Multilayered Composite Membranes Based on Layer‐by‐Layer Stacked Graphene Films for Ultraviolet Pellicle Applications (Adv. Funct. Mater. 4/2026)

Graphene is a promising material for next‐generation extreme ultraviolet (EUV) pellicles due to its excellent optical transparency, mechanical, and thermal stability under intense EUV radiation. However, challenges remain in precisely controlling its thickness at large scales and preventing hydrogen radical‐induced degradation. In this study, a multilayer graphene composite with protective capping layers, enabling nanometer‐scale thickness control is devloped. A 10‐layer, 5 nm thick graphene film achieves ≈92% transparency and an effective Young's modulus of 220 GPa. When integrated into a free‐standing molybdenum (Mo)/graphene/silicon nitride (SiN) composite, the Young's modulus increases by 29%, and the fracture load improves by 840% compared to a single‐layer SiN membrane. Molecular dynamics simulations confirm that the enhanced mechanical strength mainly results from graphene's intrinsic properties. Additionally, a full‐size pellicle with five graphene layers and a 100 nm SiN layer are fabricated, which maintains over 90% EUV transparency on a 7 nm SiN substrate. These results suggest that multilayer graphene membranes can overcome current EUV pellicle limitations and support the broader commercialization of EUV lithography in the near future.

Extreme ultraviolet (EUV) lithography is considered to be the most effective strategy for realize 7 nm generation manufacturing and beyond. A key factor for the realization of EUV lithography is the choice of EUV resist material that is capable of resolving below 15-nm half pitch with high sensitivity. Chemical Amplified Resist (CAR) using positive-tone development (PTD) is still one of the strongest candidates for EUV lithography. Recently, some researchers have reported concerns on the limitations in the performance of CAR materials. Consequently, there is a critical need for new chemistry and development of new resist materials. However, new resist materials still have lots of concerns for manufacturing, such like a non-CAR materials including metal resist. Therefore, CAR materials are still most important items for EUV lithography manufacturing. We’ve been developing negative-tone imaging (organic solvent development) with EUV exposure (EUV-NTI) for a long time. EUV-NTI has advantages for line-width roughness (LWR) due to their low swelling and dissolving smoothly. New EUV-NTI performances will be shown and also process condition progress will be updated. Also, the basic study will be reported, which is high absorption unit including materials for improving stochastic effect. We report herein recent progress of CAR materials, both positive-tone and negative-tone for EUV lithography.

To reduce the influence of carbon contamination growth, which is the origin of the resist outgassing during extreme ultraviolet (EUV) exposure, it is necessary to study the relationship between the outgassing species from the resist and carbon contamination growth during EUV exposure. Thus a novel evaluation system which enable the measurement of the carbon contamination thickness on a Mo/Si multilayer witness sample by in-situ ellipsometry in the resist outgassing environment under EUV exposure was installed at the beamline in the NewSUBARU synchrotron radiation facility. The carbon contamination thickness on the witness sample measured by in-situ ellipsometry is in good agreement with those measured using an atomic microscope and by reflectivity measurement. In addition, it is found that the time dependence of the carbon growth on a witness sample is due to the difference in outgassing species from the resist samples during EUV exposure. Furthermore, for the model resist of poly(hydroxystyrene) containing the protectiive group of tertial butoxycarbonyl group with a photoacid generator (PAG) and a quencher, the time dependence of contamination thickness was mainly due to the decomposition of outgassing species of the tert-butoxycarbonyl group and the residual casting solvent, such as propyleneglycol monomethyl ether acetate. In order to evaluate the carbon contamination thickness measurement, the in-situ measurement system was moved to the 10.8-m-long undulator beamline. The EUV light intensity flux was estimated to be the same level as that required in high-volume manufacturing.

Extreme ultraviolet (EUV) lithography uses 13.5 nm light to reach the sub-20 nm resolution. However, the process of pattern formation induced by this high-energy light is not well-understood. In this work, we provide an inorganic EUV photoresist with fluorescence properties by introducing a carbazole derivative as a ligand, and we study its effect on the patterning process. Using the fluorescence properties, changes in the emission of the material after EUV exposure could be tracked by means of spectroscopy and microscopy. The resist sensitivity was substantially reduced by the incorporation of the carbazole benzoate ligands, which is attributed to hole trapping and steric hindrance. After EUV irradiation of the resist films, infrared, UV-visible absorption, and fluorescence spectroscopies showed that the carbazole units were still mostly intact, although their fluorescence intensity was lowered. Our work shows that fluorescent labeling can provide relevant mechanistic insights in the patterning process of resists, potentially with a molecular resolution.

