Lithography Applications Research Articles

Improving the Lithography Sensitivity of Atomically Precise Tin-Oxo Nanoclusters via Heterometal Strategy.

Tin-oxo clusters are increasingly recognized as promising materials for nanolithography technology due to their unique properties, yet their structural impacts on lithography performance remain underexplored. This work explores the structural impacts of heterometal strategies on the performance of tin-oxo clusters in nanolithography, focusing on various metal dopants and their coordination geometries. Specifically, SnOC-1(In), SnOC-1(Al), SnOC-1(Fe), and SnOC-2 were synthesized and characterized. These clusters demonstrate excellent solubility, dispersibility, and stability, facilitating the preparation of high-quality films via spin-coating for lithographic applications. Notably, this work innovatively employs nano-infrared (nano-IR), neutron reflectivity (NR), and X-ray reflectivity (XRR) measurements to confirm film homogeneity. Upon electron beam lithography (EBL), all four materials achieve 50 nm line patterns, with SnOC-1(In) demonstrating the highest lithography sensitivity. This enhanced sensitivity is attributed to indium dopants, which possess superior EUV absorption capabilities and unsaturated coordination environments. Further studies on exposure mechanisms indicated that Sn-C bond cleavage generates butyl free radicals, promoting network formations that induce solubility-switching behaviors for lithography. These findings underscore the efficacy of tailored structural design and modulation of cluster materials through heterometal strategies in enhancing lithography performance, offering valuable insights for future material design and applications.

Improving the Lithography Sensitivity of Atomically Precise Tin‐Oxo Nanoclusters via Heterometal Strategy

Tin‐oxo clusters are increasingly recognized as promising materials for nanolithography technology due to their unique properties, yet their structural impacts on lithography performance remain underexplored. This work explores the structural impacts of heterometal strategies on the performance of tin‐oxo clusters in nanolithography, focusing on various metal dopants and their coordination geometries. Specifically, SnOC‐1(In), SnOC‐1(Al), SnOC‐1(Fe), and SnOC‐2 were synthesized and characterized. These clusters demonstrate excellent solubility, dispersibility, and stability, facilitating the preparation of high‐quality films via spin‐coating for lithographic applications. Notably, this work innovatively employs nano‐infrared (nano‐IR), neutron reflectivity (NR), and X‐ray reflectivity (XRR) measurements to confirm film homogeneity. Upon electron beam lithography (EBL), all four materials achieve 50 nm line patterns, with SnOC‐1(In) demonstrating the highest lithography sensitivity. This enhanced sensitivity is attributed to indium dopants, which possess superior EUV absorption capabilities and unsaturated coordination environments. Further studies on exposure mechanisms indicated that Sn–C bond cleavage generates butyl free radicals, promoting network formations that induce solubility‐switching behaviors for lithography. These findings underscore the efficacy of tailored structural design and modulation of cluster materials through heterometal strategies in enhancing lithography performance, offering valuable insights for future material design and applications.

Novel low-temperature and high-flux hydrogen plasma source for extreme-ultraviolet lithography applications

Inside extreme-ultraviolet (EUV) lithography machines, a hydrogen plasma is generated by ionization of the background gas by EUV photons. This plasma is essential for preventing carbon build-up on the optics, but it might affect functional performance and the lifetime of other elements inside the machine. The interaction of scanner materials and components with hydrogen plasma is investigated in controlled experiments using laboratory (off-line) setups, where the properties of EUV-generated plasmas are mimicked. Here, we present a novel experimental setup at TNO, where a low-temperature hydrogen plasma is generated by means of electron-impact ionization using a high-current, high-pressure electron beam (e-beam) gun. We show that the produced ion flux, peak ion energies, and radical-to-ion ratio are similar to that of the EUV-generated plasma. Since the e-gun has the option of operating the e-gun in the pulsed mode, it is possible to reproduce the time-dependent behavior of the scanner plasma as well. Moreover, as shown by Luo et al. [RSC Adv. 10, 8385 (2020)], electrons that impinge on surfaces mimic EUV photons in the generation of secondary electrons, which often drive radiation-induced processes (e.g., surface oxidation, reduction, and growth of carbon). We conclude that e-beam generated hydrogen plasma is a very promising technology for cost-effective lifetime testing of materials and optics, as compared to setups with EUV sources.

Additive-Assisted Forming High-Quality Thin Films of Sn-Oxo Cluster for Nanopatterning.

