• Journal of the Microelectronics and Packaging Society
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• v.16 no.2
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• pp.21-25
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• 2009

The organic-inorganic thin film transistors (OITFTs) with ZnO channel layer and the cross-linked PVP (Poly-4-vinylphenol) gate insulator were fabricated on the patterned ITO gate/glass substrate. ZnO channel layer was deposited by using atomic layer deposition (ALD). In order to improve the electrical properties, $O_2$ plasma treatment onto PVP film was introduced and investigated the effect of the plasma treatments on the electrical properties of the OITFTs. The field effect mobility and sub-threshold slope (SS) values of the OITFT decreased slightly from 0.24 to 0.16 $cm^2/V{\cdot}s$ and from 9.7 to 9.2 V/dec, respectively with increasing RF power from 30 to 50 Watt. The $I_{on/off}$ ratio was about $10^3$ for all samples with $O_2$ plasma treatment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.378-384
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• 2003

Etching species in CF$_4$/Ar plasma and the behavior of etching rate of Bi$_4$-$_{x}$L$_{x}$rTi$_3$O$_2$ (BLT) films were investigated in inductively coupled plasma (ICP) reactor in terms of etch parameters. The etching rate as functions of CF$_4$ contents showed the maximum 803 $\AA$/min at 20% CF$_4$ addition in CF$_4$/Ar plasma. The increase of RF power and DC bias voltage caused to an increase of etch rate. The variation of relative volume densities for F and he atoms were measured with the optical emission spectroscopy (OES). The chemical states of BLT were investigated with using X-ray photoelectron spectroscopy (XPS). XPS narrow scan analysis shows that La-fluorides remained on the etched surface. The presence of maximum etch rate at CF$_4$(20%)/Ar(80%) may be explained by the concurrence of two etching mechanisms such as physical sputtering and chemical reaction. The roles of he ion bombardment include destruction of metal (Bi, La, Ti)-O bonds as well as assistant for chemical reaction of metals with fluorine atoms.oms.

• Journal of Sensor Science and Technology
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• v.20 no.2
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• pp.131-136
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• 2011

In this study, a compact wireless vibration measurement system was developed using a 3-axial accelerometer in order to evaluate the vibration stimulation system. A low power microprocessor chip integrated with 2.4 GHz RF transceiver was used for the wireless data communication. To evaluate the system, the frequencies and accelerations from the vibration stimulation system were measured using an LVDT sensor and a vibration measurement system. The average frequency difference by the measurement system was less than 0.1 Hz, and the standard deviation of frequencies estimated by the LVDT sensor and the accelerometer was below 0.08 Hz. The developed system was applied to access a vibration stimulation system for the future study. The average acceleration difference of the central and peripheral point of the stimulation system was less than 0.0005 g(1 g=9.8 $m/s^2$), and the standard deviation of the acceleration was below 0.004 g, which shows the usefulness of the wireless vibration measurement system.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.75-81
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• 2012

This study is to design the transmitter and receiver of short range UWB(Ultra Wide Band) imaging radar that is able to display high resolution radar image for front area of a UGV(Unmanned Ground Vehicle). This radar can help a UGV to navigate autonomously as it detects and avoids obstacles through foliage. The transmitter needs two transmitters to improve the azimuth resolution. Multi-channel receivers are required to synthesize radar image. Transmitter consists of high power amplifier, channel selection switch, and waveform generator. Receiver is composed of sixteen channel receivers, receiver channel converter, and frequency down converter, Before manufacturing it, the proposed architecture of transceiver is proved by modeling and simulation using several parameters. Then, it was manufactured by using industrial RF(Radio Frequency) components and all other measured parameters in the specification were satisfied as well.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1654-1659
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• 2014

Tunneling field-effect transistors (TFETs) are very applicable to low standby-power application by their virtues of low off-current ($I_{off}$) and small subthreshold swing (S). However, low on-current ($I_{on}$) of silicon-based TFETs has been pointed out as a drawback. To improve $I_{on}$ of TFET, a gate-all-around (GAA) TFET based on III-V compound semiconductor with InAs/InGaAs/InP multiple-heterojunction structure is proposed and investigated. Its performances have been evaluated with the gallium (Ga) composition (x) for $In_{1-x}Ga_xAs$ in the channel region. According to the simulation results for $I_{on}$, $I_{off}$, S, and on/off current ratio ($I_{on}/I_{off}$), the device adopting $In_{0.53}Ga_{0.47}As$ channel showed the optimum direct-current (DC) performance, as a result of controlling the Ga fraction. By introducing an n-type InGaAs thin layer near the source end, improved DC characteristics and radio-frequency (RF) performances were obtained due to boosted band-to-band (BTB) tunneling efficiency.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.141-147
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• 2008

