• Tribology and Lubricants
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• v.31 no.3
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• pp.79-85
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• 2015

RC delay is a critical issue for achieving high performance of ULSI devices. In order to minimize the RC delay time, we uses the CMP process to introduce high-conductivity Cu and low-k materials on the damascene. The low-k materials are generally soft and fragile, resulting in structure collapse during the conventional high-pressure CMP process. One troubleshooting method is electrochemical mechanical polishing (ECMP) which has the advantages of high removal rate, and low polishing pressure, resulting in a well-polished surface because of high removal rate, low polishing pressure, and well-polished surface, due to the electrochemical acceleration of the copper dissolution. This study analyzes an electrochemical state (active, passive, transpassive state) on a potentiodynamic curve using a three-electrode cell consisting of a working electrode (WE), counter electrode (CE), and reference electrode (RE) in a potentiostat to verify an electrochemical removal mechanism. This study also tries to find optimum conditions for ECMP through experimentation. Furthermore, during the low-pressure ECMP process, we investigate the effect of current density on surface roughness and removal rate through anodic oxidation, dissolution, and reaction with a chelating agent. In addition, according to the Faraday’s law, as the current density increases, the amount of oxidized and dissolved copper increases. Finally, we confirm that the surface roughness improves with polishing time, and the current decreases in this process.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.162-162
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• 2014

최근 들어 wearable computing에 대한 수요가 증가하면서 flexible device에 대한 연구가 활발히 진행되고 있다. 하지만, flexible device를 구현하기 위해서는 기판의 damage를 줄이기 위한 저온공정, device life-time 향상을 위한 passivation, 와이어 본딩 등 다양한 문제들이 해결 되어야 한다. 이러한 문제들 중, polymer 기판과 금속간의 접착력을 향상시키기 위해서 많은 연구자들은 기판의 표면에 adhesive layer를 도포하거나 금속잉크의 solvent를 변화시키는 등의 연구를 진행해왔다. 종래의 연구는 기존 device를 대체 할 수 있을 정도의 생산성과 polymer 기판에 대한 열 적인 손상 이 문제가 되었다. 종래의 문제를 해결하기 위하여 저온공정, in-line system이 가능한 준 준 대기압 플라즈마를 사용하였다. 본 연구에서는 금속잉크를 Ink-jet으로 jetting하여 와이어 본딩 하는 과정에서 전도성 ink의 선폭을 유지시키고 접착력을 향상하기 위하여 준 대기압 플라즈마 공정을 이용하여 이러한 문제점을 해결하고자 하였다. Polymer 기판 표면에 roughness를 만들기 위해 대략 수백 nm 크기를 갖는 graphene flake를 spray coating하여 마스크로 사용하고 준 대기압 플라즈마를 이용하여 표면을 식각 함으로써 roughness를 형성시켰다. 준 대기압 플라즈마를 발생시키기 위해 double discharge system에서 6 slm/1.5 slm (He/O2) gas composition을 하부 전극에 흘려보내고 60 kHz, 5 kV 파워를 인가하였다. 동시에 상부 전극에는 30 kHz, 5 kV 파워를 인가하여 110초 동안 표면 식각 공정을 진행하였다. Graphene flake mask가 coating되어 있는 유연기판을 산소 플라즈마 처리 한 후 물에 3초 동안 세척하여 표면에 남아있는 graphene flake를 제거하고 6 slm/0.3 slm (He/SF6)의 유량으로 주파수와 파워 모두 동일 조건으로 110초 동안 표면 처리를 하였다. Figure 1은 표면 개질 과정과 graphene flake를 mask로 사용하여 얻은 roughness 결과를 SEM을 이용하여 관찰한 결과이다. 이와 같이 실험한 결과 ink와 기판간의 접촉면적을 늘려주고 접촉 각을 조절하여 Wenzel model 을 형성 할 수 있는 표면 roughness를 생성하였고 표면의 화학적 결합을 C-F group으로 치환하여 표면의 물과 접촉각 이 $47^{\circ}$에서 $130^{\circ}$로 증가하는 것을 확인하였다.

