Yong-Goo Kim

Variable stars in the open cluster NGC 2099 (M37)

Time-series CCD photometric observations of the intermediate-age open cluster NGC 2099 were performed to search for variable stars. We also carried out BV photometry to study physical properties of variables in the cluster. Using V-band time-series data, we carefully examined light variations of about 12,000 stars in the range of 10 < V< 22 mag. A total of 24 variable stars have been identified; seven stars are previously known variables, and 17 stars are newly identified. On the basis of observational properties such as light curve shape, period, and amplitude, we classified the new variable stars as nine δ Scuti-type pulsating stars, seven eclipsing binaries, and one peculiar variable star. Judging from the position of δ Scuti-type stars in the color-magnitude diagram, only two stars are likely to have cluster membership. One new variable, KV 10, shows peculiar light variations with a δ Scuti-type short period of about 0.044 days, as well as a long period of 0.417 days.

Highly thermal robust NiSi for nanoscale MOSFETs utilizing a novel hydrogen plasma immersion ion implantation and Ni-Co-TiN tri-layer

In this letter, hydrogen plasma immersion ion implantation (H PIII) with Ni-Co-TiN tri-layer is introduced for the first time to enhance the thermal stability of the Ni-silicide for nanoscale CMOS technology. The Ni-silicided poly-Si gate and source/drain showed stable sheet resistance in spite of 650/spl deg/C, 30 min post-silicidation annealing. The junction leakage current is even improved a lot without degradation of device performance using the proposed method.

On-chip charge pumping method for characterization of interface states of ultra thin gate oxide in nano CMOS technology

For the first time, on-chip charge pumping method is proposed to characterize ultra thin gate oxide for nano-scale CMOSFETs. Designed on-chip charge pumping system can supply 30-500MHz square-type pulse waves to DUT transistor and measured charge pumping current showed no gate tunneling current dependency which can be easily monitored in very thin gate oxide. In addition to the measurement of interface states by fixed-amplitude method, the distribution of interface states in channel region can be easily extracted by fixed-base method using this system. The proposed method is also successfully applied to analyze hot-carrier stress-induced threshold voltage (Vt)-degradation and to evaluate plasma process induced damage in terms of interface trap density

Variable Stars in the Open Cluster M11 (NGC 6705)

V-band time-series CCD photometric observations of the intermediate-age open cluster M11 were performed to search for variable stars. Using these time-series data, we carefully examined light variations of all stars in the observing field. A total of 82 variable stars were discovered, of which 39 stars had been detected recently by Hargis et al. On the basis of observational properties such as variable period, light-curve shape, and position on a color-magnitude diagram, we classified their variable types as 11 d Scuti-type pulsating stars, two g Doradus-type pulsating stars, 40 W UMa-type contact eclipsing binaries, 13 Algol-type detached eclipsing binaries, and 16 eclipsing binaries with long period. Cluster membership for each variable star was deduced from the previous proper-motion results and position on the color-magnitude diagram. Many pulsating stars and eclipsing binaries in the region of M11 are probable members of the cluster.

Abnormal Oxidation of NiSi Formed on Arsenic-Doped Substrate

Nickel silicide is a most up-to-date self-aligned silicide (salicide) technology for nanoscale complementary metal-oxide-semiconductor field-effect transistors. However, an unintended oxidation of nickel silicide happenedonly on As-doped substrate. This abnormal oxidation phenomenon occurred only when the annealing temperature was higher than 613°C (sublimation point of As). The main reason for the oxidation is believed to the thermal energy that induces the diffusion of Ni from the nickel silicide to the substrate direction. Due to the oxidation, nickel silicide on As-doped substrate showed poor thermal stability contrasted to BF 2 -doped substrate.

Time-Dependent Dielectric Breakdown of -Doped High- /Metal Gate Stacked NMOSFETs

Time-dependent dielectric breakdown (TDDB) characteristics of La2O3-doped high-k dielectric in Hf-based high-k/TaN metal gate stack were studied. Unlike the abrupt breakdown in the conventional SiO2 , dielectric breakdown behaviors of La-incorporated HfON and HfSiON dielectrics show progressive breakdown characteristics. Moreover, the extracted Weibull slope beta of breakdown distribution is in the range of 0.87-1.19, and it is independent on capacitor areas and stress conditions. Moreover, field dependence of TBD and stress-induced leakage current strongly suggest that the E-model is more applicable to explain in TDDB of La-incorporated high-k dielectric in Hf-based high-k/metal gate stack structure.

Co-Induced Low-Temperature Silicidation of Ni Germanosilicide Using NiPt Alloy and the Effect of Ge Ratio on Thermal Stability

In this paper, novel Ni germanosilicide technology using NiPt alloy and Co overlayer has been proposed. Using the Co overlayer after NiPt deposition on Si1-xGex, the formation temperature of low resistive Ni germanosilicide is lowered with high thermal stability. The thermal stability of Ni germanosilicide with different Ge fraction in is also characterized. The sheet resistance degrades as increasing the Ge fraction (x) in Si1-xGex when NiPt/TiN is used. However, using the Co overlayer, the sheet resistance property among Ni germanosilicide formed with different Ge fraction is improved greatly compared with those of NiPt/TiN case (without Co overlayer). Therefore, low-temperature formation of highly thermal robust Ni germanosilicide can be achieved through the NiPt/Co/TiN tri-layer.

Midazolam dose for loss of response to verbal stimulation during the unilateral or bilateral spinal anesthesia

Background: We have conducted this study to investigate whether unilateral or bilateral spinal anesthesia with bupivacaine induces different sensitivity to intravenous (i.v.) midazolam for sedation.

Investigation of Device Performance and Negative Bias Temperature Instability of Plasma Nitrided Oxide in Nanoscale p-Channel Metal–Oxide–Semiconductor Field-Effect Transistor's

In this paper, we investigated the device performance and negative bias temperature instability (NBTI) degradation for thermally nitrided oxide (TNO) and plasma nitrided oxide (PNO) in nanoscale p-channel metal oxide semiconductor field effect transistor (PMOSFET). PNOs show the improvement of dielectric performance compared to TNO with no change of the device performance. PNOs also show the improvement of NBTI immunity than TNO at low temperature stress, whereas NBTI immunity of PNO with high N concentration can be worse than TNO at high temperature stress. Recovery effect of NBTI degradation of PNO is lower than that of TNO and it is increased as the N concentration is increased in PNO because the dissociated Si dangling bonds and generated positive oxide charges are repassivated and neutralized, respectively. Moreover, complete recovery of ΔVth is dominated by neutralization of positive oxide charges. Therefore, N contents at polycrystalline Si/SiO2 interface as well as N contents at Si/SiO2 interface can affect significantly on NBTI degradation and recovery effect.

Time-Dependent Dielectric Breakdown of

Time-dependent dielectric breakdown (TDDB) characteristics of La2O3-doped high-k dielectric in Hf-based high-k/TaN metal gate stack were studied. Unlike the abrupt breakdown in the conventional SiO2 , dielectric breakdown behaviors of La-incorporated HfON and HfSiON dielectrics show progressive breakdown characteristics. Moreover, the extracted Weibull slope beta of breakdown distribution is in the range of 0.87-1.19, and it is independent on capacitor areas and stress conditions. Moreover, field dependence of TBD and stress-induced leakage current strongly suggest that the E-model is more applicable to explain in TDDB of La-incorporated high-k dielectric in Hf-based high-k/metal gate stack structure.