• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.373-373
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• 2014

Resistive-change random access memory (ReRAM) device is one of the promising candidates owing to its simple structure, high scalability potential and low power operation. Many resistive switching devices using transition metal oxides materials such as NiO, Al2O3, ZnO, HfO2, $TiO_2$, have attracting increased attention in recent years as the next-generation nonvolatile memory. Among various transition metal oxides materials, HfO2 has been adopted as the gate dielectric in advanced Si devices. For this reason, it is advantageous to develop an HfO2-based ReRAM devices to leverage its compatibility with Si. However, the annealing temperature of these high-k thin films for a suitable resistive memory switching is high, so there are several reports for low temperature process including microwave irradiation. In this paper, we demonstrate the bipolar resistive switching characteristics in the microwave irradiation annealing processed Ag/HfO2/Pt ReRAM device. Compared to the as-deposited Ag/HfO2/Pt device, highly improved uniformity of resistance values and operating voltage were obtained from the micro wave annealing processed HfO2 ReRAM device. In addition, a stable DC endurance (>100 cycles) and a high data retention (>104 sec) were achieved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.85-88
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• 2003

$Sr_xBa_{1-x}Nb_2O_6$(SBN, $025{\leq}x{\leq}0.75$) ceramic is a ferroelectric material with tetragonal tungsten bronze (TTB) type structure, which has a high pyroelectric coefficient and a nonlinear electro-optic coefficient value. In spite of its advantages, SBN has not been investigated well compared to other ferroelectric materials with perovskite structure. In this study, SBN thin film was manufactured by ion beam sputtering technique using the prepared SBN target in Ar/$O_2$ atmosphere. SBN30 thin film of 500 ${\AA}$ was pre-deposited as a seed layer on Pt(l00)/$TiO_2$/$SiO_2$/Si substrate followed by SBN60 deposition up to 4500 ${\AA}$ in thickness. SBN60/SBN30 layer was deposited at different Oxygen amount of 0, 8.1, 17, and 31.8 sccm, respectively. The crystallinity and orientation behavior as well as electric properties of SBN60/SBN30 multi-layer were examined. The deposited layer was uniform and the orientation was shown primarily along (001) plane from XRD pattern. The crystal structure and the electric properties depended on the Oxygen amount, heating temperature and was the best at O2 = 8.1 seem, $750^{\circ}C$. In electric properties of Pt/SBN60/SBN30/Pt thin film capacitor prepared, the remnant polarization (2Pr) value was 13 ${\mu}C/cm^2$, the coercive field (Ec) 75 kV/cm, and the dielectric constant 1492, respectively.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.42-43
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• 2002

반도체 디바이스의 발전은 높은 직접화 및 동작 속도를 추구하고 있으며, 이를 위해서 MOSFET의 scale down시 발생되는 문제를 해결해야만 한다. 특히, Channel이 짧아짐으로써 발생하는 device의 열화현상으로 동작전압의 조절이 어려워 짐을 해결해야만 하며, gate oxide 두께를 줄임으로써 억제할 수 있다고 알려져 왔다. 현재, gate oxide으로 사용되고 있는 SiO2박막은 비정질로써 ～8.7 eV의 높은 band gap과 Si기판 위에서 성장이 용이하며 안정하다는 장점이 있으나, 두께가 1.6 nm 이하로 얇아질 경우 전자의 direct Tunneling에 의한 leakage current 증가와 gate impurity인 Boron의 channel로의 확산, 그리고 poly Si gate의 depletion effect[1,2] 등의 문제점으로 더 이상 사용할 수 없게 된다. 2001년 ITRS에 의하면 ASIC제품의 경우 2004년부터 0.9～l.4 nm 이하의 EOT가 요구된다고 발표하였다. 따라서, gate oxide의 물리적인 두께를 증가시켜 전자의 Tunneling을 억제하는 동시에 유전막에 걸리는 capacitance를 크게 할 수 있다는 측면에서 high-k 재료를 적용하기 위한 연구가 진행되고 있다[3]. High-k 재료로 가능성 있는 절연체들로는 A1₂O₃, Y₂O₃, CeO₂, Ta₂O, TiO₂, HfO₂, ZrO₂,STO 그리고 BST등이 있으며, 이들 재료 중 gate oxide에 적용하기 위해 크게 두 가지 측면에서 고려해야 하는데, 첫째, Si과 열역학적으로 안정하여 후속 열처리 공정에서 계면층 형성을 배제하여야 하며 둘째, 일반적으로 high-k 재료들은 유전상수에 반비례하는 band gap을 갖는 것으로 알려줘 있는데 이 Barrier Height에 지수적으로 의존하는 leakage current때문에 절연체의 band gap이 낮아서는 안 된다는 점이다. 최근 20이상의 유전상수와 ～5 eV 이상의 Band Gap을 가지며 Si기판과 열역학적으로 안정한 ZrO₂[4], HfiO₂[5]가 관심을 끌고 있다. HfO₂은 ～30의 고유전상수, ～5.7 eV의 높은 band gap, 실리콘 기판과의 열역학적 안전성 그리고 poly-Si와 호환성등의 장점으로 최근 많이 연구가 진행되고 있다. 또한, Hf은 SiO₂를 환원시켜 HfO₂가 될 수 있으며, 다른 silicide와 다르게 Hf silicide는 쉽게 산화될 수 있는 점이 보고되고 있다.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.222-225
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• 2001

