• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.206.2-206.2
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• 2015

최근 비정질 산화물 반도체 thin film transistor(TFT)는 차세대 투명 디스플레이로 많은 관심을 받고 있으며 활발한 연구가 진행되고 있다. 산화물 반도체 TFT는 기존의 비정질 실리콘 반도체에 비하여 큰 on/off 전류비, 높은 이동도 그리고 낮은 구동전압으로 인하여 차세대 투명 디스플레이 산업에 적용 가능하다는 장점이 있다. 한편 기존의 sputter나 evaporator를 이용한 증착 방식은 우수한 막의 특성에도 불구하고 많은 시간과 제작비용이 든다는 단점을 가지고 있다. 따라서 본 연구에서는 별도의 고진공 시스템이 필요하지 않을 뿐만 아니라 대면적화에도 유리한 용액공정 방식을 이용하여 박막 트렌지스터를 제작하였으며 thermal 열처리와 microwave 열처리 방식에 따른 전기적 특성을 비교 및 분석하고 각 열처리 방식의 열처리 온도 및 조건을 최적화 하였다. 제작된 박막 트렌지스터는 p-type bulk silicon 위에 산화막이 100 nm 형성된 기판에 spin coater을 이용하여 Al-Zn-Sn-O 박막을 형성하였다. 연속해서 photolithography 공정과 BOE (30:1) 습식 식각 과정을 이용해 활성화 영역을 형성하여 소자를 제작하였다. 제작 된 소자는 Pseudo-MOS FET구조이며, 프로브 탐침을 증착 된 채널층 표면에 직접 접촉시켜 소스와 드레인 역할을 대체하여 동작시킬 수 있어 전기적 특성평가가 용이하다는 장점을 가지고 있다. 그 결과, microwave를 통해 열처리한 소자는 100oC 이하의 낮은 열처리 온도에도 불구하고 furnace를 이용하여 열처리한 소자와 비교하여 subthreshold swing(SS), Ion/off ratio, field-effectmobility 등이 개선되는 것을 확인하였다. 따라서, microwave 열처리 공정은 향후 저온 공정을 요구하는 MOSFET 제작 시의 훌륭한 대안으로 사용 될 것으로 기대된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.75-75
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• 2015

Strong interactions between electromagnetic radiation and electrons at metallic interfaces or in metallic nanostructures lead to resonant oscillations called surface plasmon resonance with fascinating properties: light confinement in subwavelength dimensions and enhancement of optical near fields, just to name a few [1,2]. By utilizing the properties enabled by geometry dependent localization of surface plasmons, metal photonics or plasmonics offers a promise of enabling novel photonic components and systems for integrated photonics or sensing applications [3-5]. The versatility of the nanoplasmonic platform is described in this talk on three folds: our findings on an enhanced ultracompact photodetector based on nanoridge plasmonics for photonic integrated circuit applications [3], a colorimetric sensing of miRNA based on a nanoplasmonic core-satellite assembly for label-free and on-chip sensing applications [4], and a controlled fabrication of plasmonic nanostructures on a flexible substrate based on a transfer printing process for ultra-sensitive and noise free flexible bio-sensing applications [5]. For integrated photonics, nanoplasmonics offers interesting opportunities providing the material and dimensional compatibility with ultra-small silicon electronics and the integrative functionality using hybrid photonic and electronic nanostructures. For sensing applications, remarkable changes in scattering colors stemming from a plasmonic coupling effect of gold nanoplasmonic particles have been utilized to demonstrate a detection of microRNAs at the femtomolar level with selectivity. As top-down or bottom-up fabrication of such nanoscale structures is limited to more conventional substrates, we have approached the controlled fabrication of highly ordered nanostructures using a transfer printing of pre-functionalized nanodisks on flexible substrates for more enabling applications of nanoplasmonics.

