• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.290-293
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• 2003

Ohmic contact characteristics of Al ion implanted n-type SiC wafer were investigated. Al ions implanted with high dose to obtain the final concentration of $5{\times}10^{19}/cm^3$, then annealed at high temperature. Firstly, B ion ion implanted p-well region were formed which is needed for fabrication of SiC devices such as DIMOSFET and un diode. Secondly, Al implanted high dose region for ohmic contact were formed. After ion implantation, the samples were annealed at high temperature up to $1600^{\circ}C\;and\;1700^{\circ}C$ for 30 min in order to activate the implanted ions electrically. Both the inear TLM and circular TLM method were used for characterization. Ni/Ti metal layer was used for contact metal which is widely used in fabrication of ohmic contacts for n-type SiC. The metal layer was deposited by using RF sputtering and rapid thermal annealed at $950^{\circ}C$ for 90sec. Good ohmic contact characteristics could be obtained regardless of measuring methods. The measured specific contact resistivity for the samples annealed at $1600^{\circ}C\;and\;1700^{\circ}C$ were $1.8{\times}10^{-3}{\Omega}cm^2$, $5.6{\times}10^{-5}{\Omega}cm^2$, respectively. Using the same metal and same process of the ohmic contacts in n-type SiC, it is found possible to make a good ohmic contacts to p-type SiC. It is very helpful for fabricating a integrated SiC devices. In addition, we obtained that the ratio of the electrically activated ions to the implanted Al ions were 10% and 60% for the samples annealed at $1600^{\circ}C\;and\;1700^{\circ}C$, respectively.

• Korean Journal of Metals and Materials
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• v.50 no.8
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• pp.569-573
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• 2012

In order to understand the difference in SiC deposition between the $CH_3SiCl_3-H_2$ and $C_3H_8-SiCl_4-H_2$ systems, we calculate the phase stability among ${\beta}$-SiC, graphite and silicon. We constructed the phase-diagram of ${\beta}$-SiC over graphite and silicon via computational thermodynamic calculation considering pressure (P), temperature (T) and gas composition (C) as variables. Both P-T-C diagrams showed a very steep phase boundary between the SiC+C and SiC region perpendicular to the H/Si axis, and also showed an SiC+Si region with a H/Si value of up to 6700 in the $C_3H_8-SiCl_4-H_2$, and 5000 in the $CH_3SiCl_3-H_2$ system. This difference in phase boundaries is explained by the ratio of Cl to Si, which is 4 for the $C_3H_8-SiCl_4-H_2$ system and 3 for the $C_3H_8-SiCl_4-H_2$ system. Because the C/Si ratio is fixed at 1 in the $CH_3SiCl_3-H_2$ system while it can be variable in the $C_3H_8-SiCl_4-H_2$ system, the functionally graded material is applicable for better mechanical bonding during SiC coating on graphite substrate in the $C_3H_8-SiCl_4-H_2$ system.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.60-60
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• 2003

디자인 룰에 의해 Gate Length 가 100nm 이하로 줄어듦에 따라 Gate delay 감소와 Switch speed 향상을 위해 보다 더 큰 drive current 를 요구하게 되었다. 본 연구는 dirve current 를 증가시키기 위해 고안된 Strained Si substrate 를 만들기 위한 SiGe layer 성장에 관한 연구이다. SiGe layer를 성장시킬 때 SiH$_4$ gas와 GeH$_4$ gas를 furnace에 flow시켜 Chemical 반응에 의해 Si Substrate를 성장시키는 LPCVD(low pressure chemical vapor depositio)법을 사용하였고 SIMS와 nanospec을 이용하여 박막 두께 및 Ge concentration을 측정하였고, AFM으로 surface의 roughness를 측정하였다. 본 연구에서 우리는 10,20,30,40%의 Ge concentration을 갖는 10nm 이하의 SiGe layer를 얻기 위하여 l0nm 이하의 fixed 된 두께로 SiGe layer를 성장시킬 때 temperature, GeH$_4$ gas pre-flow, SiH$_4$ 와 GeH$_4$의 gas ratio를 변화시켜 성장시킨 후 Ge 의 concentration과 실제 형성된 두께를 측정하였고, SiGe의 mole fraction의 변화에 따른 surface의 roughness 를 측정하였다. 그 결과 10 nm의 두께에서 temperature, GeH$_4$ gas pre-flow, SiH$_4$ 와 GeH$_4$ 의 gas ratio의 변화와 Ge concentration 과의 의존성을 확인 할 수 있었고, SiGe 의 mole traction이 증가하였을 때 surfcace의 roughness 가 증가함을 알 수 있었다. 이 연구 결과는 strained Si 가 가지고 있는 strained Si 내에서 n-FET 와 P-FET사이의 불균형에 대한 해결과 좀 더 발전된 형태인 fully Depleted Strained Si 제작에 기여할 것으로 보인다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.1
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• pp.9-13
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• 1982

