EUV photolithography nanotube films and methods for performing EUV photolithography

Abstract

A nanostructured pellicle film is disclosed that is coated with an ultra-thin zirconium and formed by filtration. The nanostructured pellicle film includes a plurality of nanotubes that randomly intersect and form an interconnected network structure with a planar orientation that enhances properties, and a zirconium coating layer. The zirconium coating layer coated interconnected structure enables a high minimum EUV transmittance of at least 88%. The interconnected network structure has a thickness ranging from a lower limit of 3 nm to an upper limit of 100 nm, enabling effective EUV lithography processing.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 249,118, filed September 28, 2021, and U.S. Provisional Patent Application No. 63 / 312,658, filed February 22, 2022. The disclosures of each of these documents, including the specification, drawings, and claims, are hereby incorporated by reference in their entirety.

[0002] The present disclosure relates generally to thin films and thin film devices used in semiconductor microchip manufacturing, and more particularly to ultra-thin, ultra-low density, zirconium coated, nanostructured, free-standing pellicle films and devices for extreme ultraviolet (EUV) photolithography. [Background technology]

[0003] A pellicle is a protective device that covers a photomask and is used in semiconductor microchip manufacturing. A photomask may refer to a grown crystalline plate with holes or transparencies that allow light to shine through in a predetermined pattern. Photomasks such as these may be widely used in photolithography and integrated circuit manufacturing. As a master template, the photomask is used to generate patterns on a substrate (usually a thin slice of silicon known as a wafer in semiconductor chip manufacturing).

[0004] Particle contamination can be a significant problem in semiconductor manufacturing. Photomasks are protected from particles by pellicles, which consist of a thin transparent film stretched over a pellicle frame that is attached over the patterned side of the photomask. The pellicle is close to the mask but far enough away that small to medium sized particles that land on the pellicle are too out of focus to be printed. Recently, the microchip manufacturing industry has realized that pellicles can protect photomasks from damage resulting from sources other than particles and contaminants.

[0005] Extreme ultraviolet photolithography is an advanced optical lithography technique that uses the EUV wavelength range (more specifically, 13.5 nm wavelength). It allows semiconductor microchip manufacturers to pattern the most delicate features at resolutions of 7 nm or less to place more transistors without increasing the size of the space required. EUV photomasks work by reflecting light. The reflection of light is achieved by using multiple alternating layers of molybdenum and silicon. When the EUV light source is turned on, the EUV light first strikes the pellicle film, passes through the pellicle film, and is reflected back from underneath the photomask, striking the pellicle film once more, before continuing its path to print the microchip. During this process, some of the energy is absorbed, which can result in heat being generated, absorbed, and stored. The temperature of the pellicle can rise to 450 to over 1000 degrees Celsius.

[0006] While heat resistance is important, the pellicle must also be highly transparent to EUV light to ensure the reflection and light patterns from the photomask can pass through, with low EUV scattering, resulting in accurate, sharp prints and improved manufacturing yields.

[0007] In 2016, a polysilicon-based EUV pellicle was developed after decades of research and efforts, but the EUV transmittance was only 78% for a simulated relatively low-power 175 watt EUV source. Driven by the desire for increased transistor density, stringent requirements present EUV pellicle developers with additional technical challenges for higher transmittance, lower transmittance variation, higher temperature tolerance, and low light scattering.

[0008] Attempts have been made to target higher light transmittance by placing a high single-walled carbon nanotube content (e.g., as high as 98% by weight) in the carbon nanotube sheet, but the products obtained by such attempts have low quality structures and short lifetimes. Therefore, such carbon nanotube-based thin films need to have a certain level of high temperature resistance for a certain period of time under EUV irradiation and low light scattering. As a result, the EUV transmittance of such carbon nanotube-based thin films has not met industry standards, despite having a satisfactory product lifetime.

[0009] Additionally, heat generated during the photolithography process can increase the temperature of the pellicle film from approximately 450°C to over 1,000°C, shortening the pellicle film's lifespan and eventually causing it to break. Any broken pellicle film or pieces of broken pellicle film can cause damage, contamination, or adhesion to the scanner chamber and the underlying reticle and / or mask. As the pellicle film weakens, the scanner may need to vent the chamber, increasing the risk of breaking the already weakened pellicle film. Thus, in such a situation, the scanner must be shut down and production halted, resulting in extended downtime.

[0010] In addition to the lifetime requirement, the pellicle film must have very little light scattering, as any scattering can reduce image contrast in EUV optics, affecting image reconstruction and EUV photolithography throughput.

[0011] Therefore, in the prior art, achieving high EUV light transmittance, good life span of the pellicle film, and low light scattering presents new challenges in the field. Summary of the Invention

[0012] According to an embodiment of the present disclosure, a specifically structured nanotube film is disclosed, which comprises a plurality of carbon nanotubes that randomly intersect and form an interconnected network structure in a planar orientation with a thin zirconium coating layer, the interconnected network structure having a thickness ranging from a lower limit of 3 nm to an upper limit of 100 nm and a minimum EUV transmittance of 88% or greater.

