Breakdown Voltage Distribution Research Articles

Low- k film damage-resistant CO chemistry-based ash process for low- k/Cu interconnection in flash memory devices

In this paper, CO chemistry-based ash processes have been suggested to reduce carbon depletion and moisture absorption from plasma discharges for low- k/Cu interconnection in 40 nm-node Flash memory. We analyzed ash processes utilizing Fourier transform infrared spectroscopy (FTIR), k-value measurements, and sidewall-shrinking profile measurements based on a cross-sectional scanning electron microscope (SEM) image obtained before and after filling trench with Cu. In an effort to better understand the role of ash processes in ultra-narrow capacitors, we also evaluated the distribution of breakdown voltages as a function of voltage for trench-patterned wafers. In this paper, we successfully found that low-damage ash processes for low- k/Cu interconnection by adopting CO chemistry-based ash process.

Statistical analysis of the AC breakdown voltages of ester based transformer oils

Recent decades have seen the rapid and successful deployment of ester oils as transformer dielectrics. When evaluating the compatibility of ester oils with existing transformer insulation designs, it is essential to not only compare the mean breakdown voltages of the oils, but also to consider the role of dispersion and thus the withstand voltage levels (with the acceptable breakdown likelihood). Insulation designers sometimes estimate the withstand voltage of mineral oil from the dispersion of the data, assuming that the breakdown voltages of the oil follow a parametric distribution. However, there is a lack of discussion as to whether this method would be suitable for estimating the withstand voltages of ester oils. This paper uses samples of breakdown voltages of a synthetic ester, a natural ester and a mineral oil to analyze their distributions, and discusses the applicability of using Weibull and Gaussian distributions to estimate the withstand voltages of the esters. It is found that the distributions of ester breakdown voltages, in particular the lowest breakdown voltage, are similar to those of mineral oil. Consequently there is evidence that from the ac withstand voltage point of view the tested esters are compatible for the use in power transformers.

Maximum likelihood estimation in the 3-parameter weibull distribution: a look through the generalized extreme-value distribution

The main contribution of this paper is to provide reasonable confidence intervals for maximum likelihood estimates of percentile points in dielectric breakdown voltage probability distributions. The Weibull distributions which include threshold values are often used in breakdown voltage distributions. In some breakdown voltage samples, there exist cases in which the maximum likelihood estimates of all the three Weibull parameters diverge; these cases, in limiting forms, correspond to Gumbel distributions. However, computing confidence intervals of the percentile point estimates using the observed information matrix might be impossible when the distribution models are assumed to be the Weibull type. For such cases, adoption of the generalized extreme-value distribution as an extension of the Weibull distribution allows us to assess this troublesome problem. A Monte Carlo simulation using the newly developed generalized extreme-value distribution parameter estimation code reveals the property of the percentile point estimates for extreme-value type distributions, when the Weibull shape parameter is large. Biases and root mean squared errors of percentile point estimates are investigated both for the maximum likelihood estimates and for some closed form estimates; maximum likelihood estimates provide reasonable confidence intervals. For convenience, a demonstrative example with an estimation algorithm is provided.

A 1 cm/spl times/1 cm In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 1 cm/spl times/1 cm array of 100 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APD). The average breakdown voltage was 28.7 V with a standard deviation of less than 0.5 V. The distribution of breakdown voltage across the area followed a radial pattern consistent with a slight epitaxial growth nonuniformity. The mean dark current at a gain of 10, or 6.1 A/W, was 10.3 nA, and none of the 100 APDs had a dark current of more than 25 nA. The bandwidth at a gain of 10 was 6.2 GHz, and the maximum gain-bandwidth product was 140 GHz. This technology is ideally suited for next-generation three-dimensional imaging applications.

Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages

AbstractStatistically based measurements of breakdown voltages U b and breakdown delay times td and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages U b for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s –1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients α , γ and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y 0 (τ ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas‐phase model. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Study of transient processes in nitrogen by measurements of dynamic breakdown voltages

In this paper the measurements of the dynamic breakdown voltages U b for linearly rising pulses in nitrogen at low pressure are presented. The measurements were carried out for the rates of voltage rise k up to $300\, {\rm V\,s}^{-1}$ . Dependence of the breakdown voltages, delay times and electron yields on the rate of rise were obtained experimentally and theoretically under different conditions. It was found that the overvoltage $\overline {\Delta U_b}$ and the mean effective electron yield $\overline {YP}$ is proportional to $\sqrt k$ ( Y is a number of generated electrons in the interelectrode space per second and P the breakdown probability), while the statistical time delay $\overline t_s$ is proportional to $1/\sqrt k$ . In the second part, the experimental breakdown voltage distributions were obtained, fitted by theoretical distributions and some breakdown parameters relevant to experimental conditions were determined. Based on the approximate analytical and numerical models, the dependence of the effective secondary electron yield γ on the overvoltage and on the rate of voltage rise were derived from these measurements. It was found that γ varies linearly with the overvoltage for a constant k , and the slope of γ is proportional to $\sqrt k$ .

Characterization of Three-Dimensional Capacitor Prepared by Oxide Recess in Shallow Trench Isolation

In this paper, we present a new process flow to increase cell capacitance in planar dynamic random access memory cells designed for system-on-chip applications. Silicon dioxide of shallow trench isolation (STI) under capacitor electrodes is recessed to increase cell capacitance. It appears that the cell capacitance is increased to 25% when the STI recess is 0.15 μm. The recession slightly decreases junction leakage current due to annealing of defects and also relief of STI stress. These combined effects increase refresh time about 50% in 1 Mb memory array. The distribution of breakdown voltage in capacitor oxide shows similar behavior compared with samples without STI recessed. Also, the lifetime of the capacitor oxide evaluated from the Weibull method exceeds 2000 years. © 2004 The Electrochemical Society. All rights reserved.

Thickness dependence of Weibull slopes of HfO2 gate dielectrics

Breakdown voltage distribution, Weibull slopes, and area scaling factors have been investigated for HfO/sub 2/ gate dielectrics in order to gain a better understanding of the breakdown mechanism. Weibull slope of thick HfO/sub 2/ (e.g., /spl beta//spl ap/4 for EOT=2.5 nm) is smaller than that of SiO/sub 2/ with similar physical thickness, whereas /spl beta/ of the thinner HfO/sub 2/ (e.g., /spl beta//spl ap/2 for EOT=1.4 nm) is similar to that of SiO/sub 2/. The implication of the thickness dependence of /spl beta/ is discussed.

A High-Voltage Switching Device Based on Two High-Current Vacuum Gaps Connected in Series

A high-voltage switch that consists of two РВУ-43 triggered vacuum spark gaps connected in series has been manufactured and tested. The switch is intended for use at a voltage of up to 80 kV. The maximum current switched is 200 kA. The breakdown strength of the switch has been theoretically and experimentally investigated. Experimental and theoretical breakdown-voltage distribution functions have been obtained for the gaps and the switch. Based on the empirical breakdown-voltage distributions for both of the gaps, the breakdown-voltage distribution for the switch has been calculated and found to be in satisfactory agreement with the measurement results.

Statistical Analysis of the Breakdown Voltage in Ne at 1 mbar Pressure

The results of the electrical breakdown investigation in neon at Paschen's minimum, using a dynamic method with applying surface law are presented in this paper. The investigations were performed for applied voltage increase rates from 0.1 to 300 V/s. Two hundred measurements were done for each of applied voltage increase rates, while the number of measurements was 1000 for establishing the breakdown voltage distributions. Using the Mann-Whitney's test it was shown that the results appear randomly without any systematic error. A new form of breakdown voltage density distribution is suggested. Some of the V-t characteristics are given and the validity of the surface law is confirmed for the low pressure gas breakdown.

Breakdown-voltage memory effect in a neon-filled diode at 1 mbar

Results of the investigation of the breakdown-voltage distribution dependence on the relaxation time of the diode [the curve U~/sub b~/=f(/spl tau/)], i.e., memory effect, in neon at p=1 mbar are presented in this paper. The memory effect is determined for the diode-relaxation times 0.1-100 s. The applied voltage was linearly increased with the increasing rate 10 V/s. For each value of the relaxation time, the series of 200 successive and independent measurements were done. The numerical fitting of the theoretical expression of the breakdown-voltage distribution on the histograms of the experimentally established data was used to determined relative yield in the diode for the different relaxation times Y/Y/sub 0/=f(/spl tau/). Results show that the yield in the diode decreased in that time interval in one order of magnitude. Quantitative parameters for two-step decreasing and qualitative explanation of these dependencies are given.