Poly(vinyl alcohol) (PVA) biaxially stretched film has the advantages of being environmentally friendly, having high mechanical strength, and possessing excellent oxygen barrier properties, so it can be widely used in theory. However, the poor water resistance limits its practical application in barrier packaging for food and pharmaceuticals. To fully utilize the high barrier properties of PVA, herein, our independently developed PVA biaxially stretched (BOPVA) film was adopted as a barrier layer for polyethylene (PE) film, and maleic anhydride‐grafted polyethylene (PE‐g‐MAH) was used as an interfacial adhesive. In this way, a PE/BOPVA/PE multilayer composite film was fabricated, and the effects of MAH content, lamination time, temperature, and pressure on interfacial morphology and peel strength of the multilayer composite film were systematically investigated. The interfacial peel strength between BOPVA film and PE film was effectively enhanced to 28.5 N/15 mm, and the tensile strength and modulus of the obtained multilayer composite film respectively reached 52.4 MPa and 1.38 GPa. The multilayer composite film also presented high puncture strength (85.3 N/mm) and low oxygen permeability coefficient (5.6 × 10 −17 cm 3 ·cm/[cm 2 ·s·Pa]). All of the above properties surpassed those of commercially available EVOH/PA/PE multilayer film, demonstrating the significant potential of PE/BOPVA/PE multilayer composite film for packaging applications.

We synthesized three type polymers 1) Poly hydroxyl-styrene (PHS resist). 2) hydroxyl-styrene methacrylate copolymer (Hybrid resist). 3) methacrylic acid tertiary aliphatic esters copolymer (Methacrylate resist). These polymers have been used in ArF, KrF lithography. Recently, these resists have been investigated to employ for Extreme ultra violet (EUV) lithography because absorption of EUV doesn’t depend on the molecular structure. But EUV has very higher energy than ArF, KrF and it is exceed ionization potential of resist materials. Thus, polymer behavior under the EUV exposure is different from ArF, KrF exposure. For analyzing difference between ArF, KrF and EUV, we conducted to exposed resist materials (PHS, Hybrid, Methacrylate resist) using electron beam (EB) radiation source. As the results, we observed PHS resist showed crosslinking behavior less than 5μ C/cm² , Hybrid resist showed cross-linking behavior more than 20μ C/cm², Methacrylate resist showed moderate main chain scission behavior less than 20μ C/cm² respectively.

In this study, we evaluated the feasibility of incorporating elements with high extreme ultraviolet (EUV) absorption cross sections into chemically amplified photoresist (CAR) formulations to mitigate the sensitivity degradation characteristic of EUV lithography (EUVL), particularly in efforts aimed at reducing photon shot noise. We designed experiments to identify high-absorption elements that enhance the radiolysis of photoacid generators (PAGs) under EUV exposure. Bilayer stacks comprising a fluoroalkylated polymer overcoat doped with candidate elements atop an acid-labile polymer underlayer were exposed to EUV radiation, post-exposure baked, and developed. Varying the overcoat composition revealed that iodine (I) increased the underlayer's solubility, whereas tin (Sn) produced no comparable effect. Guided by this result, we synthesized an iodine-containing radiosensitizer, IOH-A, by introducing acid-cleavable acetal groups into iohexol, a radiocontrast agent used in computed tomography angiography. Incorporating IOH-A into CAR formulations, followed by compositional optimization, yielded a 2.6% improvement in sensitivity and a 12% reduction in line-edge roughness (LER) during EUVL patterning. These results demonstrate a practical strategy to relax the long-standing sensitivity-LER trade-off in EUVL using CARs and propose IOH-A as a promising design motif for next-generation CAR systems.