[0013] According to another aspect of the disclosure, in some embodiments, the thickness has a lower limit of 3 nm to an upper limit of 40 nm.

[0014] According to another aspect of the disclosure, in some embodiments, the thickness has a lower limit of 3 nm to an upper limit of 20 nm.

[0015] According to yet another aspect of the present disclosure, in some embodiments, the average thickness of the interconnected network structure is 11 nm.

[0016] According to further aspects of the present disclosure, in some embodiments, the EUV transmission is increased to greater than 92%.

[0017] According to further aspects of the present disclosure, in some embodiments, EUV transmission is increased to greater than 95%.

[0018] According to yet another aspect of the present disclosure, in some embodiments, the EUV transmission is increased to greater than 98%.

[0019] According to one aspect of the present disclosure, in some embodiments, the light transmittance at 550 nm is increased to about 80% or greater.

[0020] According to another aspect of the present disclosure, in some embodiments, the light transmission at 550 nm is increased to 90% or more.

[0021] According to further aspects of the present disclosure, in some embodiments, the light transmittance at 550 nm is increased to 92.5% or greater.

[0022] According to a further aspect of the present disclosure, the plurality of nanotubes further comprises single-walled carbon nanotubes and multi-walled carbon nanotubes, the single-walled carbon nanotubes having one wall, the double-walled carbon nanotubes having two walls, and the multi-walled carbon nanotubes having three or more walls.

[0023] According to another embodiment of the present disclosure, single-walled carbon nanotubes account for 20-40% of all carbon nanotubes, double-walled carbon nanotubes account for 50% or more of all carbon nanotubes, and the remaining carbon nanotubes are multi-walled carbon nanotubes.

[0024] According to a further aspect of the present disclosure, the nanotube film further comprises a zirconium coating layer.

[0025] According to another aspect of the present disclosure, the zirconium coating layer has an average thickness of 1.5 nm or less on one side of the nanotube film.

[0026] According to another aspect of the present disclosure, the zirconium coating layer has an average thickness of less than or equal to 1 nm on each side of the nanotube film.

[0027] According to another aspect of the present disclosure, the zirconium coating layer has an average thickness of 0.5 nm or less on each side of the nanotube film.

[0028] According to another aspect of the present disclosure, the average thickness of the zirconium coating layer is about 0.3 nm thick on each side of the nanotube film.

[0029] According to one aspect of the present disclosure, a zirconium coating layer covers both sides of the nanotube film.

[0030] According to another aspect of the present disclosure, a zirconium coating layer covers one side of the nanotube film.

[0031] According to another aspect of the present disclosure, the zirconium coated nanotube film has a scattering of 0.5% or less measured at an angle of 4.7° (degrees).

[0032] According to another aspect of the present disclosure, the zirconium coated nanotube film has a scattering of 0.3% or less measured at an angle of 4.7° (degrees).

[0033] According to another aspect of the present disclosure, the zirconium coated nanotube film has a scattering of 0.2% or less measured at a 4.7° (degree) angle.

[0034] The present disclosure will be further described in the following detailed description with reference to a number of drawings, which are mentioned as non-limiting examples of preferred embodiments of the present disclosure, in which like characters represent like elements throughout the several views of the drawings. [Brief description of the drawings]

[0035] [Figure 1] 1 shows a flow chart for manufacturing a zirconium (Zr) coated pellicle film according to an exemplary embodiment. [Diagram 2] 1 illustrates the correlation between average areal density and visible light transmittance according to an example embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Through one or more of its various aspects, the embodiments and / or specific features, subcomponents, or processes of the present disclosure are intended to demonstrate one or more of the advantages specifically discussed above and below.

[0037] All numbers expressing quantities of ingredients, reaction conditions, thicknesses, and so forth used in the specification and claims can be understood to be optionally modified in all instances by the term "about." Accordingly, the numerical parameters set forth in the following specification and attached claims may be approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of significant digits and ordinary rounding approaches.

[0038] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention may be approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.

[0039] A pellicle may refer to a thin transparent film that protects a photomask during semiconductor microchip fabrication. A pellicle constitutes a protective device with a boundary frame and a central aperture. Both the boundary and the aperture are covered by a continuous thin film over at least a portion of the boundary and the entire aperture. The central portion of such thin film over the aperture is free-standing. A pellicle may act as a dust cover to prevent particles and contaminants from falling onto the photomask during fabrication. However, the pellicle must be transparent enough to allow light to pass through for lithography and, more importantly, to allow EUV illumination. A higher level of light transmission is required for more effective EUV photolithography.

[0040] Also, when EUV light travels through a pellicle into a vacuum or EUV scanner chamber filled with hydrogen gas and then back into the vacuum or hydrogen environment, some of the light is absorbed by the pellicle and subsequently emitted in a diverted direction, called scattering. This EUV scattering can cause anomalous light patterns on the mask and ultimately on the silicon wafer, which can result in printing errors, reduced resolution, and / or lower manufacturing yields. The total amount of scattered light that deviates from its original path within an angle of 4.7 degrees is measured, and the result is the key parameter of scattering for the current industry standard.

