Self-standing film with HARM structure

Abstract

A method of forming a free-standing film comprising a high aspect ratio molecular structure (HARM structure) is disclosed. The method comprises: a) depositing a first portion of a HARM structure onto a porous filter to form a membrane of the HARM structure on the porous filter, b) transferring the membrane of the HARM structure from the porous filter to a frame to form a free-standing membrane of the HARM structure attached to the frame, and c) depositing a second portion of the HARM structure onto the free-standing film of the HARM structure attached to the frame to form a free-standing thin film of the HARM structure attached to the frame.

Description

Technical Field

[0001] The present disclosure relates to a method for forming a freestanding film (pellicle film) comprising a high aspect ratio molecular structure (HARM structure). The present disclosure also relates to a freestanding film comprising a high aspect ratio molecular structure (HARM structure) attached to a frame. The present disclosure also relates to the use of the freestanding film. Background Art

[0002] Extreme ultraviolet lithography (EUV or EUVL) is an optical lithography technology that uses the extreme ultraviolet wavelength range. EUV film structures are used to protect photomasks from defects, improve accuracy, shorten processes, and increase wafer production efficiency. However, defects in printing remain a key limiting factor in the promotion of EUV lithography technology. Therefore, complex and advanced particle filters such as EUV films are needed. Summary of the invention

[0003] The present invention discloses a method for forming a self-supporting film. The method for forming a self-supporting film containing a high aspect ratio molecular structure (HARM structure) comprises:

[0004] a) depositing a first portion of the HARM-structure onto a porous filter to form a film of the HARM-structure on said porous filter,

[0005] b) transferring the membrane of HARM-structures from the porous filter to a frame to form a free-standing membrane of HARM-structures attached to the frame, and

[0006] c) depositing a second portion of the HARM-structures onto the free-standing film of HARM-structures attached to said frame to form a free-standing thin film of HARM-structures attached to said frame.

[0007] In addition, the present invention discloses a self-supporting film comprising a high aspect ratio molecular structure (HARM structure) attached to a frame. The self-supporting film of the HARM structure exhibits a transmittance difference of at most 1% when calculated according to the following formula:

[0008] Transmittance difference (%) = maximum transmittance (%) - minimum transmittance (%),

[0009] in

[0010] The maximum transmittance is the maximum value of the transmittance of the free-standing film of the HARM structure measured at a wavelength of 550 nm;

[0011] The minimum transmittance is the minimum value of the transmittance of the free-standing film of the HARM-structure measured at a wavelength of 550 nm.

[0012] The invention also discloses the use of the self-supporting film in extreme ultraviolet lithography; as an extreme ultraviolet film; as an extreme ultraviolet debris filter; or as a film for an X-ray window. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to provide a further understanding of the embodiments and constitute a part of this specification and illustrate the embodiments. In the drawings:

[0014] Figure 1 A method for forming a free-standing film of a HARM-structure according to one embodiment is shown;

[0015] Figure 2 shows a schematic diagram of an optical measurement device for measuring transmittance;

[0016] Figure 3 and Figure 4 A defect image is shown. DETAILED DESCRIPTION

[0017] The present disclosure relates to a method for forming a free-standing film comprising a high aspect ratio molecular structure (HARM-structure), wherein the method comprises:

[0018] a) depositing a first portion of the HARM-structure onto a porous filter to form a film of the HARM-structure on said porous filter,

[0019] b) transferring the membrane of HARM-structures from the porous filter to a frame to form a free-standing membrane of HARM-structures attached to the frame, and

[0020] c) depositing a second portion of the HARMS-structure onto the free-standing film of HARM-structure attached to said frame to form a free-standing thin film of HARM-structure attached to said frame.

[0021] In one embodiment, the deposition of the first part of the HARM-structure and / or the second part of the HARM-structure is deposited from the gas phase. In one embodiment, step a) is depositing the first part of the HARM-structure from the gas phase onto a porous filter to form a film of the HARM-structure on the porous filter. In one embodiment, step c) is depositing the second part of the HARMS structure from the gas phase onto a self-standing film of the HARM-structure attached to the frame to form a self-standing film of the HARM-structure attached to the frame.

