Breakdown Distribution Research Articles

Time-dependent dielectric breakdown in pure and lightly Al-doped Ta2O5 stacks

The time-dependent dielectric breakdown (TDDB) characteristics of 7 nm pure and lightly Al-doped Ta2O5 (equivalent oxide thickness of 2.2 and 1.5 nm, respectively) with W gate electrodes in MOS capacitor configuration are studied using gate injection and constant voltage stress. The effect of both the process-induced defects and the dopant on the breakdown distribution, and on the extracted Weibull slope values, are discussed. The pre-existing traps which provoke weak spots dictate early breakdowns. Their effect is compounded of both the stress-induced new traps generation (percolation model is valid) and the inevitable lower-k interface layer in the region with long time-to-breakdown. The domination of one of these competitive effects defines the mechanism of degradation: the trapping at pre-existing traps appears to dominate in Ta2O5; Al doping reduces defects in Ta2O5, the generation of new traps prevails over the charge trapping in the doped samples, and the mechanism of breakdown is more adequate to the percolation concept. The doping of high-k Ta2O5 even with small amount (5 at.%) may serve as an engineering solution for improving its TDDB characteristics and reliability.

Area Dependence of Reliability Characteristics for Atomic Layer Deposition HfO2 Film under Static and Dynamic Stress

The reliability characteristics of high-k gate stacks of HfO2 films under static and dynamic stresses have been investigated. Weibull slopes (β), area scaling factor, and lifetime projection model have been checked, in order to further understanding of the breakdown mechanism of HfO2 gate stacks. Irrespective of the static and dynamic stress, the breakdown distributions of HfO2 capacitors with various areas can be merged to a single Weilbull plot, suggesting that the dielectric breakdown is intrinsic for both cases. This study shows that a higher frequency and a lower duty cycle in the bipolar stress resulted in a longer lifetime enhancement. With respect to gate area effect, the amount of lifetime enhancement increases as the gate area decreases. A higher weibull slope is observed on a smaller gate area under dynamic stress.

Area Dependence of Reliability Characteristics for Atomic Layer Deposition HfO2 Film under Static and Dynamic Stress

The reliability characteristics of high-k gate stacks of HfO2 films using atomic layer deposition method have been investigated. Weibull slopes (β), area scaling factor, and lifetime projection model have been checked for static and dynamic stress, in order to further understanding of the breakdown mechanism of HfO2 gate stacks. Irrespective of the static and dynamic stress, the breakdown distributions of HfO2 capacitors with various areas can be merged to a single Weibull plot, suggesting that the dielectric breakdown is intrinsic for both cases. This study shows that a higher frequency and lower duty cycle in the bipolar stress resulted in a longer lifetime enhancement. Additionally, increasing the stress time and voltage of the opposite polarity in the bipolar stress enhanced the dielectric breakdown lifetimes as well. With respect to gate area effect, the amount of lifetime enhancement increases as the gate area decreases. A higher weibull slope is observed on a smaller gate area under dynamic stress.

Prospects for using cathodoluminescence in SEM to study the distribution and types of breakdown in glass insulators

A method for detecting dielectric breakdown in the signal of cathodoluminescence in SEM is compared with both capacitive and secondary-emission methods. In the investigated samples of glass dielectrics, breakdowns of two types are found: surface and emission. The prospects for using cathodoluminescence to detect and localize defects in insulators that lower the breakdown voltage are discussed.

Epidemiology of cheerleading injuries presenting to NEISS hospitals from 2002 to 2007

Cheerleading has developed into a complex sport utilizing aspects of dance, gymnastics/tumbling, single- and multiple-partner stunts, and tosses in complex displays. Stunting and tosses elevates one or multiple participants into the air supported by teammates putting all at significant injury risk. We reviewed all cheerleading injuries captured by the US Consumer Product Safety Commission National Electronic Injury Surveillance System from 2002 to 2007 that presented to US Emergency Departments and used the new narrative feature added in 2002 to better differentiate injury context and severity. There were 4,245 cases of cheerleaders presenting to National Electronic Injury Surveillance System Emergency Departments from 2002 to 2007 with an average age of 14.6 years, and 96.3% were female. Most of these injuries could be treated as outpatients (97.9%). The extremities were most likely affected, 2,610 (61.5%), with further distribution breakdown as follows: upper extremity 1,339 (31.5%), lower extremity 1,271 (29.9%), head and neck 1,085 (25.6%), trunk 491 (11.6%), and other 48.0 (1.1%). The type of injury sustained in descending order is as follows: sprains/strains 1,871 (44.1%), fractures 709 (16.7%), and contusions 684 (16.1%). The most common mechanism of injury was a collision between two or more cheerleaders (1,242; 29.3% overall), followed by stunting (841; 19.8% overall), tumbling (478, 11.3% overall), and tossing (105, 2.5% overall). Subset analysis was performed on fracture, admit, and severe injury groups. The upper extremity was the most commonly injured part of the body and sustained a significantly greater number of fractures. However, head injuries were more likely to be severe. The value of a more detailed database specific to cheerleading could be invaluable in identifying risk factors and activity-specific injury patterns and facilitate implementing safety measures. III.

