ADI-FDTD Method With Fourth Order Accuracy in Time

This letter presents an unconditionally stable alternating direction implicit finite-difference time-domain (ADI-FDTD) method with fourth order accuracy in time. Analytical proof of unconditional stability and detailed analysis of numerical dispersion are presented. Compared to second order ADI-FDTD and six-steps SS-FDTD, the fourth order ADI-FDTD generally achieves lower phase velocity error for sufficiently fine mesh. Using finer mesh gridding also reduces the phase velocity error floor, which dictates the accuracy limit due to spatial discretization errors when the time step size is reduced further.     

Pi-coefficient analysis of update algorithms for adaptive systems

This paper finds the appropriate pi-coefficients for a parameter estimation adaptive system and uses them to analyze the stability of two estimation algorithms. The estimation error dynamics of the system are modeled by a linear time-invariant subsystem and a nonlinear time-varying update law in a feedback loop. Then the so-called max-p problems are formulated and solved to obtain the pi-coefficients for the linear subsystem and nonlinear update low. For the investigated system, the quantitative results show that the least-squares update algorithm has larger stability range than that of the gradient algorithm, and the σ-modification scheme gives larger stability ranges for both algorithms.     

Fast alternating direction implicit method for efficient transient thermal simulation of integrated circuits

This paper presents fast alternating direction implicit (FADI) method for efficient transient thermal simulation of integrated circuits. The FADI method is formulated from Peaceman–Rachford's ADI and Douglas–Gunn's ADI methods. The update procedure of the proposed method has basic implicit form that features derivative‐free right‐hand side and hence, better efficiency and conciseness. Subsequently, through the basic implicit form of FADI method, the relationship between classical Peaceman–Rachford's and Douglas–Gunn's ADI methods can be clarified and elucidated in detail. A unified boundary condition that can cater to common kinds of boundary conditions in thermal simulation is also introduced. To further accelerate FADI method, the graphics processing unit is also utilized through Compute Unified Device Architecture implementation. It is shown that high efficiency gain can be achieved using the proposed FADI method through large time step size and data parallelism, while maintaining stability and good accuracy. As numerical illustration, an integrated circuit structure with microchannel cooling is demonstrated. Numerical results further ascertain the cooling effect of the microchannels. Copyright © 2015 John Wiley & Sons, Ltd.     

Asymmetric energy distribution of interface traps in n- and p-MOSFETs with HfO/sub 2/ gate dielectricon ultrathin SiON buffer layer

The variable rise and fall time charge-pumping technique has been used to determine the energy distribution of interface trap density (D/sub it/) in MOSFETs with a HfO/sub 2/ gate dielectric grown on an ultrathin (<1 nm)-SiON buffer layer on Si. Our results have revealed that the (D/sub it/) is higher in the upper half of the bandgap than in the lower half of the bandgap, and are consistent with qualitative results obtained by the subthreshold current-voltage (I--V) measurements, capacitance-voltage (C-V), and ac conductance techniques. These results are also consistent with the observation that n-channel mobilities are more severely degraded than p-channel mobilities when compared to conventional MOSFETs with SiO/sub 2/ or SiON as the gate dielectric.     

Experimental Evidence of the Fast and Slow Charge Trapping/Detrapping Processes in High- k Dielectrics Subjected to PBTI Stress

A single-pulse technique, with a wide range of pulse times, has been applied to study positive bias temperature instability in high-k nMOSFETs. It is shown that the charging phenomenon includes both fast and slow electron trapping processes with rather well-defined characteristic times, which differ by six orders of magnitude. On the other hand, the poststress charge relaxation cannot be described by a simple detrapping process, which makes identifying the dominant detrapping mechanism complicated.     

Comparison of On-The-Fly, DC Id–Vg, and Single-Pulse Methods for Evaluating Threshold Voltage Instability in High-κ nMOSFETs

Stress-induced degradation of the threshold voltage of high-kappa nMOSFETs measured by on-the-fly and single-pulse methods is investigated. It was found that the relaxation of the stress-induced threshold voltage (V_th) shift during stress interruption (sensing) time is primarily governed by the fast detrapping of charges trapped through the fast transient charging (FTC) process. Subtraction of the FTC contribution from the total stress time-dependent V_th shift provides a practical and convenient method for eliminating a major source of V_th relaxation, which results in identical lifetime estimations by the on-the-fly and pulsed methods     

Improved Ge Surface Passivation With Ultrathin SiOX Enabling High-Mobility Surface Channel pMOSFETs Featuring a HfSiO/WN Gate Stack

