• 전력전자학회논문지
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• 제21권4호
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• pp.356-363
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• 2016

The design methodology of an adequate input voltage and magnetizing inductance to minimize reactive power is suggested to design a wireless power transfer (WPT) converter for high-power transfer efficiency. To increase the magnetizing inductance, the turn number of the WPT coil is increased, thus causing high parasitic resistance in the WPT coil. Moreover, the high coil resistance produces high conduction loss in the transfer and receive coils. Therefore, the analysis of conduction loss is used in the design of the WPT coil and the operating point of the WPT converter. To verify the proposed design methodology, the mathematical analysis of the conduction loss is presented by experimental results.

• 센서학회지
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• 제24권1호
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• pp.10-14
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• 2015

This paper reports the results of a study on the optimization of the etching profile, which is an important factor in deep-reactive-ion etching (DRIE), i.e., dry etching. Dry etching is the key processing step necessary for the development of the Internet of Things (IoT) and various microelectromechanical sensors (MEMS). Large-area etching (open area > 20%) under a high-frequency (HF) condition with nonoptimized processing parameters results in damage to the etched sidewall. Therefore, in this study, optimization was performed under a low-frequency (LF) condition. The HF method, which is typically used for through-silicon via (TSV) technology, applies a high etch rate and cannot be easily adapted to processes sensitive to sidewall damage. The optimal etching profile was determined by controlling various parameters for the DRIE of a large Si wafer area (open area > 20%). The optimal processing condition was derived after establishing the correlations of etch rate, uniformity, and sidewall damage on a 6-in Si wafer to the parameters of coil power, run pressure, platen power for passivation etching, and $SF_6$ gas flow rate. The processing-parameter-dependent results of the experiments performed for optimization of the etching profile in terms of etch rate, uniformity, and sidewall damage in the case of large Si area etching can be summarized as follows. When LF is applied, the platen power, coil power, and $SF_6$ should be low, whereas the run pressure has little effect on the etching performance. Under the optimal LF condition of 380 Hz, the platen power, coil power, and $SF_6$ were set at 115W, 3500W, and 700 sccm, respectively. In addition, the aforementioned standard recipe was applied as follows: run pressure of 4 Pa, $C_4F_8$ content of 400 sccm, and a gas exchange interval of $SF_6/C_4F_8=2s/3s$.

• 공업화학
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• 제17권3호
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• pp.327-330
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• 2006

Si nanodot 배열을 형성하기 위하여 $NbO_{x}$ nanopillar를 건식식각 공정의 식각마스크로써 이용하기 위한 가능성이 조사되었다. $NbO_{x}$ nanopillar는 Al과 Nb의 양극산화 공정을 이용하여 준비되었다. $NbO_{x}$ nanopillar의 식각속도와 식각프로파일은 고밀도 플라즈마를 이용한 반응성 이온 식각법에 의해서 식각가스의 농도와 coil rf power, 그리고 dc bias voltage를 각각 변화시키면서 조사 되었다. $Cl_{2}$ 가스의 농도가 증가할수록 $NbO_{x}$ nanopillar의 식각속도는 감소하였고 coil rf power와 dc bias voltage의 증가는 식각속도의 상승을 초래했다. 선택된 식각조건에서 식각시간을 변화하여 $NbO_{x}$ nanopillar의 식각특성 및 식각메커니즘이 조사되었다.

• 한국초전도ㆍ저온공학회논문지
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• 제16권4호
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• pp.49-52
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• 2014

