K.-W. Lee

Soongsil University, Sŏul, Seoul, South Korea

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Publications (16)8.28 Total impact

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    ABSTRACT: The hybridization of an individual plasmon in gold nanoparticle dimers was observed. By varying the interparticle separation within the metallic nanoparticle on a nanometer scale, we observed a renormalization, as well as a splitting, of the surface plasmon energy. The distinct hybridization and splitting of the individual plasmon mode were detectable in dimer plasmons when the edge-to-edge separation was smaller than ∼13 nm in gold particle pairs with a diameter of 160 nm, and a height of 40 nm for each particle. The range of the interparticle separation where the hybridization was detectable was sensitive to each particle's aspect ratio and size. An initial study of the ultrafast nonlinear optical response of exciton-plasmon coupled system is also reported. We observed an enhancement of the transient nonlinear transmission of Frenkel excitons in an organic semiconductor, cyanine J-aggregate, resonantly coupled with surface plasmons in gold metallic particle arrays.
    No preview · Article · Mar 2007 · Journal- Korean Physical Society
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    ABSTRACT: The stripping of the photoresist (PR) layer on a silicon wafer and transmittance enhancement of an indium-tin-oxide (ITO) film was investigated by irradiation with the line beam of a KrF excimer laser with a wavelength of 248 nm. A 0.82-μm-thick PR layer was removed perfectly at an energy density of 300 mJ/cm 2 after a 6-pulse irradiation with the line beam without the aid of any chemical or solvent. The ablation rates were 0.06 μm/pulse for 100 mJ/cm 2, 0.10 μm/pulse for 200 mJ/cm 2 and 0.13 μm/pulse for 300 mJ/cm 2. Many application fields require materials with optically smooth surfaces. A non-contact optical polishing method with a line beam technology is introduced and discussed for reducing the ITO surface roughness with angstrom (Å) precision without any pre- or post-treatment with chemicals. The transmission spectra of the ITO film before and after line beam irradiation showed an enhanced transmittance of over 8 % in the visible region (400 ∼ 800 nm). The effects of the excimer laser's fluence and the number of pulses applied to the ITO surface on reducing the surface roughness wore investigated. The root-mean-square (RMS) roughness of the ITO film was decreased by 30 ∼ 37 % compared to the initial laser-untreated ITO surface roughness. The main reason for the enhanced transmittance of the ITO film is the reduction of the ITO surface roughness, which reduces light scattering at the surface of the ITO. Non-contact laser technology has shown the ability to strip the PR without any pre- or post-chemical process and without any substrate damage.
    No preview · Article · Jul 2006 · Journal- Korean Physical Society
  • K.-W. Lee · Y.-Y. Kim
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    ABSTRACT: In this research, we used photoluminescence (PL) and photoluminescence excitation (PLE) to visualize the electronic band structure in porous silicon (PS). From the combined results of the PLE measurements at various PL emission energies and the PL measurements under excitation at various PLE absorption energies, we infer that three different electronic band structures, originating from different luminescent origins, give rise to the PL spectrum. Through either thermal activation or diffusive transfer, excited carriers are moved to each of the electronic band structures.
    No preview · Article · Oct 2004 · Journal- Korean Physical Society
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    ABSTRACT: A manufacturable Cu/low-k multilevel interconnects have been integrated using HSQ-via-fill dual damascene process for 65nm node as stated in K.-W. Lee et al. (2003). By introducing non-porous type SiOC film (k=2.7) without trench etch stopper and capping oxide, we obtained the effective k (keff) less than 3.0 for 65nm design rule. Simple and reliable process was achieved by improved unit process technologies such as damage-free capping oxide, abrasive free low-k direct polishing, advanced ionized PVD (AiPVD) barrier metal and bi-layer dielectric barriers, etc. according to K.C. Park et al. (2003).
