Enhanced ultra-thin, ultra-low density films for EUV lithography and method of producing thereof

Abstract

A filtration-formed nanostructured surface film is disclosed. This filtration-formed nanostructured surface film comprises a plurality of carbon nanofibers randomly intersecting to form a planar-oriented interconnected network structure, which is enhanced by plasma treatment. This interconnected structure allows for a high minimum EUV transmittance of at least 92% with a thickness ranging from a lower limit of at least 3 nm to a maximum upper limit of 100 nm, enabling efficient EUV lithography.

Description

Enhanced ultra-thin and ultra-low density films for EUV lithography and methods for their manufacture The present disclosure relates generally to thin films and thin film devices used in semiconductor microchip fabrication, and more particularly to an ultrathin, ultralow density, nanostructured, self-standing pellicle film with enhanced mechanical properties for extreme ultraviolet (EUV) lithography and a method for making such a pellicle and pellicle film. This application claims priority to U.S. Provisional Patent Application No. 63 / 249,113, filed on September 28, 2021. The disclosures of each of these documents, including specifications, drawings, and claims, are incorporated herein by reference in their entireties. The surface layer acts as a protective device. It covers a photomask and is used in semiconductor microchip manufacturing. A photomask can be an opaque plate with holes that allow light to pass through in a defined pattern, or a transparent piece. Such photomasks are commonly used in photolithography and integrated circuit production. As a master template, a photomask is used to create a pattern on a substrate (typically a thin silicon wafer in the case of semiconductor chip manufacturing). Particle contamination can be a significant problem in semiconductor manufacturing. The photomask is protected from particles by a skin layer; this is a thin, transparent film stretched over a frame attached to the patterned side of the photomask. The skin layer is close to the photomask, but far enough away that medium- to small-sized particles that land on the skin layer will be too far out of focus to be printed. Recently, the microchip manufacturing industry has realized that the skin layer can also protect the photomask from damage due to causes other than particles and contaminants. Extreme ultraviolet lithography (EUV) is an advanced optical lithography technique that uses the EUV wavelength range, more specifically a 13.5 nm wavelength. It enables semiconductor microchip manufacturers to pattern the most complex features at 7 nm resolution and beyond, allowing them to place more transistors without increasing the size of the required space. The EUV light mask works by reflecting light, which is achieved using alternating layers of molybdenum and silicon. When the EUV light source is turned on, the EUV light first strikes the surface film, passes through it, and then bounces off from under the light mask, striking the surface film again before continuing its path to print the microchip. Some energy is absorbed during this process, and as a result, heat can be generated, absorbed, and accumulated. The temperature of the surface layer can rise to anywhere from 600 to 1000 degrees Celsius, or even higher. While heat resistance is important, the surface layer must also be highly transparent to EUV light to ensure transmission of reflected light and the light pattern from the photomask. After decades of research and effort, a polysilicon-based EUV overlay was developed in 2016, achieving only 78% EUV transmittance at a simulated, relatively low-power 175-watt EUV source. Stringent requirements, driven by the need for greater transistor density, present further technical challenges for EUV overlay developers, aiming for higher transmittance, lower transmittance variation, higher temperature tolerance, and stronger mechanical robustness. Attempts have been made to achieve higher EUV transmittance (e.g., 90%, 95%, or even 98%) by incorporating carbon nanotubes (CNTs) into the formation of surface films. However, in order to manufacture and utilize thin films with higher EUV transmittance in EUV lithography scanner chambers, the film's mechanical strength needs to be further enhanced. This is because any pressure disturbances or mechanical vibrations during product packaging, shipping, and scanner pump-down and venting can cause irreparable film damage. Consequently, existing technologies have been unable to produce and provide surface films with both high EUV transmittance and sufficient mechanical strength for use in EUV lithography scanners. Furthermore, the demand for significantly larger film sizes for EUV scanners (e.g., full-size surface films of 110 mm x 140 mm or higher on larger bezels) presents additional challenges regarding mechanical strength requirements while maintaining ultra-thin and high EUV transmission states. Therefore, in conventional technology, the development of EUV surface layers is significantly limited by three factors (which are often contradictory) that are characteristic of high transmittance of EUV light, ultra-thin thickness of the surface layer, and strong mechanical strength in one embodiment. In the production of such thin films, existing methods for increasing the film strength are ineffective. According to one aspect of the present disclosure, a specially structured nanotube film is disclosed. The nanotube film includes a plurality of