[0041] Furthermore, pellicles for EUV lithography require a long lifetime to support continuous manufacturing operations and avoid frequent pellicle replacement and manufacturing interruptions due to pump-down and vent cycles of EUV scanners. One proposed solution is to apply a thin metal coating on the pellicle film. When the EUV exposure is off, or during the pause between two EUV exposures, this metal coating releases the heat gained and absorbed during the EUV exposure. This increases the emissivity of the pellicle film, thereby reducing the temperature of the pellicle film and extending its lifetime.

[0042] Any selected coating material must retain high EUV transmission while experiencing very gradual degradation in transmission. Further EUV transmission degradation may not be acceptable due to the high transmission requirements of EUV photolithography. Secondly, the metal coating must not meaningfully alter the scattering pattern in a way that violates the strict scattering criteria. The coating material must be "transferred" onto the surface of the pellicle film during EUV exposure, bonded to that surface, and maintained in a high temperature environment without any delamination effects that could lead to contamination of the reticle, mask, or scanner chamber.

[0043] In this aspect, as one approach to producing, using, and extending the use of pellicle films under EUV irradiation, carbon nanotubes are proposed as a semiconductor substrate material that can be used to fabricate pellicles for this EUV pellicle application, along with metal coatings.

[0044] Carbon nanotubes and carbon nanotube films Carbon nanotubes (CNTs) typically come in several different varieties, including, but not limited to, single-walled CNTs (SWCNTs), double-walled CNTs (DWCNTs), multi-walled CNTs (MWCNTs), and coaxial nanotubes. They may exist substantially purely of one variety, or often in combination with other varieties. Individual CNTs may intersect with several others. Collectively, many CNTs can form mesh-like, free-standing microstructured thin films. As the names suggest, SWCNTs have one or a single wall, DWCNTs have two walls, and MWCNTs have three or more walls.

[0045] Furthermore, among several possible methods to produce freestanding films, a filtration-based approach was used to produce films ranging from small size to films large enough and uniform for EUV lithography. This filtration-based method allows for the rapid production of films of CNTs as well as other high aspect ratio nanoparticles and nanofibers, such as boron nitride nanotubes (BNNTs) or silver nanowires (AgNWs). Because this approach separates the nanoparticle synthesis method from the film production method, different types of nanotubes made by virtually any method may be used. Different types of nanotubes can be mixed in any desired proportion, such as a mixture of two or more layers of CNTS selected from SWCNTs, DWCNTs, and MWCNTs. Filtration is a self-leveling process in the sense that non-uniformities in film thickness during the filtration process are self-corrected by local permeability variations, and is therefore a highly desirable film formation process and a promising candidate for the production of highly uniform films.

[0046] After the successful filtration process, a filter film is formed and collected for Zr coating by electron beam or other physical vapor deposition methods.

[0047] FIG. 1 shows a flow chart for manufacturing a Zr coated pellicle film according to an exemplary embodiment.

[0048] As shown in Figure 1, a free-standing carbon nanotube-based pellicle film may be created by a filtration-based method. In operation 101, a catalyst is removed from carbon nanotubes (CNTs) to be used to form an aqueous suspension. In an example, the CNTs may be chemically purified to reduce the concentration of catalyst particles to less than 1 wt% or preferably less than 0.5 wt% as measured by thermogravimetric analysis prior to dispersion in the suspension. The removal of the catalyst is not limited to any particular process or procedure, and any suitable process may be used to achieve the desired results.

[0049] In operation 102, an aqueous suspension is prepared using the purified CNTs such that the purified CNTs are uniformly dispersed in water. When preparing one or more CNT suspensions, the carbon nanotube material may be mixed with a selected solvent to uniformly disperse the nanotubes in the final solution as a suspension. Mixing may include mechanical mixing (e.g., using a magnetic stir bar and stir plate), ultrasonic mixing (e.g., using an immersion ultrasonic probe), or other methods. In some examples, the solvent may 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 examples, a surfactant may be included to aid in the uniform dispersion of the carbon nanofibers in the solvent. Examples of surfactants include, but are not limited to, anionic surfactants.

[0050] Carbon nanofiber films are typically formed from one of MWCNTs, DWCNTs, or SWCNTs. Carbon nanofiber films may also contain mixtures of two or more types of CNTs (i.e., SWCNTs, DWCNTs, and / or MWCNTs) with varying ratios between the different types of CNTs.

[0051] Each of these three different types of carbon nanotubes (MWCNT, DWCNT, and SWCNT) has different properties. In one example, single-walled carbon nanotubes can be more conveniently dispersed in water or water with a solvent (i.e., the majority of the nanotubes are suspended separately and are not adsorbed onto other nanotubes) for subsequent formation into sheets of randomly oriented carbon nanotubes. This ability to uniformly disperse individual nanotubes in water or water with a solvent can result in the production of more planarly uniform nanotube films formed by removing the water and solvent from the nanofiber suspension. This physical uniformity can also improve the uniformity of properties across the film (e.g., uniform radiation transmission across the film).

