Improved extreme ultraviolet pellicle with enhanced extreme ultraviolet transmission and method of producing thereof

Abstract

A method of enhancing extreme ultraviolet (EUV) transmission and reducing scattering of a carbon nanostructure pellicle film is disclosed. The method includes treating the carbon nanostructure pellicle film with at least one irradiation, which reduces the defects of the carbon nanostructure and strengthens the properties of the carbon nanostructure. Carbon nanostructure pellicle film with modified and enhanced properties for EUV lithography is also disclosed.

Description

IMPROVED EXTREME ULTRAVIOLET PELLICLE WITH ENHANCED EXTREME ULTRAVIOLET TRANSMISSION AND METHOD OF PRODUCING THEREOFCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to U.S. Provisional Application No. 63 / 541,992 filed on October 2, 2023, which is hereby incorporated by reference in its entirety.TECHNICAL FIELD

[0002] This disclosure generally relates to a thin film and a thin film device used in a semiconductor microchip fabrication and, more particularly, to an improved quality ultra-thin, ultralow density, nanostructured free-standing pellicle film with enhanced microstructures and extreme ultraviolet (EUV) transmission, said film and film device destined for EUV lithography.BACKGROUND

[0003] A pellicle is a protective device that protects a photomask (also referred to as a reticle) and is used in semiconductor microchip fabrication to reduce patterning defects brought by falling particles or minuscule particles on the photomask. The photomask may refer to an opaque plate with holes or transparencies that allow light to be reflected in a defined pattern, acting like a blueprint that will be printed on many wafers. Such photomasks are commonly used in photolithography and the production of integrated circuits. As a master template, the photomask is used to produce a pattern repetitively on a substrate, usually a thin slice of silicon known as a wafer in the case of semiconductor chip manufacturing.

[0004] Despite the adoption of state-of-the-art cleanroom and air filtration techniques, fall- on particles on the photomasks with unknown particle sources are still observed after exposure of photomasks in lithography, according to field reports in the semiconductor industry. Such particlecontamination, even a tiny amount, is often a significant problem in semiconductor manufacturing. It becomes a more prominent issue in advanced photolithography of much higher-resolution processes and microcircuits, increasing defect rates and affecting product yields as any nonnegligible particles may alter the printing patterns of semiconductor circuits on the chips, which have no built- in redundancy.

[0005] A photomask may be protected from undesired particles by an effective pellicle, a thin transparent film stretched over a frame (also referred to as a pellicle border with a central opening or aperture) that may be attached over the patterned side of the photom sk. The pellicle is close to but far enough away from the photomask, so moderate-to-small-sized particles that land on the pellicle will be too far out of focus to print.

[0006] Recently, the microchip manufacturing industry further realized that the pellicle might protect the photomask from damages and causes other than particles and contaminants. Early pellicle adoption has shown initial results in reducing defects and improving production yields.

[0007] Extreme ultraviolet (EUV) lithography is an advanced photolithography technology using a range of EUV wavelengths, for example, about 13.2 nm or often 13.5 nm. The EUV lithography enables semiconductor microchip manufacturers to pattern the most sophisticated features at 7 nm resolution and beyond and place many more transistors without increasing the size of substrates. EUV photomasks work by reflecting light, which is achieved by using multiple alternating layers of molybdenum and silicon. When an EUV light source turns on, the EUV light hits the pellicle film first, passes through the pellicle film, and then bounces back from underneath the photomask, hitting the pellicle film once more before it continues its path to print a microchip. Some EUV energy is absorbed during this process, and heat may be generated, absorbed, and accumulated within pellicles due to double EUV light passages. The temperature of the pellicle may heat up to anywhere from 500° Celsius to 1000° Celsius or above.

[0008] While heat resistance may be a desired trait, high transparency of the pellicle to EUV may also be desired to ensure the passing through of the incident light from the EUV light source and the reflected EUV light and light pattern from the photomask. This is one of the main reasons EUV pellicles are generally very thin, less than 200 nm, preferably less than 100 nm, or less than 40 nm thick.

[0009] In 2016, a polysilicon-based EUV pellicle was developed after decades of research and effort with only 78% EUV transmission (EUVT) on a simulated relatively low-power 175-watt EUV source. Due to greater transistor density demand, stringent requirements present further technical challenges to EUV pellicle developers for a higher transmission rate, lower transmission variation, higher temperature tolerance, and strong mechanical strength.

[0010] Carbon nanotubes (CNTs) are graphene sheets rolled into seamless concentric cylinder structures, including single-wall (or single-walled) carbon nanotubes (SWCNTs), doublewall (or double-walled) carbon nanotubes (DWCNTs), or multiwall (or multiwalled) carbon nanotubes (MWCNTs). High-quality CNTs often have a high carbon nanotube content in a carbon nanotube sheet (e.g., as high as 99% by mass or above). They may form pellicles with high visible light and EUV transmittance rates. Ultra-thin, ultra-low density CNT pellicle films have been reported with satisfactory lifetime.

[0011] However, as CNTs or graphene sheets are produced by methods and carbon sources selected from various hydrocarbon gases, their hexagonal honeycomb lattice microstructure defects in graphene structures may occur. Furthermore, a thin layer of carbonaceous material, i.e., adventitious carbon, generally exists for most air-exposed surfaces. Romen spectroscopy is frequently selected to analyze CNTs, CNT sheets, CNT yarns, and alternations, defects, or modifications of CNTs.SUMMARY

[0012] According to an aspect of the present disclosure, a specifically structured nanostructure film is disclosed. The nanostructure film includes a plurality of carbon nanotubes that are intersected randomly to form an interconnected network structure in a planar orientation, the intersected or interconnected network structure having a thickness ranging from a lower limit of 3 nm to an upper limit of 100 nm, and a light transmission rate from 50%, 70%, 80%, 90% or 95% and above at 550 nm wavelength and a EUV transmission rate from 75%, 80%, 90%, or 92% to 94% or above, 95% or above, up to 99%, in which the nanostructure film (e.g., nanotube structure) undergoes a flash light annealing, i.e., at least one flash of light, or a laser annealing, and presents structural or microstructural changes with improved overall hexagonal honeycomb lattices and / or EUV transmission rates. The preferred CNT pellicles may have further preference of having a plurality of carbon nanofibers with at least 50% of double-walled carbon nanotubes, at least 50% of single-walled carbon nanotubes, or at least 50% of three or more walled carbon nanotubes, with the rest filled with carbon nanofibers, including different number-walled carbon nanotubes, to account for the final 100% content. The present disclosure further includes CNT pellicle films with any combination of single-walled, double-walled, and multi-walled carbon nanotubes and other types of nanofibers. Such nanofiber structures may present higher crystallinity, perfected microstructures, or other properties (detailed below) upon the contemplated flash light annealing treatment, laser annealing, or any other forms of irradiation treatment, turning non-EUV lithography compatible or less EUV transmittable nanofiber film structure into an EUV lithography-eligible film, meeting the then industrial requirement and standards.