REBCO coated conductor (CC) tapes with superior mechanical and electromechanical properties are preferable in applications such as superconducting coils and magnets. The CC tapes should withstand factors that can affect their performance during fabrication and operation of its applications. In coil applications, CC tapes experience different mechanical constraints such as tensile or compressive stresses. Recently, the critical current ($I_c$) degradation of CC tapes used in coil applications due to delamination were already reported. Thermal cycling, coefficient of thermal expansion mismatch among constituent layers, screening current, etc. can induce excessive transverse tensile stresses that might lead to the degradation of $I_c$ in the CC tapes. Also, CC tapes might be subjected to very high magnetic fields that induce strong Lorentz force which possibly affects its performance in coil applications. Hence, investigation on the delamination mechanism of the CC tapes is very important in coiling, cooling, operation and design of prospect applications. In this study, the electromechanical properties of REBCO CC tapes fabricated by reactive co-evaporation by deposition and reaction (RCE-DR) under transversely applied loading were investigated. Delamination strength of the CC tape was determined using the anvil test. The $I_c$ degraded earlier under transverse tensile stress as compared to that under compressive one.

• Korean Chemical Engineering Research
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• 제43권4호
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• pp.531-536
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• 2005

포토리지스트 마스크로 패턴된 CoTb 및 CoZrNb 자성 박막에 대한 유도 결합 플라즈마 반응성 이온 식각이 $Cl_2/Ar$와 $C_2F_6/Ar$ 가스를 이용하여 진행되었고 식각 속도와 식각 프로파일 측면에서 조사되었다. $Cl_2$와 $C_2F_6$ 가스의 농도가 증가함에 따라서 자성 박막들의 식각 속도는 감소하였고 식각 경사는 낮아졌다. 자성 박막들의 식각 가스로서 $Cl_2/Ar$이 빠른 식각 속도와 가파른 식각 경사를 얻는데 있어서 $C_2F_6/Ar$ 보다 더 효과적이었다. Coil rf power의 증가는 플라즈마 내의 Ar 이온과 라디칼의 밀도를 증가시키고 dc bias voltage의 증가는 기판으로 스퍼터되는 Ar 이온의 에너지를 증가시키기 때문에 coil rf power와 dc bias voltage가 증가할수록 식각 속도와 식각 경사는 증가하였지만 패턴의 측면에서 재증착이 일어났다. 자성 박막들의 적층으로 형성된 magnetic tunnel junction stack에 고밀도 플라즈마 반응성 이온 식각을 적용하여, 높은 식각 경사와 재증착이 없는 깨끗한 식각 프로파일을 얻었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.932_933
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• 2009

A technology based on thyristors will be used to manufacture the super-conducting coil AC/DC converters because of the low ratio of cost over installed power compared to a design based on GTO or similar technology. But phase-controlled converter suffers from fundamental disadvantage. They inject current harmonics into the input ac mains due to their nonlinear characteristics, thereby distort the supply voltage waveform, and demand reactive power from the associated ac power system at retarded angles. To overcome this disadvantage, in the case of two series converters at the DC side, connected to the same step-down transformer, apply for the sequence control. It is the most simple and efficient way to reduce the reactive power consumption at low cost. Analytical sequence control algorithm is suggested, the validity of the proposed scheme has been verified by experimental results with the small-scaled International Thermonuclear Experimental Reactor (ITER) Power Supply to minimize reactive power consumption.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.77-77
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• 2011

These days, a growing demand for memory device is filled up with the flash memory and the dynamic random access memory (DRAM). Although DRAM is a reasonable solution for current demand, the universal novel memory with high density, high speed and nonvolatility, needs to be developed. Among various new memories, the magnetic random access memory (MRAM) device is considered as one of good candidate memories because of excellent features including high density, high speed, low operating power and nonvolatility. The etching of MTJ stack which is composed of magnetic materials and insulator such as MgO is one of the vital process for MRAM. Recently, MgO has attracted great interest in the MTJ stack as tunneling barrier layer for its high tunneling magnetoresistance values. For the successful realization of high density MRAM, the etching process of MgO thin films should be investigated. Until now, there were some works devoted to the investigations on etch characteristics of MgO thin films. Initially, ion milling was applied to the etching of MgO thin films. However, ion milling has many disadvantages such as sidewall redeposition and etching damage. High density plasma etching containing the magnetically enhanced reactive ion etching and high density reactive ion etching have been employed for the improvement of etching process. In this work, inductively coupled plasma reactive ion etching (ICPRIE) system was adopted for the improvement of etching process using MgO thin films and etching gas mixes of $CH_4$/Ar and $CH_4$/$O_2$/Ar have been employed. The etch rates are measured by a surface profilometer and etch profiles are observed using field emission scanning emission microscopy (FESEM). The effects of gas concentration and etch parameters such as coil rf power, dc-bias voltage to substrate, and gas pressure on etch characteristics will be systematically explored.