The purpose of this experiment is to evaluate the noise dependency on the gate dimensions of the P-ch MOSFET which is fabricated of p+ sourse, drain, and gate electrode doped with PH$_3$ gas in type-N Si sudstrate. Experimental results indicate that: for the constant gate area and reletively thick films, noise level tends to decrease for the W/L ratio over unity, which generally conforms with theoretical observations, but its variation with the change in the thickness of film is less than the theoretically predicted for the W/L ratio below unity.

• Korean Journal of Soil Science and Fertilizer
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• v.3 no.1
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• pp.17-21
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• 1970

To determine the effects of the silicate and the phosphate on the rice seedlings, 200 grams dry soil of the paddy field taken in the petri dish of 15cm diameter were treated with three levels of silicate(wollastonite) and phosphate. And the same amounts of nitrogen and potash were added constantly to each treated petridish. 100 grains of rice of which variety is Nongrim 25 were sown on each treated petridish simultaneously. After five times continuous culture, the rice plants and the soil were analyzed chemically and the results obtained are summarized as follows: 1. Dry matter weight of the rice seedlings was significantly increased to the increased phosphate absorption, on the other hand that was decreased when the silica absorption was increased. 2. The higher the available phosphate content in the soil after the experiments, the lower the silica content as well as absorption by the plant, and the $SiO_2/P_2O_5$ ratio in the plant was significantly decreased. 3. By the wollastonite application, the available silica, the exchangeable calcium in the soil after the experiment, and the silica content as well as silica absorption and $SiO_2/P_2O_5$ ratio in the rice plant was significantly increased. 4. Higher correlation coefficient was obtained between the exchangeable calcium amount and the silica content or silica/phosphate ratio in the rice plant than the available silica content in soil itself. 5. It is possible to control the silica/phosphate ratio in plant by the control of the silica/phosphate ratio in soil. 6. The relation between the silica/phosphate ratio in plant (y) and the available silica/phosphate ratio in soil (x) was $y=0.665+1.420x-0.0825x^2$ and the goodness of fit(r) was 82%.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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• pp.289-298
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• 1993

Properties in terms of the variation of the glass compositions, which were density (p), molar volume(Vm), atom/ion packing density (Dp), refractive index (nD), transformation temperature (Tg), dilatometric softening point (Td), thermal expansion coefficient (α), Young's modulus (E), and knoop hardness (KHN) were investigated in CaO-SiO2 glasses and CaO-P2O5-SiO2 glasses containing less than 10mole% of P2O5. Those properties were measured by density measurement kit, Abbe refractometer, dilatometer, ultrasonic pulse echo equipment, and micro hardness tester. When CaO content was increased in CaO-SiO2 glasses, p, Dp, nD, Tg, Td, α, E and KHN were increased, while Vm was decreased. When P2O5 was added to the CaO-SiO2 glasses with constant CaO/SiO2 ratio as 1.07, p, Dp, nD, Tg, Td, α, E and KHN were decreased, while Vm was increased. When the amount of P2O5 in glasses was kept constant, the changes of the properties with variation of CaO content in the CaO-P2O5-SiO2 glasses were very similar to those of CaO-SiO2 glasses. These phenomena could be explained by the structural role of P2O5 in the CaO-P2O5-SiO2 glasses, which was polymerization of siicate structures and resulted in [PO4] monomer structure in glasses. Due to this structural characteristics, the bond strength and packing density were changed with compositions. Proportional relationships between 1) np and Dp, 2) Tg, Td, α and CaO content, 3) E and Vm-1, and 4) KHN and P2O5 content were evaluated in this investigation.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.385-385
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• 2012

