Photolithography Method Research Articles

Sheet-on-sheet fixed target data collection devices for serial crystallography at synchrotron and XFEL sources

Serial crystallography (SX) efficiently distributes over many crystals the radiation dose absorbed during diffraction data acquisition, enabling structure determination of samples at ambient temperature. SX relies on the rapid and reliable replacement of X-ray-exposed crystals with fresh crystals at a rate commensurate with the data acquisition rate. `Solid supports', also known as `fixed targets' or `chips', offer one approach. These are microscopically thin solid panes into or onto which crystals are deposited to be individually interrogated by an X-ray beam. Solid supports are generally patterned using photolithography methods to produce a regular array of features that trap single crystals. A simpler and less expensive alternative is to merely sandwich the microcrystals between two unpatterned X-ray-transparent polymer sheets. Known as sheet-on-sheet (SOS) chips, these offer significantly more versatility. SOS chips place no constraint on the size or size distribution of the microcrystals or their growth conditions. Crystals ranging from true nanocrystals up to microcrystals can be investigated, as can crystals grown in media ranging from low viscosity (aqueous solution) up to high viscosity (such as lipidic cubic phase). Here, we describe our two SOS devices. The first is a compact and lightweight version designed specifically for synchrotron use. It incorporates a standard SPINE-type magnetic base for mounting on a conventional macromolecular crystallography goniometer. The second and larger chip is intended for both X-ray free-electron laser and synchrotron use and is fully compatible with the fast-scanning XY-raster stages developed for data collection with patterned chips.

Mask optimization for optical lithography based on UNet

Abstract Traditional photolithography methods are increasingly unable to meet the ever-stringent demands for pattern resolution and alignment accuracy, and developing efficient mask optimization techniques has become an urgent need in the industry. This paper delves into the application of Inverse Lithography Technology (ILT) in nanoscale photolithography and proposes an improved mask optimization algorithm. The backbone network of this algorithm employs a UNet architecture, trained initially on a prepared dataset comprising original masks and the ones optimized through traditional methods. The pre-trained backbone network generates a coarse mask, which is then inputted into a correction layer to refine the mask, enhancing pattern accuracy and processing efficiency. Compared to traditional gradient-based mask optimization methods, neural ILT demonstrates superior effectiveness, which enhances the efficiency and pattern quality of the lithography process while reducing production costs.

Artificial intelligence-based droplet size prediction for microfluidic system

PurposeThis study aims to introduce a vision-based model to generate droplets with auto-tuned parameters. The model can auto-adjust the inherent uncertainties and errors involved with the fabrication and operating parameters in microfluidic platform, attaining precise size and frequency of droplet generation.Design/methodology/approachThe photolithography method is utilized to prepare the microfluidic devices used in this study, and various experiments are conducted at various flow-rate and viscosity ratios. Data for droplet shape is collected to train the artificial intelligence (AI) models.FindingsGrowth phase of droplets demonstrated a unique spring back effect in droplet size. The fully developed droplet sizes in the microchannel were modeled using least absolute shrinkage and selection operators (LASSO) regression model, Gaussian support vector machine (SVM), long short term memory (LSTM) and deep neural network models. Mean absolute percentage error (MAPE) of 0.05 and R2 = 0.93 were obtained with a deep neural network model on untrained flow data. The shape parameters of the droplets are affected by several uncontrolled parameters. These parameters are instinctively captured in the model.Originality/valueExperimental data set is generated for varying viscosity values and flow rates. The variation of flow rate of continuous phase is observed here instead of dispersed phase. An automated computation routine is developed to read the droplet shape parameters considering the transient growth phase of droplets. The droplet size data is used to build and compare various AI models for predicting droplet sizes. A predictive model is developed, which is ready for automated closed loop control of the droplet generation.