• Journal of the Korean Vacuum Society
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• v.13 no.3
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• pp.120-126
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• 2004

A damage-reduced trench was investigated in view of the defect distribution along trench sidewall and bottom using high resolution transmission electron microscopy, which was formed by HBr plasma and additive gases in magnetically enhanced reactive ion etching system. Adding $O_2$ and other additive gases into HBr plasma makes it possible to eliminate sidewall undercut and lower surface roughness by forming the passivation layer of lateral etching. To reduce the RIE induced damage and obtain the fine shape trench corner rounding, we investigated the hydrogen annealing effect after trench formation. Silicon atomic migration on trench surfaces using high temperature hydrogen annealing was observed with atomic scale view. Migrated atoms on crystal surfaces formed specific crystal planes such as (111), (113) low index planes, instead of fully rounded comers to reduce the overall surface energy. We could observe the buildup of migrated atoms against the oxide mask, which originated from the surface migration of silicon atoms. Using this hydrogen annealing, more uniform thermal oxide could be grown on trench surfaces, suitable for the improvement of oxide breakdown.

• Korean Journal of Materials Research
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• v.6 no.12
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• pp.1270-1278
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• 1996

고진공하에서 벽개된 GaAs를 대기중 노출시킨후, 결합상태 및 조성의 변화를 정량적으로 연구하여 Ga의 우선적 산화경향 및 결합의 붕괴에 기인한 원소상태 Ga 및 As의 생성을 관찰하였다. 대기중 노출시, 초기 Ga/As 비(=0.01)는 Ga의 우선적 산화에 의해 증가하였으며 원소상태 As의 증가와 더불어 일정값(=1.25)으로 유지되었다. 습식세정된 GaAs와 유황처리된 (S-passivated)GaAs를 각각 대기중에 노출시켜, 각각의 표면상태 변화를 비교, 관찰하였다. 유황처리된 GaAs는 습식세정처리만한 GaAs에 비해 산화막 성장이 크게 억제되었고, 이는 (NH4)2Sx 용액 처리로 형성된 Ga-S 및 As-S 겹합의 표면보호 효과에 기인한 것이다. 특히 대기중 노출에 따른 유황처리된 GaAs 표면조성 및 결합상태 변화의 정량적 관찰을 통하여, 유황보호막(S-passivation layer) 및 GaAs 표면과 대기중 산소와의 반응 기구를 규명할 수 있었다. 대기중 노출에 따라, 표면의 Ga-S 및 As-S 결합은 대기중 산소와 반응하여 점차 붕괴, 감소하는 경향을 나타냈으며, 이와 동시에 unpassivated 상태의 GaAs가 산소와 반응하여 Ga-O 결합을 형성함을 관찰할 수 있었다. 본 연구에서는 X-선 광전자 분광기를 사용하여 GaAs 표면 조성 및 결합상태의 변화를 관찰하였다.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.77-80
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• 2003

Adsorption of glycine on$Si_3N_4$powder surface has been investigated, which is supposed to enhance the formation of passive layer inhibiting oxidation in aqueous solution. In the basic solution, multinuclear surface complexing between Si and dissociated ligands was responsible for the saturated adsorption of glycine. In addition, $CeO_2$-based CMP slurry containing glycine was manufactured and then applied to planarize$SiO_2$and$Si_3N_4$thin film. Owing to the passivation by glycine, the removal rates, Rh, were decreased, however, the selectivities, RE(SiO$_2$)/RR($Si_3N_4$), increased and showed maximum at pH=12. The suppressed oxidation and dissolution by adsorbate were correlated with the dissociation behavior of glycine at different pH and subsequent chemical adsorption.

• Journal of the Korean Solar Energy Society
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• v.33 no.2
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• pp.11-17
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• 2013

Silicon nitride($SiN_x:H$) deposited by radio frequency plasma enhanced chemical vapor deposition(RF-PECVD) is commonly used for anti-reflection coating and passivation in crystalline silicon solar cell fabrication. In this paper, characteristics of the deposited silicon nitride was studied with change of working pressure, deposition temperature, gas ratio of $NH_3$ and $SiH_4$, and RF power during deposition. The deposition rate, refractive index and effective lifetime were analyzed. The (100) p-type silicon wafers with one-side polished, $660-690{\mu}m$, and resistivity $1-10{\Omega}{\cdot}cm$ were used. As a result, when the working pressure increased, the deposition rate of SiNx was increased while the effective life time for the $SiN_x$-deposited wafer was decreased. The result regarding deposition temperature, gas ratio and RF power changes would be explained in detail below. In this paper, the optimized condition in silicon nitride deposition for silicon solar cell was obtained as 1.0 Torr for the working pressure, $400^{\circ}C$ for deposition temperature, 500 W for RF power and 0.88 for $NH_3/SiH_4$ gas ratio. The silicon nitride layer deposited in this condition showed the effective life time of > $1400{\mu}s$ and the surface recombination rate of 25 cm/s. The crystalline silicon solar cell fabricated with this SiNx coating showed 18.1% conversion efficiency.