[0052] As used herein, the term "nanofiber" refers to a fiber having a diameter of less than 1 μm. As used herein, the terms "nanofiber" and "nanotube" are used interchangeably and both include single-walled carbon nanotubes, double-walled carbon nanotubes, and / or multi-walled carbon nanotubes (where the carbon atoms are linked together to form a cylindrical structure).

[0053] In an example, the aqueous CNT suspension initially formed in operation 102 may have a purity of at least greater than 85% SWCNT. The remainder may be a mixture of DWCNT, MWCNT, and / or catalyst. In other examples, dispersed CNT suspensions may be prepared with different ratios of different types of CNT, such as about 20% / 75% DWCNT / SWCNT, about 50% / 45% DWCNT / SWCNT, about 70% / 20% DWCNT / SWCNT (with the remainder being MWCNT). In an example, an anionic surfactant may be used as a catalyst in the suspension.

[0054] In operation 103, the CNT suspension is then further refined to remove any aggregated or stuck CNTs from the initial mixture. In an example, different morphologies of CNTs (undispersed or aggregated vs. well-dispersed) may be separated from the suspension by centrifugation. Centrifugation of the surfactant-suspended carbon nanotubes before proceeding to the next filtration step may help reduce the turbidity of the suspension solution to ensure full dispersion of the carbon nanotubes within the final suspension solution. However, aspects of the present disclosure are not limited in this respect and other separation methods or processes may be used.

[0055] In operation 104, the CNT supernatant from operation 103 is then filtered through a filtration membrane to form a CNT web (a continuous sheet of film of intersecting CNTs).

[0056] In an example, one approach to making a CNT film is to deposit nanotubes in a random pattern on a filter using water or other fluid. The uniformly dispersed CNT-containing mixture is passed or forced through the filter, leaving the nanotubes on the surface of the filter to form a nanotube structure or film. The size and shape of the resulting film is determined by the size and shape of the desired filtering area of ​​the filter, while the thickness and density of the film are determined by the quantity of nanotube material used in the process and the permeability of the filtering membrane to the components of the input CNT material, since the impermeable components are trapped on the surface of the filter. 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, and the average areal density of the resulting film can be determined by dividing the nanotube mass by the total filtering surface area. The filter selected is generally not permeable to any CNTs according to the embodiments of the present disclosure.

[0057] The filter-formed CNT films can be combinations of SWCNTs, DWCNTs, and / or MWCNTs in different compositions.

[0058] The CNT film is then removed from the filtration membrane in operation 105. More specifically, the carbon nanofibers may be randomly crossed to form an interconnected network structure in a planar orientation to form a thin CNT film.

[0059] In operation 106, the lifted CNT film is then collected using a collector frame and transferred and mounted directly onto virtually any solid substrate (e.g., a metal frame, a silicon frame, or a pellicle boundary with an aperture defined therein). The CNT film may be attached to the pellicle boundary and cover the aperture to form a pellicle. Mounting the transferred film onto a metal or silicon frame with a central opening as small as 1 cm x 1 cm may be useful. For practical EUV pellicles, there is a high demand for much larger films. Exemplary embodiments of the present disclosure address filtered CNT pellicle films that have a structure different from known prior art while exhibiting properties that meet or exceed certain aspects of EUV lithography requirements. Certain aspects of EUV lithography requirements include, without limitation, EUV transmittance (EUVT), low scattering, and lifetime testing.

[0060] This pellicle film structure results in an ultra-thin pellicle film that allows for very high EUVT (e.g., greater than 88%, 92%, or 95%) while being extremely temperature resistant (e.g., resistant to temperatures above 450° C.) and mechanically robust. In examples, the minimum EUVT can be 88% or greater. Although the disclosure above has been shown for CNTs and aqueous solutions, aspects of the disclosure are not limited thereto and different nanotubes (e.g., boron nitride nanotubes (BNNTs)) may be used with the same principles.

[0061] The aforementioned thin films may be conformally coated by various methods, such as, but not limited to, E-beam, chemical vapor deposition, atomic layer deposition, spin coating, dip coating, spray coating, sputtering, DC sputtering, and RF sputtering. The material may be a metallic element, including any one of the following: silicon, SiO2, SiON, boron, ruthenium, boron, zirconium, niobium, molybdenum, rubidium, yttrium, YN, Y2O3, strontium, and / or rhodium. The material may be any one of a metal, a metal oxide, or a nitride. However, aspects of the present disclosure are not limited thereto, and a combination of materials may be used in the coating.

[0062] According to an exemplary embodiment of the present disclosure, the thin films described above, such as nanotube films, can be coated with a zirconium layer having a thickness of about 1.5 nm or less on one or both sides of the nanotube film.

[0063] However, aspects of the present disclosure are not so limited, and the zirconium coating layer may be 1.5 nm thick or less than 1 nm thick on a single side of the nanotube film, or 0.3 nm on each side.