Spatial light assisted femtosecond laser direct writing of a bionic superhydrophobic Fresnel microlens arrays

High quality imaging and self-cleaning function are two significant factors for Fresnel Microlens Arrays (FMLAs) to operate properly in outdoor environment. Bionic superhydrophobic FMLAs are explored for outdoor uses due to their ability allowing free rolling down of water droplets taking away dust particles. Current photolithographic method of fabricating FMLAs involves multi-processing steps, which increase the complexity of the microlens array structure as well as reduces the optical imaging capability of the lenses. In this study, we report a method for creating bionic superhydrophobic FMLAs by integrating the Nepenthes Alata crescent structures with FMLAs fabricated by spatial light assisted femtosecond laser direct writing, i.e. Two-Photon Polymerization (TPP). The fabricated FMLAs were further modified with Perfluorooctyltrimethoxysilane (F13) to enhance hydrophobicity and surface uniformity. Results show that the optimized bionic FMLAs exhibit superhydrophobicity in different liquid media and excellent self-cleaning ability. The water contact angle (CA) reached 156.3°, a low rolling angle of 4.7°, and surface adhesion force of 25.5 μN. The FMLAs designed have excellent imaging characteristics and focusing ability. This research provides insights into the fabrication and performance optimization of bionic superhydrophobic FMLAs, offering potential applications for outdoor optical systems.

Photoinduced Dehalogenation‐Based Direct In Situ Photolithography of CsPbBr3 Quantum Dots Micropatterns for Encryption and Anti‐Counterfeiting with High Capacity

Fluorescent lead halide perovskite quantum dots (LH PQDs) micropatterns hold great potential for photonic applications. However, current photolithography for LH PQDs micropatterning is hindered by their incompatibility with traditional photolithography methods, which involve development processes using numerous solvents and exhibit poor stability due to the ionic characteristics of LH PQDs. Herein, a direct in situ photolithography to fabricate CsPbBr3 PQDs micropatterns based on ultraviolet‐C light‐driven debromination is developed. Using this approach, fluorescent CsPbBr3 PQDs micropatterns with high theoretical information storage capacity (up to 10750205) can be achieved in a single step, without the need for tedious development processes. Furthermore, the fabricated CsPbBr3 PQDs micropatterns show high stability, remaining undamaged even after immersion in water for 6 months. The combination of excellent optical properties, development‐free process, high stability, and low cost makes the in situ photolithography strategy very promising for patterning LH PQDs toward photonic integrations.

Overcoming oxygen inhibition in UV photolithography for the fabrication of low-loss polymer waveguides.

Perfluorinated acrylate polymer materials exhibit low absorption loss at 1310 and 1550 nm, but molecular oxygen inhibits their photocuring. We propose a novel, to our knowledge, UV photolithography method incorporating a pre-exposure process for fabricating low-loss perfluorinated acrylate polymer waveguides. During the pre-exposure process, a partially cured thin layer forms on the core layer, effectively overcoming oxygen inhibition in subsequent lithography. Furthermore, the functional group contents of the polymerized materials were characterized by a Raman spectrometer to analyze the development reaction under the pre-exposure layer. Utilizing this improved method, we fabricated a straight waveguide with a length of 21 cm. The experiments showed that the propagation losses are 0.14 dB/cm at 1310 nm and 0.51 dB/cm at 1550 nm. The inter-channel cross talk for a core pitch of 250 µm was measured as low as -49 dB at 1310 nm. Error-free NRZ data transmission over this waveguide at 25 Gb/s was achieved, showcasing the potential in optical interconnect and communication applications.

