• Journal of the Semiconductor & Display Technology
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• v.2 no.2
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• pp.5-8
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• 2003

In this study, as Cu diffusion barrier, tantalum nitrides were successfully deposited on Si(100) substrate and $SiO_2$ by plasma assisted atomic layer deposition(PAALD) and thermal ALD, using pentakis (ethylmethlyamino) tantalum (PEMAT) and NH$_3$ as precursors. The TaN films were deposited at $250^{\circ}C$ by both method. The growth rates of TaN films were 0.8${\AA}$/cycle for PAALD and 0.75${\AA}$/cycle for thermal ALD. TaN films by PAALD showed good surface morphology and excellent step coverage for the trench with an aspect ratio of h/w -1.8:0.12 mm but TaN films by thermal ALD showed bad step coverage for the same trench. The density for PAALD TaN was 11g/cmand one for thermal ALD TaN was 8.3g/$cm^3$. TaN films had 3 atomic % carbon impurity and 4 atomic % oxygen impurity for PAALD and 12 atomic % carbon impurity and 9 atomic % oxygen impurity for thermal ALD. The barrier failure for Cu(200 nm)/TaN(10 nm)/$SiO_2$(85 nm)/ Si structure was shown at temperature above $700^{\circ}C$ by XRD, Cu etch pit analysis.

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.38-38
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• 2004

• Progress in Superconductivity
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• v.6 no.1
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• pp.37-40
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• 2004

We investigated the effects of impurity doping on the electrical transport and magnetic properties of TEX>$(Ru, Sn)(Sr, La)<_2$$EuCeCu_2$$O_{z}$ samples. We found that Sn substitution fur Ru causes a significant decrease of the volume fraction of ferromagnetic phase, as well as a decrease of the temperature where the ferromagnetic component is observed. La substitution for Sr leads to an increase of the magnetic ordering temperature with a moderate change of ferromagnetic component. The experimental results are discussed in conjunction with the structural data, transport properties and a possible change of oxygen content.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.5-8
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• 1989

Conventional ceramic method has been used to prepare the green phase, $Y_2BaCuO_5$, commonly observed in 90-K superconductor $YBa_2Cu_3O_P{7-{\delta}}$as an impurity phase. The powder X-ray diffraction analysis indicates that $Y_2BaCuO_5$ has an orthorhombic symmetry with lattice parameter of a = 12.2 $\AA$, b = 5.61 $\AA$, and c = 7.14 $\AA.$ The average g-value 2.13 observed in ESR spectrum is attributable to Cu2+ stabilized in $C_{4v}$ field. From the magnetic susceptibility ($\mu$eff = 2.29 BM) and the ESR measurements, it is confirmed that Cu(II) $3d^9$ electrons in $Y_2BaCuO_5$ are localized and can be characterized by Curie-Weiss behavior. Optical reflectance spectrum shows a broad absorption peak around 680 nm due to dxy ${\rightarrow}$ $dx^2-y^2$ eletronic transition.

• Journal of the Korean Vacuum Society
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• v.14 no.1
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• pp.17-23
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• 2005

Glow discharge mass spectrometry(GDMS) was used to determine the impurity concentrations of the deposited Cu films and the 6N Cu target. Cu films were deposited on Si (100) substrates at zero substrate bias voltage and a substrate bias voltage of -50 V using a non-mass separated ion beam deposition method. Since do GDMS has a little difficulty to apply to thin films because of the accompanying non-conducting substrate, we have used an aluminum foil to cover the edge of the Cu film in order to make an electrical contact of the Cu film deposited on the non-conducting substrate. As a result, the Cu film deposited at the substrate bias voltage of -50 V showed lower impurity contents than the Cu film deposited without the substrate bias voltage although both the Cu films were contaminated during the deposition. It was found that the concentration change of each impurity in the Cu films by applying the negative substrate bias voltage is related to the difference in their ionization potentials. The purification effect by applying the negative substrate bias voltage might result from the following reasons: 1) Penning ionization and an ionization mechanism proposed in the present study, 2) difference in the kinetic energy of accelerated Cu+ ions toward the substrate with/without the negative substrate bias voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.543-546
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• 2004

The melting temperature and critical temperature(Tc) of $YBa_2Cu_3O_x$ with deferent content impurities of PbO and $BaPbO_3$ were studied. When the PbO was used as addition in $YBa_2Cu_3O_x$, although the melting point could be reduced, the superconductivity(the transition width, ${\Delta}T_c$) became poor. From the XRD pattern of the sintered mixture of $YBa_2Cu_3O_x$ and PbO it was known that there is a reaction between $YBa_2Cu_3O_x$ and PbO, and the product is $BaPbO_3$. In the process of the reaction the superconducting phase of $YBa_2Cu_3O_x$ was decreased and in the sample $BaPbO_3$ became the main phase. Therefore the superconductivity was reduced. $BaPbO_3$ was chosen as the impurity for the comparative study. The single phase BaPbO3 was synthesized by the simple way from both mixtures of $BaPbO_3$ and PbO, $BaPbO_3\;and\;PbO_2$. Deferent contents of $BaPbO_3$(10%, 20%, 30%) were added in the $YBa_2Cu_3O_x$. By the phase analysis in the XRD patterns it was proved that there werenot reactions between $YBa_2Cu_3O_x$ and $BaPbO_3$. When $BaPbO_3$ was used as impurity in $YBa_2Cu_3O_x$ the superconductivity was much better than PbO as impurity in $YBa_2Cu_3O_x$. But the melting point of $YBa_2Cu_3O_x$ with $BaPbO_3$ could not be found when the temperature was lower than $1000^{\circ}C$ in the DTA measurement.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.57-59
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• 2004