[0064] Electron Beam Evaporation Coating Electron beam (E-beam) evaporation is a physical vapor deposition technique for evaporating source materials using high energy electrons in the form of an intense beam. The E-beam machine causes thermionic emission of electrons, which after this facilitation can provide enough energy to evaporate any material, in this example, yttrium, ruthenium, or zirconium metals. At the start of the process, the metal element sample is mounted on a rotating planetary fixture. The fixture is loaded onto a carrier in the E-beam chamber. The crucible(s), the container that holds the material to be evaporated for coating, is placed in its holder. The shutter of the holder is closed, and then the E-beam chamber is closed.

[0065] Chamber 5 x 10-6 The pressure is pumped down to below 1000 MPa (1.2 Pa). The selected film thickness is then input into the device. The E-beam gun is powered up to generate an electron current that is directed at the material inside the crucible. The current is then increased until the material begins to melt. For the deposition process, a specific current is applied for each metallic element selected as the different metallic materials (e.g., yttrium or zirconium) usually have different melting temperatures.

[0066] The planet carrier is then rotated, the crucible shutter is opened, and the current is further increased so that deposition begins after the material has melted. E-beam machines are typically equipped with a deposition thickness monitor.

[0067] Once the monitored thickness reaches a preselected target value, the shutter is closed, the current is reduced to zero, and the system is allowed to cool the chamber before venting to atmosphere.

[0068] The thickness of the coating may be monitored by the amount of metal element deposited on the target surface. The amount of element applied on the coating area determines the coating areal density. Once a predetermined coating areal density is reached, the coating process is stopped and the coating is complete.

[0069] Magnetron Sputtering Coating Magnetron sputtering presents the ability to deposit dense, defect-free coatings of desired materials at high deposition rates. It begins with placing the selected coating material (which may be niobium) on a magnetron inside a vacuum chamber. The magnetron is an electron tube for amplifying or generating microwaves using electrons that are controlled by an external magnetic field. The chamber is filled with an inert gas. A negative charge is applied to the magnetron, ultimately causing the ejection of targeted Nb molecules. These targeted molecules are then collected on a substrate, for example a CNT film.

[0070] Surface coating methods are also referred to herein as surface deposition, but aspects of the present disclosure are not limited to the above list. The embodiments of the present invention are not limited to physical vapor deposition (PVD) E-beam and magnetron sputtering. Other PVD methods include, but are not limited to, thermal evaporation, remote plasma sputtering, electrochemical deposition, and electroplating. In addition, atomic layer deposition and chemical vapor deposition may be applicable to achieve thin layer coating or deposition on nanotube surfaces.

[0071] Thin Film Thickness Exemplary embodiments of the present disclosure are further analyzed for their thickness, which is important to determine and ensure high EUVT. More specifically, the Dimension Icon AFM instrument was first calibrated against a National Institute of Standards and Technology (NIST) traceable standard. CNT pellicle films with an area of ​​approximately 90 μm×90 μm were selected for AFM 2D and 3D height imaging. Step height analysis was performed to measure the film thickness. Three measurements were performed 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 objects was about 11.3±0.6 nm.

[0072] Furthermore, thickness values ​​of 3 nm to 100 nm, 3 nm to 40 nm, and 3 nm to 20 nm were obtained based on additional sets of measurements.

[0073] Additionally, in other samples, the thickness values ​​may be 3 nm to 100 nm, 3 nm to 40 nm, and 3 nm to 20 nm, but the embodiments of the present application are not limited thereto, and the range may be 3 nm to 5 nm at the lower end and 20 nm to 100 nm at the upper end.

[0074] Given the much higher mechanical strength exhibited by DWCNT-dominant CNT pellicle films, they may be constructed extremely thin to obtain higher EUVT values ​​without sacrificing mechanical strength or integrity for use in EUV scanners. The thinner the film, the less heat it may absorb and retain, and the longer it may last.

[0075] Visible and EUV transmittance Various properties of the Zr-coated CNT pellicle films were measured.

[0076] A 1 mm diameter light beam was used to collect visible light transmittance at 550 nm for each Zr-coated pellicle film tested. Each sample test was run multiple times and the average value was recorded.

[0077] Figure 2 shows the correlation between nanotube film areal density and the optical transmittance of the film at a visible light wavelength of 550 nm. From both the table and the chart in Figure 2, it can be seen that higher areal density results in lower visible light transmittance with a strong linear correlation. Variations in the average length, average diameter, and type of nanotubes used for suspension preparation may change the actual value of visible light transmittance. Visible light transmittance has a better and stronger linear correlation with EUV transmittance.

[0078] The EUV transmittance of the samples was measured using the current industry standard 13.5 nm wavelength. A full size 110 x 140 mm pellicle for EUV lithography may require a minimum of 4 measurements and up to 99 or more measurements to determine the EUVT and average EUVT variation. For an accurate EUV transmittance map, more measurements are preferred, such as 100 measurements. The EUV light beam has a spot size and shape of less than 2 mm diameter, or 1 mm x 2 mm. 2 The rectangular shape may be:

[0079] EUVT maps were generated based on the EUV scanning results to demonstrate and measure the variation and / or uniformity of the transmittance.

