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A Novel Hybrid Removal Technology for High-Aspect-Ratio SU-8 Micromolds in ECF (Electro-Conjugate Fluid) Micropumps Fabrication by UV-LIGA
摘要： Previously, we have developed ECF micropumps with triangular prism and slit electrode pairs (TPSEs) fabricated by the UV-LIGA. However, the previous KMPR molds have a limit to attain higher-aspect-ratio TPSEs. As a promising substitute, the ultrathick SU-8 molds are preferable for the TPSEs due to higher-aspect-ratio ability, but their difficult removal remains an annoying problem. To solve this problem, we first propose a novel hybrid removal method combining CO2 laser engraving with O2/CF4 plasma to achieve the fast, non-swelling, and complete removal of ultrathick SU-8 micromolds for higher-aspect-ratio TPSEs. The CO2 laser engraving is utilized as the main process to remove most SU-8, while the O2/CF4 plasma is adopted as the post-treatment to remove the remaining SU-8. To gather the proper fabrication conditions, we quantitatively analyze the effects of laser power, laser scan speed, and laser-pass numbers on the SU-8 ablation thickness. We successfully fabricated TPSEs of 590 μm and 970 μm in height by selectively removing SU-8 micromolds of 620 and 1100 μm in thickness. This achievement confirmed that our hybrid removal technology could remove the crosslinked SU-8 effectively and efficiently. We further experimentally proved the fascinating potential of our hybrid removal in improving the output performance of ECF micropumps. This promising hybrid removal opens the door to the easier fabrication of ultrathick metallic microstructures by UV-LIGA.
关键词： high aspect ratio,ECF micropump,CO2 laser engraving,SU-8 removal,triangular prism & slit electrode pair
更新于2025-09-23 15:22:29
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High-Resolution, High-Aspect-Ratio Printed and Plated Metal Conductors Utilizing Roll-to-Roll Microscale UV Imprinting with Prototype Imprinting Stamps
摘要： Micron-scale, high-aspect-ratio features were imprinted by a roll-to-roll process into a UV-curable polymer and used to create high-current-carrying conductive networks on plastic substrates. A stamp fabrication method was developed to create low-cost, rapidly produced roll-to-roll imprinting stamps, which can mold features from 3 μm to 1 mm wide. Isolated raised features 50 μm high were molded from a 25-μm-thick layer of UV-curable resin by displacing resin into raised features in the stamp. Substrates with imprinted capillary channels were used to form electrical conductors by printing a silver ink into reservoirs connected to the channels and allowing capillary flow to coat the channel. Copper electroless plating then filled the channels. The conductors demonstrate high resolution, high aspect ratio (～5:1 height:width), low resistance per length, and easy integration into networks. This roll-to-roll imprinting process provides a foundation for high-throughput manufacturing of high-resolution printed electronics.
关键词： high-aspect-ratio,conductive networks,roll-to-roll imprinting,UV-curable polymer,printed electronics
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Singapore, Singapore (2018.4.22-2018.4.26)] 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Fabrication of SU-8 Microtowers for a 100-Turn Toroid Inductor
摘要： This paper presents a fabrication of extremely thick SU-8 photoresist process in a height range of 1000 μm to 2000 μm high-aspect-ratio microstructures. To differentiate conventional high-aspect-ratio tall structures less than 1000 μm, a new term, microtower, was adopted for the microstructure with a height of 1000 μm or taller. In fabrication process, to avoid a long softbaking process from the thick photoresist and provide uniform film thickness, an SU-8 dry film was adopted. Ultra-violet (UV) light exposure with an acrylic filter was investigated in terms of transparency of the applicable wavelength spectrum. An array of the 1000-μm tall microtower array was fabricated without the acrylic filter resulting in wavy sidewalls. Whereas an array of 2000-μm tall microtower was fabricated with the acrylic filter resulting straight sidewalls. An array of 1500-μm-long inclined V-pillars was also successfully fabricated by adopting the UV exposure with the acrylic filter, and the fabricated microstructures have potential use as a microfilter in microfluidics. A state-of-art 100-turn toroid inductor was successfully fabricated and electrically characterized resulting an average inductance of 950 nH in the frequency range of 0.1 to 10 MHz. A low-frequency resistance of 5.4 Ω at 0.1 MHz and a quality factor of 22 at 60 MHz were measured.