[0022] When depositing HARM-structures to form layers or films, porous filters can be used.Porous filters can be nonwoven filters or woven filters.Porous filters can be made of mixed cellulose esters (MCE), polyethersulfone (PES), track-etched polycarbonate, electrostatic spinning (PVDF) or polyethylene terephthalate (PET), polyamide, metal or glass fiber.The material of porous filter can be selected to make when depositing HARM-structures thereon from, for example, gas phase, the HARM-structures are retained on the porous filter, and thus gas itself, i.e. carrier gas, is filtered by the porous filter.

[0023] Typically, porous filters, as well as most surfaces, do not have a smooth and defect-free surface, but may contain multiple defects in the form of small holes or bumps and areas of high and low porosity. These porous filter defects may adversely affect the uniformity of the film deposited on the porous filter. These defects may degrade the mechanical properties of the film and impair the particle filtering capabilities of the film, for example in particle filtration or EUV film applications.

[0024] Generally, efforts have been made to seek to provide a filter with a surface as smooth and defect-free as possible for deposition, so as to reduce the inhomogeneity of the deposited film. However, the inventors were surprised to find that when a portion of the HARM-structure is first deposited on a porous filter, and then after the film of the formed HARM-structure is transferred to a frame, another portion of the HARM-structure is directly deposited on the self-supporting film of the HARM-structure, the defects in the self-supporting film of the produced HARM-structure can be effectively reduced. Not limited to any particular theory, with regard to forming a highly smooth self-supporting film by gradually depositing the HARM-structure, as disclosed in the current specification, it can be considered that when the second portion of the HARM-structure is deposited on the self-supporting HARM-structure film, the thinner portion of the film of the HARM-structure may pass more gas, while the thicker portion passes less gas. This may result in more HARM-structures being deposited at the potential defects of the self-supporting HARM-structure film, rather than other parts of the film.

[0025] Unless otherwise stated, in the present description the expression "defects" is to be understood as pores, thinner areas, indentations, pinholes, protrusions or areas of high and low porosity of the film.

[0026] The present disclosure also relates to a free-standing film comprising a high aspect ratio molecular structure (HARM-structure) attached to a framework, wherein the free-standing film of the HARM-structure exhibits a transmittance difference of at most 1% when calculated according to the following formula:

[0027] Transmittance difference (%) = maximum transmittance (%) - minimum transmittance (%),

[0028] in

[0029] The maximum transmittance is the maximum value of the transmittance of the free-standing film of the HARM structure measured at a wavelength of 550 nm;

[0030] The minimum transmittance is the minimum value of the transmittance of the free-standing film of the HARM-structure measured at a wavelength of 550 nm.

[0031] The transmittance can be calculated by using Figure 2 The optical measurement device shown in is measured according to the following: the device is calibrated to 100% T and 0% T. The frame with the film attached is placed on the workbench between the LED light source and the collimating lens. The distance between the LED and the collimator is set to 5cm, and the spot size is about 3mm. The LED type used is a Moonstone 3W high-brightness power LED light source (color temperature 4000K-10000K, 110-degree viewing angle, product model ASMT-MWE2-NNP00), and the spectrometer is OceanInsight STS-VIS-L-25-400-SMA (range: 350-800nm). Record the %T (% transmittance) value.

[0032] To determine the transmittance difference, for each square centimeter (cm 2 ) sample, take a %T measurement point. The maximum and minimum values ​​measured are used to calculate the transmittance difference (%).

[0033] The present disclosure also relates to the use of a self-supporting film as disclosed in this specification in extreme ultraviolet lithography; as an extreme ultraviolet film; as an extreme ultraviolet debris filter; or as a film for an X-ray window. In one embodiment, the self-supporting film is a film for extreme ultraviolet lithography; an extreme ultraviolet film; an extreme ultraviolet debris filter; or an X-ray window.

[0034] Unless otherwise stated, the expression "HARM structure" or "HARMS" should be understood in this specification to refer to "nanostructure", i.e. a structure with one or more nanoscale characteristic dimensions, i.e. less than or equal to about 100 nanometers. "High aspect ratio" refers to that the size of the conductive structure in two mutually perpendicular directions has a significantly different order of magnitude. For example, the nanostructure can have a length that is tens or hundreds of times higher than its thickness and / or width. In the film of the HARM structure, a large number of the nanostructures are interconnected to form a network of interconnected molecules. Considered on a macroscopic scale, the HARMS network forms a solid, monolithic material, in which the single molecular structure is non-oriented or non-oriented, i.e. substantially randomly oriented or oriented. The network of various types of HARM structures can be produced in the form of a thin transparent layer with a reasonable resistivity. In one embodiment, the HARM structure is a conductive HARM structure.