Recently, metal-oxo clusters (MOCs) have attracted significant interest in fabricating nanoscale patterns in semiconductors via lithography. However, many MOCs are highly crystalline, making it difficult for them to form films and hindering subsequent nanopatterning processes. In this study, we developed a novel and simple method to enhance the film-forming ability of aromatic tetranuclear Sn-oxo clusters by adding additives. Theoretical calculations and Fourier-transform infrared (FTIR) analysis revealed the formation of intermolecular hydrogen bonds between the Sn-oxo clusters and additives, which induced a crystal-gel phase transition at -20 °C, thereby inhibiting the easy crystallization of the Sn-oxo clusters. High-quality and uniform thin films with surface roughness below 0.3 nm were prepared via spin coating. The obtained thin films exhibited good lithographic performance under deep ultraviolet (DUV), electron beam, and extreme-ultraviolet irradiation without a photo acid generator/photoinitiator, and 13- and 21 nm-wide line patterns were obtained on the films via electron-beam and extreme-ultraviolet lithographies. This study will pave the way for the further investigation of novel MOCs for advanced lithography and other thin-film applications.

Directed Self-Assembly of Polystyrene-Block-Polyhedral Oligomeric Silsesquioxane Monolayer by Nano-Trench for Nanopatterning.

This work pioneers to combine fast self-assembly of polyhedral oligomeric silsesquioxanes (POSS) nanocage-based giant surfactants with high etching contrast and directed self-assembly for reliable long-range lateral order to create well-aligned sub-10nm line nanopatterns via reactive ion etching (RIE). Polystyrene-block-oligo(dimethylsiloxane) substituted POSS (PS-b-oDMS7POSS) with seven oligo(dimethylsiloxane) at the corners of the POSS nanocage and one polystyrene (PS) tail is designed and synthesized as a giant surfactant with self-assembly behaviors like block copolymer (BCP). In contrast to BCP, oDMS7POSS gives a volume-persistent "nanoatom" particle with higher mobility for fast self-assembly and higher segregation strength with PS for smaller feature size. By taking advantage of directed self-assembly using nano-trench fabricated by electron beam lithography, well-ordered nanostructured monolayer with well-aligned parallel oDMS7POSS cylinders can be formed by confined self-assembly within the nano-trench. With the optimization of the RIE treatment using O2 as an etchant, the high etching contrast from the oDMS7POSS and PS gives the formation of well-defined line nanopatterns with sub-10nm critical dimension that can serve as a mask for pattern transfer in lithography. These results demonstrate a cost-effective approach for nanopatterning by utilizing a creatively designed giant surfactant with sub-10nm feature size and excellent etching contrast for modern lithographic applications.

Synthesis of micro-crosslinked adamantane-containing matrix resins designed for deep-UV lithography resists and their application in nanoimprint lithography.

A certain type of photoresist used for deep-UV lithography (DUVL) can also be used for other types of photolithography. Thus, to meet the requirements of two or more lithography technologies simultaneously, it is necessary to design a variety of corresponding functional groups in the molecules of materials and obtain the required properties. Herein, we designed four matrix resins based on acrylate for DUVL, employing alkyl sulfide, adamantane, methyladamantane, and hydroxyl as dangling groups and a microcrosslinking network by adding a small amount of crosslinker. These polymers were used in the thermal nanoimprint lithography (NIL) process, and distinct patterns with a resolution of 100 nm were observed. The acrylate copolymers designed for DUVL in this work can be used as thermal NIL resists and to obtain good patterns. It was found that ethylene dimethacrylate (EDMA) and adamantane endowed the matrix resins with good thermal stability and that PMMHM demonstrated the best patterning performance among the four resins. These polymers can be applied in the manufacturing of high-density integrated circuits, nano-transistors, optoelectronic devices and other components in the future.

Confirming the theoretical foundation of steady-state microbunching

Steady-State Microbunching (SSMB) has been proposed as a concept to generate coherent synchrotron radiation at an electron storage ring. SSMB promises to supply kilowatt level average power radiation in the extreme ultraviolet regime, meeting the power level demands for lithography applications that presently cannot be fulfilled by established accelerator technologies. SSMB is under theoretical and experimental study, building on a proof-of-principle (PoP) experiment at the Metrology Light Source which previously showed the viability of the idea. Here we report experimental findings from systematic studies in the ongoing SSMB PoP experiment, where microbunching is generated from an energy modulation imposed by a laser of wavelength 1064 nm. The results confirm the expected dependence of the microbunching process on modulation amplitude and show that the influence of transverse-longitudinal coupling dynamics is as predicted. This confirmation of key parts of the SSMB theory establishes a solid footing for continuing the proof-of-principle efforts towards the goal of constructing a prototype SSMB light source facility.

