• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.319-319
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• 2013

Even though the fabrication methods of metal oxide based thin film capacitor have been well established such as RF sputtering, Sol-gel, metal organic chemical vapor deposition (MOCVD), ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD), an applicable capacitor of printed circuit board (PCB) has not realized yet by these methods. Barium Strontium Titanate (BST) and other high-k ceramic oxides are important materials used in integrated passive devices, multi-chip modules (MCM), high-density interconnect, and chip-scale packaging. Thin film multi-layer technology is strongly demanded for having high capacitance (120 nF/$mm^2$). In this study, we suggest novel multi-layer thin film capacitor design and fabrication technology utilized by plasma assisted deposition and photolithography processes. Ba0.6Sr0.4TiO3 (BST) was used for the dielectric material since it has high dielectric constant and low dielectric loss. 5-layered BST and Pt thin films with multi-layer sandwich structures were formed on Pt/Ti/$SiO_2$/Si substrate by RF-magnetron sputtering and DC-sputtering. Pt electrodes and BST layers were patterned to reveal internal electrodes by photolithography. SiO2 passivation layer was deposited by plasma-enhanced chemical vapor deposition (PE-CVD). The passivation layer plays an important role to prevent short connection between the electrodes. It was patterned to create holes for the connection between internal electrodes and external electrodes by reactive-ion etching (RIE). External contact pads were formed by Pt electrodes. The microstructure and dielectric characteristics of the capacitors were investigated by scanning electron microscopy (SEM) and impedance analyzer, respectively. In conclusion, the 0402 sized thin film multi-layer capacitors have been demonstrated, which have capacitance of 10 nF. They are expected to be used for decoupling purpose and have been fabricated with high yield.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.100-100
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• 2000

Aluminium oxide (Al2O3) films have been investigated for many applications such as insulating materials, hard coatings, and diffusion barriers due to their attractive electrical and mechanical properties. In recent years, application of Al2O3 films for dielectric materials in integrated circuits as gates and capacitors has attracted much attention. Various deposition techniques such as sol-gel, metalorganic decomposition (MOD), sputtering, evaporation, metalorganic chemical vapor deposition (MOCVD), and pulsed laser ablation have been used to fabricate Al2O3 thin films. Among these techniques, reactive sputtering has been widely used due to its high deposition rate and easy control of film composition. It has been also reported that the sputtered Al2O3 films exhibit superior chemical stability and mechanical strength compared to the films fabricated by other processes. In this study, Al2O3 thin films were deposited on Pt/Ti/SiO/Si2 and Si substrates by DC reactive sputtering at room temperature with variation of the Ar/O2 ratio in sputtering ambient. Crystalline phase of the reactively sputtered films was characterized using X-ray diffractometry and the surface morphology of the films was observed with Scanning election microscopy. Effects of Th Ar/O2 ratio characteristics of Al2O3 films were investigated with emphasis on the thickness dependence of the dielectric properties. Correlation between the dielectric properties and the microstructure was also studied

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.211-211
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• 1999