[0080] EUV pellicle life tests were performed under high intensity EUV irradiation on the coating and control samples. EUV irradiation was performed for 2.5 hours with an irradiation intensity of 13.4 w / cm 2 (corresponding to the intensity on the EUV mask when using a 600W light source) and 20 Pa of hydrogen gas. This is roughly equivalent to processing 13,000 wafers, and is 120 KJ / cm 2 can be considered to be equal to the total energy of the EUV irradiation.

[0081] Different or higher EUV energies, similar to a larger number of wafer exposures during the manufacturing process, may be further applied in other lifetime studies.

[0082] Also, the surface structure roughness of the pellicle film may be important for EUV photolithography performance and product yield. The rough surface modifies the diffraction intensity used for structure reconstruction based on rigorous calculation of EUV diffraction. In some embodiments, the rough reflective surface may be configured in such a way that the angular scattering profile meets EUV lithography requirements. One of the strict and critical thresholds for EUV lithography to ensure accurate manufacturing and printing results in the end is less than 0.2% scattering at an angle of 4.7 degrees according to the current industry standard. When considering other adaptive measures, less than 0.5% scattering may be acceptable.

[0083] At least one embodiment of the present disclosure was tested by EUV reflectance measurements for scattering tests and results.

[0084] Coated Pellicle Film The structure of the pellicle film results in an ultra-thin pellicle film. It allows for very high EUVT (e.g., greater than 92% or 95%) while being extremely temperature resistant (e.g., resistant to temperatures above 600°C) and mechanically robust. The filtration-formed CNT pellicle film can have different optical transmittances, which can range from 50% to 95% at 550 nm, depending on the total amount of input nanotube material. Pellicle films with high optical transmittances can exhibit very high EUV transmittances, typically greater than 88%, and in some cases, results of greater than 92%, or even greater than 95 or 98%. Both visible and EUV transmittances can correlate well with each other. At either visible or EUV wavelengths, one transmittance value can be extrapolated from the measurement of another transmittance value based on these correlations. In another example, a full sample scan of a full size pellicle film (approximately 110 mm x 144 mm or larger) shows an average of 96.69 ± 0.15% transmission, and a scan of a 1.5 mm x 1.5 mm central area gives an average of 96.75 ± 0.03% transmission. A more stringent criterion for evaluating EUVT uniformity is used to calculate the difference between any two EUVT measurements from the same nanotube film at any focal area. This requirement can be less than 5%, less than 2%, or even less than 1.0% or less. For a full size pellicle of this exemplary embodiment, multi-point EUVT uniformity test results (e.g., 100 point measurements per sample) show some extremely small variation of less than 1.5%, less than 0.9%, less than 0.6%, or less than 0.4%.

[0085] Nanotube pellicle films were coated with selected metal elements and tested with the results shown in Tables 1, 2, and 3. [Table 1]

[0086] According to an exemplary embodiment of the present disclosure, a first Zr-coated pellicle (Zr-1) as provided in Table 1 had a 1.0 nm thick Zr layer first deposited on one side of a CNT film by E-beam method. The nanotube film was rotated 180 degrees and the same material was deposited on the other side by the same process.

[0087] According to another exemplary embodiment of the present disclosure, a second Zr-coated pellicle (Zr-2) as provided in Table 1 had a 0.5 nm thick Zr layer deposited first, followed by another 0.5 nm thick Zr layer deposited on the opposite side of the nanotube film by the same E-beam deposition method.

[0088] According to one exemplary embodiment of the present disclosure, a yttrium coated pellicle as provided in Table 1 has a 1.0 nm thick layer of Y first deposited on one side of a CNT film, and then another 1.0 nm thick layer of Y is deposited by E-beam on the opposite side of the same film.

[0089] According to an exemplary embodiment of the present disclosure, a ruthenium coated pellicle as provided in Table 1 has a 1.5 nm thick Ru layer deposited on one side of the pellicle film by magnetron sputtering.

[0090] According to an exemplary embodiment of the present disclosure, an uncoated or pristine nanotube pellicle (UC-1) as provided in Table 1 has an average visible light transmission of 90.4% and a measured EUVT of about 96.7%.

[0091] All pellicle films of Zr-1, Zr-2, Y-coated, Ru-coated, and UC-1 were produced from the same batch of pristine samples with approximately the same areal density. The test results shown in Table 1 demonstrate at least one exemplary embodiment of the present disclosure. The Ru-coated film significantly reduced the visible light transmittance. The Ru-coated and Y-coated nanotube films have scattering test results of more than 0.4% at an angle of 4.7 degrees. Together with unstable life test results (i.e., the film breaks during the life test), the Ru-coated and Y-coated nanotube pellicles do not meet the EUV requirements compared to uncoated or Zr-coated nanotube films.