A point-of-care electrochemical biosensor for the rapid and sensitive detection of biomarkers in murine models with LPS-induced sepsis

Sepsis is a life-threatening condition, which is irreversible if diagnosis and intervention are delayed. The response of the immune cells towards an infection triggers widespread inflammation through the production of cytokines, which may result in multiple organ dysfunction and eventual death. Conventional detection techniques fail to provide a rapid diagnosis because of their limited sensitivity and tedious protocol. This study proposes a point-of-care (POC) electrochemical biosensor that overcomes the limitations of current biosensing technologies in the clinical setting by its integration with electrokinetics, enhancing the sensitivity to picogram level compared with the nanogram limit of current diagnostic technologies. This biosensor promotes the use of a microelectrode strip to address the limitations of conventional photolithographic fabrication methods. Tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and microRNA-155 (miR-155) were monitored in a lipopolysaccharide (LPS)-induced septic mouse model. The optimum target hybridization time in a high conductivity medium was observed to be 60 s leading to the completion of the whole operation within 5 min compared with the 4-h detection time of the traditional enzyme-linked immunosorbent assay (ELISA). The limit of detection (LOD) was calculated to be 0.84, 0.18, and 0.0014 pg mL−1, respectively. This novel sensor may have potential for the early diagnosis of sepsis in the clinical setting.

Ligand-Nondestructive Direct Photolithography Assisted by Semiconductor Polymer Cross-Linking for High-Resolution Quantum Dot Light-Emitting Diodes.

The photolithographic patterning of fine quantum dot (QD) films is of great significance for the construction of QD optoelectronic device arrays. However, the photolithography methods reported so far either introduce insulating photoresist or manipulate the surface ligands of QDs, each of which has negative effects on device performance. Here, we report a direct photolithography strategy without photoresist and without engineering the QD surface ligands. Through cross-linking of the surrounding semiconductor polymer, QDs are spatially confined to the network frame of the polymer to form high-quality patterns. More importantly, the wrapped polymer incidentally regulates the energy levels of the emitting layer, which is conducive to improving the hole injection capacity while weakening the electron injection level, to achieve balanced injection of carriers. The patterned QD light-emitting diodes (with a pixel size of 1.5 μm) achieve a high external quantum efficiency of 16.25% and a brightness of >1.4 × 105 cd/m2. This work paves the way for efficient high-resolution QD light-emitting devices.

Improving morphological and functional properties of enteric neuronal networks in vitro using a novel upside-down culture approach.

The enteric nervous system (ENS) comprises millions of neurons and glia embedded in the wall of the gastrointestinal tract. It not only controls important functions of the gut but also interacts with the immune system, gut microbiota, and the gut-brain axis, thereby playing a key role in the health and disease of the whole organism. Any disturbance of this intricate system is mirrored in an alteration of electrical functionality, making electrophysiological methods important tools for investigating ENS-related disorders. Microelectrode arrays (MEAs) provide an appropriate noninvasive approach to recording signals from multiple neurons or whole networks simultaneously. However, studying isolated cells of the ENS can be challenging, considering the limited time that these cells can be kept vital in vitro. Therefore, we developed an alternative approach cultivating cells on glass samples with spacers (fabricated by photolithography methods). The spacers allow the cells to grow upside down in a spatially confined environment while enabling acute consecutive recordings of multiple ENS cultures on the same MEA. Upside-down culture also shows beneficial effects on the growth and behavior of enteric neural cultures. The number of dead cells was significantly decreased, and neural networks showed a higher resemblance to the myenteric plexus ex vivo while producing more stable signals than cultures grown in the conventional way. Overall, our results indicate that the upside-down approach not only allows to investigate the impact of neurological diseases in vitro but could also offer insights into the growth and development of the ENS under conditions much closer to the in vivo environment.NEW & NOTEWORTHY In this study, we devised a novel approach for culturing and electrophysiological recording of the enteric nervous system using custom-made glass substrates with spacers. This allows to turn cultures of isolated myenteric plexus upside down, enhancing the use of the microelectrode array technique by allowing recording of multiple cultures consecutively using only one chip. In addition, upside-down culture led to significant improvements in the culture conditions, resulting in a more in vivo-like growth.