[0013] According to an aspect of the present disclosure, a pellicle is disclosed. The pellicle includes a pellicle border defining an aperture, at least one nanostructured film mounted to the pellicle border covering the aperture, the mounted nanostructured film being annealed by an electromagnetic wave, such as a flash(es) of light, laser energy (i.e., laser pulse) and having enhanced properties,including but not limited to EUV transmittance, film deflection, and reduced defects, compared to an unannealed or pre-annealed nanostructured film for EUV lithography.

[0014] According to one aspect of the present disclosure, flash light annealing or laser annealing applies a single flash of energy on a CNT pellicle film or a CNT pellicle device.

[0015] According to one aspect of the present disclosure, flash light annealing or laser annealing applies a series of flashes of energy on a CNT pellicle film or a CNT pellicle device.

[0016] According to another aspect of the present disclosure, a duration of flash light annealing or laser annealing for a surface of a pellicle film covered by an irradiation of the annealing ranges from a lower limit of 0.01 milliseconds (ms) to an upper limit of 1 seconds; a cumulative duration ranging from a lower limit of 0. 1 milliseconds to an upper limit of 10.0 seconds.

[0017] According to yet another aspect of the present disclosure, flash light annealing may deliver energy of 0.5-50 J / cm2directly at a pellicle film.

[0018] According to yet another aspect of the present disclosure, flash light annealing or laser annealing may deliver a power of 0.05-50 watts / cm2, up to 1,000 watts / cm2directly at pellicle film.

[0019] According to another aspect of the present disclosure, irradiation energy from a flash(es) of light or laser pulsation may increase the G band / D band intensity ratio in Raman spectra (i.e., IG / ID) of a nanostructure film.

[0020] According to another aspect of the present disclosure, an pellicle film’s improved IG / ID is at least 105% of an IG / ID of the pellicle film prior to receiving irradiation or electromagnetic wave energy by a method selected from at least flash light annealing or laser annealing.

[0021] According to another aspect of the present disclosure, an enhanced IG / ID by at least flash light annealing or laser annealing in some embodiments raises EUV transmission rates and / or reduces EUV scattering of a nanostructure film or nanofiber pellicle.

[0022] According to a further aspect of the present disclosure, flash light annealing or laser annealing treatment raises EUV transmission rates of a nanofiber structure from below 90% to above90%, below 92% to above 92%, or below 95% to above 95%. EUV transmission rates of nanofiber structures after flash light annealing or laser annealing are at least 0.3%, 0.6%, 1.0%, 2.0%, 5.0%, up to 10.0% higher than EUV transmission rates before the flash light annealing or the laser annealing.

[0023] According to yet another aspect of the present disclosure, in some embodiments, electromagnetic wave energy during a flash light annealing or laser annealing is applied directly or indirectly (i.e., through deflection or reflection of other objects, such as mirrors) to pellicle films or pellicles at one or both surfaces of the pellicle films. Exemplary electromagnetic irradiation light source includes but is not limited to an electromagnetic wave spectrum of visible light, laser light, infrared, or ultraviolet. The spectrum wavelength may range from 100 nm to 1 .0 mm.

[0024] According to one aspect of the present disclosure, a flash light or laser annealing device may be a standalone device or a part of an EUV scanner or have direct connections with an EUV scanner, such as within a lithography machine or lithography system or a semiconductor manufacturing production line, for delivery of freshly flash light or laser annealed pellicle films or pellicle devices to EUV scanners.

[0025] According to another aspect of the present disclosure, flash light or laser annealing of pellicle films or pellicles may occur remotely away from EUV scanners or semiconductor production sites.

[0026] According to one aspect of the present disclosure, flash light or laser annealing of a pellicle film is performed before EUV irradiation without or with limited atmospheric air exposure or without or with limited other non-inert gas exposure.

[0027] According to yet another aspect of the present disclosure, flash light or laser annealing of a pellicle film or pellicle may be performed in an open-air space, a vacuum chamber, a non-vacuum chamber, or a chamber under a reduced atmospheric pressure filled with one or more of gases, selected inert gases, or air. Exemplary inert gases include but are not limited to, argon, helium, neon, krypton, xenon, and radon.

[0028] According to another aspect of the present disclosure, the nanostructured film has an areal density of about 0.2 pg / cm2to about 6.0 pg / cm2, partially listed in FIG. 3 with corresponding transmission rates measured at 550 nm wavelength. For example, an areal density of 0.62 ug / cm2may result in a mean light transmission % of 93.833 with a standard deviation of 0. 197. In contrast, a higher areal density of 3.11 ug / cm2may result in a mean light transmission % of 72.900 with a standard deviation of 0.965, generally illustrating an inverse relationship between the areal density and the light transmission %.

[0029] According to one aspect of the present disclosure, a method of producing a pellicle film or a pellicle device for EUV lithography is disclosed. An exemplary method includes steps of producing a pellicle film and a pellicle, preferably by filtration method, mounting the pellicle film to a pellicle border or an intermediary border, performing a flash light annealing or laser annealing of the pellicle or pellicle film to enhance a ratio of G-band intensity over D-band intensity in a Raman Spectra (IG / ID) of the pellicle film on the pellicle border or the intermediary border, and optionally transferring the pellicle film from the intermediary border onto a pellicle border.

[0030] According to another aspect of the present disclosure, a method of performing EUV lithography is disclosed. The method includes annealing a pellicle by a flash or flashes of light or laser to raise IG / ID and then transmitting EUV radiation through the pellicle having an enhanced IG / ID and a raised EUV transmission.BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present disclosure is further described in the detailed description, which follows, in reference to the noted plurality of drawings by way of non-limiting examples of preferred embodiments of the present disclosure, in which like characters represent like elements throughout the several views of the drawings.

[0032] FIG. 1 illustrates a filtration method for forming a pellicle film followed by a flash light annealing step with an optional transferring step in accordance with an exemplary embodiment.

[0033] FIG. 2 illustrates a scanning electron microscope (SEM) image of a microstructure of a double-wall CNT (DWCNT)-dominant film in accordance with an exemplary embodiment.

[0034] FIG. 3 illustrates a correlation between areal densities of CNT nanostructure films and their light transmission rates measured at 550 nm in accordance with an exemplary embodiment.

[0035] FIG. 4 illustrates the changes of D-band intensity over G-band intensity (IG / ID) and light transmittance measured at 550 nm wavelength before and after flash light annealing of CNT films having a 550 nm wavelength transmittance of 72% in accordance with an exemplary embodiment.