A new approach to the optimaldesign of multiple field-limiting ring structures

In this paper, a computer-based analysis is performedto study layout solutions aimed at increasing the breakdownvoltage in Si-microstrip detectors. For optimum performance itis crucial to achieve maximum breakdown voltage for Sidetectors operating at very high bias due to the extremely hostileradiation environment of next generation experiments such asLHC. The performance of Si-microstrip detectors can be improved by implementing floating field-limiting rings around theactive detector area. A simulation study has been carried outto evaluate the distribution of breakdown voltage as a functionof guard-ring spacing (GS). The purpose of this work is to finda criterion to optimize GS for multiplering structures incorporating various physical and geometrical parameters as an aid to design optimization. Using thiscriterion the optimum spacing of guard rings for multiple ringstructures was obtained. The proposed criterion is very robustand is insensitive to the number of guard rings, junction depthand radiation damage. The simulation results for the seven-ringdesign agree well with experimental measurements.

Characteristics of n+ polycrystalline-Si/Al2O3/Si metal–oxide– semiconductor structures prepared by atomic layer chemical vapor deposition using Al(CH3)3 and H2O vapor

We report interface and dielectric reliability characteristics of n+ polycrystalline-silicon (poly-Si)/Al2O3/Si metal–oxide–semiconductor (MOS) capacitors. Al2O3 films were prepared by atomic layer chemical vapor deposition using Al(CH3)3 and H2O vapor. Interface state density (Dit) and dielectric reliability properties of n+ poly-Si/Al2O3/Si MOS structures were examined by capacitance–voltage, conductance, current–voltage, and time-dependent dielectric breakdown measurements. The Dit of the n+ poly-Si/Al2O3/Si MOS system near the Si midgap is approximately 8×1010 eV−1 cm−2 as determined by the conductance method. Frequency dispersion as small as ∼20 mV and hysteresis of ∼15 mV were attained under the electric field of ±8 MV/cm. The gate leakage current of ∼36 Å effective thickness Al2O3 dielectric measured at the gate voltage of −2.5 V is ∼−5 nA/cm2, which is approximately three orders of magnitude lower than that of a controlled oxide (SiO2). Time-dependent dielectric breakdown data of Al2O3/Si MOS capacitors under the constant current/voltage stress reveal excellent charge-to-breakdown characteristics over controlled oxide. Reliable gate oxide integrity of Al2O3 gate dielectric is manifested by the excellent distribution of gate oxide breakdown voltage on 128 million MOS capacitors having isolation edges. Extracted time constant and capture cross section of the Al2O3/Si junction are discussed.

Application of Weibull distribution analysis to the dielectric failure of multilayer ceramic capacitors

The Weibull distribution has been previously applied to the mechanical and dielectric failures of ceramics. In this paper, it is confirmed by experiment that this data treatment method is also valid for application in the dielectric failure of multilayer ceramic capacitors (MLCs) which have undergone screening. The Weibull modulus is found to be a useful parameter indicating the sharpness of the distribution of breakdown voltages and mechanical strength of MLCs. By Weibull analysis, the lately developed relaxor-based MLCs are found to compare favorably with traditional barium-titanate-based MLCs, implying that relaxor MLCs are more attractive than generally realised.

