• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.77.2-77.2
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• 2013

In this talk, I will briefly review recent results of my group related to application of atomic layer deposition (ALD) for fabricating environmental catalysts and organic solar cells. ALD was used for preparing thin films of TiO2 and NiO on mesporous silica with a mean pore size of 15 nm. Upon depositing TiO2 thin films of TiO2 using ALD, the mesoporous structure of the silica substrate was preserved to some extent. We show that efficiency for removing toluene by adsorption and catalytic oxidation is dependent of mean thickness of TiO2 deposited on silica, i.e., fine tuning of the thickness of thin film using ALD can be beneficial for preparing high-performing adsorbents and oxidation catalysts of volatile organic compound. NiO/silica system prepared by ALD was used for catalysts of chemical conversion of CO2. Here, NiO nanoparticles are well dispersed on silica and confiend in the pore, showing high catalytic activity and stability at 800oC for CO2 reforming of methane reaction. We also used ALD for surface modulation of buffer layers of organic solar cell. TiO2 and ZnO thin films were deposited on wet-chemically prepared ZnO ripple structures, and thin films with mean thickness of ~2 nm showed highest power conversion efficiency of organic solar cell. Moreover, performance of ALD-prepared organic solar cells were shown to be more stable than those without ALD. Thin films of oxides deposited on ZnO ripple buffer layer could heal defect sites of ZnO, which can act as recombination center of electrons and holes.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.75.2-75.2
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• 2013

Atomic layer deposition (ALD), utilizing self-limiting surface reactions, could offer promising perspectives for future efficient energy conversion devices. The capabilities of ALD for surface/interface modification and construction of novel architectures with sub-nanometer precision and exceptional conformality over high aspect ratio make it more valuable than any other deposition methods in nanoscale science and technology. In the context, a variety of researches on fabrication of active materials for energy conversion applications by ALD are emerging. Among those materials, one-dimensional nanotubular titanium dioxide, providing not only high specific surface area but also efficient carrier transport pathway, is a class of the most intensively explored materials for energy conversion systems, such as photovoltaic cells and photo/electrochemical devices. The monodisperse, stoichiometric, anatase, TiO2 nanotubes with smooth surface morphology and controlled wall thickness were fabricated via low-temperature template-directed ALD followed by subsequent annealing. The ALD-grown, anatase, TiO2 nanotubes in alumina template show unusual crystal growth behavior which allows to form remarkably large grains along axial direction over certain wall thickness. We also fabricated dye-sensitized solar cells (DSCs) introducing our anatase TiO2 nanotubes as photoanodes, and studied the effect of blocking layer, TiO2 thin films formed by ALD, on overall device efficiency. The photon convertsion efficiency ~7% were measured for our TiO2 nanotubebased DSCs with blocking layers, which is ~1% higher than ones without blocking layer. We also performed open circuit voltage decay measurement to estimate recombination rate in our cells, which is 3 times longer than conventional nanoparticulate photoanodes. The high efficiency of our ALD-grown, anatase, TiO2 nanotube-based DSCs may be attributed to both enhanced charge transport property of our TiO2 nanotubes photoanode and the suppression of recombination at the interface between transparent conducting electrode and iodine electrolytes by blocking layer.

• The Korea Journal of Herbology
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• v.38 no.1
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• pp.31-43
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• 2023

Objective : Alcoholic liver disease (ALD) is caused by excess alcohol intake. In the liver, alcohol breakdown results formation of toxic byproducts that lead to damage to tissue. This study is to investigate the therapeutic effects of Paeoniae Radix Alba and Puerariae Radix combination (PP) on ALD. Methods : PP was analyzed for polyphenolic compounds and free radical scavenging activity. ALD mouse model was induced by feeding ethanol and water (Control), silymarin (50 mg/kg), low-dose (PP: 100 mg/kg) or high-dose (PP: 200 mg/kg) was orally administrated to ALD mice for 14 days. The serum was assessed with levels of AST, ALT, total bilirubin, total cholesterol, and triglyceride. Liver tissues were evaluated for ROS levels, degree of liver damage and protein expression. Results : The 3:1 (Paeoniae Radix Alba:Puerariae Radix) ratio showed the best antioxidant values for the experiment. In ALD model, levels of AST, ALT, total bilirubin, total cholesterol, and triglyceride were significantly increased in the Control and the levels were decreased by treatment of PP. In addition, increased ROS, ONOO^- and MDA levels in the Control were reduced in the PP groups. Western blot analysis figured out that proteins related to ROS and cholesterol metabolism were higher in ALD than in PP-treated ALD. Antioxidant enzyme expression was low in the control group and increased by PP treatment. Conclusion : Our results suggest that PP has the potential to be a medicine in ALD in terms of regulating oxidative stress and adjusting lipid metabolism.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.860-863
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• 2007