Extreme ultraviolet (EUV) lithography is crucial to enabling technology scaling in pitch and critical dimension (CD). Currently, one of the key challenges of introducing EUV lithography to high volume manufacturing (HVM) is throughput, which requires high source power and high sensitivity chemically amplified photoresists. Important limiters of high sensitivity chemically amplified resists (CAR) are the effects of photon shot noise and resist blur on the number of photons received and of photoacids generated per feature, especially at the pitches required for 7 nm and 5 nm advanced technology nodes. These stochastic effects are reflected in via structures as hole-to-hole CD variation or local CD uniformity (LCDU). Here, we demonstrate a synergy of film stack deposition, EUV lithography, and plasma etch techniques to improve LCDU, which allows the use of high sensitivity resists required for the introduction of EUV HVM. Thus, to improve LCDU to a level required by 5 nm node and beyond, film stack deposition, EUV lithography, and plasma etch processes were combined and co-optimized to enhance LCDU reduction from synergies. Test wafers were created by depositing a pattern transfer stack on a substrate representative of a 5 nm node target layer. The pattern transfer stack consisted of an atomically smooth adhesion layer and two hardmasks and was deposited using the Lam VECTOR PECVD product family. These layers were designed to mitigate hole roughness, absorb out-of-band radiation, and provide additional outlets for etch to improve LCDU and control hole CD. These wafers were then exposed through an ASML NXE3350B EUV scanner using a variety of advanced positive tone EUV CAR. They were finally etched to the target substrate using Lam Flex dielectric etch and Kiyo conductor etch systems. Metrology methodologies to assess dimensional metrics as well as chip performance and defectivity were investigated to enable repeatable patterning process development. Illumination conditions in EUV lithography were optimized to improve normalized image log slope (NILS), which is expected to reduce shot noise related effects. It can be seen that the EUV imaging contrast improvement can further reduce post-develop LCDU from 4.1 nm to 3.9 nm and from 2.8 nm to 2.6 nm. In parallel, etch processes were developed to further reduce LCDU, to control CD, and to transfer these improvements into the final target substrate. We also demonstrate that increasing post-develop CD through dose adjustment can enhance the LCDU reduction from etch. Similar trends were also observed in different pitches down to 40 nm. The solutions demonstrated here are critical to the introduction of EUV lithography in high volume manufacturing. It can be seen that through a synergistic deposition, lithography, and etch optimization, LCDU at a 40 nm pitch can be improved to 1.6 nm (3-sigma) in a target oxide layer and to 1.4 nm (3-sigma) at the photoresist layer.

Relying on reflective mask technology, extreme-ultraviolet (EUV) lithography is particularly vulnerable to mask substrate roughness. Previous research has shown mask roughness to play a significant role in printed line-edge roughness (LER). Here the analysis of mask-roughness effects is extended to printed contact-size variations. Unlike LER, illumination partial coherence is found to have little affect on the results for contacts that are near the diffraction limit. Analysis shows that, given the current state-of-the-art EUV mask, mask roughness has a significant effect on the process window for small contacts. The analysis also shows that a significant portion of the contact-size variation observed in recent 0.1-numerical-aperture EUV exposures can be attributed to the mask-roughness effect studied here.

Implementation of extreme ultra violet lithography (EUVL) for printing features of dimensions around 32nm and below has faced multiple challenges that have been overcome mostly through tool and process engineering. Currently, the main concern for implementation of EUVL in high volume manufacturing is related to stochastic defects, such as line bridges or breaks, which may occur randomly and have an impact on device performance.1 Photon shot noise, in addition to the inherent process variability and material non-homogeneities can lead to defects on the final patterned structures. As the pitch and critical dimension (CD) approach 32nm pitch and below, the dependency of stochastics defects increases exponentially. This paper fits within imec’s EUV stochastics and defectivity program, which investigates the key parameters for the generation and mitigation of defects from both a theoretical and practical approach. Initially, a reference process has been established and a methodology has been developed to capture and characterize bridge-type defects after pattern transfer into relevant layers for metrology and applications. Optical inspection and scanning electron microscopy (SEM) review are used to collect information on the number and types of defects present over large patterned areas (in the order of cm2). With a well-defined inspection technique, experiments related to fundamentals as well as materials and processes are continuously run. In the past years, imec has been leading the fundamental work on stochastic defects.2,3 De Bisschop et al. identified the “defect cliff”, or the exponential dependency of defect density as a function of space CD for multiple parameters, such as resist formulation and exposure/imaging conditions. More recently, the focus has changed to the investigation of the “defect floor”, which as the name suggests, is a flat response of defects to CD. The defect floor suggests that defectivity cannot be further improved, making one of the most relevant problems to solve for implementation of EUV in high volume manufacturing (HVM). Our results show a decomposition of the potential contributors to explore the effect of processing conditions related to scanner, track and pattern transfer on final defect density for a chemically amplified resist and attempt a comparison to a metal-oxide resist. Goal is to understand the contributors to the defect floor and identify an effective route to avoid/minimize defect formation.

