraviolet (EUV) optical filter.

[0020] In one embodiment, the filter is used as an EUV debris filter, an EUV optical filter, or a combination thereof. In one embodiment, the filter is used as an EUV debris filter and an EUV optical filter. In one embodiment, the filter is used as an EUV debris filter or an EUV optical filter.

[0021] In one embodiment, the sensor is a wearable or implantable sensor, a biosensor, a gas sensor, an electrochemical sensor, a touch sensor, or a strain sensor.

[0022] In one embodiment, the pellicle is an extreme ultraviolet lithography pellicle or a high transmittance pellicle.

[0023] Disclosed is a structure comprising a coated, free-standing film attached to a support. A parylene coating may be provided on the free-standing film. In this specification, a reference to a coating "on" a free-standing film of carbon nanostructures should be understood to mean that the coating is provided or formed to be located on or upon the free-standing film of carbon nanostructures, unless otherwise stated. The free-standing film of carbon nanostructures may act as a carrier or support structure for the coating. In one embodiment, a parylene coating is provided directly on the free-standing film of carbon nanostructures, without any additional layers, coatings, or films interposed therebetween. However, in other embodiments, a metal-based coating, for example, may be provided between the parylene coating and the free-standing film of carbon nanostructures.

[0024] In one embodiment, the parylene is unsubstituted parylene (Parylene N), chlorinated parylene (Parylene C, Parylene D), fluorinated parylene (Parylene AF-4), alkyl-substituted parylene (Parylene M, Parylene E), reactive parylene (Parylene A, Parylene AM), colored parylene, or crosslinked parylene (Parylene X), or any combination of at least two of these. Colored parylene may be considered parylene with chromophores attached directly to the [2.2]paracyclophane-based molecule to impart color to the parylene.

[0025] In one embodiment, the parylene is unsubstituted parylene, i.e., parylene N. Parylene N has the added advantage that it contains only carbon and hydrogen, making its structure closer to that of a carbon nanotube or carbon nanobud.

[0026] The inventors have observed that it is possible to provide a thin parylene coating on a free-standing film of carbon nanostructures by depositing the parylene coating directly onto the unsupported film over its entire area. Providing a parylene coating on a free-standing film of carbon nanostructures has the added benefit that the parylene provides a so-called planarizing layer on the carbon nanostructure film, allowing a smooth metal-based coating to then be formed on the planarizing layer. Thus, parylene may be deposited from the vapor phase onto a porous surface, making the porous surface smooth and uniform for further coatings.

[0027] The parylene coating has the added utility of providing a gas seal to the structure by blocking any holes that may form between the carbon nanostructures in the free-standing film. Using a parylene coating to fill any holes in the free-standing film of carbon nanostructures has the added utility that the parylene coating does not impair the permeability of the formed structure. Because the parylene coating may be made from the vapor phase, the parylene coating may form a conformal coating on the free-standing film of carbon nanostructures, making its surface smoother and providing a more defect-free surface.

[0028] Additionally, by providing a parylene coating between the free-standing film of carbon nanostructures and the metal-based coating, the oxidation effects of the metal-based coating may be significantly slowed. Chemical deposition of inorganic layers on carbon nanostructure films is generally considered troublesome due to oxidation of the carbon nanostructure film.

[0029] Without being bound to any particular theory as to why oxidation is slower, this may be due to the smaller surface area of ​​the inorganic layer, for example, a metal-based coating.

[0030] Metal-based coatings may be used in devices with optical functionality to filter out specific wavelengths, so the structures can be used, for example, as optical filters with relatively low X-ray / EUV absorption but high, for example, IR absorption.

[0031] In one embodiment, the parylene coating is provided on only one side of the free-standing film of carbon nanostructures. In one embodiment, the parylene coating is provided on both sides of the free-standing film of carbon nanostructures. Providing a parylene coating on both sides of the free-standing film has the added benefit of providing improved mechanical performance because it allows the carbon nanostructures to be fully embedded in the parylene coating.

[0032] In one embodiment, the structure comprises a parylene coating provided on only one side of a free-standing film of carbon nanostructures. In one embodiment, the structure comprises a parylene coating provided on both sides of a free-standing film of carbon nanostructures.

