Lithography Tool Research Articles

E-beam Lithography Technology for Quantum Device Fabrication and Nanoscale Patterning

Currently nanotechnology becoming more important with the implementation of nano devices including quantum devices. In this paper, we will briefly introduce the JEOL JBX-8100FS e-beam lithography tool which was recently installed in Hallym University and the current status of the exposure conditions set up. As applications using e-beam lithography tool, we will introduce Schottky barrier single hole transistor and silicon nanowire thermoelectric device, respectively. We are under researching plasmonic and quantum devices as basic research.

Aperiodic multilayer masks for M3D mitigation in high- and hyper-NA extreme ultraviolet lithography

As extreme ultraviolet lithography tools with higher image numerical apertures (NAi) are introduced, the range of angles at the multilayer mask stack is also increased. Lithography systems are designed to fulfill the “abbe sine rule,” where NAm is related to NAi by the reduction factor. As a result, increases in NAi will increase NAm. High-NA and hyper-NA systems will be implemented with anamorphic optics, 4× in “X,” and 8× in “Y” to reduce the necessary angles. Even so, hyper-NA masks may see illumination angles as high as 13.4°, up from 10.8° for 0.33 NA. This represents a challenge for maintaining through-angle mask reflection using the current periodic mask multilayer structures. In addition to the reflectance amplitude, the phase of reflected light, which plays an important role in imaging, is also strongly influenced by increasing angles. The propagation of light through each bilayer in the stack imparts a phase shift based on the incidence angle. This is then accumulated over many layers, inducing phase effects, which are unique to each illumination point. This will become especially true for high-NA and hyper-NA mask applications. While adjustments to the multilayer period are sufficient to achieve acceptable reflectance, periodic multilayers may suffer in normalized image log slope (NILS) and image placement error (IPE) metrics as a result of strong oblique multilayer M3D phase effects. In this work, we present a first principles methodology for the systematic reduction of oblique multilayer M3D effects through the use of aperiodic multilayer design. We find that when used for low-k1, hyper-NA patterning NILS is improved by 40+%, while IPE through pitch is similarly improved. Under high-NA conditions, a 5%–25% NILS gain is found alongside the enhanced depth of focus.

Conformal Antireflective Multilayers for High‐Numerical‐Aperture Deep‐Ultraviolet Lenses

AbstractPrecise surface reflectance control at specific deep‐ultraviolet (DUV) wavelengths across wide angles is crucial for semiconductor inspection and lithography tools. The inherent challenges in designing DUV antireflective multilayers stem from limited transparent materials and the resultant fabrication complexity owing to numerous interfaces. Here, wide‐angle antireflective multilayers finely tuned to 248 nm designed using an active learning scheme is presented. The active learning scheme employing factorization machines (FM) identifies the optimal configurations for binary‐material‐based multilayers (AlF3/LaF3, AlF3/MgF2, and AlF3/Al2O3) with varying index contrasts, achieving minimal figure‐of‐merit (i.e., average angular reflectance) values at predetermined total thicknesses. High‐index‐contrast AlF3/Al2O3 multilayers are fabricated via atomic layer deposition, thus enabling the conformal coating of high‐numerical‐aperture (NA) lenses with atomic precision. An optimized AlF3/Al2O3 tri‐layer with a total thickness of 180 nm results in an average (0°–45°) reflectance of 0.4% on a CaF2 planar substrate and 0.6% on a CaF2 convex lens (NA = 0.47), similar to the performance of an ideal single‐layer coating requiring a practically unavailable refractive index. Phasor analysis, which considers only first‐order reflections between adjacent layers, supports the benefits of high‐index‐contrast binary materials and the use of the FM‐based active learning scheme in antireflective multilayer design.

Thermal scanning probe and laser lithography for patterning nanowire based quantum devices

Semiconductor nanowire (NW) quantum devices offer a promising path for the pursuit and investigation of topologically-protected quantum states, and superconducting and spin-based qubits that can be controlled using electric fields. Theoretical investigations into the impact of disorder on the attainment of dependable topological states in semiconducting nanowires with large spin–orbit coupling and g-factor highlight the critical need for improvements in both growth processes and nanofabrication techniques. In this work, we used a hybrid lithography tool for both the high-resolution thermal scanning probe lithography and high-throughput direct laser writing of quantum devices based on thin InSb nanowires with contact spacing of 200 nm. Electrical characterization demonstrates quasi-ballistic transport. The methodology outlined in this study has the potential to reduce the impact of disorder caused by fabrication processes in quantum devices based on 1D semiconductors.