A perspective on deep-ultraviolet nonlinear optical materials

Deep ultraviolet (DUV) nonlinear optical (NLO) crystals have important applications in lithography, microfabrication, and high-resolution photoelectric spectrometer. In recent years, significant progress has been made in both the theoretical design and experimental research of DUV NLO crystals. This review aims to offer a comprehensive perspective on exploring a new generation of DUV NLO materials. First, we summarize various computer-aided strategies for crystal structure design and emphasize their significant role in advancing the discovery of DUV NLO materials. Then, we outline several representative DUV crystals of experimental synthesis. Finally, we discuss the future prospects for exploring new generations of DUV NLO materials. We believe that employing data-driven, computer-aided methods to explore DUV NLO materials will help address the current challenges in the field of DUV NLO materials research. The close integration of calculation and experimentation will unlock new opportunities.

Accurate Determination of the Low-Light-Level Absorption of DUV-Fused Silica at 193 nm with Laser Calorimetry

The low-light-level absorption coefficient of OH-contained and H2-impregnated synthetic fused silica material in 193 nm optical lithography application is determined via a laser calorimetry measurement. The fluence and repetition rate dependences of the absorptances of the deep ultraviolet (DUV)-fused silica samples with different thickness are measured. The measured dependences are fitted to a theoretical model, taking into consideration the generation and annealing of laser irradiation induced defects. The surface absorption, the low-light-level linear absorption coefficient, as well as the nonlinear absorption coefficient of the fused silica material are accurately determined via the fitting. The low-light-level linear absorption coefficients determined via the fluence dependence and the repetition rate dependence are in good agreement, demonstrating the reliability of the measured low-light-level absorption coefficient, which is the key parameter to the determination of the internal transmission of the DUV-fused silica material used in the 193 nm optical lithography.

Creating spatial doughnut-spot arrays and double-helix focal fields with prescribed characteristics

Spatially controllable focal fields play a pivotal role in light manipulation and provide significant opportunities for precisely manipulating light–matter interactions in a wide range of applications. In particular, the double-helix focal field—characterized by a distinctive helical structure—exhibits exceptional optical properties, thus differentiating it apart from conventional focal fields. However, the rapid construction of a double-helix focal field with controllable characteristics and a uniform intensity remains a challenging task. Based on the theory of pattern synthesis of an antenna array, we propose and realize the generation of three-dimensional doughnut-spot arrays and double-helix focal fields with specified characteristics in a 4π system by reverse-solving the radiation field of the virtual antenna. Numerical examples indicate that the desired novel focal fields, including features such as shape, orientation, length, and period, could be rapidly, conveniently, and flexibly customized by selecting appropriate parameters for the magnetic dipole array antennas. This method could reveal an avenue for enhanced light manipulation for applications in materials processing, optical lithography, and optical communications.

A2Pb3[H2N(CH2COO)2]3Cl5 (A = K, Rb): Porous Crystals Constructed on [Pb3Cl5O6] Clusters with Comprehensive Nonlinear Optical Performance

AbstractNonlinear optical (NLO) crystals that can extend the frequency range of coherent light have significant applications in laser technology, semiconductor manufacturing, and lithography. Herein, two interesting NLO crystals, A2Pb3[H2N(CH2COO)2]3Cl5 (A = K, Rb), are rationally obtained. Their porous structures are constructed on [Pb3Cl5O6] clusters that possess large hyperpolarizability and polarizability anisotropy, and are arranged in a parallel manner. Remarkably, A2Pb3[H2N(CH2COO)2]3Cl5 (A = K, Rb) exhibits comprehensive NLO performance, including strong phase‐matching second‐harmonic generation (SHG) response, the widest bandgap among lead oxychloride NLO crystals, larger laser damage threshold than 127 MW cm−2, suitable birefringence of 0.11@1064 nm, high thermal stability, non‐deliquescence, as well as facile crystal growth. Theoretical calculations and structural analysis demonstrate that their strong SHG response is predominantly originated from the [Pb3Cl5O6] cluster. This study will provide a unique method for the discovery of new interesting NLO crystals in future.

Spatially Amplified and Rigid Junction in Diblock Copolymers: Reduced Microphase Separation Size via Interface Expansion.

We introduce an approach in diblock copolymer design, where modifying the junction point with rigid bulky monomer expands the cross-sectional area of the interface and leads to a decrease in the repeat period. Using living anionic polymerization, we synthesized a series of dialkynyl midfunctionalized poly(styrene-b-methyl methacrylate) (PSM-DA) and functionalized them using the thiol-alkyne click reaction with specifically selected rigid bulky monomers: PSS-(3-mercapto)propyl-heptaisobutyl substituted (PSS) and 1-adamantanethiol (ADA). This modification, though involving only a single monomer unit within the diblock copolymer structure, brought about a significant reduction in domain size, with PSS and ADA reducing it by 18% and 15%, respectively. The results indicate a method for reducing the domain sizes of block copolymers, which could lead to advancements in lithography and various nanotechnological applications.