Titanium nitride (TiN) thin films have useful properties including high hardness, good electrical conductivity, high melting point, and chemical inertness. The applications have included wear-resistant hard coatings on machine tools and bearings, decorative coating making use of the golden color, thermal control coatings for widows, and erosion resistant coatings for spacecraft plasma probes. For all these applications as feature sizes shrink and aspect ratios grow, the issue of good step coverage becomes increasingly important. It is therefore essential to manufacture conformal coatings of TiN. The growth of TiN thin films by chemical vapor deposition (CVD) is of great interest for achieving conformal deposition. The most widely used precursor for TiN is TiCl4 and NH3. However, chlorine impurity in the as-grown films and relatively high deposition temperature (>$600^{\circ}C$) are considered major drawbacks from actual device fabrication. To overcome these problems, recently, MOCVD processes including plasma assisted have been suggested. In this study, therefore, we have doposited Ti(C, N) thin films on Si(100) and D2 steel substrates in the temperature range of 150-30$0^{\circ}C$ using tetrakis diethylamido titanium (TDEAT) and titanium isopropoxide (TIP) by pulsed DC plamsa enhanced metal-organic chemical vapor deposition (PEMOCVD) method. Polycrystalline Ti(C, N) thin films were successfully grown on either D2 steel or Si(100) surfaces at temperature as low as 15$0^{\circ}C$. Compositions of the as-grown films were determined with XPS and RBS. From XPS analysis, thin films of Ti(C, N) with low oxygen concentration were obtained. RBS data were also confirmed the changes of stoichiometry and microhardness of our films. Radical formation and ionization behaviors in plasma are analyzed by optical emission spectroscopy (OES) at various pulsed bias and gases conditions. H2 and He+H2 gases are used as carrier gases to compare plasma parameter and the effect of N2 and NH3 gases as reactive gas is also evaluated in reduction of C content of the films. In this study, we fond that He and H2 mixture gas is very effective in enhancing ionization of radicals, especially N resulting is high hardness. The higher hardness of film is obtained to be ca. 1700 HK 0.01 but it depends on gas species and bias voltage. The proper process is evident for H and N2 gas atmosphere and bias voltage of 600V. However, NH3 gas highly reduces formation of CN radical, thereby decreasing C content of Ti(C, N) thin films in a great deal. Compared to PVD TiN films, the Ti(C, N) film grown by PEMOCVD has very good conformability; the step coverage exceeds 85% with an aspect ratio of more than 3.

• Progress in Superconductivity and Cryogenics
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• v.14 no.4
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• pp.5-11
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• 2012

In this review article, we focus on various co-evaporation technologies developed for the fabrication of high performance $REBa_2Cu_3O_{7-{\delta}}$ (RE: Y and Rare earth elements, REBCO) superconducting films. Compared with other manufacturing technologies for REBCO films such as sputtering, pulsed laser deposition (PLD), metal-organic deposition (MOD), and metal organic chemical vapor deposition (MOCVD), the co-evaporation method has a strong advantage of higher deposition rate because metal sources can be used as precursor materials. After the first attempt to produce REBCO films by the co-evaporation method in 1987, various co-evaporation technologies for high performance REBCO films have been developed during last several decades. The key points of each co-evaporation technology are reviewed in this article, which enables us to have a good insight into a new high throughput process, called as a Reactive Co-Evaporation by Deposition and Reaction (RCE-DR).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.222-222
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• 2011

Titanium dioxide (TiO2) has a number of applications in optics and electronics due to its superior properties, such as physical and chemical stability, high refractive index, good transmission in vis and NIR regions, and high dielectric constant. Atomic layer deposition (ALD), also called atomic layer epitaxy, can be regarded as a special modification of the chemical vapor deposition method. ALD is a pulsed method in which the reactant vapors are alternately supplied onto the substrate. During each pulse, the precursors chemisorb or react with the surface groups. When the process conditions are suitably chosen, the film growth proceeds by alternate saturative surface reactions and is thus self-limiting. This makes it possible to cover even complex shaped objects with a uniform film. It is also possible to control the film thickness accurately simply by controlling the number of pulsing cycles repeated. We have investigated the ALD of TiO2 at 100$^{\circ}C$ using precursors titanium tetra-isopropoxide (TTIP) and H2O on -O, -OH terminated Si surface by in situ X-ray photoemission spectroscopy. ALD reactions with TTIP were performed on the H2O-dosed Si substrate at 100$^{\circ}C$, where one cycle was completed. The number of ALD cycles was increased by repeated deposition of H2O and TTIP at 100$^{\circ}C$. After precursor exposure, the samples were transferred under vacuum from the reaction chamber to the UHV chamber at room temperature for in situ XPS analysis. The XPS instrument included a hemispherical analyzer (ALPHA 110) and a monochromatic X-ray source generated by exciting Al K${\alpha}$ radiation (h${\nu}$=1486.6 eV).