Extreme ultraviolet (EUV) lithography is considered as the leading patterning technology beyond the ArF-based optical lithography, addressing the need for transistor densification to meet Moore's Law. Theoretically, EUV lithography at 13.5nm wavelength meets the resolution requirements for 1xnm technology nodes. However, there are several major challenges in the development of EUV lithography for mass production of advanced CMOS devices. These include the development of high power EUV light sources, EUV optics, EUV masks, EUV resists, overlay accuracy, and metrology and inspection capabilities. In particular, it is necessary to ensure that effective defect control schemes will be made available to reduce the EUV lithography defectivity to acceptable levels. This paper presents a study on the wafer defectivity and characterization of patterned EUV resists, with the objective of providing a quantitative comparison between the defectivity of different resist materials and different stacks. Patterned wafers were printed using the ASML® EUV full-field Alpha-Demo Tool (ADT 0.25 NA) at imec. The EUV resist patterns were 32nm line/spaces. Several advanced resist types were screened experimentally. The different resist types and stacks were inspected using a DUV laser based brightfield inspection tool, followed by a SEM defect review and CD metrology measurements. The patterns were characterized in terms of defect types and defect density. We identified the major defect types and discuss factors that affect the defectivity level and pattern quality, such as resist type, exposure dose and focus. Defect scattering analysis of DUV polarized light at different polarizations was performed, to indicate on the inspection performance trends for a variety of defect types and sizes of the different resists and stacks. The scattering analysis shows that higher defect scattering is induced using polarized light.

The following topics are dealt with: low-power electronics; Internet of Things; integrated circuit design; video coding; integrated circuit manufacture; CMOS integrated circuits; field programmable gate arrays; magnetic sensors; calibration; power consumption.

The performance of beryllium-based multilayer coatings designed to reflect light of wavelengths near 11 nm, at normal incidence, is presented. These multilayer coatings are of special interest for extreme ultraviolet lithography (EUVL). The beryllium-based multilayers investigated were Mo/Be, Ru/Be and a new material combination Mo,CiBe. The highest reflectivity achieved so far is 70% at 11.3 mn with 70 bilayers of Mo/Be. However, even though high reflectivity is very important, there are other parameters to satisfy the requirements for an EUVL production tool. Multilayer stress, thermal stability, radiation stability and long term reflectance stability are of equal or greater importance. An experimental characterization of several coatings was carried out to determine the reflectivity, stress, microstructure, and long term stability of these coatings. Theoretically calculated reflectivities are compared with experimental results for different material pairs; differences between experimental and theoretical reflectivities and bandwidths are addressed. Keywords: Extreme ultraviolet (EUV) lithography, reflective coatings, multilayer deposition, beryllium.

Asahi Glass Company (AGC) has been developing the extreme ultra violet (EUV) lithography mask blank and polished substrate since 2003, including the developments of all essential materials and processes: the low thermal expansion material (LTEM), the material developments of the reflective, capping and absorber films, the process developments of the substrate polishing, cleaning, film deposition and resist film coating processes. In this paper, we present the current development status of the full-stack EUV mask blank and polished substrate which are the most suitable for the EUV lithography process development with EUV pre-production exposure tools. We report the development progress of the reflective multilayer-coated LTEM substrate by showing its critical performances with those of 2010 achievements, which include the substrate flatness, the EUV optical properties of the Mo/Si reflective layers and the defect of LTEM substrate and reflective layer. The performances of the Ta-based absorber and the resist films are explained as well to show the readiness of the EUV mask blank suitable for various kinds of process developments of the EUV lithography.

As Extreme ultraviolet (EUV) lithography technology shows promising results below 40nm feature sizes, TOKYO ELECTRON LTD.(TEL) is committed to understanding the fundamentals needed to improve our technology, thereby enabling customers to meet roadmap expectations. TEL continues collaboration with imec for evaluation of Coater/Developer processing sensitivities using the ASML Alpha Demo Tool for EUV exposures. The results from the collaboration help develop the necessary hardware for EUV Coater/Developer processing. In previous work, processing sensitivities of the resist materials were investigated to determine the impact on critical dimension (CD) uniformity and defectivity. In this work, new promising resist materials have been studied and more information pertaining to EUV exposures was obtained. Specifically, post exposure bake (PEB) impact to CD is studied in addition to dissolution characteristics and resist material hydrophobicity. Additionally, initial results show the current status of CDU and defectivity with the ADT/CLEAN TRACK ACT^TM 12 lithocluster. Analysis of a five wafer batch of CDU wafers shows within wafer and wafer to wafer contribution from track processing. A pareto of a patterned wafer defectivity test gives initial insight into the process defects with the current processing conditions. From analysis of these data, it's shown that while improvements in processing are certainly possible, the initial results indicate a manufacturable process for EUV.