Herbal nanogels: Revolutionizing skin cancer therapy through nanotechnology and natural remedies

The escalating global incidence of skin cancer demands innovative therapeutic approaches that balance efficacy and reduced side effects. The convergence of nanotechnology and medicinal research has unveiled herbal nanogels as promising candidates for advancing skin cancer therapy. Skin cancer, comprising diverse malignancies, necessitates novel strategies to enhance treatment outcomes. Nanogels, intricate networks of cross-linked polymers at the nanoscale, have emerged as versatile vehicles for targeted drug delivery. Their ability to encapsulate a range of therapeutic agents and respond to stimuli offers a platform to revolutionize treatment paradigms. The taxonomy of nanogels encompasses physical cross-linked gels, liposome-modified nanogels, micellar nanogels, hybrid nanogels, and chemically cross-linked nanogels, each holding distinctive characteristics suitable for specific applications. The synthesis of nanogels is a precise craft involving techniques like photolithography, micro-moulding, and emulsion methods, enabling control over particle size, morphology, and drug-loading capacity. Stimuli-responsive nanogels present a dynamic facet of this field, exhibiting potential for targeted drug delivery. Noteworthy examples include LHRH-targeted nanogels and nanogels responsive to the intricate microenvironment of bacterial-accumulated tumors. One of the most intriguing developments lies in the fusion of herbal medicine and nanotechnology, paving the way for herbal nanogels. By incorporating bioactive plant-derived compounds into nanogel matrices, these constructs offer a holistic therapeutic approach. The convergence of nanotechnology and herbal medicine in the form of herbal nanogels presents a promising avenue for elevating skin cancer therapy. Through precise drug delivery mechanisms and responsiveness to complex microenvironments, nanogels exhibit a potential to reshape treatment norms. This comprehensive review provides an in-depth roadmap of the evolving landscape of herbal nanogels, illuminating their potential as effective, targeted, and minimally invasive tools for combating skin cancer.

Large scale integrated IGZO crossbar memristor array based artificial neural architecture for scalable in-memory computing

Neuromorphic systems based on memristor arrays have not only addressed the von Neumann bottleneck issue but have also enabled the development of computing applications with high accuracy. In this study, an artificial neural architecture based on a 10 × 10 IGZO memristor array is presented to emulate synaptic dynamics for performing artificial intelligence (AI) computing with high recognition accuracy rate. The large area 10 × 10 IGZO memristor array was fabricated using the photolithography method, resulting in stable and reliable memory operations. The bipolar switching at −2 V–2.5 V, endurance of 500 cycles, retention of >104 s, and uniform Vset/Vreset operation of 100 devices were achieved by modulating the oxygen vacancy in the IGZO film. The emulation of electric synaptic dynamics was also observed, including potentiation-depression, multilevel long-term memory (LTM), and multilevel short-term memory (STM), revealing highly linear and stable synaptic functions at different modulated pulse settings. Additionally, electrical modeling (HSPICE) with vector-matrix measurements and simulation of various artificial neural network (ANN) algorithms, such as convolution neural network (CNN) and spiking neural network (SNN), were performed, demonstrating a linear increase in current accumulation with high recognition rates of 99.33 % and 86.46 %, respectively. This work provides a novel approach for overcoming the von Neumann bottleneck issue and emulating synaptic dynamics in various neural networks with high accuracy.

Direct wire writing technique benefitting the flexible electronics

ABSTRACT This work proposes a rapid manufacturing technique for the conductive lines applied in flexible electronics, which is referred to as the ‘direct wire writing (DWW)’ technique. The fine metal wire is dragged out of the needle by adhesion, and attached to the stick-on substrate synchronously along design paths to form high-quality circuits. This technique overcomes the unstable performance of ink-based conductive lines fabricated by screen printing, spraying, 3D printing, etc., and avoids complex processes for stable metallic circuits mainly manufactured by the photolithography method, etc. Firstly, the forming mechanism of dominating the micro deformation behaviour (local-debonding, slip, warping) is clarified and analysed, which provides guidelines for fabricating in-plane wire patterns and 3D structural circuits rapidly and easily. Subsequently, some practical applications, including strain rosette, wearable sensor patch and light display are presented, showing the promising potential of the DWW technique in the ongoing exploration of flexible electronics.