Two-frame wavefront reconstruction method with nonlinear optimization for Ronchi lateral shearing interferometry

Ronchi lateral shearing interferometry is widely applied in wavefront measurement of advanced lithography tools. In Ronchi lateral shearing interferometry, higher-order diffraction beam interference is a common challenge, currently mitigated by introducing more phase shifts, resulting in extended measurement times and added errors. In this study, we propose a nonlinear optimization approach that combines a 2-frame phase-shifting algorithm to suppress the influence of high diffraction orders, reducing the required number of phase shifts by more than 75%. We formulate a numerical model that aligns with the interferometry, construct a highly robust error function, and enable high-precision wavefront reconstruction by optimizing Zernike coefficients. The accuracy and robustness of the proposed method are verified through simulations and experiments.

Design concept evaluation based on cloud rough model and modified AHP-VIKOR: An application to lithography tool manufacturing process

Design concept evaluation is a wide domain of research as the production process of new product development is mainly based on the evaluations of experts. As different types of uncertainties like vagueness, randomness, and diversity essentially exist in the evaluation information, the manipulation models that deal with just one type of uncertainty are not appropriate for ranking the design alternatives. The integration of multiple approaches into a single mathematical model to create an effective framework is more useful for uncertain information manipulation. This paper presents an innovative group decision-making approach to evaluate design concepts by integrating cloud rough numbers, analytic hierarchy process (AHP) and VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method to introduce a novel cloud rough AHP-VIKOR model. The concept of cloud rough numbers is utilized by fusing the merits of the cloud model theory and rough approximations in addressing randomness in experts’ judgments and intrapersonal uncertainty for handling consensus inconsistency. Some new modified algebraic operations are introduced to remove the errors in already existing operations of cloud rough numbers. The cloud rough AHP technique is introduced to compute weights of design criteria by computing the cloud rough numbers of linguistic values and their reciprocals. Based on cloud rough values of positive and negative ideals, the individual regret, group utility values and evaluation indices are determined. Using the distance of evaluation indices from minimized cloud rough value, the design alternatives are ranked using different formulae. The significance of the proposed approach is illustrated with a real-world application in lithography tool manufacturing process. The out-performance and reliability of the proposed model is studied by a sensitivity analysis of different parameters in the method, and a comparison analysis with existing approaches.

All-Glass 100 mm Diameter Visible Metalens for Imaging the Cosmos.

Metasurfaces, optics made from subwavelength-scale nanostructures, have been limited to millimeter-sizes by the scaling challenge of producing vast numbers of precisely engineered elements over a large area. In this study, we demonstrate an all-glass 100 mm diameter metasurface lens (metalens) comprising 18.7 billion nanostructures that operates in the visible spectrum with a fast f-number (f/1.5, NA = 0.32) using deep-ultraviolet (DUV) projection lithography. Our work overcomes the exposure area constraints of lithography tools and demonstrates that large metasurfaces are commercially feasible. Additionally, we investigate the impact of various fabrication errors on the imaging quality of the metalens, several of which are specific to such large area metasurfaces. We demonstrate direct astronomical imaging of the Sun, the Moon, and emission nebulae at visible wavelengths and validate the robustness of such metasurfaces under extreme environmental thermal swings for space applications.

Self-Aligning Nanojunctions for Integrated Single-Molecule Circuits.

Robust, high-yield integration of nanoscale components such as graphene nanoribbons, nanoparticles, or single-molecules with conventional electronic circuits has proven to be challenging. This difficulty arises because the contacts to these nanoscale devices must be precisely fabricated with angstrom-level resolution to make reliable connections, and at manufacturing scales this cannot be achieved with even the highest-resolution lithographic tools. Here we introduce an approach that circumvents this issue by precisely creating nanometer-scale gaps between metallic carbon electrodes by using a self-aligning, solution-phase process, which allows facile integration with conventional electronic systems with yields approaching 50%. The electrode separation is controlled by covalently binding metallic single-walled carbon nanotube (mCNT) electrodes to individual DNA duplexes to create mCNT-DNA-mCNT nanojunctions, where the gap is precisely matched to the DNA length. These junctions are then integrated with top-down lithographic techniques to create single-molecule circuits that have electronic properties dominated by the DNA in the junction, have reproducible conductance values with low dispersion, and are stable and robust enough to be utilized as active, high-specificity electronic biosensors for dynamic single-molecule detection of specific oligonucleotides, such as those related to the SARS-CoV-2 genome. This scalable approach for high-yield integration of nanometer-scale devices will enable opportunities for manufacturing of hybrid electronic systems for a wide range of applications.

