Electron Beam Lithography Research Articles

A Fabrication Method for Realizing Vertically Aligned Silicon Nanowires Featuring Precise Dimension Control

Silicon nanowires (SiNWs) have garnered considerable attention in the last few decades owing to their versatile applications. One extremely desirable aspect of fabricating SiNWs is controlling their dimensions and alignment. In addition, strict control of surface roughness or diameter modulation is another key parameter for enhanced performance in applications such as photovoltaics, thermoelectric devices, etc. This study investigates a method of fabricating silicon nanowires using electron beam lithography (EBL) and the deep reactive ion etching (DRIE) Bosch process to achieve precisely controlled fabrication. The fabricated nanowires had a pitch error within 2% of the pitch of the direct writing mask. The maximum error in the average diameter was close to 25%. The simplified two-step method with tight control of the dimensions and surface tunability presents a reliable technique to fabricate vertically aligned SiNWs for some targeted applications.

Mitigating interface damping of metal adhesion layers of nanostructures through bright-dark plasmonic mode coupling

Metal (such as Cr, Ti, etc.) adhesion layers, which are generally used to prevent nanostructures from falling off during electron beam lithography processes, will introduce interface damping, decrease the near-field enhancement, and shorten the dephasing time of localized surface plasmons (LSP). Maintaining metal adhesion layers while alleviating the induced interface damping in nanostructures is crucial for high-performance sensing, surface-enhanced Raman scattering elements, plasmon-based photocathodes, and plasmon-mediated catalysis. Here, we experimentally demonstrated that the mitigation of interface damping of metal adhesion layers can be achieved through the coupling between the bright and dark plasmonic modes of gold nanorods. We attribute the mitigation to stronger confinement across the plasmon energy, which effectively reduces the proportion of plasmon energy injected into the Cr adhesive layers. Compared to weak coupling, the non-radiative damping of plasmonic modes 1 and 2 is reduced by approximately 74% and 85%, respectively, under strong coupling conditions. The experimental results are supported by finite-difference time-domain simulations and are well explained by the calculated interaction potential for different gap sizes. This research will further benefit applications where low interface damping is required, such as the construction of low-threshold nanolasers and ultrasensitive sensing systems.

Quantitative evaluation of residual resist in electron beam lithography based on scanning electron microscopy imaging and thresholding segmentation algorithm

Electron beam lithography is a critical technology for achieving high-precision nanoscale patterning. The presence of resist residues in the structures can significantly affect subsequent processes such as etching and lift-off. However, the evaluation and optimization of resist residues currently relies on qualitative observations like scanning electron microscopy (SEM), necessitating multiple experiments to iteratively optimize exposure parameters, which is not only labor-intensive but also costly. Here, we propose a quantitative method to evaluate resist residues. By processing the obtained SEM images using a threshold segmentation algorithm, we segmented the resist structure region and the residual resist region in the images. The grayscale values of these two regions are identified, and the residues are quantified based on the ratio of these values. Furthermore, a relationship curve between the residue amount and the exposure dose is plotted to predict the optimal exposure dose. To validate this method, we fabricated hydrogen silsesquioxane annular grating structures with 30 nm linewidth and analyzed the residue levels over an exposure dose range of 2000-2500μC cm-2, predicting the optimal dose to be 1800μC cm-2and confirming this through experiments. Additionally, we applied the method to polymethyl methacrylate and ZEP-520A structures, achieving similarly accurate results, further confirming the method's general applicability. This method has the potential to reduce experimental costs and improve yield and production efficiency in nano fabrication.

Research on Chip Manufacturing and Fault Detection Technology

In the wave of the digital era, the chip plays a key role in promoting the whole information technology revolution with its core position in the development of world science and technology. As the cornerstone of computing and data processing, the development of chips has promoted the progress of the entire technology field. The chip’s manufacturing is the key to determining the performance and computing power of the whole chip, and fault detection technology in the production process is an important part of determining the product’s quality and cost. Therefore, under the background of Moore’s law approaching the physical limit, how to ensure the yield of chip production while continuing to improve chip performance has become a major challenge for the chip manufacturing industry. Based on this, this paper summarizes the key manufacturing steps of the chip. The chip manufacturing technology is comprehensively sorted from design to silicon wafer manufacturing, photolithography, etching, ion implantation, and other processes. At the same time, the research direction of monocrystalline silicon manufacturing technology and the existing lithography technology are introduced, including optical lithography, extreme ultraviolet lithography, electron beam lithography, and so on. Fault detection technology in chip production has also been introduced. In addition, the chip manufacturing and fault detection technology introduced in this paper is summarized and its future development is prospected, which provides reference and inspiration for promoting the continuous progress of chip technology.