The planar type inductors have a good potential for the application of miniaturized low power DC-DC converters. For those high quality application, the reduction of coil loss and also magnetic films which have good high frequency properties are required. Fabricated inductor was consisted of FeTaN/Ti magnetic film and electroplated Cu coil thickness of 100$\mu\textrm{m}$ and $SiO_2$ as a insulating layer. The inductor was designed double rectangular spiral shape for magnetic field highly confining within the device. The measured value of inductance and resistance were 980 nH and 1.7 $\Omega$ at 1 MHz as operating frequency of device. The Q factor is 3.55 at 1 MHz.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.2 s.17
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• pp.81-87
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• 2004

Semiconductor thick film gas sensors based on tin oxide are fabricated and their gas response characteristics are examined for four simulant gases of chemical warfare agent (CWA)s. The sensing materials are prepared in three different sets. 1) The Pt or Pd $(1,\;2,\;3\;wt.\%)$ as catalyst is impregnated in the base material of $SnO_2$ by impregnation method.2) $Al_2O_3\;(0,\;4,\;12,\;20\;wt.\%),\;In_2O_3\;(1,\;2,\;3\;wt.\%),\;WO_3\;(1,\;2,\;3\;wt.\%),\;TiO_2\;(3,\;5,\;10\;wt.\%)$ or $SiO_2\;(3,\;5,\;10\;wt.\%)$ is added to $SnO_2$ by physical ball milling process. 3) ZnO $(1,\;2,\;3,\;4,\;5\;wt.\%)$ or $ZrO_2\;(1,\;3,\;5\;wt.\%)$ is added to $SnO_2$ by co-precipitation method. Surface morphology, particle size, and specific surface area of fabricated sensing films are performed by the SEM, XRD and BET respectively. Response characteristics are examined for simulant gases with temperature in the range 200 to $400^{\circ}C$, with different gas concentrations. These sensors have high sensitivities more than $50\%$ at 500ppb concentration for test gases and also have shown good repetition tests. Four sensing materials are selected with good sensitivity and stability and are fabricated as a sensor array A sensor array Identities among the four simulant gases through the principal component analysis (PCA). High sensitivity is acquired by using the semiconductor thick film gas sensors and four CWA gases are classified by using a sensor array through PCA.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1861-1866
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• 2012

The new semiconducting copolymers with 4,4-dialkyl-$4H$-cyclopenta[2,1-$b$:3,4-$b^{\prime}$]dithiophene and 2,2-dimethyl-$2H$-benzimidazole units were synthesized. The fused aromatic rings, such as cyclopentadithiophene (CPDT) unit, can make the polymer backbone more rigid and coplanar, which induces long conjugation length, narrow band gap, and strong intermolecular ${\pi}-{\pi}$ interaction. The stacking ability was controlled through attaching of linear or branched alkyl side chains. The spectra of PEHCPDTMBI and PHCPDTMBI in the solid films show absorption bands with maximum peaks at 401, 759 and 407, 768 nm, and the absorption onsets at 925 and 954 nm, corresponding to band gaps of 1.34 and 1.30 eV, respectively. The devices comprising PHCPDTMBI with $TiO_X$ showed a $V_{OC}$ of 0.39 V, a $J_{SC}$ of 1.14 $mA/cm^2$, and a $FF$ of 0.34, giving a power conversion efficiency of 0.15%. The PHCPDTMBI with linear alkyl chain on CPDT shows good solubility in organic solvent with higher PCE value than that of PEHCPDTMBI.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.111-115
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• 2003

200nm 정도의 두께를 가진 SBT 박막이 liquid delivery MOCVD 공정에 의해 (111) oriented Pt/Ti/$SiO_2$/Si 기판 위에 증착되었다 이 실험에서는 $Sr(TMHD)_2$tetraglyme, $Bi(ph)_3$ 그리고 $Ta(O^iPr)_4$(TMHD)를 출발 물질로 사용하였다. Sr 출발 물질의 열적 안정화를 위해서 adduct로 tetraglyme를 사용하여 실험하였고 유기 용매로는 n-butyl acetate를 사용하였다 Substrate temperature와 reactor pressure는 각각 $570^{\circ}C$와 5Torr로 유지시켰다. 또한 vaporizer의 용도는 $190-200^{\circ}C$, 그리고 delivery line 의 온도는 vaporizer 보다 높게 유지 $(220-230^{\circ}C)$하여 출발 용액을 분당 0.1ml로 50분간 주입하였다. 수송가스로 Ar, 산화제로 $O_2$ 가스를 사용하였다. 제조한 SBT 박막은 $750^{\circ}C$에서 열처리한 후 인가전압 3V와 5V에서 $2P_r$값이 각각 6.47, $8.98{\mu}C/cm^2$이었으며, $2E_c$값은 인가전압 3V와 5V에서 각각 2.05, 2.31V이었다 그리고 $800^{\circ}C$에서는$750^{\circ}C$에서 열처리한 SBT 박막보다 다소 우수한 이력특성을 나타내어 $2P_r$ 값은 인가전압 3V와 5V에서 각각 7.59, $10.18{\mu}C/cm^2$ 이었으며, $2E_c$값은 인가 전압 3V와 5V에서 각각 2.00, 2.21V 이었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.76.2-76.2
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• 2013