Displacement

The concept of displacement and its consequences are permanently present in my practice, either in the narratives explored in light of the personal stories that have a wider psychological impact, or in the archaeological approach to tame raw, organic materials through the reconstitution of technological, 19th-century procedures considered obsolete and commercial. The approach to paper based on multiple experiments led to reconstructing feasible alternatives to the traditional techniques of obtaining images, including photographic and non-photographic processes. Revision of gillotage, reconstruction of lithographic drawing, painting and printing tools and working in situ directed the research into more immediate work with raw materials like resins, plasters, organic glues, and pigments. Preliminary tests of image development with dichromate dusting methods established satisfactory surfaces for traditional photo-enamel. In my PhD proposal, displacement meets with the obsolete techniques and the fusion of printmaking, photography, and glass as a haptic medium that corresponds to my heuristic approach.

Nanoimprint lithography guiding templates for advanced magnetic media fabrication

Nanoimprint lithography presents unique opportunities for advanced magnetic storage media with ordered bit arrangements such as bit patterned media or heated dot magnetic recording. Providing sub-10 nm resolution and full disk imprinting capability, UV-nanoimprint lithography based on rigid quartz templates bears the entitlement for patterned recording media manufacturing with high throughput at low cost. However, a key challenge is the fabrication of the high-resolution template that can transfer the desired pattern onto the disk with high fidelity and low line edge roughness. In this article, we present fabrication routes and overcome challenges to the fabrication of quartz templates suitable for self-alignment and guiding purposes to be used for template replication toward full disk imprints. Guiding patterns down to 40 nm pitch are prepared using a rotary electron beam lithography tool. We compare three different process approaches to fabricate an etching mask for patterning the quartz. Two methods target chromium patterning, one with traditional lift-off and another by dry etching, both using an e-beam resist mask. The third approach is based on the development of a carbon-based Tri-layer hard mask. The template pattern profile is optimized for imprint-suitable sidewall angles using dry etching in a CF4/O2 chemistry. The templates were characterized using scanning electron microscopy and atomic force microscopy to evaluate the quality of the transferred pattern as well as line edge roughness. Our results show that the Tri-layer process using carbon resulted in the lowest line edge roughness of ≈0.65 nm at the imprinted disk level. In addition, we show that Tri-layer masking allowed for the use of conventional ZEP e-beam resist and fast writing speeds, while gaining high selectivity during quartz patterning.

X-ray-based overlay metrology using reciprocal space slicing analysis

Overlay serves as the pivotal performance indicator for lithography tools, and its prompt and precise measurement significantly underpins the process yield control. At present, diffraction-based overlay metrology employing optical wavelengths encounters constraints in terms of measurement sensitivity. When transitioning to x-ray wavelengths, the critical-dimension small-angle x-ray scattering (CDSAXS) method for nanostructure characterization necessitates reciprocal space mapping (RSM) and inverse problem solving, resulting in substantial throughput constraints. In this work, we propose an x-ray-based overlay metrology using reciprocal space slicing analysis (RSS), yielding high-precision overlay measurement at one single angle of incidence (AOI). Moreover, we examine the robustness of the proposed method against errors stemming from overlay target grating fabrication and measurement processes, substantiating its efficacy as a novel x-ray-based overlay metrology and unveiling the potential application of x-ray-based techniques within the realm of integrated circuit metrology.

Generating smooth potential landscapes with thermal scanning-probe lithography

Scanning probe microscopy (SPM) uses a sharp tip to interrogate surfaces with atomic precision. Inputs such as mechanical, electrical, or thermal energy can activate highly localized interactions, providing a powerful class of instruments for manipulating materials on small length scales. Thermal scanning-probe lithography (tSPL) is an advanced SPM variant that uses a silicon tip on a heated cantilever to locally sublimate polymer resist, acting as a high-resolution lithography tool and a scanning probe microscope simultaneously. The main advantage of tSPL is the ability to electrically control the temperature and applied force of the tip, which can produce smooth topographical surfaces that are unattainable with conventional nanofabrication techniques. Recent investigations have exploited these surfaces to generate potential landscapes for enhanced control of photons, electrons, excitons, and nanoparticles, demonstrating a broad range of experimental possibilities. This paper outlines the principles, procedures, and limitations of tSPL for generating smooth potentials and discusses the prospective impact in photonics, electronics, and nanomaterials science.

