• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.7
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• pp.7-13
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• 2001

The wirebonding is a common interconnection technique for modern microwave devices because of rather simple and reliable processes involved. At millimeter-wave frequencies, however, the bondwire parasitics are significant and consequently limit the external performance of packaged devices. In this paper, we represent wideband characterization of multiple bondwires and ribbon in a frequency range from 20 to 35 GHz. From these results, the double bondwire shows very small insertion loss less than 0.55 dB up to 35 GHz and its performance is comparable to that of the ribbon in the millimeter-wave frequencies. Therefore, the wirebonding is very suitable for millimeter wave packaging in terms of performance and manufacturing cost.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.15-24
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• 2014

Recently, a variety of printing technologies, including ink jet, gravure, and roll-to-roll (R2R) printing, has generated intensive interest in the application of flexible and wearable electronic devices. However, the actual use of printing technique is much limited because the sintering process of the printed nanoparticle inks remains as a huge practical drawback. In the fabrication of the conductive metal film, a post-sintering process is required to achieve high conductivity of the printed film. The conventional thermal sintering takes considerable sintering times, and requires high temperatures. For application to flexible devices, the sintering temperature should be as low as possible to minimize the damage of polymer substrate. Several alternative sintering methods were suggested, such as laser, halogen lamp, infrared, plasma, ohmic, microwave, and etc. Eventually, the new sintering technique should be applicable to large area, R2R, and polymer substrate as well as low cost. This article reviews progress in recent technologies for several sintering methods. The advantages and disadvantages of each technology will be reviewed. Several issues for the application in R2R process are discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.370.1-370.1
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• 2014

Giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), and magnetic random-access memory (MRAM) are currently active areas of research. Magnetite, Fe3O4, is predicted to possess as half-metallic nature, ~100% spin polarization (P), and has a high Curie temperature (TC~850 K). On the other hand, Spinel ferrite CoFe2O4 has been widely studies for various applications such as magnetorestrictive sensors, microwave devices, biomolecular drug delivery, and electronic devices, due to its large magnetocrystalline anisotropy, chemical stability, and unique nonlinear spin-wave properties. Here we have investigated the magneto-transport properties of epitaxial CoxFe3-xO4 thin films. The epitaxial CoxFe3-xO4 (x=0; 0.4; 0.6; 1) thin films were successfully grown on MgO (100) substrate by molecular beam epitaxy (MBE). The quality of the films during growth was monitored by reflection high electron energy diffraction (RHEED). From temperature dependent resistivity measurement, we observed that the Werwey transition (1st order metal-insulator transition) temperature increased with increasing x and the resistivity of film also increased with the increasing x up to $1.6{\Omega}-cm$ for x=1. The magnetoresistance (MR) was measured with magnetic field applied perpendicular to film. A negative transverse MR was disappeared with x=0.6 and 1. Anomalous Hall data will be discussed.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.3
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• pp.31-36
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• 2000

We developed embedded inductors in MCM-D substrate for RF applications. The increasing demand for high density packaging was the driving forces to the development of MCM-D technology. Most of these development efforts have been focused on high performance digital circuits. However, recently there is a great need fur mixed mode circuits with a combination of digital, analog and microwave devices. Mixed mode modules often have a large number of passive components that are connected to a small number of active devices. Integration of passive components into the high density MCM substrate becomes desirable to further reduce cost, size, and weight of electronic systems while improving their performance and reliability. The proposed MCM-D substrate was based on Cu/photosensitive BCB multilayer and Ti/Cu is used to form the interconnect layer. Seed metal was formed with 1000 $\AA$ Ti/3000 $\AA$ Cu by sputtering method and main metal was formed with 3 $\mu\textrm{m}$ Cu by electrical plating method. The multi-turn sprial inductors were designed in coplanar fashion. This paper describe the manufacturing process of integrated inductors in MCM-D substrate and the results of electrical performance test.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1077-1082
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• 2007

This paper presents the analysis of the potential ultra-wideband(UWB) interference to WiMAX at 3.5 GHz bands and the mitigation method using transmit power control(TPC) of UWB system. UWB interference effect is evaluated with WiMax's outage probability over UWB density when multiple UWB systems and single WiMAX receiver distribute in unit area of 1$km^2$, When UWB distribution density is 20$devices/km^2$ and the dynamic range of TPC is 30 dB, UWB interference effect with TPC is decreased by 42 % rather than that without mitigation scheme. Finally, we describe that the proposed TPC is an effective method to mitigate UWB interference to WiMAX.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1523-1525
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• 2003

Due to the rapid development of wireless networking system, researches on the communication devices are mainly focus on microwave frequency devices such as filters, resonators, and phase shifters. Among them, Film bulk acoustic resonator (FBAR) has been paid extensive attentions for their high performance. In this research, ZnO thin films were deposited by RF-magnetron sputtering on Al/$SiO_2$/Si wafer and then crystalline properties and surface morphology were examined. To measure crystalline structure and surface morphology X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) were employed. It was showed that crystalline properties of ZnO thin films were strongly dependant on the deposition conditions. As increasing the deposition temperature and the deposition pressures, the peak intensities of ZnO(002) plane were increased until $300^{\circ}C$, then decreased rapidly. At the sputtering conditions of RF power of 213 W and working pressure of 15 m Torr, ZnO film had excellent c-axis orientation, surface morphology, and adhesion to the substrate. In conclusion we optimized smooth surface with very small grains as well as highly c-axis oriented ZnO film for FBAR applications.