Functionalization of Polypropylene with High Dielectric Properties: Applications in Electric Energy Storage

Biaxial-oriented polypropylene (BOPP) thin films are currently used as dielectrics in state-of-the-art capacitors that show many advantages, such as low energy loss and high breakdown strength, but a limited energy density ( 600 MV/m. The PP-OH dielectric demonstrates a linear reversible charge storage behavior with high releasing energy density > 7 J/cm3 (2 - 3 times of BOPP) after an applied electric field at E = 600 MV/m, without showing any significant increase of energy loss and remnant polarization at zero electric field. On the other hand, a cross-linked polypropylene (x-PP) exhibits an e ~ 3, which is independent of a wide range of temperatures and frequencies, slim polarization loops, high breakdown strength (E = 650 MV/m), narrow breakdown distribution, and reliable energy storage capacity > 5 J/cm3 (double that of state-of-the-art BOPP capacitors), without showing any increase in energy loss.

Joint determination of optimal safety stocks and production policy for an imperfect production system

In this article, we develop an imperfect economic manufacturing quantity (EMQ) model for an unreliable production system subject to process deterioration, machine breakdown and repair and buffer stock. The basic model is developed under general process shift, machine breakdown and repair time distributions. We suggest a computational algorithm for determination of the optimal safety stock and production run time which minimize the expected cost per unit time in the steady state. For a numerical example, we illustrate the outcome of the proposed model and perform a sensitivity analysis with respect to the model-parameters which have direct influence on the optimal decisions.

Precipitate Formation and Effects on Electrical and Mechanical Properties of Fluorinated Silicon Oxide

Precipitates appear on fluorine-doped silicon oxide (SiOF) film when the film surface is exposed to atmospheric air. They are flake-type and hexagonal-shaped and show up rapidly after initiation, and then densely clustered. Energy-dispersive X-ray (EDX) analysis results of the precipitates show that mainly Si & O are detected. From the analysis of Raman spectra, the decreased intensities at about 600 cm-1 and 500 cm-1 post precipitation indicates the reduction of strained low-order ring structure in SiOF film. It is found that the dielectric constant of SiOF films initially increases at exposure to air and is attributable to the absorption of water, and then on the contrary a declining trend of the dielectric constant was observed after precipitation. From the Current-Voltage (I-V) characteristics, there is an apparent shift of the breakdown distribution to lower values of electric field for the SiOF films post-precipitation. Slight but appreciable reduction in hardness could be observed along exposure to air and precipitation. Precipitation on SiOF film at exposure to humid air is accompanied by reconstruction in structure, leading to further increase in film porosity and reduction in film rigidity.

Initial leakage current related to extrinsic breakdown in HfO 2/Al 2O 3 nanolaminate ALD dielectrics

Multiple successive breakdown events are reported for HfO 2/Al 2O 3 nanolaminate dielectrics grown by atomic-layer deposition. The first breakdown distribution is not a Weibull distribution and shows a long TBD tail at high failure percentiles. Analysis of the correlation between time-to-breakdown and initial current leakage allows identifying this tail with extrinsic breakdown. Screening of the data to eliminate the extrinsic tail demonstrates that the successive breakdown events are completely uncorrelated and perfectly match the successive breakdown theory. The statistical correlation between initial current and extrinsic breakdown distribution is explained in terms of variations of the unintentional interfacial SiO x layer at the silicon substrate/dielectric interface.

Cross-linking effect on dielectric properties of polypropylene thin films and applications in electric energy storage

A family of cross-linked polypropylene (x-PP) thin film dielectrics is systematically studied to understand the cross-linking effect on the dielectric properties. Evidently, the butylstyrene (BSt) cross-linkers increase both the dielectric constant (ε) and breakdown strength (E), without increasing energy loss. An x-PP dielectric, with 3.65 mol % BSt cross-linkers, exhibits a ε∼3, which is independent of a wide range of temperatures and frequencies, slim D-E hysteresis loops, high breakdown strength (E=650 MV/m), narrow breakdown distribution, and reliable energy storage capacity >5 J/cm3 (double that of state-of-the-art biaxially oriented polypropylene capacitors), without showing any increase in energy loss.

