Modeling of Charge-to-Breakdown with an Electron Trapping Model for Analysis of Thermal Gate Oxide Failure Mechanism in SiC Power MOSFETs

The failure mechanism of thermal gate oxide in silicon carbide (SiC) power metal oxide semiconductor field effect transistors (MOSFETs), whether it is field-driven breakdown or charge-driven breakdown, has always been a controversial topic. Previous studies have demonstrated that the failure time of thermally grown silicon dioxide (SiO2) on SiC stressed with a constant voltage is indicated as charge driven rather than field driven through the observation of Weibull Slope β. Considering the importance of the accurate failure mechanism for the thermal gate oxide lifetime prediction model of time-dependent dielectric breakdown (TDDB), charge-driven breakdown needs to be further fundamentally justified. In this work, the charge-to-breakdown (QBD) of the thermal gate oxide in a type of commercial planar SiC power MOSFETs, under the constant current stress (CCS), constant voltage stress (CVS), and pulsed voltage stress (PVS) are extracted, respectively. A mathematical electron trapping model in thermal SiO2 grown on single crystal silicon (Si) under CCS, which was proposed by M. Liang et al., is proven to work equally well with thermal SiO2 grown on SiC and used to deduce the QBD model of the device under test (DUT). Compared with the QBD obtained under the three stress conditions, the charge-driven breakdown mechanism is validated in the thermal gate oxide of SiC power MOSFETs.

An Investigation of Body Diode Reliability in Commercial 1.2 kV SiC Power MOSFETs with Planar and Trench Structures

The body diode degradation in SiC power MOSFETs has been demonstrated to be caused by basal plane dislocation (BPD)-induced stacking faults (SFs) in the drift region. To enhance the reliability of the body diode, many process and structural improvements have been proposed to eliminate BPDs in the drift region, ensuring that commercial SiC wafers for 1.2 kV devices are of high quality. Thus, investigating the body diode reliability in commercial planar and trench SiC power MOSFETs made from SiC wafers with similar quality has attracted attention in the industry. In this work, current stress is applied on the body diodes of 1.2 kV commercial planar and trench SiC power MOSFETs under the off-state. The results show that the body diodes of planar and trench devices with a shallow P+ depth are highly reliable, while those of the trench devices with the deep P+ implantation exhibit significant degradation. In conclusion, the body diode degradation in trench devices is mainly influenced by P+ implantation-induced BPDs. Therefore, a trade-off design by controlling the implantation depth/dose and maximizing the device performance is crucial. Moreover, the deep JFET design is confirmed to further improve the body diode reliability in planar devices.

Efficacy and safety of Cerebrolysin treatment in early recovery after acute ischemic stroke: a randomized, placebo-controlled, double-blinded, multicenter clinical trial

Background and Purpose : The aim of this study was to evaluate the efficacy, safety, and tolerability of cerebrolysin in the early recovery phase after acute ischemic stroke. Methods. This prospective, randomized, double-blinded, placebo-controlled, multicenter, parallel-group study enrolled a total of 100 patients within 18 h after the onset of stroke. The patients were treated with Cerebrolysin (30 mL over seven days followed by 10 mL until day 30) or placebo once daily over a period of four weeks. Efficacy was primarily assessed by the NIH Stroke Scale at day 30, and additional parameters included the modified Rankin Scale, the Clinical Global Impression, the Patient Global Satisfaction (PGS) and the Mini Mental State Examination (MMSE). Nonparametric statistical procedures employing the Wilcoxon-Mann-Whitney test were used for data analysis. Safety and tolerability were assessed by adverse events, vital signs, and laboratory parameters. Results.The estimated effect size on the change from baseline in the NIH Stroke Scale on day 30 indicated a medium to large superiority of cerebrolysin compared to placebo (Mann-Whitney [MW] 0.66; 95% confidence interval [CI] 0.55-0.78, P=0.005). Similar effect sizes were reported for the modified Ranking Scale (MW 0.65; 95% CI 0.54-0.76; P=0.010) and the Clinical Global Impression (MW 0.70; 95% CI 0.55-0.85; P=0.006). Effect sizes in the MMSE and PGS did not reach statistical significance. No significant group differences were seen in any of the safety parameters. Conclusions. Cerebrolysin was effective, safe, and well tolerated in the early recovery phase after acute ischemic stroke and significantly improved neurological and global function outcomes compared to placebo.

Chromosomal location of the cadmium uptake gene (Cdu1) in durum wheat

Levels of the heavy metal cadmium (Cd) in food products are a food safety concern. Grain Cd is higher in durum (Triticum turgidum L. var. durum) than in common wheat, so reduction of Cd in durum grain is a priority of breeding programs. Previous research demonstrated that a single dominant gene, Cdu1, confers the low grain Cd phenotype, but the map location of the gene is not known. A doubled haploid population segregating for Cd concentration, developed from the cross of W9262-260D3 (a Kyle*2/Biodur inbred selection with low Cd uptake) and Kofa (high Cd uptake) and mapped with microsatellite markers, was used to locate Cdu1. Grain Cd concentration was determined by standard laboratory methods on field grain samples in 2000 and 2001. The Cd concentration segregated bimodally, allowing Cdu1 to be mapped qualitatively as well as quantitatively with quantitative trait locus analysis. The Cdu1 gene mapped to the long arm of chromosome 5B.