To realize high-mobility surface channel pMOSFETs on Ge, a 1.6-nm-thick SiO_X passivation layer between the bulk Ge substrate and HfSiO gate dielectric was introduced. This approach provides a simple alternative to epitaxial Si deposition followed by selective oxidation and leads to one of the highest peak hole mobilities reported for unstrained surface channel pMOSFETs on Ge: 332 cm² middotV^-1middots^-1 at 0.05 MV/cm-a 2times enhancement over the universal Si/SiO₂ mobility. The devices show well-behaved output and transfer characteristics, an equivalent oxide thickness of 1.85 nm and an I_ON/I_OFF ratio of 3times10³ without detectable fast transient charging. The high hole mobility of these devices is attributed to adequate passivation of the Ge surface     

Electrical characterization and analysis techniques for the high-κ era

Various conventional and novel electrical characterization techniques have been combined with careful, robust analysis to properly evaluate high-κ gate dielectric stack structures. These measurement methodologies and analysis techniques have enhanced the ability to separate pre-existing defects that serve as fast transient charging and discharging sites from defects generated with stress. In addition, the differentiation of electrically active bulk high-κ traps, silicon substrate interface traps, and interfacial layer traps has been effectively demonstrated.     

Skin hydration effects,physico‐chemical properties and vitamin E release ratio of vital moisture creams containing water‐soluble chitosans

Synopsis The effects of the addition of water‐soluble chitosans on skin hydration, physico‐chemical properties and vitamin E release ratio of vital moisture creams (vitamin E‐containing creams) were studied. Results show that vitamin E‐containing creams containing different molecular weights and/or concentrations of water‐soluble chitosans are pseudoplastic fluids. The apparent viscosity of vitamin E‐containing creams increased with increasing molecular weight and/or with increasing concentration of water‐soluble chitosans used in the formula. The apparent viscosities of those vitamin E‐containing creams containing 0.5% water‐soluble chitosan were higher than those containing 2% glycerol monostearate (control). The higher apparent viscosity of vitamin E‐containing creams obtained using water‐soluble chitosans improves the stability and enhances skin hydration of the creams thus prepared. Such creams containing water‐soluble chitosans were stable for more than 3 months during high temperature or cyclic temperature storage, whereas those containing glycerol monostearate had a shorter storage life of 2 months. Skin hydration in terms of water‐holding capacity of vitamin E‐containing creams containing 1.0% water‐soluble chitosan was superior to those containing 2% glycerol monostearate. No erythema occurred on shaved rabbit skin after applying vitamin E‐containing creams containing water‐soluble chitosans, and the vitamin E release ratios of these creams were similar to the cream containing 2% glycerol monostearate. Résumé Nous avons étudié le rôle de l’addition de chitosanes hydrosolubles dans une crème hydratante vitale, sur le taux de relargage de vitamine E, l’hydratation de la peau et les propriétés physiscochimiques de cette préparation. Les résultats montrent que les crêmes hydratantes vitales contenant différentes masses moléculaires et/ou concentrations de chitosanes hydrosolubles sont des fluides pseudo‐plastiques. La viscosité apparente des crêmes hydratantes vitales croit avec la masse moléculaire et/ou la concentration des chitosanes employés dans la formulation. La viscosité apparente de ces crèmes hydratantes vitales contenant 0.5% de chitosane hydrosoluble est supérieure à celle contenant 2% de monostéarate de glycérol (contrôle). La viscosité apparente plus élevée des crêmes hydratantes vitales obtenue grâce à la présence de chitosane hydrosoluble améliore la stabilité, accroit l’hydratation de la peau. Les crêmes hydratantes vitales contenant du chitosane hydrosoluble sont stables pendant 3 mois au cours d’un stockage à température élevée, en continu ou cyclique. Ceux contenant du monostéarate de glycérol ont une durée de conservation inférieure, de 2 mois. L’hydratation de la peau, en terme de capacité de rétention d’eau, pour les crêmes hydrantes vitales contenant 1% de chitosane hydrosoluble sont supérieures à celles contenant 2% de monostéarate de glycérol. Aucun érythème n’apparait sur une peau de lapin rasé après application de crême hydratante vitale contenant des chitosane hydrosolubles. Le taux de relargage de vitamine E des crêmes hydratantes vitales contenant des chitosanes hydrosolubles est semblable à celui des crêmes contenant 2% de monostéarate de glycérol.     

Impact of the trapping of anode hot holes on silicon dioxide breakdown

Hot holes are injected from the anode and trapped in thin silicon dioxide using constant voltage stress at large gate voltage. By comparing oxides having trapped holes with oxides in which the holes were detrapped, it is shown that the presence of trapped holes does not affect the breakdown of the oxide. Furthermore, as the temperature during stress is increased, less hole trapping is observed whereas the charge-to-breakdown of the oxide is decreased. The results show that although the trapping of hot holes injected using anode hole injection (AHI) may be partly responsible for defect generation in silicon dioxide, breakdown cannot be limited by the number of holes trapped in the oxide.