[0035] In one embodiment, the HARM-structure is a carbon nanostructure. In one embodiment, the carbon nanostructure comprises carbon nanotubes, carbon nanobuds, carbon nanoribbons or any combination thereof. In one embodiment, the carbon nanostructure comprises carbon nanotubes and / or carbon nanobuds. Carbon nanobuds or carbon nanobud molecules, as they may also be called, have fullerenes or fullerene-like molecules covalently bonded to the sides of tubular carbon molecules.

[0036] In one embodiment, the method comprises, before step a), forming or producing the step of HARM-structure as aerosol in gas phase. That is, HARM-structure can be initially produced in gas phase in reactor, and they can be deposited on porous filter or self-supporting membrane of HARM-structure respectively from reactor. Such deposition can be carried out by making airflow, for example carrier gas with HARM-structure, pass through porous filter or self-supporting membrane, thus HARM-structure is retained on porous filter or self-supporting membrane, and the sediment of HARM-structure is formed thereon, and carrier gas can pass through porous filter or self-supporting membrane simultaneously. HARM-structure can be deposited from gas phase, for example by filtering mode.

[0037] Deposition can be carried out by passing a gas stream comprising the HARM-structures through a porous filter or a free-standing membrane of the HARM-structures at a total gas flow rate of 5-500 l / min. The gas flow rate can be, for example, 5-30 L / min; or 30-90 L / min, or 40-80 L / min, or 50-70 L / min; or 90-500 L / min, or 100-450 L / min, or 150-400 L / min. The higher the flow rate, the higher the throughput of the gas stream through the porous filter of the free-standing membrane of the HARM-structures, thus affecting the costs involved in the method.

[0038] In one embodiment, a free-standing film of a HARM-structure is formed which exhibits a transmittance difference of at most 1% when calculated according to the following formula:

[0039] Transmittance difference (%) = maximum transmittance (%) - minimum transmittance (%),

[0040] in

[0041] The maximum transmittance is the maximum value of the transmittance of the free-standing film of the HARM structure measured at a wavelength of 550 nm;

[0042] The minimum transmittance is the minimum value of the transmittance of the free-standing film of the HARM-structure measured at a wavelength of 550 nm.

[0043] In one embodiment, a free-standing film of a HARM-structure has a thickness of 1 cm 2In one embodiment, the free-standing film of the HARM-structure has at most 10, or at most 5, or at most 3, or at most 1, or at most 0 defects per cm 2 0-10, or 1-5, or 1-3 defects are included. Therefore, it can be considered that the defect is a defect with a size greater than 15μm, or greater than 12μm, or greater than 9μm, or greater than 7μm, or greater than 5μm, or greater than 3μm, or greater than 2.5μm, or greater than 1.5μm, or greater than 1μm, or greater than 0.5μm, or greater than 0.3μm, or greater than 0.15μm in at least one direction. In one embodiment, the self-supporting film of the HARM structure has a size greater than 15μm, or greater than 12μm, or greater than 9μm, or greater than 7μm, or greater than 5μm, or greater than 3μm, or greater than 2.5μm, or greater than 1.5μm, or greater than 1μm, or greater than 0.5μm, or greater than 0.3μm, or greater than 0.15μm. 2 Contains at most 10, or at most 5, or at most 3, or at most 1, or 0 defects having a size greater than 15 μm, or greater than 12 μm, or greater than 9 μm, or greater than 7 μm, or greater than 5 μm, or greater than 3 μm, or greater than 2.5 μm, or greater than 1.5 μm, or greater than 1 μm, or greater than 0.5 μm, or greater than 0.3 μm, or greater than 0.15 μm.

[0044] The inventors surprisingly found that by the method disclosed in this specification one can reduce the number of defects present in a free-standing film of HARM-structures compared to depositing all HARM-structures directly only on a porous filter. The number of defects can be determined by using an optical microscope device, such as an Olympus MX63L, except that a camera is used instead of an eyepiece. The following parameters can be used:

[0045] Light source: Olympus BX3M LEDR LED light source for reflected light;

[0046] Objective lens: 10x (Olympus MPLFLN20XBD flat-field fluorite objective lens) Working distance: 6.5mm;

[0047] Imaging device: DP28-CU microscope camera;

[0048] Resolution: 0.68 microns / pixel;

[0049] Stage: Motorized XY stage;

[0050] Image analysis software: Olympus Stream Motion and ImageJ 1.52a.