• Journal of the Optical Society of Korea
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• v.9 no.1
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• pp.16-21
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• 2005

Using a cantilever type nanoprobe having a 100㎚m aperture at the apex of the pyramidal tip of a near-field scanning optical microscope (NSOM), nanopatterning of polymer films are conducted. Two different types of polymer, namely a positive photoresist (DPR-i5500) and an azopolymer (Poly disperse orange-3), spincoated on a silicon wafer are used as the substrate. A He-Cd laser with a wavelength of 442㎚ is employed as the illumination source. The optical near-field produced at the tip of the nanoprobe induces a photochemical reaction on the irradiated region, leading to the fabrication of nanostructures below the diffraction limit of the laser light. By controlling the process parameters properly, nanopatterns as small as 100㎚ are produced on both the photoresist and azopolymer samples. The shape and size variations of the nanopatterns are examined with respect to the key process parameters such as laser beam power, irradiation time or scanning speed of the probe, operation modes of the NSOM (DC and AC modes), etc. The characteristic features during the fabrication of ordered structures such as dot or line arrays using NSOM lithography are investigated. Not only the direct writing of nano array structures on the polymer films but also the fabrication of NSOM-written patterns on the silicon substrate were investigated by introducing a passivation layer over the silicon surface. Possible application of thereby developed NSOM lithography technology to the fabrication of data storage is discussed.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.28-32
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• 1998

The electrochemical behavior of film and charge-discharge capacity of Li-ion cell in 1 M $LiPF_6/EC:DME$ (1 : 1, by volume ratio) electrolyte solution was studied using chronopotentiometry, cyclic voltammetry, chronoamperometry, and impedance spectroscopy. The first irreversible capacity was higher than the second irrversible capacity because of solvent decomposition. Especially, passivation film that is electron insulating and ionic conducting were formed on the MPCF by solvent decomposition during the first charge. The solvated Li is co-intercalated with solvent into MPCF electrode. Part of the MPCF is expoliated during co-intercalation of solvent-Li. The MPCF ends up nonuniformly covered by a relatively thick layer of exfoliated particles embedded in a matrix of product by solvent decomposition.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.148-154
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• 2010

We have fabricated $SiO_2$ oxidation thin films by TCP-CVD (transformer coupled plasma chemical vapor deposition) method for passivation layer of OLED (organic light emitting diode). The purpose of this paper is to control and estimate the deposition rate and refracive index characteristics with process parameters. They are power, gas condition, distance of source and substrate and process temperature. The results show that transmittance of thin films is over 90%, rapid deposition rate and stable reflective index from 1.4 to 1.5 at controled process conditions. They are $SiH_4$ : $O_2$ = 30 : 60 [sccm] gas condition, 70 [mm] distance of source and substrate, no-biased substrate and under 80 [$^{\circ}C$] process temperature.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.650-656
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• 1995

High frequency SAW filters for cellular communications were fabricated by metallizing 36$^{\circ}$Y-X LiTaO$_3$piezoelectric substrate with IIDT type electrodes. It was found that the center frequency of the filter was lowered than as designed. In order to overcome such a drawback and enable a fine tuning of its center frequency, dielectric SiN$_{x}$ thin films were deposited on LiTaO$_3$substrate by PECVD as passivation layer and then frequency responses were also characterized. As a result, the center frequency of the filter could be shifted to a higher frequency with increasing the thickness of SiN$_{x}$ film, because SAW velocity increased with increasing the ratio of the thickness of dielectric thin film to wavelength. The insertion loss of the filter, however, became larger with increasing the thickness of SiN$_{x}$ film.