[0036] FIG. 5 illustrates the changes of light transmittance measured at 550 nm wavelength and EUV (13.5 nm) and IG / ID of another set of CNT films having a 70% light transmittance measured at 550 nm before and after flash light annealing in exemplary conditions, e.g., vacuum or atmospheric air, in accordance with an exemplary embodiment.

[0037] FIG. 6 illustrates the changes of IG / ID for two individual CNT films having an 80% light transmittance measured at 550nm in accordance with an exemplary embodiment.

[0038] FIG. 7 illustrates the change of IG / ID of a CNT film by laser annealing in accordance with an exemplary embodiment.

[0039] FIG. 8 illustrates a typical Raman spectrum of CNT material.DETAILED DESCRIPTION

[0040] Through one or more of its various aspects, embodiments and / or specific features, sub-components, or processes of the present disclosure are intended to bring out one or more of the advantages as specifically described above and noted below.

[0041] A pellicle film may refer to a thin transparent film that protects a photomask during semiconductor microchip production. A pellicle contemplates a protective device with a border or a frame having a central opening, aperture, or window, and a pellicle film. Both border and aperture are covered by a continuous thin and transparent film, i.e., a pellicle film, on the top of at least a portion of the border and a portion of the aperture, preferably the entire aperture. The center portion of such a thin film extending the aperture is free-standing. The pellicle may act as a dust cover or a filter that prevents particles and contaminants from falling onto an object(s) below the pellicle. In extreme ultraviolet (EUV) lithography, an EUV pellicle functions as a particle filter or a fine particle filter to protect a photomask, also referred to as a reticle, during advanced microchip production. Further, the pellicle may be sufficiently transparent to allow the light transmission necessary to perform lithography. Higher light transmission rates may be desired to achieve more effective lithography. For most EUV lithography applications, an 80% EUV transmission rate from a pellicle may be acceptable. The high-resolution EUV lithography at 5 nm or below, a high-energy EUV scanner, or a high or hyper numeric aperture EUV lithography scanner may prefer an EUV transmission rate of 90% or above, 92% or above, 94% or above, 96% or above, up to 99%.

[0042] Further, pellicles for EUV lithography may call for a large (e.g., equal to or larger than 110 mm x 140 mm, depending on the then specified photomask sizes) free-standing, thin-film material with extreme and unique properties. Besides high transparency to EUV radiation, any unexpected film rupture during microchip production may interrupt ongoing manufacturing processes, leading to possible debris decontamination of the entire scanner due to a damaged pellicle, changing or cleaning photomasks and reflective mirrors, losing microchip production, etc. High- quality EUV pellicle films with minimum or no defects in CNTs may lead to achieving high- temperature resistance and longer pellicle usage lifetime. Given the stringent requirements, effective EUV pellicles have been conventionally difficult to produce to meet the criteria.

[0043] In this aspect, carbon nanotubes and equivalent nanofibers may be used as starting materials to create pellicles for this EUV lithography application due to their excellent thermal and mechanical properties and capability to form porous films. Further improvement of CNT pellicles is contemplated in one or more of the embodiments of this disclosure.Carbon Nanotubes and Carbon Nanotube Films

[0044] Carbon nanotubes (CNTs) or carbon nanofibers, as often referred to herein, are long tubes with small diameters typically measured in nanometers. They have a high aspect ratio of length vs. diameter in a range generally preferred above about 100:1, which may be above about 1000: 1. Another preferred aspect ratio may be at least approximately 10,000: 1. CNTs are made up of one or more graphene sheets rolled up into a concentric structure. A graphene sheet is a collection of carbon allotrope arranged in a single layer in a hexagonal lattice structure. Each graphene sheet of a CNT is regarded as a wall of a CNT. A single-wall CNT (SWCNT) is made of a single graphene sheet. A double-wall CNT (DWCNT) is made of two graphene sheets. Lastly, a multiwall CNT (MWCNT) has multiple graphene sheets. Other types of CNTs may include, but are not limited to, coaxial nanotubes having at least one graphene wall and one non-graphene wall, conical carbon nanotubes, and closed carbon nanotubes. Other carbon allotropes may also form sheets with excellent properties for pellicle films. For CNTs, they may exist substantially pure in one type or often in combination with other types with respect to the number of CNT walls. The CNTs may also exist individually, separated from others, or form bundles. A bundle may include the same type or different types of CNTs, such as SWCNT with DWCNT, SWCNT with MWCNT, etc. Within a bundle, CNTs may have different lengths and diameters. Each bundle, having two or more CNTs, may be aligned in parallel, at least for a portion of their entire lengths. For simplicity and convenience, CNTs in this application may refer to different types of CNTs, for example, different numbers of walls, CNTs existing individually or in bundles. According to exemplary aspects, nanofibers may beinterchangeable with CNTs or nanofibers having at least one graphene wall and one non-graphene wall.

[0045] As used herein, nanofiber may exemplarily refer to a fiber having a diameter of less than 1pm. Nanofiber and nanotube may be used interchangeably and may encompass SWCNTs, DWCNTs, MWCNTs, coaxial CNTs, and other carbon allotropes in which carbon atoms are linked together to form a final cylindrical structure.

[0046] A CNT may be intersected with one or more other CNTs. Together, many CNTs could interconnect and form a mesh-like microstructure film. One exemplary embodiment may include a free-standing microstructure thin film, of which an area of the thin film has no supporting material or substrate on either side of the thin film. While such formation is possible, it may not be guaranteed in every trial, especially for making an ultra-thin film with high transparency and other properties intended for EUV lithography pellicles. Defects in graphene sheets of CNT walls may exist.

[0047] Further, among several possible methods to fabricate free-standing films, a filtrationbased approach was utilized to produce membrane films from small -size films to sufficiently large films with uniform film thickness or EUV transmittance for EUV lithography. Films having a uniform thickness generally correlate to even light transmission. This filtration -based method allows for the quick manufacturing of films not only of CNTs but also other high aspect ratio nanoparticles and nanofibers, such as boron nitride nanotubes (BNNT) or silver nanowires (AgNW). Since this approach separates the nanotubes or nanoparticle syntheses and the film manufacturing processes, a variety of nanofibers produced by virtually any method may be used. Different types of nanotubes (SWCNT, DWCNT, MWCNT, carbon allotropes, or coaxial) may be mixed in any desired ratio. As filtration can be a self-leveling process in the sense that non -uniformities of film thickness during the filtration process are self-corrected by the variations of local permeability and, therefore, a highly desirable film formation process, it is also a promising candidate for the production of highly uniform films.

