• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.8
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• pp.1-8
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• 2004

Experimental results are presented for gate oxide degradation, such as SILC and soft breakdown, and its effect on device parameters under negative and positive bias stress conditions using n-MOSFET's with 3 nm gate oxide. The degradation mechanisms are highly dependent on stress conditions. For negative gate voltage, both interface and oxide bulk traps are found to dominate the reliability of gate oxide. However, for positive gate voltage, the degradation becomes dominated mainly by interface trap. It was also found the trap generation in the gate oxide film is related to the breakage of Si-H bonds through the deuterium anneal and additional hydrogen anneal experiments. Statistical parameter variations as well as the “OFF” leakage current depend on both electron- and hole-trapping. Our results therefore show that Si or O bond breakage by tunneling electron and hole can be another origin of the investigated gate oxide degradation. This plausible physical explanation is based on both Anode-Hole Injection and Hydrogen-Released model.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.397-401
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• 2011

The response of lightning impulse voltage was explored in dielectric liquids employing hydrodynamic modeling with three charge carriers using the finite element method. To understand the physical behavior of discharge phenomena in dielectric liquids, the response of step voltage has been extensively studied recently using numerical techniques. That of lightning impulse voltage, however, has rarely been investigated in technical literature. Therefore, in this paper, we tested impulse response with a tip-sphere electrode which is explained in IEC standard #60897 in detail. Electric field-dependent molecular ionization is a common term for the breakdown process, so two ionization factors were tested and compared for selecting a suitable coefficient with the lightning impulse voltage. To stabilize our numerical setup, the artificial diffusion technique was adopted, and finer mesh segmentation was generated along with the axial axis. We found that the velocity from the numerical result agrees with that from the experimental result on lightning impulse breakdown testing in the literature.

• Journal of Electrical Engineering and information Science
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• v.2 no.3
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• pp.71-76
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• 1997

A lot of experiments and analyses have been done to determine the aging mechanism of mica-epoxy composite material used for large generator stator windings in order to estimate remaining life of the generator for last decades. After degrading artificially the mica-epoxy composite material, the surface analysis is performed to analyze breakdown mechanism of insulation in air and hydrogen atmosphere; i) In the case of air atmosphere, it is observed that an aging propagation from conductor to core by partial discharge effect and the formation of cracks between layers is widely carbonized surface. ii) In case of hydrogen atmosphere, the partial discharge effect is reduced by the hydrogen pressure (4kg/$\textrm{cm}^2$). Potassium ions forming a sheet of mica is replaced by hydrogen ions, which can lead to microcracks. It is confirmed that the sizes of crack by SEM analysis are 10∼20[$\mu\textrm{m}$] in length under air, and 1∼5[$\mu\textrm{m}$] in diameter, 10∼50[$\mu\textrm{m}$] in length under hydrogen atmosphere respectively. The breakdown mechanism of sttor winding insulation materials which are composed of mica-epoxy is analyzed by the component of materials with EDS, SEM techniques. We concluded that the postassium ions of mica components are replaced by H\ulcorner, H$_3$O\ulcorner at boundary area of mica-epoxy and/or mica-mica. It is proposed that through these phenomena, the conductive layers of potassium enable creation of voids and cracks due to thermal, mechanical, electrical and environmental stresses.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.969-972
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• 1992

It is shown that the ac breakdown strength, treeing phenomena, oxidation level, and crystallinity of unaged and aged distribution CV cables vary with XLPE insulations (characterizing anti-oxidation) and curing process. The maximum size of bow-tie tree in insulation influenced on the decrease of ac breakdown strength and the increase of oxidation level and crystallinity of XLPE according to aging time lead to increase the size and density of bow-tie trees.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.426-428
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• 1989

As a first phase of plasma study intended for semiconductor processing research, we have studied the discharge phenomena. In particular, we have obtained a specific formula for the breakdown voltage as a function of the neutral state pressure of reactive gases. Our experimental results with H2,O2,Ar,CF4 seem ro verify this formula. In addition we find the voltage levels for various gases in the descending order of CF4>O2=Ar>H2 in high pressure region, while H2>CF4>O2>Ar in low pressure region. When H2 and CF4 were mixed, we observe the overall voltage dominated by the gas with lower breakdown volotage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.961-964
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• 2003

This paper presents the temperature annealing effect on the dark current of the InGaAs waveguide photodiodes, which are developed for high-speed optical receivers. The interesting experimental phenomena were observed that the dark current is significantly decreased and the breakdown voltage is slightly increased after annealing at $250^{\circ}C$ whereas the dark current and the breakdown voltage are almost constant after annealing at $200^{\circ}C$. Based on the experimental results, the long-term annealing is more effective for the dark current improvement than the conventional curing process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.262-265
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• 2001

In order to investigate the water tree degradation behavior on XLPE cable, direct voltage of 200 to 800V has been applied to the material at $50^{\circ}C\sim100^{\circ}C$. and the water tree property has been correlated with voltage and temperature in this study. The leakage current was shown to increase as temperature increased and the Ohm's law was generally satisfied in this experiment though some experimental errors were found. The leakage current was shown to decrease and reach to the stable state with time. It was also shown that the time for the stabilization of leakage current was lessened as voltage increased

• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.329-337
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• 2001

This simulator is developed for the analysis of a MOSFET based on Thermally Coupled Energy Transport Model(TCETM). The simulator has the ability to calculate not only stationary characteristics but also non - stationary characteristics of a MOSFET. It solves basic semiconductor devices equations including Possion equation, current continuity equations for electrons and holes, energy balance equation for electrons and heat flow equation, using finite difference method. The conventional semiconductor device simulation technique, based on the Drift-Diffusion Model (DDM), neglects the thermal and other energy-related properties of a miniaturized device. I, therefore, developed a simulator based on the Thermally Coupled Energy Transport Model (TCETM) which treats not only steady-state but also transient phenomena of such a small-size MOSFET. In particular, the present paper investigates the breakdown characteristics in transient conditions. As a result, we found that the breakdown voltage has been largely underestimated by the DDM in transient conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.82-85
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• 2000

The less sensitive structure to the surface effect has been presented utiliting an undoped GaAs layer on the n-GaAs channel. The undoped layer has been found to be effective to supress the frequency dispersion phenomena caused by a surface trapping effect and to raise the MESFET's performance. The gate structure, with an undoped layer underneath the gate metal has been found to be effective to improve the breakdown voltage. GaAs MESFETS with different physical structures are fabricated and DC characteristics are measued. GaAs MESFET's are fabricated on epi-wafers which have an undoped GaAs layer in between n+ and n GaAs layers grown by MBE.

• Electrical & Electronic Materials
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• v.1 no.1
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• pp.78-85
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• 1988

본 논문에서는 SiH$_{4}$-N$^{2}$ 혼합가스에 의한 PECVD 방법으로 퇴적시킨 실리콘 질화막의 신뢰성을 평가하기 위해 절연파괴 분포와 TDDB(Time Dependent Dielectric Breakdown)특성을 고찰하였다. MNS 캐패시터의 절연파괴 분포는 7-8NV/cm의 전계세기에서 그 파괴전계가 집중되었으며 전계와 온도 stress에 의해 파괴시간이 지수함수적으로 감소함을 알 수 있었다. 아울러 이러한 TDDB 특성과 계면준위 밀도 및 SiN 막내의 공간전하형성과의 관련성을 고찰하였다.