Application of Graphene in Acoustoelectronics

An interdigital transducer structure was fabricated from multilayer graphene on the surface of the YZ-cut of a LiNbO3 ferroelectric crystal. The multilayer graphene was prepared by CVD method and transferred onto the surface of the LiNbO3 substrate. The properties of the multilayer graphene film were studied by Raman spectroscopy. A multilayer graphene (MLG) interdigital transducer (IDT) structure for surface acoustic wave (SAW) excitation with a wavelength of Λ=60 μm was fabricated on the surface of the LiNbO3 crystal using electron beam lithography (EBL) and plasma chemical etching. The amplitude–frequency response of the SAW delay time line was measured. The process of SAW excitation by graphene IDT was visualized by scanning electron microscopy. It was demonstrated that the increase in the SAW velocity using graphene was related to the minimization of the IDT mass.

Xenon plasma-focused ion beam milling for fabrication of high-purity, bright single-photon sources operating in the C-band

Electron beam lithography is a standard method for fabricating photonic micro and nanostructures around semiconductor quantum dots (QDs), which are crucial for efficient single and indistinguishable photon sources in quantum information processing. However, this technique is difficult for direct 3D control of the structure shape, complicating the design and enlarging the 2D footprint to suppress in-plane photon leakage while directing photons into the collecting lens aperture. Here, we present an alternative approach to employ xenon plasma-focused ion beam (Xe-PFIB) technology as a reliable method for the 3D shaping of photonic structures containing low-density self-assembled InAs/InP quantum dots emitting in the C-band range of the 3rd telecommunication window. The method is optimized to minimize the possible ion-beam-induced material degradation, which allows exploration of both non-deterministic and deterministic fabrication approaches, resulting in photonic structures naturally shaped as truncated cones. As a demonstration, we fabricate mesas using a heterogeneously integrated structure with a QD membrane atop an aluminum mirror and silicon substrate. Finite-difference time-domain simulations show that the angled sidewalls significantly increase the emission collection efficiency to approx. 0.9 for NA = 0.65. We demonstrate experimentally a high purity of pulsed single-photon emission (∼99%) and a superior extraction efficiency value reported in the C-band of η = 24 ± 4%.

High-efficiency and easy-processing thin-film lithium niobate edge coupler

Fiber-to-chip coupling with ultralow loss and broadband operation wavelength range is essential in the practical applications of thin-film lithium niobate (TFLN) integrated photonic devices. However, the existing edge couplers often require electron beam lithography overlaying and multiple etching processes, which are expensive and complex. In this Letter, we demonstrate an edge coupler that includes only a vertically tapered TFLN waveguide and silicon dioxide cladding. The coupling efficiency between a lensed fiber and an on-chip LN waveguide is down to 1.43 dB/facet, while the 3-dB bandwidth exceeds the range from 1510 to 1630 nm. These edge couplers also show reliable fiber misalignment tolerance. Furthermore, the fabrication complexity is greatly reduced since only a single etching step for the TFLN waveguide is needed. The minimum waveguide width of 1.3 μm guarantees compatibility with i-line photolithography, providing a potential for massive production of TFLN devices.

Resistive Switching Characteristics of NiO Thin Films Influenced by Changes in the Diameter of Nanometer-Scale Top Electrodes.

We investigated the forming, set, and reset voltages affected by the area of the top electrodes of a resistive random access memory (RRAM) capacitor fabricated by epitaxial NiO thin films. NiO RRAM capacitors with Au top electrode with a diameter of 100 μm showed typical unipolar switching characteristics. Au top electrodes with diameters of 10, 20, and 30 nm were formed on the surface of epitaxial NiO thin films by e-beam lithography. The forming, set, and reset voltages tended to decrease as the diameter of NiO RRAM capacitors with nanosized Au top electrodes decreased. As the area of the Au top electrodes increases, the volume of space in which the conductive filaments formed within the NiO RRAM capacitors can be formed becomes larger. This causes the conductive filament to be formed at relatively low energy, giving low forming voltages, while increasing the diversity of paths, causing a wide forming voltage distribution.