The melting temperature and critical temperature (Tc) of YBa$_2$Cu$_3$Ox with deferent content impurities of PbO and BaPbO$_3$ were studied. When the PbO was used as addition in YBa$_2$Cu$_3$Ox, although the melting point could be reduced, the superconductivity (the transition wide, ΔTc) became poor. From the XRD pattern of the sintered mixture of YBa$_2$Cu$_3$Ox and PbO it was known that there is a reaction between YBa$_2$Cu$_3$Ox and PbO, and the product is BaPbO$_3$. In the process of the reaction the superconducting phase of YBa$_2$Cu$_3$Ox was decreased and in the sample BaPbO$_3$became the main phase. Therefore the superconductivity was reduced. BaPbO$_3$was chosen as the impurity for the comparative study. The single phase BaPbO$_3$was synthesized by the simple way from both mixtures of BaPbO$_3$and PbO, BaPbO$_3$and PbO$_2$. Deferent contents of BaPbO$_3$(10%, 20%, 30%) were added in the YBa$_2$Cu$_3$Ox. By the phase analysis in the XRD patterns it was proved that there were not reactions between YBa$_2$Cu$_3$Ox and BaPbO$_3$. When BaPbO$_3$was used as impurity in YBa$_2$Cu$_3$Ox the superconductivity was much better than PbO as impurity in YBa$_2$Cu$_3$Ox But the melting point of YBa$_2$Cu$_3$Ox with BaPbO$_3$could not be found when the temperature was lower than 1000 $^{\circ}C$ in the DTA measurement.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.14-19
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• 2002

In this study, as Cu diffusion barrier, tantalum nitrides were successfully deposited on Si(100) substrate and SiO2 by plasma assisted atomic layer deposition(PAALD) and thermal ALD, using pentakis (ethylmethlyamino) tantalum (PEMAT) and $NH_3$ as precursors. The TaN films were deposited on $250^{\circ}$C by both method. The growth rates of TaN films were $0.8{\AA}$/cycle for PAALD and $0.75{\AA}$/cycle for thermal ALD. TaN films by PAALD showed good surface morphology and excellent step coverage for the trench with an aspect ratio of h/w - $1.8 : 0.12 \mu\textrm{m}$ but TaN films by thermal ALD showed bad step coverage for the same trench. The density for PAALD TaN was $11g/\textrm{cm}^3$ and one for thermal ALD TaN was $8.3g/\textrm{cm}^3$. TaN films had 3 atomic % carbon impurity and 4 atomic % oxygen impurity for PAALD and 12 atomic % carbon impurity and 9 atomic % oxygen impurity for thermal ALD. The barrier failure for Cu(200nm)/TaN(l0nm)/$SiO_2(85nm)$/Si structure was shown at temperature above $700^{\circ}$C by XRD, Cu etch pit analysis.

• Electrical & Electronic Materials
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• v.7 no.3
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• pp.213-219
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• 1994

Cu compensated Si doped GaAs (GaAs :Si:Cu has been chosen as the switch material. The GaAs material has been characterized by DLTS(Deep Level Transient Spectroscopy) technique and the obtained data were used in the computer simulation. Simulation studies are performed on several GaAs switch systems, composed of different densities of Cu, to investigate the influence of deep traps in the switch systems. The computed results demonstrates important aspect of the switch, the existence of two stable states and fast optical quenching. An important parameter optimum Cu density for the switch are also determined.

• Korean Journal of Materials Research
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• v.6 no.8
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• pp.817-824
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• 1996

Removal of Cu impurities on Si substrates using remote H-plasma was investigated. Si substrates were intentionally contaminated by 1ppm ${CuCI}_{2}$, standard chemical solution. To determine the optimal process condition, remote H-plasma cleaning was conducted varying the parameters of rf power, cleaning time and remoteness(the distance between the center of plasma and the surface of Si substrate). After remote H-plasma cleaning was conducted, Si surfaces were analysed by TXRF(total x-ray reflection fluorescence) and AFM(atomic force microscope). The concentration of Cu impurity was reduced by more than a factor of 10 and its RMS roughness was improved by more than 30% after remote H-plasma cleaning. TXRF analysis results show that remote H-plasma cleaning is effective in eliminating Cu impurity on Si surface when it is performed under the optimal process condition. AFM analysis results also verifies that remote H-plasma cleaning makes no damage to the Si surface. The deposition mechanism of Cu impurity may be explained by the redox potential(oxidation-reduction reaction potential) theory. Based on the XPS analysis results we could draw a conclusion that Cu impurities on the Si substrate are removed together with the oxide by a "lift-off" mechanism when the chemical oxide( which forms when Cu ions are adsorbed on the Si surface) is etched off by reactive hydrogen atoms.gen atoms.