关键词： Micro tower,High aspect ratio,3-D Toroid inductor
更新于2025-09-19 17:15:36
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3D Microlithography Using an Integrated System of 5-mm UV-LEDs with a Tilt-Rotational Sample Holder
摘要： This paper demonstrates a 3D microlithography system where an array of 5 mm Ultra Violet-Light Emitting Diode (UV-LED) acts as a light source. The unit of the light source is a UV-LED, which comes with a length of about 8.9 mm and a diameter of 5 mm. The whole light source comprises 20 × 20 matrix of such 5 mm UV-LEDs giving a total number of 400 LEDs which makes it a very favorable source with a large area for having a batch production of the desired microstructures. This light source is able to give a level of precision in microfabrication which cannot be obtained using commercial 3D printers. The whole light source performs continuous rotational movement once it is turned on. This can also move up and down in a vertical direction. This multidirectional light source also comprises a multidirectional sample holder. The light source teaming up with the multidirectional sample holder highly facilitates the process of fabrication of a huge range of 3D structures. This article also describes the different levels of characterization of the system and demonstrates several fabricated 3D microstructures including high aspect ratio vertical micro towers, twisted turbine structures, triangles, inclined pillar ‘V’ structures, and hollow horn structures as well.
关键词： Ultra Violet (UV) lithography,high aspect ratio,SU8 microstructure,3D microstructure,tilt rotational sample holder
更新于2025-09-19 17:13:59
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Micro‐/Nanopillars for Micro‐ and Nanotechnologies Using Inductively Coupled Plasmas
摘要： Herein, the plasma etching mask transfer of the resistance of e-beam resists, both negative and positive, as well as nanoparticle masks and hard masks are investigated. Various microscale and nanoscale features are exposed under plasma etching chemistries and are examined through both Bosch and pseudo-Bosch processes using an inductive-coupled plasma-deep reactive ion etching (ICP-DRIE) system. The selection of masks transfer proposed in this work provides better flexibility and cost-effective processing. The etch profile depending on plasma etching process and feature size is studied and highlighted. In particular, nanopillars are etched to a length of 10 μm and a diameter of 280 nm with a good aspect ratio (>30) yielding a selectivity of better than 100:1 and a satisfactory vertical profile.
关键词： plasma etching,micropillars,high aspect ratio,inductive-coupled plasma-deep reactive ion etching,nanopillars,selectivity
更新于2025-09-19 17:13:59
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Enhanced metal assisted etching method for high aspect ratio microstructures: Applications in silicon micropillar array solar cells
摘要： A solar cell device, fabricated on high density array cylindrical pillars, enables photogenerated carrier collection in the radial direction, thus shortening the path length of the carriers reaching the junction. It also provides advantages over conventional planar junction solar cells, such as reduced surface re?ectance and enhanced light trapping. In this study, highly ordered Si micropillars were fabricated by photolithography and metal assisted etching (MAE) methods. It is shown that the use of ethanol as a solvent during the etching process and increasing HF concentration in the MAE solution both improve the quality of the surfaces of the pillars. Micropillars with smooth sidewalls and a high aspect ratio were obtained in this way. Solar cells with a radial junction were then fabricated on these micropillars. Standard doping, SiO2/SiNx passivation, and metallisation steps were carried out for the fabrication of solar cells with di?erent micropillar lengths. A signi?cant decrease in re?ectance values was observed as the micropillar length increased, as expected. Solar cell short circuit current density (Jsc) and e?ciency (η) of the solar cells tended to increase with micropillar length up to 11.5 μm and then decrease due to increased surface recombination. The maximum e?ciency achieved in this study is 17.26%.
关键词： Solar cell,Ethanol,Micropillar,Metal assisted etching,High aspect ratio,Radial junction
更新于2025-09-16 10:30:52
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Ultrasensitive and Selective Gas Sensor Based on a Channel Plasmonic Structure with an Enormous Hot-spot Region.
摘要： We present experimental and theoretical studies of a metamaterial based plasmonic structure to build a plasmonic-molecular coupling detection system. High molecular sensitivity is realized only when molecules are located in the vicinity of the enhanced field (hot-spot region); thus, introducing target molecules in the hot-spot region to maximize plasmonic-molecular coupling is crucial to developing the sensing technology. We design a metamaterial consisting of a vertically oriented metal insulator metal (MIM) structure with a 25 nm channel sandwiched between two metal films, which enables the delivery of molecules into the large ravine-like hot-spot region, offering an ultrasensitive platform for molecular sensing. This metamaterial is applied to carbon dioxide and butane detection. We design the structure to exhibit resonances at 4033 cm?1 and 2945 cm-1, which overlap with the C=O and –CH2 vibration modes, respectively. The mutual coupling of these two resonance modes creates a Fano resonance, and their distinct peaks are clearly observed in the corresponding transmission dips. In addition, owing to its small footprint, such a vertical oriented MIM structure enables us to increase the integration density and allows the detection of a 20 ppm concentration with negligible background noise and high selectivity in the mid-infrared region.