Simulation study of decoherence and light intensity uniformization for extreme ultraviolet of uniform light pipe

<sec>Free electron laser (FEL) is a high-quality laser source with wavelengths ranging from short-wave X-ray to long-wave infrared ray. Extreme ultra-violet (EUV) radiation at <i>λ</i> = 13.5 nm emitted by FEL can be used in manufacturing integrated circuit, such as EUV lithography exposure and mask defect inspection. However, the high spatial coherence characteristics and similar Gauss intensity profile distribution of FEL source has a negative effect on imaging, and cannot meet the requirements of imaging applications in EUV lithography. In this work, a newly light pipe for decoherence and intensity uniformity in an EUV spectral range is designed through the simulation calculations. The new light pipe consists of two pairs of tilted elements which are symmetrically distributed in the <i>y</i>-<i>z</i> plane and <i>x</i>-<i>z</i> plane, respectively. In this way, the beam transmission divergence in two dimensions can be widened at the same time, and the disturbance of the ray transmission track and spatial phase distribution is increased, so as to achieve the uniformization of light intensity and the reduction of spatial coherence.</sec><sec>The simulation results show that for an EUV Gaussian beam at <i>λ</i> = 13.5nm, with a diameter of 200 μm, and a divergence of 20 mrad, the newly designed light pipe has more significant decoherence and illumination field uniformity than the conventional light pipe structure. When the new light pipe has an inner diameter of 1mm, a total length of not less than 600 mm, and a tilt angle of 10mrad , a basically uniform illumination field can be obtained, the coherence is completely disordered, and the non-uniformity of light intensity distribution in the illumination field decreases to 0.97 from 28.38 achieved by conventional cylindrical light pipe. At the same time, the light power transmission efficiency is about 37.6% and the maximum transmission efficiency is about 44.58%. The uniformity can be further improved by increasing the number of reflections. When the inner diameter and tilted angle of the light pipe are unchanged, the length of the light pipe increases to 1m, the non-uniformity of intensity distribution at the illumination field further decreases to 0.90, and the light power transmission efficiency is about 22.35%. The results show that the newly designed light pipe structure can meet the application requirements of decoherence and improve the uniformity of illumination field at EUV wavelength range, and it has great application prospects in EUV lithography and other imaging applications.</sec>

Principle of Free-electron Laser and Applications in Medical Research and Lithography

In recent years, as a breakthrough light source technology, free-electron laser (FEL) has the unique advantage of producing coherent radiation with high brightness, high energy, good directivity and excellent monochromaticity. With this in mind, this study will systematical discuss the historical development of FEL technology, from Einstein's laser theory to Dr. Maiman's first commercial laser, as well as the birth and evolution of FEL. To be specific, the basic principles and construction of FEL technology will be discussed in detail, including key components such as electron sources, electron accelerators, and oscillators. The application of free electron laser (FEL) technology in medicine and lithography will also be demonstrated in this paper. According to the analysis, the current limitations of the state-of-art facilities as well as the future development trends and improvements for FEL system will be clarified based on the evaluations. Overall, these results shed light on guiding further exploration of FEL techniques.

Electron Gun Generation and Application in Welding, Lithography and Treatment of Pollutants

Electron Gun Generation and Application in Welding, Lithography and Treatment of Pollutants

Enhanced Thermal Conductivity of Free-Standing Double-Walled Carbon Nanotube Networks.

Nanomaterials are driving advances in technology due to their oftentimes superior properties over bulk materials. In particular, their thermal properties become increasingly important as efficient heat dissipation is required to realize high-performance electronic devices, reduce energy consumption, and prevent thermal damage. One application where nanomaterials can play a crucial role is extreme ultraviolet (EUV) lithography, where pellicles that protect the photomask from particle contamination have to be transparent to EUV light, mechanically strong, and thermally conductive in order to withstand the heat associated with high-power EUV radiation. Free-standing carbon nanotube (CNT) films have emerged as candidates due to their high EUV transparency and ability to withstand heat. However, the thermal transport properties of these films are not well understood beyond bulk emissivity measurements. Here, we measure the thermal conductivity of free-standing CNT films using all-optical Raman thermometry at temperatures between 300 and 700 K. We find thermal conductivities up to 50 W m-1 K-1 for films composed of double-walled CNTs, which rises to 257 W m-1 K-1 when considering the CNT network alone. These values are remarkably high for randomly oriented CNT networks, roughly seven times that of single-walled CNT films. The enhanced thermal conduction is due to the additional wall, which likely gives rise to additional heat-carrying phonon modes and provides a certain resilience to defects. Our results demonstrate that free-standing double-walled CNT films efficiently dissipate heat, enhancing our understanding of these promising films and how they are suited to applications in EUV lithography.

