This thesis presents the results of research into the performance of advanced polymer dielectrics for the realization of high-power electronic circuits in a miniature form. These polymeric materials must satisfy a number of critical thermal, environmental, and electrical requirements to meet the required performance criteria for microelectronics applications. These desired attributes include thermal stability, low moisture uptake, high breakdown voltage (low leakage current), low dielectric constant, low loss tangent, high glass transition temperature, and low surface roughness. The use of these polymers allows for advanced electronic packaging techniques, resulting in improved system performance and reliability. Research was performed using a commercially available polymer dielectric and evaluated the feasibility of utilizing these materials as interlayer dielectrics in multilayer power electronic circuits. Historically, efforts to develop advanced interlayer dielectric materials have concentrated on promoting their use in high speed digital circuits. However, dielectrics used in power electronics must meet requirements not commonly stressed in designs for digital circuits. Multilayer circuits used in power electronics place a particular emphasis on the material properties of high dielectric strength or breakdown voltage and small values for loss tangent or dissipation factor. The focus of this research has been to characterize these particular properties for a commercially available polymer dielectric. / Master of Science

Lui Man Leung. / "May 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 197-200).

The aim of this work was to contribute to a better understanding of the characteristics and applications of (Ba,Sr)Sm2Ti4O12 microwave dielectric ceramics. The major contents are as follows. Firstly, to establish the correct reaction sequence of (Ba,Sr)Sm2Ti4O12, phases present in different calcining temperatures are identified by X-ray diffraction patterns. When different calcining temperatures are used, the source materials BaO (BaCO3), TiO2 and Sm2O3 are consumed at different calcining temperatures; the intermediate phases BaTiO3, BaTi4O9, and Sm2Ti2O7 reveals and consume at different calcining temperatures before the BaSm2Ti4O12 phase starts to reveal. However, the real solid reaction processes are usually more complex, and some intermediate reaction processes might happen. Secondly, in the (Ba1-xSrx)Sm2Ti4O12 system, SrO can be used to substitute the BaO site and improve the microwave dielectric characteristics. In this study, we find that SrO content in the range of 2 ~ 6 mol% is the acceptable composition because of the higher Q*f values and acceptable and values. Thirdly, the CaO-BaO- Li2O-Sm2O3-TiO2(CBLST) ceramics system was studied. In general, a dielectric material with a high has a large . To adjust to close 0ppm/oC, two or more compounds having negative and positive values are employed to form a solid solution or mixed phases in order to obtain the desired dielectric properties. In this study, BaO was used to substitute the CaO site and improved the microwave dielectric characteristics. Finally, the (Ba0.98Sr0.02)Sm2Ti4O12 system was adopted as a case of applications in dielectric resonator antenna. It possessed a low value of -5.96ppm/¢XC, a high value of 79, and a high Q*f value of 7920 GHz (at 3.311GHz). With the loading of a (Ba0.98Sr0.02)Sm2Ti4O12 dielectric resonator (DR), a circular polarization (CP) design of DR antenna through a cross slot of unequal slot lengths in the ground plane of a microstrip line is fabricated. From the results obtained, it is also found that the present proposed CP design has relatively relaxed manufacturing tolerances, as compared to the conventional CP designs that require slight geometrical modifications of the microstrip patch or DR elements. With the loading of a (Ba0.98Sr0.02)Sm2Ti4O12 superstrate layer and a 1W chip resistor, a compact rectangular microstrip antenna with enhanced gain and wider bandwidth can be implemented. The antenna size is reduced to be ~ 6.05% times of a conventional patch antenna, the proposed structure can have an operating bandwidth of more than six times that of a conventional patch antenna, with an almost equal antenna gain level.