[0051] The frame of the free-standing film with HARM structures is placed on the microscope XY stage, below the microscope objective. Using the microscope software, the stage is moved to a vertical position (Z axis) where the surface of the free-standing film with HARM structures is in the focus of the objective. The user then uses computer software to examine the image taken from the surface. Defective areas are identified as darker areas because the microscope uses light reflected from the sample surface to acquire the image, so holes or areas with fewer HARM structures appear darker because less light is reflected from those areas.

[0052] In one embodiment, the free-standing film of the HARM-structures exhibits a transmittance difference of at most 0.8%, or at most 0.7%, or at most 0.6%, or at most 0.5%, or at most 0.4%, or at most 0.35%, at most 0.33%, or at most 0.30%, or at most 0.25%, or at most 0.20%, or at most 0.15%, or at most 0.10%, or at most 0.05%.

[0053] The deposition of the first part of the HARM-structure and the deposition of the second part of the HARM-structure can continue until a predetermined or desired transmittance is achieved. When depositing the first part of the HARM-structure, a thinner HARM-structure film can be deposited, or a thicker HARM-structure film can be deposited. The same applies to the step of depositing the second part of the HARM-structure on the self-supporting film of the HARM-structure, that is, a thick or thin deposit can be formed. Therefore, the deposition of the first part of the HARM-structure can be continued until the transmittance of the film of the HARM-structure is 1-99%. In addition, the deposition of the second part of the HARM-structure can continue until the transmittance of the self-supporting film of the HARM-structure reaches a predetermined or desired value.

[0054] In one embodiment, continue the deposition of the first part of the HARM-structure, until the transmittance of the film of the HARM-structure when measured at a wavelength of 550nm is 80-99% or 85-98% or 90-96% or 92-94% of the energy of the light per unit time incident thereon vertically. In one embodiment, continue to deposit the first part of the HARM-structure, until the transmittance of the film of the HARM-structure when measured at a wavelength of 550nm is 90-99% or 92-98% or 94-96% of the energy of the light per unit time incident thereon vertically. The transmittance of the deposit formed on the porous filter can be measured with a camera in situ. Any suitable camera can be used. Only as an example, 10 positions, 1.6MP monochrome cameras can be mentioned. Then, after the film of the HARM-structure is transferred to the framework, final transmittance value can be determined.

[0055] In one embodiment, the deposition of the second portion of the HARM-structures is continued until the transmittance of the free-standing film of the HARM-structures measured at a wavelength of 550 nm is 50-95%, or 55-93%, or 60-87%, or 65-86%, or 70-85%, or 75-80% of the energy of light per unit time incident vertically thereon. In one embodiment, the deposition of the second portion of the HARM-structures is continued until the transmittance of the free-standing film of the HARM-structures measured at a wavelength of 550 nm is 80-87%, or 81-86%, or 82-85% of the energy of light per unit time incident vertically thereon.

[0056] The transmittance or transparency of a film mainly refers to the transparency of the film or its portion in the thickness direction. To achieve "transparency", a sufficient portion of the light energy incident on the film or its portion should be able to propagate through the film in the thickness direction.

[0057] In one embodiment, the deposition of the first part of the HARM-structure is continued until the thickness of the film of the HARM-structure is 3-50nm, or 5-45nm, or 7-40nm, or 10-35nm, or 15-30nm, or 20-25nm. In one embodiment, the deposition of the second part of the HARM-structure is continued until the thickness of the free-standing film of the HARM-structure is 75-400nm, or 76-350nm, or 77-300nm, or 78-250nm, or 79-200nm, or 80-160nm, or 81-140nm, or 82-120nm, or 83-110nm, or 84-100nm, or 85-90nm. The thickness of the film can be measured with a contact profiler, such as an atomic force microscope (AFM), or an optical profiler.