[0048] An image of a CNT film with a majority of DWCNTs (i.e., 50% or more) is exemplarily provided in FIG. 2. More specifically, a scanning electron microscope image of the CNT film, with an interconnected and intersected network structure, is exemplarily provided in FIG. 2. As illustrated in FIG. 2, the CNTs may form bundles, and the intersected network structure may exhibit high porosity.Carbon Nanotube Synthesis and its Raman Spectrum

[0049] CNTS may be synthesized by different methods, depending on product types, precursors, heating source, reaction time, temperature, and atmosphere. The most common methods include but are not limited to, arc discharge, electrolysis, laser ablation, chemical vapor deposition (CVD), flame synthesis, mechano-thermal, etc. The well-known CVD methods have evolved to plasma-enhanced PE-CVD, aerosol CVD (AACVD), water-assisted WA-CVD, oxygen-assisted CVD, catalytic CVD, etc.

[0050] These CNT production methods utilize one or more carbon sources, such as acetylene (C2H2), ethylene (C2H4), or other hydrocarbons, in a reaction chamber with at least one catalyst and a temperature ranging from 350 to l,000°C or above.

[0051] Within a CVD reaction chamber, a catalyst may be in a free-floating form within the reaction chamber during the synthesis (FC-CVD). Under pyrolysis of hydrocarbon gas(es), FC-CVD is applied to produce nanofiber sheets. Alternatively, FC-CVD, under different growth conditions, may produce nanofibers, which can be collected as CNT powers for later dispersion and filtration to produce pellicle films, as described below.

[0052] Other commonly deployed CVD synthesis methods start with a catalyst deposition on a substrate, e.g., a silicon wafer, by electron-beam (E-beam) deposition, sputtering, atomic layer deposition, laser-assisted CVD, and plasma-enhanced CVD. A collection of individual nanofibers are vertically aligned on the substrate to each other, with one end of the nanofibers attached to thesubstrate, like a forest, frequently referred to as a CNT forest. They may be detached from the substrate and harvested as CNT powders for CNT pellicle films.

[0053] Regardless of selected methods of CNT syntheses, a vast number of honeycomb microstructures within a single graphene sheet or massive collections of graphene sheets in a nanofiber film present tremendous challenges for perfection. Non-honeycomb defects may be inevitably incorporated into CNTs, such as the known Stone-Wales defects, single or multiplevacancy defects, line defects, carbon or foreign adatoms, substitutional impurities, etc. Besides the above-mentioned atomic-level defects, macroscopic disorders of CNTs, such as curvature, twist, and hetero-junction kink, may more or less affect the crystallinity of CNTs and cause property changes in intended applications, including CNT pellicle films.

[0054] For decades, research has focused on these so-called lattice defects as these lattices form the fundamental honeycomb structures of graphenes, the rolled-up walls of CNTs. To detect defects at molecular levels, Raman spectroscopy may be used to analyze CNT or graphene material. Raman spectroscopy may refer to a non-destructivve spectroscopic technique to measure, record, and determine molecular vibrations in principle. More specifically, in Raman spectroscopy, an incident laser light may be directed to a target to induce scattering, which is detected, collected, and recorded by Raman shift (cm ) and intensities (peaks) in a chart (Raman spectrum).

[0055] Different material exhibits different Raman spectra. For CNT mixtures, different CNT purities may affect their Raman spectra. CNTs with different diameters may often have different amounts of defects with different Raman spectra or IG / ID. Larger diameter CNTs or MWCNTs tend to have more defects compared to smaller diameter CNTs or SWCNTs or DWCNTs.

[0056] FIG. 8 is a typical exemplary Raman spectrum of CNTs. The G-band, sometimes also referred to as G-peak, with a peak around 1590 cm4, derives from the in-plane vibration of the six- membrane ring (honeycomb lattice) in CNTs and represents the majority of carbon-carbon bonds (shown as a high and sharp peak). The D-band, referred to as D-peak on other occasions, with a peakaround 1350 cm’1, derives from the defects at the atomic level with a broader and very shallow base compared to the G-band. A high-quality (or defect-less) honeycomb structure typically has a higher G-peak and lower D-peak on Raman spectra or a higher G-band intensity over D-band intensity ratio in a Raman spectrum (IG / ID) compared to a similar honeycomb structure with apparent defects.

[0057] However, other factors may also affect Raman data acquisition, such as background noise / vibrations of a measuring system, a minute amount of surfactant in CNT suspension or surfaces, and selected substrates to support CNT material for Raman analyses (i.e., silicon vs. metal substrate, etc.). Presence of contaminating catalysts used during CNT syntheses and surface aliphatic compounds of CNTs acquired over time may also affect the Raman data.Flash Light and Laser Annealing

[0058] Flash light and laser annealing may refer to applying a light treatment in a short time (or duration) to a material or material surface, one side or both sides, to alter the given material’s physical and sometimes chemical properties to increase its ductility and reduce its hardness. Either flash light or laser annealing starts with a light source, administrates its energy onto a material to raise the temperature of such material rapidly for a very short duration, and then lets the material cool off. Addional mechanism of action for the observed pellicle film improvement is possible depending on conditions and / or environment when the annealing happens.

[0059] A flash light or laser annealing may apply a single flash of light or a series of light flashes to a desired target. Each flash moment may cover a portion of a pellicle film, an entire surface of a pellicle film, or a pellicle.

[0060] In one instance, one or more light flashes or laser pulses may cover a side (i.e., a surface) of an entire pellicle film with little irradiation variation for even annealing results. In another instance, one or more light flashes or laser pulses may uniformly irradiate one side and / or the oppositeside of a pellicle film. For flash light annealing and laser annealing with two or more flash light irradiations and laser pulses, changing, adjusting, or rotating the target film positions in reference to the light source may reduce or avoid possible irradiation bias or unevenness caused by a single flash of light or a single pulse of laser.

[0061] A light source in flash light annealing or laser annealing may emit a visible spectrum, an infrared spectrum, a laser, or an electromagnetic wavelength. Flash light annealing or laser annealing may apply a single wavelength or multiple wavelengths from a single or multiple energy sources. Flash light annealing or laser annealing may apply a light flash or a pulse of laser with a narrow spectrum, a broad spectrum, or a spectrum range selected from 200 nm to 800 nm, from 50 nm to 5 pm, 10 nm to 200 nm, 5 pm to 1 mm, or a combination thereof.

[0062] A light source may be configured to emit electromagnetic waves evenly at a target material or material surface directly or optionally by a delivery system. An environment carrying out such flash light or laser annealing may be designed in a way to avoid bouncing of light, which may cause uneven annealing results of a film. Furthermore, an appropriate power or energy may be selected to prevent burning, ablating, or sublimating any portion of CNTs, which may introduce new defects to any target film.