[0092] Further studies of Zr coatings were carried out and the test results are presented below and summarized in Tables 2 and 3. [Table 2]

[0093] According to one exemplary embodiment of the present disclosure, a third Zr-coated pellicle (Zr-3) has an average 1.6 nm thick Zr layer deposited on only one side of the CNT film. In one example, the Zr coating may be performed using a magnetron sputtering protocol. Furthermore, Zr-3 was measured to have an average visible light transmittance of about 90.0%. The film may be further coated on the other side by a magnetron sputtering protocol.

[0094] According to another exemplary embodiment of the present disclosure, a fourth Zr-coated pellicle (Zr-4) has a 0.3 nm thick Zr layer first deposited on one side of a CNT film, followed by another 0.3 nm thick Zr layer deposited on the opposite side of the same film by E-beam method. Zr-4 has a visible light transmittance of about 80.06%.

[0095] According to yet another exemplary embodiment of the present disclosure, a fifth Zr-coated pellicle (Zr-5) has a 0.3 nm thick Zr layer deposited first on one side of the CNT film, followed by another 0.3 nm thick Zr layer deposited on the opposite side of the same film by the same E-beam method. Zr-5 has a visible light transmittance of about 90.0%.

[0096] According to yet another exemplary embodiment of the present disclosure, a sixth Zr-coated pellicle (Zr-6) has a 0.3 nm thick Zr layer deposited first on one side of a CNT film, followed by another 0.3 nm thick Zr layer deposited on the opposite side of the same film by the same E-beam method. Zr-6 has a visible light transmittance of about 93.0%. [Table 3]

[0097] According to one exemplary embodiment of the present disclosure, a seventh Zr-coated pellicle (Zr-7) was formed by depositing 0.19 micrograms / cm of the Zr initially deposited on one side of the CNT film. 2 and then deposited by E-beam on the opposite side of the same film, with a coating areal density of 0.19 micrograms / cm 2 This is followed by another Zr coating having an areal density of 100.001 mm. Zr-7 has an average visible light transmittance of about 90.4%.

[0098] According to another exemplary embodiment of the present disclosure, an eighth Zr-coated pellicle (Zr-8) was formed by depositing 0.19 micrograms / cm of Zr initially on one side of the CNT film. 2 and then deposited on the opposite side of the same film by E-beam, with an areal density of 0.19 micrograms / cm 2 This is followed by another Zr coating having an areal density of 100.0%. Zr-8 has an average visible light transmittance of about 93.0%.

[0099] All coatings of any of the above exemplary embodiments, including the Zr-1 to Zr-8 pellicle films, have thicknesses less than 2 nanometers, and the Zr-4 to Zr-6 film coatings are in the sub-nanometer range. According to exemplary aspects, each layer by itself may not cover all possible areas or spots on the surface. According to one embodiment of the present disclosure, the coating thickness or coating areal density may be an average value that takes into account the process itself, possible process failures, and technical challenges and difficulties.

[0100] As shown in Table 2, pristine nanotube pellicles with average visible light transmittance of 90.3% (UC-2) and 93.1% (UC-3) have measured EUVTs of approximately 96.9% and 98.0%, respectively.

[0101] According to yet another aspect of the present disclosure, the coated nanotube pellicle film generally has a high EUV transmittance of 88% or more for Zr-4 to Zr-8. Pellicle films Zr-5 to Zr-8 have an EUVT of 93% or more, and Zr-6 has an EUVT of over 95%.

[0102] According to yet another aspect of the present disclosure, all pellicle films listed in Tables 2 and 3 were tested in the presence of hydrogen gas for a lifespan equivalent to at least 10,000 wafers at 600 watts of irradiation power (i.e., total energy of EUV irradiation is at least 100 kJ / cm). 2 ) without any damage.

[0103] At the time of filing this application, high resolution EUV photolithography below 0.7 nm is still under development. No consensus has been reached on the actual life test parameters for the industry standard. Higher wafer equivalent tests exceeding the 10,000 wafer equivalent tests detailed herein have been performed at 100 kJ / cm. 2 In at least one study, uncoated nanotube films according to one embodiment of the present disclosure were able to withstand a 32,000 wafer equivalent life test (288 kJ / cm2 The nanotube film was destroyed at 1.0 nm total energy of EUV irradiation, while the thin Zr coating (1.0 nm thick coating on each side of the film) remained intact.

[0104] As shown, the Zr coating of the ultra-thin nanotube pellicle and pellicle film according to an exemplary embodiment of the present application constitutes an ultra-thin nanotube based EUV pellicle having a Zr coating with an average thickness of 0.3 nm.

[0105] Table 2 shows the lifetime test equivalent to 10,000 wafers at 600 watts irradiation power in the presence of hydrogen gas (total energy of EUV irradiation 100 kJ / cm 2 ) are illustratively shown. They have low EUV scattering results of less than 0.2% measured at an angle of 4.7 degrees, and different film densities with visible light transmission ranging from approximately 80% to 93% at 550 nm.

[0106] Table 3 shows the results for 100 kJ / cm 2 The data exemplarily represents data from a nanotube pellicle that survived a life test with a total energy of EUV irradiation of 100 nm and had a scattering of less than 0.2% measured at an angle of 4.7 degrees, and a film density with a visible light transmission of approximately 90%-93% at 550 nm.