Advanced electronic application areas have strongly required new materials due to the continuous shrinking dimensions of their devices. Specially, the development and use of metal precursors for atomic layer deposition has been extensively focused on application to electronic devices. Thus the systematic design and synthesis of metal compounds with relevant chemical and physical properties, such as stability, volatility, and resistance to air and moisture are very important in the vacuum deposition fields. In many case, organic ligands for metal precursors are especially focused in the related research areas because the large scale synthesis of the metal complexes with excellent properties exclusively depends on the potential usefulness of the ligands. It is recommended for metal complexes to be in monomeric forms because mononuclear complexes generally show high vapor pressures comparing with their oligomeric structure such as dimer and trimer. Simple metal alkoxides complexes are involatile except several examples such as Ti(OiPr)4, Si(OEt)4, and Hf(OtBu)4. Thus the coordinated atom of alkoxide ligands should be crowded in its own environment with some substituents by prohibiting the coordinated atoms from bonding to another metal through oxygen-bridging configuration. Alkoxide ligands containing donor-functionalized group such as amino and alkoxy which can induce the increasing of the coordinative saturation of the metal complexes and the decreasing of the intermolecular interaction between or among the metal compounds. In this presentation, we will discuss the development of metal compounds which adopted donor-functionalized alkoxide ligands derived from their alcohols for electronic application. Some recent results on ALD using metal precursors such as tin, nickel, ruthenium, and tungsten developed in our group will be disclosed.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.74-79
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• 2009

Titanium and titanium alloy can be reproduced immediately even if oxide films($TiO_2$) break apart in sea water. Therefore, since titanium demonstrates large specific strength and outstanding resistance to stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion in sea water environment, it has been widely applied to heat exchanger for ships. In particular, with excellent elongation, pure titanium may be deemed as optimal material for production of heat exchanger plate which is used with wrinkles formed for efficient heat exchange. Conventional plate type heat exchanger prevented leakage of liquid through insertion of gasket between plates and mechanical tightening by bolts and nuts, but in high temperature and high pressure environment, gasket deterioration and leakage occur, so heat exchanger for LPG re-liquefaction device etc do not use gasket but weld heat exchanger plate for use. On the other hand, since welded plate cannot be separated, it is important to obtain high quality reliable welds. In addition, for better workability and production performance, lasers that can obtain weldment with large aspect ratio and demonstrate fast welding speed even in atmospheric condition not in vacuum condition are used in producing products. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through quantitative analysis of oxygen and nitrogen and measurement of hardness as fundamental experiment for the evaluation of titanium laser welding, and evaluated the welding performance and mechanical properties of butt welding. This study welded specimens in various conditions by using laser and GTA welding machine to apply edge welding to heat exchanger, and evaluated the mechanical strength through tensile stress test. As a result of tensile test, laser weldment demonstrated tensile strength 4 times higher than GTA welds, and porosity could be controlled by increasing and decreasing slope of laser power at overlap area.

• Korean Journal of Materials Research
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• v.7 no.6
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• pp.505-509
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• 1997

FRAM(Ferroelectric Random Access memory)에의 응용을 위해 rf magnetron sputtering법을 이용하여 SrB $i_{2}$T $a_{2}$ $O_{9}$(SBT)박막을 증착하였다. 사용된 기판은 Pt/Ti/Si $o_{2}$Si이었으며 50$0^{\circ}C$에서 증착한 후 80$0^{\circ}C$의 산소 분위기 하에서 1시간 동안 열처리하였다. 증착시 증착 압력을 변화시켜 가면서 이에 따른 특성의 변화를 고찰하였다. 박막내의 Bi와 Sr의 부족을 보상하기 위해 20mole%의 Bi $O_{2}$와 30mole%의 SrC $O_{3}$를 과잉으로 넣어 타겟을 제조후 사용하였고 박막들의 두께는 300nm의 두께를 가지며 증착압력에 따라 다른 미세 구조르 보였다. 10mtorr에서 증착한 박막의 조성은 S $r_{0.6}$B $i_{3.8}$Ta/ sub 2.0/ $O_{9.0}$이었다. 이 SBT 박막의 잔류 분극(2 $P_{r}$)과 보전계(2 $E_{c}$)값은 각각 인가 전압 5V에서 18.5 $\mu%C/$\textrm{cm}^2$과 150kV/cm이었고, signal/noise비는 3V에서 4.6을 나타내었다. 5V의 bipolar pulse하에서 $10^{10}$cycle까지 피로 현상이 나타나지 않았으며, 누설 전류 밀도는 133kV/cm에서 약 1x$10^{-7A}$$\textrm{cm}^2$의 값을 보였다.을 보였다.