    No preview · Conference Paper · Jul 2004
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    ABSTRACT: We present the effect of mechanical strength and residual stress of dielectric barrier on electromigration performance in Cu/low-k interconnects. It has been discovered that mechanical strength and residual stress of dielectric capping layer have a great role on EM performance. The use of mechanically strong dielectric capping material with high residual compressive stress in Cu/low-k interconnects improves a structural confinement of Cu line. Also, it helps tensile stress level decrease near via bottom and compressive stress level increase at Cu beneath SiCN along Cu line. Reduction of tensile stress at via bottom would effectively suppress void nucleation and growth. Moreover, increase of compressive stress in Cu beneath SiCN alleviates Cu migration through that pathway, leading to a longer lifetime of interconnect component.
    No preview · Conference Paper · Jan 2004
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    ABSTRACT: Integrating FSG dual damascene interconnects using MSQ-based sacrificial via filler has been previously shown. When applying such via filler to a Cu/low-k OSG integration, however, the requisite O<sub>2</sub>-ashing induces an inevitable damage to the low-k OSG due to the challenge in selectively eliminating such filler using conventional wet chemistry. By employing an inorganic HSQ that can readily be removed per dilute fluoric acid cleaning in low-k OSG structure, we demonstrated not only a more viable technology with lower defect density at each process step, e.g., photolithography and etching, but also a simpler process that selectively removes the filler material relative to the existing technology based on MSQ and/or organic fillers.
    No preview · Conference Paper · Jul 2003
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    ABSTRACT: Photoluminescent p-type porous silicon (PS), which showed a strong photoluminescence (PL) peak centered at about 720 nm, was annealed in vacuum. After the PS was annealed at about 550 °C, the PL completely quenched, and it was found that the average skeleton size of the PS layer became 50 ∼ 100 nm, which was 5 ∼ 10 times larger than that of PS before annealing. The Si 2p core level photoemission spectrum showed that the amount of oxide increased with annealing temperature. The increase in the average skeleton size, rather than a change in the oxide states, seemed to be the main cause of the observed irrecoverable PL degradation.
    No preview · Article · Jun 2003 · Journal- Korean Physical Society
  • Y.-Y. Kim · K.-W. Lee · C.-W. Lee · S. Hong · J.-W. Ryu · J.-H. Jeon
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    ABSTRACT: To enhance the photoluminescence intensity from porous silicon, we fabricated a porous silicon microcavity and investigated its photoluminescence resonance properties. The porous silicon microcavity was formed with a porous silicon active layer in the middle and sandwiched in between two multi-layered Bragg reflectors. We found that compared with a porous silicon single layer, the peak value of the emission intensity increased and the full width half maximum value of the photoluminescence resonance noticeably narrowed when a microcavity structure was used.
    No preview · Article · Feb 2003 · Journal- Korean Physical Society
  • KW Lee · JH Lee · HS Oh
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    ABSTRACT: As demand for the application in multimedia networks is increasing rapidly, it is important to provide multimedia services in Mobile Environments (ME). Obtaining to multimedia services which satisfy synchronization constraints in ME and improving the delay time and Quality of Service(QoS) between media streams to be presented, new specification model has to be proposed. In this paper we propose Mobile Petri-net Model(MPM) as a new specification model including the QoS parameter that minimizes the transmission delay time. The proposed model has higher the guarantee of QoS such as the loss rate and the playout rate than it of the previous work.
    No preview · Conference Paper · Jan 2003
  • YY Kim · K. W. Lee · E. J. Ahn · S. Shim
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    ABSTRACT: Photoluminescence spectra were measured experimentally and compared with the results of the optical model calculations in oder to identify the region of photoluminescence in a porous silicon layer. It is found that the upper surface region in the porous silicon layer contributes most of the luminescence, by analyzing the interference patterns of the photoluminescence spectra and those of reflectances. It is confirmed by comparing the results of a detailed computer simulation with the experiments, and by analyzing the photoluminescence characteristics of a free-standing porous silicon film. Analyses of the photoluminescence spectra measured using several different excitation wavelengths also support our conclusion.
