• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.57-57
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• 2009

반도체 device가 고집적화 및 다층화 되어짐에 따라 현재 사용되고 있는 구리 interconnect의 확산방지막인 Ta/TaN은 많은 문제가 발생하고 있다. 고집적화 된 반도체 소자에 적용시키기에는 Ta/TaN 확산 방지막의 고유 저항값이 매우 크고, 구리의 증착에 필요한 seed layer의 크기도 문제화 된다고 보고되어지고 있다. 이러한 이유로 인해 점차 고집적화 되어지는 반도체 기술에 맞추어 새로운 확산 방지막에 대한 연구가 현재 활발히 이루어지고 있다. 이에 새로운 확산 방지막으로써 대두되고 연구되고 있는 재료가 Ruthenium (Ru)이다. Ru은 공기 중에서 매우 안정하고 고유저항 값 또한 $13\;{\mu}{\Omega}\;cm$의 Ta에 비해 $7.1\;{\mu}{\Omega}\;cm$의 매우 작은 고유저항 특성을 가지고 있다. 또한, Ru은 구리와의 우수한 접착성으로 인해 구리의 interconnect의 형성에 있어 seed layer가 필요하지 않을 뿐만 아니라 높은 annealing 온도에서도 무시할 만큼 작은 solid solubility를 가지며 구리와의 계면에서 새로운 화합물을 형성하지 않으며 annealing시 구리의 delamination을 유발시키지도 않는다. 이에 따라, 평탄화와 소자 분리를 위하여 chemical mechanical planarization (CMP) 공정이 필요하게 되었다. 하지만, Ru의 noble한 성질과 Ru 확산방지막 CMP공정 시 노출되는 다른 이종 물질 사이의 최적화 된 selectivity를 구현하는데 많은 어려움이 있다. 이로인해 Ru 확산 방지막을 위한 CMP slurry에 대한 연구는 아직 미흡한 수준이다. 본 연구에서는 Ru이 확산방지막으로 사용되었을 때 이를 위한 CMP slurry에 대한 평가와 연구가 이루어졌다. Slurry 조성과 농도 및 pH에 따른 전기 화학적 분석을 통하여 slurry 내에서 각각의 막질들이 어떠한 상태로 존재하는지 분석해 보았다. 또한, Ru을 비롯한 이종막질들의 etch rate, removal rate와 selectivity에 대한 연구가 진행되었다. 최종적으로 Ru 확산방지막 CMP를 위한 최적화된 slurry를 제안하였다.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.2 s.39
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• pp.15-19
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• 2006

The resistance switching characteristics of amorphous $SiO_2$ and poly-crystalline $TiO_2$ were investigated. Both films exhibit well defined switching characteristics with low and high resistance states. From I-V curve analyses, it was found that the low resistance states of both films obey an ohmic conduction mechanism and the high resistance states show generation of a Schottky potential barrier. Regarding the mechanism for resistance switching of the binary oxide, it is suggested that the generation and annihilation of potential barriers accounts for the changes to the high resistance state and low resistance state, respectively. The device operation characteristic parameters such as reset and set voltages of $TiO_2$ are distinctly smaller than those of $SiO_2$, indicating that the values are related to the dielectric constant.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.75-78
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• 2006

In case of contacts between semiconductor and metal in semiconductor circuits, they become unstable because of thermal budget. To prevent these problems, we use diffusion barrier that has a good thermal stability between metal and semiconductor. So we consider the diffusion barrier to prevent the increase of contact resistance between the interfaces of metals and semiconductors, and the increase of resistance and the reaction between the interfaces. In this paper we deposited tungsten boron carbon nitride (W-B-C-N) thin film on silicon substrate. The impurities of the $1000\;{\AA}-thick$ W-B-C-N thin films provide stuffing effect for preventing the inter-diffusion between metal thin films $(Cu-2000\;{\AA})$ and silicon during the high temperature $(700\~1000^{\circ}C)$ annealing process.

• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.47-55
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• 2007

In this study, applicability of electrical conductivity monitoring technique for containment barrier such as soil-bentonite wall was evaluated. Laboratory tests including permeability tests and column tests were performed to understand variations in electrical conductivity at different bentonite contents, hydraulic conductivities, and heavy metal concentrations. The electrical conductivity of compacted soil-bentonite mixtures was found to increase proportionally with bentonite content. Accordingly, the hydraulic conductivity of compacted soil-bentonite mixtures which decreases linearly with increasing bentonite content was found to have an inversely proportional relationship with the electrical conductivity. In column tests, electrical conductivity breakthrough curves and concentration breakthrough curves were simultaneously obtained. These results indicated that electrical conductivity measurement can be an effective means of detecting heavy metal transport at the desired locations within barriers and verifying possible contaminant leakage. Experimental results obtained from this study showed that the electrical conductivity measurement can be a promising tool for monitoring of containment barrier.