[0058] In one embodiment, the method comprises depositing a first portion of a HARM-structure until the thickness of the film of the HARM-structure is 99-75% or 95-85% of the total thickness of the free-standing film of the HARM-structure to be formed. In one embodiment, the method comprises depositing a first portion of a HARM-structure until the thickness of the film of the HARM-structure is 99-95%, or 95-85%, or 85-75% of the total thickness of the free-standing film of the HARM-structure to be formed.

[0059] In one embodiment, the formed free-standing thin film of HARM-structures is arranged to have a predetermined transmittance value, and the deposition of the first portion of the HARM-structures is continued until the film of the HARM-structures exhibits a transmittance of 75-15%, or 65-35%, or 55-35% of the predetermined transmittance value. In one embodiment, the formed free-standing thin film of HARM-structures is arranged to have a predetermined transmittance value, and the deposition of the first portion of the HARM-structures is continued until the film of the HARM-structures exhibits a transmittance of 75-65%, or 65-55%, or 55-35%, 35-15% of the predetermined transmittance value.

[0060] The film of the HARM-structure formed on the porous filter in step a) is transferred to the framework in step b) to form the self-supporting film of the HARM-structure. The framework can support the self-supporting film of the HARM-structure, or support the self-supporting film of the HARM-structure in the subsequent stage, supported on the outer edge part, thereby forming the unsupported independent area of ​​the self-supporting (thin) film of the HARM-structure. The supporting position can be located at any position in the structure, as long as they provide enough support for the self-supporting (thin) film of the HARM-structure. For example, they can be on the side of the self-supporting (thin) film of the HARM-structure, or in the area near the corner, or adjacent to each other along the side. Any wider area including multiple supporting points also means to be covered by this aspect, for example, if the framework has an uninterrupted circular shape, wherein the self-supporting area is located in the circle. The framework can also have any other uninterrupted shape of extension. In one embodiment, the framework is shaped as a circle, square, triangle, rectangle, ellipse or polygon.

[0061] In one embodiment, the frame is made of a polymer, quartz, titanium, graphite, silicon, silicon carbide, silicon nitride, polysilicon, a transition metal, or a transition metal alloy.

[0062] In one embodiment, the method further includes at least one other portion of the HARMS structure or other nanomaterials is deposited on the self-supporting film of the HARM structure. In one embodiment, the method further includes at least one other portion of the HARMS structure or other nanomaterials is deposited from the vapor phase on the self-supporting film of the HARM structure. The term "other nanomaterials" can refer to boron nitride nanotubes (BNNT), nanosheets, nanobelts, nanowires and nanofibers. As examples of nanosheets, graphene nanosheets, borene nanosheets, boron carbide nanosheets can be mentioned. As examples of nanobelts, graphene nanobelts and graphite nanobelts can be mentioned. As examples of nanowires, tungsten nanowires, copper nanowires, aluminum nanowires, nickel nanowires or silver nanowires can be mentioned. As examples of nanofibers, carbon nanofibers and silicon carbide nanofibers can be mentioned. In one embodiment, the method further includes depositing polymers on the self-supporting film of the HARM structure. Depositing the other portions of the same or different nanomaterials on the self-supporting film of the HARM structure has the increased utility of being able to form a film with a hybrid material structure.

[0063] In one embodiment, the method further comprises depositing a third portion of the HARMS structure onto the free-standing film of the HARM-structure. In one embodiment, the method further comprises depositing a third portion of the HARMS structure onto the free-standing film of the HARM-structure from the vapour phase.

[0064] In one embodiment, the method further comprises re-transferring the formed free-standing film of HARM-structures attached to the frame from the frame to a second frame, wherein the dimensions of the second frame are smaller than the dimensions of the frame, wherein the second frame is pushed through the free-standing film of HARM-structures attached to the frame to stretch the free-standing film of HARM-structures. The free-standing film of HARM-structures may thus be stretched due to the re-transfer, thereby generally enhancing the mechanical properties of the free-standing film, making the free-standing film flatter by reducing possible "wrinkles".

[0065] The material of the second frame may be different from the material of the frame. Transferring the free-standing film of the HARM-structure from the frame to the second frame has the additional utility of enabling post-processing methods, such as those carried out at high temperatures or in corrosive environments that would be detrimental to other frame materials.