[0033] In one embodiment, the parylene coating has a thickness of 10-190 nm, or 15-170 nm, or 20-150 nm, or 25-130 nm, or 30-100 nm, or 35-80 nm, or 40-60 nm. Thin parylene coatings have the added benefit of reducing the amount of light absorption. The thickness of a parylene coating may be measured using thin film interference and absorbance at 233 nm. When the refractive index of the parylene coating is known, the thin film interference pattern can be used to calculate the thickness of the coating. Fresnel's equations, Snell's law, and trigonometry may be used to calculate the thickness of a coating with a known refractive index. The following equation may be used: m*α=2*n*d*cos(angle) (m-0.5)*α=2*n*d*cos(angle) m = positive integer α=wavelength (nm) n = refractive index d = coating thickness angle = refraction angle within the coating

[0034] In this manner, the free-standing film of carbon nanostructures is attached to the support. The support may be any type of support suitable for attaching a free-standing film of carbon nanostructures. In one embodiment, the support is formed of glass, metal, plastic, or any combination thereof. The form of the support may vary. The support may have the form of a frame. In one embodiment, the support has the form of a frame to which the film or carbon nanostructures are attached. The frame may support the free-standing film of carbon nanostructures at its outer edges, thereby forming free-standing, unsupported regions of the carbon nanostructure film. The support locations may be located anywhere on the structure as long as they provide sufficient support for the carbon nanostructure film. For example, the support locations may be on the sides of the free-standing film of carbon nanostructures, in areas near corners, or adjacent along the sides. Any larger area including multiple support points is also intended to be encompassed by this aspect, such as when the frame has a continuous, circular shape and the free-standing regions are located within the circle. The frame may also have any other elongated, continuous shape. In one embodiment, the frame is shaped as a circle, square, triangle, rectangle, oval, or polygon.

[0035] Carbon nanostructures are used to form freestanding films. The term "nanostructure" in this specification, unless otherwise stated, should be understood as a structure having one or more characteristic dimensions on the nanometer scale, i.e., up to about 100 nanometers. The dimensions of conductive nanostructures in two perpendicular directions may be significantly different orders of magnitude. For example, a nanostructure may have a length 10, 100, or even 100,000 times greater than its thickness or width. In a carbon nanostructure film, many of the carbon nanostructures are interconnected to form a network of interconnected molecules. On a macroscopic scale, such a network forms a solid, monolithic material in which the individual molecular structures are either disoriented or non-oriented, i.e., substantially randomly oriented, or oriented. Various types of carbon nanostructure networks can be fabricated in the form of thin, transparent layers.

[0036] In one embodiment, the carbon nanostructures include carbon nanotubes (CNTs), carbon nanobuds (CNBs), carbon nanoribbons, or any combination or mixture thereof. In one embodiment, the carbon nanostructures include carbon nanotubes, carbon nanobuds, or any combination or mixture thereof. Carbon nanobuds, sometimes referred to as carbon nanobud molecules, have fullerene or fullerene-like molecules covalently attached to the sides of a tubular carbon molecule. Such carbon nanotubes and carbon nanobuds have the added benefit of being highly transparent at X-ray and visible wavelengths. In addition, they have robust mechanical properties and high chemical inertness.

[0037] Various procedures exist in the art that can be used to form free-standing films of carbon nanostructures. Different approaches can be used to synthesize and / or deposit carbon nanostructures to form films. For example, in the case of carbon nanotubes or carbon nanobud molecules, deposition can be carried out by commonly known methods, such as filtration from the gas phase or liquid, deposition in a force field, or deposition from solution using spray coating or spin drying. Carbon nanobud molecules can be synthesized using methods such as those disclosed in WO 2007 / 057501 and deposited directly onto a substrate, for example, from an aerosol stream, with the aid of, for example, electrophoresis or thermophoresis, or by methods such as those described by Nasibulin et al., "Multifunctional Free-Standing Single-Walled 20 Carbon Nanotube Films," ACS NANO, vol. 5, no. 4, pp. 3214-3221, 2011. Functionalization of carbon nanostructures can be considered as the creation of functional groups on the surface of the carbon nanostructures. Functionalization of carbon nanostructures has the additional utility of increasing their reactivity, increasing their solubility, or enabling various chemical modifications such as ion adsorption, metal deposition, or grafting reactions.