    No preview · Article · Jan 2003 · Journal of Applied Physics
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    ABSTRACT: EM reliability has been improved with the advanced technology in 0.13μm node device integrated with FSG/SiOC hybrid low-k dual damascene process. The advanced technology includes advanced PVD Ta(N) process, SiCN deposition process, and longer NH3 plasma treatment. The advanced PVD Ta(N) process prevented void from generating by promoting deposition along sidewall of via bottom. SiCN film with moisture barrier property is supposed to block oxygen diffusion and Cu oxidation and to result in good adhesion with Cu. Longer NH3 plasma treatment improved adhesion between Cu and SiC and decreased stress at Cu/SiC interface. The EM lifetime of samples integrated with advanced processes is improved over 30 years.
    No preview · Article · Jan 2003
  • Source
    Joonghoe Dho · E.O Chi · N.H Hur · K.W Lee · H.S Oh · Y.N Choi
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    ABSTRACT: The magnetic and structural properties of a single crystal of Pr0.8Ca0.2MnO3 have been investigated by neutron powder diffraction and bulk magnetization as a function of temperature. Two ferromagnetic (FM) transitions near 140 and 70 K, which are ascribed to the ordering of Mn and Pr spins, respectively, are clearly evidenced by both measurements. The low temperature FM transition is largely dependent upon a strong exchange coupling between the localized Pr 4f and the neighboring itinerant Mn 3d spins. Near 140 K distinctive changes occur in lattice parameters, whereas no anomalous variation develops near 70 K.
    Full-text · Article · Aug 2002 · Solid State Communications
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    ABSTRACT: The changes of the structure and chemical states of photoluminescent p-type porous silicon (PS) caused by annealing in vacuum were investigated with atomic force microscopy and X-ray photoemission spectroscopy. The relative intensities of the silicon dioxide and suboxide peaks increased with the annealing temperature. The average size of the fine crystallites of the as-prepared samples was 5-10 nm and became 50-100 nm after being annealed at 550°C. The cause of photoluminescence quenching upon annealing is discussed.
    No preview · Article · Feb 2002 · Surface Review and Letters
  • W. S. Kim · H. S. Choi · B. C. Nam · E. O. Chi · K. W. Lee · N. H. Hur
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    ABSTRACT: Temperature and field dependent magnetic and transport measurements on a polycrystalline sample of Sr1.6La1.4Mn2O7 reveal distinct magnetic peaks above the ferromagnetic ordering temperature TC ≈ 90 K. The magnetic moment of the subsidiary phases identified as perovskitic impurities by a relation between the volume fraction and the corresponding magnetic moment does not couple with that of Sr1.6La1.4Mn2O7 in the high temperature range. This is evidenced by the presence of two slopes, dM/dH, in the M(H) curves and two different field dependences, H and H2, in the ρ(H) curves. On the other hand, a simple slope, dM/dH, in the low temperature regime hints at an exchange coupling between the magnetic moments of the two phases.
    No preview · Article · Jun 2001 · physica status solidi (a)
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    ABSTRACT: A novel partially-depleted silicon-on-insulator (PDSOI) CMOSFETs with SiGe-inserted layer have been proposed. The SiGe-inserted layer in NMOS successively suppresses the floating body effects (FBE) by lowering the body-to-source potential barrier to hole current. It also provides a good current performance in PMOS by inducing the change of channel dopant distribution and increasing the efficiency of pocket ion implantation. Consequently, SiGe-inserted SOI devices achieve higher drain-to-source breakdown voltage in NMOS due to the suppression of FBE and increase drive currents of both NMOS and PMOS by 10% and 15%, respectively, compared to conventional PDSOI devices
    No preview · Conference Paper · Feb 2000
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    ABSTRACT: Dielectric and mechanical characterization of organosilicon based PECVD a-SiOC:H low-k dielectric is presented. The film properties, such as refractive index, dielectric constant, elastic modulus, thermal stability are investigated as a function of 3 MS flow rate. A low-k a-SiOC:H film deposited with Z3MS™ and N2O gas has minimum k value of 2.7. The dielectric constant and the elastic modulus decrease with increase of 3 MS flow rate. The film with k value of 2.8 is tested as dielectric materials for Cu dual damascene process. The film has no PR tooting and shows high etch selectivity to a-SiC:H Cu diffusion barrier.
    No preview · Article · Jan 2000