• Journal of the Korean Ceramic Society
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• v.42 no.3 s.274
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• pp.211-217
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• 2005

[ $Zn_{1-x}Co_{x}O$ (x=0-0.3) films were grown on Corning 7059 glasses by asymmetrical bipolar pulsed dc magnetron sputtering. The c-axis orientation along (002) plane was enhanced with increasing Co concentration. The $Zn_{1-x}Co_{x}O$ films are grown with fibrous grains of tight dome shape. The transmittance spectra measured from UV-visible showed that sp-d exchange interactions and typical d-d transitions become activated with increasing Co concentration. The electrical resistivity of $Zn_{1-x}Co_{x}O$ films increased with increasing Co concentration, especially it increased greatly at $30at\% Co. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster is formed and the ferromagnetic properties are exhibited. The low electrical resistivity and room temperature ferromagnetism of $Zn_{1-x}Co_{x}O$ thin films suggested the possibility of the application to Diluted Magnetic Semiconductors (DMSs).

• Journal of the Korean Magnetics Society
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• v.2 no.3
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• pp.257-262
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• 1992

We have studied the variations of composition and magnetic properties with deposition rate in GdFe thin films by means of DC magnetron sputtering with the enhanced complex target method. Gd atomic percent was decreased with the increase of deposite rate. It appeared the transition phenomena at 1.0 ${\AA}/s the deposition rate. Also, the deposition rate increased with input power and the sputtering efficience was proportional to the number of Gd chip. An increase of the coercivity with input power can be interpreted by the large size of Fe crystal grains. We have introduced by the diffusion guard sputtering and it was effective for reproducibility of the sample. We have measured ${\theta}_k$ with Kerr angle gauge, and could observe that the ${\theta}_k$ was little varied with input power.

• Journal of Surface Science and Engineering
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• v.48 no.2
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• pp.43-49
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• 2015

This study reports a fabrication of $TiO_2$ on the surface of dental implants by pulsed d.c. magnetron sputtering from a Ti target. A systematic investigation on the microstructure and mechanical properties of $TiO_2$ films was carried out with the variation of $O_2$ contents and substrate temperatures. The effects of deposition parameters on the fabricated structures were investigated by X-ray diffraction (XRD) technique and field emission scanning electron microscope (FE-SEM). Hydrophilic properties were evaluated by measuring water contact angles on the film surface. With increasing $O_2$ contents up to 40%, surface roughness of $TiO_2$ film increased while relatively smooth surface was obtained with 50% $O_2$ contents. Surface roughness and adhesion strength both increased as substrate temperature increased up to $200^{\circ}C$. From these results, hydrophilic and adhesive properties of the present $TiO_2$ films synthesized with 40% $O_2$ at $200^{\circ}C$ are regarded to be suitable for bio-compatible applications.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.49.2-49.2
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• 2009

투명전극은 디스플레이, 태양전지와 같은 광전자 소자에 필수적이며, 지금까지 개발된 재료 중에는 ITO가 가장 투명하면서 전기전도도가 높고 생산성도 좋기 때문에 투명전극의 재료로 사용하고 있다. ITO는 낮은 비저항(${\sim}10^{-4}{\Omega}cm$) 과 높은 투과율 (~85 %), 상대적으로 넓은 밴드갭 에너지 (3.5 eV) 의특성과 같이 뛰어난 전기적 광학적 특성에 반해서 높은 원자재 가격, 불안정한 공급량 등으로 인한 문제점이꾸준히 제기되고 있다. 따라서 $In_2O_3$:Sn, ZnO:Al, ZnO:Ga, ZnO:F, ZnO:B, TiN 등과 같은 물질들로대체하려는 연구가 활발하게 진행되고 있다. ZnO는 ITO보다원자재의 수급이 원활하기 때문에 원가가 낮으며, 상대적으로 낮은 온도에서도 제작이 가능하다. 또한 화학적으로 안정적이므로 ZnO에 Al, Ga 등의 3족 원소를 도핑함으로써 낮은 비저항의 박막 제작이 가능하고, ITO 박막과 비교하여 etching이 쉬우며 기판과의 접착성이 좋으며, sputtering 공정시 plasma 분위기에서의 안정성이 뛰어나고 박막증착율이 높기 때문에 투명전극으로 적합한 재료이다. 본 연구에서는 cylindrical type의 Aldoping된 ZnO single target을 사용하여 박막 증착 압력의 변화를 주어 유리기판 위에 DC sputtering을 하였다. Fieldemission scanning electron microscope (FESEM)을 통해 ZnO:Al 박막의 표면의 형상과 두께를 확인하였으며, X-ray diffraction (XRD) 분석을 통해 박막의 결정학적 특성을 관찰하였다. 투명전극용 물질로서 ZnO:Al 박막의 적합성 여부를 확인하기 위하여 Van der Pauw 방법을 이용하여 박막의 비저항, 전자 이동도, 캐리어 농도를 측정하였으며, 박막의 기계적 성질 및 표면 접착성을 확인하기 위하여 nano-indentaion 분석을 하였다. 또한 UV-vis spectrophotometer를 이용하여 ZnO:Al 박막의 투과율을 분석하여 투명전극으로의 응용 가능성을 확인하였다.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.5
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• pp.281-287
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• 2005

