• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.832-835
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• 2001

We report the structural and electrical properties of hafnium oxide (HfO$_2$) films with tungsten silicide (WSi$_2$) metal gate. In this study, HfO$_2$thin films were fabricated by oxidation of sputtered Hf metal films on Si, and WSi$_2$was deposited directly on HfO$_2$by LPCVD. The hysteresis windows in C-V curves of the WSi$_2$HfO$_2$/Si MOS capacitors were negligible (<20 mV), and had no dependence on frequency from 10 kHz to 1 MHz and bias ramp rate from 10 mV to 1 V. In addition, leakage current was very low in the range of 10$^{-9}$ ~10$^{-10}$ A to ~ 1 V, which was due to the formation of interfacial hafnium silicate layer between HfO$_2$and Si. After PMA (post metallization annealing) of the WSi$_2$/HfO$_2$/Si MOS capacitors at 500 $^{\circ}C$ EOT (equivalent oxide thickness) was reduced from 26 to 22 $\AA$ and the leakage current was reduced by approximately one order as compared to that measured before annealing. These results indicate that the effect of fluorine diffusion is negligible and annealing minimizes the etching damage.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.795-797
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• 1998

A $BaTiO_3$, ferroelectric material, was mixed $SrTiO_3$, $(x)BaTiO_3-(1-x)SrTiO_3$($0.7{\leq}x{\leq}1$) ceramic capacitor with stable electrical properties in high voltage was fabricated. And microstructure, electrical property were investigated with $SrTiO_3$ mol ratio. The shrinkage, open porosity, sintering density were predominated at $9BaTiO_3-0.1SrTiO_3$. Increasing $SrTiO_3$ mol ratio, curie temperature was shifted at low temperature and maximum permittivity was increased. Also, $0.9BaTiO_3-0.1SrTiO_3$ was showed stable dielectric properties at $25{\sim}80[^{\circ}C]$. V-I properties of specimen were observed in the temperature range of $21{\sim}143[^{\circ}C]$, were divided into three regions. The region I below 10[kV/cm] was shown Ohmic conduction, the region II from 10 to 30[kV/cm] was explained by the Poole-Frenkel emission theory and the region III above 30[kV/cm] was analysed by the tunneling effect.

• Transactions on Electrical and Electronic Materials
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• v.17 no.2
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• pp.92-97
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• 2016

This paper presents design and simulation of wide band RF microswitch that uses electrostatic actuation for its operation. RF MEMS devices exhibit superior high frequency performance in comparison to conventional devices. Similar techniques that are used in Very Large Scale Integration (VLSI) can be employed to design and fabricate MEMS devices and traditional batch-processing methods can be used for its manufacturing. The proposed switch presents a novel design approach to handle reliability concerns in MEMS switches like dielectric charging effect, micro welding and stiction. The shape has been optimized at actuation voltage of 14-16 V. The switch has an improved restoring force of 20.8 μN. The design of the proposed switch is very elemental and primarily composed of electrostatic actuator, a bridge membrane and coplanar waveguide which are suspended over the substrate. The simple design of the switch makes it easy for fabrication. Typical insertion and isolation of the switch at 1 GHz is -0.03 dB and -71 dB and at 85 GHz it is -0.24 dB and -29.8 dB respectively. The isolation remains more than - 20 db even after 120 GHz. To our knowledge this is the first demonstration of a metal contact switch that shows such a high and sustained isolation and performance at W-band frequencies with an excellent figure-of merit (fc=1/2.pi.Ron.Cu =1,900 GHz). This figure of merit is significantly greater than electronic switching devices. The switch would find extensive application in wideband operations and areas where reliability is a major concern.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.1
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• pp.25-32
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• 2015

Dielectric barrier discharge (DBD) plasma actuator was designed to reduce aerodynamic drag in a cylindrical model and wind tunnel test was performed at various wind velocities. In addition, computational fluid dynamics (CFD) analysis and flow visualization were used to investigate the effect of the plasma on the flow stream in the cylinderical model. At low wind velocity, the plasma actuator had no effects because flow separation did not appear. The aerodynamic drag was reduced by 14% at 14 m/s and by 27% at 17 m/s, respectively. It was confirmed by CFD analysis and flow visualization that the DBD plasma actuator decreased in pressure difference around the cylindrical model, thus decreasing the magnitude of wake vortex.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.2
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• pp.93-98
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• 2001

YMnO$_3$ films are excellent gate dielectric materials of ferroelectric random access memories (FRAMs) with MFSFET (metal -ferroelectric-semiconductor field effect transistor) structure because YMnO$_3$ films can be deposited directly on Si substrate and have a relatively low permittivity. Although the patterning of YMnO$_3$ thin films is the requisite for the fabrication of FRAMs, the etch mechanism of YMnO$_3$ thin films has not been reported. In this study, YMnO$_3$thin films were etched with Cl$_2$/Ar gas chemistries in inductively coupled plasma (ICP). The maximum etch rate of YMnO$_3$ film is 285$\AA$/min under Cl$_2$/(Cl$_2$+Ar) of 1.0, RF power of 600 W, dc-bias voltage of -200V, chamber pressure of 15 mTorr and substrate temperature of $25^{\circ}C$. The selectivities of YMnO$_3$ over CeO$_2$ and $Y_2$O$_3$ are 2.85, 1.72, respectively. The selectivities of YMnO$_3$ over PR and Pt are quite low. Chemical reaction in surface of the etched YMnO$_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS) surface of the selected YMnO$_3$ thin films was investigated with X-ray photoelectron spectroscopy(XPS) and secondary ion mass spectrometry (SIMS). The etch profile was also investigated by scaning electron microscopy(SEM)

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.572-577
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• 2001