• Korean Journal of Materials Research
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• v.19 no.1
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• pp.28-32
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• 2009

Silicon carbide (SiC) is a promising material for power device applications due to its wide band gap (3.26 eV for 4H-SiC), high critical electric field and excellent thermal conductivity. The Schottky barrier diode is the representative high-power device that is currently available commercially. A field plate edge-terminated 4H-SiC was fabricated using a lift-off process for opening the Schottky contacts. In this case, Ni/Ti dual-metal contacts were unintentionally formed at the edge of the Schottky contacts and resulted in the degradation of the electrical properties of the diodes. The breakdown voltage and Schottky barrier height (SBH, ${\Phi}_B$) was 107 V and 0.67 eV, respectively. To form homogeneous single-metal Ni/4H-SiC Schottky contacts, a deposition and etching method was employed, and the electrical properties of the diodes were improved. The modified SBDs showed enhanced electrical properties, as witnessed by a breakdown voltage of 635 V, a Schottky barrier height of ${\Phi}_B$=1.48 eV, an ideality factor of n=1.04 (close to one), a forward voltage drop of $V_F$=1.6 V, a specific on resistance of $R_{on}=2.1m{\Omega}-cm^2$ and a power loss of $P_L=79.6Wcm^{-2}$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.438-439
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• 2013

Microelectronic devices의 접촉저항의 향상을 위해 Metal silicides의 형성 mechanism과 전기적 특성에 대한 연구가 많이 이루어지고 있다. 지난 수십년에 걸쳐, Ti silicide, Co silicide, Ni silicide 등에 대한 개발이 이루어져 왔으나, 계속적인 저저항 접촉 소재에 대한 요구에 의해 최근에는 Rare earth silicide에 관한 연구가 시작되고 있다. Rare-earth silicide는 저온에서 silicides를 형성하고, n-type Si과 낮은 schottky barrier contact (~0.3 eV)를 이룬다. 또한, 비교적 낮은 resistivity와 hexagonal AlB2 crystal structure에 의해 Si과 좋은 lattice match를 가져 Si wafer에서 high quality silicide thin film을 성장시킬 수 있다. Rare earth silicides 중에서 ytterbium silicide는 가장 낮은 electric work function을 갖고 있어 낮은 schottky barrier 응용에서 쓰이고 있다. 이로 인해, n-channel schottky barrier MOSFETs의 source/drain으로써 주목받고 있다. 특히 ytterbium과 molybdenum co-deposition을 하여 증착할 경우 thin film 형성에 있어 안정적인 morphology를 나타낸다. 또한, ytterbium silicide와 마찬가지로 낮은 면저항과 electric work function을 갖는다. 그러나 ytterbium silicide에 molybdenum을 화합물로써 높은 농도로 포함할 경우 높은 schottky barrier를 형성하고 epitaxial growth를 방해하여 silicide film의 quality 저하를 야기할 수 있다. 본 연구에서는 ytterbium과 molybdenum의 co-deposition에 따른 silicide 형성과 전기적 특성 변화에 대한 자세한 분석을 TEM, 4-probe point 등의 다양한 분석 도구를 이용하여 진행하였다. Ytterbium과 molybdenum을 co-deposition하기 위하여 기판으로 $1{\sim}0{\Omega}{\cdot}cm$의 비저항을 갖는 low doped n-type Si (100) bulk wafer를 사용하였다. Native oxide layer를 제거하기 위해 1%의 hydrofluoric (HF) acid solution에 wafer를 세정하였다. 그리고 고진공에서 RF sputtering 법을 이용하여 Ytterbium과 molybdenum을 동시에 증착하였다. RE metal의 경우 oxygen과 높은 반응성을 가지므로 oxidation을 막기 위해 그 위에 capping layer로 100 nm 두께의 TiN을 증착하였다. 증착 후, 진공 분위기에서 rapid thermal anneal(RTA)을 이용하여 $300{\sim}700^{\circ}C$에서 각각 1분간 열처리하여 ytterbium silicides를 형성하였다. 전기적 특성 평가를 위한 sheet resistance 측정은 4-point probe를 사용하였고, Mo doped ytterbium silicide와 Si interface의 atomic scale의 미세 구조를 통한 Mo doped ytterbium silicide의 형성 mechanism 분석을 위하여 trasmission electron microscopy (JEM-2100F)를 이용하였다.