carbon nanotubes randomly intersecting to form an interconnected network structure with a planar orientation. The interconnected network structure has a thickness ranging from a lower limit of at least 3 nm to an upper limit of at most 100 nm and a minimum EUV transmittance of 92% or higher. According to another aspect of the present disclosure, in some embodiments, the thickness ranges from a lower limit of 3 nm to an upper limit of 40 nm. According to another aspect of the present disclosure, in some embodiments, the thickness ranges from a lower limit of 3 nm to an upper limit of 20 nm. According to yet another aspect of the present disclosure, in some embodiments, the average thickness of the interconnect network structure is between 10.7 nm and 11.9 nm. According to yet another aspect of the present disclosure, in some embodiments, EUV transmittance is increased to greater than 95%. According to yet another aspect of the present disclosure, in some embodiments, EUV transmittance is increased to above 98%. According to another aspect of the present disclosure, the plurality of carbon nanotubes further include single-walled carbon nanotubes and multi-walled carbon nanotubes. The single-walled carbon nanotube has one wall, the double-walled carbon nanotube has two walls, and the multi-walled carbon nanotube has three or more walls. According to another aspect of the present disclosure, single-walled carbon nanotubes account for 20% to 40% of all carbon nanotubes, double-walled carbon nanotubes account for 50% or more of all carbon nanotubes, and the remainder of the carbon nanotubes are multi-walled carbon nanotubes. According to yet another aspect of the present disclosure, the nanotube film is further treated by plasma treatment. According to yet another aspect of the present disclosure, the plasma treatment of the nanostructured film uses a gas selected from hydrogen or oxygen. According to another aspect of the present disclosure, the surface layer undergoes a plasma treatment. According to another aspect of the present disclosure, the plasma treatment of the surface layer applies a reactive gas selected from oxygen, hydrogen, or atmospheric air. According to another aspect of the present disclosure, the plasma treatment is mild as defined by treatment time interval, treatment power, and gas type. According to another aspect of the present disclosure, the treatment time interval is between 1 and 60 seconds, and preferably between 5 and 20 seconds. According to one aspect of the present disclosure, the plasma treatment is applied at a power between 15 watts and 35 watts. According to yet another aspect of the present disclosure, the plasma processing power is between 15 watts and 20 watts. According to one aspect of the present disclosure, plasma treatment of a small surface film of size 10 mm×10 mm can be performed at a power range of 15 watts to 35 watts with a treatment time interval of no more than 50 seconds. According to another aspect of the present disclosure, the plasma treatment of a small-sized 10 mm×10 mm surface film may preferably be performed at a power range of 15 watts to 20 watts and a treatment time interval of 5 to 20 seconds. According to one aspect of the present disclosure, for full-size or larger surface films, the plasma treatment applies 15 to 25 watts of power. According to another aspect of the present disclosure, the plasma treatment applies 22 watts or less of power for full-size or larger surface films. According to another aspect of the present disclosure, for full-size or larger ultra-thin surface films with greater than 89% light transmittance at 550 nm, the plasma treatment applies a power of 10 to 20 watts. According to another aspect of the present disclosure, for full-size or larger ultra-thin surface films with greater than 89% light transmittance at 550 nm, the plasma treatment applies 15 or 16 watts of power. According to one aspect of the present disclosure, the plasma treatment time interval is 25 seconds or less for a full-size surface film. According to another aspect of the present disclosure, the plasma treatment time interval is 22 seconds or less for a full-size surface film. According to yet another aspect of the present disclosure, for a full-size or larger ultra-thin surface film having a light transmittance greater than 89% at 550 nm, the plasma treatment time interval is 6 to 15 seconds. According to yet another aspect of the present disclosure, for a full-size or larger ultra-thin surface film having a light transmittance greater than 89% at 550 nm, the plasma treatment time interval is 6 to 15 seconds. According to yet another aspect of the present disclosure, for a full-size or larger ultra-thin surface film having a light transmittance greater than 89% at 550 nm, the plasma treatment time interval is 6 seconds or 10 seconds. Through one or more of the various aspects of the present disclosure, embodiments and / or specific features, sub-components or processes of the present disclosure are intended to bring about one or more of the advantages as specifically described above and pointed out below. The skin layer may refer to a thin transparent film that protects the photomask during semiconductor microwaving. The skin layer contemplates a protective device having a border frame and a central aperture. Both the border and the aperture are covered by a continuous film on top of at least a portion of the border and the entire aperture. Such a film is self-supporting in the center portion over the aperture. The skin layer may