ZnO nano film for transparent thin film transistors is prepared by injection type source delivery system of atomic layer deposition. By using this delivery system the source delivery pulse time can dramatically be reduced to 0.005s in ALD system. ZnO nanofilms obtained at $150^{\circ}C$ are characterized.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.239-240
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• 2008

As semiconductor devices are scaled down for better performance and more functionality, the Cu-based interconnects suffer from the increase of the resistivity of the Cu wires. The resistivity increase, which is attributed to the electron scattering from grain boundaries and interfaces, needs to be addressed in order to further scale down semiconductor devices [1]. The increase in the resistivity of the interconnect can be alleviated by increasing the grain size of electroplating (EP)-Cu or by modifying the Cu surface [1]. Another possible solution is to maximize the portion of the EP-Cu volume in the vias or damascene structures with the conformal diffusion barrier and seed layer by optimizing their deposition processes during Cu interconnect fabrication, which are currently ionized physical vapor deposition (IPVD)-based Ta/TaN bilayer and IPVD-Cu, respectively. The use of in-situ etching, during IPVD of the barrier or the seed layer, has been effective in enlarging the trench volume where the Cu is filled, resulting in improved reliability and performance of the Cu-based interconnect. However, the application of IPVD technology is expected to be limited eventually because of poor sidewall step coverage and the narrow top part of the damascene structures. Recently, Ru has been suggested as a diffusion barrier that is compatible with the direct plating of Cu [2-3]. A single-layer diffusion barrier for the direct plating of Cu is desirable to optimize the resistance of the Cu interconnects because it eliminates the Cu-seed layer. However, previous studies have shown that the Ru by itself is not a suitable diffusion barrier for Cu metallization [4-6]. Thus, the diffusion barrier performance of the Ru film should be improved in order for it to be successfully incorporated as a seed layer/barrier layer for the direct plating of Cu. The improvement of its barrier performance, by modifying the Ru microstructure from columnar to amorphous (by incorporating the N into Ru during PVD), has been previously reported [7]. Another approach for improving the barrier performance of the Ru film is to use Ru as a just seed layer and combine it with superior materials to function as a diffusion barrier against the Cu. A RulTaN bilayer prepared by PVD has recently been suggested as a seed layer/diffusion barrier for Cu. This bilayer was stable between the Cu and Si after annealing at $700^{\circ}C$ for I min [8]. Although these reports dealt with the possible applications of Ru for Cu metallization, cases where the Ru film was prepared by atomic layer deposition (ALD) have not been identified. These are important because of ALD's excellent conformality. In this study, a bilayer diffusion barrier of Ru/TaCN prepared by ALD was investigated. As the addition of the third element into the transition metal nitride disrupts the crystal lattice and leads to the formation of a stable ternary amorphous material, as indicated by Nicolet [9], ALD-TaCN is expected to improve the diffusion barrier performance of the ALD-Ru against Cu. Ru was deposited by a sequential supply of bis(ethylcyclopentadienyl)ruthenium [Ru$(EtCp)_2$] and $NH_3$plasma and TaCN by a sequential supply of $(NEt_2)_3Ta=Nbu^t$ (tert-butylimido-trisdiethylamido-tantalum, TBTDET) and $H_2$ plasma. Sheet resistance measurements, X-ray diffractometry (XRD), and Auger electron spectroscopy (AES) analysis showed that the bilayer diffusion barriers of ALD-Ru (12 nm)/ALD-TaCN (2 nm) and ALD-Ru (4nm)/ALD-TaCN (2 nm) prevented the Cu diffusion up to annealing temperatures of 600 and $550^{\circ}C$ for 30 min, respectively. This is found to be due to the excellent diffusion barrier performance of the ALD-TaCN film against the Cu, due to it having an amorphous structure. A 5-nm-thick ALD-TaCN film was even stable up to annealing at $650^{\circ}C$ between Cu and Si. Transmission electron microscopy (TEM) investigation combined with energy dispersive spectroscopy (EDS) analysis revealed that the ALD-Ru/ALD-TaCN diffusion barrier failed by the Cu diffusion through the bilayer into the Si substrate. This is due to the ALD-TaCN interlayer preventing the interfacial reaction between the Ru and Si.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.312.1-312.1
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• 2016

