• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.771-775
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• 2015

In this paper, we designed and fabricated low cost imprinting process for micro patterning on FCCL (flexible copper clad laminate). Compared to conventional imprinting process, developed fabrication method processing imprint and UV photolithography step simultaneously and it does not require resin etch process and it can also reduce the fabrication cost and processing time. Based on proposed method, patterns with $10{\mu}m$ linewidth are fabricated on $180mm{\times}180mm$ FCCL. Compared to conventional methods using LDI (laser direct imaging) equipment that showed minimum line with $10{\sim}20{\mu}m$, proposed method shows comparable pattern resolution with very competitive price and shorter processing time. In terms of mass production, it can be applied to fabrication of large-area low cost applications including FPCB.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.319-319
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• 2013

Even though the fabrication methods of metal oxide based thin film capacitor have been well established such as RF sputtering, Sol-gel, metal organic chemical vapor deposition (MOCVD), ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD), an applicable capacitor of printed circuit board (PCB) has not realized yet by these methods. Barium Strontium Titanate (BST) and other high-k ceramic oxides are important materials used in integrated passive devices, multi-chip modules (MCM), high-density interconnect, and chip-scale packaging. Thin film multi-layer technology is strongly demanded for having high capacitance (120 nF/$mm^2$). In this study, we suggest novel multi-layer thin film capacitor design and fabrication technology utilized by plasma assisted deposition and photolithography processes. Ba0.6Sr0.4TiO3 (BST) was used for the dielectric material since it has high dielectric constant and low dielectric loss. 5-layered BST and Pt thin films with multi-layer sandwich structures were formed on Pt/Ti/$SiO_2$/Si substrate by RF-magnetron sputtering and DC-sputtering. Pt electrodes and BST layers were patterned to reveal internal electrodes by photolithography. SiO2 passivation layer was deposited by plasma-enhanced chemical vapor deposition (PE-CVD). The passivation layer plays an important role to prevent short connection between the electrodes. It was patterned to create holes for the connection between internal electrodes and external electrodes by reactive-ion etching (RIE). External contact pads were formed by Pt electrodes. The microstructure and dielectric characteristics of the capacitors were investigated by scanning electron microscopy (SEM) and impedance analyzer, respectively. In conclusion, the 0402 sized thin film multi-layer capacitors have been demonstrated, which have capacitance of 10 nF. They are expected to be used for decoupling purpose and have been fabricated with high yield.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.3
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• pp.197-203
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• 2004

New lithography techniques are employed for the patterning of arbitrary shapes in nanometer scale. When, in the photolithography, the electromagnetic waves such as UV and X-ray are incident on the mask patterned in nanometer scale, the diffraction effect is unavoidable and degrades images of the mask imprinted on wafer. Only a convex lens is well-known Fourier transformer. It is possible to make the mask Fourier-transformed with the convex lens, even though the size of pattern on the mask is very large compared to the wavelength of electromagnetic wave. If the mask, modified according to new technique described in this paper, was placed at the front of the lens and was illuminated with laser beam, the nanometer-size patterns are only formed on the plane called Fourier transform plane. The new method presented here is quite simple setup and comparable with present and next generation lithographies such as UV/EUV photolithograpy and electron projection lithography when compared in attainable minimum linewidth. In this paper, we showed our theoretical research work in the field of Fourier optics, . In the near future, we are going to verify this theoretical work by experiments.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.1
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• pp.47-54
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• 2019

An experimental study was conducted on the wear and friction responses in sliding tests of a micro-textured surface on laser pattern (LP) steel as reduction gear material in electric guided vehicle. In this research, the friction characteristics of laser pattern steel under different micro texture density conditions were investigated. The friction tests were carried out at sliding speeds of 0.06 m/s to 0.34 m/s and at normal loads of 2 to 10 N. Photolithography method was used to create the dimples for surface texturing purpose. Four different specimens having different dimple densities of 10%, 12.5%, 15%, and 20% were observed respectively. In this research, friction conditions as shown in Stribeck curve were investigated. Furthermore, the microscopic surface was observed using scanning electron microscope. It was found that the dimple density had a significant role on the friction characteristics of laser pattern steel conditioned as reduction gear material in an agricultural vehicle. The duty number showed that the friction condition was hydrodynamic regime. The best performance was obtained from 12.5% dimple density with lowest friction coefficient achieved at 0.018771 under the velocity of 0.34 m/s and 10N load.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.3-8
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• 2006