act as a dust cover to prevent particles and contaminants from falling onto the photomask during manufacturing. However, the skin layer must be transparent enough to allow transmission of EUV light for performing lithography. A higher level of light transmission is desirable for more efficient lithography. Furthermore, surfaces for EUV lithography require large (e.g., greater than 110 x 140 mm) self-supporting thin film materials with extreme and unique properties. A full-size EUV surface can refer to a surface device with a self-supporting film covering an aperture of 110 x 140 mm or larger. In addition to high transparency to EUV radiation, the surface layer must withstand temperatures exceeding 600°C and be mechanically robust to survive the handling, transportation, pumping, and exhaust operations during photolithography processes. Gas permeability while retaining micron-sized particles is also desirable. Given the number of high-level properties required, effective EUV surface layers have traditionally been difficult to manufacture. In this regard, carbon nanotubes have been suggested as a possible starting material for creating skin layers for such EUV skin layer applications due to their excellent thermal and mechanical properties and ability to form porous films. Carbon nanotubes and carbon nanotube films Carbon nanotubes (CNTs) generally come in several different types, including but not limited to single-walled CNTs (SWCNTs), double-walled CNTs (DWCNTs), multi-walled CNTs (MWCNTs), and coaxial nanotubes. They can exist essentially pure as one type, or often in combination with other types. Individual CNTs can intersect with a small number of other CNTs. Many CNTs together can form a network of self-supporting microstructured films. As the names suggest, SWCNTs have one or a single wall, DWCNTs have two walls, and MWCNTs have three or more walls. Among several potential approaches for producing self-supporting membranes is the use of filtration-based methods to fabricate membranes, ranging from small-scale membranes to large, uniform membranes suitable for EUV lithography or even larger than full-scale surfaces. This filtration-based approach allows for the rapid production of membranes not only of CNTs but also of other high-aspect-ratio nanoparticles and nanofibers, such as boron nitride nanotubes (BNNTs) or silver nanowires (AgNWs). Because this approach separates the nanoparticle synthesis process from the membrane fabrication process, a wide variety of nanotube types produced by virtually any method can be used. Different nanotube types can be mixed in any desired ratio, such as a mixture of two or more CNTs selected from SWCNTs, DWCNTs, and MWCNTs. Because filtration is a self-leveling process (a highly desirable membrane formation process in that nonuniformities in membrane thickness are self-corrected by changes in local permeability during the filtration process), filtration is also a potential candidate for producing highly uniform membranes. After film formation, plasma treatment is applied to the surface film on the surface frame or carrier frame, using selected gas and plasma treatment time intervals to enhance the mechanical properties of the film, reduce film deflection, and increase the film rupture pressure and flow rate when the film ruptures. Plasma treatment is widely used to clean, activate, etch, and coat surfaces in a variety of technical fields for various purposes. These purposes include promoting surface adhesion, wettability, and hydrophilicity. For stacks of 100-layer CNT sheets densified with polyvinyl alcohol extracted from a CNT forest, lower power plasma treatments (as low as 100 watts for 10 seconds) have been shown to improve the Young's modulus and tensile strength of the sheets tested using a Surfx Atomflo™ 400 plasma system, while higher power treatments (such as 140 watts for 30 seconds) actually reduced the Young's modulus and tensile strength of the sheets. FIG1 illustrates a flow chart for producing a plasma-treated nanotube surface film according to an exemplary embodiment. As illustrated in FIG1 , a self-supporting carbon nanotube-based surface membrane can be produced via a filtration-based method. In operation 101, a catalyst is removed from carbon nanotubes (CNTs) to be used to form a water-based suspension. In one example, the CNTs can be chemically purified to reduce the concentration of catalyst particles to less than 1% by weight, or preferably less than 0.5% by weight, as measured by thermogravimetric analysis, before being dispersed into the suspension. The removal of the catalyst is not limited to any particular procedure or process, and any suitable procedure can be used to achieve the desired result. In operation 102, a water-based suspension is prepared using purified CNTs, such that the purified CNTs are uniformly dispersed in the water. When preparing one or more CNT suspensions, the carbon nanotube material can be mixed with a selected solvent to uniformly distribute the nanotubes in the final solution as a suspension. Mixing can include mechanical mixing (e.g., using a magnetic stir bar and stir plate), ultrasonic agitation (e.g., using an immersed 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, such as 60%, 70%, 80%, 90%, 95% IPA, N-methyl-2-pyrrolidone (NMP), dimethyl sulfide (DMS), and combinations thereof. In one example, a surfactant can also be included to facilitate uniform dispersion of the carbon nanofibers in the solvent. Examples of surfactants include, but are not limited to, anionic surfactants. Carbon