关键词： high aspect ratio structure,gas sensor,enormous hot-spot region,Fano resonance,metal insulator metal (MIM) structure
更新于2025-09-16 10:30:52
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High Aspect Ratio Microstructuring of Copper Surfaces by Means of Ultrashort Pulse Laser Ablation
摘要： Laser beam machining (LBM) is capable of almost force-free 2D and 3D machining of any kind of material without tool wear. This process is defined by many parameters, such as pulse energy, frequency, scanning velocity and number of scanning repetitions. Modern laser machines provide high energy at shorter pulse durations and have more precise positioning systems than machines of the past. These can easily fulfil today’s continuous changing product requirements. For an overall understanding, an extensive amount of experimentation is required to display the interaction laws and dependencies between process parameters, as well as the resulting shapes and quality of the machined surface. By using an ultrashort pulse (USP) laser, a wide range of customer oriented applications in micrometer scale can be addressed, which leads to precise ablation with minimal thermal damage. This paper provides knowledge on the machining of copper micro features with high aspect ratio and a 532 nm wavelength laser beam. Aspect ratios up to 17 and slot widths smaller than 20 μm were performed with a beam radius ω0 smaller than 5 μm and pulse duration smaller than 12 ps. For desired slot geometries, necessary process parameters were developed and their physical limits are shown and discussed. The limits of minimum structure size have been analysed by observing the remaining material between slots at decreasing distances. Material debris deposits on the non-machined surface, as well as chemical changes of copper, were analysed using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). Special attention was given to the taper angle, which arises due to the Gaussian distribution of energy in the laser beam.
关键词： cold laser ablation,micro machining,high aspect ratio
更新于2025-09-12 10:27:22
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Laser direct printing of solder paste
摘要： We experimentally demonstrated a laser-based approach for the maskless printing of solder paste with a predefined size and position. In this work, a 532 nm laser marking system is used to induce the formation of a solder paste bridge between the donor and acceptor substrate. After the donor is removed vertically, the bridge will rupture and a high aspect ratio voxel can be obtained on the acceptor substrate. The width and height of transferred voxels can be controlled by modifying the laser fluence. In order to find out the specific conditions for the solder paste bridge formation, we carried out transfer experiments at different gap distances and found out a bridge formation threshold. Solder paste bridges can be produced only when the gap distance is smaller than the threshold. Furthermore, the threshold can be affected by the film thickness and spot size. In this condition, a solder paste array with an average size of 100 μm and a pitch of 200 μm has been successfully transferred. Compared to conventional printing methods, the method proposed in this paper can effectively improve the transfer accuracy and reduce the production cost.
关键词： laser direct printing,laser-induced forward transfer,solder paste,high aspect ratio voxel,maskless printing
更新于2025-09-12 10:27:22
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Fabrication and Optimization of High Aspect Ratio Through-Silicon-Vias Electroplating for 3D Inductor
摘要： In this study, the ?lling process of high aspect ratio through-silicon-vias (TSVs) under dense conditions using the electroplating method was ef?ciently achieved and optimized. Pulsed power was used as the experimental power source and the electroplating solution was prepared with various additive concentrations. Designed control variable experiments were conducted to determine the optimized method. In the control variable experiments, the relationship of multiple experimental variables, including current density (0.25–2 A/dm2), additive concentration (0.5–2 mL/L), and different shapes of TSVs (circle, oral, and square), were systematically analyzed. Considering the electroplating speed and quality, the in?uence of different factors on experimental results and the optimized parameters were determined. The results showed that increasing current density improved the electroplating speed but decreased the quality. Additives worked well, whereas their concentrations were controlled within a suitable range. The TSV shape also in?uenced the electroplating result. When the current density was 1.5 A/dm2 and the additive concentration was 1 mL/L, the TSV ?lling was relatively better. With the optimized parameters, 500-μm-deep TSVs with a high aspect ratio of 10:1 were fully ?lled in 20 h, and the via density reached 70/mm2. Finally, optimized parameters were adopted, and the electroplating of 1000-μm-deep TSVs with a diameter of 100 μm was completed in 45 h, which is the deepest and smallest through which a three-dimensional inductor has ever been successfully fabricated.
关键词： electroplating,high aspect ratio,through-silicon-vias (TSV),three-dimensional (3D) inductor,control variable method
更新于2025-09-09 09:28:46