Microwave dielectric resonators (DRs) are being widely used in microwave telecommunication devices owing to their excellent characteristics of suitable dielectric constant, good temperature stability, and low dielectric loss. In this study, the crystalline phase and the microwave dielectric properties of the (1-x)Al2O3 - xTiO2 (x=0.08, 0.12, 0.16) compositions with 2wt%, 4wt%, 6wt%, and 8wt% MgO-CaO-Al2O3-SiO2 (MCAS) glass addition have been investigated. By combining the material Al2O3 with negative temperature coefficient of the resonant frequency (£nf = -55 ppm/¢J) and the material TiO2 with positive £nf value (£nf = +450 ppm/¢J), it is desired to produce the ceramics with £nf ~0 ppm/¢J. The MCAS is used as liquid-phase sintering aid to lower down the sintering temperature. In the MCAS-doped (1-x)Al2O3 - xTiO2 system, the Al2TiO5 phase starts to appear at about 1250¢J, and then the crystalline intensity of Al2TiO5 phase increases with the increase of sintering temperatures and MCAS glass content, until the temperatures that TiO2 is consumed. As the sintering temperature increases, the maximum dielectric constants and Q¡Ñf values can be obtained at 1250¢J, and the £nf values shift from positive to negative. The optimum £nf value of ¡V0.6 ppm/¢J exists in the 88mol%Al2O3 - 12mol%TiO2 composition with 2wt% MCAS addition and sintering temperature of 1300¢J. The MCAS content, TiO2 content, and sintering temperature will result in the variation of microwave dielectric properties. In this study, MCAS-doped (1-x)Al2O3 - xTiO2 system exhibits the microwave dielectric properties of¡G £`r=7~9.5, Q¡Ñf=6500~11000, and £nf = -60 to +40ppm/¢J. By adjusting the MCAS content, TiO2 content, and sintering temperatures, ceramics with good microwave properties can be obtained in the MCAS-doped (1-x)Al2O3 - xTiO2 system.

As integrated circuits (ICs) are scaled down to deep submicron regime, interconnect delay becomes increasingly dominant over intrinsic gate delay. To solve the issue, two realistic methods are accepted popularly. On the one hand we use copper as the conductor for multilevel interconnects to decrease the resistance part of the RC delay. On the other hand we should reduce the coupling capacitance between the metal lines and this requires a low dielectric constant material. However, some difficulties come up in integrating low-k material with copper wires, including dielectric integrity and high diffusivity of copper ions. In order to prevent copper from penetrating into dielectric material under high electric fields and operation temperature, barrier dielectric have been developed to enhance resistance against copper drift. Silicon carbide (SixCy) with lower dielectric constant (k=4~5) is a promising barrier dielectric material to replace typically used silicon nitride (SixNy), (k~8). In this thesis, we will discuss the basic material properties of silicon carbide and the issues which will meet in process integration and actual working such as thermal cycles and operating under an electric field and a high temperature environment simultaneously. We investigated the conduction mechanism of the leakage current and tried to extract the physical parameters among it. In addition, the electrical properties of Silicon carbide at low temperature were also an important part of our research. Finally, we proposed some reasonable models to demonstrate the phenomenon and results we observed.

As technologies continue advancing, semiconductor devices with dimensions in nanometers have entered all spheres of human life. This research deals with both the statistical aspect of reliability and some electrical aspect of reliability characterization. As an example of nano devices, TaO_x-based high k dielectric thin films are studied on the failure mode identification, accelerated life testing, lifetime projection, and failure rate estimation. Experiment and analysis on dielectric relaxation and transient current show that the relaxation current of high k dielectrics is distinctive to the trapping/detrapping current of SiO₂; high k films have a lower leakage current but a higher relaxation current than SiO₂. Based on the connection between polarization-relaxation and film integrity demonstrated in ramped voltage stress tests, a new method of breakdown detection is proposed. It monitors relaxation during the test, and uses the disappearing of relaxation current as the signal of a breakdown event. This research develops a Bayesian approach which is suitable to reliability estimation and prediction of current and future generations of nano devices. It combines the Weibull lifetime distribution with the empirical acceleration relationship, and put the model parameters into a hierarchical Bayesian structure. The value of the Bayesian approach lies in that it can fully utilize available information in modeling uncertainty and provide cogent prediction with limited resources in a reasonable period of time. Markov chain Monte Carlo simulation is used for posterior inference of the reliability projection and for sensitivity analysis over a variety of vague priors. Time-to-breakdown data collected in the accelerated life tests also are modeled with a bathtub failure rate curve. The decreasing failure rate is estimated with a non-parametric Bayesian approach, and the constant failure rate is estimated with a regular parametric Bayesian approach. This method can provide a fast and reliable estimation of failure rate for burn-in optimization when only a small sample of data is available.