• Electrical & Electronic Materials
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• v.16 no.9
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• pp.63.1-63
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• 2003

Catalytic chemical vapor deposition (Cat-CVD) has been developed to deposit alumina(Al$_2$O$_3$) thin films on silicon (Si) crystal using N$_2$ bubbled tir-methyl aluminium [Al(CH$_3$)$_3$, TMA] and molecular oxygen (O$_2$) as source species and tungsten wires as a catalyzer. The catalyzer dissociated TMA at approximately 600$^{\circ}C$ The maximum deposition rate was 18 nm/min at a catalyzer temperature of 1000 and substrate temperature of 800$^{\circ}C$. Metal oxide semiconductor (MOS) diodes were fabricated using gates composed of 32.5-nm-thick alumina film deposited as a substrate temperature of 400oC. The capacitance measurements resulted in a relatively dielectric constant of 7, 4, fixed charge density of 1.74*10e12/$\textrm{cm}^2$, small hysteresis voltage of 0.12V, and very few interface trapping charge. The leakage current was 5.01*10e-7 A/$\textrm{cm}^2$ at a gate bias of 1V.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.9
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• pp.423-430
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• 2002

The fabrication and experimentation of multi-channel electrodes which enable detecting and recording of multi-site neuronal signals have been investigated. A multi-channel electrode array was fabricated by depositing 2000${\AA}$ thick Au layer on the 1000${\AA}$ thick Ti adhesion layer on a glass wafer. The metal paths were patterned by wet etching and passivated by depositing a PECVD silicon nitride insulation layer to prevent signals from intermixing or cross-talking. After placing a thin slice of rat cerebellar granule cell in the culture ring located in central portion of the multi-channel electrode plate, a neuronal signal from an electrode which is in contact with the cerebellar granule cell has been detected. It was found that the electrode impedance ranges 200㏀∼1㏁ and the impedance is not changed by cleaning with nitric acid. Also, the impedance is inversely proportion to the exposed electrode area and the cross-talk is negligible when the electrode spacing is bigger than 600$\mu\textrm{m}$. The amplitude and frequency of the measured action potential were 38㎷ and 2㎑, which are typical values. From the experimental results, the fabricated multi-channel electrode array proved to be suitable for multi-site neuronal signal detection for the analysis of a complicated cell network.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.923-932
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• 1998

Al2O3/Al composites were produced by displacement reaction method which was carried out by imm-ersing the sintered silica preform which was prepared form fused silica powder in molten aluminu. an ac-tivation energy of 94kJ/mole was calculated from Al-SiO2 reaction data in 1000-130$0^{\circ}C$ temperature range With increase of reaction temperature the alumina particle in the Al2O3/Al composites produced with pur metal Al showed grain growth and the growth of alumina particle in Al2O3/Al composite produced by using of Mg contained Al alloy was inhibited. The flexural strength of Al2O3/Al composites produced at 100$0^{\circ}C$ showed the highest value as 393 MPa. Flexural strength of the composite fabricated at 85$0^{\circ}C$ showed higher deviation than that of the composite produced at above 100$0^{\circ}C$ Low flexural strength of the composite fa-bricated at 120$0^{\circ}C$ due to the growth of pore and alumina particle size. The hardness of composites de-pended on alumina content in Al2O3/Al composite decreased with increasing of aluminium content in case the same alumina content and increased with increasing of silicon content in composite.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1228-1231
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• 2005

This paper reports about the development of scanning probe microscopy (SPM) tip with multi-walled carbon nanotube (MWNT). For making a carbon nanotube (CNT) modified tips, AC electric field which causes the dielectrophoresis was used for alignment and deposition of CNTs to the metal coated SPM tip. By dropping the MWNT solution and applying an electric field between an SPM tip and an electrode, MWNTs which were dispersed into a diluted solution were directly assembled onto the apex of the SPM tips due to the attraction by the dielectrophoretic force. In this paper, we investigate experimental conditions about the alignment of the CNT to tip axis according to the change of the angle between a tip and an electrode. Experimental results are presented, and then fabricated CNT tips are showed and measurement results for 15nm gold particles are compared with that of the conventional silicon tip.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.434-437
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• 2005