Methods for extending working distance using modified photonic crystal for near-field lithography

Near-field lithography has evident advantages in fabricating super-resolution nano-patterns. However, the working distance (WD) is limited due to the exponential decay characteristic of the evanescent waves. Here, we proposed a novel photolithography method based on a modified photonic crystal (PC), where a defect layer is embedded into the all-dielectric multilayer structure. It is shown that this design can amend the photonic band gap and enhance the desired high-k waves dramatically, then the WD in air conditions could be extended greatly, which would drastically relax the engineering challenges for introducing the near-field lithography into real-world manufacturing applications. Typically, deep subwavelength patterns with a half-pitch of 32 nm (i.e., λ/6) could be formed in photoresist layer at an air WD of 100 nm. Moreover, it is revealed that diversified two-dimensional patterns could be produced with a single exposure using linear polarized light. The analyses indicate that this improved dielectric PC is applicable for near-field lithography to produce super-resolution periodic patterns with large WD, strong field intensity, and great uniformity.

Laser fabrication of lead selenide infrared focal plane array devices

The motivation of this work is to demonstrate the versatility and potential of laser processing in the fabrication of PbSe thin films and focal plane array devices. This work fabricates an FPA device with any need for the suite of equipment and chemicals necessary for photolithography and etching. Advances in laser technologies and the vast number of laser parameters available are enabling the huge potential for laser processing of thin films and device fabrication. This can be accomplished faster using lasers with fewer steps than using conventional thin film deposition and photolithography methods. This work presents the fabrication and simple operation of a proof-of-concept PbSe-based, 120-pixel PFA (10 × 12 pixel) focal plane array using only laser processing for film deposition and device patterning. Lasers were used to both deposition and pattern a PbSe film with 60 × 70 µm pixels with 100 µm pitch with a unit cell photoresponse of 17% DelR. Additional results, challenges, limitations, and suggested future improvements are presented.

Dielectric optical waveguide fabricated on a transparent substrate

Transparent glass substrates are routinely used in the fabrication of metasurfaces, augmented reality (AR), virtual reality (VR), and holographic devices. While readily compatible with photolithographic patterning methods, when electron beam (E-Beam) techniques are used, field distortion and stitching errors can result due to the buildup of charge. A common approach to overcome this issue is to deposit a thin conductive polymer layer (E-Spacer). However, if high-voltage E-Beam is used to achieve nano-features, the polymer conductivity is not sufficient. We have shown that by using chromium (Cr) as an overcoating conductive layer on the resist, we can achieve accurate and seamless patterning in multiple writing fields and used the method to fabricate on-chip Si3N4 waveguides on SiO2. This technique has the potential to enable the fabrication of large-scale integrated photonic systems on transparent or dielectric substrates.

Low-damage photolithography for magnetically doped (Bi,Sb)2Te3 quantum anomalous Hall thin films

We have developed a low-damage photolithography method for magnetically doped (Bi,Sb)2Te3 quantum anomalous Hall (QAH) thin films incorporating an additional resist layer of poly(methyl methacrylate) (PMMA). By performing control experiments on the transport properties of five devices at varied gate voltages (V gs), we revealed that the modified photolithography method enables fabricating QAH devices with the transport and magnetic properties unaffected by fabrication process. Our experiment represents a step towards the production of novel micro-structured electronic devices based on the dissipationless QAH chiral edge states.

Microstructural and micromechanical characterization of sintered nano-copper bump for flip-chip heterogeneous integration

Copper nanoparticles (CuNPs) sintering for flip-chip interconnects is a promising solution for 3D and heterogeneous integration to overcome the limitation of solder materials. To this end, we perform the photolithographic stencil printing method to pattern CuNPs, and the form of flip-chip interconnects is completed after CuNPs sintering process. This paper aims to study the effect of sintering processing parameters (time, pressure, temperature) on the mechanical properties of CuNPs bumps when applying the novel method to approach the Cu interconnects. We fabricated seven groups of specimens of sintered CuNPs bumps, built with a diameter of 100 μm and sintered. The nanoindentation tests assessed the mechanical property to get Young's modulus and hardness. Results clarify that Young's modulus is strongly affected by pressure. An suggested combination of parameters (the 25 MPa and 260 °C for 15 min) give the highest modulus of 126 GPa and the hardness of 1.76 GPa. Moreover, the observations by scanning electron microscopy (SEM) reveal the microstructure and porosity evolution versus different processing parameters.

