• Design & Manufacturing
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• 제14권3호
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• pp.44-49
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• 2020

One of display trends today is development of high pixel density. To get high PPI, a small size of pixel must be developed. RGB pixel is arranged by evaporation process which determines pixel size. Normally, a fine metal mask (FMM; Invar alloy) has been used for evaporation process and it has advantages such as good strength, and low thermal expansion coefficient at low temperature. A FMM has been manufactured by chemical etching which has limitation to controlling the pattern shape and size. One of alternative method for patterning FMM is laser micromachining. Femtosecond laser is normally considered to improve those disadvantages for laser micromachining process due to such short pulse duration. In this paper, a femtosecond laser drilling for thickness of 16 ㎛ FMM is examined. Additionally, we introduce experimental results for controlling taper angle of hole by vibration module adapted in laser system. We used Ti:Sapphire based femtosecond laser with attenuating optics, co-axial illumination, vision system, 3-axis linear stage and vibration module. By controlling vibration amplitude, entrance and exit diameters are controllable. Using vibrating objective lens, we can control taper angle when femtosecond laser hole drilling by moving focusing point. The larger amplitude of vibration we control, the smaller taper angle will be carried out.

• 마이크로전자및패키징학회지
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• 제20권1호
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• pp.33-37
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• 2013

전구체의 농도가 ZnO 나노로드의 성장에 미치는 영향에 대하여 알아보았다. ZnO 나노로드는 수열합성법에 의하여 c-plane 사파이어 상에서 성장되었으며, 전구체 농도가 0.01M에서 0.025M로 증가할 때의 형태적, 구조적, 광학적 성질의 변화에 대하여 주사전자현미경, X-선 회절분석기, 그리고 Photoluminescence(PL) 분석을 통하여 알아보았다. 전구체의 몰 분율이 증가함에 따라서 나노로드의 두께와 길이가 모두 증가하는 경향을 보였으며, 성장 방향은 모두 c-axis 방향임을 알 수 있었다. PL 측정에서의 380 nm파장의 강한 emission으로부터, 수열합성법에 의하여 성장된 ZnO 나노로드는 결함의 영향이 적고 양호하게 성장되어 있음을 확인할 수 있었다.

• 한국진공학회지
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• 제7권s1호
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• pp.15-19
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• 1998

Structural and optical properties of $In_xGa_{1-X}N$ as well as $In_{0.1}Ga_{0.9}N$/GaN single quantum we11 (SQW) grown on sapphire (0001) substrate with an based GaN using rf-plasma assisted MBE have been investigated. The quality of the InXGal.,N fdm was improved as the growth temperature increased. In PL measurements at low temperatures, the band edge emission peaks of $In_xGa_{1-X}N$ was shifted to red region as an indium cell and substrate temperature increased. For $In_{0.1}Ga_{0.9}N$/GaN SQW, the optical emission energy has blue shift about 15meV in PL peak, due to the confined energy level in the well region. And, the FWHM of the $In_{0.1}Ga_{0.9}N$/GaN SQW was larger than that of the bulk Ino,la.9N films. The broadening of FWHM can be explained either as non-uniformity of Indium composition or the potential fluctuation in the well region. Photoconductivity (PC) decay measurement reveals that the optical transition lifetimes of the SQW measured gradually increased with temperatures.

• 한국기계가공학회지
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• 제15권2호
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• pp.51-56
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• 2016