This paper describes the design of frequency down converting Mixer in the receiver to use compound semiconductor and CMOS product process. The basic theory and structure of frequency down converting Mixer is surveyed, and we design mixer circuit with active balun which use the compound semiconductor and CMOS process. This mixer convert a single ended signal to differential signal at input port of RF and LO instead of matching circuit to get dual band balanced mixer structure and characteristic broadband. This designed mixer has a conversion gain $-1{\sim}-6[dB]$ at $2{\sim}6[GHz]$ bandwidths. However, the simulation of the designed mixer with active balun has the result of a 7[dB] conversion gain for -2[dBm] LO input power and -10[dBm] input P1[dB] at 5.8[GHz].

• Journal of the Korean institute of surface engineering
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• v.34 no.1
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• pp.10-16
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• 2001

Recently plasma etching research has been focused on the metal surfaces in the nuclear industry. In this study, surface etching reaction of metallic Co and Mo, principal contaminants in the spent nuclear components, in CF$_4$/O$_2$, gas plasma has been experimentally investigated to look into the applicability and the effectiveness of the technique for the surface decontamination. Experimental variables are $CF_4$/$O_2$ ratio and substrate temperature between 29$0^{\circ}C$ and 38$0^{\circ}C$. Experimental results Show that the optimum gas composition is 80%CF$_4$-20%$O_2$ and the metallic Co and Mo are etched out well enough in the temperatures range. Cobalt starts to be etched above $350^{\circ}C$ and the etching rate increases with increasing substrate temperature. Maximum rate achieved at 38$0^{\circ}C$ under 220 W r.f. plasma power is 0.06 $\mu\textrm{m}$/min. On the other hand, the metallic Mo is etched easily even at low temperature and the reaction rate drastically increases as the substrate temperature goes up. Highest rate obtained under the same conditions is $1.9\mu\textrm{m}$/min. OES (Optical Emission Spectroscopy) analysis reveals that the intensities of F atom and CO molecule reach maximum at the optimum gas composition, which demonstrates that the principal reaction mechanism is fluorination and/or carbonyl reaction. It is confirmed, therefore, that dry processing technique using reactive plasma is quite feasible and applicable for the decontamination of surface-contaminated parts or equipments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.11
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• pp.902-905
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• 2012

This study is explore the photoelectric conversion change of dye-sensitized solar cells with surface treatment of the conductive substrate. gases of FTO surface treatment were $N_2$, and $O_2$. Treatment conditions of surface were gas flux from 25 sccm to 50 sccm and RF power were from 25 W to 50 W. Treatment time and pressure were fixed 5 min and 100 mtoor. The best sheet resistance and surface roughness were obtained by $O_2$ 50 sccm and 50 W and that result were 7.643 ${\Omega}/cm^2$ and 17.113 nm, respectively. The best efficiency result was obtained by $O_2$ 50 sccm and 50 W and that result of Voc, Jsc, FF and efficiency were 7.03 V, 14.88 $mA/cm^2$, 63.75% and 6.67%, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.142-142
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• 2010

