A Study of Nanometer Semiconductor Scaling Effects on Microelectronics Reliability

The desire to assess the reliability of emerging scaled microelectronics technologies through faster reliability trials and more accurate acceleration models is the precursor for further research and experimentation in this relevant field. The effect of semiconductor scaling on microelectronics product reliability is an important aspect to the high reliability application user. From the perspective of a customer or user, who in many cases must deal with very limited, if any, manufacturer's reliability data to assess the product for a highly-reliable application, product-level testing is critical in the characterization and reliability assessment of advanced nanometer semiconductor scaling effects on microelectronics reliability. This dissertation provides a methodology on how to accomplish this and provides techniques for deriving the expected product-level reliability on commercial memory products. Competing mechanism theory and the multiple failure mechanism model are applied to two separate experiments; scaled SRAM and SDRAM products. Accelerated stress testing at multiple conditions is applied at the product level of several scaled memory products to assess the performance degradation and product reliability. Acceleration models are derived for each case. For several scaled SDRAM products, retention time degradation is studied and two distinct soft error populations are observed with each technology generation: early breakdown, characterized by randomly distributed weak bits with Weibull slope Beta=1, and a main population breakdown with an increasing failure rate. Retention time soft error rates are calculated and a multiple failure mechanism acceleration model with parameters is derived for each technology. Defect densities are calculated and reflect a decreasing trend in the percentage of random defective bits for each successive product generation. A normalized soft error failure rate of the memory data retention time in FIT/Gb and FIT/cm2 for several scaled SDRAM generations is presented revealing a power relationship. General models describing the soft error rates across scaled product generations are presented. The analysis methodology may be applied to other scaled microelectronic products and key parameters

Large-Area Multi-Breakdown Characterization of Polymer Films: A New Approach for Establishing Structure–Processing–Breakdown Relationships in Capacitor Dielectrics

The ever-growing need for high-energy density and high operation temperature capacitive energy storage for next-generation applications has necessitated research and development on new dielectric materials for film capacitors. Consequently, various new approaches offering unique ways to tailor dielectric properties of polymers have recently emerged, and new materials such as dielectric polymer nanocomposites (PNC) are envisioned as potential next-generation dielectrics. Establishment of optimized formulation and processing conventions is however necessary in order to achieve improvement in dielectric breakdown properties. Importantly however, such material development puts dielectric breakdown strength assessment of polymer films in a central role in guiding material development process towards highly optimized functional materials. This is not a trivial task though, as the current state-of-the-art breakdown strength measurement techniques rarely provide statistically sufficient amounts of breakdown data from the application point-of-view, thus leading to impaired evaluation of the practical breakdown performance in film capacitors.In this thesis, a new large-area multi-breakdown measurement method enabling detailed dielectric breakdown characterization of polymer films is developed and evaluated. Various aspects encompassing sample film preparation, measurement procedure, breakdown progression, discharge event characterization, breakdown field determination, data validation and statistical analysis are systematically and critically discussed. A data qualification process based on the self-healing discharge energy and breakdown voltage characteristics is developed and shown to be a sensible and convenient way to exclude non-breakdown events from the measurement data prior to Weibull statistical analysis. The measurement method is shown to enable high-statistical-accuracy breakdown characterization of both metallized and non-metallized polymer films of different nature, including laboratory-scale, pilot-scale and commercial-grade capacitor films. Statistical aspects on the area dependence are discussed and the problematic nature of Weibull area-extrapolation of small-area breakdown data to represent larger film areas is exemplified. The fundamental differences between the large-area multi-breakdown and the small-area single-breakdown measurement methods and the statistical aspects thereof are analyzed in more detail by the Monte Carlo simulation method.The large-area multi-breakdown method is utilized to carry out a comprehensive analysis on structure--processing--breakdown relationships in conventional polymer and polymer nanocomposite films. Analysis on the effects of film processing, structure and morphology on the large-area multi-breakdown response of cast- and bi-axially oriented isotactic polypropylene (PP) films emphasizes the determining effect of processing-dependent film morphology in large-area dielectric breakdown response of PP films. Commercial capacitor-grade bi-axially oriented polypropylene (BOPP) films are shown to exhibit differences in breakdown distribution structure and weak point behavior in comparison to the laboratory-scale BOPP films, presumably due to differences in raw material, additives, thermal history and processing. Breakdown characterization of commercial metallized polymer films as a function of inter-layer pressure also emphasizes the importance of careful breakdown characterization under authentic operation stresses in order to ensure proper design and operation in practical applications.BOPP-based polymer nanocomposite (PNC) films are studied with a particular emphasis on the effects of various compositional, structural and film processing factors on the breakdown behavior of laboratory- and pilot-scale melt-compounded BOPP nanocomposite films incorporating silica and/or calcium carbonate nanofillers. The optimum nano-filler content is found to reside at the low fill-fraction range (~1 wt-%), however, the fill-fraction itself is not the only determining factor, as compounds with equal nanoparticle content but with differences in e.g. compounder screw speed are found to exhibit large differences in breakdown response. Indications of possible silica-antioxidant interaction are also reported. Structural imaging of the films shows that nano-structural features cannot solely explain the observed large-area breakdown behavior – this aspect points towards large-area approach being necessary for the imaging techniques as well in order to reliably establish a link between structural properties and engineering breakdown strength. The results point out that up-scaling of PNC production is sensible with conventional melt-blending technology, although further development and optimization of nanocomposite formulations and processing are seen as necessary. Analysis on the ramp-rate-dependence of the breakdown response in dielectric polymer nanocomposite films also provides perspective on the importance of careful breakdown assessment when dielectric films of more complex internal structure are studied

