• 한국전기전자재료학회논문지
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• 제19권8호
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• pp.775-779
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• 2006

In this study, sputtered $Al_2O_3$ thin films were evaluated as a passivation layer in the process of InGaN-based blue LEDs in order to improve the brightness of LED lamps. In terms of packaged LED lamps, lamps with $Al_2O_3$ passivation layer emanated higher brightness than those with $SiO_2$ passivation layer, and LED lamps with 90 nm $Al_2O_3$ passivation layer were the brightest among four kinds of lamps. Although lamps with $Al_2O_3$ passivation had a slight increase in operating voltage, their brightness was improved about 13.6 % compare to the lamps made of conventional LEDs without the changes of emitting wavelength.

• 대한금속재료학회지
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• 제46권6호
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• pp.390-401
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• 2008

The objective of this study is to evaluate various machining characteristics of AlN-hBN machinable ceramics in micro end-milling process for its further application. First, AlN based machinable ceramics with hBN contents in the range of 10 to 20vol% were prepared by hot-pressing. Material properties of the composites, such as relative density, Vickers hardness, flexural strength, Young's modulus and fracture toughness were measured and compared. Then, micro end-milling experiments were performed to fabricate micro channels using prepared system. During the process, cutting forces, vibrations and AE signals were measured and analyzed using applied sensor system. Machined micro channel shapes and surface roughness were measured using 3D non-contact type surface profiler. From the experimental results, it can be observed that the cutting forces, vibrations and AE signal amplitudes decreased with increasing hBN contents. Also, measured surface roughness and profiles were improved with increasing hBN contents. As a result of this study, optimum machining conditions can be determined to fabricate desired products with AlN-hBN machinable ceramics based on the experimental results of this research.

• 한국결정성장학회지
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• 제22권1호
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• pp.11-14
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• 2012

AlGaN는 3.4~6.2 eV까지 넓은 밴드갭을 가지는 직접천이형 반도체이다. 최근에 자외영역의 광소자가 다양하게 응용되면서 자외선 발광이 가능한 AlGaN 역시 주목받고 있다. 이를 위해서는 고품질의 AlGaN 층이 필요하지만 GaN 층위에 AlGaN 층을 성장하는 것은 이들의 격자상수와 열팽창계수 차이로 인해 어렵다. 본 논문에서, multi-sliding boat법이 적용된 혼합소스 HVPE법을 이용하여 GaN template 위에 LED 구조를 성장하였다. 활성층의 Al 조성을 조절함으로써 AlGaN의 격자상수 변화와 광학적 변화를 관찰하고자 하였다. 에피 성장을 위해 HCl과 $NH_3$ 가스를 혼합소스 표면으로 흘려주었고, 수송가스로는 $N_2$를 사용하였다. 소스영역과 성장영역의 온도는 각각 900과 $1090^{\circ}C$로 안정화하였다. 성장 후 샘플은 x-ray diffraction(XRD)과 electro luminescence(EL) 측정을 하였다.

• 동력기계공학회지
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• 제10권2호
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• pp.83-88
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• 2006

Corrosion characterization of Fe-XAl-0.3Y(X=5, 10, 14 wt%) alloys in $0.1{\sim}1N$ sulphuric acid at room temperature was studied using potentiodynamic techniques. The morphology and components of corrosion products on surface of Fe-aluminide alloys were investigated using SEM/EDX, XRD. The potentiodynamic polarization curve of alloys exhibited typical active, passive, transpassive behaviour. Corrosion potential($E_{corr}$) and corrosion current density($I_{corr}$) values of Fe-XAl-0.3Y alloys followed linear rate law. $E_{corr}$ of 10Al alloy and 14Al alloy was ten times lower than 5Al alloy. Icorr of 14Al alloy was five times lower than 5Al alloy. The passive film on the surface of Fe-5Al-0.3Y alloy was formed iron oxide. Fe-10Al-0.3Y and Fe-14Al-0.3Y alloys passive films were aluminium oxide. especially, Fe-14Al-0.3Y alloy showed good corrosion resistance in $0.1{\sim}1N$ sulphuric acid. This is attributed to the forming of protective $Al_2O_3$ oxide on the surface of Fe-14Al-0.3Y alloy.