[0107] 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 the products and methods constituting the products or methods described herein. Many other embodiments may become apparent to those skilled in the art upon review of the present disclosure. Since other embodiments may be utilized and derived from the present disclosure, structural and logical substitutions and changes may be made without departing from the scope of the present disclosure. Furthermore, the illustrations are merely representative and may not be drawn to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be minimized. Thus, the present disclosure and figures should be considered illustrative rather than limiting.

[0108] One or more embodiments of the present disclosure may be referred to herein, individually and / or collectively, by the term "invention" merely for convenience and without any intention to spontaneously limit the scope of the present application to any particular invention or inventive concept. In addition, although specific embodiments have been illustrated and described herein, it will be understood that any subsequent arrangements designed to achieve the same or similar purpose may be substituted for the specific embodiment shown. The present disclosure is intended to cover any and all subsequent adaptations or variations of the various embodiments. Combinations of the foregoing embodiments, as well as other embodiments not specifically described herein, will be apparent to one of ordinary skill in the art upon review of this description.

[0109] 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, the foregoing Detailed Description may group or describe various features together in a single embodiment for the purpose of streamlining the disclosure. This disclosure should not 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.

[0110] The foregoing disclosed subject matter should be considered as illustrative and not limiting, and the appended claims are intended to cover all such modifications, extensions, and other embodiments that fall within the true spirit and scope of the present disclosure. Accordingly, to the maximum extent permitted by law, the scope of the present disclosure should be determined by the broadest permissible interpretation of the following claims and their equivalents, and should not be limited or restricted by the foregoing detailed description.

Claims

1. 1. An extreme ultraviolet (EUV) photolithographic nanotube film comprising a plurality of nanotubes, The EUV photolithographic nanotube film, wherein the nanotubes randomly intersect to form an interconnected network structure in a planar orientation, the interconnected network structure having a thickness ranging from a lower limit of 3 nm to an upper limit of 100 nm, and the zirconium coating layer is deposited on the interconnected network structure.

2. 10. The EUV photolithographic nanotube film of claim 1, wherein the zirconium coating layer has a thickness of 1.6 nm or less on at least one side of the interconnected network structure.

3. 10. The EUV photolithographic nanotube film of claim 1, wherein the zirconium coating layer has an average thickness between 0.5 nm and 1.0 nm.

4. 10. The EUV photolithographic nanotube film of claim 1, wherein the zirconium coating layer has an average thickness between 0.3 nm and 0.5 nm.

5. 10. The EUV photolithographic nanotube film of claim 1, wherein the zirconium coating layer has an average thickness of 0.3 nm.

6. The areal density of the zirconium coating layer is 0.19 micrograms / cm on each side of the interconnected network structure. ２ 10. The EUV photolithographic nanotube film of claim 1, wherein:

7. 10. The EUV photolithographic nanotube film of claim 1, wherein the EUV photolithographic nanotube film has an EUV scattering of less than 0.5% at an angle of 4.7 degrees.

8. 10. The EUV photolithographic nanotube film of claim 1, wherein the EUV photolithographic nanotube film has an EUV scattering of less than 0.2% at an angle of 4.7 degrees.

9. 10. The EUV photolithographic nanotube film of claim 1, wherein the average thickness of the interconnected network structure is in the range of 11 nm to 40 nm.

10. 10. The EUV photolithographic nanotube film of claim 1, wherein the interconnected network structure has an average thickness of 11 nm.

11. 10. The EUV photolithographic nanotube film of claim 1, wherein the interconnected network structure has a 550 nm light transmittance of at least 80% prior to zirconium coating.

12. 10. The EUV photolithographic nanotube film of claim 1, wherein the interconnected network structure with the zirconium coating layer has an EUV transmittance of at least 88%.

13. 10. The EUV photolithographic nanotube film of claim 1, wherein the interconnected network structure with the zirconium coating layer has an EUV transmittance of at least 95%.

14. the plurality of nanotubes further include single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes; 2. The EUV photolithography nanotube film of claim 1, wherein the number of layers of the single-walled carbon nanotubes is one, the number of layers of the double-walled carbon nanotubes is two, and the number of layers of the multi-walled carbon nanotubes is three or more.

15. 15. The EUV photolithography nanotube film of claim 14, wherein the single-walled carbon nanotubes account for 20-40% of the total carbon nanotubes, the double-walled carbon nanotubes account for 50% or more of the total carbon nanotubes, and the remaining carbon nanotubes are the multi-walled carbon nanotubes.

16. The interconnected network structure having the zirconium coating layer has an energy density of at least 100 kJ / cm after EUV irradiation. ２ 10. The EUV photolithographic nanotube film of claim 1, wherein the nanotube film remains intact within an amount of 0.1 to 100 μm.

17. 10. A method of performing EUV photolithography comprising transmitting EUV radiation through the EUV photolithographic nanotube film of claim 1.

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