[0038] Freestanding films of carbon nanostructures may be formed, for example, by synthesizing carbon nanostructures in, for example, the vapor phase and collecting or depositing the carbon nanostructures from the vapor phase. The carbon nanostructure film may be formed by first collecting or depositing the synthesized carbon nanostructures in one orientation in the reaction chamber, rotating it, for example, 90 degrees, and continuing to collect or deposit additional carbon nanostructures thereon. Alternatively, the carbon nanostructure film may be formed by randomly collecting or depositing the carbon nanostructures.

[0039] In one embodiment, the coated freestanding film has a thickness of 0.1 to 1000 cm 2 , or 1 to 500 cm 2 , or 5 to 350 cm 2 , or 10 to 200 cm 2 , or 50~150cm 2 It has a size of

[0040] In one embodiment, the thickness of the free-standing film of carbon nanostructures is 9 to 8,000 nm, or 15 to 7,000 nm, or 20 to 5,000 nm, or 50 to 2,500 nm, or 100 to 1,000 nm, or 200 to 600 nm. In one embodiment, the thickness of the free-standing film of carbon nanostructures is 9 to 600 nm, or 15 to 500 nm, or 20 to 400 nm, or 50 to 300 nm, or 100 to 200 nm. In one embodiment, the thickness of the free-standing film of carbon nanostructures is 100 to 8,000 nm, or 200 to 7,000 nm, or 300 to 5,000 nm, or 400 to 2,500 nm, or 500 to 1,000 nm. The thickness of free-standing films of carbon nanostructures may be measured, for example, by atomic force microscopy (AFM), optical profilometers, or contact profilometers such as ellipsometry and cross-sectional electron microscopy. Forming free-standing films of carbon nanostructures has the added utility of being able to form thin films. However, free-standing films of carbon nanostructures should not be too thin, as this can affect the ability of the free-standing film of carbon nanostructures to support itself when attached to a substrate.

[0041] In one embodiment, a metal-based coating is provided over the parylene coating. In one embodiment, a parylene coating is provided between the metal-based coating and the free-standing film of carbon nanostructures. In one embodiment, a metal-based coating is provided between the parylene coating and the free-standing film of carbon nanostructures. In one embodiment, a first metal-based coating is provided over the parylene coating and a second metal-based coating is provided between the parylene coating and the free-standing film of carbon nanostructures. The metal-based coatings may be at least partially or completely embedded inside the parylene coating.

[0042] The structure may include a metal-based coating. The structure may include a metal-based coating on a free-standing film of carbon nanostructures surrounded by a parylene coating. The surrounding parylene coating has the added benefit that the parylene fills any pinholes in the metal-based coating and / or the free-standing film of carbon nanostructures, while reducing oxidation of the metal-based coating and improving the mechanical properties of the structure.

[0043] In one embodiment, the metal-based coating has a thickness of 1 to 300 nm, or 1 to 100 nm, or 1 to 50 nm, or 1 to 30 nm, or 1 to 20 nm, or 1 to 10 nm. The thickness of the metal-based coating may be measured by, for example, transmission electron microscopy (TEM) techniques, scanning electron microscopy (SEM) techniques, or any other relevant techniques.

[0044] The metal-based coating may be formed of aluminum, zirconium, molybdenum, metal silicide, ruthenium, beryllium, niobium, or any carbide, oxide, or nitrate thereof, or any combination or mixture thereof. The metal-based coating may comprise or consist of aluminum, zirconium, molybdenum, metal silicide, ruthenium, beryllium, niobium, or any carbide, oxide, or nitrate thereof, or any combination or mixture thereof. In one embodiment, the metal-based coating is a metal-based blocking layer configured to block electromagnetic radiation having wavelengths greater than 400 nm, greater than 450 nm, or greater than 500 nm. The metal-based coating has the additional utility of blocking undesired wavelengths of radiation from passing through the filter. The metal-based coating has the further additional utility of functioning as a gas barrier.

[0045] In one embodiment, the structure includes a polymer layer. In one embodiment, a polymer layer is provided on a parylene coating. In one embodiment, a parylene coating is provided between the polymer layer and the free-standing film of carbon nanostructures. The polymer layer has the additional benefit of blocking lower energy radiation, such as near-UV radiation and visible light, from penetrating the structure. Thus, a polymer coating that can absorb visible light may provide a dark color. As an example, mention may be made of conductive forms of polyaniline, which may exhibit a dark color due to their ability to absorb light across the visible spectrum.

