Function Of Stress Parameters Research Articles

Failure analysis and lifetime assessment of IGBT power modules at low temperature stress cycles

Lifetime models of high-power Insulated Gate Bipolar Transistors modules express the number of cycles to end of life as a function of stress parameters. These models are normally developed based on experimental data from accelerated power-cycling tests performed at predefined temperature stress conditions as, for example, with temperature swings above 60 °C. However, in real power converters applications, the power modules are usually stressed at temperature cycles not exceeding 40 °C. Thus, extrapolating the parameters of lifetime models developed using data from high-temperature stress cycles experiments might result in erroneous lifetime estimations. This paper presents experimental results from power cycling tests on high-power Insulated Gate Bipolar Transistors modules subjected to low temperature stress cycles of 30 and 40 °C. Therefore, devices experience still accelerated aging but with stress conditions much closer to the real application. Post-mortem failure analysis has been performed on the modules reaching end-of-life in order to identify the failure mechanism. Finally, the number of cycles to end-of-life obtained experimentally is fit with a state-of-the-art lifetime model to assess its validity at low temperature stress cycles. Challenges and limitations on data fitting to this lifetime model and the impact of various stress parameters on the anticipated failure are also presented.

Toward an empirical ground motion prediction equation for France: accounting for regional differences in the source stress parameter

In low-to-moderate seismicity regions such as metropolitan France, characterized by limited strong-motion records in the magnitude-distance range of interest for seismic hazard assessment, the derivation of empirical ground motion prediction equations (GMPEs) is a major challenge. In this study, we take advantage of the RESORCE-2013 database ( http://resorce-portal.eu/ ) that contains uniformly processed records for the Pan-European region including relevant number of French records. After discussing the metadata for French events and stations, we first derive a base-case GMPE that is used to investigate the within-event and between-event residuals. The short-period between-event residuals for French (and Swiss) events show larger variability with respect to larger magnitude events in other regions. We show that the between-event residuals are clearly correlated with the stress parameter and that such larger variability can be explained by accounting for stress-parameter scaling. We derive an empirical scaling of ground motion with stress parameter that is consistent across regions and with the scaling predicted by stochastic GMPEs. This suggests that the scaling of ground motion with stress parameter for a given magnitude is largely region independent whereas the absolute stress parameter values may vary regionally. Based on these results we propose to adopt the scaling model as a function of stress parameter and magnitude by Yenier and Atkinson (Bull Seismol Soc Am 105(4):1989–2009, 2015) by adapting the reference stress parameter to our target regions. By accounting for stress parameter scaling in the GMPE we reduce the between-event variability for French and Swiss small-magnitude events. Finally, we investigate the aleatory variability (σ) of the GMPE and its components (τ, ϕ, ϕss). We propose a heteroscedastic σ model to be used when the stress-parameter scaling is not considered in the GMPEs due to lack of information. If enough information on the stress-parameter is available the adjusted GMPE can be applied using a homoscedastic σ. Despite using small events, the ϕss for French stations is found to be consistent with other studies and confirms the stability of ϕss across different regions and datasets.

Deformation criterion of salt rock failure

The author offers a new deformation criterion for the compressive strength of salt rock specimens. The limiting principal strain is a function of stress parameter in the form of a ratio of hydrostatic pressure and stress intensity. The safety factor based on the deformation criterion is defined. The numerical modeling of experimental compression of various geometry specimens produces the deformation criterion for sylvinite and carnallite of Upper Kama deposit. The offered criterion is applicable to assessment of salt rock stability.

Charge Trapping in HfYOx Gate Dielectrics on Strained-Si

HfYOx gate dielectric has been deposited on strained-Si/Si0.8Ge0.2 by RF co-sputtering of HfO2 and Y2O3 targets. Chemical and electrical properties have been demonstrated by x-ray photo electron spectroscopy (XPS), capacitance-voltage (C-V) and leakage current (I-V) characteristics. The reliability characteristics of HfYOx gate dielectric stacks on strained-Si/Si0.8Ge0.2 have been investigated under different field (2.3-6MV/cm) and constant current stress (10-25mA/cm2) of different amplitude and fluence in order to analyze the degradation of oxide as a function of stress parameters. Oxide trap charge and trap centroid location have been analyzed after constant current stressing.

Reliability assessment of SiO 2/ZrO 2 stack gate dielectric on strained-Si/Si 0.8Ge 0.2 heterolayers under dynamic and AC stress

The reliability characteristics of SiO 2/ZrO 2 gate dielectric stacks on strained-Si/Si 0.8Ge 0.2 have been investigated under dynamic and pulsed voltage stresses of different amplitude and frequency in order to analyze the transient response and the degradation of oxide as a function of stress parameters. The current transients observed in dynamic voltage stresses have been interpreted in terms of the charging/discharging of interface and bulk traps. The evolution of the current during unipolar pulsed voltage stresses shows the degradation being much faster at low frequencies than at high frequencies. Results have been compared with those obtained after CVS, as a function of injected charge and pulse frequency.