• Journal of the Korean institute of surface engineering
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• v.31 no.1
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• pp.12-23
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• 1998

The Thermal Barrier Coating(TBC) has been used to improve the heat barrier and tribological properties of the aircraft engine and the automobile engine in high temperature. Especially, the high temperature tribological propertied of the cylinder haed and the piston crown of diesel engine was emphasized. Therefore, the purpose of this work was to evaluate the microstructure, tribological propeer in high tempearmal shock resistance and bonding strength of five layer functionally gradient TBC for the applications. The five layerwere composed with 100% ceramic insulating later, 75(ceramic):25 (metal) layer, 50:50 layer, 25:75 layer and 100% metal bonding layer to redude the thermal stress. the YSL and MSL poweders were the insulation ceramics powers. The NiCrAly, Inconel625 and SUS powders were the bonding and mixingg powders for plasma spray process. According to the result of high temperature wear test, the wera resistance of YSZ/NiCrAlY siytem was most out standing at 600 and $800^{\circ}C$. At $400^{\circ}C$, the wear resistance of YSZ/Inconel system was better than others. Wear volume at other temperature because of the low temperature degration of zirconia. The thermal shock mechanism of 5 later is the vertical crack gegration in insulating layer. this means that the initial cracks were generated in the top layer, and then developed into the composite layers during thermal shock test. Finally, these cracks werereached to the interface of coating and substrate and also, these vertioal cracks join with the horizontal cracks of the each layers. The bonding strength of YSZ/NiCrAlY and YSZ/Inconel 5 layer system is better than other 5layer systems. The theramal shock resistance of thermal barrier coating s with 5 layer system is better than that of 3 layers and 2 layers.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.109-112
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• 2008

The miniaturization of device size and submicron process causes serious problems in conventional metallization due to the solubility of silicon and metal at the interface, such as an increasing contact resistance in the contact hole and interdiffusion between metal and silicon. Moreover, the interaction between Cu and Si is so strong and detrimental to the electrical performance of Si even at temperatures below $200^{\circ}C$. Therefore it is necessary to implement a barrier layer between Cu and Si. So we study W-C-N diffusion barrier for prevent Cu diffusion as a function of $N_2$ gas flow and thermal stability. Especially, we also study the W-C-N diffusion barrier for analyzing the change of lattice constants.

• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.348-352
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• 2007

In submicron processes, the feature size of ULSI devices is critical, and it is necessary both to reduce the RC time delay for device speed performance and to enable higher current densities without electromigration. In case of contacts between semiconductor and metal in semiconductor devices, it may be very unstable during the thermal annealing process. To prevent these problems, we deposited tungsten carbon nitride (W-C-N) ternary compound thin film as a diffusion barrier for preventing the interdiffusion between metal and semiconductor. The thickness of W-C-N thin film is $1,000{\AA}$ and the process pressure is 7mTorr during the deposition of thin film. In this work we studied the interface effects W-C-N diffusion barrier using the XRD and 4-point probe.

• Journal of IKEEE
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• v.23 no.1
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• pp.193-199
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• 2019

In this study, we have proposed a floating metal guard ring structure based on TCAD simulation in order to enhance the breakdown voltage characteristics of gallium oxide ($Ga_2O_3$) vertical high voltage switching Schottky barrier diode. Unlike conventional guard ring structures, the floating metal guard rings do not require an ion implantation process. The locally enhanced high electric field at the anode corner was successfully suppressed by the metal guard rings, resulting in breakdown voltage enhancement. The number of guard rings and their width and spacing were varied for structural optimization during which the current-voltage characteristics and internal electric field and potential distributions were carefully investigated. For an n-type drift layer with a doping concentration of $5{\times}10^{16}cm^{-3}$ and a thickness of $5{\mu}m$, the optimum guard ring structure had 5 guard rings with an individual ring width of $1.5{\mu}m$ and a spacing of $0.2{\mu}m$ between rings. The breakdown voltage was increased from 940 V to 2000 V without degradation of on-resistance by employing the optimum guard ring structure. The proposed floating metal guard ring structure can improve the device performance without requiring an additional fabrication step.