The demand fer small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased by using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable fur mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-replication process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the surface profiles of master, mold and molded pattern were measured by optical scanning profiler. The geometrical deviation between the master and the molded DOE was less than $0.1{\mu}m$. The diffraction efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.35-40
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• 2005

The demand for small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable for mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-molding process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the shapes of master, mold and molded pattern were measured by optical scanning profiler. The deviation between the master and the molded DOE was less than 0.1um. The efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.429-434
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• 2021

The feasibility of lecithin as a material for dissolving microneedles to improve skin permeability of drugs and the effect of the composition of lecithin on the mechanical strength, solubility, and skin permeability of rhodamine B (RhB) of the dissolving microneedles were investigated. Dissolving microneedles with needles of uniform shape and size were fabricated with the mold made using the laser-writing technique, simpler and more efficient method compared to the photolithography method, the conventional method to fabricate the microneedle mold. The composition of lecithin in the microneedle affected the mechanical strength and solubility of the needle thus, the mechanical strength of the needle increased as the composition of lecithin in the needle increased, resulting in improving the skin permeability of RhB contained in the microneedles. When comparing the microneedles containing same composition of amylopectin (AP), the skin permeability of RhB of the microneedles containing lecithin was higher. These results indicate that lecithin can be used as a material for dissolving microneedles and the skin permeability of the microneedle could be controlled by changing the composition of lecithin.

• Particle and aerosol research
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• v.6 no.3
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• pp.131-138
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• 2010

Flexible electronics are the electronics on flexible substrates such as a plastic, fabric or paper, so that they can be folded or attached on any curved surfaces. They are currently recognized as one of the most innovating future technologies especially in the area of portable electronics. The conventional vacuum deposition and photolithographic patterning methods are well developed for inorganic microelectronics. However, flexible polymer substrates are generally chemically incompatible with resists, etchants and developers and high temperature processes used in conventional integrated circuit processing. Additionally, conventional processes are time consuming, very expensive and not environmentally friendly. Therefore, there are strong needs for new materials and a novel processing scheme to realize flexible electronics. This paper introduces current research trends for flexible electronics based on (a) nanoparticles, and (b) novel processing schemes: nanomaterial based direct patterning methods to remove any conventional vacuum deposition and photolithography processes. Among the several unique nanomaterial characteristics, dramatic melting temperature depression (Tm, 3nm particle~$150^{\circ}C$) and strong light absorption can be exploited to reduce the processing temperature and to enhance the resolution. This opens a possibility of developing a cost effective, low temperature, high resolution and environmentally friendly approach in the high performance flexible electronics fabrication area.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.3 s.180
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• pp.156-162
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• 2006

Direct fabrication of nano patterns has been studied employing a nano-stereolithography (NSL) process. The needs of nano patterning techniques have been intensively increased for diverse applications for nano/micro-devices; micro-fluidic channels, micro-molds. and other novel micro-objects. For fabrication of high-aspect-ratio (HAR) patterns, a thick spin coating of SU-8 process is generally used in the conventional photolithography, however, additional processes such as pre- and post-baking processes and expansive precise photomasks are inevitably required. In this work, direct fabrication of HAR patterns with a high spatial resolution is tried employing two-photon polymerization in the NSL process. The precision and aspect ratio of patterns can be controlled using process parameters of laser power, exposure time, and numerical aperture of objective lens. It is also feasible to control the aspect ratio of patterns by truncation amounts of patterns, and a layer-by-layer piling up technique is attempted to achieve HAR patterns. Through the fabrication of several patterns using the NSL process, the possibility of effective patterning technique fer various N/MEMS applications has been demonstrated.

• Progress in Superconductivity
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• v.4 no.2
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• pp.109-113
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• 2003

We have developed a planar-type single layer second-order $high-T_{c}$ SQUID gradiometer, which can detect the $d^2$$B_{z/}$dxdy of the second-order field gradient. This SQUID gradiometer consists of four-way 'clover-leaf' pick-up loops and is coupled directly to a 4-junction dc SQUID in such a way that the coupling polarity of the two diagonal loops is opposite to that of the other two loops. The pickup loops are intrinsically balanced for both uniform field and the 1 st-order field gradient. The $YBa_2$$Cu_3$$O_{7}$ thin film was made by pulsed laser deposition method on $SrTiO_3$ single crystal substrate and patterned by photolithography with Ar ion milling technique. Response of this gradiometer was tested for both uniform field and the 2nd-order field gradient. Details of the design, fabrication, and results will be discussed.