[0063] Flash light or laser annealing time or duration is short, preferably in sub-millisecond to a low single-digit second. The irradiation time of a single flash or pulse may be as short as 0.01 ms, 0.1 ms, 0.5 ms, 1.0 ms, 10 ms, 60 ms, 150 ms, 250 ms, and 400 ms and may not exceed 1 second. Cumulative light flashes or pulses may have an irradiation time ranging from 0.1 ms to 1 second, 5 seconds, or 10 seconds. Irradiation by flashes of light or pulsations of laser may be a single flash of an electromagnetic wave or an accumulation of two or more pulsations of one or more electromagnetic waves (i.e., the same or different electromagnetic wavelengths). Light energy from a total of at least 0.5 J / cm2, 1.0 J / cm2, 10 J / cm2, or 30 J / cm2, but not exceeding 50 J / cm2, may beapplied. Alternatively, electromagnetic waver power may be selected from 0.05 watts / cm2to 1000 watts / cm2.

[0064] Flash light or laser annealing may be applied or re-applied to a pellicle film or device prior to subjecting the annealed pellicle film or pellicle to an EUV lithography process or post an EUV lithography process to recover loss of IG / ID according to one or more aspects of the present disclosure. Additionally, the applied irradiation energy, cumulative treatment time, and the selected wavelengths may be determined by the target material density, porosity, thickness, and microstructural geometries.

[0065] The target surface temperature may be raised to 100°C and above, 300°C and above, 500°C and above, 600°C and above, 650°C and above, 700°C and above, 800°C and above, 900°C and above, or l,000°C and above. It may also be 3,000°C or less, 2,500°C or less, 2,000°C or less, l,800°C or less, l,700°C or less, l,600°C or less, l,500°C or less, or l,400°C or less.

[0066] Multiple irradiation energy from flashes of light or laser pulses may be applied in a fixed interval or variable intervals for optimal changes of IG / ID and / or EUV transmittance enhancement. Energy and / or power for each irradiation in a series of irradations may be arranged in an incremental regiment, a descending regiment, or a combination thereof.

[0067] A low thermal expansion material may be preferred for a pellicle border to avoid overexpansion or shrinking of a pellicle film mounted on the pellicle border, causing wrinkles or folds in the pellicle film.

[0068] Flash light and laser annealing may occur in a vacuum, a chamber filled with one or more inert gases, or atmospheric air.

[0069] Exemplary inert gases include but are not limited to argon, helium, neon, krypton, xenon, and radon. Exemplary hydrocarbon gases include but are not limited to methane, ethane, propane, butanes, pentanes, hexane, and heptane.

[0070] Flash light or laser annealing chamber or vacuum chamber may be a part of an EUV scanner. It may directly connect with an EUV scanner as a part, an accessory, or an attachment of an EUV-based microchip production line. It may also be stand-alone for performing an annealing treatment near a scanner or at a remote site.

[0071] However, aspects of the present disclosure are not limited thereto, such that different flash light or laser annealing operations / methods may be performed or a combination of annealing operations may be performed. The term flash light and laser annealing may include further aspects and broader interpretations in various technical fields and industries applicable to or related to the current disclosure. One or more present innovative contributions herein arise for the material science and semiconductor fields.Film Formation and Flash Light Annealing

[0072] An ultra-thin and ultra-low density CNT pellicle film may be produced, followed by a flash light or laser annealing process in accordance with exemplary embodiments of the current disclosure.

[0073] FIG. 1 illustrates a filtration method for forming a pellicle film, as shown in FIG. 2, followed by a subsequent flash light or laser annealing treatment in accordance with an exemplary embodiment.

[0074] Another embodiment of this disclosure may further include any pellicle films produced, to be produced, processed, or to be processed by all means prior to flash light or laser annealing. Furthermore, another embodiment of the present disclosure includes any other pellicle films with various CNT surface modifications, including but not limited to coating or other means of disposing of one or more metal elements, metal oxides, CNT surface modifiers, or a combination thereof on CNT films and subjects them to flash light or laser annealing.

[0075] As illustrated in FIG. 1, a free-standing carbon nanotube-based pellicle film may be produced via a filtration-based method. In Operation 101, catalysts are removed from carbon nanotubes (CNTs) that are to be used to form a water-based suspension. In an example, prior to dispersion into a suspension, the CNTs may be chemically purified to reduce a concentration of catalyst particles to less than 1% wt., less than 0.5% wt., or preferably less than 0.2% wt, which may be measured by, for example, thermogravimetric analysis. Removal of the catalysts is not limited to any particular process or procedure, such that any suitable process or method may be utilized to achieve a desirable result.

[0076] In Operation 102, a water-based suspension is prepared using the purified CNTs, such that the purified CNTs are evenly dispersed in the water-based suspension. When preparing one or more CNT suspensions, carbon nanotube material can be mixed with a selected solvent to distribute nanotubes uniformly in a final solution as a suspension. Mixing can include mechanical mixing (e.g., using a magnetic stir bar and stirring plate), ultrasonic agitation (e.g., using an immersion ultrasonic probe), or other methods. In some examples, the solvent can be a protic or aprotic polar solvent, such as water, isopropyl alcohol (IPA), and aqueous alcohol mixtures, e.g., 60%, 70%, 80%, 90%, 95% IPA, N-Methyl-2-pyrrolidone (NMP), dimethyl sulfide (DMS), and combinations thereof. In another example, a surfactant can also be included to aid the uniform dispersion of carbon nanofibers in the solvent. Examples of surfactants include but are not limited to anionic surfactants. Exemplary surfactants include but are not limited to sodium dodecyl sulfate (SDS), sodium cholate, Triton X- 100, Tween 20, and Tween 80.

[0077] Carbon nanofiber pellicle films are generally formed from one of MWCNTs, DWCNTs, or SWCNTs. A carbon nanofiber pellicle film may also include a mixture of different types of CNTs (i.e., SWCNTs, DWCNTs, and / or MWCNTs) with a variable ratio between the different types of CNTs. Other types of CNTs may also be used to produce CNT films by filtration and other known and contemplated methods.

[0078] Each of these three common carbon nanotubes (e.g., MWCNT, DWCNT, and SWCNT) has different properties. In one example, single-wall carbon nanotubes or single-wall and double-wall carbon nanotubes can be more conveniently dispersed in a solvent (i.e., with the majority of nanotubes suspended individually and less adsorbed onto other nanotubes) for subsequent formation into a sheet of randomly oriented carbon nanotubes. This ability of individual nanotubes to be uniformly dispersed in a solvent can, in turn, produce a more planarly uniform nanotube film formed by removing the solvent from the suspended nanofibers. This physical uniformity can also improve the uniformity of other properties across the film (e.g., transparency and scattering to irradiation, mechanical strength upon pressure changes, and lifetime / durability test).

