• 한국전기전자재료학회논문지
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• 제21권4호
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• pp.305-310
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• 2008

Deep trench etching of silicon was investigated as a function of RF source power, DC bias voltage, $C_4F_8$ gas flow rate, and $O_2$ gas addition. On increasing the RF source power from 300 W to 700 W, the etch rate was increased from $3.52{\mu}m/min$ to $7.07{\mu}m/min$. The addition of $O_2$ gas improved the etch rate and the selectivity. The highest etch rate is achieved at the $O_2$ gas addition of 12 %, The selectivity to PR was 65.75 with $O_2$ gas addition of 24 %. At DC bias voltage of -40 V and $C_4F_8$ gas flow rate of 30 seem, We were able to achieve etch rate as high as $5.25{\mu}m/min$ with good etch profile.

• 한국전기전자재료학회논문지
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• 제24권9호
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• pp.718-722
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• 2011

In this work, we investigated to the etching characteristics of the TiN thin film in He/$BCl_3/Cl_2$ plasma. The etch rate was measured by the gas mixing ratio, the RF power, the DC bias voltage and the process pressure. The maximum etch rate in He/$BCl_3/Cl_2$ plasma was 59 nm/min. The etch rate increased as the RF power and the DC-bias voltage was increased. The chemical reaction on the surface of the etched the TiN thin films was investigated with X-ray photoelectron spectroscopy (XPS). The intensity of Ti 2p and N 1s peaks are varied during etching process. A new peak was appeared in He/$BCl_3/Cl_2$ plasma. The new peak was revealed Ti-$Cl_x$ by Cl 2p peak of XPS wild scan spectra analysis.

• Transactions on Electrical and Electronic Materials
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• 제15권1호
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• pp.32-36
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• 2014

In this study, the etching characteristics of titanium dioxide ($TiO_2$) thin films were investigated with the addition of $N_2$ to CF4/Ar plasma. The crystal structure of the $TiO_2$ was amorphous. A maximum etch rate of 111.7 nm/min and selectivity of 0.37 were obtained in an $N_2/CF_4/Ar$ (= 6:16:4 sccm) gas mixture. The RF power was maintained at 700 W, the DC-bias voltage was - 150 V, and the process pressure was 2 Pa. In addition, the etch rate was measured as functions of the etching parameters, such as the gas mixture, RF power, DC-bias voltage, and process pressure. We used X-ray photoelectron spectroscopy to investigate the chemical state on the surface of the etched $TiO_2$ thin films. To determine the re-deposition and reorganization of residues on the surface, atomic force microscopy was used to examine the surface morphology and roughness of $TiO_2$ thin films.

• Journal of Advanced Marine Engineering and Technology
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• 제41권2호
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• pp.146-149
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• 2017

Si clusters generated during the plasma chemical vapor deposition (CVD) process have a great influence on the quality of the fabricated films. In particular, in hydrogenated amorphous silicon thin films (a-Si:H) used for thin film solar cells, Si clusters are mainly responsible for light-induced degradation. In this study, we investigated the amount of clusters incorporated into thin films using a quartz crystal microbalance (QCM) and specially designed cluster eliminating filters, and investigated the effect of the DC grid mesh in preventing cluster incorporation. Experimental results showed that as the applied voltage of the grid mesh, which is placed between the electrode and the QCM, decreased, the number of clusters incorporated into the film decreased. This is due to the electrostatic force from the grid mesh bias, and this method is expected to contribute to the fabrication of high-quality thin films by preventing Si cluster incorporation.

• 전자공학회논문지A
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• 제33A권10호
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• pp.139-143
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• 1996

We report on the static and dynamic characteristics of optically modulated resonant tunneling diode oscillator (RTDO) formed in double-barrier quantum-well structure. Under the illumination of Ti:Sapphire laser, the dc current-voltage (I-V) curves of RTDO shifted towared lower voltages. This characteristic was found to odify the series resistance, negtive differential resistance, capacitance, and the inductance of the RTDO. As a result, the resonant frequency of TRDO centered at 5.302 GHz was found to decrease about 20 MHz under the laser illumination. At a constnat bias voltage, the oscillation frequency decreased linearly as the laser power was increased.

• 한국진공학회지
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• 제6권2호
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• pp.136-142
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• 1997

An/n-GaAs(100) Schottky 장벽 diode를 제작하여 변조전압($V_{ac}$) 및 dc 바이어스 전 압($V_{bias}$) 변화에 따른 electroreflectance(ER)를 측정하였다. 관측된 Franz-Keldysh oscillation(FKO) 피크로부터 이 시료의 내부 전기장($E_i$)은 $5.76\times 10^{4}$V/cm였다. $V_{ac}$를 변화시 킴에 따라 ER신호의 모양은 변화가 없고, 진폭만 선형적으로 증가하였다. 순방향 및 역방향 의 $V_{bias}$변화에 따라 ER신호의 진폭은 감소하였으며, $V_{bias}$가 -5.0~0.6V로 증가함에 따라 Ei 는 $19.3\times 10^4\sim4.39\times10^4$V/cm로 감소하였다. 그리고 $V_{bias}$변화에 대한 $E_i^2$의 그래프로부터 built-in 전압(Vbi)은 0.70V였으며, 이 값은 $V_{bias}$변화에 따른 FKO피크의 진폭 관계 그래프 에서 얻은 결과와 잘 일치하였다. 또한 이 시료의 캐리어 농도(N)와 전위장벽($\Phi$)은 300K에 서 각각 $2.4\times 10^{16}\textrm{cm}^{-3}$와 0.78eV의 값을 얻었다.