Development of YBCO Patterned Multi-Filamentary Film Using Photolithography Method

High-temperature superconducting (HTS)-coated conductors (CCs) can be applied to magnets under low temperature and high magnetic field conditions, as well as in electric power equipment. Reducing the screening current and AC loss is an important topic for practical applications. In this study, we propose a multifilamentary YBCO thin film, fabricated by depositing YBCO on a substrate with elevated Zr stripes patterned by using photolithography techniques. While the thin film exhibited superconductivity, the crystal grain orientation was disturbed above the stripe, which locally inhibited the superconducting current flow. The results of this study indicate that a continuous YBCO film can be dividing into separate superconducting filaments by locally suppressing the good grain alignment required for a high intergrain <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> with Zr stripes between the STO substrate and the YBCO film.

Fabrication of Robust Paper-Based Electronics by Adapting Conventional Paper Making and Coupling with Wet Laser Writing

Paper offers the potential as a sustainable substrate for electronics, yet a key remaining challenge is patterning. While most demonstration studies pattern by printing conducting inks onto cellulose, we adapt conventional paper making to create a stable non-conducting composite of graphene oxide (GO; 30%) and cellulose (70%) and then pattern this composite using wet laser writing. Specifically, the GO/cellulose composite is as follows: soaked in a HAuCl4 solution; laser patterned to simultaneously reduce GO (rGO) and generate metallic gold seeds (typical writing speed 20 s·cm–2); and then incubated (30 min) in HAuCl4 solution to “grow” gold nanoparticles (Au NPs) in the pre-seeded patterned region. Various methods demonstrate that laser patterning induces spatially selective chemical changes in the composite. Functionally, the patterned region (Au NPs/rGO/cellulose) shows a 200-fold increase in conductivity (1362 S m–1) compared to the unpatterned region (GO/cellulose). As a simple demonstration, we fabricated patterned composite paper electrodes and demonstrate excellent electrochemical sensing performance in terms of sensitivity, selectivity, stability, and repeatability. We envision that laser patterning of composite paper offers unprecedented opportunities for scalable manufacturing because conventional papermaking can generate the stable substrate and laser patterning can be extended from serial writing to parallel photolithographic methods common in electronics fabrication.

Bioinspired Adhesive Manufactured by Projection Microstereolithography 3D Printing Technology and Its Application

AbstractMany methods are used to manufacture bioinspired adhesive arrays such as photolithography and nanoimprinting methods, which are very high cost and time‐consuming. In this manuscript, projection microstereolithography 3D printing method is firstly adopted to prepare the bioinspired dry adhesive in several micrometers, which is low cost, time saving, convenient and can realize rapid, large‐scale, high‐precision, and controllable complex structure manufacture. The morphology and adhesive properties of four kinds of adhesive with flat punch, mushroom‐shaped, suction cup‐shaped, and titled micropillar structures are investigated. Scanning electron microscope (SEM) observation shows that the very regular pattern of the adhesive is generated and no collapse phenomenon is observed. The adhesion test results show the mushroom‐shaped adhesive reach the maximum adhesion of 15 KPa, which can be maintained after repeated uses. The contact angle of the adhesive is 143.7°, showing the good self‐cleaning ability. The mushroom‐shaped adhesive exhibits excellent adhesion property, high repeatability, and good self‐cleaning ability, which is further applied in grasping and transferring various surfaces such as solar panels, printed circuit board, flanges, and so on.