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.254-254
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• 2016

Tin dioxide (SnO2) thin film is one of the most important n-type semiconducting materials having a high transparency and chemical stability. Due to their favorable properties, it has been widely used as a base materials in the transparent conducting substrates, gas sensors, and other various electronic applications. Up to now, SnO2 thin film has been extensively studied by a various deposition techniques such as RF magnetron sputtering, sol-gel process, a solution process, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and atomic layer deposition (ALD) [1-6]. Among them, ALD or plasma-enhanced ALD (PEALD) has recently been focused in diverse applications due to its inherent capability for nanotechnologies. SnO2 thin films can be prepared by ALD or PEALD using halide precursors or using various metal-organic (MO) precursors. In the literature, there are many reports on the ALD and PEALD processes for depositing SnO2 thin films using MO precursors [7-8]. However, only ALD-SnO2 processes has been reported for halide precursors and PEALD-SnO2 process has not been reported yet. Herein, therefore, we report the first PEALD process of SnO2 thin films using SnCl4 and oxygen plasma. In this work, the growth kinetics of PEALD-SnO2 as well as their physical and chemical properties were systemically investigated. Moreover, some promising applications of this process will be shown at the end of presentation.

• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.378-383
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• 2007

A novel fabrication method for the multi-component metal oxides such as zirconium titanate($Zr_xTi_{1-x}O_2$) has been suggested, which would yield the uniform film characteristics and control the film composition at relatively low process temperature. The method has the basic concept that firstly layer-by-layer structure is constructed with the primitive oxide layers, which are components of the desired multi-component oxides, and secondly the film is annealed at appropriate thermal conditions for the transformation to a single-phase multi-component oxides. In this study, PRTMOCVD(pulsed rapid thermal metalorganic chemical vapor deposition) possessing the superior thickness controllability was introduced to prepare $ZrO_2$ and $TiO_2$ thin film for zirconium titanate. Single-phase zirconium titanate thin films have been prepared successfully by the interdiffusion of oxide multilayers having several alternating layers of $ZrO_2$ and $TiO_2$. The Zr/Ti ratio of zirconium titanate could be controlled easily by altering the thickness of $ZrO_2$ and $TiO_2$ thin film.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.86-91
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• 1999

We have fabricated high-$\textrm{T}_c$ superconducting $\textrm{YBa}_{2}\textrm{Cu}_{3}\textrm{O}_{7-x}$(YBCO) grain boundary junctions at a step-edge on (001) $\textrm{SrTiO}_3$(STO) substrates. A diamond-like carbon (DLC) film grown by plasma enhanced chemical vapor deposition were used as an ion milling mask to make steps on the STO (100) single crystal and was removed by an oxygen reactive ion etch process. The c-axis oriented YBCO and TO thin films were deposited epitaxially on the STO substrate with a step-edge by pulsed laser deposition. The grain boundary junctions were formed at the top and the bottom of the step. The junctions worked at temperatures above 77 K, and had I\ulcornerR\ulcorner products of 7.5mV at 16K and 0.3 mV at 77K, respectively. The I-V characteristics of these junctions showed the shape of the two noisy resistively shunted junction model.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.259-259
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• 2011