본 논문은 단결정 및 다결정 실리콘 기판 상에 아산화질소 플라즈마 처리를 통하여 형성한 초박형 실리콘 옥시나이트라이드 박막의 특성과 이의 어플리케이션에 관한 것이다. 초박형 절연막은 현재 다양한 전자소자의 제작과 특성 향상을 위하여 활용되고 있으나 일반적인 화학 기상 증착 방법으로는 균일도를 확보하기 어려운 문제점을 가지고 있다. 디스플레이의 구동소자로 활용되는 박막 트랜지스터의 특성 향상과 비휘발성 메모리 소자의 터널링 박막에 응용하기 위하여 초박형 실리콘 옥시나이트라이드 박막의 증착과 이의 특성을 분석하였고, 실제 어플리케이션에 적용하였다. 실리콘 산화막과 실리콘 계면상에 존재하는 질소는 터널링 전류와 결함 형성을 감소시키며, 벌크 내에 존재하는 질소는 단일 실리콘 산화막에 비해 더 두꺼운 박막을 커패시턴스의 감소없이 이용할 수 있는 장점이 있다. 아산화질소 플라즈마를 이용하여 활성화된 질소 및 산소 라디칼들이 실리콘 계면을 개질하여 초박형 실리콘 옥시나이트라이드 박막을 형성할 수 있다. 플라즈마 처리 시간과 RF power의 변화에 따라 형성된 실리콘 옥시나이트라이드 박막의 두께 및 광학적, 전기적 특성을 분석하였다. 아산화질소 플라즈마 처리 방법을 사용한 실리콘 옥시나이트라이드 박막을 시간과 박막 두께의 함수로 전환해보면 초기적으로 증착률이 높고 시간이 지남에 따라 두께 증가가 포화상태에 도달함을 확인할 수 있다. 아산화질소 플라즈마 처리 시간의 변화에 따라 형성된 박막의 전기적인 특성의 경우, 플라즈마 처리 시간이 짧은 실리콘 옥시나이트라이드 박막의 경우 전압의 변화에 따라 공핍영역에서의 기울기가 현저히 감소하며 이는 플라즈마에 의한 계면 손상으로 계면결합 전하량이 증가에 기인한 것으로 판단된다. 또한, 전류-전압 곡선을 활용하여 측정한 터널링 메카니즘은 2.3 nm 이하의 두께를 가진 실리콘 옥시나이트라이드 박막은 직접 터널링이 주도하며, 2.7 nm 이상의 두께를 가진 실리콘 옥시나이트라이드 박막은 F-N 터널링이 주도하고 있음을 확인할 수 있다. 결론적으로 실리콘 옥시나이트라이드 박막을 활용하여 전기적으로 안정한 박막트랜지스터를 제작할 수 있었으며, 2.5 nm 두께를 경계로 터널링 메커니즘이 변화하는 특성을 이용하여 전하 주입 및 기억 유지 특성이 효과적인 터널링 박막을 증착하였고, 이를 바탕으로 다결정 실리콘 비휘발성 메모리 소자를 제작하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.177-177
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• 2010

고효율 비정질 실리콘 박막 태양전지 제작을 위해서는 광파장대에서 optical confinement 능력을 최대화할 수 있는 기술이 필수적이다. 효율적인 photon trapping을 위해서는 back reflector를 사용하거나 전면전극인 투명전도성막의 표면에 요철을 형성하여 포획된 태양광의 내부 반사를 증가시키거나 전면 투명전극에서 반사를 감소시켜 태양광의 travel length를 증가시키는 방법이 일반적이며, 이를 통해 흡수층의 효율을 최대화할 수 있다. 이 중 전면전극으로 사용되는 투명전도성막은 불소가 도핑된 tin-oxide가 주로 사용되었으나, 최근 들어 Al이 도핑된 산화아연막을 이용한 비정질 실리콘 박막 태양전지 개발에 대한 연구도 활발히 진행되고 있다. 투명전극 증착후 표면의 유효면적을 증가시키기 위해 염산 용액을 이용하여 표면 텍스쳐링을 수행한다. 그후 흡수층인 p-i-n 층을 플라즈마 화학기상증착법을 이용하여 형성하는 것이 일반적이다. 이때 표면처리 된 투명전극은 수소플라즈마에 대해 특성이 변하지 않아야 고효율 비정질 실리콘 박막 태양전지 제조에 적용될 수 있다. 본 연구에서는 표면처리 된 AZO 투명전극의 수소플라즈마에 의한 특성 변화에 대해 고찰하였다. 먼저 AZO 투명전극은 스퍼터링 공정을 적용하여 $1\;{\mu}m$두께로 증착하였고, 0.5 wt%의 HCl 용액을 이용하여 습식 식각을 수행하였다. 수소플라즈마 처리 조건은 $H_2$ flow rate 30 sccm, working pressure 20 mtorr, RF power 300 W, Temp $60^{\circ}C$ 이며 3분간 진행하였다. 표면형상은 수소플라즈마 전 후에는 큰 차이를 보이지 않았으며 AZO의 grain size는 각각 220 nm, 210 nm로 관찰되었다. 투명전극의 가장 중요한 특성인 가시광선 영역에서의 투과도는 수소플라즈마 처리전에는 90 % 이상의 투과도를 보였으나, 수소플라즈마 처리 후에는 85 %로 약간 저하된 특성을 보였다. 그러나 이는 박막 태양전지용 전면전극으로 사용하기 위한 투과도인 80 % 이상을 만족하는 결과로, 비정질 박막 실리콘 태양전지 제작에 사용될 수 있다. 또 하나의 중요한 특성인 Haze factor 역시 수소플라즈마 처리 전 후 모두 10 이상의 값을 나타냈다. 하지만 고효율 실리콘 박막 태양전지에 적용하기 위해서는 Haze factor를 증가시키는 공정 개발에 대한 추가 연구가 필요하다.