[0046] In one embodiment, a parylene coating is provided on a free-standing film of carbon nanostructures. In one embodiment, the parylene coating is deposited from the vapor phase. The parylene coating may be formed or deposited by pyrolysis of a selected dimer in a vacuum environment at temperatures of 600-750°C, or 650-700°C, or 680-690°C. The dimer is thus vaporized into a dimer gas. Deposition then occurs on a cooler (i.e., room temperature) surface inside the deposition chamber under continued vacuum.

[0047] The structures disclosed in the current disclosure have the additional utility of being structures that can reduce or prevent gases from passing through the structure while allowing certain radiation to pass through the structure, such as inert gases that may be desired to be blocked from passing through the structure in certain applications.

[0048] The structures disclosed in the current disclosure have the added utility of reducing light absorption by the structure by including a thin parylene coating, which has the added utility of reducing or preventing oxidation of metal-based coatings that may be used, which may result in light absorption by the structure. [Example]

[0049] Reference will now be made in detail to the described embodiments, examples of which are illustrated in the accompanying drawings.

[0050] The following description discloses some embodiments in sufficient detail to enable one skilled in the art to use the method based on the present disclosure. Not all steps of the embodiments are discussed in detail because some steps may be obvious to one skilled in the art based on this specification.

[0051] FIG. 1 shows an SEM micrograph of a structure comprising a Parylene N coating having a thickness of 10 nm on a free-standing film of carbon nanotubes.

[0052] Example 1 Fabrication of a structure containing a parylene coating In this example, different structures were fabricated and tested for their ability to transmit EUV radiation and block certain gases from passing through the structure. The materials used are listed in Table 1.

[0053] [Table 1]

[0054] Example and comparative structures were prepared as presented in Table 2.

[0055] [Table 2]

[0056] First, carbon nanotubes were synthesized in an aerosol laminar flow (floating catalyst) reactor using carbon monoxide and ferrocene as the carbon source and catalyst precursor, respectively. The formed carbon nanotubes were deposited from the gas phase onto a porous collection filter at a total gas flow rate of 60 l / min (maximum gas velocity of 0.13 m / s), forming a carbon nanotube film on the porous collection filter. The gas temperature was approximately 60°C. The formed carbon nanotube film had a thickness of 50 nm, corresponding to 81% T at a wavelength of 550 nm.

[0057] The resulting carbon nanotube film was then transferred from the porous collection filter to a rectangular plastic frame larger than the final circular frame. The film was then transferred to the final circular frame to form a free-standing film of carbon nanotubes attached to the frame. The frame thus had a circular shape with an opening in the center.

[0058] A parylene coating was then formed on the free-standing film of carbon nanotubes, followed by a metal-based coating on the parylene coating (example structure), or alternatively, a metal-based coating was formed directly on the free-standing film of carbon nanotubes, and this structure did not include a parylene coating (comparative example structure).

[0059] A parylene coating was formed by pyrolysis of di-p-xylene (dimer) at about 680°C in a vacuum environment and then depositing it on a cooler (i.e., room temperature) substrate inside a deposition chamber under continuous vacuum. The parylene coating had a thickness of 185 nm.

[0060] The metal-based coating was a MoSi2 metal-based coating having a thickness of 18 nm. The metal-based coating was formed using magnetron sputtering with DC power.

[0061] By using a particle accelerator (MAX IV synchrotron), the formed structures were subjected to EUV and DUV (deep ultraviolet radiation) measurements, the results of which are presented in Table 3.

[0062] [Table 3]

[0063] The results show that for the comparative example without the Parylene N coating, the EUV transparency of the MoSi2 layer was significantly lower than expected. This is likely due to the oxidation of MoSi2 to MoO3 and SiO2. By forming a Parylene N coating between the free-standing film of carbon nanotubes and the metal-based coating, this phenomenon does not occur and such oxidation is suppressed. Therefore, the use of a Parylene coating has the additional benefit of suppressing the oxidation of the MoSi2 coating to the highly EUV-absorbing compounds MoO3 and SiO2.

[0064] Furthermore, they noted that the parylene coating effectively blocks the holes present in the freestanding film of carbon nanotubes, thereby significantly reducing its gas permeability.