DEEP SUBMICRON CMOS VLSI CIRCUIT RELIABILITY MODELING, SIMULATION AND DESIGN

CMOS VLSI circuit reliability modeling and simulation have attracted intense research interest in the last two decades, and as a result almost all IC Design For Reliability (DFR) tools now try to incrementally simulate device wearout mechanisms in iterative ways. These DFR tools are capable of accurately characterizing the device wearout process and predicting its impact on circuit performance. Nevertheless, excessive simulation time and tedious parameter testing process often limit popularity of these tools in product design and fabrication. This work develops a new SPICE reliability simulation method that shifts the focus of reliability analysis from device wearout to circuit functionality. A set of accelerated lifetime models and failure equivalent circuit models are proposed for the most common MOSFET intrinsic wearout mechanisms, including Hot Carrier Injection (HCI), Time Dependent Dielectric Breakdown (TDDB), and Negative Bias Temperature Instability (NBTI). The accelerated lifetime models help to identify the most degraded transistors in a circuit in terms of the device's terminal voltage and current waveforms. Then corresponding failure equivalent circuit models are incorporated into the circuit to substitute these identified transistors. Finally, SPICE simulation is performed again to check circuit functionality and analyze the impact of device wearout on circuit operation. Device wearout effects are lumped into a very limited number of failure equivalent circuit model parameters, and circuit performance degradation and functionality are determined by the magnitude of these parameters. In this new method, it is unnecessary to perform a large number of small-step SPICE simulation iterations. Therefore, simulation time is obviously shortened in comparison to other tools. In addition, a reduced set of failure equivalent circuit model parameters, rather than a large number of device SPICE model parameters, need to be accurately characterized at each interim wearout process. Thus device testing and parameter extraction work are also significantly simplified. These advantages will allow circuit designers to perform quick and efficient circuit reliability analyses and to develop practical guidelines for reliable electronic designs

Steering Capacitor Film Development with Methods for Correct and Adequate Dielectric Performance Assessment

The transition of electric power systems towards renewable generation has created an increasing market for power electronics using film capacitors as one of their key components. Size, weight, and cost reduction can be achieved with better capacitors – an objective achievable with advanced dielectric films. The current state-of-the-art biaxially oriented polypropylene (BOPP) films are already operated close to their fundamental limits, causing a growing demand for next-generation technologies. To perform well when used in a capacitor, a film needs to have a wide range of fundamental and applied properties, all of which should be evaluated during film development to ensure there are no unwanted trade-offs. Power capacitors are used in applications with high downtime costs, e.g. HVDC, thus especially the reliability aspects must be given scrutiny. This thesis work was inspired by the lack of knowledge of the long-term performance of next generation dielectrics, e.g. polymer nanocomposites. Equally important was to fill the gaps in published knowledge of measurement methods to evaluate long-term properties, voltage endurance, and surprisingly, also the dielectric permittivity of thin (≈10 μm) low-loss films. In this thesis, a suitable measurement for each three is presented along with examples of their capability and an approach to applying them to steer film development. The large-area multi-breakdown method developed in our research group is extended to measurements at realistic operating temperatures, and industrial BOPP films are shown to exhibit an 11–20 % decrease in the DC breakdown strength between room temperature and 100 ◦C. The results align with literature, which supports the validity of the approach. BOPP films made of base materials varying in terms of molecular weight are measured: these films exhibit similar short-term breakdown performance at room temperature, yet at 100 ◦C differences emerge. The difference did not correlate with the reduction of breakdown performance after DC electro-thermal aging, demonstrating the necessity of long-term tests. Electron beam evaporation in high vacuum (P<10−6 mbar) is established as a repeatable and suitable method to metallize electrodes on ultra low-loss BOPP films, solving earlier issues of abnormally high dielectric losses or unrealistically low real permittivity. Metallization process is identified as the crucial factor: no pre- or post-treatments are required, and valid results are obtainable with various electrode metals. The method was demonstrated by measuring true “literature value” dielectric permittivity of commercial BOPP films: E≈2.25 and tanδ≈10−4. The importance of successful metallization process for measuring the intrinsic losses is demonstrated: samples with sputter deposited electrodes exhibited abnormally high dielectric losses, as also did samples metallized using another e-beam evaporator. The multi-breakdown approach is also extended to times-to-breakdown tests, and accelerated ageing tests are conducted on an industrial BOPP film. High-field degradation and drastically reduced insulation life are observed. Analysis of the Weibull failure rate supports the notion that at current design stresses, BOPP is already operated close to the fundamental material limits, and also that the life in operating conditions cannot be determined by simple inverse power law extrapolation of accelerated rapid ageing data. Again, long-term ageing testing is advocated. Space charge measurements on “classic” BOPP films reveal charge accumulation at high fields, as expected. Interestingly, no space charge accumulation is detected in a novel nanostructured material under similar conditions, demonstrating the potentiality of nanofilled DC insulation. A DC electro-thermal ageing test method is presented to investigate long-term phenomena in realistic operating conditions. Two 1000 h DC electro-thermal ageing tests associate ageing with the formation of electrically weak points. Large-area breakdown behavior, being sensitive to local changes, is established as a recommended ageing indicator. Material characterization does not reveal ageing-induced changes in bulk properties, supporting the literature-backed conclusion that early ageing progresses by localized degradation. A trial with eight pilot-scale materials demonstrate that weak point formation may be inhibited in nanostructured materials, but also that material-specific optimization of film processing is required to reach optimal dielectric performance. Ultimately, the methods developed are fused into one resource-efficient approach to capacitor film development, in which the short-, mid-, and long-term properties are evaluated in three overlapping phases. Reliance on individual performance metrics to steer film development is discouraged: all properties need to be at an appropriate level for a film to perform in application, and there are trade-offs to be managed