[0066] The method disclosed in this specification has the additional utility of providing a self-supporting film comprising a HARM-structure having a smooth surface and a reduced number of defects. Since the number of defects in the self-supporting film can be reduced, its mechanical properties are improved. In addition, the capacity of the self-supporting membrane for particle filtration can be improved.

[0067] Example

[0068] Reference will now be made in detail to the described embodiments, examples of which are illustrated in the accompanying drawings.

[0069] The following description discloses some embodiments in detail, so that those skilled in the art can form a self-standing film including HARM-structures based on the present disclosure.Not all steps of the embodiments are discussed in detail, because many steps will be obvious to those skilled in the art based on this description.

[0070] For simplicity, in the case of repeated components, the item numbering will be maintained in the following exemplary embodiments.

[0071] Figure 1 A method for forming a free-standing film comprising a HARM-structure according to one embodiment is shown. Figure 1 In an embodiment, first a first part of the HARM-structure is deposited onto a porous filter, for example from a vapor phase, to form a film of the HARM-structure on the porous filter ( Figure 1 1).

[0072] The HARM-structured membrane is transferred from the porous filter to the frame to form a free-standing membrane of the HARM-structure attached to the frame ( Figure 1 2-4).

[0073] After the step of transferring the film of the HARM-structures onto the frame to form a free-standing film of the HARM-structures attached to the frame, a second part of the HARM-structures is deposited, for example from the vapour phase, onto the free-standing film of the HARM-structures attached to the frame to form a free-standing thin film of the HARM-structures attached to the frame ( Figure 1 5-6).

[0074] exist Figure 1 In the embodiment of the present invention, there is further shown a step of transferring the formed self-supporting film of the HARM-structure attached to the frame from the frame to a second frame, wherein the size of the second frame is smaller than the size of the frame, wherein the second frame is pushed through the self-supporting film of the HARM-structure attached to the frame to stretch the self-supporting film of the HARM-structure ( Figure 1 7).

[0075] Figure 3 An image showing possible defects on the film surface. The image was taken with an Olympus MX63L microscope. The arrows show the size of the defects in microns. These defects are dents and areas with less carbon nanotube material.

[0076] Figure 4 It is shown how protruding defects present in a porous filter are transferred to a thin film formed on the porous filter by depositing HARM-structures thereon. The defects manifest themselves as indentations containing less HARM-structure material.

[0077] Example 1 - Preparation of a free-standing film

[0078] In this example, different free-standing films attached to a frame were prepared using the following materials:

[0079] Material Porous filter MCE* frame Polymethyl methacrylate HARM structure Carbon Nanotubes

[0080] *MCE=Mixed Cellulose Esters

[0081] **Square frame, inner area 111.5mm×144mm, outer area 118.5mm×151mm

[0082] First, carbon nanotubes were synthesized in an aerosol laminar flow (floating catalyst) reactor using carbon monoxide and ferrocene as carbon source and catalyst precursor, respectively. The first portion of carbon nanotubes formed were deposited from the gas phase onto a porous filter at a total gas flow rate of 60 l / min (maximum gas velocity of 0.13 m / s) to form a carbon nanotube film on the porous filter. The gas temperature was about 60° C., and the first portion of carbon nanotubes was deposited until the carbon nanotube film had a transmittance of 95% of the energy of light per unit time incident vertically thereon when measured at a wavelength of 550 nm. The film thickness of the formed carbon nanotubes was 15-30 nm.

[0083] The formed carbon nanotube thin film is then transferred from the porous filter to a frame to form a carbon nanotube free-standing film attached to the frame. The frame has a rectangular shape with an opening in the middle.

[0084] Then, a second portion of carbon nanotubes was deposited from the vapor phase onto the carbon nanotube self-supporting film attached to the frame to form a carbon nanotube self-supporting film attached to the frame. The second portion of carbon nanotubes was deposited until the carbon nanotube self-supporting film had a transmittance of 87% of the energy of light per unit time incident vertically thereon when measured at a wavelength of 550 nm. The thickness of the film formed was 70 nm.

[0085] Additionally, a comparative example was prepared by preparing an otherwise similar free-standing film, but in which a second portion of the carbon nanotubes was deposited from the vapor phase onto the porous filter having the carbon nanotube film already formed thereon.

[0086] In order to evaluate the uniformity of the different films formed, the transmittance was measured as described in this specification. Based on the measurement results, the transmittance difference was calculated in the following manner:

[0087] Transmittance difference (%) = maximum transmittance (%) - minimum transmittance (%).

