Search

Pattern collapse, also as known as leaning, has become one of the most common and challengeable defects in semiconductor manufacturing process due to device shrinkage. In single wafer wet cleaning, Isopropyl Alcohol (IPA) rinse is widely used after Deionized Water (DIW) rinse. Fingering instabilities are observed at the mixing boundary of IPA and DIW, where dry spots are formed due to unbalanced capillary force amid patterns. Unlike previous DRAM devices, we have found that recent 1x-nm DRAM devices have become more vulnerable to pattern collapse induced by dry spots related to fingering instability. In this paper, we examine factors and phenomenon related to fingering-induced leaning through both experiments and simulation analysis. In addition, we also propose improved rinsing methods which could prevent fingering and related pattern collapse by adjusting nozzle configurations (i.e. speed, flow rate and etc.).

AbstractEndophytic fungi occupy inner plant tissues, which results in various interactions between the fungus and host. Studies on endophytic fungi have been conducted in Korea for over 30 years. This paper summarizes the published results of those studies. The endophytic fungi of approximately 132 plant species in Korea have been studied since the 1990s, resulting in over 118 publications. The host plants featured in these studies comprised 3 species of mosses, 34 species of woody plants, and 95 species of herbaceous plants. At the family level, the most studied plants were members of the Poaceae family, covering 18 species. Regionally, these studies were conducted throughout Korea, but over half of the studies were conducted in Gyeongsangbuk-do, Gangwon-do, and Chungcheongnam-do. Relatively few studies have been conducted in a metropolis such as Seoul. We confirmed 5 phyla, 16 classes, 49 orders, 135 families, 305 genera, and 855 taxa of endophytic fungi, excluding Incertae sedis, whose relationship with others are unknown. Most of the endophytic fungi belonged to Ascomycota (93.2%), and a few belonged to Basidiomycota (3.6%). Since the diversity of endophytic fungi differs depending on the host plant, plant tissue, and distribution region, future studies should be conducted on multiple host plants and in various regions. Future studies on endophytic fungi are expected to broaden, including genomics and taxonomic and ecological studies of secondary metabolites.

A more in-depth study was conducted on silicon nitride thin films deposited using the space-divided plasma enhance atomic layer deposition (PE-ALD) method. Existing silicon nitride thin films are fabricated using thermal chemical vapor deposition (CVD) at high temperatures of 700 °C or higher with carbon (C)- and chlorine (Cl)-based precursors. However, the high process temperature and the high concentration of C and Cl in films cause a slew of issues for semiconductor integration. In this study, the silicon–nitride thin films have been deposited using the PE-ALD method and an iodine-based precursor to solve these problems. NH3and N2gases were used as the reactant gases. When N2was used as the reactant gas instead of NH3, the concentration of the hydrogen (H) impurity was reduced from 19 to 15%. A plasma treatment was used to improve the density and remove the impurities in the thin films; the density of the thin films was confirmed to be 3.21 g/cm3, and the H concentration was 11%, indicating that the properties had improved. When a small amount of He gas was added to N2, the step coverage properties were improved up to 99.2%. The results of this study confirmed that silicon nitride thin films having superior properties can be produced using iodine-based precursors.

A space-divided plasma-enhanced atomic layer deposition (PE-ALD) system in which disk and wafer rotate at the same time was developed. In the space-divided PE-ALD system, the disk and the wafer are each independently rotated and deposited. It has the advantage that high productivity and dispersion can be improved by controlling the rotation speed of the disk and wafer. Also, it can be applied to various processes by changing the design of the upper lid slightly.In this study, a study on the deposition characteristics of SiO2thin films was conducted using the developed spatially divided PE-ALD system. The effect of the rotation speed of the disk and wafer on the deposition rate and the uniformity characteristics of the SiO2thin film was confirmed, and a study on the correlation with the wet etch rate was conducted.