[0079] In an example, the water-based CNT suspension in Operation 102 may have at least above 85% purity of SWCNTs. The remaining may be a mixture of DWCNTs, MWCNTs, and / or a catalyst. In other examples, a dispersed CNT suspension with various ratios of different types of CNTs may be prepared, such as about 20% / 75% DWCNTs / SWCNTs, about 50% / 45% DWCNTs / SWCNTs, about 70% / 20% DWCNTs / SWCNTs, with MWCNTs accounted for the remaining. A mixture of 10% or more MWCNT and a blended DWCNT and SWCNT at various DWCNT / SWCNT percentage ratios may be prepared and subjected to the same filtration process of forming nanofiber structures. In an example, anionic surfactants may be utilized as the dispersants in the suspension to enhance the uniform dispersion of different types of CNT mixtures.

[0080] In Operation 103, the CNT suspension is further purified to remove the aggregated or agglutinated CNTs from the initial mixture. In an example, different forms of CNTs, undispersed or aggregated vs. fully dispersed, may be separated from the suspension via centrifugation. Centrifugation of surfactant-suspended carbon nanotubes may aid in decreasing the turbidity of the suspension solution and ensuring a complete dispersion of the carbon nanotubes in the final suspension solution before going into the next filtration step. However, aspects of the disclosure are not limited thereto, such that other separation methods or processes may be utilized. According toexemplary aspects, Operation 103 may be optionally performed or performed as a necessary step in the formation of the pellicle film.

[0081] In Operation 104, any CNT suspension, preferably the CNT supernatant after a separation procedure from Operation 103, is filtered through a filtration membrane to form a CNT nanostructure film, a continuous sheet of film of intersecting CNTs.

[0082] In an example, one technique for making the CNT film uses water or other fluids to place nanotubes in a random pattern on a filter, often a flat filtration membrane. The evenly dispersed CNT-containing mixture is allowed to pass or is forced to pass through the filter, leaving a nanofiber structural layer on the surface of the filter. The size and shape of the resulting films are determined by the size and shape of the desired filtration area of the filter, while the thickness and density of the films are determined by the quantity of nanofiber material applied during the filtration process and the permeability of the filtration membrane to each ingredient of the input material, as the non- permeable ingredient is captured on the surface of the filter. If the concentration of nanofibers dispersed in the flow-through filtration fluid is known, the mass of nanofibers deposited onto the filter can be determined from the amount of such fluid that passes through the filter, and the film’s areal density is determined by the nanofiber mass divided by the total filtration area. And filtration area of the filter may be the same or smaller than the size of the filter, depending on the filter’s underlying supporting structure. The selected filter is generally not permeable to any CNTs.

[0083] The filtration-formed CNT film may be a combination of SWCNT, DWCNT, and / or MWCNT in differing compositions. Carbon nanofibers may intersect randomly to form an interconnected network structure in a planar orientation as a thin CNT film.

[0084] In Operation 105, the resulting CNT film is then separated from the filtration membrane, starting from a first edge of the CNT film toward a second edge. When detached fully from the filtration membrane, the nanofiber film is ready for the next operation, either Operation 106 A or Operation 106B.

[0085] In Operation 106A, the detached CNT film is harvested onto a solid substrate, such as a frame, sometimes referred to as a harvesting frame, a harvester frame, or an intermediary frame, all having a central opening or aperture.

[0086] Alternatively, in Operation 106B, the CNT film may be harvested and mounted to a pellicle border. The CNT film may cover the entire aperture to form a pellicle or pellicle device, ready for EUV photolithography. The detached CNT film may be mounted on any frame (e.g., a metal frame, silicon frame, quartz frame, or a pellicle border) with an opening of as small as 5 mm x 5 mm. A much larger film, at least 110 mm x 140 mm, is preferred, serving as a full-size pellicle film for EUV lithography. CNT film characterization, such as an optical light transmittance and / or transmittance uniformity (or variation) test, EUV transmittance and / or transmittance uniformity (or variation) test, mechanical strength, deflection test, permeability test, deflection at constant pressure or during simulated scanner pumping down conditions, lifetime test, particle test, may be performed. Based on current industry standards, a full-size pellicle for EUV lithography scanning may specify an ultra-thin, free-standing film generally larger than 110 mm x 140 mm. A full-size pellicle may be referred to as a full-field pellicle. A more advanced pellicle may have its aperture size doubled, i.e., at least 220 mm x 140 mm or 110 mm x 280 mm, for future high NA EUV lithography.

[0087] A pellicle frame or intermediary frame referred to herein may tolerate high- temperature treatments to sustain high-temperature annealings. Furthermore, it may have a low thermal expansion coefficient to avoid stretching or cause stretching of the nanofiber films mounted on itself. Exemplary frame material can be selected from silicon dioxide, commonly known as quartz, silicon carbide, etc.

[0088] In Operation 107, a CNT film on a frame, pellicle border, or intermediate transferring frame receives at least one flash or pulse of light, i.e., flash light or laser annealing. Exemplary flash light or laser annealing is conducted in atmospheric air, a closed chamber, or a vacuum chamber. However, aspects of the present disclosure are not limited thereto, such that various annealingtreatment methods may be conducted at room temperature, elevated temperatures, for a defined short period of time, and by different light sources, e.g., different electromagnetic wavelengths or spectra.

[0089] A flashlight or laser treatment may last as short as 0.01 millisecond, up to 1 second in a single flash, or less than 10 seconds of cumulative flashes or pulsations.

[0090] In another example, flash light or laser annealing may be performed in ambient air, a chamber, or a vacuum. The chamber may be filled with one or more inert gas(es). Any flash light and laser annealing variations, such as uneven energy or power disposed on a pellicle film, or uneven energy received at the pellicle film, may cause, for example, film wrinkles, focal film thickening or thinning, or even premature film breakage. Any of these events or changes may alter film light transmission rates, worsen transmission variation or uniformity, weaken film mechanical strength, or shorten film lifetime.

[0091] After annealing, a pellicle film may be ready for EUV lithography or further surface modification, including coating by at least one of the physical and chemical vapor depositions and / or chemical synthesis to add at least one or more “walls” on exterior sides or surfaces of CNTs, turning CNTs into coaxial nanofibers or nanotubes. Coating may apply one or more metal elements, metal oxides, CNT surface modifiers, or a combination thereof.

[0092] In Operation 108, the flash light or laser-annealed CNT film or nanofiber film mounted on an intermediary frame is transferred onto a pellicle border or pellicle frame.

[0093] A flash light or laser annealed film may be further analyzed by, including but not limited to, a visible light (e.g., 550 nm wavelength) and EUV transmission measurement, visible light and EUV transmission variation measurement, coating, mechanical tension measurement, and adjustment, or further transferred.Pellicle Film Enhancement Post Flash Light Annealing

[0094] According to exemplary aspects, increased porosity or transparency of material may correlate to light transmission rates through the material. However, transmission rates for a selected material measured by a given light source in a visible wavelength are different from the transmission rates of extreme ultraviolet (EUV). For example, a CNT film produced from Operation 101 to Operation 106 A or 106B, without Operation 107, having approximately 80% transmission rate when measured at a 550 nm wavelength, may yield a transmission rate at EUV 13.5 nm of about 94%. This observation and reports from others lead to difficulties and uncertainties in predicting and correlating transmission rates for a given material at selected visible and EUV wavelengths. Without further experimentation, it may be challenging to establish the correlations between the transmission rates at these wavelengths. Upon additional treatment or modification imposed on the pellicle film, the predictability of such correlations will become even more difficult.