Synthesis and electrical transport properties of superconducting platinum silicide thin films and devices

We evaluate the material characteristics of superconducting platinum silicide (PtSi) thin films as candidate materials for superconducting quantum information devices compatible with silicon technology. These films were synthesized using magnetron sputtering under ultrahigh vacuum conditions, followed by rapid thermal annealing. Polycrystalline PtSi films synthesized by this method have the favorable properties of superconducting critical temperature of 0.95 K and relatively long zero-temperature Ginzburg-Landau coherence length of 76 nm. We further studied coplanar microbridge devices fabricated by electron beam lithography and chlorine-free reactive ion etching, finding that the temperature-dependent critical current density follows the Ginzburg Landau depairing mechanism.

Reliable fabrication of 3D freestanding nanostructures via all dry stacking of incompatible photoresist

Three-dimensional (3D) free-standing nanostructures based on electron-beam lithography (EBL) have potential applications in many fields with extremely high patterning resolution and design flexibility with direct writing. In numerous EBL processes designed for the creation of 3D structures, the multilayer resist system is pivotal due to its adaptability in design. Nevertheless, the compatibility of solvents between different layers of resists often restricts the variety of feasible multilayer combinations. This paper introduces an innovative approach to address the bottleneck issue by presenting a novel concept of multilayer resist dry stacking, which is facilitated by a near-zero adhesion strategy. The poly(methyl methacrylate) (PMMA) film is stacked onto the hydrogen silsesquioxane (HSQ) resist using a dry peel and release technique, effectively circumventing the issue of HSQ solubilization by PMMA solvents typically encountered during conventional spin-coating procedures. Simultaneously, a dry lift-off technique can be implemented by eschewing the use of organic solvents during the wet process. This pioneering method enables the fabrication of high-resolution 3D free-standing plasmonic nanostructures and intricate 3D free-standing nanostructures. Finally, this study presents a compelling proof of concept, showcasing the integration of 3D free-standing nanostructures, fabricated via the described technique, into the realm of Fabry-Perot cavity resonators, thereby highlighting their potential for practical applications. This approach is a promising candidate for arbitrary 3D free-standing nanostructure fabrication, which has potential applications in nanoplasmonics, nanoelectronics, and nanophotonics.

Constant period line gratings as a metric for patterning fidelity in electron beam lithography

As smaller critical dimensions of devices fabricated via electron-beam lithography (EBL) are achieved over large areas, the need for new metrology techniques follows. Large (cm × cm) substrates have traditionally been both time and labor intensive to measure using traditional techniques such as scanning electron microscopy (SEM) or atomic force microscopy. When optimizing an EBL process over large areas, stitch error must be eliminated to maximize feature placement fidelity. Simultaneously, traditional EBL requirements, such as low line-edge roughness, proximity effect correction, and appropriate write times, must be maintained. With this plethora of requirements, we propose a technique to characterize placement errors over large areas using interferometric measurements. This method, when combined with traditional techniques like SEM and optical microscopy, assesses the full domain of potential errors over large areas in a time- and cost-efficient manner. As a proof of concept, a set of five small format (5 × 10 mm2) gratings with an 855 nm period were written twice, each set produced under two different tool error conditions. We report on the efficacy of interferometric metrology to accurately assess feature placement errors and report measured groove displacement across all ten gratings.

Fabrication of thick Cr masks for reactive ion substrate etching by electron beam lithography and lift-off techniques

Fabrication of tall Cr nanostructures of different shapes by lithography and lift-off processes is demonstrated. By varying resist thickness, metal layer thickness, and diameter of holes in the resist mask, it is demonstrated that metal structures with shapes ranging from sharp-tipped conical over flat-top cones to nearly cylindrical can be fabricated. A comparison of resist layer dissolution in acetone, covered by Ag and Cr films, reveals that Cr films grow with an open structure of particles that allow rapid solvent diffusion through Cr layers that are several hundred nanometers thick. On the other hand, the 2D growth of Ag on the resist forms a barrier against acetone diffusion. The open structure of Cr enables the lift-off process to fabricate several-μm-high nanostructures using a single resist layer. As an example, high-aspect-ratio Si structures are demonstrated by reactive ion etching using thick Cr layers as a mask, fabricating nanopillars with 3 μm height at room temperature.

Fourier Surfaces Reaching Full-Color Diffraction Limits.