• 한국정보통신학회논문지
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• 제16권10호
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• pp.2237-2246
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• 2012

본 논문에서는 구강센서를 소형화하고 제조 원가를 낮추기 위해 구강센서에서 필요로 하는 바이어스 회로를 구강센서 칩 내부에서 만들어주었다. 제안된 DC-DC 변환기 회로는 기준전류 발생기(reference current generator) 회로의 IREF를 이용하여 전압 레귤레이터(voltage regulator)에 필요한 기준전류와 바이어스 전류를 각각 공급해준다. 이들 전류가 각각의 전압 레귤레이 회로에서 해당되는 기준전압을 생성하여 부궤환(negative feedback)에 의해 목표전압을 regulation하게 된다. 그리고 기준전류가 전류 복사비(current mirror ratio)에 의해 mirroring되어 정전류인 IB0/IB1을 공급해주고, VREF 전압을 공급해주도록 설계하였다. $0.18{\mu}m$ X-ray CMOS 이미지 센서 공정을 이용하여 설계된 구강센서의 DC-DC 변환기의 출력 전압의 평균 전압, ${\sigma}$와 $4{\sigma}$는 양호한 측정 결과를 얻었다. 그리고 line-pair pattern 영상은 blurring 없이 높은 해상도 특성을 보였으며, 좋은 구강 영상을 획득하였다.

• 한국진공학회지
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• 제16권2호
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• pp.122-127
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• 2007

본 연구에서는 비정질 탄소박막들(a-C, a-C:H, a-C:N)을 흑연타겟이 부착되어진 비대칭 마그네트론 스퍼터링법을 이용하여 증착하였으며, 음의 DC 바이어스 전압의 효과를 알아보기 위해 증착가스 압력내에서 200 V를 인가하여 탄소박막들을 제작하였다. 수소화된 비정질 탄소박막과 질화탄소박막은 각각 스퍼터링 가스로써 아세틸렌과 질소를 주입하여 제작하였다. 결과적으로 26.5 GPa의 높은경도와 0.1 nm의 낮은 거칠기 그리고 접착력은 30.5 N를 가지는 수소화된 비정질 탄소박막을 합성하였으며, 32 N의 좋은 접착 특성을 나타내는 질화 탄소 박막을 합성하였다. 본 논문에서는 아세틸렌과 질소 가스의 효과와 음의 DC 바이어스 전압에 따른 비정질 탄소박막들의 구조적 특성과 물리적 특성과의 관계를 규명하였다.

• 전자공학회논문지D
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• 제36D권4호
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• pp.56-62
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• 1999

본 연구에서, (Ba,Sr)TiO\sub 3\ 박막이 rf 전력, dc 바이어스 전압 및 반응로 압력과 같은 식각 공정 변수를 변화하여 ICP에서 Cl\sub 2\Ar 가스 혼합비에 따라 식각되었다. 0.2의 Cl\sub 2\/(Cl\sub 2\+Ar) 가스 혼합비, 600 W의 rf 전력,250 V의 dc 바이어스 전압 및 5 mTorr의 반응로 압력의 공정 조건하에서 식각율은 56nm/min이었다. 이때 Pt, SiO\sub 2\ 막에 대한 BST 박막의 식각 선택비는 각각 0.52, 0.43이었다. 식각된 BST 박막의 표면반응은 XPS로 분석하였다. Ba는 BaCl\sub 2\ 와 같은 화학적인 반응과 물리적인 스퍼터링에 의해 제거되었다. Sr의 제거는 Sr과 Cl의 화확적인 반응보다 Ar 이온 충격이 더 효과적이었다. Ti는 TiCl\sub 4\ 와 같은 화학반응에 의해 용이하게 제거되었다. XPS 분석 결과를 비교하기 위하여 SIMS의 분석을 수행하여 비교한 결과 동일한 결론을 도출하였다.

• Journal of Power Electronics
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• 제17권1호
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• pp.222-231
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• 2017

In this paper, a new architecture for a cost-effective power conditioning systems (PCS) using a single-sourced asymmetric cascaded H-bridge multilevel inverter (MLI) for photovoltaic (PV) applications is proposed. The asymmetric MLI topology has a reduced number of parts compared to the symmetrical type for the same number of voltage level. However, the modulation index threshold related to the drop in the number of levels of the inverter output is higher than that of the symmetrical MLI. This problem results in a modulation index limitation which is relatively higher than that of the symmetrical MLI. Hence, an extra voltage pre-regulator becomes a necessary component in the PCS under a wide operating bias variation. In addition to pre-stage voltage regulation for the constant MLI dc-links, another auxiliary pre-regulator should provide isolation and voltage balance among the multiple H-bridge cells in the asymmetrical MLI as well as the symmetrical ones. The proposed PCS uses a single-ended DC-DC converter topology with a coupled inductor and charge-pump circuit to satisfy all of the aforementioned requirements. Since the proposed integrated-type voltage pre-regulator circuit uses only a single MOSFET switch and a single magnetic component, the size and cost of the PCS is an optimal trade-off. In addition, the voltage balance between the separate H-bridge cells is automatically maintained by the number of turns in the coupled inductor transformer regardless of the duty cycle, which eliminates the need for an extra voltage regulator for the auxiliary H-bridge in MLIs. The voltage balance is also maintained under the discontinuous conduction mode (DCM). Thus, the PCS is also operational during light load conditions. The proposed architecture can apply the module-integrated converter (MIC) concept to perform distributed MPPT. The proposed architecture is analyzed and verified for a 7-level asymmetric MLI, using simulation results and a hardware implementation.