• Composites Research
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• v.19 no.3
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• pp.1-6
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• 2006

As the structures of the high performance electronic equipments and devices recently become more complex, the electromagnetic interference (EMI) and compatibility (EMC) have been very essential for commercial and military purposes. Thus, sensitive electrical devices and densely packed systems need to be protected from electromagnetic wave. In this research, glass fabric/epoxy composites containing conductive multi-walled carbon nanotube (MWNT) and carbon fiber/epoxy composites as electrical shielding materials were fabricated and electrical properties of the composites were measured. The concerning frequency band is from 300 MHz to 1 GHz. The performances of composite shielding enclosures were predicted using electromagnetic wave 3-D simulation tool, CST Microwave Studio. The shielding enclosure made of carbon fiber/epoxy composites were fabricated and the shielding effectiveness (SE) was measured in the anechoic chamber.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.68.1-68.1
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• 2012

The best part of graphene is - charge-carriers in it are mass less particles which move in near relativistic speeds. Comparing to other materials, electrons in graphene travel much faster - at speeds of $10^8cm/s$. A graphene sheet is pure enough to ensure that electrons can travel a fair distance before colliding. Electronic devices few nanometers long that would be able to transmit charge at breath taking speeds for a fraction of power compared to present day CMOS transistors. Many researches try to check a possibility to make it a perfect replacement for silicon based devices. Graphene has shown high potential to be used as interconnects in the field of high frequency electrical devices. With all those advantages of graphene, we demonstrate characteristics of electrical and optical properties of graphene such as the effect of graphene geometry on the microwave properties using the measurements of S-parameter in range of 500 MHz - 40 GHz at room temperature condition. We confirm that impedance and resistance decrease with increasing the number of graphene layer and w/L ratio. This result shows proper geometry of graphene to be used as high frequency interconnects. This study also presents the optical properties of graphene oxide (GO), which were deposited in different substrate, or influenced by oxygen plasma, were confirmed using different characterization techniques. 4-6 layers of the polycrystalline GO layers, which were confirmed by High resolution transmission electron microscopy (HRTEM) and electron diffraction analysis, were shown short range order of crystallization by the substrate as well as interlayer effect with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups on its layers. X-ray photoelectron Spectroscopy (XPS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation, and Fourier Transform Infrared spectroscopy (FTIR) and XPS analysis shows the changes in oxygen functional groups with nature of substrate. Moreover, the photoluminescent (PL) peak emission wavelength varies with substrate and the broad energy level distribution produces excitation dependent PL emission in a broad wavelength ranging from 400 to 650 nm. The structural and optical properties of oxygen plasma treated GO films for possible optoelectronic applications were also investigated using various characterization techniques. HRTEM and electron diffraction analysis confirmed that the oxygen plasma treatment results short range order crystallization in GO films with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups. In addition, Electron energy loss spectroscopy (EELS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation and XPS analysis shows that epoxy pairs convert to more stable C=O and O-C=O groups with oxygen plasma treatment. The broad energy level distribution resulting from the broad size distribution of the $sp^2$ clusters produces excitation dependent PL emission in a broad wavelength range from 400 to 650 nm. Our results suggest that substrate influenced, or oxygen treatment GO has higher potential for future optoelectronic devices by its various optical properties and visible PL emission.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.3
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• pp.196-203
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• 2004

A three-dimensional (3D) IC technology platform is presented for high-performance, low-cost heterogeneous integration of silicon ICs. The platform uses dielectric adhesive bonding of fully-processed wafer-to-wafer aligned ICs, followed by a three-step thinning process and copper damascene patterning to form inter-wafer interconnects. Daisy-chain inter-wafer via test structures and compatibility of the process steps with 130 nm CMOS sal devices and circuits indicate the viability of the process flow. Such 3D integration with through-die vias enables high functionality in intelligent wireless terminals, as vertical integration of processor, large memory, image sensors and RF/microwave transceivers can be achieved with silicon-based ICs (Si CMOS and/or SiGe BiCMOS). Two examples of such capability are highlighted: memory-intensive Si CMOS digital processors with large L2 caches and SiGe BiCMOS pipelined A/D converters. A comparison of wafer-level 3D integration 'lith system-on-a-chip (SoC) and system-in-a-package (SiP) implementations is presented.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.5
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• pp.97-102
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• 2012

In this paper, each electrical length and harmonics of the multi-stage SIR are calculated by using the input impedance for the variable application of SIR in the microwave systems. The size reduced ratio of the SIR is slightly reduced as increasing of the number of stage. The impedance ratio between lower and higher impedance of the SIR has the dominant effect on the size reduced ratio and harmonic characteristics. Also the equivalent impedance of the SIR is a geometric mean between lower and higher impedance and the quality factor of the SIR is similar to the half-wavelength resonator's.