[0095] An exemplary embodiment of the present disclosure covers flash light or laser annealing-treated CNT pellicle films, having EUV transmission rates and / or visible light transmission rates elevated and / or an EUV transmission scattering rates lowered compared to untreated CNT pellicle films.

[0096] In an example, a CNT pellicle film having a 40% or 50% light transmittance at 550 nm may have an EUVT of 81% or 84%, respectively (without any treatment), or an EUVT of 89% or 91%, respectively, after receiving a flash light annealing regiment, which represents an EUVT gain of 8.0% or 7.0%, respectively.

[0097] In another example, a CNT pellicle film having a 70% or 80% light transmittance at 550 nm may have an EUVT of 93.5% or 96.5%, respectively (without any treatment), or an EUVT of 95% or 97%, respectively, after a separate flash light annealing treatment. This EUVT gain of 1.5% or 0.5%, respectively, is smaller than an EUVT gain from a CNT pellicle film having a higher visible light transmission, such as 40% or 50%.

[0098] Yet in another example, a flash light annealing may gain a minimum EUVT of 0.3% compared to pre-flash light annealing EUVT. As most material absorbs or reflects EUV, a high EUV transmissible material is difficult to find for EUV lithography applications. Once found, any additional EUVT enhancement of a given material presents new challenges. An EUVT gain, such as, at little as 0.3%, could provide precious assistance in lithography and semiconductor production yield.

[0099] The annealed CNT pellicle films exhibit little changes in their appearance or mechanical strength while their EUV transmission rates improve. Further, EUV transmission variation (i.e., differences of multiple EUV transmission rates measured at various locations of the same pellicle film) may remain unchanged or have little change after flash light annealing. These features provided by the embodiments of the present disclosure add new values to and broaden the utility of unannealed CNT pellicles.

[0100] Furthermore, any CNT film defect reduction, demonstrated by the measurement results of G-band intensity over D-band intensity by Raman Spectroscopy (IG / ID), i.e., the IG / ID increases, may play a significant role in pellicle film's lifetime. An exemplary IG / ID gain is at least 5% post-flash light or laser annealing compared to IG / ID before the flash light or laser annealing.

[0101] While the exemplary embodiments of the present disclosure meet or exceed EUV pellicle specifications, including, but not limited to, EUV transmission rate, EUV transmission evenness, deflection rate, and mechanical strength of pellicle films under pressure changes, the exemplary embodiments also provide a method to treat pellicle films other than CNT pellicle films or majority DWCNT pellicle films, which may be inferior to present or then industrial standards, and enhance their properties to meet or exceed minimum EUV pellicle specifications. For example, a film with an EUV transmission rate of less than 90% may exceed a transmission rate of 90%, 92%, or even higher than 95% after applying one or more aspects of the present disclosure.

[0102] This constitution of the exemplary pellicle film provides an improved ultra-thin pellicle film with strengthened microstructures, allowing for high EUV transmission rates (e.g., greater than 70%, 80%, 85%, 90%, or 92%) and sustained lifetime while being extremely temperature resistant (e.g., resistant to temperatures above 500°C) and mechanically robust to sustain humans and robotic maneuvers and disturbances, including but are not limited to packaging, shipping, atmospheric pressure fluctuations at low and high altitude, and pressure changes during EUV scanner pumping down and venting. In an example, a minimum EUV transmission rate may be a value of 80% and a preferred EUV transmission rate of 90% or greater.

[0103] FIG. 4 shows exemplary flash light annealing effects measured by Raman spectroscopy. Samples A and B of the exemplary CNT films having 72.1% and 72% transmission rates measured at 550 nm wavelength, respectively, were treated by flash light under vacuum, and Samples C and D of the exemplary CNT films having 72.1% and 72.2% transmission rates measured at 550 nm wavelength, respectively, were flash light annealed in atmospheric air. Samples A and B have significantly increased IG / ID - the mean values have increased by 37.0 and 29.9, or 73.56% and 63.89%, respectively. Samples C and D show less IG / ID gains - the mean values increased by 7.2 and 3.7, respectively, or 14.26% and 7.59%, respectively. The transmission rates measured by 550 nm wavelength are also increased. Samples A and B’s 550 nm transmission rates increase from 72.1% and 72% to 73.4% and 74.2%, respectively, which may indicate a higher magnitude of EUV transmission rate increases. Samples C and D’s 550 nm transmission rates increase from 72.1% and 72.1% to 72.8% and 72.8%, respectively. Both in-air and in-vacuum annealing by a flash(es) of light reduces CNT lattice defects and increases the pristinity of CNTs; the in-vacuum flash light annealing presents further advantages over the in-air flash light annealing.

[0104] FIG. 5 shows other exemplary flash light annealing results based on three CNT films(i.e., Sample Al, Sample Bl, and Sample Cl) from the same sample preparation batch having about a 70% 550 nm light transmission rate (e.g., 69.44% for Sample Al) with an average IG / ID of 14±0.39.Sample Al was flash light annealed in a vacuum; Sample Bl was flash light annealed in atmospheric air; Sample Cl was the untreated control. After a 5-flash light annealing treatment (i.e., 5 flashes of light), the IG / ID mean values of Sample Al were increased by 29.5 or 210% in a in-vacuum flash light annealing; and the IG / ID mean values of Sample Blwere increased by 3.8 or 27.1% in an in-air flash light annealing. The transmission rates measured at 550 nm demonstrated an increase from 69.44% to 72.66% for Sample Al (i.e., 3.22% increase), while no meaningful 550 nm transmission change was shown for Sample Bl, compared to an unannealed CNT film.

[0105] Comparing the results from FIGS. 4 and 5, the in-vacuum flash light annealing demonstrates its effectiveness in improving 550 nm light transmission and CNT pristinity than the in-air flash light annealing.

[0106] Also, from FIG. 5, the effects of flash light annealing on EUV transmission rates exhibit similar patterns of 550 nm transmission rate shift and the IG / ID increase. The flash light annealing in a vacuum showed an increase of EUVT from 91. 68% to 94.44%, a net gain of 2.76% EUVT, while the flash light annealing in air has the EUVT enhancement from 91.68% to 92.9%, a net 1.22% improvement. There was EUV scattering improvement, a small decrease of 0.03% from flash light annealing in a vacuum or 0.01% from flash light annealing in air. The trend of EUVT changes correlates to the direction of IG / ID changes.