Titanium aluminium nitride((TiAl)N) film is anticipated as an advanced coating film with wear resistance used for drills, bites etc. and with corrosion resistance at a high temperature. In this study, (TiAl)N thin films were deposited both at room temperature and at elevated substrate temperatures of 573 to 773 K by using a two-facing-targets type DC sputtering system in a mixture Ar and $N_2$ gases. Atomic compositions of the binary Ti-Al alloy target is Al-rich (25Ti-75Al (atm%)). Process parameters such as precursor volume %, substrate temperature and Ar/$N_2$ gas ratio were optimized. The crystallization processes and phase transformations of (TiAl)N thin films were investigated by X-ray diffraction, field-emission scanning electron microscopy. The microhardness of (TiAl)N thin films were measured by a dynamic hardness tester. The films obtained with Ar/$N_2$ gas ratio of 1:3 and at 673 K substrate temperature showed the highest microhardness of $H_v$ 810. The crystallized and phase transformations of (TiAl)N thin films were $Ti_2AlN+AlN{\rightarrow}TiN+AlN$ for Ar/$N_2$ gas ratio of 1:3, $Ti_2AlN+AlN{\rightarrow}TiN+AlN{\rightarrow}Ti_2AlN+TiN+AlN$ for Ar/$N_2$ gas ratio of 1:1 and $TiN+AlN{\rightarrow}Ti_2AlN+TiN+AlN{\rightarrow}Ti_2AlN+AlN{\rightarrow}Ti_2AlN+TiN+AlN$ for Ar/$N_2$ gas ratio of 3:1. The above results are discussed in terms of crystallized phases and microhardness.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.1
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• pp.10-14
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• 2014

Niobium nitride coatings have many potential thin film applications due to their chemical inertness, good mechanical properties, temperature stability and superconducting properties. In this study, $NbN_x$ coatings were prepared by inductively coupled plasma (ICP) assisted DC magnetron sputtering method on the surface of AISI 304 austenitic stainless steels. Effects of target power were studied on mechanical and chemical properties of the coatings. The coating structure was analyzed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The coating hardness was measured by micro-knoop hardness tester. The coating thickness was measured using a 3D profiler and wear characteristics were estimated using a ball-on-disk wear tester. The thickness of the $NbN_x$ coatings increased linearly from 300 nm to 2000 nm as the Nb target power increased, and it showed over $HK_{0.005}$ 4000 hardness above Nb target power of 300 W. Hexagonal ${\delta}^{\prime}$-NbN phase and cubic ${\delta}$-NbN phase were observed in the coating films and the hardness of the NbNx coatings was higher when these two peaks were mixed. The corrosion resistance increased with the increase of the Nb target power.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.163-163
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• 1999

