• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.385.1-385.1
• /
• 2014

$Bi_2Te_3$는 전기적, 열적 특성 등이 아주 흥미로운 소재로, 열전소자 응용 및 위상절연체(Topologycal insulator: TI)로써의 연구가 활발히 진행되고 있는 소재이다. 한편, 전기적, 광학적, 기계적, 열적 특성들이 매우 뛰어나 신소재로 각광받고 있는 그래핀은 나노소재의 합성 분야에서도 기판으로 활용되어, 최근에는 그래핀을 기판으로 한 고품질 나노소재의 합성에 관한 연구보고가 증가하고 있다. 이에, 본 연구에서는 그래핀을 $SiO_2$에 전사한 기판 및 $SiO_2$ 기판 위에 $Bi_2Te_3$ 나노 구조를 합성하고 다양한 분석을 하였다. 라만 스펙트럼 및 XRD를 통해 $Bi_2Te_3$ 임을 확인하였고, 비정질 $SiO_2$기판과 결정질 그래핀/$SiO_2$기판 그리고 구리호일과 그래핀/구리 호일 위에서 합성된 $Bi_2Te_3$ 나노구조를 SEM 및 TEM을 이용하여 비교 분석 하였다. 또한 기초적인 전기물성을 평가하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.176.2-176.2
• /
• 2014

In this work, we demonstrated that the fabrication of flexible graphene-based chemical sensor with heaters by soft lithographic patterning method [1]. First, monolayer and multilayer graphene were prepared by thermal chemical vapor deposition transferred onto SiO2 / Si substrate in order to fabrication of patterned-sensor and -heater. Second, patterned-monolayer and multilayer graphene were detached through soft lithography process, which was transferred on top and bottom sides of PET film. Third, Au / Ti (Thickness : 100/30 nm) electrodes were deposited end of the patterned-graphene line by sputtering system. Finally, we measured sensor properties through injection of NO2 and CO2 gas on different temperature with voltage change of graphene heater.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.292-292
• /
• 2014

Wide band gap semiconductors, such as III-nitrides (GaN, AlN, InN, and their alloys), SiC, and diamond are expected to play an important role in the next-generation electronic devices. Specifically, GaN-based high electron mobility transistors (HEMTs) have been targeted for high power, high frequency, and high temperature operation electronic devices for mobile communication systems, radars, and power electronics because of their high critical breakdown fields, high saturation velocities, and high thermal conductivities. For the stable operation, high power, high frequency and high breakdown voltage and high current density, the fabrication methods have to be optimized with considerable attention. In this study, low ohmic contact resistance and smooth surface morphology to AlGaN/GaN on 2 inch c-plane sapphire substrate has been obtained with stepwise annealing at three different temperatures. The metallization was performed under deposition of a composite metal layer of Ti/Al/Ni/Au with thickness. After multi-layer metal stacking, rapid thermal annealing (RTA) process was applied with stepwise annealing temperature program profile. As results, we obtained a minimum specific contact resistance of $1.6{\times}10^{-7}{\Omega}cm2$.

• Transactions on Electrical and Electronic Materials
• /
• v.6 no.1
• /
• pp.10-13
• /
• 2005

$Sr_{0.6}Ba_{0.4}Nb_{2}O_{6}$, hereafter SBN60, thin films of 300 nm thickness were deposited using ion beam sputtering technique, in which sintered ceramic target of the same composition was utilized and the $Ar:O_{2}$ gas ratio was controlled during deposition onto $Pt(100)/TiO_{2}/SiO_{2}/Si$ substrate. Crystallization and orientation behavior as well as electrical properties of the films were examined after annealing treatment at $650{\sim}800{\cric}C$. It was found that the film orientation was dependent upon $Ar:O_{2}$ratio, in which strong (00l) orientation was developed when the gas ratio was about 1:4 at $4.3{\times}10^{-4}$ torr. Typical remanent polarization (2Pr), the coercive field (Ec) and the dielectric constant of Pt/SBN60/Pt thin film capacitor were approximately $10{\mu}C/cm^{2}$, 60 kV/cm, and 615, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.99-100
• /
• 2005

We have grown carbon nanotubes (CNTs) with a microwave plasma chemical vapor deposition (MPECVD) method, which has been regard as one of the most promising candidates for the synthesis of CNTs due to the vertical alignment, the low temperature and the large area growth. We use methane ($CH_4$) and hydrogen ($H_2$) gas for the growth of CNTs. 60 nm thick Ni catalytic layer were deposited on the TiN coated glass substrate by RF magnetron sputtering method. In this work, we report the effects of pressure on the growth of CNTs. We have changed pressure of processing (10 $\sim$ 20 Torr) deposition of CNTs. SEM (Scanning electron microscopy) images show diameter, length and cross section state CNTs.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.848-850
• /
• 1999