[0107] FIG. 6 shows another exemplary embodiment of the present disclosure. CNT films, having an 80% 550 nm light transmission rate and an average IG / ID of 14±0.39, were annealed or irradiated by a different number of light flashes from separate light sources, delivering different amounts of energies. CNT film Sample A2 was irradiated by one flash from a first light source in a vacuum, yielding a mean IG / ID increase of 47.3 or 228.5% (the post-annealing IG / ID value is 328.5% of the pre-annealing IG / ID value). CNT film Sample B2 was irradiated by fifteen flashes from a second light source in a vacuum as well, yielding a mean IG / ID increase of 43.0 or 162.3% (the post-annealing IG / ID value is 262.3% of the pre-annealing IG / ID value). The testing results showed IG / ID surges under in-vacuum flash light annealing conditions.

[0108] FIG. 6 further embodies another aspect of the present disclosure, comparing one strong light flash from high energy or power source to fifteen weak light flashes from low energy or power source, that multiple flashes of light may have cumulative flash light annealing effects, comparing or similarily to a single flash of light. As illustrated in FIG. 6, mean IG / ID value before performance of light annealing shows values of 20.7 and 26.5 with standard deviations of 0.5 and 0.8 for Samples A2 and B2, respectively. After performance of flash light annealing on Sample A2 with the single flash of light, the mean IG / ID value reflected 68.0 with a standard deviation of 4.23, showing an increase of 47.3 in value or 228.5% in percentage. Further, after performance of flash light annealing on Sample B2 with the fifteen flashes of light, the mean IG / ID value reflected 69.5 with a standard deviation of 5.8, showing an increase of 43.0 in value or 162.3% in percentage.

[0109] FIG. 7 demonstrates another embodiment of the present disclosure, applying laser annealing of CNT pellicle films to enhance IG / ID and EUV transmission. A pristine CNT pellicle film (i.e., untreated) with an 80.84% at 550 nm wavelength transmission rate experienced negligible or insignificant transmission rate change measured by 550 nm wavelength (i.e., 80.48%) after receiving a 30-watt laser energy for a duration of 10 milliseconds for each irradiated surface area under vacuum. On the other hand, the EUV transmission rate of this in-vacuum laser annealed pristine CNT pellicle film was increased from 94.73% to 96.26%, representing a significant gain. The IG / ID was raised from a mean value of 31.97 to 39.53, providing a gain of 7.56 in value or 23% in percentage.

[0110] The illustrations of the embodiments described herein are intended to provide a general understanding of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of products and methods that form the products or methods described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the 1disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. Additionally, the illustrations are merely representational and may not be drawn to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be minimized. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive.

[0111] One or more embodiments of the disclosure may be referred to herein, individually and / or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any particular invention or inventive concept. Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments and other embodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the description.

[0112] The Abstract of the Disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter.

[0113] The above disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and otherembodiments which fall within the true spirit and scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

Claims

What is claimed is:

1. A nanostructure film comprising: a plurality of carbon nanofibers that are intersected randomly to have an interconnected network structure, the interconnected network structure having a planar orientation, being an electromagnetic wave energy irradiated structure, and having a post-irradiation extreme ultraviolet (EUV) transmission rate of 80% and above.2 The nanostructure film of Claim 1, wherein the interconnected network structure has a gain of a ratio of G-band intensity to D-band intensity in a Raman spectrum (IG / ID).3 The nanostructure film of Claim 2, wherein the gain is 5% and higher than an IG / ID of a non-irradiated interconnected network structure having the plurality of carbon nanofibers randomly intersected.4 The nanostructure film of Claim 1, wherein the post-irradiation EUV transmission rate is 92 and above.5 The nanostructure film of Claim 1, wherein the post -irradiation EUV transmission rate is 95 and above.6 The nanostructure film of Claim 1, wherein the post -irradiation EUV transmission rate is at least 0.3% higher than a pre-irradiation EUV transmission rate of the interconnected network structure.

7. The nanostructure film of Claim 1, wherein the post -irradiation EUV transmission rate is at least 1.0% higher than a pre-irradiation EUV transmission of the interconnected network structure.

8. The nanostructure film of Claim 1, wherein a pre-irradiation IG / ID is 14 and above.9 The nanostructure film of Claim 1, wherein the electromagnetic wave for irradiating a surface of the interconnected network structure is selected from at least one wavelength ranging from a lower limit of 100 nm to an upper limit of 1.0 mm.10 The nanostructure film of Claim 1, wherein an energy for irradiating a surface of the interconnected network structure arriving at the surface is selected from a range having a lower limit of 0.5 J / cm2and an upper limit of 50 J / cm2.11 The nanostructure film of Claim 1, wherein a power for irradiating a surface of the interconnected network structure arriving at the surface is selected from a range having a lower limit of 0.05 watts and an upper limit of 1000 watts.12 The nanostructure film of Claim 1, wherein the plurality of the carbon nanofibers comprises single-walled carbon nanotubes, multiwalled carbon nanotubes, and double-walled carbon nanotubes, wherein a number of walls of the single-walled carbon nanotubes is one, a number of walls of the double-walled carbon nanotubes is two, and a number of walls of the multiwalled carbon nanotubes is three or more.

13. The nanostructure film of Claim 12, wherein a number of the double-walled carbon nanotubes accounts for at least 50% of the plurality of the carbon nanofibers.

14. The nanostructure film of Claim 1, wherein a duration for irradiating the interconnected network structure is selected from a range having a lower limit of 0.1 milliseconds and an upper limit of 1.0 seconds.

15. A method of improving an extreme ultraviolet (EUV) pellicle film, the method comprising: providing a plurality of carbon nanofibers; intersecting the plurality of carbon nanofibers to form an interconnected network structure; and irradiating at least a surface of the interconnected network structure with an irradiation energy to increase a ratio of G-band intensity to D-band intensity (IG / ID).

16. The method of Claim 15, wherein the EUV pellicle film has a minimum post -irradiation EUV transmission rate of 80%, the minimum post -irradiation EUV transmission rate being at least 0 3 higher than a pre-irradiation EUV transmission rate of the EUV pellicle film.17 The method of Claim 15, wherein the EUV pellicle film has a post -irradiation IG / ID at least 5 higher than the pre-irradiation IG / ID.18 The method of Claim 15, wherein a cumulative duration of irradiating the interconnected network is selected from a range having a lower limit of 0.1 milliseconds to an upper limit of 10 seconds.

19. The method of Claim 15, wherein an energy for irradiating a surface of the interconnected network at the surface is selected in a range having a lower limit of 0.5 J / cm2and a higher limit of 50 J / cm2.

20. The method of Claim 15, wherein a power for irradiating at the surface of the interconnected network structure is selected from a range having a lower limit of 0.05 W / cm2and an upper limit of 1,000 W / cm2.

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