With the rapidly progress in the microwave communication systems, miniaturization and performance enhancement have become two main requirements of the microwave devices. Microwave dielectric substrates would be the best choice for these requirements, because high dielectric constant of the substrates would reduce the size of the devices, high quality factor of the substrates would improve the microwave characteristics of the devices, and low temperature coefficient of resonant frequency would reduce the shift of the operating frequencies due to the variation of temperature. As mentioned above, the main research of this dissertation is divided into two parts: microwave dielectric materials and microwave filters. 1. Microwave dielectric materials AB2O6 (A=Mg, Zn; B=Ta, Nb) microwave dielectric ceramics have been developed as the microwave dielectric resonators (DRs) in the past, because the dielectric resonators fabricated by AB2O6 ceramics reveal the good microwave dielectric characteristics. However, the temperature coefficients of resonant frequency of MgTa2O6, MgNb2O6, ZnTa2O6, and ZnNb2O6 ceramics are still not good enough for the applications at the microwave frequency. In addition, MgTa2O6 and ZnTa2O6 ceramics reveal positive temperature coefficients of resonant frequency but the MgNb2O6 and ZnNb2O6 ceramics reveal negative temperature coefficients of resonant frequency. In this study, combining of MgNb2O6 ceramics (with negative temperature coefficients of resonant frequency) and MgTa2O6 ceramics (with positive temperature coefficients of resonant frequency) to form Mg(Ta1-xNbx)2O6 ceramics and combining of ZnNb2O6 ceramics (with negative temperature coefficients of resonant frequency) and ZnTa2O6 ceramics (with positive temperature coefficients of resonant frequency) to form Zn(Ta1-xNbx)2O6 ceramics, which all reveal near-zero temperature coefficients of resonant frequencyand are suitable for the applications of microwave communication devices. The sintering and microwave dielectric characteristics of the Mg(Ta1-xNbx)2O6 and Zn(Ta1-xNbx)2O6 dielectric ceramics are also investigated. 2. Wide-band, dual-band, tri-band, and tetra-band bandpass filters Microwave filters have been widely used in the communication systems. The optimal microwave dielectric characteristics of AB2O6 ceramics developed in this thesis were adopted as the substrates of the filters. The performance of the filters was improved obviously due to the high dielectric constant and high quality factor of the microwave dielectric ceramic substrates. At first, a wide-band and a dual-band (2.45/5.2 GHz) bandpass filters are developed by the combination technique of modified end-coupled microstrip lines and half-wavelength ombination technique will generate three transmission zeros easily in the stop-band to improve the characteristics of the filters. And the next, the tri-band (1.57/2.45/5.2 GHz) bandpass filters are developed by the combination of modified end-coupled microstrip lines, outer-frame structures and half-wavelength U-shaped hairpin resonators. The Defected Grounded Structures (DGS) are add into the ground planes of the tri-band bandpass filters to generate the fourth frequency (3.5 GHz), hence, the tetra-band (1.57/2.45/3.5/5.2 GHz) bandpass filters are accomplished. In addition, due to the uses of the high dielectric constant ceramic substrates and the combination techniques, the size of this tetra-band bandpass filter is only 26.3 mm*9.9 mm. Besides, six deeply transmission zeros are generated in the stop-band to improve the characteristics of the filters (1~7 GHz), all the characteristics of this tetra-band filters (frequency, bandwidth, insertion loss, and stop-band rejection) are suitable for the applications of modern communication systems.

Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Includes bibliographical references. Issued in print and online. Available via ProQuest Digital Dissertations.

Electromagnetic heating (EMH) processes are being increasingly used in the industrial and domestic sectors, yet they receive relatively little attention in the thermal engineering domain. Time-temperature characteristics in EMH are qualitatively different from those in conventional heating techniques due to the additional parameters (viz dielectric properties of the material, size and shape of the product and process frequency). From a unified theory perspective, a multi-purpose model has been developed in order to obtain the heating characteristics for an arbitrary processing situation. Theoretical analyses of various EMH processes in materials of various regular geometries and a range of physical properties have been undertaken. Despite the wide spread usage of microwave energy in the food engineering sector. few understand microwaves and their interactions with foods. Much of the published research is largely focussed from the view point of an electrical engineer and aimed at the oven designer. However, trial-and-error methods are usually employed when developing microwavable food products and when using microwave ovens. The presented thesis is focussed from the view-point of the thermal engineer and aimed primarily at food developers and end users. The multi-purpose model was then modified specifically for simulating the heating of food materials in a microwave oven. The validity of the commonly made assumptions was investigated; in particular the variation of dielectriC properties during the heating processes and their likely influence on the model's predictions. Experimental data available in the literature were compiled and analysed to form a set of equations for predicting the dielectric properties of various food materials. Also available correlations for thermal properties were evaluated for a selected set of experimental data of different food materials. Analyses were undertaken to demonstrate and evaluate the effects of various parameters on the heating characteristics of different food materials commonly heated/cooked in microwave ovens. A qualitative comparison of model predictions and experimental measurements is provided to validate the physical basis of the model. Findings from the model lead to a better understanding of the interactions between foods and microwaves.