MOSFET, MESFET 그리고 MODFET는 Logic ULSIs, high speed ICs, RF MMICs 등에서 중요한 역할을 하고 있으며, 그것의 gate electrode, contact, interconnect 등의 물질로는 refractory metal을 이용한 CoSi2, MoSi2, TaSi2, PtSi2, TiSi2 등의 효과를 얻어내고 있다. 그중 TiSi2는 비저항이 가장 낮고, 열적 안정도가 좋으며 SAG process가 가능하므로 simpler alignment process, higher transconductance, lower source resistance 등의 장점을 동시에 만족시키고 있다. 최근 소자차원이 scale down 됨에 따라 TiSi2의 silicidation 과정에서 C49 TiSi2 phase(high resistivity, thermally unstable phase, larger grain size, base centered orthorhombic structure)의 출현과 그것을 제거하기 위한 노력이 큰 issue로 떠오르고 있다. 여러 연구 결과에 따르면 PAI(Pre-amorphization zimplantation), HTS(High Temperature Sputtering) process, Mo(Molybedenum) implasntation 등이 C49를 bypass시키고 C54 TiSi2 phase(lowest resistivity, thermally stable phase, smaller grain size, face centered orthorhombic structure)로의 transformation temperature를 줄일 수 있는 가장 효과적인 방법으로 제안되고 있지만, 아직 그 문제가 완전히 해결되지 않은 상태이며 C54 nucleation에 대한 physical mechanism을 밝히진 못하고 있다. 본 연구에서는 증착 시 기판온도의 변화(400~75$0^{\circ}C$)에 따라 silicon 위에 DC/RF magnetron sputtering 방식으로 Ti/Si film을 각각 제작하였다. 제작된 시료는 N2 분위기에서 30~120초 동안 500~85$0^{\circ}C$의 온도변화에 따라 RTA법으로 각각 one step annealing 하였다. 또한 Al을 cosputtering함으로써 Al impurity의 존재에 따른 영향을 동시에 고려해 보았다. 제작된 시료의 분석을 위해 phase transformation을 XRD로, microstructure를 TEM으로, surface topography는 SEM으로, surface microroughness는 AFM으로 측정하였으며 sheet resistance는 4-point probe로 측정하였다. 분석된 결과를 보면, 고온에서 제작된 박막에서의 C54 phase transformation temperature가 감소하는 것이 관측되었으며, Al impuritydmlwhswork 낮은온도에서의 C54 TiSi2 형성을 돕는다는 것을 알 수 있었다. 본 연구에서는 결론적으로, 고온에서 증착된 박막으로부터 열적으로 안정된 phase의 낮은 resistivity를 갖는 C54 TiSi2 형성을 보다 낮은 온도에서 one-step RTA를 통해 얻을 수 있다는 결과와 Al impurity가 존재함으로써 얻어지는 thermal budget의 효과, 그리고 그로부터 기대할 수 있는 여러 장점들을 보고하고자 한다.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.39-47
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• 2003

Cr thin films were deposited on photosensitive polyimide substrates by RF bias sputtering and DC sputtering and the interfaces between Cr thin film and polyimide were observed using TEM. When the polyimide surface was in-situ RF plasma cleaned at the RF power density of 0.13-2.12 $W/cm^2$, increasing of RF power density changed the morphology of polyimide surfaces from round dig to sharp shape, and surface roughness increased by anisotropic etching. The intermixed layer-like interfaces between Cr and polyimide were observed in the RF bias sputtered specimens. This interface seems to be formed due to the RF cleaning effect; the polyimide surface was RF plasma cleaned while RF power was increased to the setting point before Cr deposition.

• Progress in Superconductivity
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• v.8 no.2
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• pp.181-185
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• 2007

For more than two decades Nb trilayer ($Nb/Al_2O_3/Nb$) process has been serving as the most stable fabrication process of the Josephson junction integrated circuits. Fast development of semiconductor fabrication technology has been possible with the recent advancement of the fabrication equipments. In this work, we took an advantage of advanced fabrication equipments in developing a superconducting Arithmetic Logic Unit (ALU) by using Nb trilayers. The ALU is a core element of a computer processor that performs arithmetic and logic operations on the operands in computer instruction words. We used DC magnetron sputtering technique for metal depositions and RF sputtering technique for $SiO_2$ depositions. Various dry etching techniques were used to define the Josephson junction areas and film pattering processes. Our Nb films were stress free and showed the $T{_c}'s$ of about 9 K. To enhance the step coverage of Nb films we used reverse bias powered DC magnetron sputtering technique. The fabricated 1-bit, 2-bit, and 4-bit ALU circuits were tested at a few kilo-hertz clock frequency as well as a few tens giga-hertz clock frequency, respectively. Our 1-bit ALU operated correctly at up to 40 GHz clock frequency, and the 4-bit ALU operated at up to 5 GHz clock frequency.

• Applied Microscopy
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• v.29 no.3
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• pp.265-274
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• 1999

The microstructure of Cu thin films in various deposition conditions was characterized. Cr films (50 nm thick) and Cu films (500 or 1000 nm thick) were deposited on polyimide films by DC magnetron sputtering. The Ar pressure during Cu deposition was controlled to 5, 50 and 100 mtorr. The microstructure was characterized using conventional and high resolution SEM and TEM. As sputtering pressure increases, open boundaries are observed more frequently. The Cu film deposited at 5 mtorr has a dense and uniform structure, while low-density regions or open boundaries between columns exist in the film deposited at higher pressure. As the film grows thicker, open boundaries are wider and the density of open boundaries are higher. The comparison between SEM and TEM show that the small features shown in high resolution SEM are grains. High resolution SEM is very effective to characterize the microstructure of the thin films. One column in the films deposited at 50 and 100 mtorr consists of several grains, which are smaller than those deposited at 5 mtorr.