[0065] It is obvious to those skilled in the art that with the advancement of technology, the basic idea may be implemented in various ways, so the embodiments are not limited to the examples described above, but may instead vary within the scope of the claims.

[0066] The embodiments described herein above may be used in any combination with each other. Several embodiments may be combined together to form further embodiments. A structure, method, or use disclosed herein may include at least one of the embodiments described herein above. It will be understood that the benefits and advantages described above may relate to one embodiment or to several embodiments. The embodiments are not limited to embodiments that solve any or all of the described problems or have any or all of the described benefits and advantages. It will be further understood that reference to "an" item refers to one or more of those items. As used herein, the term "comprising" is used to mean inclusive of the features or operations that follow it, and does not exclude the presence of one or more additional features or operations.

Claims

1. 1. A structure comprising a coated free-standing film attached to a support, said free-standing film being a free-standing film of carbon nanostructures, and a parylene coating having a thickness of 5 to 200 nm provided on said free-standing film.

2. 10. The structure of claim 1, wherein the parylene is unsubstituted parylene, chlorinated parylene, fluorinated parylene, alkyl-substituted parylene, reactive parylene, colored parylene, or crosslinked parylene, or any combination of at least two thereof.

3. The structure of any one of claims 1 to 2, wherein the parylene coating is provided on only one side of the free-standing film of carbon nanostructures.

4. The structure of any one of claims 1 to 3, wherein the parylene coating is provided on both sides of the free-standing film of carbon nanostructures.

5. 5. The structure of any one of claims 1 to 4, wherein the parylene coating has a thickness of 10 to 190 nm, or 15 to 170 nm, or 20 to 150 nm, or 25 to 130 nm, or 30 to 100 nm, or 35 to 80 nm, or 40 to 60 nm.

6. 6. The structure of any one of claims 1 to 5, wherein the free-standing film of carbon nanostructures has a thickness of 8 to 8000 nm, or 15 to 7000 nm, or 20 to 5000 nm, or 50 to 2500 nm, or 100 to 1000 nm, or 200 to 600 nm.

7. The structure of any one of claims 1 to 6, wherein the support is formed of glass, metal, plastic, or any combination thereof.

8. The coated free-standing film has a thickness of 0.1 to 1000 cm ２ , or 1 to 500 cm ２ , or 5 to 350 cm ２ , or 10 to 200 cm ２ , or 50 to 150 cm ２ The structure according to any one of claims 1 to 7, having a size of

9. The structure of any one of claims 1 to 8, wherein a metal-based coating is provided over the parylene coating.

10. The structure of any one of claims 1 to 9, wherein a metal-based coating is provided between the parylene coating and the free-standing film of carbon nanostructures.

11. 11. The structure of claim 9 or claim 10, wherein the metal-based coating has a thickness of 1 to 300 nm, or 1 to 100 nm, or 1 to 50 nm, or 1 to 30 nm, or 1 to 20 nm, or 1 to 10 nm.

12. The structure of any one of claims 1 to 11, wherein the structure is a sensor, an optical filter, a debris filter, a pellicle, a membrane filter, an electron blocking window, or any combination of at least two of these.

13. 1. A method for reducing gas permeability while allowing transmission of ionizing radiation through a structure comprising a free-standing film of carbon nanostructures attached to a support and a metal-based coating, the method comprising providing the structure with a parylene coating having a thickness of 5 to 200 nm.

14. Use of a parylene coating to reduce gas permeability of a structure comprising a free-standing film of carbon nanostructures attached to a support and a metal-based coating, while allowing transmission of ionizing radiation, by providing the parylene coating having a thickness of 5 to 200 nm to the structure.

15. 15. The use of claim 14, wherein the parylene coating is provided such that the metal-based coating is interposed between the parylene coating and the free-standing film of carbon nanostructures.

16. The use according to any one of claims 14 to 15, wherein the parylene coating is provided between the metal-based coating and the free-standing film of carbon nanostructures.

17. The use according to any one of claims 14 to 16, wherein the parylene coating is deposited from the gas phase.

18. Use of the structure of any one of claims 1 to 12 as a sensor, an optical filter, a debris filter, a pellicle, a membrane filter, an electron blocking window, or any combination thereof.

19. 19. The use according to claim 18, wherein the pellicle is an extreme ultraviolet lithography pellicle.

Images