[0088] The results are shown in Table 1 below:

[0089] Table 1. Transmittance differences of samples

[0090] Transmittance difference (%) (measured at 550nm) Comparative Example 1.02 Carbon nanotube free-standing film 0.32

[0091] It can be seen from Table 1 that the transmittance difference of the carbon nanotube free-standing film is 0.32%.

[0092] Furthermore, the number of defects was measured as described in this specification. For these measurements, the following free-standing films attached to a frame were prepared using the following materials:

[0093]

[0094]

[0095] *Material MCE = mixed cellulose esters

[0096] **Round frame, inner diameter 21mm, outer diameter 37mm

[0097] The results are shown in Table 2 below:

[0098] Table 2. Defects in samples

[0099]

[0100] One sigma standard deviations are in parentheses.

[0101] The size of the defects recorded was greater than 13.0 μm for the comparative example and greater than 38.6 μm for the carbon nanotube free-standing film.

[0102] ***Number of samples measured and averaged.

[0103] As can be seen from Table 2 above, the carbon nanotube free-standing thin film has significantly fewer defects per square centimeter than the film of the comparative example.

[0104] It is obvious to a person skilled in the art that, as technology advances, this basic idea can be implemented in various ways. Therefore, the embodiments are not limited to the examples described above; instead, they may vary within the scope of the claims.

[0105] The embodiments described above can be used in any combination with each other. Several embodiments can be combined to form further embodiments. The method of forming a self-supporting film comprising a HARM structure or a self-supporting film comprising a HARM structure attached to a frame, or the use as disclosed herein, may include at least one embodiment described above. It should be understood that the above benefits and advantages may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those embodiments that solve any or all of the problems described, or those embodiments with any or all of the benefits and advantages. It will also be understood that reference to "one" refers to one or more of these items. The term "comprising" is used in this specification to indicate that the features or behaviors that follow are included, without excluding the presence of one or more additional features or behaviors.

Claims

1. A method for forming a free-standing film comprising a high aspect ratio molecular structure (HARM structure), characterized in that The method includes: a) depositing a first portion of the HARM-structure onto a porous filter to form a film of the HARM-structure on said porous filter, b) transferring the membrane of HARM-structures from the porous filter to a frame to form a free-standing membrane of HARM-structures attached to the frame, and c) depositing a second portion of the HARMS structure onto the free-standing film of the HARM-structure attached to the frame to form a free-standing thin film of the HARM-structure attached to the frame.

2. The method according to claim 1, wherein: What is formed is a free-standing film of a HARM-structure which exhibits a transmittance difference of at most 1% when calculated according to the following formula: Transmittance difference (%) = maximum transmittance (%) - minimum transmittance (%), in The maximum transmittance is the maximum value of the transmittance of the free-standing film of the HARM structure measured at a wavelength of 550 nm; The minimum transmittance is the minimum value of the transmittance of the free-standing film of the HARM-structure measured at a wavelength of 550 nm.

3. The method according to claim 2, wherein: The free-standing films of the HARM-structures exhibit a transmittance difference of at most 0.8%, or at most 0.7%, or at most 0.6%, or at most 0.5%, or at most 0.4%, or at most 0.35%, or at most 0.33%, or at most 0.30%, or at most 0.25%, or at most 0.20%, or at most 0.15%, or at most 0.10%, or at most 0.05%.

4. A method according to any one of the preceding claims, wherein: The HARM-structured self-supporting film has a thickness of 1 cm 2 Contains at most 10, or at most 5, or at most 3, or at most 1, or 0 defects.

5. A method according to any one of the preceding claims, wherein: The deposition of the first part of the HARM-structure and / or the second part of the HARM-structure is by vapour deposition.

6. A method according to any one of the preceding claims, wherein: Deposition of the first portion of the HARM-structures is continued until the HARM-structure film has a transmittance of 80-99%, or 85-98%, or 90-96%, or 92-94% of the energy of light normally incident thereon per unit time when measured at a wavelength of 550 nm.

7. A method according to any one of the preceding claims, wherein: The deposition of the second portion of the HARM-structure is continued until the free-standing film of the HARM-structure has a transmittance of 50-95%, or 55-93%, or 60-87%, or 65-86%, or 70-85%, or 75-80% of the energy of light normally incident thereon per unit time when measured at a wavelength of 550 nm.