Poverty Changes during the Three Recent Development Plans in Iran (1995-2007)

AbstractThe purpose of this study is to analyse the degree of poverty in Iran and how it changed over time during the second, third and fourth (first three years) five-year national development plans (1995-2007). It does this by documenting overall poverty levels and poverty within regional subgroups, using the micro-level data set of household expenditure survey conducted by the Statistical Centre of Iran (SCI) in 1995, 1999, 2004 and 2007. I have found an increase in all poverty measures in rural regions and a decrease in urban areas during the second development plan (1995-1999). The country as a whole also experienced a considerable poverty reduction over the third development plan (1999-2004) under Khatami’s presidency. However, all poverty measures suggest that during Ahmadinejad Administration (2004-2007) poverty has risen. This paper also examines the distribution of poverty breakdown by the regional status of households in Iran. The incidence, intensity and severity of poverty are higher in rural than urban areas in Iran. Regional decompositions show that although poverty was spread throughout the country, the intensity of poverty in some provinces such as Systan-Balochestan, Kermanshah, Kordestan, Hamadan and Ilam was more pronounced. The results also suggest that the contribution of the “southeast” and “west” regions (including above mentioned provinces) to the national poverty were increased during the second, third and fourth plans. This might be attributed to the fact that these provinces were more affected by eight-year long Iran-Iraq war, immigration of refuges from neighbours countries and drought.

Dielectric properties and effect of electrical aging on space charge accumulation in polyimide/TiO2 nanocomposite films

In situ polymerized polyimide/TiO2 (PI/TiO2) nanocomposite films with good electrical aging resistance are studied. Space charge distribution in the PI/TiO2 nanocomposite films are measured using the pulsed electroacoustic method. Dielectric properties of the films are measured in the frequency range of 102 Hz–106 Hz by an impedance analyzer (Agilent 4294A) at room temperature. These nanocomposite films are also characterized by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). It is demonstrated that the nano-TiO2 particles strongly affect dielectric breakdown, lifetime and space charge distribution, and increase the voltage endurance of the nanocomposite films significantly. SEM analyses show that the nanocomposite films are destroyed after corona aging. The relation of space charge distribution with the concentration of the nano-TiO2 particles and the aging time is explored. Results show that an increase in dielectric permittivity of the nanocomposite films is observed with increasing filler concentration. However, the accumulation of space charge decreases with increasing nano-TiO2 particles concentration for the same corona aging time, and depends on the dielectric permittivity of the nanocomposite films.

Prediction and Modeling of Thin Gate Oxide Breakdown Subject to Arbitrary Transient Stresses

A reliable dielectric breakdown model under transient stresses via an extension of the power law is demonstrated. The model, which is based on the percolation model and the assumption of no significant detrapping, is successfully used in ramped voltage stress breakdown analysis. A demonstration of the model's validity consists of applying repetitive time-variant voltage waveforms—pulses, sine waves, ramps, and noise—until breakdown and, consequently, comparing prediction to reality. The breakdown distribution is initially derived from DC measurements, with the model predicting both the center and the shape of the distribution.

Statistical Analysis of Lifetime Distribution of Time-Dependent Dielectric Breakdown in Cu/Low-k Interconnects by Incorporation of Overlay Error Model

We propose a method for the statistical analysis of a via-to-line time-dependent dielectric breakdown (TDDB) test under misalignment impacts. The √E and overlay error models are incorporated into the lifetime distribution analysis in the framework of the Weibull regression model. The doubly truncated normal distribution effectively describes the space-decrease distribution that is estimated using the overlay error model. Incorporating these physical and statistical characteristics into the lifetime distribution analysis yields more reliable distribution parameters and helps to distinguish outliers as early failures with rejection of misalignment impacts.

Filamentary model of dielectric breakdown

A dielectric breakdown model based on the phenomenological description of the nucleation and growth of filaments is proposed. This description involves different characteristic times according to the interfacial or bulk nature of the growth processes. The resulting time to breakdown distribution presents Weibull or bimodal shape according to the relative values of those characteristic times. In particular, the variation in the Weibull slope with thickness is observable when the interfacial process characteristic time is the larger. Bimodal shapes are observable when the characteristics times are in the same range and the surface scaling of the distributions influences the apparent Weibull slopes. The model is compared to experimental constant voltage stress and linear ramp voltage stress measurements made on metal insulator metal and metal oxide semiconductors structures. The physical parameters extracted are discussed. Breakdown electric fields are derived as functions of temperature, dielectric thickness, and dielectric permittivity consistently with experimental trends. The electric field acceleration factors are also derived and depend on dielectric thickness.