염료감응형 태양전지(Dye-Sensitized Solar Cells:DSSC)는 환경 친화적이며, 저가의 공정에 대한 가능성으로 기존의 고가의 결정질 실리콘 태양전지의 경제적인 대안으로 각광을 받고 있다. 최근 염료감응형 태양전지는 투명 전도성 산화막(Transparent Conducting Oxide : TCO)으로 사용되는 Fluorine Tin Oxide (FTO)가 증착된 유리기판 위에 주로 제작된다. FTO는 낮은 비저항과 가시광선 영역에서 높은 투과도를 가지는 우수한 전기-광학적 특성을 갖지만, 비교적 공정이 까다로운 Chemical Vapor Deposition (CVD)법으로 제조하며, 전체 공정비용의 60%를 차지하는 높은 생산단가로 인해 현재 FTO를 대체할 재료개발 연구가 활발히 진행되고 있다. 그 중 ZnO (Zinc Oxide)는 우수한 전기-광학적 특성과 비교적 저렴한 가격으로 새로운 TCO로써 주목받고 있다. ZnO는 넓은 energy band gap (3.4 [eV])의 육방정계 울자이트(hexagonal wurtzite) 결정 구조를 가지는II-VI족 n형 반도체 물질이며, III족 금속원소인 Al, Ga 및 In 등의 불순물을 첨가하면 TCO로서 우수한 전기-광학적 특성과 안정성을 나타낸다. 이들 물질중 $Zn^{2+}$ (0.060 nm)의 이온반경과 유사한 $Ga^{2+}$0.062 nm) 이온이 ZnO의 격자반경을 최소화 시킬 수 있다는 장점으로 최근 주목 받고 있다. 하지만 Ga-doped ZnO (GZO)의 경우 DSC에 사용되는 루테늄 계열의 산성 염료 하에 장시간 두면 표면이 파괴되는 문제가 발생하며, $TiO_2$ paste를 Printing 후 열처리하는 과정에서도 박막의 파괴가 발생할 수 있다. 이를 방지하기 위해 $TiO_2$ Blocking Layer를 GZO 투명전극 위에 증착하였다. 또한, $TiO_2$ Blocking Layer를 적용한 GZO 박막을 전면전극으로 이용하여 DSC를 제작하여 효율을 확인하였다. 2wt%의 $Ga_2O_3$가 도핑된 ZnO 박막은 20mTorr 400$^{\circ}C$에서 Pulsed Laser Deposition (PLD)에 의해 성장되었고, $TiO_2$박막은 Ti 금속을 타겟으로 이용하여 30mTorr 400$^{\circ}C$에서 증착되었다. Scanning electron microscopy (FE-SEM)을 이용한 박막 분석 결과 $TiO_2$가 증착된 GZO 박막의 경우 표면 파괴가 일어나지 않았다. Solar Simulator을 이용하여 I-V특성 측정결과 상용 FTO를 사용한 DSC 수준의 효율을 나타내었다. 이에 따라 Pulsed Laser Deposition을 이용해 제작된 GZO 기판은 $TiO_2$ Blocking Layer를 이용하여 표면 파괴를 방지할 수 있었으며, 이는 향후 염료감응형 태양전지의 투명전극에 적용 가능 할 것으로 판단된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.175-175
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• 2008

투명전극으로 사용되고 있는 Indium tin oxide (ITO) 박막은 전기적 전도도와 기판과의 접확성, 화학적 안정성, 광투과율 등의 특성과 함께 우수한 전기 광학적 거동을 보이고 있다. 그러나 ITO는 고가의 재료이기 때문에 대체 투명전극으로 Al을 도핑한 ZnO 박막의 연구가 활발히 진행되고 있다. ZnO:Al 박막은 chemical vapor deposition, reactive magnetron sputtering, electron-beam evaporation, pulsed laser deposition 등의 당양한 방법을 이용하여 증착하였다. 그러나 최근 낮은 온도에서 대면적의 균일성과 우수한 특성 때문에 atomic layer depositon (ALD) 방법을 이용하여 많은 연구가 진행되고 있으며, 이런 투명전극은 태양전지를 위해 연구되어지고 있다. 따라서 본 연구에서는 ALD 방법으로 Al의 도핑 양을 조절하여, ZnO:Al 박막을 제조하여 그 특성을 평가하고, 또한 ZnO TFT를 제작하여 발표하고자 한다. ZnO와 ZnO:Al 박막은 실리콘과 유리 기판 위에 ALD (Lucida-D200, NCD Technology) 장치로 증착하였다. DEZn, TMA, $H_2O$는 ZnO와 ZnO:Al 박막을 증착하기 위한 전구체와 반응가스로 사용하였다. 증착된 박막은 XRD와 HRTEM을 이용하여 결정구조와 미세구조를 분석하였다. AFM과 4-point probe를 이용하여 증착된 박막의 표면 거칠기와 면저항을 관찰하였다. semiconductor parameter 분석기를 이용하여 제작된 ZnO TFT를 평가하였다.