nanofiber membranes are generally formed from one of MWCNTs, DWCNTs, or SWCNTs. Carbon nanofiber membranes may also include a mixture of two or more types of CNTs (i.e., SWCNTs, DWCNTs, and / or MWCNTs) with varying ratios between the different types of CNTs. Each of these three different types of carbon nanotubes (MWCNTs, DWCNTs, and SWCNTs) exhibits distinct properties. In one example, single-walled carbon nanotubes (SWCNTs) can be more easily dispersed in water or water and solvent (i.e., the majority of nanotubes are individually suspended without adsorbing to other nanotubes) for subsequent formation into randomly oriented carbon nanotube sheets. This ability to uniformly disperse individual nanotubes in water or water and solvent allows for the production of more uniform nanotube films across a surface, formed by removing water and solvent from a nanofiber suspension. This physical uniformity can also improve the uniformity of properties across the film (e.g., even radiation transmission through the film). As used herein, the term "nanofiber" means a fiber having a diameter of less than 1 μm. As used herein, the terms "nanofiber" and "nanotube" are used interchangeably and encompass both single-walled carbon nanotubes, double-walled carbon nanotubes, and / or multi-walled carbon nanotubes in which carbon atoms are linked together to form a cylindrical structure. In one example, the water-based CNT suspension initially formed in operation 102 can have a purity of at least 85% SWCNTs. The remainder can be a mixture of DWCNTs, MWCNTs, and / or a catalyst. In other examples, CNT suspensions can be prepared having various ratios of dispersed CNT types, such as approximately 20% / 75% DWCNT / SWCNT, approximately 50% / 45% DWCNT / SWCNT, or approximately 70% / 20% DWCNT / SWCNT, with the balance being MWCNTs. In one example, an anionic surfactant can be used as a catalyst in the suspension. In operation 103, the CNT suspension is then further purified to remove aggregated or agglutinated CNTs from the initial mixture. In one example, different forms of CNTs (undispersed or aggregated CNTs versus fully dispersed CNTs) can be separated from the suspension via centrifugation. Centrifuging the surfactant-suspended CNTs can help reduce the turbidity of the suspension and ensure that the CNTs are fully dispersed in the final suspension before entering the next filtration step. However, aspects of the present disclosure are not limited thereto, and other separation methods or procedures may be utilized. In operation 104, the CNT supernatant from operation 103 is then filtered through a filter membrane to form a CNT mesh, ie, a continuous sheet of interdigitated CNTs. In one example, a technique for making CNT membranes uses water or other fluids to deposit nanotubes in a random pattern onto a filter. A uniformly dispersed CNT-containing mixture is allowed to pass through or forced through the filter, leaving nanotubes on the filter surface to form a nanotube structure or membrane. The size and shape of the resulting membrane are determined by the size and shape of the desired filter area, while the thickness and density of the membrane are determined by the amount of nanotube material utilized during the process and the permeability of the filter membrane to the input CNT material component, since impermeable components are trapped on the filter surface. If the concentration of nanotubes dispersed in the fluid is known, the mass of nanotubes deposited on the filter can be determined from the amount of fluid passing through the filter. The average areal density of the membrane can be determined by dividing the nanotube mass by the total filter area. The selected filter is generally impermeable to all CNTs. The CNT membrane formed by filtration can be a combination of SWCNTs, DWCNTs and / or MWCNTs of different compositions. The CNT film is then detached from the filter membrane in operation 105. More specifically, the carbon nanofibers may become randomly intertwined to form a planar oriented interconnected network structure, thereby forming a thin CNT film. In operation 106, the lifted CNT film is then harvested using a harvester frame and then directly transferred and mounted onto nearly any solid substrate, such as a surface frame with a defined orifice. The CNT film can be mounted to the surface frame and cover the orifice to form a surface. Transferred films mounted on metal or silicon frames with openings as small as 1×1 cm can be useful. Actual EUV scanners highly require films of much larger sizes. According to an exemplary embodiment, a scanning electron microscope (SEM) image of a CNT film prepared according to FIG. 1 is illustrated in FIG. Based on current industry standards, a full-size surface for EUV lithography scanning may require an ultra-thin, self-supporting film typically having dimensions of 110×140 mm or larger. In operation 107, the CNT film is further treated by plasma. Plasma treatment uses a selected reactive gas or gas precursor with a predetermined treatment power and treatment time interval. A variety of gases can be considered and applied to generate the plasma. The plasma treatment power and treatment time interval vary depending on the specific application. After completing operation 107, the method for producing a plasma-treated nanotube surface film is completed in operation 108. Characterization of the CNT films, such as mechanical strength, flexure testing, permeability testing, flexure under constant pressure or during pumping conditions, can be