Chemical Mechanical Polishing (CMP) has become an essential step in the overall semiconductor wafer fabrication technology. In general, CMP is a surface planarization method in which a silicon wafer is rotated against a polishing pad in the presence of slurry under pressure. The polishing pad, generally a polyurethane-based material, consists of polymeric foam cell walls, which aid in removal of the reaction products at the wafer interface. It has been found that the material removal rate of any polishing pad decreases due to the so-called 'pad glazing' after several wafer lots have been processed. Therefore, the pad restoration and conditioning has become essential in CMP processes to keep the urethane polishing pad at the proper friction coefficient and to allow effective slurry transport to the wafer surface. Diamond pad conditioner employs a single layer of brazed bonded diamond crystals. Due to the corrosive nature of the polishing slurry required in low pH metal CMP such as copper, it is essential to minimize the possibility of chemical interaction between very low pH slurry (pH <2) and the bond alloy. In this paper, we report an exceptional protective coated conditioner for in-situ pad conditioning in low pH Cu CMP process. The protective Cr-coated conditioner has been tested in slurry with pH levels as low as 1.5 without bond degradation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.767-770
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• 2010

In this work, we investigated the static characteristics of 4H-SiC vertical metal-oxidesemiconductor field effect transistors (VMOSFETs) by adjusting the doping level of n-epilayer and the effect of a current spreading layer (CSL), which was inserted below the p-base region with highly doped n+ state ($5{\times}10^{17}cm^{-3}$). The structure of SiC VMOSFET was designed by using a 2-dimensional device simulator (ATLAS, Silvaco Inc.). By varying the n-epilayer doping concentration from $1{\times}10^{16}cm^{-3}$ to $1{\times}10^{17}cm^{-3}$, we investigated the static characteristics of SiC VMOSFETs such as blocking voltages and on-resistances. We found that CSL helps distribute the electron flow more uniformly, minimizing current crowding at the top of the drift region and reducing the drift layer resistance. For that reason, silicon carbide VMOSFET structures of highly intensified blocking voltages with good figures of merit can be achieved by adjusting CSL and doping level of n-epilayer.

• Transactions on Electrical and Electronic Materials
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• v.14 no.1
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• pp.32-35
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• 2013

In this paper, a manufacturing process was developed for fabricating high-quality AlGaN/GaN high electron mobility transistors (HEMTs) on silicon carbide (SiC) substrates. Various conditions and processing methods regarding the ohmic contact and pre-metal-deposition $BCl_3$ etching processes were evaluated in terms of the device performance. In order to obtain a good ohmic contact performance, we tested a Ti/Al/Ta/Au ohmic contact metallization scheme under different rapid thermal annealing (RTA) temperature and time. A $BCl_3$-based reactive-ion etching (RIE) method was performed before the ohmic metallization, since this approach was shown to produce a better ohmic contact compared to the as-fabricated HEMTs. A HEMT with a 0.5 ${\mu}m$ gate length was fabricated using this novel manufacturing process, which exhibits a maximum drain current density of 720 mA/mm and a peak transconductance of 235 mS/mm. The X-band output power density was 6.4 W/mm with a 53% power added efficiency (PAE).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.29-32
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• 2000

Cerium oxide thin film has been proposed as a buffer layer between the ferroelectric film and the Si substrate in Metal-Ferroelectric-Insulator-Silicon (MFIS ) structures for ferroelectric random access memory (FRAM) applications. In this study, CeO$_2$thin films were etched with Cl$_2$/Ar gas combination in an inductively coupled plasma (ICP). The highest etch rate of CeO$_2$film is 230 $\AA$/min at Cl$_2$/(Cl$_2$+Ar) gas mixing ratio of 0.2. This result confirms that CeO$_2$thin film is dominantly etched by Ar ions bombardment and is assisted by chemical reaction of Cl radicals. The selectivity of CeO$_2$to YMnO$_3$was 1.83. As a XPS analysis, the surface of etched CeO$_2$thin films was existed in Ce-Cl bond by chemical reaction between Ce and Cl. The results of XPS analysis were confirmed by SIMS analysis. The existence of Ce-Cl bonding was proven at 176.15 (a.m.u.).