Polyethylene, as the predominant polymer produced globally, poses significant environmental challenges due to its resistance to natural decomposition. In this study, we introduce an innovative chemicalbiological approach for transforming waste polyethylene into valuable biosurfactants. Our method involves hydrogenolysis using specially designed Ru/CeO2catalysts, which efficiently convert polyethylene into alkanes while keeping methane selectivity below 5%. This optimization ensures maximum feed availability for subsequent microbial processes. Notably, the produced chemical intermediates are directly utilized in the biological phase, eliminating the need for intermediate processing. Gordoniasp. JW21, selected for its exceptional alkane degradation capabilities, efficiently metabolizes a wide range of alkane structures, including extended alkyl chains. The microbial process culminates in the generation of high-value biosurfactants. This synergistic strategy not only offers an effective solution for polyethylene waste management but also sets a precedent for the sustainable production of biosurfactants.

Developing efficient conversion technologies for waste valorization is crucial in the context of a sustainable bioeconomy. The massive generation of spent coffee grounds (SCG) has become an environmental and social concern. Although the majority of SCG is underutilized, it exhibits the potential to be converted into value-added products. Herein, we report the effective production of lactic acid (LA), a precursor of polylactic acid, from SCG through catalytic upcycling using an erbium triflate catalyst. The reaction conditions, including time, temperature, and catalyst loading, were optimized to maximize the LA yield. The proposed strategy converted SCG into LA with a high yield (70 mol%) within 1 h. The morphology and chemical structure of SCG were investigated. Additionally, a techno-economic analysis (TEA) was conducted, which demonstrated that an economically viable catalytic upcycling strategy can enhance the efficiency of the waste valorization process.

We investigate the effect of current injection during contact formation of an Ag-based screen-printed electrode to boron-doped emitters, which differ by their sheet resistances. The average contact resistivities between the metal electrode and silicon of all the boron-doped emitter samples are ∼3 mΩ cm2, regardless of the sheet resistance (75–145 Ω/sq), and the lowest values are below 1 mΩ cm2 using the injection of a current density of 5 A/cm2 during the metallization process. Additionally, the injection of current to a phosphorus-doped emitter in the opposite direction suppressed the formation of the Ag precipitates and crystallites and increased the contact resistivity of over 300 mΩ cm2, which is comparable to that obtained when Ag paste is applied to a boron-doped emitter with no current injection. This finding indicates that electrons are essential for the reduction of Ag ions during high-temperature metallization process using the screen-printing technique and that the injection of current can control the contact formation and enhance the efficiency of solar cells. Finally, we suggest a suitable process for reducing the contact resistivity in manufacturing n-type Si solar cells.

Mongolian oak (MO), a lignocellulosic biomass feedstock comprising lignin, hemicellulose, and cellulose, was fractionated via reductive catalytic fractionation (RCF) into holocellulose-rich solid residue and lignin-derived phenol-rich liquid oil. To achieve an economically feasible RCF process, tungstate-zirconia (WZr)-supported metal catalysts, exhibiting bifunctionalities of hydrogen-adsorbing metal and acidic WZr, were used for depolymerizing and valorizing lignocellulose, and their catalytic activity was found to be highly dependent on the deposited metal. Ru/WZr exhibited excellent fractioning ability, achieving a maximum yield of 23.6 wt% of monomeric and dimeric compounds from MO and exhibiting the potential to be techno-economically viable. The superior activity of Ru/WZr can be attributed to the synergistic effects of metal and acid, which were studied by investigating the product distributions of aromatic small molecules depending on the properties of WZr-supported metal catalysts. The stabilization of reactive radical intermediates depending on the surface Brønsted acidity of acid catalysts and hydrogen-adsorbing ability of metals were also investigated. RCF reaction conditions were optimized for the maximum yield of monomeric compounds, which can be beneficial for the further development of industrial processes.