performed with or without plasma treatment. Exemplary embodiments of the present disclosure provide filtered CNT surface films having different configurations than known prior art to exhibit certain properties that meet or exceed EUV lithography requirements, including but not limited to EUV transmittance (EUVT), EUVT uniformity, low deflection, and mechanical strength under pressure changes. This exemplary configuration of the skin film provides an ultra-thin skin film that allows for very high EUVT (e.g., greater than 92%, 95%, or even 98%) while being extremely high temperature resistant (e.g., resistant to temperatures greater than 600° C.) and mechanically robust. In one example, the minimum EUVT can be 92% or greater. Although the above disclosure is provided with respect to CNTs and aqueous solutions, aspects of the present disclosure are not limited thereto, such that different nanotubes, such as boron nitride nanotubes (BNNTs), can be utilized using the same principle. The above mentioned thin films can also be conformally coated by various methods including but not limited to electron beam, chemical vapor deposition, atomic layer deposition, spin coating, dip coating, spray coating, sputtering, DC sputtering and RF sputtering. The material can be a metal element, including any of the following: silicon, SiO 2. SiON, boron, ruthenium, boron, zirconium, niobium, molybdenum, rubidium, yttrium, YN, Y 2O 3. Strontium and / or rhodium. The material may also be any one of a metal, a metal oxide, or a nitride. However, the present disclosure is not limited thereto, and a combination of materials may be used in the coating. Plasma treatment Plasma treatment is a well-known technique used in various fields of science and technology, as well as in manufacturing processes. It is generally used to clean, activate, modify hydrophilicity, etch, or prepare surfaces for subsequent bonding with other materials using various combinations of reactive gases, gas precursors, gas mixtures, treatment energies, and treatment time intervals. Plasma treatment using one or more inappropriate parameters, whether under optimal or suboptimal conditions, can produce unsatisfactory results on the target surface or cause irreversible damage to the target or target surface, including destruction of the target or target surface. Effective treatment of any surface can also be specified or tailored. In an exemplary embodiment of the present disclosure, the surface layer is placed in a 25 cm x 25 cm enclosure or chamber. Due to the high pressure and gas flow sensitivity of the ultrathin nanotube film, the chamber is then closed and purged with oxygen, hydrogen, nitrogen, or atmospheric air at a low rate of 25 sccm (cubic centimeters per second). In one example, the plasma treatment can be performed in a low pressure environment, such as 0.2 to 0.3 Pascals, and the treatment temperature can be room temperature or ambient temperature. Furthermore, a radio frequency power ranging from 1 to 100 watts is applied for 1-600 seconds. The chamber can then be slowly vented, from 5 minutes to overnight, and the sample removed. Multiple samples were prepared for each experimental group, and multiple measurements were performed on the same sample. Film thickness The exemplary embodiments of the present disclosure were further analyzed with respect to their thickness, which is critical for determining and ensuring high EUVT. More specifically, the Dimension Icon AFM instrument was first calibrated based on National Institute of Standards and Technology (NIST) traceable standards. An area of ​​approximately 90 µm x 90 µm of the CNT surface film was selected for AFM 2D and 3D height imaging. Step height analysis was performed to measure the film thickness. Three measurements were taken from three carbon nanotube film samples, with readings of 11.8 nm, 10.6 nm, and 11.4 nm, respectively. The average thickness of the test subjects was approximately 11.3 ± 0.6 nm (10.7 nm to 11.9 nm). Furthermore, based on additional measurement sets, thickness values ​​in the ranges of 3 nm to 100 nm, 3 nm to 40 nm, and 3 nm to 20 nm are provided. In other samples, the thickness may also be in the range of 3 nm to 100 nm, 3 nm to 40 nm, and 3 nm to 20 nm. However, aspects of the present application are not limited thereto, and the range may have a lower limit of 3 nm to 5 nm and an upper limit of 20 nm to 100 nm. Considering that DWCNT-dominant CNT skin films exhibit much higher mechanical strength, DWCNT-dominant CNT skin films can be constructed to be extremely thin to allow higher EUVT values ​​for EUV scanners without sacrificing mechanical strength or integrity. Visible light and EUV Transmittance Measure the EUV transmittance of the sample at the current industry standard of 13.5 nm. Create an EUVT map based on the EUV scan results to show and measure the variation and / or uniformity of the transmittance. The filtered CNT surface films exhibited high EUV transmittance, typically exceeding 92%, with results exceeding 95% or even 98% in some cases. For example, a full-size surface film (approximately 110 mm × 144 mm) scanned across the entire sample exhibited an average transmittance of 96.69 ± 0.15%, while a scan of a 1.5 mm × 1.5 mm central area yielded an average transmittance of 96.75 ± 0.03%. The transmittance of plasma-treated surface films (film size: 10 mm x 10 mm) at 550 nm was measured and compared to an untreated negative control. Transmittance improved for both oxygen- and hydrogen-treated films. The percentage improvement ranged from