• 마이크로전자및패키징학회지
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• 제22권3호
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• pp.19-23
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• 2015

본 연구에서는 COG (Chip On Glass) 패키지 적용을 위해 Au 범프를 전기도금 공정을 사용하여 Al/Si wafer와 SiN/Si wafer 위에 TiW/Au 구조를 갖는 두 종류의 Au범프 시료를 제작하였다. UBM (Under Bump Metallurgy) 물질로서 TiW 박막을 스퍼터링 방법으로 증착하였으며 스퍼터링 입력 파워(500~5000 Watt)에 따른 박리 현상을 관찰하였다. 안정된 계면 접착을 나타내는 스퍼터링 파워는 1500 Watt임을 확인 할 수 있었다. 또한 SAICAS (Surface And Interfacial Cutting Analysis System) 장비를 사용하여 기판 종류에 따른 Au Bump의 접착력을 조사하였다. TiW 증착 조건은 스퍼터링 파워를 1500 Watt로 고정하였다. TiW/Au 계면의 접착력은 두 종류의 wafer (Al/Si과 SiN/Si wafers)에 관계없이 오차 범위 안에서 비슷한 접착력을 보여주었으나, TiW UBM 스퍼터링 박막 계면에서의 접착력은 하부 박막인 Al 금속과 SiN 비금속 박막에서의 접착력 차이가 약 2.2배 크게 나타났다. 즉, Al/Si wafer와 SiN/Si wafer위에 증착된 TiW의 접착력은 각각 0.475 kN/m와 0.093 kN/m 값을 나타내었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.112-112
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• 2009

In this study, the effect of a long post-deposition thermal annealing(600 and 1000 $^{\circ}C$) on the surface acoustic wave (SAW) properties of polycrystalline (poly) aluminum-nitride (AlN) thin films grown on a 3C-SiC buffer layer was investigates. The poly-AlN thin films with a (0002) preferred orientation were deposited on the substrates by using a pulsed reactive magnetron sputtering system. Experimental results show that the texture degree of AlN thin film was reduced along the increase in annealing temperature, which caused the decrease in the electromechanical coupling coefficient ($k^2$). The SAW velocity also was decreased slightly by the increase in root mean square (RMS) roughness over annealing temperature. However, the residual stress in films almost was not affect by thermal annealing process due to small lattice mismatch different and similar coefficient temperature expansion (CTE) between AlN and 3C-SiC. After the AlN film annealed at 1000 $^{\circ}C$, the insertion loss of an $IDT/AlN/3C-SiC/SiO_2/Si$ structure (-16.44 dB) was reduced by 8.79 dB in comparison with that of the as-deposited film (-25.23 dB). The improvement in the insertion loss of the film was fined according to the decrease in the grain size. The characteristics of AlN thin films were also evaluated using Fourier transform-infrared spectroscopy (FT-IR) spectra and X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) images.

• 대한금속재료학회지
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• 제50권1호
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• pp.78-85
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• 2012

Aluminum nitride(AlN) is a compound (III-V group) of hexagonal system with a crystal structure. Its Wurzite phase is a very wide band gap semiconductor material. It has not only a high thermal conductivity, a high electrical resistance, a high electrical insulating constant, a high breakdown voltage and an excellent mechanical strength but also stable thermal and chemical characteristics. This study is on the preferred orientation characteristics of AlN thin films by reactive evaporation using $NH_3$. We have manufactured an AlN thin film and then have checked the crystal structure and the preferred orientation by using an X-ray diffractometer and have also observed the microstructure with TEM and AlN chemical structure with FT-IR. We can manufacture an excellent AlN thin film by reactive evaporation using $NH_3$ under 873 K of substrate temperature. The AlN thin film growth is dependent on Al supplying and $NH_3$ has been found to be effective as a source of $N_2$. However, the nuclear structure of AlN did not occur randomly around the substrate a particle of the a-axis orientation in fast growth speed becomes an earlier crystal structure and is shown to have an a-axis preferred orientation. Therefore, reactive evaporation using $NH_3$ is not affected by provided $H_2$ amount and this can be an easy a-axis orientation method.