High brittleness is a characteristic of glass, and in many cases it is broken during the process of machining due to processing problems, such as scratches, chipping, and notches. Machining defects occur due to the vibration of the equipment. Therefore, design techniques are needed that can control the vibration generated in the equipment to increase the strength of tempered glass. The natural frequency of the machine tool via vibration analysis (computer simulation) must be accurately understood to improve the design to ensure the stability of the machine. To accurately understand the natural frequency, 3D modeling, which is the same as actual apparatus, was used and a constraint condition was also applied that was the same as that of the actual apparatus. The maximum speeds of ultrasonic and high frequency, which are 15,000 rpm and 60,000 rpm, respectively, are considerably faster than those of typical machine tools. Therefore, an improved design is needed so that the natural frequency is formed at a lower region and the natural frequency does not increase through general design reinforcement. By restructuring the top frame of the glass processing, the natural frequency was not formed in the operating speed area with the improved design. The lower-order natural frequency is dominant for the effects that the natural frequency has on the vibration. Therefore, the design improvement in which the lower-order natural frequency is not formed in the operating speed area is an optimum design improvement. It is possible to effectively control the vibrations by avoiding resonance with simple design improvements.

• 한국기계가공학회지
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• 제16권6호
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• pp.1-6
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• 2017

Recently, the brittle materials such as ceramics, glass, sapphire and textile material have been widely used in semiconductors, aerospace and automobile owing to high functional characteristics. On the other hand, it has the characteristics of difficult-to-cut material relative to all materials. In this study, diamond electro-deposited band-saw machine was developed to operate stably using water-coolant type through relative motion between band-saw tool and $Al_2O_3$ material. High densified $Al_2O_3$ material was manufactured by spark plasma sintering method. The bulk density was observed by the Archimedes law and the theoretical density was estimated to be $3.88g/cm^3$ and its hardness 14.7 MPa. From the dicing sawing test of $Al_2O_3$ specimen, behavior of surface roughness and band-saw wear are dominantly affected by the increase of the band-saw linear velocity. Additionally, an continuous pattern type of diamond band-saw was a very effective due to entry impact as a one-off for brittle material.

• 마이크로전자및패키징학회지
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• 제26권4호
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• pp.113-118
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• 2019

In this study, we investigated the growth of single-crystallinity α-Ga₂O₃ thin films on c-plane sapphire substrates using halide vapor pressure epitaxy. We also found the optimal growth conditions to suppress the phase transition of α-Ga₂O₃. Our results confirmed that the growth temperature and partial pressure of the reactive gas greatly influenced the crystallinity. The optimal growth temperature range was about 460~510℃, and the α-Ga₂O₃ thin films with the highest crystallinity were obtained at a III/VI ratio of 4. The thickness and surface morphology of the thin films was observed by scanning electron microscopy. The film thickness was 6.938 ㎛, and the full width at half maximum of the ω-2θ scan rocking curve was as small as 178 arcsec. The optical band gap energy obtained was 5.21 eV, and the films were almost completely transparent in the near-ultraviolet and visible regions. The etch pit density was found to be as low as about 6.0 × 10⁴ cm^-2.

• 한국결정성장학회지
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• 제22권6호
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• pp.261-264
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• 2012

본 연구에서는 HVPE법으로 사파이어 기판(0001) 위에 성장시킨 GaN epilayer의 etching에 따른 표면변화 특성을 조사하였다. 주사전자 현미경(SEM) 관찰 결과, 3가지 형태를 갖는 육각형 모양의 etch pit(edge, screw, mixed) 들이 GaN epilayer의 두께 변화에 따라서 형성되었다. 이러한 관통전위들은(TDs) epilayer의 두께가 얇고, etch pit density가 높을수록 screw and mixed type TDs이 많이 관찰되었고, 두께가 증가할수록 etch pit density가 낮아지면서 edge and mixed type TDs들이 주로 존재하는 것을 관찰 할 수 있었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.38.1-38.1
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• 2009