approximately 0.8% to approximately 3%, as shown in Figures 3 and 4. This improvement correlated well with treatment times ranging from 5 to 60 seconds (see, for example, Figures 3 and 4). The visible and EUV transmittance of plasma-treated films of 110 cm x 140 mm or larger can be measured using the same method. Full-size films treated with 15-watt oxygen plasma exhibited visible light transmittance improvements of 1.4% and 1.7% at treatment intervals of 6 and 8 seconds, respectively. Used for EUV Micro-Shadow CNT Mechanical properties of the surface The exemplary embodiments of the present application provide CNT skins with sufficient and satisfactory mechanical strength for product transportation and handling. The skins can withstand any desired pressure changes in their surroundings, including but not limited to EUV lithography scanner environments. A commonly applied mechanical property is the bulge test, which measures membrane deflection under flow pressure. For example, the membrane to be tested can be attached to the flat surface of a frame (a surface membrane mounted on a surface frame), and a baseline of the membrane can be established without any air or gas flow affecting the membrane. An initial flow of gas (preferably an inert gas) can then be applied vertically at a low, steady pressure, aimed at the central area of ​​the membrane to locally elevate the surface. The gas pressure is gradually increased to further deform the membrane until a predetermined pressure is reached, which for the 2 Pa deflection test is 2 Pascals. This value can also be achieved at a flow rate of approximately 10 sccm, 3.5 mbar / s, or any other conditions where the scanner is pumped or exhausted. The distance between the highest point of the deformed membrane and its baseline is measured. The result can be recorded as deflection at 2 Pa. The deflection test can be performed at pressures other than 2 Pa. Increasing the applied gas flow pressure can ultimately cause the membrane to rupture. This pressure can be recorded as the rupture pressure, and the membrane deflection just before rupture can be referred to as the rupture deflection. The gas flow rate at the point of membrane rupture can be taken as the rupture flow rate. Furthermore, membrane deflection can be purposefully adjusted by methods including, but not limited to, tension adjustment via physical or chemical means. Plasma surface treatment and enhanced mechanical properties One or more exemplary embodiments of the present disclosure are described in detail below and illustrated in Figures 5-10. Figures 5 through 10 exemplify the changes in mechanical properties of a 10 mm x 10 mm nanotube film after oxygen or hydrogen plasma treatment (using various treatment times ranging from 5 seconds to 60 seconds and 20 watts of radio frequency (RF) power) according to exemplary embodiments. According to exemplary aspects, the 10 mm x 10 mm film exhibited reduced deflection when challenged with a constant 2 Pa flow with short treatment intervals. The 10 mm x 10 mm film ruptured at higher flow pressures and higher flow rates. Furthermore, both oxygen and hydrogen treatment of the 10 mm x 10 mm film reduced film deflection by an average of more than 100% for the 10-second treatment, as shown in Figures 5 and 6 , and increased the rupture pressure and rupture flow rate by an average of more than 60% for the 5-second treatment, as shown in Figures 7 through 10 . As exemplified, the benefits of plasma treatment with respect to rupture pressure diminished after treatment intervals exceeding 30 seconds. The studies with smaller and larger RF powers are summarized in Table 1 below. A set of 10 mm x 10 mm nanotube films were subjected to a constant oxygen plasma treatment time of 8 seconds at various RF power levels. Compared to previous studies of film density or percent transmittance at 550 nm, the 20-watt treatment results showed similar reductions in film deflection and gains in rupture pressure and optical transmittance measured at 550 nm. Higher power treatments, such as the 25-watt and higher exemplified in Table 1, showed reduced film deflection while also becoming more fragile due to a dramatic reversal in film rupture pressure. When treated with RF powers of 40 watts or higher, the films became too fragile to survive the plasma treatment. For the full-scale ultra-thin surface layer, a series of plasma treatments using different reactive gases, different plasma powers, and various treatment time intervals are detailed below and in Table 2. Guided by the results of the 10 mm × 10 mm film studies, the full-scale ultrathin surface films took two different paths regarding oxygen plasma treatment. As shown in Table 2, even with reduced plasma treatment powers and treatment intervals, they did not survive well. They were easily broken after 6 seconds of treatment at 18 or 20 watts of applied power. A 10-second oxygen plasma treatment at 15 watts before the treatment process was complete did not protect the ultrathin films from breakage. However, 6- and 8-second oxygen plasma treatments at 15 watts maintained film integrity, demonstrating increases in transmittance at 550 nm of approximately 1.4% and 1.7%, respectively, while also reducing film deflection by approximately 20% and 23%, respectively. The same treatment schedule of 15 watts and 6 seconds with atmospheric air instead of oxygen had approximately the same results as shown in Table 2. A very mild hydrogen plasma treatment as exemplarily outlined in column 8 of Table 2 provided above did not