Polymethylmethacrylate powders are commonly used to improve the spreadability and blurring effects of powder foundation cosmetics. In this study, the opacity and haze effect of four types of polymethylmethacrylate powders and their 10wt% powder foundation formulation was evaluated. The distorted random hemispherical particulates with both concave and convex portions showed the highest haze and opacity value as a single powder substance. And as a formulated phase, the powder foundation formulation containing particulates with fine pores provided the highest haze and opacity value. We also examined the quantity of reflected light over the angular range 20-75° by polarized light goniophotometry. The total reflected light intensity, surface-reflected light, and internally reflected light were characterized. These studies demonstrated that hemispherical PMMA powders produce natural brilliance by creating high internally reflected light which is similar to the total reflection profile of artificial skin.

Vibration in a driveline is presented in this paper. In the experiment, the rear subframe and propeller shafts and axle were composed and mounted with rubber each other. For applying the vibration input instead of the torsional vibration effect of an engine, the shaker was taken. In particular, torsional vibration due to fluctuating forced vibration excitation across the joint between driveline and rear subframe was carefully examined. Accordingly, the joint response was checked from experiments and the FE-simulation using FRF (frequency response function) analysis was performed. All test results were signal processed and validated against numerical simulations. In present study, the new test bench for measuring the vibration signal and simulating the vehicle chassis system was proposed. The modal value and the mode shape of components were analyzed using the model to identify the important components affecting driveline noise and vibration. It could be reached that the simplified test bench could be well established and be used for design guide and development of the vehicle chassis components.

Methane conversion using an electric discharge has been studied for many years. Recently, many research groups have developed high-frequency pulsed plasma reaction for methane conversion to higher hydrocarbons and synthesis gas. CO2reforming of methane to synthesis gas has also attracted considerable interest as a method of utilization of the greenhouse gases, CO2and CH4, which occupy most of man-made greenhouse gases. In this study, the influence of pulse form of applied voltage on methane and carbon dioxide conversions and product selectivity has been investigated using a cylindrical type DBD reactor. For this purpose, two kinds of power supply were compared, that is, AC power supply which has a high-frequency sinusoidal wave form, and AC pulse power supply which has modified AC pulse wave form. The conversions of methane and carbon dioxide were enhanced using pulsed plasma. The lower pulse width was more profitable economically.

Objectives: Although musculoskeletal disorders (MSD) represent a significant occupational issue for most nursing home staff, few epidemiological studies have been conducted in Korea. Methods: We investigated the prevalence of, and risk factors for, MSD within South Korea’s largest nursing home using a previously validated, self-reporting questionnaire. Results: From a total of 130 registered employees, 91 (70.0%) successfully completed questionnaires were obtained. The majority were female (80.2%, n=73), with an age range of 27 to 62 years and an average age of 47.0 years (SD 8.0). MSD occurred in varying amounts and was classified into distinct categories depending on body site. The most commonly affected region was the shoulder (reported by 35.2%), followed by the arm (22.0%), knee (20.9%) and lower back (19.8%). Three statistically significant risk factors were consistently identified among all 4 MSD sites: manually handling patients (OR 5.1 to 20.8), changing a patient’s clothes (OR 6.7 to 30.1) and working as a nursing aide (OR 3.7 to 74.3). Conclusions: Overall, the present results suggest that employment within a South Korean nursing home incurs certain hazards depending on job description and daily work tasks. The MSD prevalence differed from other occupations within South Korea and previous nursing home studies.

We report a case of a 3-year-old boy with hemophagocytic lymphohistiocytosis (HLH), with enlarged cervical lymph nodes causing internal jugular vein compression, who initially presented a condition similar to the superior vena cava syndrome. Laboratory data along with neck node and bone marrow biopsies confirmed the HLH. Genetic analysis revealed the patient to be compound heterozygous for 2 variations of the perforin gene, c.1620 A>G and c.562C>G. This case featuring a rare initial manifestation of HLH that has not been previously reported, points to the necessity of considering this disease when symptoms similar to superior vena cava syndrome are encountered.