Recent advances in block copolymer self‐assembly: From the lowest to the highest

AbstractA perspective is presented on recent developments in block copolymers (BCPs), capable of forming sub‐10 nm nanostructures and bottlebrush block copolymers (BBCPs), capable of forming supra‐100 nm nanostructures. Over the last few decades, BCP research has emphasized pattern miniaturization for application in next‐generation lithography tools in the semiconductor industry. The first part focuses on the recent efforts that investigated high‐χ linear BCPs evolved from conventional poly(styrene‐b‐methyl methacrylate) (PS‐b‐PMMA) pairs. Recently, novel BCP structures capable of forming nanostructures with significant periodicities for controlling visible light have gained considerable attention. The second part reviews the literature on BBCPs that exhibit the potential to create supra‐100 nm nanostructures. Finally, the future aspect on BCP lithography is discussed.

(Gordon E. Moore Medal for Outstanding Achievement in SSS&T) Moore’s Law Sustained by Non-Lithographic Technologies

Since G. Moore’s historical observation [1] that the functionality per chip (bits, transistors) as well as MPU performance (clock frequency in MHz × instructions per clock = millions of instructions per second) doubles every 1.5 to 2 years, the semiconductor industry has continued to grow to over 600 G$ in 2022 [2].The IRDS 2022 Roadmap [3] catches the scaling challenges faced for the upcoming decades by the term ‘3D Power Scaling’. This period is the third in a sequence of eras that started early on with straightforward geometrical scaling by continuous shortening of the wavelengths (from regular UV to deep UV/immersion) used in the lithographic patterning of planar transistor structures (Fig. 1a). In the second, almost past ‘equivalent scaling’ era, new superior material properties and critical dimensions nearing single-digit nanometer values could still be realized by cost-effective technology solutions, often in spite of the delay in (EUV) lithography solutions. Ever more complex device architectures requiring extreme edge placement accuracy, layer conformality and shape fidelity in all processing steps (deposition, etching) could be fully 3D-integrated into vertical intra- and inter-chip concepts (Fig. 1b) thus alleviating the need for new capital-intensive lithography tools capable of higher resolution (~ 40% of total tool costs).Figure 2 illustrates the development in the past 65 years of the non-lithographic technologies that have sustained Moore’s Law, as driven by continuous downscaling of CMOS devices. Two extra trends have set in half way (~1993): single-wafer processing and heterogeneous device integration. The latter development, often coined as More than Moore, a term that was introduced in the 2005 ITRS Roadmap, and refers to the silicon-compatible integration of devices with functionalities that do not necessarily scale according to Moore's Law, but provide additional value in different ways. The More-than-Moore approach allows for the incorporation of non-digital functionalities (e.g., RF communication, passive components, power control, sensors, actuators) that can flexibly move from the system board-level into the package (SiP) or onto the chip (SoC).We will discuss a kaleidoscopic view of the author’s activities in Rapid Thermal Processing, RIE etching for TSVs, RF-SIP integration of passives, and Atomic Layer Processing (deposition, etch, and cleaning). In sub-10 nm scaling and fabrication of 3D architectures, especially the techniques of ALD and ALE have manifested to cost-effectively bridge the record incubation time needed to bring EUV technology from prototype to commercial use. More importantly, these unique techniques can be used to create advanced devices in dedicated isotropic (thermal and radical-enhanced) and anisotropic (directional and ion-enhanced) processing modes. Here, energetic species (radicals and/or ions in a plasma) are used in one or two steps, with the ions yielding anisotropic profiles (used in FinFET logic and 3D NAND memory), and neutrals and radicals yielding isotropic profiles used to deposit or etch the features in horizontal nanowires, nanosheets and ‘forksheets’ in GAA-FETs.1. G. Moore, Cramming more components onto integrated circuits, Electronics 38(8), (1965) 114-118.2. https://www.semiconductors.org/global-semiconductor-sales-increase-24-year-to-year-in-october-annual-sales-projected-to-increase-26-in-2021-exceed-600-billion-in-2022/3. International Roadmap for Devices and Systems (IRDS™) 2022 Edition - IEEE IRDS™. Fig. 1. a) Different scaling ages for device manufacturing; b) the planar-to-GAA transition; after [3]. Fig. 2. Historic and future perspectives of non-lithographic key technologies in IC scaling. Figure 1

Enhancing projection based iterative learning control: A set-membership approach

Lithographic machine tools require both high motion accuracy and high motion flexibility. Projection based iterative learning control (P-ILC) is appealing for wafer stages to achieve two goals, simultaneously. P-ILC contains a nonparametric feedforward controller based on ILC, and a parametric feedforward controller with a projection step for feedforward tuning. In this paper, a set-membership based frequency-domain ILC algorithm (SM-F-ILC) is employed in the enhancing P-ILC scheme to improve the performance in the nonparametric feedforward control mode. SM-F-ILC can effectively compensate for repetitive errors, attenuate the nonrepetitive error accumulation and achieve fast convergence speed with model uncertainties. These superiorities also facilitate to improve the performance of P-ILC in the parametric feedforward control mode. The validity of the enhancing P-ILC scheme is demonstrated by experimental results.

