Reliability improvement by the suppression of keyhole generation in W-plug vias

This paper describes a mechanism of failures in W-plug vias due to the keyhole generation, and presents the process conditions which enhance the reliability of W-plug vias. For a high aspect ratio via-hole, one of the limiting factors in the reliability of the W-plug is the generation of the keyholes. We have investigated the sensitivities of corresponding technologies and conditions to the generation of the keyholes during the plug process. They include deposition technologies of TiN and deposition conditions of W. Based on the SEM observation and the electromigration failure test, the process conditions of TiN and W have been optimized.     

Dynamic mechanical properties and morphology of sulfonated polystyrene ionomers neutralized with mixtures of various cations

Summary The effects of the addition of mixed cations to the acid form sulfonated styrene copolymers on their mechanical properties and morphology were investigated. It was found that the matrix T _g, does not Change with the type of cations. However, the Cluster T _g, ionic moduli, and the Position of the SAXS peak were affected by the type of cations. The decreasing trends of Cluster T _g with increasing the amount of cesium and zinc cations in Na/Cs, Bai Cs, and Ba/Zn mixtures, were explained on the basis of the considerations of the size, Charge, and type of cations, which alter the degree of clustering as weil as ion-hopping mechanism. Received: 7 October 2002/Revised Version: 13 December 2002/ Accepted: 14 December 2002 Correspondence to Joon-Seop Kim     

Characteristics of steam hydrogasification of wood using a micro-batch reactor

Hydrogasification of pinewood was studied in the presence of steam using a micro-batch reactor. A series of reaction experiments were performed at temperatures ranging from 873 to 1043 K, and pressures ranging from 5 to 35 bar. It was found that steam significantly increases not only the rate of the hydrogasification reaction but also the conversion of carbon into product gases. The enhancement of the formation of total carbon-containing gases (CH₄, CO, CO₂ and C₂+) by adding steam is estimated to be as high as 30 times greater compared to dry hydrogasification at 1043 K. Increased hydrogen pressure also enhanced methane formation in the product gas.     

Higher order eigenfields in mode II cracks under elastic-plastic deformation

The explicit formulation of theJ-integral and theM-integral is constructed in terms of the stress intensity factor and the higher order stress coefficients for Mode II cracks under small or large scale yielding. Furthermore, the stress intensity factor and the higher order stress coefficients as well are computed with the aid of the two-stateJ- and theM - integral, which is found to be accurate and efficient. It is found that the contribution from the higher order singularities to theJ - integral is closely related to the configuration of the plastic zone.     

Physical separation using an autogenous medium on coal

The dry beneficiation for 1–5 and 5–10-mm-size coal using an air table was investigated. Separation was conducted using autogenously formed media in the feed coal. The separation density was around 1.8–2.0 g/cm³ and the average Ep (Ecart Probability) value ranged from 0.08–0.1 for the 5–10-mm fraction, to around 0.1–0.12 for the 1–5-mm fraction. For the 5–10-mm fraction, the feed ash decreased from 44% to 8.4% in the clean coal product, with 89.5% ash rejection rate in the rejects. For the 1–5-mm fraction, the feed ash decreased from 33.7% to 9.4%, and the reject ash was 88.7%.     

Semi-transparent thin film solar cells by a solution process

Easily processed, low cost, and highly efficient solar cells are desirable for photovoltaic conversion of solar energy to electricity. We present the fabrication of precursor solution processed CuInGaS2 (CIGS) thin film solar cells on transparent indium tin oxide (ITO) substrates. The CIGS absorber film was prepared by a spin-coating method, followed by two successive heat treatment processes. The first annealing process was on a hot plate at 300 °C for 30 min in air to remove carbon impurities in the film; this was followed by a sulfurization process at 500 °C in an H₂S(1%)/Ar environment to form a polycrystalline CIGS film. The absorber film with an optical band-gap of 1.52 eV and a thickness of about 1.1 µm was successfully synthesized. Because of the usage of a transparent glass substrate, a bifacial CIGS thin film device could be achieved; its power conversion efficiency was measured to be 6.64% and 0.96% for front and rear illumination, respectively, under standard irradiation conditions.     

CuO formation control as a function of mixed ratio of Cu-free powders in the synthesis of YBCO superconductors on Cu substrates

YBa₂Cu₃O_x (Y123) superconducting films were fabricated on Cu substrates using a simple screen-printing method, from Cu-free powders (Y₂O₃ and BaCO₃). In the process, CuO, which causes superconducting properties of Y123 films to deteriorate, was formed on the film surface. By varying the atomic ratio of Y to Ba (Y:Ba = 1:1∼1:4), the ratio needed to prevent CuO formation was found for the film surface that had been heat-treated at 980^∘C for 17 s. The film, with the ratio of Y to Ba (Y:Ba = 1:1), is reheat-treated at 930^∘C for 9 min 30 s to form a superconducting Y123 phase. It was possible to prevent CuO formation by controlling the ratio of Cu-free powders in the mixture and to fabricate YBCO superconductors on Cu substrates using a two-step heat-treatment.     

Water extract of licorice (Glycyrrhiza uralensis Fisch.) Supplementation is related with decreased lipid peroxidation among healthy male smokers with glutathione-S-transferase M1 positive genotype

Recently, licorice (Glycyrrhiza uralensis Fisch., GU) has demonstrated significant in vitro and in vivo antioxidant properties. In this study, it was tested that a daily regimen of supplementation with water extract of GU would ameliorate oxidative stress and whether effects were modulated by the glutathion-S-transferase (GST) polymorphisms. Forty healthy male smokers aged 20–60 were divided evenly into 2 groups and given either 260 mL of GU extracted with hot water or 260 mL of oligosaccharide based placebo every day for 8 weeks without any change of usual food intake, and blood samples were drawn before and after the intervention. Eight weeks of GU supplementation significantly decreased plasma conjugated dienes (a maker for lipid peroxidation) in GSTM1 positive subjects, but not in the GSTM1 null genotype group. Our finding suggests that consumption of licorice water extract might be effectively decreasing lipid peroxidation in the subgroup of smokers who have GSTM1 gene.     

Efficiency improvement of polymer light-emitting diodes using a quantum dot interlayer between a hole transport layer and an emitting layer

The current efficiency of polymer light-emitting diodes (PLEDs) were improved using a quantum dot interlayer between a hole transport layer and an emitting layer. The quantum dot interlayer played a role of controlling the hole transport in the PLEDs and enhanced the charge balance in the emitting layer. The current efficiency of the PLEDs was increased by more than 20% by the quantum dot interlayer. In particular, the efficiency improvement was significant at high luminance due to reduced efficiency roll-off in the quantum dot-embedded PLEDs.