Digital Color Output Conformity to ISO12647-7 Standards (GRACoL 2013 [CGATS21-2-CRPC6]) With the Use of Statistical Process Control (SPC)

The purpose of this applied research was to apply the statistical process control (SPC) to determine the digital color output conformity to ISO12647-7 standards in a color managed digital printing workflow (CMDPW) over a period of 100 days (N=100). The quality of digital color printing is determined by these influential factors: screening method applied, type of printing process, calibration method, device profile, ink (dry toner or liquid toner), printer resolution, and the substrate (paper). For this research, only the color printing attribute overall average color deviation (ACD; ΔE(2000)) was analyzed to examine the CMDPW process consistency in a day-to-day digital printing operation. Printed colors from the random sample size (n=80) were measured against the General Requirement for the Applications in the Commercial Offset Lithography (GRACoL 2013) standards to derive the colorimetric/densitometric values. Reference colorimetric values used in the analysis were the threshold deviations (acceptable color deviations) as outlined in the ISO12647-7 standards (GRACoL 2013). A control chart analysis was applied for further determining the process (CMDPW) ACD variation. The data collected were run through multiple software applications (Microsoft Excel/SPSS/Minitab) to apply various statistical methods. Analyzed data from the experiment revealed that the printed colorimetric values were in match (aligned) with the GRACoL 2013 (reference/target) standards. Since the color values were in control throughout the process, this enabled the CMDPW to produce consistent acceptable color deviation (average printed ΔE(2000)=2.978). (The acceptable threshold color deviation is ΔE(2000)≤3.00.)

EFFECTIVE METHODS OF SYNTHESIS AND OPTIMIZATION OF A HOLOGRAPHIC MASK

The paper presents several statements of the problems of synthesis of holographic mask in the form of optimization problems for quality of holographic images. An effective algorithm for the synthesis of holographic masks based on FFT with complexity O(NlnN), where N is the number of elements of the depicted object, is described. Based on this algorithm, a scalable software package has been developed and implemented that allows synthesizing holographic masks for various lithography applications, including the production of MEMS, MOEMS and high-end chips. Experimental results are presented.

Ultrathin, Flexible, and Reusable Silicon Shadow Masks Manipulated via Transfer Printing

Stencil lithography is a facile patterning technique that offers a potential solution to the limitations of conventional photolithography. However, several critical factors such as enhanced pattern resolution, ability to pattern on nonplanar surfaces, and multilayer patterning should further be addressed to extend the applications of stencil lithography. This study presents a novel ultrathin silicon shadow mask which is flexible, reusable, and able to be precisely aligned and manipulated through transfer printing. The small thickness of the silicon shadow mask inherently provides it with the enhanced resolution patterning on both planar and nonplanar surfaces. To highlight these attractive benefits, substrates are patterned with metal deposition as well as by etching in a multilayer configuration. Moreover, it is found that the pattern resolution which is degraded as the shadow mask is repeatedly coated with metal and becomes warped can be restored after the mask cleaning procedure, demonstrating its effective reusability. Finally, as a device‐level application, top contact/bottom gate organic thin film transistor arrays are fabricated on both planar and curved surfaces using the shadow mask. These results show the promise of stencil lithography as a versatile and reliable high resolution patterning method for various applications by exploiting the presented ultrathin silicon shadow mask.

Correcting Hohlraum Drive Asymmetry with Glow Discharge Polymerization Coated Capsule Shims

In inertial confinement fusion target design, the shape discrepancy between the cylindrical hohlraum and the spherical capsule creates a low mode asymmetry in the implosion. One way to correct such asymmetry is to shim the target capsule surface with extra mass in specific locations following a three-dimensional P4 Legendre mode. Previously, the desired surface pattern was precision machined out of the capsule. The resulting 2DConA experiments that investigated the implosion’s shape demonstrated the shimming method’s success. However, machining leaves large defects on the capsule surface that will degrade neutron yield in a DT implosion. An alternative shimming approach is to grow the pattern on the capsule surface using a glow discharge polymerization coating process in a stencil lithography application. In this paper, we discuss the fabrication, characterization, and challenges of making shimmed target capsules with this new method.