We have deposited ZnO thin films by ultraviolet (UV) enhanced atomic layer deposition using diethylznic (DEZ) and water (H2O) as precursors with UV light. The atomic layer deposition relies on alternating dose of the precursor on the surface and subsequent chemisorption of the precursors with self-limiting growth mechanism. Though ALD is useful to deposition conformal and precise thin film, the surface reactions of the atomic layer deposition are not completed at low temperature in many cases. In this experiment, we focused on the effects of UV radiation during the ALD process on the properties of the inorganic thin films. The surface reactions were found to be complementary enough to yield uniform inorganic thin films and fully react between DEZ and H2O at the low temperature by using UV irradiation. The UV light was effective to obtain conductive ZnO film. And the stability of TFT with UV-enhanced ZnO was improved than ZnO by thermal ALD method. High conductive UV-enhanced ZnO film have the potential to applicability of the transparent electrode.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.21-21
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• 2014

$CrN/Al_2O_3/CrN$ 다층 코팅을 HIPIMS와 ALD간 하이브리드 코팅법을 통해 형성하였다. ALD를 통해 CrN 층에 도입한 $Al2O_3$층의 두께 및 위치가 $CrN/Al_2O_3/CrN$ 다층 코팅층의 미세구조, 표면 거칠기, 기계적 특성 및 화학적 특성에 미치는 영향에 대해 조사하였다. 전체 공정시간은 거의 변화시키지 않고도, ALD를 이용한 $Al2O_3$층의 삽입에 의하여 기계적/화학적 특성이 크게 개선될 수 있음을 확인하였으며, 개선된 특성에 대한 원인에 대해 조사하였다.

• Journal of Powder Materials
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• v.25 no.1
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• pp.60-68
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• 2018

The design and fabrication of photoelectrochemical (PEC) electrodes for efficient water splitting is important for developing a sustainable hydrogen evolution system. Among various development approaches for PEC electrodes, the chemical vapor deposition method of atomic layer deposition (ALD), based on self-limiting surface reactions, has attracted attention because it allows precise thickness and composition control as well as conformal coating on various substrates. In this study, recent research progress in improving PEC performance using ALD coating methods is discussed, including 3D and heterojunction-structured PEC electrodes, ALD coatings of noble metals, and the use of sulfide materials as co-catalysts. The enhanced long-term stability of PEC cells by ALD-deposited protecting layers is also reviewed. ALD provides multiple routes to develop improved hydrogen evolution PEC cells.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.231-231
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• 2010

현재 Cu배선 제조공정에서 전해도금은 Damascene pattern의 Cu filling에 사용되고 있는데, 우수한 특성의 전해도금을 위해서는 step coverage가 우수한 Cu seed layer가 필수적이다. 현재까지 Cu seed layer를 형성하는 방법으로는 ionized physical vapor deposition(I-PVD)이 사용되고 있는데, 22 nm 이후의 소자에서는 step coverage의 한계로 인해 완벽한 Cu filling 어려울 것으로 예상된다. 본 연구에서는 step coverage가 매우 우수한 atomic layer deposition(ALD) 방법으로 Cu seed layer를 증착하고 그 특성을 기존의 PVD 박막과 비교하였다. Ketoiminate 계열의 +2가 Cu 전구체와 $H_2$를 이용하여 ALD Cu 박막을 증착하였는데 exposure, 기판의 온도를 변화시키면서 기판별로 ALD Cu의 최적공정조건을 도출하였다. ALD Cu seed와 PVD Cu seed 위에 약 $1{\mu}m$의 Cu 박막을 전해도금한 후 박막의 두께, 비저항, 미세구조와 함께 pattern filling 특성을 비교하였다.

• Current Applied Physics
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• v.18 no.11
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• pp.1436-1440
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• 2018

SiN and SiCN film production using plasma-enhanced atomic layer deposition (PE-ALD) is investigated in this study. A developed high-power and high-density multiple inductively coupled plasma (multi-ICP) source is used for a low temperature PE-ALD process. High plasma density and good uniformity are obtained by high power $N_2$ plasma discharge. Silicon nitride films are deposited on a 300-mm wafer using the PE-ALD method at low temperature. To analyze the quality of the SiN and SiCN films, the wet etch rate, refractive index, and growth rate of the thin films are measured. Experiments are performed by changing the applied power and the process temperature ($300-500^{\circ}C$).