The electrical properties of Pr$_{6}$ O$_{11}$ -based ZnO varistors consisting of ZnO-Pr$_{6}$ O$_{11}$ -CoO-Cr$_2$O$_3$-Er$_2$O$_3$ ceramics were investigated with sintering temperature in the range of 1325~f1345$^{\circ}C$. As sintering temperature is raised., the nonlinear exponent was increased up to 1335$^{\circ}C$, reaching a maximum 70.53, whereas raising sintering temperature further caused it to decrease, reaching a minimum 50.18 and the leakage current was in the range of 1.92~4.12 $\mu$A. The best electrical properties was obtained from the varistors sintered at 1335$^{\circ}C$, exhibiting a maximum (70.53) in the nonlinear exponent and a minimum (1.92 $\mu$A) in the leakage current, and a minimum (0.035) in the dissipation factor. On the other hand, the donor concentration was in the range of (0.90~1.14)x10$^{18}$ cm$^{-3}$ , the density of interface states was in the range of (2.69~3.60)x10$^{12}$ cm$^{-2}$ , and the barrier height was in the range of 0.77~1.21 eV with sintering temperature. With raising sintering temperature, the variation of C-V characteristic parameters exhibited a mountain type, reaching maximum at 134$0^{\circ}C$. Conclusively, it was found that the V-I, C-V, and dielectric characteristics of Pr$_{6}$ O$_{11}$ -based ZnO varistors are affected greatly by sintering temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.723-727
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• 2003

[ $Sr_xBa_{1-x}Nb_2O_6$ ] (SBN, $0.25{\leq}x{\leq}0.75$) ceramic is a ferroelectric material with tetragonal tungsten bronze (TTB) type structure, which has a high pyroelectric coefficient and a nonlinear electro-optic coefficient value. In spite of its advantages, SBN has not been investigated well compared to other ferroelectric materials with perovskite structure. In this study, SBN thin film was manufactured by ion beam sputtering technique using the prepared SBN target in $Ar/O_2$ atmosphere. SBN30 thin film of $1000{\AA}$ was pre-deposited as a seed layer on $Pt(100)/TiO_2/SiO_2/Si$ substrate followed by SBN60 deposition up to $3000{\AA}$ in thickness. As-deposited SBN60/SBN30 layer was heat-treated at different temperatures of 650, 700, 750, and $800^{\circ}C$ in air, respectively The crystallinity and orientation behavior as well as electric properties of SBN60/SBN30 multi-layer were examined. The deposited layer was uniform and the orientation was shown primarily along (001) plane from XRD pattern. There was no difference in the crystal structure with heat-treatment temperature, but the electric properties depended on the heating temperature and was the best at $750^{\circ}C$. In electric properties of Pt/SBN60/SBN30/Pt thin film capacitor prepared, the remnant polarization (2Pr) value was $15{\mu}C/cm^2$, the coercive field (Ec) 75 kV/cm, and the dielectric constant 1075, respectively.

• Journal of the Korean Ceramic Society
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• v.33 no.5
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• pp.572-582
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• 1996

The porous silicon was prepared in the condition of 70mA/cm2 and 5.10 sec and then oxidized at 800~110$0^{\circ}C$ MOS(Metal Oxide Semiconductor) structure was prepared by Al electrode deposition and analyzed by C-V (Capacitance-Voltage) characteristics. Dielectric constant of oxidized porous silicon was large in the case of low temperature (800, 90$0^{\circ}C$) and short time(20-30min) oxidation and was nearly the same as thermal SiO2 3.9 in the case of high temperature (110$0^{\circ}C$) and long time (above 60 min) It is though to be caused byunoxidized silicon in oxidized porous silicon film and capacitance increase due to surface area increment effect.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.129-133
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• 2016

$MnO_2$ was added to the $0.95(Na_{0.5}K_{0.5})NbO_3-0.05CaTiO_3$ (NKN-CT) ceramics in order to promote the densification and improve the poling efficiency by increasing the resistance of the specimens. Densification and abnormal grain growth occurred in the $MnO_2$-added NKN-CT ceramics sintered at $1020^{\circ}C$, indicating that $MnO_2$ assisted the liquid-phase sintering of these materials. $Mn^{3+}$ ions were considered to enter the A-site of the matrix, thereby producing the free electrons, which interacted with the holes resulting from the evaporation of alkali ions. This interaction results in an increase in the resistance of the specimens. The increased resistance improved the poling efficiency and, hence, the dielectric and piezoelectric properties of the NKN-CT ceramics. A few of the $Mn^{3+}$ ions that entered the B-site of the NKN-CT matrix led to a slight increase in the mechanical quality factor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.772-775
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• 2004

본 논문에서는 $B_2O_3$ 첨가가 Ba$(Mg_{1/3}Ta_{2/3})O_3$ (BMT)의 유전특성 및 미세구조의 변화에 미치는 영향에 대해 연구하였다 $B_2O_3$가 소량 첨가되었을 때는 결정립의 성장을 야기하여 치밀한 미세구조를 보였지만, 다량이 첨가된 경우 비정상 결정립 성장을 야기하여 치밀화가 떨어지는 미세구조를 보임과 동시에 $Ba_3Ta_5O_{15}$의 2차상을 형성했다. 이는 소량의 $B_2O_3$ 첨가가 유전특성의 향상을 가져왔지만, 다량의 첨가는 오히려 특성의 악화를 가져온 결과의 원인이라 생각된다. 0.5mol%의 $B_2O_3$를 첨가하여 $1500^{\circ}C$에서 6시간 소결한 경우 ${{\varepsilon}_r}=24$, $Q{\times}f=210,000GHz$의 유전 특성 값과 $4.74ppm/^{\circ}C$의 $T_{cf}$ 값을 얻었다.