• Journal of Environmental Science International
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• v.22 no.9
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• pp.1097-1103
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• 2013

Tetrafluoromethane($CF_4$) have been widely used as etching and chemical vapor deposition gases for semiconductor manufacturing processes. $CF_4$ decomposition efficiency using microwave system was carried out as a function of the microwave power, the reaction temperature, and the quantity of $Al_2O_3$ addition. High reaction temperature and addition of $Al_2O_3$ increased the $CF_4$ removal efficiencies and the $CO_2/CF_4$ ratio. When the SA30 (SiC+30wt%$Al_2O_3$) and SA50 (SiC+50wt%$Al_2O_3$) were used, complete $CF_4$ removal was achieved at $1000^{\circ}C$. The $CF_4$ was reacted with $Al_2O_3$ and by-products such as $CO_2/CF_4$ and $AlF_3$ were produced. Significant amount of by-product such as $AlF_3$ was identified by X-ray powder diffraction analysis. It also showed that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ after microwave thermal reaction.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.2
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• pp.128-135
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• 2013

This letter presents the MISHFET with si-doped AlGaN/GaN heterostructure for power amplifier. The device grown on 6H-SiC(0001) substrate with a gate length of 180 nm has been fabricated. The fabricated device exhibited maximum drain current density of 837 mA/mm and peak transconductance of 177 mS/mm. A unity current gain cutoff frequency was 45.6 GHz and maximum frequency of oscillation was 46.5 GHz. The reported output power density was 1.54 W/mm and A PAE(Power Added Efficiency) was 40.24 % at 9.3 GHz.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.242-242
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• 2012

From the combined studies of STM and synchrotron photoemission, it has been found that a $CaF_2$ molecule is dissociated to Ca and F atoms on the $Si(114)-2{\times}1$ held at $500^{\circ}C$ at the initial adsorption stage. The Ca atoms form isolated and unique shapes of silicide molecules as shown in Fig. (a), while the F atoms are desorbed from the surface. On the other hand, beyond a $CaF_2$ coverage of 0.3 monolayer, as shown in Fig. (b), in addition to these silicide molecules, a 1-D facet [composed of (113) and (115) faces] adjacent to an etch pit has been observed, and F atoms are also detected from photoemission. These results imply that F atoms act as an etchant on Si(114) and CaF is adsorbed selectively on the (113) face of this facet. From the present studies, it has been concluded that, an insulating $CaF_2$ layer like that on Si(111) cannot be formed on Si(114), but a CaF-decorated nanofacet with a high aspect-ratio can be grown.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.1-33
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• 2000

Silicon carbide ceramics with sintering additives from the system AlN-Y$_2$O$_3$ can be gas-pressure sintered to theoretical density. While commonly a combination of sesquioxides is used such as Al$_2$O$_3$-Y$_2$O$_3$, the oxynitrid additives offer the advantage that only a nitrogen atmosphere is require instead of a powder. By starting form a mixture of ${\beta}$-SiC and ${\alpha}$-SiC, and by performing dedicated heat treatments after densification, anisotropic grain growth is obtained which leads to a platelet microstructure showing enhance fracture toughness. In the present work, recent improvement of the mechanical behaviour of these materials at ambient and high temperatures is reported. By means of a surface oxidation treatment in air it is possible to obtain four-point bending strengths in excess of 1 GPa, and the strength retention at high temperatures is significantly improved.

• Journal of Powder Materials
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• v.1 no.2
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• pp.135-144
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• 1994

Silicon carbide powder was prepared from mixtures of Sangdong silica sand and carbon black by SHS (Self propagating High temperature Synthesis) method which utilizes magnesiothermic reduction of silica. In the powder preparation process, the reacted powder was leached by chloric acid to remove the magnesium oxide and was subsequently roasted to remove free carbon. The impurities were mostly eliminated by hot acid treatment. The resultant SiC powder showed the mean particle size of 0.22 ${\mu}{\textrm}{m}$ and the specific surface area of $66.55 m^2/g$. The SiC powder was mixed with 1 wt% of boron and of carbon to increase densification rate. The mixed powder was pressed and sintered pressurelessly at $2100^{\circ}C$ for 30 min in argon gas. The sintered body showed the hardness of $2550 kg{\cdot}f/mm^2$ and the fracture toughness, KIC of $3.47 MN/m^{3/2}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.194-195
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• 2006