meaningfully improve film deflection, with a 3.3% deflection reduction. When full-scale ultrathin surface films were subjected to the same plasma treatment chamber using nitrogen as the reactive gas, the optical transmittance at 550 nm increased compared to the untreated films, moving in the opposite direction to reduce EUVT. The examples of the embodiments described herein are intended to provide a general understanding of the various embodiments. These examples are not intended to be used as a complete description of all elements and features of the product or method forming the product or method described herein. After reviewing this disclosure, many other embodiments may be clear to those with ordinary knowledge in the technical field to which the invention belongs. Other embodiments can be derived from this disclosure so that structural and logical replacements and changes can be made without departing from the scope of this disclosure. In addition, these examples are merely representative and may not be drawn to scale. Certain proportions within these examples may be exaggerated, while other proportions may be minimized. Accordingly, this disclosure and the accompanying drawings should be regarded as illustrative rather than restrictive. One or more embodiments of the present disclosure may be referred to herein individually and / or collectively by the term "invention," which is merely for convenience and is not intended to automatically limit the scope of this application to any particular invention or inventive concept. Furthermore, although specific embodiments have been illustrated and described herein, it should be understood that any subsequent configuration designed to achieve the same or similar purpose may be substituted in the illustrated embodiments. The present disclosure is intended to cover any and all subsequent adaptations or variations of the various embodiments. Upon review of the description, the combination of the above embodiments and other embodiments not specifically described herein will be clear to those having ordinary knowledge in the technical field to which the invention belongs. The Abstract of this disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the scope of the claims. In addition, in the aforementioned detailed description, various features may be grouped together or described in a single embodiment for the purpose of streamlining this disclosure. This disclosure should not be interpreted as reflecting an intention that the claimed embodiments require more features than those explicitly recited in the various claims. Rather, as reflected in the following claims, the subject matter of the invention may be directed to fewer features than all the features of any disclosed embodiment. Therefore, the following claims are incorporated into the detailed description, with each claim independently defining the subject matter of the individual claims. 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 other embodiments that fall within the true spirit and scope of the 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. 101: Operation 102: Operation 103: Operation 104: Operation 105: Operation 106: Operation 107: Operation 108: Operation The present disclosure is further described in the following detailed description, by way of non-limiting examples of preferred embodiments of the disclosure, with reference to the accompanying drawings in which like characters represent like elements throughout the several views of the drawings. [ FIG. 1 ] A flow chart illustrating the process of fabricating a plasma-treated nanotube surface film according to an exemplary embodiment. [ FIG. 2 ] A scanning electron microscope (SEM) image illustrating the microstructure of an untreated CNT film according to an exemplary embodiment. FIG. 3 illustrates a time course study of the average optical transmittance measured at a wavelength of 550 nm and the average percent change in optical transmittance for a 10 mm×10 mm film treated with oxygen plasma according to an exemplary embodiment. FIG. 4 illustrates a time course study of the average optical transmittance and the average percent change in optical transmittance measured at a wavelength of 550 nm for a 10 mm×10 mm film treated with hydrogen plasma according to an exemplary embodiment. [ FIG. 5 ] illustrates the results of a time course study of the deflection of a 10 mm×10 mm film treated with oxygen plasma according to an exemplary embodiment, measured at a constant pressure of 2 Pascals during plasma treatment. [ FIG. 6 ] illustrates the results of a time course study of the membrane deflection measured at a constant pressure of 2 Pascals during plasma treatment of a 10 mm×10 mm membrane treated with hydrogen plasma according to an exemplary embodiment. FIG. 7 illustrates the results of a time course study of the film rupture pressure measured during plasma treatment of an oxygen plasma treated film according to an exemplary embodiment. FIG. 8 illustrates the results of a time course study of the film rupture pressure measured during plasma treatment of a sample treated with hydrogen plasma according to an exemplary embodiment. FIG. 9 illustrates a time course study of the membrane rupture flow rate measured during plasma treatment of an oxygen plasma-treated nanotube membrane according to an exemplary embodiment. FIG. 10 illustrates a time course study of the membrane rupture flow rate measured during plasma treatment of a nanotube membrane treated with hydrogen plasma according to an exemplary embodiment.