• 한국세라믹학회지
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• 제16권4호
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• pp.206-212
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• 1979

The phase relations and microstructure appeared at 1700℃ in a system of Si3N4-Al2O3-SiO2 were studied. The samples were pressurelessly sintered at 1700℃ for 1hr and reheated at 1600℃ for 1hr under nitrogen atmosphere. The compounds formed were identified by X-ray diffraction method and the microstrues were observed by SEM. The stable phases appeared in this system were X-phase, Si2ON2, β'-Si3N4 and Mullite. From the results of those experiments, it was concluded that the X-phase has very close composition to that proposed by G, K. Layden, Si3Al6O12N2. SEM photographs showed that Si2ON2 was a plate phase and X-phase was a rectagular plate phase.

• 한국재료학회지
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• 제25권3호
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• pp.138-143
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• 2015

Aluminum nitride, a compound semiconductor, has a Wurtzite structure; good material properties such as high thermal conductivity, great electric conductivity, high dielectric breakdown strength, a wide energy band gap (6.2eV), a fast elastic wave speed; and excellent in thermal and chemical stability. Furthermore, the thermal expansion coefficient of the aluminum nitride is similar to those of Si and GaAs. Due to these characteristics, aluminum nitride can be applied to electric packaging components, dielectric materials, SAW (surface acoustic wave) devices, and photoelectric devices. In this study, we surveyed the crystallization and preferred orientation of AlN thin films with an X-ray diffractometer. To fabricate the AlN thin film, we used the magnetron sputtering method with $N_2$, NH3 and Ar. According to an increase in the partial pressures of $N_2$ and $NH_3$, Al was nitrified and deposited onto a substrate in a molecular form. When AlN was fabricated with $N_2$, it showed a c-axis orientation and tended toward a high orientation with an increase in the temperature. On the other hand, when AlN was fabricated with $NH_3$, it showed a-axis orientation. This result is coincident with the proposed mechanism. We fabricated AlN thin films with an a-axis orientation by controlling the sputtering electric power, $NH_3$ pressure, deposition speed, and substrate temperature. According to the proposed mechanism, we also fabricated AlN thin films which demonstrated high a-axis and c-axis orientations.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.173-173
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• 2012

본 연구는 segment target을 장착한 unbalanced magnetron sputtering을 활용하여 CrZr-Al-N 박막을 합성하고 박막의 고온안정성과 미세구조를 연구하는데 그 목적이 있다. 박막의 Al 함량을 조절하기 위하여 각 segment target은 Cr,Zr을 일정vol% 유지하며 Al vol%만 변화하여 설계하였다. 박막의 고온안정성을 실험하기 위해 각 시편은 $100{\sim}500^{\circ}C$ 사이의 온도에서 1시간씩 annealing 처리를 실시한 후에 경도를 측정하였다. 박막의 미세구조 단면을 위해 FE-SEM을 이용하였으며 이밖에 박막의 조성, 경도 및 결정구조를 측정하기 위해 EDS, microhardness testing system, XRD를 사용하였다. Al 부피비를 변화시킨 Segment target을 활용한 박막합성에서 박막의 Al함량은 각각 1/11에서 4.6at.%, 1/5에서 8.1at.%, 1/3에서 12.9at.% 로 나타났으며, 박막의 경도는 4.6~12.9at.% 사이의 Al 함량을 갖는 박막에 대해 모두 유사한 값을 가졌으며 31GPa로 측정되었다. 박막의 단면 구조 역시 4.6~12.9at.% 사이의 Al 함량을 갖는 박막에 대해 모두 columnar 구조가 관찰되었다.