8. A method according to any one of the preceding claims, wherein: The deposition of the first part of the HARM-structure is continued until the thickness of the film of the HARM-structure is 3-50 nm, or 5-45 nm, or 7-40 nm, or 10-35 nm, or 15-30 nm, or 20-25 nm.

9. A method according to any one of the preceding claims, wherein: The deposition of the second portion of the HARM-structure is continued until the thickness of the free-standing film of HARM-structure is 75-400nm, or 76-350nm, or 77-300nm, or 78-250nm, or 79-200nm, or 80-160nm, or 81-140nm, or 82-120nm, or 83-110nm, or 84-100nm, or 85-90nm.

10. A method according to any one of the preceding claims, wherein: The formed free-standing thin film of HARM-structures is set to have a predetermined transmittance value, and the deposition of the first portion of the HARM-structures is continued until the film of the HARM-structures exhibits a transmittance of 75-15%, or 65-35%, or 55-35% of the predetermined transmittance value.

11. A method according to any one of the preceding claims, wherein: The frame is made of polymer, quartz, titanium, graphite, silicon, silicon carbide, silicon nitrate, polysilicon, transition metal or alloy of transition metal.

12. A method according to any one of the preceding claims, wherein: The method also includes depositing at least one additional portion of a HARMS structure or other nanomaterial onto the free-standing film.

13. A method according to any one of the preceding claims, wherein: The HARM-structures are carbon nanostructures.

14. A method according to any one of the preceding claims, wherein: The method also includes transferring the formed self-standing film of the HARM-structure attached to the frame from the frame to a second frame, wherein the size of the second frame is smaller than the size of the frame, and wherein the second frame is pushed through the self-standing film of the HARM-structure attached to the frame to stretch the self-standing film of the HARM-structure.

15. A method according to any one of the preceding claims, wherein: The free-standing film is a film for extreme ultraviolet lithography; an extreme ultraviolet film; an extreme ultraviolet debris filter; or a film for an X-ray window.

16. A self-supporting film comprising a high aspect ratio molecular structure (HARM structure) attached to a frame, wherein: The free-standing film of the HARM-structure exhibits a transmittance difference of at most 1% when calculated according to the following formula: Transmittance difference (%) = maximum transmittance (%) - minimum transmittance (%), in The maximum transmittance is the maximum value of the transmittance of the free-standing film of the HARM structure measured at a wavelength of 550 nm; The minimum transmittance is the minimum value of the transmittance of the free-standing film of the HARM-structure measured at a wavelength of 550 nm.

17. The self-supporting film according to claim 16, wherein: The free-standing films of the HARM-structures exhibit a transmittance difference of at most 0.8%, or at most 0.7%, or at most 0.6%, or at most 0.5%, or at most 0.4%, or at most 0.35%, at most 0.33%, or at most 0.30%, or at most 0.25%, or at most 0.20%, or at most 0.15%, or at most 0.10%, or at most 0.05%.

18. The self-supporting film according to any one of claims 16 to 17, wherein: The HARM-structured self-supporting film has a thickness of 1 cm 2 Contains at most 10, or at most 5, or at most 3, or at most 1, or 0 defects.

19. The self-supporting film according to any one of claims 16 to 18, wherein: The thickness of the free-standing film is 75-400 nm, or 76-350 nm, or 77-300 nm, or 78-250 nm, or 79-200 nm, or 80-160 nm, or 81-140 nm, or 82-120 nm, or 83-110 nm, or 84-100 nm, or 85-90 nm.

20. The self-supporting film of any one of claims 16 to 19, wherein The free-standing film is a film for extreme ultraviolet lithography; an extreme ultraviolet film; an extreme ultraviolet debris filter; or a film for an X-ray window.

21. The self-supporting film according to any one of claims 16 to 20, wherein: The frame is made of polymer, quartz, titanium, graphite, silicon, silicon carbide, silicon nitrate, polysilicon, transition metal or alloy of transition metal.

22. The self-supporting film according to any one of claims 16 to 21, wherein: The HARM-structures are carbon nanostructures.

23. Use of a free-standing film according to any one of claims 16 to 22 in EUV lithography; as an EUV film; as an EUV debris filter; or as a film for an X-ray window.

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