발간논문

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Synchrotron radiation based total reflection X-ray fluorescence(SR-TXRF) has extremely low background signal. The detection limit can be lowered by minimizing background intensity. We show that the background intensity depends very much on the crystallographic orientation of Si wafer and the conditions that make the background intensity maximum are the one in which the diffracted X-rays from the wafer come into the Si(Li)detector. In our experiment, the background with maximum intensity was made at the azimuthal angle of 9.5˚ and 80.5˚. At that azimuthal angle, the diffracted X-rays from (113) and (113) planes come into the Si(Li)detector. And we investigate the mechanism how the diffracted X-rays which come into the Si(Li)detector make the background intensity maximum. When the diffracted X-rays from the wafer come into the detector, most of the photoelectron bremsstrahlung enters the detector and the background intensity becomes maximum. We calculate angular distribution of bremsstrahlung when diffracted X-rays come into the Si(Li)detector. By using the methods introduced in this thesis, the crystallographic orientation of Si wafer can be optimized in TXRF analysis.

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The effect of current wave forms on the Cu filling behavior during damascene plating was investigated. Direct current(DC) and pulsed current were used with the variation of the current densities from 1 A/d㎡ to 7 A/d㎡. Straight trenches having 0.25, 0.4 and 0.8 ㎛ width were plated. The cross-sectional images of the electroplated trenches were observed by field emission scanning electron microscope(FE-SEM). Trenches were successfully filled without any void for Cu lines of 0.4 and 0.8 ㎛ width under optimized current densities which were different with respective current wave forms. In case the plating condition was not optimized two types of void were observed : center voids and side wall voids. The formation of center voids was attributed to the fast copper deposition rate at top corner of the trench for DC plating and the fast copper deposition rate at the side wall for pulse plating. Side wall void was formed due to the corrosion of Cu seed layer during the over immersion of the wafer before plating.

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The changes in atomic bonding state at the interface of ultra thin Ni film (25 Å) with SiC were investigated as a function of annealing temperature using synchrotron radiation photoemission spectroscopy (SRPES). From these, the early stage in the reaction to form Ni silicide was examined. It was found that Ni_2Si began to form below 600℃. However, at 300℃ Ni atoms migrated on the surface of SiC, leading to the formation of Ni islands and the substrate is partially exposed, prior to the formation of Ni silicide. When Ni_2Si was formed, the binding energy of SiC bond was not changed, but work function of the contact layer was increased. This provides the evidence that Schottky barrier height was increased with the formation of Ni silicide via the increase in work function of contact layer.

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Plasma treatment was applied to remove the surface oxide of Sn-3.5 mass%Ag solder bump for fluxless flip chip bonding. The effects of plasma process parameters, such as plasma power, treatment time, chamber pressure and H_2 addition, on Sn-oxide etching characteristics were evaluated by Auger depth profile analysis. The die shear tests were performed to evaluate the adhesion strength of Sn-3.5%Ag solder bump flip chip. The addition of H_2 to Ar plasma improved the oxide etching characteristics. A low chamber pressure was more effective in oxide removal. The die shear strength of the plasma-treated Sn-3.5Ag solder flip chip was higher than that of the non-treated chip, but it was lower than that of the fluxed chip. The difference in the die shear strength between the plasma-treated specimen and the non-treated specimen increased with increasing bonding temperature. The plasma-treated flip chip fractured at the solder/TSM interface at low bonding temperature, but at the solder/UBM interface at high bonding temperature.

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The effect of the basicity on the formation behaviour of calcium ferrites was investigated in the sintering process of Fe_2O_3-CaO-Al_2O_3-SiO_2 system. In the system of Fe_2O_3-CaO-Al_2O_3, the mineral structure consists of iron oxide particles and matrix phase, which is likely to be CF(calcium ferrite). When SiO_2 is added into Fe_2O_3-CaO-Al_2O_3 system, the area fraction of CF decreases sharply. When the basicity(CaO/SiO_2) decreases below the unity, CF does not form, and the mineral structure is composed of iron oxide particles and the silicate slag. The iron oxide particles are mainly magnetite in the temperature range higher than 1300℃, while they consist of both magnetite and hematite at the temperatures below 1250℃. When SiO_2 is added into Fe_2O_3-CaO-Al_2O_3 system, the formation of hematite is promoted in the lower temperature range. The increase of SiO_2 content tends to change the composition of CF from hemi-CF to mono-CF. The solubility of solutes such as CaO, Al_2O_3 and SiO_2 in CF increase with the increase of SiO_2 content in the system.

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The copper concentrate particles were oxidized in N_2-O_2 gas stream. The effect of oxygen partial pressure and wall temperature on the oxidation behavior of copper concentrate were examined. The desulfurization rate was enhanced by the oxygen partial pressure, and the desulfurization occurred markedly in the region of 30 to 60 ㎝ below the top of the reaction tube. On the basis of X-ray diffraction analysis of the cinder, unreacted core model of copper concentrate covered with an outer product layer of boronite and magnetite was applied to the calculation of the progress of non-isothermal oxidation of copper concentrate particles. The frequency factor k_0 of the interfacial reaction rate constant was determined so as to fit the calculated desulfurization curve to the observed curve. The calculated particle temperature attained the maximum value in the upper part of reaction tube of 30 to 60 ㎝ below the top of the reaction tube. The maximum particle temperature increased with the oxygen partial pressure.

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The reduction kinetics of iron ore fines in a fluidized-bed has been extensively investigated. Iron ore fines with particle size in the range of 710 and 1000 ㎛ were reduced at 800℃ stepwisely from Fe_2O_3 to Fe_3O_4, Fe_3O_4 to Fe_(1-x)O and Fe_(1-x)O to Fe with CO-CO_2 gas mixtures in a batch-type fluidized bed. The gas flow rate used were 2.88 and 5.76Nl/min in a hot fluidization test. The measured reduction curves were compared with those calculated from the perfect mixing model and the bubble assemblage model. It was found that the perfect mixing model showed fairly good agreement at gas flow rate of 5.76Nl/min, while the bubble assemblage model at gas flow rate of 2.88Nl/min. The present study has endeavored to obtain fundamental data for effective plant operations and to provide useful parameters in a scale up plant of a fluidized-bed system.

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Invar alloy has been extensively used for shadow mask of color television and computer monitor because of its low thermal expansion coefficient, but the processing technologies of invar alloys for shadow mask have not been well known. To find out the unknown manufacturing process of invar alloys for shadow mask, variations in mechanical properties with cold reduction ratio and annealing temperature were investigated. Also, the relationships between etching properties and texture in invar alloys were investigated by applying the newly developed texture analysis technique, EBSD. The final cold reduction ratio in the invar alloys was found to be about 25 percent while the cold reduction ratio above 60 percent was needed for the good etching properties in the low carbon Al-killed steel. It was suggested that because {001} grains in the surface of invar alloys had high angle grain boundaries, the more the uniform-distributed {001} grains in the surface, the etchability was improved. When the cold-rolled invar alloys were annealed, the etchability was deteriorated by both more inhomogeneous distribution of coarse {001} recrystallized grains and the increase in high angle grain boundaries with misorientations above 40˚

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