Methods for modeling degradation of electrical engineering components for lifetime prognosis

Reliability of electrical components is an issue studied to improve the quality of products, and to plan maintenance in case of failure. Reliability is measured by studying the causes of failure and the mean time to failure. One of the methods applied in this field is the study of component aging, because failure often occurs after degradation. The objective of this thesis is to model the degradation of components in electrical engineering, in order to estimate their lifetime. More specifically, this thesis will study large area organic white light sources (OLEDs). These sources offer several advantages in the world of lighting thanks to their thinness, their low energy consumption and their ability to adapt to a wide range of applications. The second components studied are electrical insulators applied to pairs of twisted copper wires, which are commonly used in low voltage electrical machines. First, the degradation and failure mechanisms of the various electrical components, including OLEDs and insulators, are studied. This is done to identify the operational stresses for including them in the aging model. After identifying the main causes of aging, general physical models are studied to quantify the effects of operational stresses. Empirical models are also presented when the physics of degradation is unknown or difficult to model. Next, methods for estimating the parameters of these models are presented, such as multilinear and nonlinear regression, as well as stochastic methods. Other methods based on artificial intelli­gence and online diagnosis are also presented, but they will not be studied in this thesis. These methods are applied to degradation data of organic LEDs and twisted pair insulators. For this purpose, accelerated and multifactor aging test benches are designed based on factorial experimental designs and response surface methods, in order to optimize the cost of the experiments. Then, a measurement protocol is described, in order to optimize the inspection time and to collect periodic data. Finally, estimation methods tackle unconstrained deterministic degradation models based on the measured data. The best empirical model of the degradation trajectory is then chosen based on model selection criteria. In a second step, the parameters of the degradation trajectories are modeled based on operational constraints. The parameters of the aging factors and their interactions are estimated by multilinear regression and according to different learning sets. The significance of the parameters is evaluated by statistical methods if possible. Finally, the lifetime of the experiments in the validation sets is predicted based on the parameters estimated by the different learning sets. The training set with the best lifetime prediction rate is considered the best

Bibliography of Lewis Research Center technical publications announced in 1992

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1992. All the publications were announced in the 1992 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Bibliography of Lewis Research Center technical publications announced in 1993

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1993. All the publications were announced in the 1993 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Publications of the Jet Propulsion Laboratory, 1979

This bibliography includes 1004 technical reports, released during calendar year 1979, that resulted from scientific and engineering work performed, or managed, by the Jet Propulsion Laboratory. Three classes of publications are included: (1) JPL Publications; (2) articles published in the open literature; and (3) articles from the bimonthly Deep Space Network Progress Report. The publications are indexed by: (1) author, (2) subject, and (3) publication type and number. A descriptive entry appears under the name of each author of each publication; an abstract is included with the entry for the primary (first listed) author. Unless designated otherwise, all publications listed are unclassified

Cumulative index to NASA Tech Briefs, 1970-1975

Tech briefs of technology derived from the research and development activities of the National Aeronautics and Space Administration are presented. Abstracts and indexes of subject, personal author, originating center, and tech brief number for the 1970-1975 tech briefs are presented