Effects of nitrogen incorporation during growth on thin oxide wearout and breakdown

Thin oxides, 6.4–7.6 nm thick, have been formed in oxygen with varying levels of nitrogen incorporated into the oxidation ambient. In addition to films with no nitrogen, the nitrogen concentration was varied from 0.00001 to 10% in decade increments. The wearout and breakdown characteristics of these oxides were measured. Wearout was quantified by measuring the changes in the low-level leakage currents, the changes in the mid-gap interface trap densities, the shifts in the flat-band voltages, and the number of traps generated inside of the oxides, all by high voltage stresses. Breakdown was characterized by measuring the time-zero-breakdown voltage distributions. It was found that the wearout was independent of the nitrogen concentration but the breakdown voltages decreased as the nitrogen concentration increased. The average breakdown voltage dropped by |1 V| for oxides with 0.1% N 2 and by |3 V| for oxides with 10% N 2, with the number of low-voltage breakdowns also increasing as the nitrogen concentration increased. It was felt that the nitrogen was incorporated into the oxide both relatively uniformly throughout the oxide and in local non-uniform regions. The uniform distribution inside of the oxide did not affect the wearout properties of the oxide, which were determined by high-field, bond breaking of silicon-oxygen bonds. The regions with non-uniform concentrations of nitrogen introduced local asperities that affected the breakdown voltage distributions by generating local high field regions and locally high trap concentrations.

Gate oxide degradation during polysilicon etching in a parallel-plate plasma-type etcher

Gate oxide degradation by transient surge current has been tested during polysilicon etching in a parallel‐plate plasma‐type etcher. To reduce the transient surge current, rf power is removed gradually at a rate of 50 W/s after 50% overetch. Breakdown voltage distribution measured at a metal–oxide–semiconductor capacitor array structure with gate edges is improved considerably by the ramping down of rf power. This clearly indicates that the transient surge current can cause charge damage to some extent even in a plasma‐type etcher. Gate oxide recovery during the interpolyoxide deposition is also discussed.

Modeling oxide thickness dependence of charging damage by plasma processing

Develops a quantitative model for thin oxide plasma charging damage by examining the oxide thickness dependence of charging current. The current is deduced from capacitance-voltage (CV) curves of metal-oxide-semiconductor (MOS) capacitors after plasma etch. The model predicts the oxide thickness dependence of plasma charging successfully. It is shown that plasma acting on a very thin oxide during processing may be modeled as essentially a current source. Thus the damage will not be greatly exacerbated as oxide thickness is further reduced in the future. Gate oxide breakdown voltage distribution of MOS capacitors after plasma processing can be predicted accurately from that of a control wafer by using a defect-induced breakdown model.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Monitoring plasma-process induced damage in thin oxide

Plasma etching and resist ashing processes cause current to flow through the thin oxide and the resultant plasma-induced damage can be simulated and modeled as damage produced by constant current electrical stress. The oxide charging current produced by plasma processing increases with the 'antenna' size of the device structure. Oxide charge measurement such as CV or threshold voltage is a more sensitive technique for characterizing plasma-processing induced damage than oxide breakdown. The oxide charging current is collected only through the aluminum surfaces not covered by the photoresist during plasma processes. Although forming gas anneal can passivate the traps generated during plasma etching, subsequent Fowler-Nordheim stressing causes more traps to be generated in these devices than in devices that have not been through plasma etching. Using the measured charging current, the breakdown voltage distribution of oxides after plasma processes can be predicted accurately. Oxide shorts density of a single large test capacitor is found to be higher than that in a multiple of separated small capacitors having the same total oxide area. This would lead to overly pessimistic oxide defect data unless care is taken.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Scanning Force/Tunneling Microscopy as a Novel Technique for the Study of Nanometer-Scale Dielectric Breakdown of Silicon Oxide Layer

Scanning force/tunneling microscopy (AFM/STM) was proposed as a novel technique to investigate local dielectric breakdown voltage for the silicon oxide layer. It was manifested that this novel technique could simultaneously measure surface topography and distribution of dielectric breakdown voltage with nanometer-scale resolution. We confirmed that the dielectric breakdown voltage measured with the AFM/STM increased monotonously with the increase in oxide thickness. In addition to the above results, we observed that the oxide layer with visible defect had a lower dielectric breakdown voltage.

A proportional hazards approach to correlate SiO 2—breakdown voltage and time distributions : C. K. Chan. IEEE Trans. Reliab.39(2), 147 (1990)

A proportional hazards approach to correlate SiO 2—breakdown voltage and time distributions : C. K. Chan. IEEE Trans. Reliab.39(2), 147 (1990)