Plasma etching is an essential process for electronic device industries and the particulate contamination during plasma etching has been interested as a big issue for the yield of productivity. The oxynitride glasses have a merit to prevent particulate contamination due to their amorphous structure and plasma etching resistance. The YSiAlON oxynitride glasses with increasing nitrogen content were manufactured. Each oxynitride glasses were fluorine-plasma etched and their plasma etching rate and surface roughness were compared with reference materials such as sapphire, alumina and quartz. The reinforcement mechanism of plasma etching resistance of the YSiAlON glasses studied by depth profiling at plasma etched surface using electron spectroscopy for chemical analysis. The plasma etching rate decreased with nitrogen content and there was no selective etching at the plasma etched surface of the oxynitride glasses. The concentration of silicon was very low due to the generation of SiF4 very volatile byproduct and the concentration of aluminum and yttrium was relatively constant. The elimination of silicon atoms during plasma etching was reduced with increasing nitrogen content because the content of the nitrogen was constant. And besides, the concentration of oxygen was very low on the plasma etched surface. From the study, the plasma etching resistance of the glasses may be improved by the generation of nitrogen related structural groups and those are proved by chemical composition analysis at plasma etched surface of the YSiAlON oxynitride glasses.

• 한국세라믹학회지
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• 제36권8호
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• pp.813-819
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• 1999

Ion implantation, photo-lithography, Ar ion milling과 hot press 법을 이용한 micro-fabrication techrique을 사용하여 고순도 알루미나 단결정인 사파이어의 내부에, 조절된 Ca의 첨가량을 갖고 있는, crack과 비슷한 형태의 기공들을 형성시켰다. 이 bi-cryslal을 각각의 온도에서 열처리하여 Ca 이온이 고온에서 알루미나의 morphology와 hcaling에 미치는 영향을 관찰하였다. 열처리 온도가 올라감에 따라서 crack-like pore의 내부에 hcxagonal bridging ligaments가 생성되었는데, 열처리 온도와 Ca의 첨가량이 증가할수록 크기가 커지는 것을 관찰할 수 있었고, 생성된 hexagonal bndgmg ligaments는 열처리가 진행됨에 따라 서서히 커지면서 모서리가 둥글어지는 현상을 관찰할 수 있었다. Bicrystal 내부에 형성된 crack-like pore는 열처리가 진행되면서 edge regression. ligamcnt growth 및 flow의 3가지의 특징적인 형태로 진행되었다. 이때 edge regression은 상대적으로 저온에서부터 전체 crack-like pore에서 서서히 일어나기 시작하였으며, ligament growth는 일부 crack-like pore에서 진행되있으며, 대단히 빠른 속도로 crack healing이 진행됨을 추정할 수 있었다. Flow는 $1800^{\circ}C$ 이상의 고온에서 모든 crack-like pore에 걸쳐서 느리게 일어남을 알 수 있었다.

• E2M - 전기 전자와 첨단 소재
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• 제9권1호
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• pp.30-37
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• 1996

Previously, crystallization of a-Si:H films on glass substrates were limited to anneal temperature below 600.deg. C, over 10 hours to avoid glass shrinkage. Our study indicates that the crystallization is strongly influenced by anneal temperature and weakly affected by anneal duration time. Because of the high temperature process and nonconducting substrate requirements for poly-Si TFTs, the employed substrates were limited to quartz, sapphire, and oxidized Si wafer. We report on poly-Si TFT's using high temperature anneal on a Si:H/Mo structures. The metal Mo substrate was stable enough to allow 1000.deg. C anneal. A novel TFT fabrication was achieved by using part of the Mo substrate as drain and source ohmic contact electrode. The as-grown a-Si:H TFT was compared to anneal treated poly-Si TFT'S. Defect induced trap states of TFT's were examined using the thermally stimulated current (TSC) method. In some case, the poly-Si grain boundaries were passivated by hydrogen. A-SI:H and poly-Si TFT characteristics were investigated using an inverted staggered type TFT. The poly -Si films were achieved by various anneal techniques; isothermal, RTA, and excimer laser anneal. The TFT on as grown a-Si:H exhibited a low field effect mobility, transconductance, and high gate threshold voltage. Some films were annealed at temperatures from 200 to >$1000^{\circ}C$ The TFT on poly-Si showed an improved $I_on$$I_off$ ratio of $10_6$, reduced gate threshold voltage, and increased field effect mobility by three orders. Inverter operation was examined to verify logic circuit application using the poly Si TFTs.