In this study, PZT etching was performed using planar inductively coupled Ar(20)/$Cl_2/BCl_3$ plasma, The etch rate of PZT film was 2450 $\AA/min$ at Ar(20)/$BCl_3$(80) gas mixing ratio and substrate temperature of $80^{\circ}C$. X-ray photoelectron spectroscopy (XPS) analysis for film composition was utilized. The chemical bond of PbO is broken by ion bombardment, and the peak of metal Pb in a Pb 4f peak begins to appear upon etching, decreasing Pb content faster than Zr and Ti. As increase content of additive $BCl_3$, the relative content of oxygen decreases rapidly. We thought that abundant Band BCl radicals made volatile oxy-compound such as $B_{x}O_{y}$ and/or $BClO_x$ bond. To understand etching mechanism, Langmuir probe and optical emission spectroscopy (OES) analysis were utilized for plasma diagnostic.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.918-920
• /
• 1999

Recently, the ceramics of high permittivity are applied to DRAM and FRAM. In this study, (Ba, Sr)$TiO_3$ (BST) ceramics thin films were prepared by Sol-Gel method. BST solution was made and spin-coated on Pt/$SiO_2$/Si substrate at 4000[rpm] for 10 seconds. Coating process was repeated 3 times and then sintered at $750[^{\circ}C]$ for 30 minutes. Each specimen was analyzed structure and electrical characteristics. Thickness of BST ceramics thin films are about $2000[\AA]$. Dielectric constant and loss of thin films was little decreased at $1[kHz]{\sim}1[MHz]$. Dielectric constant and loss to frequency were 250 and 0.02 in BST3. In accordance with applied voltage, property of leakage current was stability when the was $0{\sim}3$[V]. According to voltage, leakage current was increased exponentially at $4{\sim}7$[V].

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2017.05a
• /
• pp.70-70
• /
• 2017

TSV(through silicon via)는 긴 종횡비를 갖는 패턴에 Cu, Ta, Ti을 높은 conformality를 갖도록 증착하는 공정이다. Magnetron cathode의 자석 배열 설계는 target 물질 종류에 따라서 multitrack, water drop type등이 있으며 target과 substrate 사이의 공간에 플라즈마를 형성시켜서 기판에 이온 입사량을 늘린 후 기판 바이어스를 이용하여 이온 충돌, re-sputtering을 통한 재증착 과정을 통해 치밀한 금속 박막을 연속적으로 형성할 수 있도록 하는 것이 목적이다. 또한 sputter가 사용되고 있는 분야에 효율을 증대시키고, 증착되는 막의 품질향상을 위해 UBMS를 사용하고 있으며, 산업에 사용되어 지는 300 mm wafer용 시스템은 제작비가 약 10억 원 정도 소요되며 다양한 테스트를 진행하기 위해선 많은 비용이 소요된다. 따라서 비용과 소요시간을 줄여 다양한 테스트를 위해 소규모 플라즈마 시스템을 설계하게 되었다. 61 l/sec 터보 분자 펌프와 다이아프램 펌프를 기초로한 TMP station에 2.75 인치 CF flange가 장착된 6 way cross를 main 챔버로 활용하고, 작은 size의 unbalanced magnetron cathode를 제작, 장착한 다음 6 way cross 주변에 전자석을 적절히 배치하여 300 mm wafer system에서와 동일한 물리적 현상을 테스트 할 수 있도록 하였다. Fig1. (a) UBMS system의 사진을 나타내었고, (b)에는 6 way cross 내부에 발생된 플라즈마의 형상을 나타내었다. 전원 장치는 Advanced Energy사의 MDX-1.5K DC power supply를 사용하였고, 방전 전압 - 전류 관계의 가스 압력에 따른 plasma 현상과 magnetron 배율에 따른 plasma 현상 그리고 전자석에 의한 영향을 주로 관찰 하였다.

• Progress in Superconductivity
• /
• v.1 no.1
• /
• pp.20-25
• /
• 1999

We constructed a high-$T_c$ scanning SQUID microscope (SSM) operating in the liquid nitrogen. We used a washer-type YBCO SQUID with inner and outer dimensions of $12{\mu}m$ and $36{\mu}m$, respectively, which was grown on the $SrTiO^3$ bicrystal substrate. The sample, rather than SQUID, was scanned using two stepping motors. We also developed readout electronics, stepping motor controller, and the software for system control and data display. We took images of various samples using our SSM and found that the spatial resolution is about $40{\mu}m$ and noise level is lower than $10^{-7}T/{\surd}Hz$ at 100 Hz and higher at lower frequencies. The noise level was much higher than that of a typical SQUID due to the other coupling from the electric parts. We present a simple argument on the inductive coupling between the sample and the SQUID which should be under-stood for the proper interpretation of the obtained images. By comparing the measured data with the simulation results the gap between the SQUID and the sample is estimated to be $40{\mu}m$.

• 한국금형공학회:학술대회논문집
• /
• 2008.06a
• /
• pp.35-38
• /
• 2008

A pattern master and a Ni stamper for 50nm class of patterns are fabricated through e-beam lithography and Ni electroforming process. A model pattern set is designed, which is based on unit patterns of 50nm, 100nm, 150nm and 200nm in length and 50nm in width. The e-beam process is optimized to fabricate designed patterns with some parameters including dose, accelerating voltage, focal distance and developing time. For Ni electroforming to fabricate Ni stamper, a seed layer, a conducting layer, is deposited first on the pattern master fabricated by an e-beam lithography process. Ni, Ti/Ni and Cr are first tested to find optimal seed layer process. Currently the best result is obtained when adopting Cr deposited to be 100nm thick with continuous tilting motion of the master substrate during the deposition process.