• 한국진공학회지
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• 제7권2호
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• pp.161-168
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• 1998

Taguchi가 제안한 강건설계 및 연구자의 주관에 의존하는 통상적인 실험방법을 병 행하여 CH4/H2 유도결합 고밀도 플라즈마를 이용한 InP 소재의 반응성이온에칭에 있어 공 정변수들이 식각특성에 미치는 영향을 분석하고 적정조건을 도출하였다. 연구 결과 ICP전력 은 표면거칠기와 측벽수직도, bias 전력은 식각속도와 수직도에, CH4분율은 수직도와 식각 속도, 석영창과 시료 사이의 거리는 표면 거칠기에 영향을 주는 변수로 작용하였고, 식각속 도에 가장 크게 영향을 주는 변수는 공정압력임을 알 수 있었다. 결과적으로 ICP Power 700W, bias Power 150W, 시편/coil 거리 14cm, 압력 7.5mTorr, 15% $CH_4$의 적정조건에서 시간당 약 3.1$\mu\textrm{m}$의 식각속도와 미려한 표면을 얻어, 기존의 반응성 이온 식각(RIE)과 비교하 여 1.5배 이상의 식각속도를 얻을 수 있었다.

• 공업화학
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• 제18권1호
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• pp.24-28
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• 2007

$Cl_2/Ar$ 가스의 고밀도 플라즈마를 이용하여 ZnO 박막에 대한 식각이 연구되었다. $Cl_2$ 가스의 농도, coil rf power, dc-bias 전압, 그리고 공정 압력을 변화시켜서 ZnO 박막의 식각특성을 체계적으로 조사하였다. $Cl_2$ 가스의 농도가 증가할수록 ZnO 박막의 식각 속도는 증가하였고, 식각된 패턴 주변의 재증착은 감소되었지만 식각된 패턴의 측면 경사는 낮아졌다. Coil rf power와 dc-bias 전압이 증가할수록 ZnO 박막의 식각 속도가 증가하였고, 식각 프로파일이 개선되었다. 공정 압력이 증가 할수록 ZnO 박막의 식각 속도가 미세하게 증가하였으나 식각 프로파일의 변화는 관찰되지 않았다. 이러한 결과들을 토대로 하여 ZnO 박막의 최적의 식각 조건이 설정되었다. 재증착이나 잔류물이 없이 대략 $75^{\circ}{\sim}80^{\circ}$의 높은 이방성 식각을 갖는 ZnO 박막의 식각이 20% $Cl_2$ 가스의 농도, 1000 W의 coil rf power, 400 V의 dc-bias 전압, 그리고 5 mTorr의 공정 압력에서 성공적으로 이루어졌다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제8권3호
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• pp.244-250
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• 2008

An inductively coupled plasma etching process to replace an existing slower rate reactive ion etching process for $60{\mu}m$ diameter via-holes using Cl2/BCl3 gases has been investigated. Process pressure and platen power were varied at a constant ICP coil power to reproduce the RIE etched $200{\mu}m$ deep via profile, at high etch rate. Desired etch profile was obtained at 40 m Torr pressure, 950 W coil power, 90W platen power with an etch rate ${\sim}4{\mu}m$/min and via etch yield >90% over a 3-inch wafer, using $24{\mu}m$ thick photoresist mask. The etch uniformity and reproducibility obtained for the process were better than 4%. The metallized via-hole dc resistance measured was ${\sim}0.5{\Omega}$ and via inductance value measured was $\sim$83 pH.