Study of dielectric breakdown distributions in magnetic tunneling junction with MgO barrier

The breakdown distribution of a magnetic tunnel junction (MTJ) with an ultrathin (∼1.2 nm) MgO barrier was studied, and two distinct distributions were identified. The breakdown distribution with high value demonstrates a wide peak-to-peak separation (∼13.4σ) to the critical spin torque induced switching voltage. However, the peak-to-peak separation is only ∼8.4σ for the devices showing low breakdown value. Both abrupt and gradual breakdown events were observed in two distributions. The dependence of the percentage of low breakdown devices as a function of bias polarity, test and stress conditions, MTJ film properties, and process conditions was investigated. The low breakdown percentage can be significantly reduced by increasing the RA value and MTJ process optimization.

Time-Dependent Dielectric Breakdown of <formula formulatype="inline"><tex Notation="TeX">$\hbox{La}_{2} \hbox{O}_{3}$</tex></formula>-Doped High-<formula formulatype="inline"><tex Notation="TeX">$k$</tex></formula>/Metal Gate Stacked NMOSFETs

Time-dependent dielectric breakdown (TDDB) characteristics of La2O3-doped high-k dielectric in Hf-based high-k/TaN metal gate stack were studied. Unlike the abrupt breakdown in the conventional SiO2 , dielectric breakdown behaviors of La-incorporated HfON and HfSiON dielectrics show progressive breakdown characteristics. Moreover, the extracted Weibull slope beta of breakdown distribution is in the range of 0.87-1.19, and it is independent on capacitor areas and stress conditions. Moreover, field dependence of TBD and stress-induced leakage current strongly suggest that the E-model is more applicable to explain in TDDB of La-incorporated high-k dielectric in Hf-based high-k/metal gate stack structure.

Effect of microwave frequency on breakdown and electron energy distribution function using a global model

Global models (GMs) have proven a key modeling tool for the plasma processing field due to simplicity and speed. However, a GM requires specification of the electron energy distribution function (EEDF). The assumption of a Maxwellian EEDF leads to inaccurate reaction rate coefficients and results in error in plasma parameter prediction in high power microwave (HPM) driven discharges. Recently, a GM was developed with a pressure-independent enhanced EEDF to improve fidelity for modeling HPM breakdown. In this work, the GM is extended to 2 decades in frequency, and the frequency effect on HPM breakdown and the EEDF is investigated.

Variability in the scale properties of high‐resolution precipitation data in the Alpine climate of Switzerland

We explore the variability of scale‐related point precipitation properties on a large data set of high‐resolution 10‐min data from 62 stations across Switzerland. The focus is on the seasonal and spatial variability in basic scaling, correlation, and breakdown distribution parameters in the subdaily scaling range and their interdependency. Seasonal variability is found to be dominant. The summer season shows more structure in precipitation; a shorter autocorrelation range due to convective activity, high intermittency, and variance; and a multiscaling behavior in statistical moments. Winter events are longer, with smoother, less variable and strongly autocorrelated precipitation, and with a simple scaling behavior caused by larger‐scale frontal events. Some coherent regional differences are also apparent. The high Alpine region shows less variability and a stronger autocorrelation than other regions and a tendency toward simple scaling. The results also show that some scale‐related precipitation parameters are correlated and that snowfall has a discernible impact on high‐resolution properties such as smoothness and correlation. The results have an important practical significance for the extrapolation of parameters of scaling‐based precipitation models to ungauged sites.

Effects of Si3N4 Thickness on the Electrical Properties of Oxide-Nitride-Oxide Tunneling Dielectrics

tunnel barriers with a residual layer of different thicknesses were fabricated by thermally oxidizing film. According to leakage current measurements, the effective barrier height was significantly lowered because the middle layer has a lower bandgap than , which is beneficial in increasing the erasing/programming speed in flash memory devices. However, detrimental effects, such as the increased hysteresis in capacitance-voltage characteristics and the degraded breakdown distribution, were observed due to the significant amount of the charge trapping induced by the increased thickness. For the sample with a distinctive layer, trap-assisted tunneling and Fowler-Nordheim tunneling were the dominant conduction mechanisms at low and high electric field, respectively. However, the accumulation of N at the interface for the fully oxidized sample resulted in an asymmetric conduction mechanism behavior, which was explained by the band diagram analysis.