Aluminum oxide films directly grown on n-type 6H-SiC(0001) substrates were fabricated by RF magnetron sputtering system. Metal-insulator-semiconductor(MIS) C-V properties with aluminum oxide thin films showed hysteresis and f1at band voltage shift. The dielectric constant of the film calculated from the capacitance at the accumulation region was about 5. Typical gate leakage current density of film at room temperature was the order of $10^{-9}\;A/cm^2$ at the range of within 2MV/cm. The breakdown did not occur at the film within the measurement range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.12
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• pp.1090-1095
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• 2008

The SiOCH films that low dielectric interlayer dielectric materials were deposited on p-type Si(100) substrates through the dissociation of BTMSM precursors with oxygen gas by using PECVD method. BTMSM precursor was introduced with the flow rates from 42 sccm to 60 sccm by 2 sccm step in the constant flow rate of 60 sccm $O_2$. SiOCH thin films were annealed at $450^{\circ}C$ for 30 minutes. The electrical property of SiOCH thin films was studied by MIS, Al/SiOCH/p-Si(100), structure. Annealed samples showed even greater reductions of the maximum capacitance and the dielectric constant of the SiOCH samples, owing to reductions of surface charge density. we confirmed this result with derivative of C-V characteristic, leakage current density. The maximum capacitance and leakage current density were respectively decreased about 4 pF, 60% after annealing. The average of low-k value is approximatly 2.07 after annealing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.9
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• pp.598-601
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• 2015

The $Sr_{0.7}Bi_{2.3}Nb_2O_9(SBN)$ thin films are deposited on Pt electrode($Pt/Ti/SiO_2/Si$) using RF sputtering method at various deposition temperature. The deposition temperature of optimum was $300^{\circ}C$. SBN thin films were annealed at $500{\sim}700^{\circ}C$ using furnace and RTA, respectively. The surface roughness showed about 2.42 nm in annealing temperature($600^{\circ}C$) of furnace. The capacitance density of SBN thin films were increased with the increase of annealing temperature. The maximum capacitance density of $0.7{\mu}F/cm^2$ was obtained by annealing temperature($700^{\circ}C$). The frequency dependence of dielectric loss showed about 0.03 in frequency ranges of 1~1,000 kHz.

• Composites Research
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• v.13 no.5
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• pp.31-36
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• 2000

The effect of several important processing variables was investigated on formation of porous mullite with acicular microstructure. Experimental results demonstrated that microstructure and porosity of porous mullite are depending on concentration of $AlF_3$, holding time at $900^{\circ}C$ and starting material. Acicular mullite was developed by increasing amount of $AlF_3$ and holding time at $900^{\circ}C$. Mullite began to be formed at $1200^{\circ}C$ and the resultant microstructure sintered at this temperature is similar to those at higher temperatures. Porosity increases with increase in amounts of $AlF_3$ and holding time at $900^{\circ}C$ . Therefore, it is found that microstructure of reaction-sintered porous mullite can be controlled by governing the amount of $AlF_3$ and holding time at $900^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.11-15
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• 1994

The TSEE characteristics of LiF(Mg,Cu,Na,Si)phosphor for gamma and beta rays are described. The TSEE glow curve of this phosphor showed 5 peaks in the range from $20^{\circ}C$ to $400^{\circ}C$ and its main peak appeared at $240^{\circ}C$. The sensitivity of the phospor for $^{60}Co$ gamma rays was about 450counts/mR. TSEE energy dependence for various beta radiation was nearly constant (${\pm}10%$) in the mean beta particle energy range from 0.02MeV to 0.8MeV. The efficiency of TSEE of the phosphor for beta radiation was $(2{\sim}15){\times}10^{-3}$.