A two terminal N+/P/N+ junction device to replace the conventional selective transistor was studied as a bilateral switching device for spin transfer torque (STT) MRAM based on 3D device simulation. An N+/P/N+ junction structure with $30{\times}30nm$ area requires bi-directional current flow enough to write a data by a drain induced barrier lowering (DIBL) under a reverse bias at N+/P (or P/N+ junction), and high current on/off ratio of 106. The SiGe materials are widely used in hetero-junction bipolar transistors, bipolar compensation metal-oxide semiconductors (BiCMOS) since the band gap of SiGe materials can be controlled by changing the fraction and the strain epilayers, and the drift mobility is increased with the increasing Ge content. In this work, N+/P/N+ SiGe material based junction provides that drive current is increased from 40 to $130{\mu}A$ by increased Ge content from 10~80%. When Ge content is about 20%, the drive current density of SiGe device substantially increased to 2~3 times better than Si-based junction device in case of 28 nm P length, which is sufficient current to operation of STT-MRAM.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.198-198
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• 2010

The low-k SiOCH thin films were prepared by CCP-PECVD method using BTMSM(Bis-trimethylsilylmethane) precursors deposited on p-Si wafer. The structural complexity originate the complex refractive constants of the films, and resulted the elliptical polarization of the incident linearly polarized light source of Xe-ramp in the range from 190nm to 2100nm. Phase difference and amplitude ratio between s wave and p wave propagating through SiOCH thin film was studied. After annealing, the amplitude of p wave was reduced more than s wave, and phase difference between p and s wave was also reduced.

• Journal of Biomedical Engineering Research
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• v.15 no.2
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• pp.189-194
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• 1994

Effects of ${AI_2O_3}/{P_2O_5}$ ratio on the crystallization of a series of glasses with the nominal composition of 41.4wt % $SiO_2$, 35.0wt % CaO, 20.6wt % (${P_2O_5}$+${AI_2O_3}$) and 3.0wt% MgO were investigated with DTA, XRD and SEM. The major crystalline phases are apatite and anorthite. The glass transition temperature ($T_g$) and the softening point ($T_s$) are shifted to the upper temperature by increasing $AI_2O_3$ content. The temperature of apatite crystallization ($T_{p1}$) is increased by $AI_2O_3$ content, but the tempera¬ture of anorthite crystallization ($T_{p2}$) is not affected significantly. With increased of $AI_2O_3$, the apatite crystallization is decreased, but anorthite crystallization is increased.

• Journal of the Korean Vacuum Society
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• v.1 no.1
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• pp.176-182
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• 1992

t-Stress and junction leakage current characteristics of CVD-tungsten have been investigated. Stressversus continuous annealing temperature plot. shows hysteresis curve where the stress level of the cooling curveis higher than that of the heating curve. It is found that the thermal and intrinsic stress of tungsten film depositedby SiH4 reduction is higher than that by Hz reduction.The tungsten film deposited by SiHl reduction is in the tensile stress state below 700"Cnd the stress ofthe film decreses with increasing annealing temperature. The stress state changes into compressive stress atabout 700"Cnd the compressive stress increases rapidly with increasing temperature.Leakage current of the n+/p diode increases rapidly especially in the range of 400-450$^{\circ}$C with increasingdeposition temperature of the CVD-W by SiH4 reduction, which is due to the Si consumption by W encroachment.On the other hand leakage current of the n+/p diode slightly increases with increasing SiH4/WF6 ratio.h increasing SiH4/WF6 ratio.