Claims

1. An extreme ultraviolet (EUV) photolithography nanotube film comprising: a plurality of nanotubes randomly intersecting to form a planar-oriented interconnect network structure, the interconnect network structure a) having a thickness ranging from a lower limit of at least 3 nm to an upper limit of at most 100 nm, and a minimum EUV transmittance of 92%; b) being self-supporting; and c) being plasma-treated using an active gas, a treatment power, a treatment pressure, and a treatment time interval, wherein the active gas is oxygen, hydrogen, or atmosphere, the plasma treatment power does not exceed 35 watts, and the treatment time interval is equal to or less than 30 seconds, and the treatment pressure is selected from a range having a lower limit of 0.2 Pascals and an upper limit of 0.3 Pascals.

2. The EUV photolithography nanotube film as claimed in claim 1, wherein the thickness ranges from a lower limit of 3 nm to an upper limit of 40 nm.

3. The EUV photolithography nanotube film as claimed in claim 1, wherein the thickness ranges from a lower limit of 3 nm to an upper limit of 20 nm.

4. The EUV photolithography nanotube film of claim 1, wherein the average thickness of the interconnect network structure is between 10.7 nm and 11.9 nm.

5. The EUV photolithography nanotube film as requested in item 1, wherein the EUV transmittance is increased to 95% or higher.

6. The EUV photolithography nanotube film of claim 1, wherein the plurality of nanotubes further includes single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes, wherein the single-walled carbon nanotube has one wall, the double-walled carbon nanotube has two walls, and the multi-walled carbon nanotube has three or more walls.

7. The EUV photolithography nanotube film as claimed in Item 6, wherein the single-walled carbon nanotubes account for 20% to 40% of all nanotubes, the double-walled carbon nanotubes account for 50% or more of all nanotubes, and the remaining nanotubes are multi-walled carbon nanotubes.

8. The EUV photolithography nanotube film of claim 1, wherein the film has a self-supporting portion with an area of ​​not less than 10 mm × 10 mm.

9. The EUV photolithography nanofilm of claim 1, wherein the self-supporting portion of the nanofilm has an area of ​​not less than 110 mm × 140 mm, the active gas is oxygen, the plasma processing power is not more than 15 watts, and the processing time interval is equal to or less than 8 seconds.

10. A method for improving an extreme ultraviolet (EUV) photolithography nanotube film, the method comprising: obtaining a film having a plurality of carbon nanotubes mounted on a frame with apertures and covering the entire aperture of the frame, the plurality of carbon nanotubes randomly intersecting to form a planar-oriented interconnect network structure, the interconnect network structure having a thickness ranging from a lower limit of at least 3 nm to an upper limit of at most 100 nm and a minimum EUV transmittance of 88%; and subjecting the film to plasma treatment using an active gas, a treatment power equal to or less than 35 watts, a treatment time interval equal to or less than 30 seconds, and a treatment pressure selected from a range having a lower limit of 0.2 Pascals and an upper limit of 0.3 Pascals.

11. The method of claim 10, wherein the film has a thickness ranging from a lower limit of 3 nm to an upper limit of 40 nm.

12. The method of claim 10, wherein the film has a thickness ranging from a lower limit of 10 nm to an upper limit of 20 nm.

13. The method of claim 10, wherein the average thickness of the film is between 10.7 nm and 11.9 nm.

14. The method of claim 10, wherein the self-supporting portion of the membrane has an area of ​​at least 10 mm × 10 mm.

15. The method of claim 10, wherein the self-supporting portion of the membrane has an area of ​​at least 110 mm × 140 mm.

16. The method of claim 15, wherein the plasma processing power does not exceed 18 watts and the processing time interval is equal to or less than 10 seconds.

17. The method of claim 15, wherein the plasma processing power does not exceed 16 watts and the processing time interval is equal to or less than 10 seconds.

18. The method of claim 15, wherein the active gas is oxygen, the processing power is 15 watts, and the processing time interval is 8 seconds or less.

19. The method of claim 10, wherein the nanotubes further comprise single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, and wherein the number of walls included in each of the single-walled carbon nanotubes is one, the number of walls included in each of the double-walled carbon nanotubes is two, and the number of walls included in each of the multi-walled carbon nanotubes is three or more.

20. The method of claim 19, wherein the single-walled carbon nanotubes constitute a percentage between 20% and 40% of all carbon nanotubes, the double-walled carbon nanotubes constitute a percentage of 50% or higher of all carbon nanotubes, and the remainder of carbon nanotubes are multi-walled carbon nanotubes.

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