Optical Fourier surfaces (OFSs), characterized by sinusoidally profiled diffractive optical elements, can outperform traditional binary-type counterparts by minimizing optical noise through selectively driving diffraction at desired frequencies. While scanning probe lithography (SPL), gray-scale electron beam lithography (EBL), and holographic inscriptions are effective for fabricating OFSs, achieving full-color diffractions at fundamental efficiency limits is challenging. Here, an integrated manufacturing process is presented, validated theoretically and experimentally, for fully transparent OFSs reaching the fundamental limit of diffraction efficiency. Leveraging holographic inscriptions and soft nanoimprinting, this approach effectively addresses challenges in conventional OFS manufacturing, enabling scalable production of noise-free and maximally efficient OFSs with record-high throughput (1010-1012 µm2h-1), surpassing SPL and EBL by 1010 times. Toward this end, a wafer-scale OFSs array is demonstrated consisting of full-color diffractive gratings, color graphics, and microlenses by the one-step nanoimprinting, which is readily compatible with rapid prototyping of OFSs even on curved panels, demanding for transformative optical devices such as augmented and virtual reality displays.

Efficient Calculation of Charging Effects in Electron Beam Lithography Using the SA-AMG

Efficient Calculation of Charging Effects in Electron Beam Lithography Using the SA-AMG

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.

Thermally tunable microring resonators based on germanium-on-insulator for mid-infrared spectrometer

We present a thermally tunable microring resonator (MRR) implemented on a Ge-on-insulator (Ge-OI) photonic platform tailored for mid-infrared spectrometer applications. Thanks to the favorable thermo-optic effect of Ge, we characterized the optical and thermal properties of the thermally tunable Ge-OI MRR through rigorous optical and thermal numerical analyses. Building upon the simulation, a ring-shaped Au heater was successfully integrated into the Ge-OI MRR that was fabricated by using a direct wafer bonding process, followed by electron-beam lithography and dry etching techniques. Observations via thermo-reflectance microscopy revealed the temperature change within the Ge induced by heat transfer from the applied bias to the Au heater. Notably, the measured temperature change of 17 K at an applied electrical power of 181.7 mW closely aligned with the simulated values. In optical measurement, the heater-integrated Ge-OI MRR exhibited the tunability of 33.7 nm/W (0.36 nm/K) and the loaded Q factor of 21k at 4.2 µm wavelength with no bias. Hence, our demonstration of the Ge-OI tunable ring filter for mid-IR spectrometers could be a promising technology employing photonic integrated circuits for diverse applications in optical communication and spectral sensing.

Micro-nanojauges design to monitor surface mechanical state during high temperature oxidation of metals with application to 17-4PH stainless steel

Determination of mechanical state of thermal oxide growing during high temperature oxidation is a challenge. Fabrication of nanogauges for monitoring during high temperature oxidation was presently investigated up to 1000 °C. Several materials were tested in terms of mechanical behaviour and maximum working temperature for gauges used as markers during thermal loading under air. The experimental determination of the optimized gauges material for high temperature oxidation was validated. SiO2 offers particularly interesting features for gauges to determine the mechanical state of metal/oxide system. In this article, a special attention has also been paid to two nano-fabrication processes, as well as their limits. The standard electron beam lithography process is well suited to build gauges for oxidation applications, and can be improved by use of reactive ion etching process. The gauges can eventually reach several micrometers height such that the oxidation layer does not cover the gauges during thermal loading for relevant monitoring at short oxidation times. To illustrate, an application to a 17-4PH stainless steel oxidized at 480 °C is proposed and stress kinetics are deduced and related to an advanced thermomechano-chemical model, as well as identification of the numerical values of different thermomechano-chemical parameters associated to mechanisms of growth or relaxation.

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.

Conjugated Polymer-Based Photo-Crosslinker for Efficient Photo-Patterning of Polymer Semiconductors.

Photo-patterning of polymer semiconductors using photo-crosslinkers has shown potential for organic circuit fabrication via solution processing techniques. However, the performance of patterning, including resolution (R), UV light exposure dose, sensitivity (S), and contrast (γ), remains unsatisfactory. In this study, a novel conjugated polymer based photo-crosslinker (PN3, Figure 1a) is reported for the first time, which entails phenyl-substituted azide groups in its side chains. Due to the potential π-π interactions between the conjugated backbone of PN3 and those of polymer semiconductors, PN3 exhibits superior miscibility with polymer semiconductors compared to the commonly used small molecule photo-crosslinker 4Bx (Figure 1a). Consequently, photo-patterning of polymer semiconductors with PN3 demonstrates improved performance with much lower UV light exposure dose, higher S and higher γ compared to 4Bx. By utilizing electron beam lithography, patterned arrays of polymer semiconductors with resolutions down to 500nm and clearer edges are successfully fabricated using PN3. Furthermore, patterned arrays of PDPP4T, the p-type semiconductor (Figure 1b), after being doped, can function as source-drain electrodes for fabricating field-effect transistors (FETs) with comparable charge mobility and significantly lower sub-threshold swing value compared to those with gold electrodes.