Wavefront measurements using the Ronchi test for high-NA lithography projection lenses.

The Ronchi test is widely used for wavefront measurements in advanced lithography tools, and a physical optics explanation of the Ronchi test based on scalar diffraction theory can be found in numerous publications. However, for high-numerical aperture (high-NA) lithography projection lenses, the vector nature of light should be considered when performing wavefront measurements, especially the effect of polarization aberrations on the wavefront test results. In this paper, a vector model for describing shearing interferometry for high-NA lithography projection lenses is established. In addition to considering the vector nature of light, the vector model also calculates the Ronchigram on the screen of a detector at any distance from a diffraction grating, as opposed to the distance restriction for the Fraunhofer diffraction approximation used by the existing methods. Using the developed mathematical model of the Ronchi test, the Ronchigrams of high-NA lithography projection lenses under non-polarized illumination are simulated, and the effect of the distance between the diffraction grating and the detection screen on the wavefront measurement accuracy are discussed.

Influence of the vibration of extreme ultraviolet lithographic tool stages on imaging.

Vibrations of the reticle and wafer stage are inevitable due to the high speed and acceleration required during the exposure movement of the lithography system. Previous studies have shown that these vibrations have an impact on both overlay and imaging quality. Furthermore, as the integrated circuit industry continues to develop and extreme ultraviolet (EUV) lithography is increasingly utilized, the size of the exposure image continues to decrease, making the stability of the reticle and wafer stage motion increasingly important. This paper establishes a model of the reticle and wafer stage motion under the influence of vibration based on the advanced process node of EUV lithography. We investigate the relationship between variations in vibration amplitude and frequency and their effects on imaging contrast and line edge roughness (LER). Additionally, we simulate the quantitative relationship between the vibration of the reticle and wafer stage and the imaging quality of through-pitch line/space structures, tip-to-tip (T2T) structures, and tip-to-line (T2L) structures under extreme exposure conditions of EUV lithography using a computer.

Rigorous simulation model of double-Ronchi shearing interferometry on lithographic tools.

Double-Ronchi shearing interferometry is widely used in wavefront aberration measurements for advanced lithography projection lens systems. A rigorous simulation model of double-Ronchi shearing interferometry on lithographic tools is the precondition for phase-shifting retrieval algorithm design and error analysis. This paper presents a rigorous simulation model of double-Ronchi shearing interferometry considering the vector nature of light. The model is accurate and can be used in the study of double-Ronchi shearing interferometry.

Development of deep ultraviolet optical maskless exposure tool for advanced lithography

Digital scanner (DS), a deep ultraviolet optical maskless exposure tool is being developed. DS uses a micromirror-type spatial light modulator to create the “mask” pattern combined with a solid-state laser with a wavelength of 193 or 248 nm. The exposure concept of DS and advantage of solid-state laser as an exposure light source is described. DS proof-of-concept tool with resolution of half-pitch 80 nm L/S was developed. The exposure results of maskless unique application, such as large area printing and chip ID printing for security purposes, are shown.

Classification of dissolution modes of partially protected poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solutions

The development of high-numerical aperture exposure tools for EUV lithography is in progress. The development process (the dissolution of resist films) is the key to fine patterning. The dissolution dynamics of acidic polymers (the backbone polymers of chemically amplified resists) depend on various parameters related to molecular structures. In this study, the dissolution dynamics in tetraalkylammonium hydroxide (TAAH) aqueous solutions were classified into six classes on the basis of the frequency and impedance changes observed during the development process by a quartz crystal microbalance method. The relationship between class and physical parameters of materials was analyzed by decision tree and support vector machine methods. The feature values used were the alkyl chain length, molecular weight, and concentration of TAAH; the viscosity of the developer; and the protection ratio, molecular weight, contact angle, surface free energies of polymers, and film thickness. The classification accuracy was 0.80 for the validation data.