• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1301-1304
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• 2007

We have investigated degradation of short channel n-type poly-Si TFTs with LDD under high gate and drain voltage stress due to self-heating. We have found that the threshold voltage of short channel TFT is shifted to negative direction on the selfheating stress, whereas the threshold voltage of long channel is moved to positive direction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.151-151
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• 2008

바이폴러 트랜지스터(이하 BJT)의 고온 콜렉터-베이스 역전압 수명시험을 실시하였고, 수영시험 전후의 특성평가를 통해 BJT의 고장모드를 분석하였다. 시험조건은 주위온도 $150^{\circ}C$에서 콜렉터-베이스 정격 역전압의 80%를 인가한 상태에서 실시하였으며, 시료수는 57개이고 최종 목표 시험시간은 2,000시간이다. 중간측정을 통해 BJT의 특성열화를 관찰하였으며, 1,500시간 경과 후 1개 시료에서 제품규격을 벗어나는 데이터가 측정되었다. 해당 시료를 분석한 결과 콜렉터-베이스 누설전류 및 전류이득($\beta$)이 증가하였고, 저주파에서의 junction capacitance 가 정상품 대비 크게 관찰되었다. 측정결과를 통해 누설전류 증가 및 이득이 증가한 원인을 추정하였다.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.687-690
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• 2003

Experimental results are presented for gate oxide degradation and its effect on device parameters under negative and positive bias stress conditions using NMOSFET's with 3 nm gate oxide. The degradation mechanisms are highly dependent on stress conditions. For negative gate voltage, both hole- and electron-trapping are found to dominate the reliability of gate oxide. However, with changing gate voltage polarity, the degradation becomes dominated by electron trapping. Statistical parameter variations as well as the "OFF" leakage current depend on those charge trapping. Our results therefore show that Si or O bond breakage by electron can be another origin of the investigated gate oxide degradation.gradation.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.30-36
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• 1997

AlGaAs/GaAs HBTs are developed well enough to be commercialized as an active device in optical transmission system, but there remains the unanswered questions about reliability. In this paper we applied the reverse constant current stress at the high voltage in avalanche region for a long time to find out a new degradation mechanism of junctrion I-V. The unction off-set voltage at which the current vanishes to zero was shifted to the negative direction of applied bias due to the increment of leakage current as the stress time increases. It was identified that the degradation was induced by the hot carriers which were generated at space charge region and trapped at the interface between GaAs base and the passivation nitride enhancing the electric field across the nesa edge.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.695-696
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• 2008

This paper deals with the reduction of DC component of cogging toruqe by using the heat treatment of the stator core. The stator core is made of electrical steel sheared by the punching die. From the punching process, large mechanical stress at the edge of stator tooth induces significant plastic and elastic deformation and influences magnetic properties. Then, these phenomenon in the sheared region has influence on the magnetic unbalance in the air-gap of motor. This paper investigated the effect of the punching process on the magnetization process and the mechanical deformation and proposed the stress relief annealing method for the reduction of friction torque among one of motor characteristics.

• Korean Journal of Adult Nursing
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• v.17 no.5
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• pp.783-792
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• 2005

Purpose: This study was conducted to meta-analyze the effects of hardiness on health-related variables. Method: After review of 19 studies performed by Korean nurses, research variables, statistical data(r or F), and other methodological data were extracted and coded. Research variables were categorized under 5 groups such as health-related behavior, well-being, adaptation, stress, and support according to conceptual similarity. Using SAS program, 20 research variables and 34 effect sizes were calculated after eliminating heterogeneous data by Q-test, Results: Effects of hardiness on whole research variables was .512 and ranged from .322 to .643 by categories. The greatest effect was obtained from well-being category, whereas the smallest effect from stress category. All effect sizes were statistically significant. But fail-safe numbers were small and failed to achieve reasonable tolerance level. Conclusion: Results of meta-analysis indicated that hardiness has a moderate effect on health-related variables. But for improving the reliability of the results by minimizing publication bias, the more hardiness studies should be done.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.2
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• pp.139-144
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• 2013

Negative bias temperature instability (NBTI) has become a major factor determining circuit reliability. The effect of the NBTI on the circuit performance depends on the duty cycle which represents the stress and recovery conditions of each device in a circuit. In this paper, we propose an analytical model to perform more accurate duty cycle estimation at the gate-level. The proposed model allows accurate (average error rate: 3%) computation of the duty cycle without the need for expensive transistor-level simulations Furthermore, our model estimates the waveforms at each node, allowing various aging effects to be applied for a reliable gate-level circuit aging analysis framework.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.247-251
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• 2002

In this paper the maximum current carrying capability of ACAs flip chip joint is investigated based on two failure mechanisms: (1) degradation of the interface between gold stud bumps and aluminum pads; and (2) ACA swelling between chips and substrates under high current stress. For the determination of the maximum allowable current, bias stressing was applied to ACAs flip chip joint. The current level at which current carrying capability is saturated is defined as the maximum allowable current. The degradation mechanism under high current stress was studied by in-situ monitoring of gold stud bump-aluminum pad ACA contact resistance and also ACA junction temperature at various current level. The cumulative failure distributions were used to predict the lifetime of ACAs flip chip joint under high current stressing. These experimental results can be used to better understand and to improve the current carrying capability of ACA flip chip joint.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.512-518
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• 1996

Amorphous carbon nitride (a-C:N) multilayerfilms are formed by using altermating conditions during film deposition in are ion plating process. Because hard a-C:N films prepared with suitable megative bias voltages have large compressive stress, it is difficult to increase film thickness more than 200nm. Preparing multilayer films composed of hard layers and soft layers, we can grow thick multilayer films on Si and SKH steel substrate. The total thickness of multilayer films is more than 1$\mu\textrm{m}$. The multilayer films are several times thicker than the single layer films and almost equal in hardness and internal stress to the single layer ones. X-ray photoelectron spectroscopy(XPS) and Raman spectroscopy reveal that multilayer films equal to single layer films in structure, which is similar to the structure of DLC films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.1
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• pp.6-9
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• 2020

Thin film transistors (TFTs) with large-area, high mobility, and high reliability are important factors for next-generation displays. In particular, thin transistors based on IGZO oxide semiconductors are being actively researched for this application. In this study, several methods for improving the reliability of a-IGZO TFTs by applying various materials on a passivation layer are investigated. In the literature, inorganic SiO₂, TiO₂, Al₂O₃, ZTSO, and organic CYTOP have been used for passivation. In the case of Al₂O₃, excellent stability is exhibited compared to the non-passivation TFT under the conditions of negative bias illumination stress (NBIS) for 3 wavelengths (R, G, B). When CYTOP passivation, SiO₂ passivation, and non-passivation devices were compared under the same positive bias temperature stress (PBTS), the Vth shifts were 2.8 V, 3.3 V, and 4.5 V, respectively. The Vth shifts of TiO₂ passivation and non-passivation devices under the same NBTS were -2.2 V and -3.8 V, respectively. It is expected that the presented results will form the basis for further research to improve the reliability of a-IGZO TFT.